Applications and Degradation of Proteins Used as Tissue Engineering Materials

Biological Functions of Macromolecular Protein Hydrogels in Constructing Osteogenic Microenvironment

Irreversible bone defects resulting from trauma, infection, and degenerative illnesses have emerged as a significant health concern. Structurally and functionally controllable hydrogels made by bone tissue engineering (BTE) have become promising biomaterials. Natural proteins are able to establish connections with autologous proteins through unique biologically active regions. Hydrogels based on proteins can simulate the bone microenvironment and regulate the biological behavior of stem cells in the tissue niche, making them candidates for research related to bone regeneration. This article reviews the biological functions of various natural macromolecular proteins (such as collagen, gelatin, fibrin, and silk fibroin) and highlights their special advantages as hydrogels. Then the latest research trends on cross-linking modified macromolecular protein hydrogels with improved mechanical properties and composite hydrogels loaded with exogenous micromolecular proteins have been discussed. Finally, the applications of protein hydrogels, such as 3D printed hydrogels, microspheres, and injectable hydrogels, were introduced, aiming to provide a reference for the repair of clinical bone defects.

The Use of Small-Molecule Compounds for Cell Adhesion and Migration in Regenerative Medicine

Cell adhesion is essential for cell survival, communication, and regulation, and it is of fundamental importance in the development and maintenance of tissues. Cell adhesion has been widely explored due to its many important roles in the fields of tissue regenerative engineering and cell biology. This is because the mechanical interactions between a cell and its extracellular matrix (ECM) can influence and control cell behavior and function. Currently, biomaterials for regenerative medicine have been heavily investigated as substrates for promoting a cells' adhesive properties and subsequent proliferation, tissue differentiation, and maturation. Specifically, the manipulation of biomaterial surfaces using ECM coatings such as fibronectin extracted from animal-derived ECM have contributed significantly to tissue regenerative engineering as well as basic cell biology research. Additionally, synthetic and natural bioadhesive agents with pronounced abilities to enhance adhesion in numerous biological components and molecules have also been assessed in the field of tissue regeneration. Research into the use of facilitative bioadhesives has aimed to further optimize the biocompatibility, biodegradability, toxicity levels, and crosslinking duration of bioadhesive materials for improved targeted delivery and tissue repair. However, the restrictive drawbacks of some of these bioadhesive and animal-derived materials include the potential risk of disease transmission, immunogenicity, poor reproducibility, impurities, and instability. Therefore, it is necessary for alternative strategies to be sought out to improve the quality of cell adhesion to biomaterials. One promising strategy involves the use of cell-adhesive small molecules. Small molecules are relatively inexpensive, stable, and low-molecular-weight (<1000 Da) compounds with great potential to serve as efficient alternatives to conventional bioadhesives, ECM proteins, and other derived peptides. Over the past few years, a number of cell adhesive small molecules with the potential for tissue regeneration have been reported. In this review, we discuss the current progress using cell adhesive small molecules to regulate tissue regeneration.

Scaffold Using Chitosan, Agarose, Cellulose, Dextran and Protein for Tissue Engineering-A Review

Biological macromolecules like polysaccharides/proteins/glycoproteins have been widely used in the field of tissue engineering due to their ability to mimic the extracellular matrix of tissue. In addition to this, these macromolecules are found to have higher biocompatibility and no/lesser toxicity when compared to synthetic polymers. In recent years, scaffolds made up of proteins, polysaccharides, or glycoproteins have been highly used due to their tensile strength, biodegradability, and flexibility. This review is about the fabrication methods and applications of scaffolds made using various biological macromolecules, including polysaccharides like chitosan, agarose, cellulose, and dextran and proteins like soy proteins, zein proteins, etc. Biopolymer-based nanocomposite production and its application and limitations are also discussed in this review. This review also emphasizes the importance of using natural polymers rather than synthetic ones for developing scaffolds, as natural polymers have unique properties, like high biocompatibility, biodegradability, accessibility, stability, absence of toxicity, and low cost.

Microfluidic Fabrication of Natural Polymer-Based Scaffolds for Tissue Engineering Applications: A Review

Natural polymers, thanks to their intrinsic biocompatibility and biomimicry, have been largely investigated as scaffold materials for tissue engineering applications. Traditional scaffold fabrication methods present several limitations, such as the use of organic solvents, the obtainment of a non-homogeneous structure, the variability in pore size and the lack of pore interconnectivity. These drawbacks can be overcome using innovative and more advanced production techniques based on the use of microfluidic platforms. Droplet microfluidics and microfluidic spinning techniques have recently found applications in the field of tissue engineering to produce microparticles and microfibers that can be used as scaffolds or as building blocks for three-dimensional structures. Compared to standard fabrication technologies, microfluidics-based ones offer several advantages, such as the possibility of obtaining particles and fibers with uniform dimensions. Thus, scaffolds with extremely precise geometry, pore distribution, pore interconnectivity and a uniform pores size can be obtained. Microfluidics can also represent a cheaper manufacturing technique. In this review, the microfluidic fabrication of microparticles, microfibers and three-dimensional scaffolds based on natural polymers will be illustrated. An overview of their applications in different tissue engineering fields will also be provided.

Potential of the Coordinated Actions of Multiple Protein-Based Micromachines for Medical Applications

Untethered mobile micromachines hold great promise in the development of effective and minimally invasive therapies. Although diverse medical micromachines for specific applications have been developed over the past few decades, the coordinated action of multiple machines with different functions remains largely unexplored. In this study, we created three types of biocompatible micromachines using proteins and demonstrated the potential of their coordinated action for medical applications. As a proof of concept, we demonstrated neural replacement therapy, in which neuroblastomas were killed by using an anticancer prodrug and the first machine that contains enzymes, enabling the conversion of the prodrug into a cytotoxic drug. Subsequently, a second machine composed of extracellular matrix was placed on the dead cancer cells to provide a suitable environment for cell adhesion, on which embryonic stem (ES) cells and stromal cells that promote neural differentiation of stem cells were attached by using third machines capable of delivering cells to target positions with desired patterns. As a result, neuroblastomas were replaced with novel healthy neurons derived from ES cells by teaming multiple protein-based machines. We believe that this work highlights the potential of heterogeneous machine groups for medical treatment and the utility of highly biocompatible and functional micromachines made from proteins, representing an important step forward in building more sophisticated micromachine-based therapies.

Recent Progress in Development of Dressings Used for Diabetic Wounds with Special Emphasis on Scaffolds

Diabetic wound (DW) is a secondary application of uncontrolled diabetes and affects about 42.2% of diabetics. If the disease is left untreated/uncontrolled, then it may further lead to amputation of organs. In recent years, huge research has been done in the area of wound dressing to have a better maintenance of DW. These include gauze, films, foams or, hydrocolloid-based dressings as well as polysaccharide- and polymer-based dressings. In recent years, scaffolds have played major role as biomaterial for wound dressing due to its tissue regeneration properties as well as fluid absorption capacity. These are three-dimensional polymeric structures formed from polymers that help in tissue rejuvenation. These offer a large surface area to volume ratio to allow cell adhesion and exudate absorbing capacity and antibacterial properties. They also offer a better retention as well as sustained release of drugs that are directly impregnated to the scaffolds or the ones that are loaded in nanocarriers that are impregnated onto scaffolds. The present review comprehensively describes the pathogenesis of DW, various dressings that are used so far for DW, the limitation of currently used wound dressings, role of scaffolds in topical delivery of drugs, materials used for scaffold fabrication, and application of various polymer-based scaffolds for treating DW.

Double-Modified Bacterial Cellulose/Soy Protein Isolate Composites by Laser Hole Forming and Selective Oxidation Used for Urethral Repair

In this study, a double-modified bacterial cellulose/soybean protein isolate (DMBC/SPI), a new type of urethral tissue engineering scaffold with good biocompatibility, biodegradability, and cell-oriented growth, was prepared. Bacterial cellulose (BC) was physically and chemically modified by laser hole forming and selective oxidation to obtain the double-modified bacterial cellulose (DMBC). The soybean protein isolate (SPI) was compounded on DMBC to obtain DMBC/SPI with better biocompatibility. DMBC/SPI was used to repair the damaged urethra in rabbits. The results showed that DMBC/SPI was beneficial to heal the damaged urethra and did not cause a milder inflammatory response. The repaired urethra was smooth and continuous. DMBC/SPI has a good urethral repair effect and is expected to be used as a new urethral reconstruction material in clinical applications. In addition, FT-IR spectroscopy, SEM, static contact angle measurements, mechanical property investigation, and cell experiments were also performed to characterize the properties of DMBC/SPI composites.

Preclinical efficacy study of a porous biopolymeric scaffold based on gelatin-hyaluronic acid-chondroitin sulfate in a porcine burn injury model: role of critical molecular markers (VEGFA, N-cadherin, COX-2), gamma sterilization efficacy and a comparison of healing potential to Integra™

Development of scaffold from biopolymers can ease the requirements for donor skin autograft and plays an effective role in the treatment of burn wounds. In the current study, a porous foam based, bilayered hydrogel scaffold was developed using gelatin, hyaluronic acid and chondroitin sulfate (G-HA-CS). The fabricated scaffold was characterized physicochemically for pre- and post-sterilization efficacy by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA).In-vitrostudies proved that the scaffold promoted cellular proliferation. The efficacy of G-HA-CS scaffold was compared with Integra™ at different time points (7, 14, 21 and 42 days), in a swine second degree burn wound model. Remarkable healing potential of the scaffold was evident from the wound contraction rate, reduction of IL-6, TNF-αand C3. The expression of healing markers TGF-β1 and collagen 1 revealed significant skin regeneration with regulated fibroblast activation towards the late phase of healing (p< 0.001 at day 21 and 42 vs. control). Expression of Vascular Endothelial Growth Factor A (VEGFA), vimentin and N-cadherin were found to favor angiogenesis and skin regeneration. Mechanistically, scaffold promoted wound healing by modulation of CD-45, cyclooxygenase-2 and MMP-2. Thus, the promising results with foam based scaffold, comparable to Integra™ in swine burn injury model offer an innovative lead for clinical translation for effective management of burn wound.

Strategies for constructing pluripotent stem cell- and progenitor cell-derived three-dimensional cardiac micro-tissues

Three-dimensional (3D) cardiac micro-tissue is a promising model for simulating the structural and functional features of heart in vitro. This scientific achievement provides a platform for exploration about the mechanisms on the development, damage, and regeneration of tissue, hence, paving a way toward development of novel therapies for heart diseases. However, 3D micro-tissue technology is still in its infant stages faced with many challenges such as incompleteness of the tissue microarchitecture, loss of the resident immune cells, poor reproducibility, and deficiencies in continuously feeding the nutrients and removing wastes during micro-tissue culturing. There is an urgent need to optimize the construction of 3D cardiac micro-tissue and improve functions of the involved cells. Therefore, scaffolds and cell resources for building 3D cardiac micro-tissues, strategies for inducing the maturation and functionalization of pluripotent stem cell- or cardiac progenitor cell-derived cardiomyocytes, and the major challenges were reviewed in this writing to enable future fabrication of 3D cardiac micro-tissues or organoids for drug screening, disease modeling, regeneration treatment, and so on.

Protein-, (Poly)peptide-, and Amino Acid-Based Nanostructures Prepared via Polymerization-Induced Self-Assembly

Proteins and peptides, built from precisely defined amino acid sequences, are an important class of biomolecules that play a vital role in most biological functions. Preparation of nanostructures through functionalization of natural, hydrophilic proteins/peptides with synthetic polymers or upon self-assembly of all-synthetic amphiphilic copolypept(o)ides and amino acid-containing polymers enables access to novel protein-mimicking biomaterials with superior physicochemical properties and immense biorelevant scope. In recent years, polymerization-induced self-assembly (PISA) has been established as an efficient and versatile alternative method to existing self-assembly procedures for the reproducible development of block copolymer nano-objects in situ at high concentrations and, thus, provides an ideal platform for engineering protein-inspired nanomaterials. In this review article, the different strategies employed for direct construction of protein-, (poly)peptide-, and amino acid-based nanostructures via PISA are described with particular focus on the characteristics of the developed block copolymer assemblies, as well as their utilization in various pharmaceutical and biomedical applications.

Role of temperature on bio-printability of gelatin methacryloyl bioink in two-step cross-linking strategy for tissue engineering applications

Additive manufacturing has shown promising results in reconstructing three-dimensional (3D) living tissues for various applications, including tissue engineering, regenerative medicine, drug discovery, and high-throughput drug screening. In extrusion-based bioprinters, stable formation of filaments and high-fidelity deposition of bioinks are the primary challenges in fabrication of physiologically relevant tissue constructs. Among various bioinks, gelatin methacryloyl (GelMA) is known as a photocurable and physicochemically tunable hydrogel with a demonstrated biocompatibility and tunable biodegradation properties. The two-step crosslinking of GelMA (reversible thermal gelation and permanent photo-crosslinking) has attracted researchers to make complex tissue constructs. Despite promising results in filament formation and printability of this hydrogel, the effect of temperature on physicochemical properties, cytocompatibility, and biodegradation of the hydrogel are to be investigated. This work studies the effect of thermoreversible, physical crosslinking on printability of GelMA. The results of 3D printing of GelMA at different temperatures followed by irreversible chemical photo-crosslinking show that the decrease in temperature improves the filament formation and shape fidelity of the deposited hydrogel, particularly at the temperatures around 15 °C. Time dependant mechanical testing of the printed samples revealed that decreasing the extruding temperature increases the elastic properties of the extruded filaments. Furthermore, our novel approach in minimizing the slippage effect during rheological study enabled to measure changes in linear and non-linear viscoelastic properties of the printed samples at different temperatures. A considerable increase in storage modulus of the extruded samples printed at lower temperatures confirms their higher solid behavior. Scanning electron microscopy revealed a remarkable decrease in porosity of the extruded hydrogels by decreasing the temperature. Chemical analysis by Fourier-transform infrared spectroscopy and circular dichroism showed a direct relationship between the coil-helix transition in hydrogel macromers and its physical alterations. Finally, biodegradation and cytocompatibility of the extruded hydrogels decreased at lower extruding temperatures.

In vitro and in vivo studies of novel fabricated bioactive dressings based on collagen and zinc oxide 3D scaffolds

The paper reports the synthesis and physico-chemical and biological characterization of novel wound dressings based on collagen and essential oil functionalized ZnO nanoparticles intended to improve the treatment of burns and to reduce the risk for developing wound sepsis in patients with burns or chronic wounds. The prepared wound dressings were physico-chemical characterized by Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). In vitro biocompatibility and cytotoxicity was proved on human fibroblast cells, antimicrobial potential was assessed on Gram positive and Gram negative bacteria models (Staphylococcus aureus and Escherichia coli, respectively), while in vivo studies were performed on a rat burn wound experimental model. Functionalized ZnO nanoparticles (NPs) proved to range 15-20 nm in size and contain about 1% orange essential oil (EO), which was utilized as a natural antimicrobial agent. NPs are grain-shapped and have a low tendency to form aggregates. No toxicity was noticed in vitro, as human fibroblasts maintained a normal growth and their membrane integrity in the presence of EO functionalized NPs. The capacity of the prepared wound dressings to act as implantable bioresorbable scaffolds that accelerates wounds healing along with an excellent biocompatibility, lack of cytotoxicity and a good antibacterial activity, make these materials promising and safe candidates for wound dressing, especially in burn patients.

Cell laden alginate-keratin based composite microcapsules containing bioactive glass for tissue engineering applications

Microcapsules based on alginate-keratin, alginate dialdehyde (ADA)-keratin and ADA-keratin-45S5 bioactive glass (BG) were successfully prepared. The samples were characterized by light microscopy, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The results showed that ADA-based materials possess higher degradation rate compared to alginate-based materials. The incorporation of BG particles (mean particle size: 2.0 µm) improved the bioactivity of the materials. Moreover, the biological properties of the samples were evaluated by encapsulating MG-63 osteosarcoma cells into the microcapsules. The cell viability in all samples increased during 21 days of cultivation. However, the presence of 0.5% BG particle seemed to have initial negative effect on cell growth compared to other samples without BG. On the other hand, the positive effect of CaP formation was visible after 3 weeks in the BG containing samples. The results are relevant to consider the development of cell laden bioinks incorporating inorganic bioactive particles for biofabrication approaches.

Photo-Crosslinked Keratin/Chitosan Membranes as Potential Wound Dressing Materials

In this study, we combined two kinds of natural polymers, chitosan and keratin, to develop a portable composite membrane via UV irradiation. UV-crosslinking without an additional chemical agent makes the fabrication more ideal by reducing reactants and avoiding residual toxic chemicals. This novel composite could perform synergistic functions benefitting from chitosan and keratin; including a strong mechanical strength, biodegradability, biocompatibility, better cell adhesion, and proliferation characteristics. Furthermore, compared with our previous research, this keratin-chitosan composite membrane was improved in that it was made to be portable, enabling it to be versatile and have various applications in vitro and in vivo. Based on these facts, this innovative composite membrane has high potential for serving as an outstanding candidate for wound healing or other biomedical applications.

Protein-Based Fiber Materials in Medicine: A Review

Fibrous materials have garnered much interest in the field of biomedical engineering due to their high surface-area-to-volume ratio, porosity, and tunability. Specifically, in the field of tissue engineering, fiber meshes have been used to create biomimetic nanostructures that allow for cell attachment, migration, and proliferation, to promote tissue regeneration and wound healing, as well as controllable drug delivery. In addition to the properties of conventional, synthetic polymer fibers, fibers made from natural polymers, such as proteins, can exhibit enhanced biocompatibility, bioactivity, and biodegradability. Of these proteins, keratin, collagen, silk, elastin, zein, and soy are some the most common used in fiber fabrication. The specific capabilities of these materials have been shown to vary based on their physical properties, as well as their fabrication method. To date, such fabrication methods include electrospinning, wet/dry jet spinning, dry spinning, centrifugal spinning, solution blowing, self-assembly, phase separation, and drawing. This review serves to provide a basic knowledge of these commonly utilized proteins and methods, as well as the fabricated fibers’ applications in biomedical research.

Multifunctional protein microparticles for medical applications

Micro- and nano-scale intelligent devices can revolutionize the medical field. Although proteins are promising materials for creating biocompatible miniature medical devices with biological functions, construction of complicated solid-state architectures, using inherently vulnerable proteins, remains challenging. Here, I present a sophisticated strategy for constructing a multifunctional microparticle for medical applications using multiple proteins; this strategy achieved the retention of function, increased stability, and orientation control of the proteins in the fabricated particle. As proof-of-concept, the particle, designed to cope with excess reactive oxygen species (ROS) involved in many diseases, was constructed by combining three proteins with different functions. The body of the particle was fabricated using albumin and superoxide dismutase (SOD), and the antibody was incorporated into the surface of the particle in an orientation-controlled manner. The constructed protein microparticle exhibited coordinated activities for coping with ROS, such as capture of the ROS-secreting cells by the incorporated antibody, followed by the elimination of 70% ROS, secreted from the captured cells, by the SOD in the particle. Additionally, diapocynin, loaded to the particle via the drug-binding ability of albumin, was released from the particle, preventing ROS production in the cells. This multifunctional microparticle, constructed from proteins, will profoundly impact the development of intelligent protein-based miniature devices used in medical fields.

Use of hydrogel scaffolds to develop an in vitro 3D culture model of human intestinal epithelium

The human intestinal cell lines: Caco-2 and HT29-MTX cells have been used extensively in 2D and 3D cell cultures as simple models of the small intestinal epithelium in vitro. This study aimed to investigate the potential of three hydrogel scaffolds to support the 3D culture of Caco-2 and HT29-MTX cells and critically assess their use as scaffolds to stimulate villi formation to model a small intestinal epithelium in vitro. Here, alginate, l-pNIPAM, and l-pNIPAM-co-DMAc hydrogels were investigated. The cells were suspended within or layered on these hydrogels and maintained under static or dynamic culture conditions for up to 21days. Caco-2 cell viability was increased when layered on the synthetic hydrogel scaffolds, but reduced when suspended within the synthetic hydrogels. In contrast, HT29-MTX cells remained viable when suspended within or layered on all 3D cultures. Interestingly, cells cultured in and on the alginate hydrogel scaffolds formed multilayer spheroid structures, whilst the cells layered on synthetic hydrogels formed villus-like structures. Immunohistochemistry staining demonstrated positive expression of enterocyte differentiation markers and goblet cell marker. In conclusion, l-pNIPAM hydrogel scaffolds supported both cell lines and induced formation of villus-like structures when cells were layered on and cultured under dynamic conditions. The ability of the l-pNIPAM to recapitulate the 3D structure and differentiate main cell types of human intestinal villi may deliver a potential alternative in vitro model for studying intestinal disease and for drug testing.

STATEMENT OF SIGNIFICANCE

Forty percent of hospital referrals are linked to disorders of the digestive tract. Current studies have utilised animal models or simple cultures of isolated cells which do not behave in the same manner as human intestine. Thus new models are required which more closely mimic the behaviour of intestinal cells. Here, we tested a number of scaffolds and conditions to develop a cell culture model which closely represents the 3D environment seen within the human small intestine. We successfully created structures seen within the intestine which have not previously been possible with other culture models. These models could be used to investigate tissue engineering, drug discovery, and used asan alternative to in vivo animal models in drug toxicity studies.

Bombyx mori Silk Fibroin Scaffolds with Antheraea pernyi Silk Fibroin Micro/Nano Fibers for Promoting EA. hy926 Cell Proliferation

Achieving a high number of inter-pore channels and a nanofibrous structure similar to that of the extracellular matrix remains a challenge in the preparation of Bombyx mori silk fibroin (BSF) scaffolds for tissue engineering. In this study, Antheraea pernyi silk fibroin (ASF) micro/nano fibers with an average diameter of 324 nm were fabricated by electrospinning from an 8 wt % ASF solution in hexafluoroisopropanol. The electrospun fibers were cut into short fibers (~0.5 mm) and then dispersed in BSF solution. Next, BSF scaffolds with ASF micro/nano fibers were prepared by lyophilization. Scanning electron microscope images clearly showed connected channels between macropores after the addition of ASF micro/nano fibers; meanwhile, micro/nano fibers and micropores could be clearly observed on the pore walls. The results of in vitro cultures of human umbilical vein endothelial cells (EA. hy926) on BSF scaffolds showed that fibrous BSF scaffolds containing 150% ASF fibers significantly promoted cell proliferation during the initial stage.

Zein-based composites in biomedical applications

Considerable research efforts have been devoted to zein-based biomaterials for tissue engineering and other biomedical applications over the past decade. The attention given to zein-based polymers is primarily attributed to their biocompatibility and biodegradability. However, due to the relatively low mechanical properties of these polymers, numerous inorganic compounds (e.g., hydroxyapatite, calcium phosphate, bioactive glasses, natural clays) have been considered in combination with zein to create composite materials in an attempt to enhance zein mechanical properties. Inorganic phases also positively impact on the hydrophilic properties of zein matrices inducing a suitable environment for cell attachment, spreading, and proliferation. This review covers available literature on zein and zein-based composite materials, with focus on the combination of zein with commonly used inorganic fillers for tissue engineering and drug delivery applications. An overview of the most recent advances in fabrication techniques for zein-based composites is presented and key applications areas and future developments in the field are highlighted. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1656-1665, 2017.

Biomineralization of Engineered Spider Silk Protein-Based Composite Materials for Bone Tissue Engineering

Materials based on biodegradable polyesters, such as poly(butylene terephthalate) (PBT) or poly(butylene terephthalate-co-poly(alkylene glycol) terephthalate) (PBTAT), have potential application as pro-regenerative scaffolds for bone tissue engineering. Herein, the preparation of films composed of PBT or PBTAT and an engineered spider silk protein, (eADF4(C16)), that displays multiple carboxylic acid moieties capable of binding calcium ions and facilitating their biomineralization with calcium carbonate or calcium phosphate is reported. Human mesenchymal stem cells cultured on films mineralized with calcium phosphate show enhanced levels of alkaline phosphatase activity suggesting that such composites have potential use for bone tissue engineering.

Fabrication and characterization of electrospun zein/Ag nanocomposite mats for wound dressing applications

Wound dressing is a very important factor in the process of wound healing as proper wound care can accelerate the recovery of the wound. In this study, zein nanofibrous mats with fiber diameters around 350-500 nm were prepared by electrospinning and silver (Ag) nanoparticles around 20 nm were concurrently synthesized in situ into the mats. The electrospun nanofibers were characterized by Field Emission-Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis. Cell viability and activity of fibroblasts cells in zein/Ag mats were also evaluated and results demonstrated good cytocompatibility and attachment of cells on the composite nanofibers. Also, the bactericidal activity of the fabricated mats against gram-positive Staphylococcus aureus (S. aureus) and gram-negative Escherichia coli (E. coli) was investigated via zone of inhibition test and results showed high anti-bacterial performance.

Corneal stromal cell growth on gelatin/chondroitin sulfate scaffolds modified at different NHS/EDC molar ratios

A nanoscale modification strategy that can incorporate chondroitin sulfate (CS) into the cross-linked porous gelatin materials has previously been proposed to give superior performance for designed corneal keratocyte scaffolds. The purpose of this work was to further investigate the influence of carbodiimide chemistry on the characteristics and biofunctionalities of gelatin/CS scaffolds treated with varying N-hydroxysuccinimide (NHS)/1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide hydrochloride (EDC) molar ratios (0-1) at a constant EDC concentration of 10 mM. Results of Fourier transform infrared spectroscopy and dimethylmethylene blue assays consistently indicated that when the NHS to EDC molar ratio exceeds a critical level (i.e., 0.5), the efficiency of carbodiimide-mediated biomaterial modification is significantly reduced. With the optimum NHS/EDC molar ratio of 0.5, chemical treatment could achieve relatively high CS content in the gelatin scaffolds, thereby enhancing the water content, glucose permeation, and fibronectin adsorption. Live/Dead assays and interleukin-6 mRNA expression analyses demonstrated that all the test samples have good cytocompatibility without causing toxicity and inflammation. In the molar ratio range of NHS to EDC from 0 to 0.5, the cell adhesion ratio and proliferation activity on the chemically modified samples significantly increased, which is attributed to the increasing CS content. Additionally, the materials with highest CS content (0.143 ± 0.007 nmol/10 mg scaffold) showed the greatest stimulatory effect on the biosynthetic activity of cultivated keratocytes. These findings suggest that a positive correlation is noticed between the NHS to EDC molar ratio and the CS content in the biopolymer matrices, thereby greatly affecting the corneal stromal cell growth.