Showing papers on "Gelatin published in 2014"

Natural polymers for the microencapsulation of cells

Abstract: The encapsulation of living mammalian cells within a semi-permeable hydrogel matrix is an attractive procedure for many biomedical and biotechnological applications, such as xenotransplantation, maintenance of stem cell phenotype and bioprinting of three-dimensional scaffolds for tissue engineering and regenerative medicine. In this review, we focus on naturally derived polymers that can form hydrogels under mild conditions and that are thus capable of entrapping cells within controlled volumes. Our emphasis will be on polysaccharides and proteins, including agarose, alginate, carrageenan, chitosan, gellan gum, hyaluronic acid, collagen, elastin, gelatin, fibrin and silk fibroin. We also discuss the technologies commonly employed to encapsulate cells in these hydrogels, with particular attention on microencapsulation.

Fabrication of alginate–gelatin crosslinked hydrogel microcapsules and evaluation of the microstructure and physico-chemical properties

Abstract: Microencapsulation of cells by using biodegradable hydrogels offers numerous attractive features for a variety of biomedical applications including tissue engineering. This study highlights the fabrication of microcapsules from an alginate–gelatin crosslinked hydrogel (ADA–GEL) and presents the evaluation of the physico-chemical properties of the new microcapsules which are relevant for designing suitable microcapsules for tissue engineering. Alginate di-aldehyde (ADA) was synthesized by periodate oxidation of alginate which facilitates crosslinking with gelatin through Schiff's base formation between the free amino groups of gelatin and the available aldehyde groups of ADA. Formation of Schiff's base in ADA–GEL and aldehyde groups in ADA was confirmed by FTIR and NMR spectroscopy, respectively. Thermal degradation behavior of films and microcapsules fabricated from alginate, ADA and ADA–GEL was dependent on the hydrogel composition. The gelation time of ADA–GEL was found to decrease with increasing gelatin content. The swelling ratio of ADA–GEL microcapsules of all compositions was significantly decreased, whereas the degradability was found to increase with the increase of gelatin ratio. The surface morphology of the ADA–GEL microcapsules was totally different from that of alginate and ADA microcapsules, observed by SEM. Two different buffer solutions (with and without calcium salt) have an influence on the stability of microcapsules which had a significant effect on the gelatin release profile of ADA–GEL microcapsules in these two buffer solutions.

Gelatin-Based Materials in Ocular Tissue Engineering.

Abstract: Gelatin has been used for many years in pharmaceutical formulation, cell culture and tissue engineering on account of its excellent biocompatibility, ease of processing and availability at low cost. Over the last decade gelatin has been extensively evaluated for numerous ocular applications serving as cell-sheet carriers, bio-adhesives and bio-artificial grafts. These different applications naturally have diverse physical, chemical and biological requirements and this has prompted research into the modification of gelatin and its derivatives. The crosslinking of gelatin alone or in combination with natural or synthetic biopolymers has produced a variety of scaffolds that could be suitable for ocular applications. This review focuses on methods to crosslink gelatin-based materials and how the resulting materials have been applied in ocular tissue engineering. Critical discussion of recent innovations in tissue engineering and regenerative medicine will highlight future opportunities for gelatin-based materials in ophthalmology.

Gelatin Particle-Stabilized High Internal Phase Emulsions as Nutraceutical Containers

Abstract: In this paper, we report for the first time the use of a well-dispersed gelatin particle as a representative of natural and biocompatible materials to be an effective particle stabilizer for high internal phase emulsion (HIPE) formulation. Fairly monodispersed gelatin particles (∼200 nm) were synthesized through a two-step desolvation method and characterized by dynamic light scattering, ζ-potential measurements, scanning electron microscopy, and atomic force microscopy. Those protein latexes were then used as sole emulsifiers to fabricate stable oil-in-water Pickering HIPEs at different concentrations, pH conditions, and homogenization times. Most of the gelatin particles were irreversibly adsorbed at the oil-water interface to hinder droplet coalescence, such that Pickering HIPEs can be formed by a small amount of gelatin particles (as low as 0.5 wt % in the water phase) at pH far away from the isoelectric point of the gelatin particles. In addition, increasing homogenization time led to narrow size distribution of droplets, and high particle concentration resulted in more solidlike Pickering HIPEs. In vitro controlled-release experiments revealed that the release of the encapsulated β-carotene can be tuned by manipulating the concentration of gelatin particles in the formulation, suggesting that the stable and narrow-size-distributed gelatin-stabilized HIPEs had potential in functional food and pharmaceutical applications.

Electrospun gelatin/PCL and collagen/PLCL scaffolds for vascular tissue engineering

Abstract: Electrospun hybrid nanofibers prepared using combinations of natural and synthetic polymers have been widely investigated in cardiovascular tissue engineering. In this study, electrospun gelatin/polycaprolactone (PCL) and collagen/poly(l-lactic acid-co-e-caprolactone) (PLCL) scaffolds were successfully produced. Scanning electron micrographs showed that fibers of both membranes were smooth and homogeneous. Water contact angle measurements further demonstrated that both scaffolds were hydrophilic. To determine cell attachment and migration on the scaffolds, both hybrid scaffolds were seeded with human umbilical arterial smooth muscle cells. Scanning electron micrographs and MTT assays showed that the cells grew and proliferated well on both hybrid scaffolds. Gross observation of the transplanted scaffolds revealed that the engineered collagen/PLCL scaffolds were smoother and brighter than the gelatin/PCL scaffolds. Hematoxylin and eosin staining showed that the engineered blood vessels constructed by collagen/PLCL electrospun membranes formed relatively homogenous vessel-like tissues. Interestingly, Young’s modulus for the engineered collagen/PLCL scaffolds was greater than for the gelatin/PCL scaffolds. Together, these results indicate that nanofibrous collagen/PLCL membranes with favorable mechanical and biological properties may be a desirable scaffold for vascular tissue engineering.

Evaluation of fibroblasts adhesion and proliferation on alginate-gelatin crosslinked hydrogel

Abstract: Due to the relatively poor cell-material interaction of alginate hydrogel, alginate-gelatin crosslinked (ADA-GEL) hydrogel was synthesized through covalent crosslinking of alginate di-aldehyde (ADA) with gelatin that supported cell attachment, spreading and proliferation. This study highlights the evaluation of the physico-chemical properties of synthesized ADA-GEL hydrogels of different compositions compared to alginate in the form of films. Moreover, in vitro cell-material interaction on ADA-GEL hydrogels of different compositions compared to alginate was investigated by using normal human dermal fibroblasts. Viability, attachment, spreading and proliferation of fibroblasts were significantly increased on ADA-GEL hydrogels compared to alginate. Moreover, in vitro cytocompatibility of ADA-GEL hydrogels was found to be increased with increasing gelatin content. These findings indicate that ADA-GEL hydrogel is a promising material for the biomedical applications in tissue-engineering and regeneration.

Gelatin hydrogels formed by orthogonal thiol-norbornene photochemistry for cell encapsulation.

Abstract: Covalently cross-linked gelatin hydrogels have received considerable attention in biomedical fields due to the inherent bioactivity of gelatin and the stability of covalent bonds linking the gelatin chains. Derivatives of gelatin, such as gelatin-methacrylamide (GelMA), can be cross-linked into covalent hydrogels through radical-mediated chain-growth photopolymerization. However, accumulating evidence suggests that chain-growth polymerized hydrogels may not be ideal for the encapsulation of cells and proteins prone to radical-mediated damage. The formation of heterogeneous kinetic chains following chain-growth polymerization of (meth)acrylates or (meth)acrylamides may also hinder molecular transport or alter cell–cell/cell–material interactions. This study presents a new synthesis route for preparing norbornene-functionalized gelatin (GelNB) that could be used to form orthogonally cross-linked gelatin-based hydrogels via a thiol–ene photo-click reaction. GelNB was synthesized through reacting gelatin with carbic anhydride in aqueous buffered solution, and the degree of norbornene substitution was controlled by adjusting the reaction time and the solution pH value. GelNB hydrogels were prepared by step-growth thiol–ene photopolymerization using multifunctional thiols as gel cross-linkers and the degree of GelNB hydrogel cross-linking was tuned by adjusting the thiol concentration, GelNB content, or cross-linker functionality. The cytocompatibility of orthogonally cross-linked GelNB hydrogels were demonstrated by in situ photo-encapsulation of human mesenchymal stem cells (hMSCs). When compared with the chain-growth GelMA hydrogels, the orthogonally cross-linked GelNB hydrogel promoted a faster and higher degree of cell spreading.

Potency of Fish Collagen as a Scaffold for Regenerative Medicine

Abstract: Cells, growth factors, and scaffold are the crucial factors for tissue engineering. Recently, scaffolds consisting of natural polymers, such as collagen and gelatin, bioabsorbable synthetic polymers, such as polylactic acid and polyglycolic acid, and inorganic materials, such as hydroxyapatite, as well as composite materials have been rapidly developed. In particular, collagen is the most promising material for tissue engineering due to its biocompatibility and biodegradability. Collagen contains specific cell adhesion domains, including the arginine-glycine-aspartic acid (RGD) motif. After the integrin receptor on the cell surface binds to the RGD motif on the collagen molecule, cell adhesion is actively induced. This interaction contributes to the promotion of cell growth and differentiation and the regulation of various cell functions. However, it is difficult to use a pure collagen scaffold as a tissue engineering material due to its low mechanical strength. In order to make up for this disadvantage, collagen scaffolds are often modified using a cross-linker, such as gamma irradiation and carbodiimide. Taking into account the possibility of zoonosis, a variety of recent reports have been documented using fish collagen scaffolds. We herein review the potency of fish collagen scaffolds as well as associated problems to be addressed for use in regenerative medicine.

Human gelatin tissue-adhesive hydrogels prepared by enzyme-mediated biosynthesis of DOPA and Fe3+ ion crosslinking

Abstract: Gelatin is extensively used as a biomaterial for diverse pharmaceutical and medical applications due to its excellent biocompatibility and biodegradability. Here we present bio-inspired tissue-adhesive gelatin hydrogels prepared by the enzyme-mediated synthesis of l-3,4-dihydroxyphenylalanine (l-DOPA) and Fe3+ ion crosslinking. Gelatin of human origin was obtained through two major steps, extracellular matrix (ECM) extraction from human adipose tissue and gelatin isolation from the ECM. The tyrosine residues in human gelatin were converted into DOPA by enzymatic reaction with tyrosinase. Upon the addition of Fe3+ ions, the DOPA-modified gelatin formed a sticky hydrogel within seconds through complexation between the DOPA molecules and Fe3+ ions. The final DOPA-modified, Fe3+ ion-crosslinked gelatin hydrogels retained their hydrogel stability well at body temperature in an aqueous environment and exhibited appropriate mechanical properties. The hemostatic ability of the DOPA-Fe3+ gelatin hydrogels was explored using a hemorrhaging liver rat model. Shortly after the injection of the DOPA-Fe3+ gelatin hydrogel, the bleeding was arrested in the hemorrhaging site of the liver. Overall results suggest that the DOPA-Fe3+ gelatin hydrogel, with its good elastic and hemostatic properties, is a promising tissue adhesive for use in a wide variety of surgical operations.