Showing papers in "Journal of Materials Chemistry B in 2016"

Heteroatom-doped carbon dots: synthesis, characterization, properties, photoluminescence mechanism and biological applications.

Abstract: Heteroatom-doped carbon dots (CDs), due to their excellent photoluminescence (PL) properties, attracted widespread attention recently and demonstrated immense promise for diverse applications, particularly for biological applications. The objective of this feature article is to provide a comprehensive overview of the recent progress in the research and development of heteroatom-doped CDs and a detailed description of the influence of single or co-doping heteroatoms on their PL behavior. The most recent understanding and critical insights into the PL mechanism of heteroatom-doped CDs are also highlighted. Moreover, potential bio-related applications of heteroatom-doped CDs in biosensing, bioimaging, and theranostics are also reviewed. This state-of-the-art review will provide a platform for understanding the intricate details of heteroatom-doped CDs, a summary of the latest progress in the field, and related applications in biology and is expected to inspire further developments in this exciting class of materials.

Advances in non-enzymatic glucose sensors based on metal oxides.

Abstract: Glucose sensors have been extensively developed because of their broad applications, especially in diabetes diagnosis. Up to date, electrochemical enzymatic glucose sensors are commonly used in daily life for glucose detection and commercially successful as glucose-meters because they exhibit excellent selectivity, high reliability, and could be handled under physiological pH conditions. However, considering some intrinsic disadvantages of enzymes, such as high fabrication cost and poor stability, non-enzymatic glucose sensors have attracted increasing research interest in recent years due to their low cost, high stability, prompt response, and low detection limit. Furthermore, the development of nanotechnology has also offered new opportunities to construct nanostructured electrodes for glucose sensing applications. With distinguished advantages, metal oxides have garnered extensive effort in the development of cost-effective sensors with high stability, sensitivity and quick response for the determination of glucose via electrochemical oxidation. Hence, this review summarizes the advances in non-enzymatic glucose sensors based on different metal oxides (such as ZnO, CuO/Cu2O, NiO, Co3O4, MnO2, etc.) and their nanocomposites. Additionally, a brief prospective is presented on metal oxides for glucose sensors.

Carbon dots: surface engineering and applications

Abstract: Carbon dots have attracted a great deal of attention because of their high performance, cheap and facile preparation, and potential applications in a wide area. In order to broaden their applications, especially to meet specific requirements, surface engineering, including tailoring surface functional group coating and subsequent chemical modification as required, is an effective strategy for further functionalization of carbon dots. In this article, representative approaches to coating the surface with various functional groups, and strategies for conjugating specific materials onto the surface of carbon dots for functional modification via covalent bonds, electrostatic interactions and hydrogen bonds are highlighted, as well as the results from explorations of their various applications in target modulated sensing, accurate drug delivery and bioimaging at high resolution.

Antibacterial activity of graphene-based materials

Abstract: Complications related to infectious diseases have significantly decreased due to the availability and use of a wide variety of antibiotics and antimicrobial agents. However, excessive use of antibiotics and antimicrobial agents over years has increased the number of drug resistant pathogens. Microbial multidrug resistance poses serious risks and consequently research attention has refocused on finding alternatives for antimicrobial treatment. Among the various approaches, the use of engineered nanostructures is currently the most promising strategy to overcome microbial drug resistance by improving the remedial efficiency due to their high surface-to-volume ratio and their intrinsic or chemically incorporated antibacterial activity. Graphene, a two-dimensional ultra-thin nanomaterial, possesses excellent biocompatibility, putting it in the forefront for different applications in biosensing, drug delivery, biomedical device development, diagnostics and therapeutics. Graphene-based nanostructures also hold great promise for combating microbial infections. Yet, several questions remain unanswered such as the mechanism of action with the microbial entities, the importance of size and chemical composition in the inhibition of bacterial proliferation and adhesion, cytotoxicity, and other issues when considering future clinical implementation. This review summarizes the current efforts in the formulation of graphene-based nanocomposites with antimicrobial and antibiofilm activities as new tools to tackle the current challenges in fighting against bacterial targets. Furthermore, the review describes the features of graphene–bacterial interactions, with the hope to shed light on the range of possible mode of actions, serving the goal to develop a better understanding of the antibacterial capabilities of graphene-based nanostructures.

Carbon dots as a trackable drug delivery carrier for localized cancer therapy in vivo

Abstract: Fluorescent carbon dots (CDs) with a size smaller than 10 nm, excellent biocompatibility, and low to no cytotoxicity are considered as a rising star in nanomedicine. In this report, for the first time we demonstrate that green-emitting CDs with a carboxyl-rich surface can be employed as a trackable drug delivery agent for localized cancer treatment in a mouse model. The CDs are conjugated with the cancer drug, Doxorubicin (DOX), via non-covalent bonding, utilizing the native carboxyl groups on CDs and the amine moiety on DOX molecules. The pH difference between cancer and normal cells was successfully exploited as the triggering mechanism for DOX release. Our in vivo study demonstrated that the fluorescent CDs can serve as a targeted drug delivery system for localized therapy, and the stimuli-responsive non-covalent bonding between the nanodot carrier and the drug molecule is sufficiently stable in complex biological systems. Taken together, our work provides a strategy to promote the potential clinical application of CDs in cancer theranostics.

Functionalized halloysite nanotube by chitosan grafting for drug delivery of curcumin to achieve enhanced anticancer efficacy

Abstract: Halloysite nanotubes (HNTs) have a unique tubular structure in nanoscale, and have shown potential as novel carriers for various drugs. Coating the nanotubes with a hydrophilic polymer shell can significantly decrease the toxicity and provide colloidal stability during blood circulation. Here, we synthesized chitosan grafted HNTs (HNTs-g-CS) and investigated their potential as a nano-formulation for the anticancer drug curcumin. The structure and properties of HNTs-g-CS were characterized using water contact angle, zeta-potential, Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and transmission electron microscopy (TEM) techniques. HNTs-g-CS exhibit a maximum 90.8% entrapment efficiency and 3.4% loading capacity of curcumin, which are higher than those of raw HNTs. HNTs-g-CS also show no obvious hemolytic phenomenon and good stability in serum. The cumulative release ratio of curcumin from HNTs-g-CS/curcumin at cell lysate after 48 hours is 84.2%. The curcumin loaded HNTs-g-CS show specific toxicity to various cancer cell lines, including HepG2, MCF-7, SV-HUC-1, EJ, Caski and HeLa, and demonstrate an inhibition concentration of IC50 at 5.3–192 μM as assessed by cytotoxicity studies. The anticancer activity of this nanoformulation is extremely high in EJ cells compared with the other cancer cell lines. The cell uptake of HNTs-g-CS is confirmed by fluorescence microscopy. Flow cytometric analysis of curcumin loaded HNTs-g-CS shows that curcumin loaded HNTs-g-CS increase apoptosis on EJ cells. The content of ROS created by HNTs-g-CS/curcumin is more than that of free curcumin. All these results suggest that HNTs-g-CS are potential nanovehicles for anticancer drug delivery in cancer therapy.

Stimuli-responsive polymersomes and nanoreactors

Abstract: Macromolecular self-assembly is attracting increasing scientific interest in polymer science. One of the most studied assemblies are stimuli-responsive polymersomes that can convert specific environmental changes to functional outputs based on a physicochemical adjustment of their chain structures and membrane properties. These unique features have made it possible to design and construct smart self-assembled architectures for various emerging applications such as polymeric nanocapsules for tunable delivery vehicles. Moreover, stimuli-responsive polymersomes possess the ability to encapsulate active enzymatic species which makes them well suited as nanoreactors capable of performing enzymatic reactions. In this regard, this class of smart polymersomes provides an avenue to apply synthetic polymer systems as biomimetic materials. Here, in this review, we will highlight recent progress with regard to stimuli-responsive polymer vesicles/nanocapsules and their development towards intelligent nanocarriers and nanoreactors or artificial organelles.

Graphene scaffolds in progressive nanotechnology/stem cell-based tissue engineering of the nervous system

Abstract: Although graphene/stem cell-based tissue engineering has recently emerged and has promisingly and progressively been utilized for developing one of the most effective regenerative nanomedicines, it suffers from low differentiation efficiency, low hybridization after transplantation and lack of appropriate scaffolds required in implantations without any degrading in functionality of the cells. In fact, recent studies have demonstrated that the unique properties of graphene can successfully resolve all of these challenges. Among various stem cells, neural stem cells (NSCs) and their neural differentiation on graphene have attracted a lot of interest, because graphene-based neuronal tissue engineering can promisingly realize the regenerative therapy of various incurable neurological diseases/disorders and the fabrication of neuronal networks. Hence, in this review, we further focused on the potential bioapplications of graphene-based nanomaterials for the proliferation and differentiation of NSCs. Then, various stimulation techniques (including electrical, pulsed laser, flash photo, near infrared (NIR), chemical and morphological stimuli) which have recently been implemented in graphene-based stem cell differentiations were reviewed. The possibility of degradation of graphene scaffolds (NIR-assisted photodegradation of three-dimensional graphene nanomesh scaffolds) was also discussed based on the latest achievements. The biocompatibility of graphene scaffolds and their probable toxicities (especially after the disintegration of graphene scaffolds and distribution of its platelets in the body), which is still an important challenge, were reviewed and discussed. Finally, the initial recent efforts for fabrication of neuronal networks on graphene materials were presented. Since there has been no in vivo application of graphene in neuronal regenerative medicine, we hope that this review can excite further and concentrated investigations on in vivo (and even in vitro) neural proliferation, stimulation and differentiation of stem cells on biocompatible graphene scaffolds having the potential of degradability for the generation of implantable neuronal networks.

Electrospinning of natural polymers for advanced wound care: towards responsive and adaptive dressings

Abstract: In the last few years, the health-care services have registered worldwide an increased number of patients suffering from chronic wounds and ulcers, which are mainly associated with diabetes, obesity and cancer. The need for regenerating rapidly and effectively the injured skin has stimulated the research of advanced therapies for wound care. This review will discuss how biomimetic architectures produced by electrospinning natural biopolymers fulfil most of the requirements of ideal wound dressings. It will also examine the recent progress in the area of portable electrospinning systems and of multiscale instructive materials that integrate stimuli responsive and sensing elements.

Nanoengineered biomimetic hydrogels for guiding human stem cell osteogenesis in three dimensional microenvironments

Abstract: The ability to modulate stem cell differentiation in a three dimensional (3D) microenvironment for bone tissue engineering in the absence of exogenous pharmaceutical agents such as bone morphogenic protein (BMP-2) remains a challenge. In this study, we introduce extracellular matrix (ECM)-mimicking nanocomposite hydrogels to induce the osteogenic differentiation of human mesenchymal stem cells (hMSCs) for bone regeneration in the absence of any osteoinductive factors. In particular, we have reinforced a photocrosslinkable collagen-based matrix (gelatin methacryloyl, GelMA) using disk-shaped nanosilicates (nSi), a new class of two-dimensional (2D) nanomaterials. We show that nanoengineered hydrogels supported the migration and proliferation of encapsulated hMSCs, with no signs of cell apoptosis or inflammatory cytokine responses. The addition of nSi significantly enhances the osteogenic differentiation of encapsulated hMSCs as evident from the increase in alkaline phosphates (ALP) activity and the deposition of a biomineralized matrix compared to GelMA. We also show that microfabricated nanoengineered microgels can be used to pattern and control cellular behaviour. Furthermore, we demonstrate that nanoengineered hydrogel have high biocompatibility as determined by in vivo experiments using an immunocompetent rat model. Specifically, the hydrogels showed minimum localized immune responses, indicating their ability for tissue engineering applications. Overall, we showed the ability of nanoengineered hydrogels loaded with 2D nanosilicates for the osteogenic differentiation of stem cells in vitro, in the absence of any growth factors such as BMP-2. Our in vivo studies show high biocompatibility of nanocomposites and show the potential for growth factor free bone regeneration.

Alginate–lavender nanofibers with antibacterial and anti-inflammatory activity to effectively promote burn healing

Abstract: One of the current challenges in wound care is the development of multifunctional dressings that can both protect the wound from external agents and promote the regeneration of the new tissue. Here, we show the combined use of two naturally derived compounds, sodium alginate and lavender essential oil, for the production of bioactive nanofibrous dressings by electrospinning, and their efficacy for the treatment of skin burns induced by midrange ultraviolet radiation (UVB). We demonstrate that the engineered dressings reduce the risk of microbial infection of the burn, since they stop the growth of Staphylococcus aureus. Furthermore, they are able to control and reduce the inflammatory response that is induced in human foreskin fibroblasts by lipopolysaccharides, and in rodents by UVB exposure. In particular, we report a remarkable reduction of pro-inflammatory cytokines when fibroblasts or animals are treated with the alginate-based nanofibers. The down-regulation of cytokines production and the absence of erythema on the skin of the treated animals confirm that the here described dressings are promising as advanced biomedical devices for burn management.

Fe doped CeO2 nanorods for enhanced peroxidase-like activity and their application towards glucose detection

Abstract: The construction of highly efficient inorganic mimetic enzymes (nanozymes) is much needed to replace natural enzymes due to their instability and high cost. Recently, nanoscale CeO2 has been attracting significant interest due to its unique properties such as facile redox behaviour (Ce4+ ↔ Ce3+) and surface defects. In the present work, various amounts of Fe3+-doped CeO2 nanorods (NRs) (with 3, 6, 9, and 12% Fe doping) were synthesized using a facile hydrothermal method and investigated for peroxidase-like activity and glucose detection. The peroxidase-like activity results revealed that 6 at% doping is the optimal Fe doping level to demonstrate superior catalytic performance over un-doped and Fe3+-doped CeO2 NRs. Steady state kinetic analysis also confirms that the 6% Fe3+-doped CeO2 (6Fe/CeO2) NRs exhibited excellent catalytic performance towards 3,3′,5,5′tetramethylbenzidine (TMB) oxidation with a Km and Vm of 0.176 mM and 8.6 × 10−8 M s−1, respectively, as compared to horseradish peroxidase (HRP) enzymes (0.434 mM and 10.0 × 10−8 M s−1). Typical colour reactions arising from the catalytic oxidation of the TMB substrate over 6Fe/CeO2 NRs with H2O2 have been utilized to establish a simple sensitive and selective colorimetric assay for the determination of glucose concentration in buffer, diluted fruit juices and foetal bovine serum samples. The superior catalytic performance of 6Fe/CeO2 NRs could be attributed to abundant surface defects, high surface area and pore volume, and preferential exposure of the highly reactive (110) planes.

A self-healing, re-moldable and biocompatible crosslinked polysiloxane elastomer

Abstract: The thermally healable polysiloxane elastomers were successfully prepared by cross-linking polydimethylsiloxane bearing maleimide pendants with furan-end functionalized siloxane via the Diels–Alder (DA) reaction. The elastomers with good mechanical properties show excellent self-healing and remoldability functions due to the thermally reversible feature of the DA reaction. The molecular mechanism of self-healing was confirmed by in situ structural characterization. Moreover, the biocompatibility of the polysiloxane elastomer containing DA bonds is found to be fairly good by cytotoxicity evaluation and animal subcutaneous experiments, suggesting its potential applications in the biomedical field as artificial skin and scaffolds for tissue engineering.

Green preparation of nitrogen-doped carbon dots derived from silkworm chrysalis for cell imaging

Abstract: Carbon dots (CDs) with a high quantum yield have been synthesized by a facile and green one-pot approach under microwaves with silkworm chrysalis (SC) as the natural carbon source, without using any other chemicals/reagents. The morphology and optical properties of the resultant CDs are characterized by TEM, XRD, FT-IR, XPS, UV-vis and photoluminescence (PL). The SC-CDs have an average size of 19 nm, and contain C, O and N with relative contents of ca. 71.32%, 22.96% and 5.72%, respectively. A significant emission at 420 nm at an excitation wavelength of 350 nm is recorded, resulting in a quantum yield of 46% with quinine sulfate (quantum yield 54%) as a reference. In addition to excellent solubility and stability in aqueous medium, the SC-CDs exhibit excitation-dependent photoluminescence with a large Stokes shift of 70 nm. It is further demonstrated that the SC-CDs exhibit a low cytotoxicity at a higher concentration of 15 mg mL−1 and they are able to display bright blue, green and red colors under an inverted fluorescence microscope during cell imaging experiments, showing their vast potential in bioimaging.

Oxygen Delivering Biomaterials for Tissue Engineering.

Abstract: Tissue engineering (TE) has provided promising strategies for regenerating tissue defects, but few TE approaches have been translated for clinical applications. One major barrier in TE is providing adequate oxygen supply to implanted tissue scaffolds, since oxygen diffusion from surrounding vasculature in vivo is limited to the periphery of the scaffolds. Moreover, oxygen is also an important signaling molecule for controlling stem cell differentiation within TE scaffolds. Various technologies have been developed to increase oxygen delivery in vivo and enhance the effectiveness of TE strategies. Such technologies include hyperbaric oxygen therapy, perfluorocarbon- and hemoglobin-based oxygen carriers, and oxygen-generating, peroxide-based materials. Here, we provide an overview of the underlying mechanisms and how these technologies have been utilized for in vivo TE applications. Emerging technologies and future prospects for oxygen delivery in TE are also discussed to evaluate the progress of this field towards clinical translation.

Collagen: a network for regenerative medicine

Abstract: The basic building block of the extra-cellular matrix in native tissue is collagen. As a structural protein, collagen has an inherent biocompatibility making it an ideal material for regenerative medicine. Cellular response, mediated by integrins, is dictated by the structure and chemistry of the collagen fibers. Fiber formation, via fibrillogenesis, can be controlled in vitro by several factors: pH, ionic strength, and collagen structure. After formation, fibers are stabilized via cross-linking. The final bioactivity of collagen scaffolds is a result of both processes. By considering each step of fabrication, scaffolds can be tailored for the specific needs of each tissue, improving their therapeutic potential.

Graphene and graphene-based nanocomposites: biomedical applications and biosafety

Abstract: Graphene is the first carbon-based two dimensional atomic crystal and has gained much attention since its discovery by Geim and co-workers in 2004. Graphene possesses a large number of material parameters such as superior mechanical stiffness, strength and elasticity, very high electrical and thermal conductivity, among many others. It is the strongest and the most stretchable known material, which has the record thermal conductivity and very high intrinsic mobility, as well as being completely impermeable. Numerous favorable properties of graphene make it a potential promising material for applications in biomedicine. A large surface area, chemical purity and the possibility for its easy functionalization allow graphene to provide opportunities for drug delivery. Its unique mechanical properties suggest applications in tissue engineering and regenerative medicine. However, like other nanomaterials, graphene may pose a bio-hazard. In this article, we present a systematic review on the synthesis of graphene, various approaches for the fabrication of nanocomposites of graphene and their applications in biomedicine. A very detailed review is presented on how graphene and its nanocomposites are currently exploited for drug delivery, cancer therapy, gene delivery, biosensing and regenerative medicine. Finally, the safety and toxicity associated with graphene are also discussed.

Azaacenes as active elements for sensing and bio applications

Abstract: Since azaacenes have electron-deficient backbones and lone-pair electrons on nitrogen centers, they can efficiently detect the target molecules or ions through supramolecular interactions such as anion–π attractions and coordinate bonding. These special features make azaacenes very designable for various sensors, which can be further used in the bio field. In this review, we will summarize the recent progress in the applications of azaacenes in sensing and bio fields. We believe that a rapid development in the research of sensors and bio applications based on azaacenes will be witnessed in the coming years due to their tuneable structures, optical properties and binding abilities.

Drug delivery and controlled release from biocompatible metal–organic frameworks using mechanical amorphization

Abstract: We have used a family of Zr-based metal–organic frameworks (MOFs) with different functionalized (bromo, nitro and amino) and extended linkers for drug delivery. We loaded the materials with the fluorescent model molecule calcein and the anticancer drug α-cyano-4-hydroxycinnamic acid (α-CHC), and consequently performed a mechanical amorphization process to attempt to control the delivery of guest molecules. Our analysis revealed that the loading values of both molecules were higher for the MOFs containing unfunctionalized linkers. Confocal microscopy showed that all the materials were able to penetrate into cells, and the therapeutic effect of α-CHC on HeLa cells was enhanced when loaded (20 wt%) into the MOF with the longest linker. On one hand, calcein release required up to 3 days from the crystalline form for all the materials. On the other hand, the amorphous counterparts containing the bromo and nitro functional groups released only a fraction of the total loaded amount, and in the case of the amino-MOF a slow and progressive release was successfully achieved for 15 days. In the case of the materials loaded with α-CHC, no difference was observed between the crystalline and amorphous form of the materials. These results highlight the necessity of a balance between the pore size of the materials and the size of the guest molecules to accomplish a successful and efficient sustained release using this mechanical ball-milling process. Additionally, the endocytic pathway used by cells to internalize these MOFs may lead to diverse final cellular locations and consequently, different therapeutic effects. Understanding these cellular mechanisms will drive the design of more effective MOFs for drug delivery applications.

Electrospun polyurethane/keratin/AgNP biocomposite mats for biocompatible and antibacterial wound dressings

Abstract: Keratin based biomaterials have emerged as potential candidates for various biomedical and biotechnological applications due to their intrinsic biocompatibility, biodegradability, mechanical durability, and natural abundance. The objective of this study is to combine the merits of polyurethane, keratin, and silver nanoparticles (AgNPs) together and develop a novel nanofibrous mat for wound dressing. Herein, keratin was first extracted from human hair and chemically modified with iodoacetic acid to afford S-(carboxymethyl) keratin. The modified keratin was examined using Raman spectroscopy, infrared spectroscopy, and SDS-PAGE. The keratin was then blended with polyurethane (PU) and electrospun. Subsequently, AgNPs were formed in situ to afford antibacterial PU/keratin/AgNP mats. These mats were characterized using field emission scanning electron microscopy (FE-SEM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), water contact angle measurements, and X-ray photoelectron spectroscopy (XPS). MTT results indicated that the introduction of keratin could accelerate fibroblast cell proliferation, while the loaded AgNPs did not weaken cytocompatibility. Antibacterial test results showed that PU/keratin/AgNP mats exerted good antibacterial property. The results from a wound healing test and a histological examination suggested that these biocomposite mats could remarkably accelerate wound recovery as compared to the conventional gauze sponge dressing. Given their excellent biocompatibility, antibacterial properties, and very mild inflammatory responses, PU/keratin/AgNP mats have great potential for wound dressing applications.

Ca2+, pH and thermo triple-responsive mechanized Zr-based MOFs for on-command drug release in bone diseases

Abstract: We report a new approach towards the design of multi-stimuli responsive “gated scaffolds” based on the combination of capped metal–organic frameworks (MOFs) and supramolecular[2]pseudorotaxanes. These mechanized Zr-MOFs showed negligible premature release, high drug encapsulation, low cytotoxicity and good biocompatibility. Around or inside the bone tumour cells, the pH, lysosomal pH, and osteoclast pH are observed to be lowered (acidosis), and thus the resulting osteolysis increases the Ca2+ concentration (hypercalcemia). The drug release from the mechanized MOFs was triggered by the simultaneous variations of pH and Ca2+ concentration in bone tumour cells. Hyperthermia (also called thermal therapy or thermotherapy) as a popular type of cancer treatment technique can also control drug release in the above-mentioned system. This design opens up the possibility of developing smart biomaterials for bone regeneration and cancer therapy.

Molecular simulation of pH-dependent diffusion, loading, and release of doxorubicin in graphene and graphene oxide drug delivery systems

Abstract: In this study, the adsorption of doxorubicin (DOX), an anticancer drug, on pristine graphene (PG) and graphene oxide (GO) nanocarriers with different surface oxygen densities and in an aqueous environment with varying pH levels was investigated using molecular dynamics (MD) simulation. The drug loading and release on the GO nanocarrier was also simulated using pH as the controller mechanism. Overall, the DOX/nanocarrier interactions become stronger as the graphene surface oxygen density increases. Although pH has a negligible effect on the single-molecule drug adsorption on the GO surfaces under acidic and neutral conditions, significantly stronger DOX/nanocarrier interactions occur for the GO nanosheet with a lower surface oxygen density (GO-16, with an O/C ratio of 1 : 6) at basic pH levels. Moreover, the DOX/nanocarrier interactions are greatly weakened in the GO nanosheet with higher surface oxygen density (GO-13, with an O/C ratio of 1 : 3) under basic conditions. These observations are partly attributed to a more favorable geometry of the DOX molecule on the GO-16 surface as opposed to a loosely attached DOX molecule on the edges of the GO-13 nanosheet. When comparing the adsorption kinetics and transport properties of the DOX molecule in different GO systems, the drug diffusion coefficient increases with decreasing pH value (going from basic to neutral to acidic) due to the reduced total water–nanocarrier interactions. The latter observation is an indication of the more facilitated transport of the DOX molecule in an aqueous medium towards the nanocarrier surface at lower pH levels. Finally, we have confirmed the loading and release of the DOX molecules on the GO nanocarrier under neutral (pH = 7) and acidic (pH = 5) conditions, respectively. The former signifies the blood pH level, whereas the latter is reminiscent of the pH of a tumorous cell. The computational results presented in this work reveal the underlying mechanisms of DOX loading and release on PG and GO surfaces, which may be used to design better graphene-based nanocarriers for the DOX delivery and targeting applications.

Recent progress in gellan gum hydrogels provided by functionalization strategies

Abstract: Gellan gum, a microbial exopolysaccharide fermentation product of Pseudomonas elodea, is a natural biomaterial that has shown promise for tissue engineering and regenerative medicine applications. Although this exopolysaccharide possesses many advantages, such as interesting physicochemical properties and non-cytotoxicity, the mechanical properties and processability of gellan gum are not totally satisfactory in different tissue engineering contexts, i.e. gellan gum hydrogels are mechanically weak and the high gelling temperature is also unfavourable. An additional critical limitation is the lack of specific attachment sites for anchorage-dependent cells. However, the multiple hydroxyl groups and the free carboxyl per repeating unit of gellan gum can be used for chemical modification and functionalization in order to optimize its physicochemical and biological properties. A number of physical modification approaches have also been employed. This review outlines the recent progress in gellan gum hydrogels and their derivatives, and identifies the new challenges in tissue engineering, provided by blending and/or chemical modification.

Micro/nanostructured surfaces for self-powered and multifunctional electronic skins

Abstract: Flexible electronic devices are regarded as one of the key technologies in wearable healthcare systems, wireless communications and smart personal electronics. For the realization of these applications, wearable energy and sensor devices are the two main technologies that need to be developed into lightweight, miniaturized, and flexible forms. In this review, we introduce recent advances in the controlled design of device structures into bioinspired micro/nanostructures and 2D/3D structures for the enhancement of energy harvesting and multifunctional sensing properties of flexible electronic skins. In addition, we highlight their potential applications in flexible/wearable electronics, sensors, robotics and prosthetics, and biomedical devices.

Gallium-containing mesoporous bioactive glass with potent hemostatic activity and antibacterial efficacy

Abstract: Haemorrhage remains the leading cause of potentially survivable death in both military and civilian populations. Although a large variety of hemostatic agents have been developed, many of them have an inadequate capacity to induce hemostasis and are not effective in killing bacteria. In recent years, mesoporous bioactive glasses (MBGs) were found to be effective in inducing hemostasis. However, the materials may not be considered as ideal hemostats since they do not offer antimicrobial activity. The gallium ion (Ga+3) not only exhibits antibacterial properties but also accelerates the blood coagulation cascade. The aim of this study was to develop MBGs containing various concentrations of Ga2O3 (1, 2 & 3 mol%) via the evaporation-induced self-assembly (EISA) process and investigate whether the addition of Ga3+ would induce both hemostatic and antibacterial effects. The results indicated that the incorporation of lower Ga2O3 content (1 mol%) into the MBG system improved structural properties including the specific surface area, mesopore size and pore volume as well as the release of silicon and calcium ions. The bioactive glass was found to stimulate blood coagulation, platelet adhesion and thrombus generation and exerted an antibacterial effect against both Escherichia coli and Staphylococcus aureus. Likewise, Ga-doped MBGs showed excellent cytocompatibility even after 3 days, with the 1% Ga2O3-containing MBG attaining the best biocompatibility that render them safe hemostatic agents for stopping bleeding. This study demonstrated that the lowest Ga2O3-substituted MBG can be a potent candidate for controlling haemorrhage and wound infection.

Self-propelled liquid metal motors steered by a magnetic or electrical field for drug delivery

Abstract: Self-propelled motors have inspired enormous potential in accomplishing various tasks when navigating in an aqueous environment due to their virtues of requiring no external energy source and autonomous locomotion. However, without reliable controllability, their potential value would be heavily reduced. Here, we demonstrate an innovative millimeter-scale self-propelled motor steered by an external magnetic or electric field, which successfully enables the motor to avoid out-of-control motion behavior encountered previously. A nickel cap is electroplated on a liquid metal droplet. The on-board fuel aluminum foil not only triggers the autonomous movement, but also enhances the adhesion between the nickel cap and the droplet. The current motor, composed of a nickel cap, aluminum and liquid metal, is capable of running with a velocity of 3 cm s−1 for hours without the use of an external energy source. In addition, the integration of the nickel cap renders a magnetic field exploitable to easily alter the performance of the motor remotely. Furthermore, an external electrical field offers a feasible way to accelerate the motor directionally in a reliable manner. More importantly, as a conceptual experiment, when loaded with soft alginate-based biomaterial containing aluminium nanoparticles as drugs, such a motor is still able to be self-propelled, exhibiting steerable motion for drug delivery. The remarkable features of the liquid metal motor, such as softness, controllable self-propelled movement and drug-delivery application, represent a critical step toward functional intelligent soft robots or machines.

Controlling the surface chemistry of cerium oxide nanoparticles for biological applications

Abstract: The catalytic activity of cerium oxide nanoparticles (CNPs) depends on the surface Ce3+/Ce4+ oxidation state. CNPs with a higher Ce3+ to Ce4+ ratio, oxygen vacancies and higher superoxide dismutase (SOD) mimetic activity are more effective against diseases associated with oxidative stress or inflammation. CNPs with a lower Ce3+/Ce4+ ratio show higher catalase mimetic activity and possess anticancer/antibacterial activity. However, different synthesis methods of CNPs and capping agents/surface coatings result in various Ce3+/Ce4+ oxidation states, thus limiting the use of particular CNPs for specific biological applications. In this study, we have shown that by selecting an appropriate doping method we can control the surface Ce3+/Ce4+ oxidation state to tune the catalytic activity and biological response. Importantly, superior SOD mimetic activity and efficient reactive oxygen species scavenging capability of one-step synthesized CNPs are linked to a uniform distribution of dopants in the CNP lattice and changes in the surface Ce3+/Ce4+ oxidation state.

Selective sensing of isoprene by Ti-doped ZnO for breath diagnostics

Abstract: Exhaled isoprene could enable non-invasive monitoring of cholesterol-lowering therapies. Here, we report an isoprene-selective sensor at high relative humidity (RH) for the first time (to our knowledge). It is made of nanostructured, chemo-resistive Ti-doped ZnO particles (10–20 nm crystal size) produced by flame spray pyrolysis (FSP) and directly deposited in one step onto compact sensor substrates forming highly porous films. The constituent particles consist of stable Ti-doped ZnO solid solutions for Ti levels up to 10 mol% apparently by substitutional incorporation of Ti4+ into the ZnO wurtzite lattice and dominant presence at the particle surface. These Ti4+ point defects strongly enhance the isoprene sensitivity (>15 times higher than pure ZnO) and turn ZnO isoprene-selective, while also improving its thermal stability. In situ infrared spectroscopy confirms that Ti4+ intensifies the surface interaction of Ti-doped ZnO with isoprene by providing additional sites for chemisorbed hydroxyl species. In fact, at an optimal Ti content of 2.5 mol%, this sensor shows superior isoprene responses compared to acetone, NH3 and ethanol at 90% RH. Most notably, breath-relevant isoprene concentrations can be detected accurately down to 5 ppb with high (>10) signal-to-noise ratio. As a result, an inexpensive isoprene detector has been developed that could be easily incorporated into a portable breath analyzer for non-invasive monitoring of metabolic disorders (e.g. cholesterol).

A facile and one-step ethanol-thermal synthesis of MoS2 quantum dots for two-photon fluorescence imaging

Abstract: Two-photon fluorescent (TPF) molybdenum disulfide quantum dots (MoS2 QDs) were synthesized through a facile and one-step solvothermal approach. The MoS2 QDs exhibit small size and high stability. Because of their low toxicity and TPF ability, the MoS2 QDs are successfully applied in two-photon fluorescence bio-imaging.

3D-printed bioceramic scaffolds with a Fe3O4/graphene oxide nanocomposite interface for hyperthermia therapy of bone tumor cells

Abstract: Simultaneous therapy and regeneration of bone tumor-induced defects still remain to be a significant challenge. Conventional therapy strategy by implanting bone graft materials can regenerate the bone defects after surgery but cannot kill residual tumor cells. In this study, we successfully prepared a 3D-printed β-tricalcium phosphate bioceramic scaffold with surface modification of Fe3O4 nanoparticles/graphene oxide nanocomposite layers (named β-TCP–Fe–GO). The prepared β-TCP–Fe–GO scaffolds possess a highly ordered macroporous structure with triangle pore morphology and a pore size of around 300–500 μm. The struts of β-TCP–Fe–GO scaffolds were uniformly deposited with Fe3O4/GO sandwich-like composite layers in which nano-sized Fe3O4 particles were wrapped by GO sheets. The Fe3O4 content in the β-TCP–Fe–GO scaffolds can be effectively modulated by controlling the coating times; the final content of Fe3O4 in β-TCP–8Fe–GO scaffolds is no more than 1% after coating 8 times. Such low content of Fe3O4 in the scaffolds endows them with super paramagnetic behavior and hyperthermal effects. The temperature of the scaffolds can be modulated in the range 50–80 °C under an alternating magnetic field for 15 minutes by controlling the magnetic intensity and Fe3O4 content. The excellent hyperthermal effect of β-TCP–Fe–GO scaffolds induced more than 75% cell death for osteosarcoma cells (MG-63) in vitro. Furthermore, the β-TCP–Fe–GO scaffolds significantly enhanced alkaline phosphatase (ALP) activity and osteogenic gene expression, such as OPN, Runx2, OCN and BSP, of rabbit bone marrow stromal cells (rBMSCs) and significantly stimulated rBMSCs proliferation as compared to pure β-TCP scaffolds by the synergistic effect of GO and the released Fe ions. Therefore, the prepared β-TCP–Fe–GO scaffolds possess prominent magnetothermal ability and excellent bone-forming activity. This study is believed to pave the way for the design and fabrication of novel tissue engineering scaffolds in a combination of therapy and regeneration functions.