Showing papers in "Journal of Biomedical Materials Research Part A in 2012"
TL;DR: The data suggest that the AgNPs-induced cytotoxic effects against tissue cells are particle size-dependent, and thus, the particle size needs careful consideration in the design of the nanoparticles for biomedical uses.
Abstract: Silver nanoparticles (AgNPs) have found a variety of uses including biomedical materials; however, studies of the cytotoxicity of AgNPs by size effects are only in the beginning stage. In this study, we examined the size-dependent cellular toxicity of AgNPs using three different characteristic sizes (∼ 10, 50, and 100 nm) against several cell lines including MC3T3-E1 and PC12. The cytotoxic effect determined based on the cell viability, intracellular reactive oxygen species generation, lactate dehydrogenase release, ultrastructural changes in cell morphology, and upregulation of stress-related genes (ho-1 and MMP-3) was fairly size- and dose-dependent. In particular, AgNPs stimulated apoptosis in the MC3T3-E1 cells, but induced necrotic cell death in the PC12 cells. Furthermore, the smallest sized AgNPs (10 nm size) had a greater ability to induce apoptosis in the MC3T3-E1 cells than the other sized AgNPs (50 and 100 nm). These data suggest that the AgNPs-induced cytotoxic effects against tissue cells are particle size-dependent, and thus, the particle size needs careful consideration in the design of the nanoparticles for biomedical uses. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A:, 2012.
378 citations
TL;DR: Hydrogels with lower stiffness led to reduced macrophage activation and a less severe and more typical FBR, and therefore are more suited for in vivo tissue engineering applications.
Abstract: Poly(ethylene glycol) (PEG) hydrogels, modified with RGD, are promising platforms for cell encapsulation and tissue engineering While these hydrogels offer tunable mechanical properties, the extent of the host response may limit their in vivo applicability The overall objective was to characterize the effects of hydrogel stiffness on the in vitro macrophage response and in vivo host response We hypothesized that stiffer substrates induce better attachment, adhesion, and increased cell spreading, which elevates the macrophage classically activated phenotype and leads to a more severe foreign body reaction (FBR) PEG-RGD hydrogels were fabricated with compressive moduli of 130, 240, and 840 kPa, and the same RGD concentration Hydrogel stiffness did not impact macrophage attachment, but elicited differences in cell morphology Cells retained a round morphology on 130 kPa substrates, with localized and dense F-actin and localized α(V) integrin stainings Contrarily, cells on stiffer substrates were more spread, with filopodia protruding from the cell, a more defined F-actin, and greater α(V) integrin staining When stimulated with lipopolysaccharide, macrophages had a classical activation phenotype, with increased expression of TNF-α, IL-1β, and IL-6, however the degree of activation was significantly reduced with the softest hydrogels A FBR ensued in response to all hydrogels when implanted subcutaneously in mice, but 28 days postimplantation the layer of macrophages at the implant surface was significantly lower in the softest hydrogels In conclusion, hydrogels with lower stiffness led to reduced macrophage activation and a less severe and more typical FBR, and therefore are more suited for in vivo tissue engineering applications
373 citations
TL;DR: The PF127/GN nanohybrid is found to be capable of effectively encapsulating doxorubicin (DOX) with ultrahigh drug-loading efficiency (DLE; 289%, w/w) and exhibits a pH responsive drug release behavior.
Abstract: Herein, a novel Pluronic F127/graphene nanosheet (PF127/GN) hybrid was prepared via an one-pot process including the simultaneous reduction of graphene oxide and assembly of PF127 and GN. The nanohybrid exhibits high water dispersibility and stability in physiological environment with the hydrophilic chains of PF127 extending to the solution while the hydrophobic segments anchoring at the surface of graphene via hydrophobic interaction. The PF127/GN nanohybrid is found to be capable of effectively encapsulating doxorubicin (DOX) with ultrahigh drug-loading efficiency (DLE; 289%, w/w) and exhibits a pH responsive drug release behavior. The superb DLE of the PF127/GN nanohybrid relies on the introduction of GN which is structurally compatible with DOX. Cellular toxicity assays performed on human breast cancer MCF-7 cells demonstrate that the PF127/GN nanohybrid displays no obvious cytotoxicity, whereas the PF127/GN-loaded DOX (PF127/GN/DOX) shows remarkable cytotoxicity to the MCF-7. Cell internalization study reveals that PF127/GN nanohybrid facilitates the transfer of DOX into MCF-7 cells, evidenced by the image of confocal laser scanning microscopy. The above results indicate the potential application of this novel nanocarrier in biomedicine.
178 citations
TL;DR: The latest improvements being made to the existing implant materials are dealt with and new materials being introduced in the field of biomaterials are included.
Abstract: Great deal of research is still going on in the field of orthopedic and craniofacial implant development to resolve various issues being faced by the industry today. Despite several disadvantages of the metallic implants, they continue to be used, primarily because of their superior mechanical properties. In order to minimize the harmful effects of the metallic implants and its by-products, several modifications are being made to these materials, for instance nickel-free stainless steel, cobalt-chromium and titanium alloys are being introduced to eliminate the toxic effects of nickel being released from the alloys, introduce metallic implants with lower modulus, reduce the cost of these alloys by replacing rare elements with less expensive elements etc. New alloys like tantalum, niobium, zirconium, and magnesium are receiving attention given their satisfying mechanical and biological properties. Non-oxide ceramics like silicon nitride and silicon carbide are being currently developed as a promising implant material possessing a combination of properties such as good wear and corrosion resistance, increased ductility, good fracture and creep resistance, and relatively high hardness in comparison to alumina. Polymer/magnesium composites are being developed to improve mechanical properties as well as retain polymer's property of degradation. Recent advances in orthobiologics are proving interesting as well. This paper thus deals with the latest improvements being made to the existing implant materials and includes new materials being introduced in the field of biomaterials.
175 citations
TL;DR: Observations suggest that the novel Chi-HAp-MSCol composite scaffolds are promising biomaterials for matrix-based bone repair and bone augmentation.
Abstract: Tricomponent scaffold systems prepared by natural materials especially of marine origin are gaining much attention nowadays for the application in bone tissue engineering. A novel scaffold (Chi-HAp-MSCol) containing chitosan (Chi), hydroxyapatite (HAp) derived from Thunnus obesus bone and marine sponge (Ircinia fusca) collagen (MSCol) was prepared using freeze-drying and lyophilization method. This biomimetic scaffold, along with the Chi and Chi-HAp scaffolds were characterized biophysicochemically for their comparative significance in bone grafting applications. The structural composition of the chitosan, Chi-Hap, and Chi-HAp-MSCol scaffolds were characterized by Fourier Transform Infrared spectroscopy. The porosity, water uptake, and retention abilities of the composite scaffolds decreased, whereas Thermogravimetric and Differential Thermal Analyses results revealed the increase in thermal stability in the scaffold because of the highly stable HAp and MSCol. Homogeneous dispersion of HAp and MSCol in chitosan matrix with interconnected porosity of 60-180 μm (Chi-HAp) and 50-170 μm (Chi-HAp-MSCol) was observed by Scanning Electron Microscopy, X-ray diffraction, and optical microscopy. Cell proliferation in composite scaffolds was relatively higher than pure chitosan when observed by MTT assay and Hoechst staining in vitro using MG-63 cell line. These observations suggest that the novel Chi-HAp-MSCol composite scaffolds are promising biomaterials for matrix-based bone repair and bone augmentation.
123 citations
TL;DR: Antimicrobial activity testing against Gram-positive bacterium, Staphylococcus aureus, demonstrated that this AMP-loaded nanotubular surface could effectively kill the bacteria and reduce the total bacterial number adhered to the surface after 4 h of culture.
Abstract: Peri-implant infections have been reported as one of the major complications that lead to the failure of orthopedic implants. An ideal solution to the peri-implant infection is to locally deliver antimicrobial agents through the implant surface. The rising problem of infections caused by multiple antibiotic-resistant bacteria makes traditional antibiotics less desirable for the prevention of peri-implant infections. One of the promising alternatives is the family of antimicrobial peptides (AMPs). In this study, we report the local delivery of AMPs through the nanotubular structure processed on titanium surface. Self-organized and vertically oriented TiO2 nanotubes, about 80 nm in diameter and 7 μm thick, were prepared by the anodization technique. HHC-36 (KRWWKWWRR), one of the most potent broad-spectrum AMPs, was loaded onto the TiO2 nanotubes via a simple vacuum-assisted physical adsorption method. Antimicrobial activity testing against Gram-positive bacterium, Staphylococcus aureus, demonstrated that this AMP-loaded nanotubular surface could effectively kill the bacteria (≈ 99.9% killing) and reduce the total bacterial number adhered to the surface after 4 h of culture. In vitro AMP elution from the nanotubes was investigated using liquid chromatography-mass spectrometry (LC-MS). The release profiles strongly depended on the crystallinity of the TiO2 nanotubes. Anatase TiO2 nanotubes released significantly higher amounts of AMP than amorphous nanotubes during the initial burst release stage. Both followed almost the same slow release profile from 4 h up to 7 days. Despite the differences in release kinetics, no significant difference was observed between these two groups in bactericidal efficiency.
123 citations
TL;DR: Dynamical mechanical analysis has evidenced that composite scaffolds at low frequencies showed an increase of storage and loss modulus with increasing frequency; furthermore, a drop of E' and E″ at 1 Hz was observed, and for higher frequencies both moduli increased again.
Abstract: The aim of this work was the preparation and characterization of scaffolds with mechanical and functional properties able to regenerate bone. Porous scaffolds made of chitosan/gelatin (POL) blends containing different amounts of a bioactive glass (CEL2), as inorganic material stimulating biomineralization, were fabricated by freeze-drying. Foams with different compositions (CEL2/POL 0/100; 40/60; 70/30 wt %/wt) were prepared. Samples were crosslinked using genipin (GP) to improve mechanical strength and thermal stability. The scaffolds were characterized in terms of their stability in water, chemical structure, morphology, bioactivity, and mechanical behavior. Moreover, MG63 osteoblast-like cells and periosteal-derived stem cells were used to assess their biocompatibility. CEL2/POL samples showed interconnected pores having an average diameter ranging from 179 ± 5 μm for CEL2/POL 0/100 to 136 ± 5 μm for CEL2/POL 70/30. GP-crosslinking and the increase of CEL2 amount stabilized the composites to water solution (shown by swelling tests). In addition, the SBF soaking experiment showed a good bioactivity of the scaffold with 30 and 70 wt % CEL2. The compressive modulus increased by increasing CEL2 amount up to 2.1 ± 0.1 MPa for CEL2/POL 70/30. Dynamical mechanical analysis has evidenced that composite scaffolds at low frequencies showed an increase of storage and loss modulus with increasing frequency; furthermore, a drop of E' and E″ at 1 Hz was observed, and for higher frequencies both moduli increased again. Cells displayed a good ability to interact with the different tested scaffolds which did not modify cell metabolic activity at the analyzed points. MTT test proved only a slight difference between the two cytotypes analyzed.
116 citations
TL;DR: A way to intrinsically optimize MFH by tailoring the MNPs to any applied AMF, a required precursor to optimize dose and time of treatment is presented.
Abstract: Magnetic Fluid Hyperthermia (MFH) is a promising approach towards adjuvant cancer therapy that is based on the localized heating of tumors using the relaxation losses of iron oxide magnetic nanoparticles (MNPs) in alternating magnetic fields (AMF). In this study, we demonstrate optimization of MFH by tailoring MNP size to an applied AMF frequency. Unlike conventional aqueous synthesis routes, we use organic synthesis routes that offer precise control over MNP size (diameter ∼10 to 25 nm), size distribution, and phase purity. Furthermore, the particles are successfully transferred to the aqueous phase using a biocompatible amphiphilic polymer, and demonstrate long-term shelf life. A rigorous characterization protocol ensures that the water-stable MNPs meet all the critical requirements: (1) uniform shape and monodispersity, (2) phase purity, (3) stable magnetic properties approaching that of the bulk, (4) colloidal stability, (5) substantial shelf life, and (6) pose no significant in vitro toxicity. Using a dedicated hyperthermia system, we then identified that 16 nm monodisperse MNPs (σ-0.175) respond optimally to our chosen AMF conditions (f = 373 kHz, H₀ = 14 kA/m); however, with a broader size distribution (σ-0.284) the Specific Loss Power (SLP) decreases by 30%. Finally, we show that these tailored MNPs demonstrate maximum hyperthermia efficiency by reducing viability of Jurkat cells in vitro, suggesting our optimization translates truthfully to cell populations. In summary, we present a way to intrinsically optimize MFH by tailoring the MNPs to any applied AMF, a required precursor to optimize dose and time of treatment.
113 citations
TL;DR: The data indicate that VICs require a much lower substrate stiffness level to "deactivate" them than previously thought, and demonstrates the importance of the mechanical properties of materials used for valve repair or for engineering valve tissue.
Abstract: During heart valve remodeling and in many disease states, valvular interstitial cells (VICs) shift to an activated myofibroblast phenotype characterized by enhanced synthetic and contractile activity Pronounced alpha smooth muscle actin (αSMA)-positive stress fibers, the hallmark of activated myofibroblasts, are also observed in VICs cultured on stiff substrates especially in the presence of transforming growth factor-beta1 (TGF-β1), however, the detailed relationship between stiffness and VIC phenotype has not been explored The goal of this study was to characterize VIC activation as a function of substrate stiffness over a wide range of stiffness levels including that of diseased valves (stiff), normal valves (compliant), and hydrogels for heart valve tissue engineering (very soft) VICs obtained from porcine aortic valves were cultured on stiff tissue culture plastic to activate them, then, cultured on collagen-coated polyacrylamide substrates of predefined stiffness in a high-throughput culture system to assess the persistence of activation Metrics extracted from regression analysis demonstrate that relative to a compliant substrate, stiff substrates result in higher cell numbers, more pronounced expression of αSMA-positive stress fibers, and larger spread area which is in qualitative agreement with previous studies Our data also indicate that VICs require a much lower substrate stiffness level to "deactivate" them than previously thought The high sensitivity of VICs to substrate stiffness demonstrates the importance of the mechanical properties of materials used for valve repair or for engineering valve tissue
107 citations
TL;DR: The 1393B3 glass provided greater bone formation and may be more promising for bone defect repair due to its capacity to be molded into scaffolds.
Abstract: Bioactive glasses are biocompatible materials that convert to hydroxyapatite in vivo, and potentially support bone formation, but have mainly been available in particulate and not scaffold form. In this study, borosilicate and borate bioactive glass scaffolds were evaluated in critical-sized rat calvarial defects. Twelve-week-old rats were implanted with 45S5 silicate glass particles and scaffolds of 1393 silicate, 1393B1 borosilicate, and 1393B3 borate glass. After 12 weeks, the defects were harvested, stained with hematoxylin and eosin to evaluate bone regeneration, Periodic Acid Schiff to quantitate blood vessel area, and von Kossa and backscatter SEM to estimate newly mineralized bone and hydroxyapatite conversion of bioactive glasses. The amount of new bone was 12.4% for 45S5, 8.5% for 1393, 9.7% for 1393B1, and 14.9% for 1393B3 (*p = 0.04; cf. 1393 and 1393B1). Blood vessel area was significantly higher (p = 0.009) with 45S5 (3.8%), with no differences among 1393 (2.0%), 1393B1 (2.4%), or 1393B3 (2.2%). Percent von Kossa-positive area was 18.7% for 45S5, 25.4% for 1393, 29.5% for 1393B1, and 30.1% for 1393B3, significantly higher (p = 0.014) in 1393B1 and 1393B3 glasses than in 45S5. 45S5 and 1393B3 converted completely to HA in vivo. The 1393B3 glass provided greater bone formation and may be more promising for bone defect repair due to its capacity to be molded into scaffolds. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A 100A:3267-3275, 2012.
106 citations
TL;DR: CoCrMo-alloy particles were by far the most toxic and decreased viability and proliferation of human osteoblasts, fibroblasts, and macrophages by >50% at a dose of only 50 particles per cell and Zr-based particles induced less toxicity and inflammatory responses.
Abstract: The performance of total joint arthroplasty (TJA) depends on the size/shape, material, and amounts of implant debris. Much remains unknown in terms of which types of debris are most reactive. We compared the responses of human periimplant cells, osteoblasts, fibroblasts, and macrophages, exposed to particles of different metal-based particles (i.e., cobalt-chromium-molybdenum (CoCrMo) alloy, titanium (Ti) alloy, zirconium (Zr) oxide, and Zr alloy. CoCrMo-alloy particles were by far the most toxic (p 50% at a dose of only 50 particles per cell. All particle types induced the production of interleukin (IL)-6, tumor necrosis factor (TNF)-α, and IL-8 by osteoblasts, fibroblasts, and monocytes/macrophages. However, the greatest cytokine responses of macrophages were to CoCrMo alloy (TNF-α and IL-8) and Ti alloy (IL-1β). Likewise, the greatest responses of fibroblasts and osteoblasts were to CoCrMo alloy (IL-6 and TNF-α) (i.e., IL-6 300 pg/mL; 30-fold max, TNF-α 150 pg/mL; 15-fold max) versus controls. For macrophages, CoCrMo particles induced IL-8 (> 2000 pg/mL; approx 100-fold max) above controls and were also significantly elevated above levels produced by Zr-based particles. Submicron sized (0.2-0.9 μm) Zr-based particles (originally presumed to be more reactive) induced less toxicity and inflammatory responses when compared with larger (approx 1 μm) CoCrMo-alloy and Ti-alloy particles.
TL;DR: This review focuses on the complex structure of native articular cartilage, the critical properties of scaffolds required for cartilage regeneration, present strategies for scaffold design, and future directions forcartilage regeneration with functional scaffold materials.
Abstract: The injury and degeneration of articular cartilage and associated arthritis are leading causes of disability worldwide. Cartilage tissue engineering as a treatment modality for cartilage defects has been investigated for over 20 years. Various scaffold materials have been developed for this purpose, but has yet to achieve feasibility and effectiveness for widespread clinical use. Currently, the regeneration of articular cartilage remains a formidable challenge, due to the complex physiology of cartilage tissue and its poor healing capacity. Although intensive research has been focused on the developmental biology and regeneration of cartilage tissue and a diverse plethora of biomaterials have been developed for this purpose, cartilage regeneration is still suboptimal, such as lacking a layered structure, mechanical mismatch with native cartilage and inadequate integration between native tissue and implanted scaffold. The ideal scaffold material should have versatile properties that actively contribute to cartilage regeneration. Functional scaffold materials may overcome the various challenges faced in cartilage tissue engineering by providing essential biological, mechanical, and physical/chemical signaling cues through innovative design. This review thus focuses on the complex structure of native articular cartilage, the critical properties of scaffolds required for cartilage regeneration, present strategies for scaffold design, and future directions for cartilage regeneration with functional scaffold materials.
TL;DR: Results indicate that PLGA-PF127 NPs can form a promising system that not only delivers anti-cancer drugs, but also overcomes drug resistance, which is prevalent in most cancer cells.
Abstract: The objective of this study was to investigate the physical characteristics of poly(D,L-lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) coated with two surfactants, Pluronic or the commonly used polyvinyl alcohol (PVA); and determine their in vitro efficiency as drug carriers for cancer therapy. Free surfactant cytotoxicity results indicated that Pluronic F127 (PF127) was most cytocompatible among the Pluronics tested and hence chosen for coating PLGA NPs for further studies. Release studies using doxorubicin (DOX) as a drug model showed sustained release of DOX from both PVA- and PF127-coated PLGA NPs (PLGA-PVA and PLGA-PF127, respectively) over 28 days. Further, there was no significant difference in human dermal fibroblasts and human aortic smooth muscle cell survival when exposed to both types of NPs. Cellular uptake studies demonstrated that uptake of both nanoparticle types was dose-dependent for both prostate and breast cancer cells. However, these cancer cells internalized more PLGA-PF127 NPs than PLGA-PVA NPs. Moreover, studies showed that drug-loaded PLGA-PF127 NPs not only killed more cancer cells than drug-loaded PLGA-PVA NPs, but also overcame drug resistance in LNCaP, MDA-MB-231, and MDA-MB-468 cancer cells on re-exposure. These results indicate that PLGA-PF127 NPs can form a promising system that not only delivers anti-cancer drugs, but also overcomes drug resistance, which is prevalent in most cancer cells.
TL;DR: Results demonstrate that aligned 400 nm TSF-scaffold is more suitable for the development of hESC-derived NPs, which shed light on optimization of the therapeutic potential of h ESCs to be employed for neural regeneration.
Abstract: Although transplantation of human embryonic stem cells (hESCs)-derived neural precursors (NPs) has been demonstrated with some success for nervous repair in small animal model, control of the survival, and directional differentiation of these cells is still challenging. Meanwhile, the notion that using suitable scaffolding materials to control the growth and differentiation of grafted hESC-derived NPs raises the hope for better clinical nervous repair. In this study, we cultured hESC-derived NPs on Tussah silk fibroin (TSF)-scaffold of different diameter (i.e., 400 and 800 nm) and orientation (i.e., random and aligned) to analyze the effect of fiber diameter and alignment on the cell viability, neuronal differentiation, and neurite outgrowth of hESC-derived NPs. The results show that TSF-scaffold supports the survival, migration, and differentiation of hESC-derived NPs. Aligned TSF-scaffold significantly promotes the neuronal differentiation and neurite outgrowth of hESC-derived neurons compared with random TSF-scaffold. Moreover, on aligned 400 nm fibers cell viability, neuronal differentiation and neurite outgrowth are greater than that on aligned 800 nm fibers. Together, these results demonstrate that aligned 400 nm TSF-scaffold is more suitable for the development of hESC-derived NPs, which shed light on optimization of the therapeutic potential of hESCs to be employed for neural regeneration. © 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2012.
TL;DR: Newly-developed silica-coated magnetite nanoparticles, with a high capacity for magnetization, water-dispersibility, and diminished cell toxicity, may be potentially useful in diverse biomedical applications, including delivery of therapeutic and diagnostic biomolecules.
Abstract: Magnetic nanoparticles (MNPs) are considered highly useful in therapeutic and diagnostic applications However, MNPs require surface modification to promote dispersibility in aqueous solutions and thus biocompatibility In this article, the authors modified MNPs with inorganic silica layer to create silica-coated magnetite nanoparticles (MNP@Si) via sol–gel process Synthesis involves hydrolysis and condensation steps using tetraethylorthosilicate (TEOS) in methanol/ polyethylene glycol (PEG) solution and ammonia catalyst Nanoparticles were characterized in terms of morphology, particle size, crystalline phase, chemical-bond structure, surface charge and magnetic properties: in particular, the MNP@Si size was easily tunable through alteration of the Fe3O4-to-TEOS ratio As this ratio increased, the MNP@Si size decreased from 270 to 15 nm whilst maintaining core 12-nm MNP particle size, indicating decrease in thickness of the silica coating All MNP@Si, in direct contrast to uncoated MNPs, showed excellent stability in aqueous solution The particles' physicochemical and magnetic properties systematically varied with size (coating thickness), and the zeta potential diminished toward negative values, while magnetization increased as the coating thickness decreased 15-nm MNP@Si showed excellent magnetization (about 641 emu/g), almost comparable to that of uncoated MNPs (708 emu/g) Preliminary in vitro assays confirmed that the silica layer significantly reduced cellular toxicity as assessed by increase in cell viability and reduction in reactive oxygen species production during 48 h of culture Newly-developed MNP@Si, with a high capacity for magnetization, water-dispersibility, and diminished cell toxicity, may be potentially useful in diverse biomedical applications, including delivery of therapeutic and diagnostic biomolecules © 2012 Wiley Periodicals, Inc J Biomed Mater Res Part A, 2012
TL;DR: It is indicated that adhesion site density but not stiffness influences the redifferentiation process of chondrocytes in 3D, and this knowledge might be used to optimize the red differentiatediation process and thus the formation of cartilage-like tissue.
Abstract: To obtain sufficient cell numbers for cartilage tissue engineering with autologous chondrocytes, cells are typically expanded in monolayer culture. As a result, they lose their chondrogenic phenotype in a process called dedifferentiation, which can be reversed upon transfer into a 3D environment. We hypothesize that the properties of this 3D environment, namely adhesion site density and substrate elasticity, would influence this redifferentiation process. To test this hypothesis, chondrocytes were expanded in monolayer and their phenotypical transition was monitored. Agarose hydrogels manipulated to give different RGD adhesion site densities and mechanical properties were produced, cells were incorporated into the gels to induce redifferentiation, and constructs were analyzed to determine cell number and extracellular matrix production after 2 weeks of 3D culture. The availability of adhesion sites within the gels inhibited cellular redifferentiation. Glycosaminoglycan production per cell was diminished by RGD in a dose-dependent manner and cells incorporated into gels with the highest RGD density, remained positive for collagen type I and produced the least collagen type II. Substrate stiffness, in contrast, did not influence cellular redifferentiation, but softer gels contained higher cell numbers and ECM amounts after 2 weeks of culture. Our results indicate that adhesion site density but not stiffness influences the redifferentiation process of chondrocytes in 3D. This knowledge might be used to optimize the redifferentiation process of chondrocytes and thus the formation of cartilage-like tissue.
TL;DR: Results show that Cu(II) enhances cell activity and proliferation of osteoblastic cells on CPC and furthermore affects the expression of several bone specific proteins such as bone sialo protein or osteocalcin and may offer a promising alternative to protein based modification to stimulate cellular activity for an improved bone healing.
Abstract: Bone substitute materials such as calcium phosphate cements (CPC) are frequently used as growth factor carriers for the stimulation of osteoblast-formation around an implant. However, biological modification based on delicate protein factors like extracellular matrix proteins or growth factors is subject to a number of shortcomings like the need for storage below room temperature and cost of production. The aim of this study was to investigate ionic modification as an alternative bioinorganic route for implant modification. Although it is known that Cu(II) plays a role in angiogenesis and bone formation, not all involved processes are well understood yet. In this study the in vitro effect of Cu(II) on growth and activity of osteoblastic cells seeded on brushite (CaHPO(4) · 2 H(2) O) scaffolds as well as on glass discs was investigated. The results show that Cu(II) enhances cell activity and proliferation of osteoblastic cells on CPC and furthermore affects the expression of several bone specific proteins such as bone sialo protein or osteocalcin. Therefore, the modification of CPC with Cu(II) may offer a promising alternative to protein based modification to stimulate cellular activity for an improved bone healing.
TL;DR: Laminin and laminin-polycaprolactone (PCL) blend nanofibers were fabricated to mimic peripheral nerve basement membrane to provide a firm foundation for the use of natural-synthetic blend electrospun nanofibia to enhance existing hollow nerve guidance conduits.
Abstract: Peripheral nerve transection occurs commonly in traumatic injury, causing deficits distal to the injury site. Conduits for repair currently on the market are hollow tubes; however, they often fail due to slow regeneration over long gaps. To facilitate increased regeneration speed and functional recovery, the ideal conduit should provide biochemically relevant signals and physical guidance cues, thus playing an active role in regeneration. To that end, laminin and laminin–polycaprolactone (PCL) blend nanofibers were fabricated to mimic peripheral nerve basement membrane. In vitro assays established 10% (wt) laminin content is sufficient to retain neurite-promoting effects of laminin. In addition, modified collector plate design to introduce an insulating gap enabled the fabrication of aligned nanofibers. The effects of laminin content and fiber orientation were evaluated in rat tibial nerve defect model. The lumens of conduits were filled with nanofiber meshes of varying laminin content and alignment to assess changes in motor and sensory recovery. Retrograde nerve conduction speed at 6 weeks was significantly faster in animals receiving aligned nanofiber conduits than in those receiving random nanofiber conduits. Animals receiving nanofiber-filled conduits showed some conduction in both anterograde and retrograde directions, whereas in animals receiving hollow conduits, no impulse conduction was detected. Aligned PCL nanofibers significantly improved motor function; aligned laminin blend nanofibers yielded the best sensory function recovery. In both cases, nanofiber-filled conduits resulted in better functional recovery than hollow conduits. These studies provide a firm foundation for the use of natural–synthetic blend electrospun nanofibers to enhance existing hollow nerve guidance conduits.
TL;DR: From a morphologic standpoint, improved interaction between connective tissue was observed at 1 week, likely leading to more uniform and higher bone formation at 3 weeks for the Ti-Plasma treated implants was observed.
Abstract: This study investigated the effect of an Argon-based atmospheric pressure plasma (APP) surface treatment operated chairside at atmospheric pressure conditions applied immediately prior to dental implant placement in a canine model. Surfaces investigated comprised: rough titanium surface (Ti) and rough titanium surface + Argon-based APP (Ti-Plasma). Surface energy was characterized by the Owens-Wendt-Rabel-Kaelble method and chemistry by X-ray photoelectron spectroscopy (XPS). Six adult beagles dogs received two plateau-root form implants (n = 1 each surface) in each radii, providing implants that remained 1 and 3 weeks in vivo. Histometric parameters assessed were bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO). Statistical analysis was performed by Kruskall-Wallis (95% level of significance) and Dunn's post-hoc test. The XPS analysis showed peaks of Ti, C, and O for the Ti and Ti- Plasma surfaces. Both surfaces presented carbon primarily as hydrocarbon (CC, CH) with lower levels of oxidized carbon forms. The Ti-Plasma presented large increase in the Ti (+11%) and O (+16%) elements for the Ti- Plasma group along with a decrease of 23% in surface-adsorbed C content. At 1 week no difference was found in histometric parameters between groups. At 3 weeks significantly higher BIC (>300%) and mean BAFO (>30%) were observed for Ti-Plasma treated surfaces. From a morphologic standpoint, improved interaction between connective tissue was observed at 1 week, likely leading to more uniform and higher bone formation at 3 weeks for the Ti-Plasma treated implants was observed. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A 2012.
TL;DR: The two decellularization methods were demonstrated to be effective for preparation of cultured cell-derived ECM scaffolds and had similar gross appearances and microstructures.
Abstract: Extracellular matrix (ECM) scaffolds derived from cultured cells have drawn increasing attention for use in tissue engineering. We have developed a method to prepare cultured cell-derived ECM scaffolds by combining three-dimensional cell culture, decellularization, and selective template removal. Cell-ECM-template complexes were first formed by culture of cells in a poly(lactic-co-glycolic acid) (PLGA) mesh template to deposit their own ECM. The complexes were subsequently decellularized to remove cellular components. Finally, the PLGA template was selectively removed to obtain the ECM scaffolds. Seven decellularization methods were compared for their decellularization effects during scaffold preparation. They were: freeze-thaw cycling (-80°C, six times) with ammonia water (25 mM); 0.1% Triton™ X-100 (TX100) with 1.5M KCl aqueous solution; freeze-thaw cycling alone; ammonia water alone; TX100 extraction; osmotic shock with 1.5M KCl; and freeze-thaw cycling with 3M NaCl. Among these methods, the methods of freeze-thaw cycling with NH(4) OH and TX100 with 1.5M KCl showed the best effect on the removal of cellular components from the complexes, while the other five methods could only partially remove cellular components. The ECM scaffolds prepared by these two methods had similar gross appearances and microstructures. In vivo implantation of the ECM scaffolds prepared by these two methods induced mild host responses. The two decellularization methods were demonstrated to be effective for preparation of cultured cell-derived ECM scaffolds.
TL;DR: Findings indicated that fish collagen scaffolds derived from fresh water origin were highly biocompatible in nature.
Abstract: Collagen, a major component of native extracellular matrix, has diverse biomedical applications. However, its application is limited due to lack of cost-effective production and risk of disease transmission from bovine sources currently utilized. This study describes fabrication and characterization of nano/micro fibrous scaffolds utilizing collagen extracted from fresh water fish origin. This is the first time collagen extracted from fresh water fish origin was studied for their biocompatibility and immunogenicity. The nano/micro fibrous collagen scaffolds were fabricated through self-assembly owing to its amphiphilic nature and were subsequently cross-linked. In vitro degradation study revealed higher stability of the cross-linked scaffolds with only ∼50% reduction of mass in 30 days, while the uncross-linked one degraded completely in 4 days. Further, minimal inflammatory response was observed when collagen solution was injected in mice with or without adjuvant, without significant dilution of sera. The fish collagen scaffolds exhibited considerable cell viability and were comparable with that of bovine collagen. SEM and fluorescence microscopic analysis revealed significant proliferation rate of cells on the scaffolds and within 5 days the cells were fully confluent. These findings indicated that fish collagen scaffolds derived from fresh water origin were highly biocompatible in nature. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A:, 2012.
TL;DR: Significant mechanical and structural differences in the aortic valve tissues of 6- to 9-month-old porcine models and 1-year-old ovine models with respect to those of aged humans, suggest that these animal models may not be representative of the typical patient undergoing aortsic valve replacement.
Abstract: Aortic valve disease develops in an escalating fashion in elderly patients. Current treatments including total valve replacement and valve repair techniques are still suboptimal. A thorough understanding of the animal and human valve tissue properties, particularly their differences, is crucial for the establishment of preclinical animal models and strategies for evaluating new valve treatment techniques, such as transcatheter valve intervention and tissue engineered valves. The goal of this study was to characterize and compare the biomechanical properties and histological structure of healthy ovine, porcine, and human aortic valve leaflets. The biaxial mechanical properties of the aortic valve leaflets of 10 ovine (∼1 year), 10 porcine (6-9 months), and 10 aged human (80.6 ± 8.34) hearts were quantified. Tissue microstructure was analyzed via histological techniques. Aged human aortic valve leaflets were significantly less compliant than both ovine and porcine leaflets, with the ovine leaflets being the most compliant. Histological analysis revealed structural differences between the species: the human and porcine leaflets contained more collagen and elastin than the ovine leaflets. Significant mechanical and structural differences in the aortic valve tissues of 6- to 9-month-old porcine models and 1-year-old ovine models with respect to those of aged humans, suggest that these animal models may not be representative of the typical patient undergoing aortic valve replacement.
TL;DR: It is suggested that coating polymers (particularly, polycarbonate) with nanostructured selenium is a fast and effective way to reduce bacteria functions that lead to medical device infections.
Abstract: Biofilms are a common cause of persistent infections on medical devices as they are easy to form and hard to treat The objective of this study was for the first time to coat selenium (a natural element in the body) nanoparticles on the surface of polycarbonate medical devices (such as those used for medical catheters) and to examine their effectiveness at preventing biofilm formation The size and distribution of selenium coatings were characterized using scanning electron microscopy and atomic force microscopy The strength of the selenium coating on polycarbonate was assessed by tape-adhesion tests followed by atomic absorption spectroscopy Results showed that selenium nanoparticles had a diameter of 50–100 nm and were well distributed on the polycarbonate surface In addition, more than 50% of the selenium coating survived the tape-adhesion test as larger nanoparticles had less adhesion strength to the underlying polycarbonate substrate than smaller selenium nanoparticles Most significantly, the results of this in vitro study showed that the selenium coatings on polycarbonate significantly inhibited Staphylococcus aureus growth to 89% and 27% when compared with an uncoated polycarbonate surface after 24 and 72 h, respectively Importantly, this was accomplished without using antibiotics but rather with an element (selenium) that is natural to the human body Thus, this study suggests that coating polymers (particularly, polycarbonate) with nanostructured selenium is a fast and effective way to reduce bacteria functions that lead to medical device infections © 2012 Wiley Periodicals, Inc J Biomed Mater Res Part A: 100A: 3205–3210, 2012
TL;DR: The results clearly demonstrated the feasibility of incorporating NT-3 and ChABC via mTG immobilization to produce protein-incorporated collagen nanofibers for SCI treatment.
Abstract: Nerve regeneration after spinal cord injuries (SCI) remains suboptimal despite recent advances in the field. One major hurdle is the rapid clearance of drugs from the injury site, which greatly limits therapeutic outcomes. Nanofiber scaffolds represent a potential class of materials for enhancing nerve regeneration because of its biomimicking architecture. In this study, we investigated the feasibility of incorporating neurotrophin-3 (NT-3) and chondroitinase ABC (ChABC) onto electrospun collagen nanofibers for SCI treatment. By using microbial transglutaminase (mTG) mediated crosslinking, proteins were loaded onto electrospun collagen nanofibers at an efficiency of ∼45-48%. By combining NT-3 with heparin during the protein incorporation process, a sustained release of NT-3 was obtained (∼96% by day 28). As indicated by dorsal root ganglion outgrowth assay, NT-3 incorporated collagen scaffolds supported neuronal culture and neurite outgrowth for a longer time period than bolus delivery of NT-3. The presence of heparin also protected ChABC from degradation. Specifically, as evaluated by dimethylmethylene blue assay, bioactive ChABC was detected from collagen scaffolds for at least 32 days in vitro in the presence of heparin (∼32% of bioactivity retained). In contrast, ChABC bioactivity was only ∼1.9% by day 22 in the absence of heparin. Taken together, these results clearly demonstrated the feasibility of incorporating NT-3 and ChABC via mTG immobilization to produce protein-incorporated collagen nanofibers. Such biofunctional nanofiber constructs may find useful applications in SCI treatment by providing topographical signals and multiple biochemical cues that can promote nerve regeneration while antagonizing axonal growth inhibition for CNS regeneration.
TL;DR: A novel biodegradable Mg-4.0Zn-1.0Ca-0.6Zr (wt %) alloy provided evidence of acceptable cytocompatibility for medical applications and was successfully produced using a series of metallurgical processes; including melting, casting, rolling, and heat treatment.
Abstract: A novel biodegradable Mg-4.0Zn-1.0Ca-0.6Zr (wt %) alloy was successfully produced using a series of metallurgical processes; including melting, casting, rolling, and heat treatment. The hardness and ultimate tensile strength of the alloy sheets increased to 71.2HV and 320 MPa after rolling and then aging for 12 h at 175°C. These mechanical properties were sufficient for load-bearing orthopedic implants. A hydroxyapatite (HA) coating was deposited on the Mg-4.0Zn-1.0Ca-0.6Zr (wt %) alloy using a novel coating process combining alkali heat pretreatment, electrodeposition, and alkali heat posttreatment. The microstructure, composition, and phases of the Mg-4.0Zn-1.0Ca-0.6Zr (wt %) alloy and HA coating were characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The degradation, hemolysis, and cytocompatibility of the HA-coated and uncoated Mg-4.0Zn-1.0Ca-0.6Zr (wt %) alloy were studied in vitro. The corrosion potential (E(corr)) of Mg-4.0Zn-1.0Ca-0.6Zr alloy (-1.72 V) was higher than Mg (-1.95 V), Mg-0.6Ca alloy (-1.91 V) and Mg-1.0Ca alloy (-1.97 V), indicating the Mg-Zn-Ca-Zr alloy would be more corrosion resistant. The initial corrosion potential of the HA-coated Mg alloy sample (-1.51 V) was higher than the uncoated sample (-1.72 V). The hemolysis rates of the HA-coated and uncoated Mg-4.0Zn-1.0Ca-0.6Zr (wt %) alloy samples were both <5%, which met the requirements for implant materials. The HA-coated and uncoated Mg-4.0Zn-1.0Ca-0.6Zr (wt %) alloy samples demonstrated the same cytotoxicity score as the negative control. The HA-coated samples showed a slightly greater relative growth rate (RGR%) of fibroblasts than the uncoated samples. Both the HA-coated and uncoated Mg-4.0Zn-1.0Ca-0.6Zr (wt %) alloy provided evidence of acceptable cytocompatibility for medical applications.
TL;DR: Collagen hydrogel has inherent inductivity for the chondrogenic differentiation of BMSCs, and the optimum specification and tissue formation were accompanied with local high cell density, which may greatly contribute to clinical cartilage regeneration.
Abstract: It is controversial whether a biomaterial itself, rather than addition of any exogenous growth factor, could induce mesenchymal stem cells (MSCs) to differentiate into chondrogenic lineage, further to regenerate cartilage. Previous studies have shown that collagen-based hydrogel could induce MSCs to differentiate into chondrocytes in vivo but the in vitro studies only have a few reports. The evidence that biomaterials could induce chondrogenesis is not adequate. In this study, we tried to address whether type I collagen hydrogel has chondro-inductive capability in vitro and how this scaffold induces MSCs to generate cartilage tissue without exogenous growth factors in the culture medium. We encapsulated neonatal rabbit bone marrow mesenchymal stem cells (BMSCs) in type I collagen hydrogel homogeneously or implanted cell aggregates in hydrogel, and cultured them in nonchondrogenic inductive media. After at least 28 days culture, cells in the homogeneous group were tending to chondrogenic differentiation while cell density was high, and cells in the aggregate group have almost gone through chondrogenesis and formed neo-cartilage tissue with abundant specific extracellular matrix (ECM) deposition. These results indicate collagen hydrogel has inherent inductivity for the chondrogenic differentiation of BMSCs, and the optimum specification and tissue formation were accompanied with local high cell density. This research suggests a feasible strategy to induce the chondro differentiation of BMSCs independent of exogenous growth factors, which may greatly contribute to clinical cartilage regeneration.
TL;DR: The results demonstrated that the copolymers could be potentially used in chemotherapeutic applications and showed efficiency in the control of the growth of HeLa cells when compared with the pac litaxel dissolved in solution or paclitaxel encapsulated in Pluronics F127.
Abstract: A multiblock poly(ether ester urethane)s comprising poly(e-caprolactone), poly(ethylene glycol), and poly(propylene glycol) segments was synthesized. The aqueous copolymer solution exhibited thermogelling behavior at a critical gelation concentration of 3 wt %. The chemical structure and molecular characteristic of the copolymers were studied by gel permeation chromatography, NMR, and fourier transform infrared spectroscopy (FTIR). Rheological characterizations on the thermogel were carried out. Drug release studies using paclitaxel showed that sustained drug release of more than 2 weeks can be achieved with this system. The paclitaxel-loaded gels showed efficiency in the control of the growth of HeLa cells when compared with the paclitaxel dissolved in solution or paclitaxel encapsulated in Pluronics F127. The results demonstrated that the copolymers could be potentially used in chemotherapeutic applications. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A 100A:2686–2694, 2012.
TL;DR: It is demonstrated that 3D MNF scaffold provides a structural support for hESC-MSCs growth and guides bone formation suggesting that this novel strategy successfully makes use of electrospun fibers for bone tissue engineering, which may help realize the clinical translation of Electrospun nanofibers for regenerative medicine in future.
Abstract: This study aimed to develop a practical three-dimensional (3D) macroporous scaffold from aligned electrospun nanofibrous yarns for bone tissue engineering. A novel 3D unwoven macroporous nanofibrous (MNF) scaffold was manufactured with electrospun poly(L-lactic acid) and polycaprolactone (w/w 9:1) nanofibers through sequential yarns manufacture and honeycombing process at 65°C. The efficacy of 3D MNF scaffold for bone formation were evaluated using human embryonic stem cell-derived mesenchymal stem cells (hESC-MSCs) differentiation model and rabbit tibia bone defect model. In vitro, more cell proliferation and cell ingrowth were observed in 3D MNF scaffold. Moreover, calcium deposit was obviously detected in vitro differentiation of hESC-MSCs. In vivo, histology and X-ray showed that 3D MNF scaffold treated bone defect had fine 3D bony tissue formation around the scaffold as well as inside the scaffold at 3 weeks and 6 weeks. This study demonstrated that 3D MNF scaffold provides a structural support for hESC-MSCs growth and guides bone formation suggesting that this novel strategy successfully makes use of electrospun fibers for bone tissue engineering, which may help realize the clinical translation of electrospun nanofibers for regenerative medicine in future.
TL;DR: The decellularized tendon slices (DTSs) are sheet scaffolds with a combination of elemental mechanical strength and tendon ECM bioactive factors that may have many potential applications in tendon tissue engineering.
Abstract: To develop a naturally derived tendon tissue engineering scaffold with the preservation of the native ultrastructure, tensile strength, and biochemical composition of the tendon extracellular matrix (ECM), decellularized tendon slices (DTSs) were prepared using repetitive freeze/thaw of the intact Achilles tendons, frozen section, and nuclease treatment. The DTSs were characterized in the native ultrastructure, mechanical properties, biochemical composition, and cytocompatibility. Histological examination and DNA quantification analysis confirmed that cells were completely removed from tendon tissue by repetitive freeze/thaw in combination with nuclease treatment 12 h. The intrinsic ultrastructure of tendon tissue was well preserved based on scanning electron microscopy examination. The tensile strength of the DTSs was retained 85.62% of native tendon slice. More than 93% of proteoglycans (fibromodulin, biglycan) and growth factors (TGF-β1, IGF-1, VEGF, and CTGF) inherent in tendon ECM were preserved in the DTSs according to ELISA analysis. Furthermore, the DTSs facilitated attachment and repopulation of NIH-3T3 fibroblasts in vitro. Overall, the DTSs are sheet scaffolds with a combination of elemental mechanical strength and tendon ECM bioactive factors that may have many potential applications in tendon tissue engineering.
TL;DR: It was observed that an inner morphological hydrogel structure influences their swelling and degradation behavior, which is additionally reduced by in-gel-embedded α-tocopherol because of hydrophobic interactions with their constituents, and hindering the effect on collagenase activity.
Abstract: The crosslinking of chitosan (CHT) and gelatin (GEL) accomplished with N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) was investigated and optimized in relation to hydrogels stability by varying the CHT/GEL mass ratio and the EDC/NHS molar ratio at different and constant EDC concentrations. Hydrogels were also fabricated in the presence of α-tocopherol to assess the release mechanism of a lipophilic drug from a highly-hydrophilic CHT/GEL hydrogel network. Alterations in the physico-chemical properties of hydrogels were characterized by differential scanning calorimetry (DSC) and fourier transform infrared spectroscopy (FTIR), and their biostability was studied within a simulated body-fluid solution (PBS of pH 7.4) at 37°C for 24 h by evaluating the degree of swelling, followed by topography and morphology characterization using scanning electron microscopy (SEM). The analysis confirmed the formation of a modulated hydrogels porosity using different freezing temperatures prior to lyophilization. The in vitro degradation behaviors of the hydrogels were investigated for up to 5 weeks using collagenase, lysozyme, and N-acetyl-β-D-glucosaminidase by monitoring the weight-losses of hydrogels and their degradation products, being identified by UV-Vis spectroscopy and high-performance liquid chromatography (HPLC) as well as the pH monitoring of degraded solutions. It was observed that an inner morphological hydrogel structure influences their swelling and degradation behavior, which is additionally reduced by in-gel-embedded α-tocopherol because of hydrophobic interactions with their constituents, and hindering the effect on collagenase activity. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2012.