Genipin-crosslinked chitosan/poly-l-lysine gels promote fibroblast adhesion and proliferation

Fully bio-based grease resistant composite coating: chitosan-Genipin-microfibrillated cellulose for sustainable paper food packaging

As awareness of health concerns continues to rise, the development of new generations of sustainable food packaging materials has emerged as a focal point of significant attention. This study presents the development of a fully bio-based grease resistant composite coating composed of chitosan (CS), genipin (GP), and microfibrillated cellulose (MFC) for sustainable paper food packaging. The synergistic effects of crosslinking between CS and GP, combined with electrostatic interactions between CS and MFC, enabled the formation of a dense, interconnected coating layer on paper substrates. Systematic optimization of coating formulations revealed that a 2 wt% CS, 0.1 wt% GP, and 15 wt% MFC composition achieved maximum grease resistance (kit rating: 12/12) at a remarkably low coating weight of 4 g/m2, outperforming existing chitosan-based coatings requiring higher application weights for medium performance. The composite coating significantly enhanced mechanical properties, with two kinds of food wrapping paper after coating exhibiting tensile strength improvements of 25 % and 13 %, and burst strength increases of 25 % and 41 %, respectively. Additionally, water vapor transmission rates decreased by 22 % and 28 %, demonstrating enhanced moisture barrier functionality. Practical evaluations have confirmed the coating's robust resistance to various organic solvents, as well as its stability in hot oil. Simulated food contact tests using fried chicken and sausages revealed no detectable grease penetration or structural compromise in coated papers. This study establishes the CS/GP/MFC coating as a high-performance, environmentally sustainable alternative to fluorinated and non-biodegradable materials, with broad applicability in grease resistant food packaging systems.

Bioadhesive Nanoparticles in Topical Drug Delivery: Advances, Applications, and Potential for Skin Disorder Treatments

Skin disorders are the fourth most common cause of all diseases, which affect nearly one-third of the world's population. Topical drug delivery can be effective in treating a range of skin disorders, including microbial infections, skin cancer, dermatitis, burn injury, wounds, and psoriasis. Bioadhesive nanoparticles (BNPs) can serve as an efficient topical drug delivery system as they can serve dual purposes as bioadhesives and nanocarriers, which can mediate targeted drug delivery, prolong retention time, and deepen drug penetration through skin layers. There is an increasing demand for BNP-based applications in medicine because of their various advantages, including biodegradability, flexibility, biocompatibility, and enhanced adhesive strength. A number of BNPs have already been developed and evaluated as potential topical drug delivery systems. In addition, a range of studies have already been carried out to evaluate the potential of BNPs in the treatment of various skin disorders, including atopic dermatitis, irritant contact dermatitis, skin cancer, psoriasis, microbial infections, wounds, and severe burn injuries. This review article is timely and unique, because it provides an extensive and unique summary of the recent advances of BNPs in the treatment of wide-ranging skin disorders. Moreover, this review also provides a useful discussion on the bioadhesion mechanism and various biopolymers that can be used to prepare BNPs.

Lysine-Mediated Yttrium Oxide Nanoparticle-Incorporated Nanofibrous Scaffolds with Tunable Cell Adhesion, Proliferation, and Antimicrobial Potency for In Vitro Wound-Healing Applications

The intricate healing mechanism of chronic wounds and their multitude of healing-related obstacles, such as infections, compromised cellular processes, and impediments to the healing process, pose a significant healthcare problem. Exploration of metal oxide nanoparticles, such as yttrium oxide (Y2O3) nanoparticles, can lead to innovative discoveries in the field of chronic wound healing by offering cues that promote cell proliferation in the scaffolds. To achieve this, Y2O3 nanoparticles were synthesized and incorporated within poly(vinyl alcohol) (PVA) nanofibrous scaffolds. Moreover, lysine was infused in the nanofibrous scaffolds to tune its cell adhesion and antimicrobial property. The structure and morphology of the synthesized nanofibers were confirmed through various physicochemical characterizations. Notably, all the fabricated scaffolds have remarkably tuned WVTR values within the range of 2000-2500 g/m2/day, favorable for removing the wound exudate, which facilitate the healing process. The scaffolds exhibited substantial antimicrobial property of approximately 68% and 72.2% against both E. coli and S. aureus at optimized Y2O3 loading. They further prevented the formation of biofilm by 68.6% for S. aureus and 51.2% for P. aeruginosa, suggesting the inhibition of recurrent wound infection. The scaffolds illustrated good blood biocompatibility, cytocompatibility, and cell adhesion capabilities. In vitro ROS inhibition study also corroborated the antioxidant property of the scaffold. Similarly, the wound scratching experiment showed high proliferative capability of a yttria-loaded PVA/lysine (S3) sample through the development of an extracellular matrix support. Molecular insight of wound healing was also validated through flow cytometry analysis and immunocytochemistry imaging studies. The findings revealed increased collagen I (Col-I) expression of approximately 19.48% in cultured fibrocytes. The findings are validated from immunocytochemistry imaging. In summary, the results furnish a captivating paradigm for the use of these scaffolds as a therapeutic biomaterial and to foster their potential efficacy toward wound care management.

Wound healing potential of silver nanoparticles embedded in optimized bio-inspired hybridized chitosan soft and dry hydrogel

Interactive wound dressings combining healing and antimicrobial potentials, besides ensuring patient compliance with a recognized wound care service gained considerable interest recently. Both hydrogel spray dried microparticles (HMP) and soft hydrogel (G) were prepared. The bio-inspired combinatory platform included natural bio-macromolecules namely: chitosan (CS) and collagen (COL) with wound healing enhancement and connective tissue building capabilities cross linked with the natural genipin (GN) to build a three dimensional structured matrix. The optimized plain hydrogel obtained by a box behnken design (BBD) program (G) scored maximum swelling and porosity. The network was hosted with green synthesized cefotaxime sodium (cef.Na) AgNPs reduced by the anabolic folic acid (FA). Both hydrogels exhibited good antimicrobial activity against gram +ve and -ve bacteria. The wound healing activity, evaluated in injured rats, showed >98 % and complete wound closure after two and three weeks respectively. Oxidative stress minimization was proved by the estimation of biochemical markers malondialdehyde (MDA) and superoxide dismutase (SOD) levels at the wound site.

Marine-derived polysaccharides and their therapeutic potential in wound healing application - A review

Polysaccharides originating from marine sources have been studied as potential material for use in wound dressings because of their desirable characteristics of biocompatibility, biodegradability, and low toxicity. Marine-derived polysaccharides used as wound dressing, provide several benefits such as promoting wound healing by providing a moist environment that facilitates cell migration and proliferation. They can also act as a barrier against external contaminants and provide a protective layer to prevent further damage to the wound. Research studies have shown that marine-derived polysaccharides can be used to develop different types of wound dressings such as hydrogels, films, and fibres. These dressings can be personalised to meet specific requirements based on the type and severity of the wound. For instance, hydrogels can be used for deep wounds to provide a moist environment, while films can be used for superficial wounds to provide a protective barrier. Additionally, these polysaccharides can be modified to improve their properties, such as enhancing their mechanical strength or increasing their ability to release bioactive molecules that can promote wound healing. Overall, marine-derived polysaccharides show great promise for developing effective and safe wound dressings for various wound types.

Reaction kinetics of chitosan nanogels crosslinked by genipin

Crosslinking of chitosan chains in dilute solution by natural crosslinker genipin leads to biocompatible nanogels. Here we investigated the reaction kinetics between chitosan and genipin in a 200 mM acetate buffer at 37 °C, and the structural and conformational evolutions of the nanogels during the crosslinking reaction by multi detection asymmetric flow field-flow fractionation (AF4). Upon crosslinking by genipin, the z-average hydrodynamic radius Rhz of the chitosan chains increased from 26 nm to 130 nm, while the weight average molar mass Mw increased from 2.0 × 105 g/mol to 1.8 × 107 g/mol. The crosslinking reaction appeared to be first-order and size-dependent. In particular, the intrachain crosslinking reaction was preferentially for nanogels having the larger size, leading to formation of branched chains/nanogels having a wide range of molar masses between 106 and 108 g/mol but a similar radius of gyration Rg ∼ 40 nm. For the largest nanogel fractions with M > 2.0 × 108 g/mol, both Rg and Rh showed a scaling relation with exponent 1/3 and a structure parameter Rg/Rh = 0.74, as expected for the hard sphere particle. The reaction was accompanied by a reduction of charge density and an increase in hydrophobicity of chitosan nanogels, which plays a key role in the formation of uniform size nanogels with chain density ρ(Rh) up to 0.45 g/cm3.

The Diamond Concept Enigma: Recent Trends of Its Implementation in Cross-linked Chitosan-Based Scaffolds for Bone Tissue Engineering

An increasing number of publications over the past ten years have focused on the development of chitosan-based cross-linked scaffolds to regenerate bone tissue. The design of biomaterials for bone tissue engineering applications relies heavily on the ideals set forth by a polytherapy approach called the "Diamond Concept". This methodology takes into consideration the mechanical environment, scaffold properties, osteogenic and angiogenic potential of cells, and benefits of osteoinductive mediator encapsulation. The following review presents a comprehensive summarization of recent trends in chitosan-based cross-linked scaffold development within the scope of the Diamond Concept, particularly for nonload-bearing bone repair. A standardized methodology for material characterization, along with assessment of in vitro and in vivo potential for bone regeneration, is presented based on approaches in the literature, and future directions of the field are discussed.

Effect of Selected Crosslinking and Stabilization Methods on the Properties of Porous Chitosan Composites Dedicated for Medical Applications

Chitosan is one of the most commonly employed natural polymers for biomedical applications. However, in order to obtain stable chitosan biomaterials with appropriate strength properties, it is necessary to subject it to crosslinking or stabilization. Composites based on chitosan and bioglass were prepared using the lyophilization method. In the experimental design, six different methods were used to obtain stable, porous chitosan/bioglass biocomposite materials. This study compared the crosslinking/stabilization of chitosan/bioglass composites with ethanol, thermal dehydration, sodium tripolyphosphate, vanillin, genipin, and sodium β-glycerophosphate. The physicochemical, mechanical, and biological properties of the obtained materials were compared. The results showed that all the selected crosslinking methods allow the production of stable, non-cytotoxic porous composites of chitosan/bioglass. The composite with genipin stood out with the best of the compared properties, taking into account biological and mechanical characteristics. The composite stabilized with ethanol is distinct in terms of its thermal properties and swelling stability, and it also promotes cell proliferation. Regarding the specific surface area, the highest value exposes the composite stabilized by the thermal dehydration method.

A kidney proximal tubule model to evaluate effects of basement membrane stiffening on renal tubular epithelial cells

The kidney tubule consists of a single layer of epithelial cells supported by the tubular basement membrane (TBM), a thin layer of specialized extracellular matrix (ECM). The mechanical properties of the ECM are important for regulating a wide range of cell functions including proliferation, differentiation and cell survival. Increased ECM stiffness plays a role in promoting multiple pathological conditions including cancer, fibrosis and heart disease. How changes in TBM mechanics regulate tubular epithelial cell behavior is not fully understood. Here we introduce a cell culture system that utilizes in vivo-derived TBM to investigate cell-matrix interactions in kidney proximal tubule cells. Basement membrane mechanics was controlled using genipin, a biocompatibility crosslinker. Genipin modification resulted in a dose-dependent increase in matrix stiffness. Crosslinking had a marginal but statistically significant impact on the diffusive molecular transport properties of the TBM, likely due to a reduction in pore size. Both native and genipin-modified TBM substrates supported tubular epithelial cell growth. Cells were able to attach and proliferate to form confluent monolayers. Tubular epithelial cells polarized and assembled organized cell-cell junctions. Genipin modification had minimal impact on cell viability and proliferation. Genipin stiffened TBM increased gene expression of pro-fibrotic cytokines and altered gene expression for N-cadherin, a proximal tubular epithelial specific cell-cell junction marker. This work introduces a new cell culture model for cell-basement membrane mechanobiology studies that utilizes in vivo-derived basement membrane. We also demonstrate that TBM stiffening affects tubular epithelial cell function through altered gene expression of cell-specific differentiation markers and induced increased expression of pro-fibrotic growth factors.

Glucose and MMP-9 dual-responsive hydrogel with temperature sensitive self-adaptive shape and controlled drug release accelerates diabetic wound healing

Chronic diabetic wounds are an important healthcare challenge. High concentration glucose, high level of matrix metalloproteinase-9 (MMP-9), and long-term inflammation constitute the special wound environment of diabetic wounds. Tissue necrosis aggravates the formation of irregular wounds. All the above factors hinder the healing of chronic diabetic wounds. To solve these issues, a glucose and MMP-9 dual-response temperature-sensitive shape self-adaptive hydrogel (CBP/GMs@Cel&INS) was designed and constructed with polyvinyl alcohol (PVA) and chitosan grafted with phenylboric acid (CS-BA) by encapsulating insulin (INS) and gelatin microspheres containing celecoxib (GMs@Cel). Temperature-sensitive self-adaptive CBP/GMs@Cel&INS provides a new way to balance the fluid-like mobility (self-adapt to deep wounds quickly, approximately 37 °C) and solid-like elasticity (protect wounds against external forces, approximately 25 °C) of self-adaptive hydrogels, while simultaneously releasing insulin and celecoxib on-demand in the environment of high-level glucose and MMP-9. Moreover, CBP/GMs@Cel&INS exhibits remodeling and self-healing properties, enhanced adhesion strength (39.65 ± 6.58 kPa), down-regulates MMP-9, and promotes cell proliferation, migration, and glucose consumption. In diabetic full-thickness skin defect models, CBP/GMs@Cel&INS significantly alleviates inflammation and regulates the local high-level glucose and MMP-9 in the wounds, and promotes wound healing effectively through the synergistic effect of temperature-sensitive shape-adaptive character and the dual-responsive system.

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The hydrogel with temperature-sensitive adaptive shape can fill irregular wounds.

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The hydrogel on-demand releases drugs responding to diabetic wound environment.

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The hydrogel significantly accelerated diabetic wound healing.

Genipin-crosslinked amphiphilic chitosan films for the preservation of strawberry

As a material for films used to keep fruits fresh, chitosan has attracted extensive interest because of its advantages of degradability, environmental friendliness, and biocompatibility. In this study, two amphiphilic chitosan derivative films were prepared by crosslinking N-2-hydroxypropyl-3-butyl ether-O-carboxymethyl chitosan (HBCC) and N-2-hydroxypropyl-3-(2-ethylhexyl glycidyl ether)-O-carboxymethyl chitosan (H2ECC)) with genipin, an excellent natural cross-linking agent. The microstructures, mechanical properties, water vapor permeability, swelling ratios, light transmittance, wettability, thermal stability, antibacterial properties, and biocompatibility of the crosslinked films were characterized. The results showed that the crosslinked films had compact structures, low moisture permeability, strong water resistance, strong ultraviolet resistance, unaffected visible light transmittance, and good hydrophilicity. Compared with the uncrosslinked films, the tensile strength of the genipin-crosslinked ones was increased by 328.33 % (HBCC) and 397.83 % (H2ECC). More importantly, the crosslinked films had strong antibacterial activity against Staphylococcus aureus and Escherichia coli and were non-toxic to endothelial cells. The crosslinked films could effectively prolong the preservation time of strawberries, inhibit the decay of strawberries, and inhibit the reduction of vitamin C in strawberries. In conclusion, genipin-crosslinked HBCC and H2ECC films are potential fruit preservation materials.

A Review on Electrospun Poly(amino acid) Nanofibers and Their Applications of Hemostasis and Wound Healing

The timely and effective control and repair of wound bleeding is a key research issue all over the world. From traditional compression hemostasis to a variety of new hemostatic methods, people have a more comprehensive understanding of the hemostatic mechanism and the structure and function of different types of wound dressings. Electrospun nanofibers stand out with nano size, high specific surface area, higher porosity, and a variety of complex structures. They are high-quality materials that can effectively promote wound hemostasis and wound healing because they can imitate the structural characteristics of the skin extracellular matrix (ECM) and support cell adhesion and angiogenesis. At the same time, combined with amino acid polymers with good biocompatibility not only has high compatibility with the human body but can also be combined with a variety of drugs to further improve the effect of wound hemostatic dressing. This paper summarizes the application of different amino acid electrospun wound dressings, analyzes the characteristics of different materials in preparation and application, and looks forward to the development of directions of poly(amino acid) electrospun dressings in hemostasis.

Silver Nanoparticles Improve the Biocompatibility and Reduce the Immunogenicity of Xenogeneic Scaffolds Derived from Decellularized Pancreas

Xenogeneic scaffolds derived from the decellularized pancreas are plausible biomedical materials for pancreatic tissue engineering applications. During the decellularized process, the ultrastructure of extracellular matrices, including collagen fibers, was destructed, which leads to the decrease of mechanical strength and the immune-inflammatory response after transplantation in vivo. The cross-linking method plays an important role in increasing mechanical strength and reducing the inflammatory potential of decellularized scaffolds. However, no ideal cross-linking agent has been identified for decellularized pancreatic scaffolds yet. In this study, a cyclic perfusion system was used to cross-link decellularized pancreatic scaffolds from Sprague Dawley rat with silver nanoparticles (AgNPs). The optimum concentration of AgNPs was selected according to the scanning electron microscope observation and mechanical evaluation, as well as cytotoxicity to human umbilical vein endothelial cells and MIN-6 cell lines in vitro. The inflammation after transplantation in vivo was evaluated by hematoxylin and eosin staining; M1/M2 polarization phenotype of macrophages was further evaluated. Our results showed that after cross-linking, the scaffold possessed better mechanical property and biocompatibility, with the polarization of M2 macrophages increased. Thus, AgNP-cross-linked pancreatic acellular scaffold can provide an ideal scaffold source for pancreatic tissue engineering.

Layer-by-Layer Cell Encapsulation for Drug Delivery: The History, Technique Basis, and Applications

The encapsulation of cells with various polyelectrolytes through layer-by-layer (LbL) has become a popular strategy in cellular function engineering. The technique sprang up in 1990s and obtained tremendous advances in multi-functionalized encapsulation of cells in recent years. This review comprehensively summarized the basis and applications in drug delivery by means of LbL cell encapsulation. To begin with, the concept and brief history of LbL and LbL cell encapsulation were introduced. Next, diverse types of materials, including naturally extracted and chemically synthesized, were exhibited, followed by a complicated basis of LbL assembly, such as interactions within multilayers, charge distribution, and films morphology. Furthermore, the review focused on the protective effects against adverse factors, and bioactive payloads incorporation could be realized via LbL cell encapsulation. Additionally, the payload delivery from cell encapsulation system could be adjusted by environment, redox, biological processes, and functional linkers to release payloads in controlled manners. In short, drug delivery via LbL cell encapsulation, which takes advantage of both cell grafts and drug activities, will be of great importance in basic research of cell science and biotherapy for various diseases.

An antibacterial ε-poly-L-lysine-derived bioink for 3D bioprinting applications

Limited bioinks have hindered applying 3D bioprinting to tissue engineering, and bacterial infection is a serious threat to these applications. Aiming to solve this problem, a novel ε-poly-L-lysine (EPL) derived...

Poly (l-lactic acid) membrane crosslinked with Genipin for guided bone regeneration

In this study, we chemically modified poly(L-lactic acid) (PLLA) with functional amine groups and fabricated a PLLA membrane crosslinked with genipin as a biomembrane for inducing guided bone regeneration (GBR). The mechanical strength of the PLLA-amine membrane was improved by crosslinking with genipin compared to pure PLLA membrane. The surface of the PLLA-amine membrane crosslinked with genipin had many more uniform pores. Attachment and proliferation of MC3T3-E1 cells were increased and improved on the PLLA-amine membrane crosslinked with genipin. In an in vitro osteogenesis study, MC3T3-E1 cells on the PLLA membrane showed higher alkaline phosphatase (ALP) activity and calcification ability evaluated by alizarin red S staining than those on the pure PLLA membrane. When a skull defect hole of a rat was covered with the PLLA-amine membrane crosslinked with genipin, vigorous new bone regeneration determined by computed tomography at 8 weeks post operation was superior to that when the skull defect was covered with the pure PLLA membrane. Taken together, these results demonstrate that the PLLA-amine membrane crosslinked with genipin has a promising therapeutic application to GBR as a barrier membrane for covering the defect site.

Solution-Blown Poly(hydroxybutyrate) and ε-Poly-l-lysine Submicro- and Microfiber-Based Sustainable Nonwovens with Antimicrobial Activity for Single-Use Applications

Antimicrobial nonwovens for single use applications (e.g., diapers, sanitary napkins, medical gauze, etc.) are of utmost importance as the first line of defense against bacterial infections. However, the utilization of petrochemical nondegradable polymers in such nonwovens creates sustainability-related issues. Here, sustainable poly(hydroxybutyrate) (PHB) and ε-poly-l-lysine (ε-PLL) submicro- and microfiber-based antimicrobial nonwovens produced by a novel industrially scalable process, solution blowing, have been proposed. In such nonwovens, ε-PLL acts as an active material. In particular, it was found that most of ε-PLL is released within the first hour of deployment, as is desirable for the applications of interest. The submicro- and microfiber mat was tested against C. albicans and E. coli, and it was found that ε-PLL-releasing microfibers result in a significant reduction of bacterial colonies. It was also found that ε-PLL-releasing antimicrobial submicro- and microfiber nonwovens are safe for human cells in fibroblast culture. Mechanical characterization of these nonwovens revealed that, even though they are felt as soft and malleable, they possess sufficient strength, which is desirable in the end-user applications.

Applications of bacteria and their derived biomaterials for repair and tissue regeneration

Microorganisms such as bacteria and their derived biopolymers can be used in biomaterials and tissue regeneration. Various methods have been applied to regenerate damaged tissues, but using probiotics and biomaterials derived from bacteria with improved economic-production efficiency and highly applicable properties can be a new solution in tissue regeneration. Bacteria can synthesize numerous types of biopolymers. These biopolymers possess many desirable properties such as biocompatibility and biodegradability, making them good candidates for tissue regeneration. Here, we reviewed different types of bacterial-derived biopolymers and highlight their applications for tissue regeneration.

Immobilization of laccase via cross-linked enzyme aggregates prepared using genipin as a natural cross-linker

Genipin is a nontoxic natural cross-linker that was successfully used to prepare cross-linked enzyme aggregates (CLEAs) of Trametes versicolor laccase. The recovered activity of CLEAs was influenced by the co-solvent type, genipin concentration, cross-linking time, preparation pH, and bovine serum albumin (BSA; amino group feeder) concentration. The characteristics of CLEAs prepared using genipin under optimal conditions (genipin-BSA-CLEAs) were compared with those of typical CLEAs prepared using glutaraldehyde or dextran polyaldehyde. Genipin-BSA-CLEAs were nano-sized (average diameter, approximately 700 nm), had a ball-like shape, showed a narrow size distribution, and exhibited the highest substrate affinity among the prepared CLEAs. The thermal stability of genipin-BSA-CLEAs was 6.8-fold higher than that of free laccase, and their pH stability was also much higher than that of free laccase in the tested range. Additionally, genipin-BSA-CLEAs retained 85% of their initial activity after 10 cycles of reuse. Particularly, genipin-BSA-CLEAs showed higher thermal and pH stability than CLEAs that were cross-linked using glutaraldehyde. Therefore, genipin represents an alternative to toxic compounds such as glutaraldehyde during cross-linking to prepare CLEAs.

Dual functionalized chitosan based composite hydrogel for haemostatic efficacy and adhesive property

The objective of this study was to devise a dual functionalized chitosan based hydrogel dressing to control haemorrhage/ bleeding. The haemostatic hydrogel was formulated by amalgamation of a definite ratio of quaternized chitosan and phosphorylated chitosan along with tannic acid which acted as adjuvant hemostat and a crosslinker. Additionally, the hydrogel contained poly-Ɛ-lysine to impart the elastic and adhesive properties. The optimized hydrogel exhibited superior haemostatic activity (clotting time, 225 ± 5 s), platelet activation (soluble P-selectin concentration 2098 ± 150.19 ng mL^-1), adhesion strength (almost 3 times higher in comparison to Axiostat), higher fluid absorption (approx. 14 times in 12 h) in addition to better mechanical properties, faster coagulation attributes (Prothrombin time, 12.6 s and activated partial thromboplastin time, 30.1 s) and lower proinflammatory potential (almost 3 times lower Tumor Necrosis Factor- α levels and 45 times lower InterLeukin-6 levels at 48 h against control) over marketed chitosan based dressing (clotting time, 300 ± 25 s). Cytotoxicity studies using L929 fibroblasts cells and in-vivo studies using Wistar rats confirmed that the optimized hydrogel was non-toxic, cytocompatible and biocompatible.

Fabrication, characterization and cytocompatibility assessment of gelatin nanofibers coated with a polymer thin film by initiated chemical vapor deposition

The presence of various functional groups in the structure of gelatin nanofibers (GNFs) has made it a suitable candidate for biomedical applications, yet its fast dissolution in aqueous media has been a real challenge for years. In the present work, we propose an efficient procedure to improve the durability of the GNFs. The electrospun GNFs were coated with poly(ethylene glycol dimethacrylate) (pEGDMA) using initiated chemical vapor deposition (iCVD) as a completely dry polymerization method. Morphological and chemical analysis revealed that an ultrathin layer formed around nanofibers (iCVD-GNFs) which has covalently bonded to gelatin chains. Against the instant dissolution of GNFs, the in vitro biodegradability test showed the iCVD-GNFs, to a large extent, preserve their morphology after 14 days of immersion and did not lose its integrity even after 31 days. In vitro cell culture studies, also, revealed cytocompatibility of the iCVD-GNFs for human fibroblast cells (hFC), as well as higher cell proliferation on the iCVD-GNFs compared to control made from tissue culture plate (TCP). Furthermore, contact angle measurements indicated that the hydrophilic GNFs became hydrophobic after the iCVD, yet FE-SEM images of cell-seeded iCVD-GNFs showed satisfactory cell adhesion. Taken together, the proposed method paves a promising way for the production of water-resistant GNFs utilized in biomedical applications; for instance, tissue engineering scaffolds and wound dressings.

Development of a poly(vinyl alcohol)/lysine electrospun membrane-based drug delivery system for improved skin regeneration

Nanofiber-based wound dressings are currently being explored as delivery systems of different biomolecules for avoiding skin infections as well as improve/accelerate the healing process. In the present work, a nanofibrous membrane composed of poly(vinyl alcohol) (PVA) and lysine (Lys) was produced by using the electrospinning technique. Further, anti-inflammatory (ibuprofen (IBP)) and antibacterial (lavender oil (LO)) agents were incorporated within the electrospun membrane through blend electrospinning and surface physical adsorption methods, respectively. The obtained results demonstrated that the PVA_Lys electrospun membranes incorporating IBP or LO displayed the suitable morphological, mechanical and biological properties for enhancing the wound healing process. Moreover, the controlled and sustained release profile attained for IBP was appropriate for the duration of the wound healing inflammatory phase, whereas the initial burst release of LO is crucial to prevent wound bacterial contamination. Indeed, the PVA_Lys_LO electrospun membranes were able to mediate a strong antibacterial activity against both S. aureus and P. aeruginosa, without compromising human fibroblasts viability. Overall, the gathered data emphasizes the potential of the PVA_Lys electrospun membranes-based drug delivery systems to be used as wound dressings.

Naturally-derived biopolymers: Potential platforms for enzyme immobilization

Naturally-derived biopolymers such as alginate, chitosan, cellulose, agarose, guar gum/guaran, agar, carrageenan, gelatin, dextran, xanthan, and pectins, etc. have appealed significant attention over the past several years owing to their natural abundance and availability all over the years, around the globe. In addition, their versatile properties such as non-toxicity, biocompatibility, biodegradability, flexibility, renewability, and the availability of numerous reactive sites offer significant functionalities with multipurpose applications. At present, intensive research efforts have been focused on engineering enzymes using natural biopolymers as novel support/composite materials for diverse applications in biomedical, environmental, pharmaceutical, food and biofuel/energy sectors. Immobilization appears as a straightforward and promising approach to developing biocatalysts with improved catalytic properties as compared to their free counterparts. Biopolymers-assisted enzymes are more stable, robust, and recoverable than that of free forms, and can be employed for continuous biocatalytic reactions. The present review highlights the recent developments and use of biopolymers and their advanced composites as support carriers for the immobilization of a variety of different enzymes to develop biocatalysts with desired catalytic activity and stability characteristics for emerging applications.

Adhesive free-standing multilayer films containing sulfated levan for biomedical applications

This work is the first reporting the use of layer-by-layer to produce adhesive free-standing (FS) films fully produced using natural-based macromolecules: chitosan (CHI), alginate (ALG) and sulfated levan (L-S). The deposition conditions of the natural polymers were studied through zeta potential measurements and quartz crystal microbalance with dissipation monitoring analysis. The properties of the FS films were evaluated and compared with the control ones composed of only CHI and ALG in order to assess the influence of levan polysaccharide introduced in the multilayers. Tensile tests, dynamic mechanical analysis and single lap shear strength tests were performed to evaluate the mechanical properties of the prepared FS films. The presence of L-S conferred both higher tensile strength and shear strength to the developed FS membranes. The results showed an adhesion strength 4 times higher than the control (CHI/ALG) FS films demonstrating the adhesive character of the FS films containing L-S. Morphological and topography studies were carried out revealing that the crosslinking reaction granted the L-S based FS film with a higher roughness and surface homogeneity. Preliminary biological assays were performed by cultivating myoblasts cells on the surface of the produced FS films. Both crosslinked and uncrosslinked FS films containing L-S were cytocompatible and myoconductive.

STATEMENT OF SIGNIFICANCE

Sutures remain as the "gold standard" for wound closure and bleeding control; however they still have limitations such as, high infection rate, inconvenience in handling, and concern over possible transmission of blood-borne disease through the use of needles. One of the challenges of tissue engineering consist on the design and development of biocompatible tissue adhesives and sealants with high adhesion properties to repair or attach devices to tissues. In this work, the introduction of sulfated levan (L-S) on multilayered free-standing membranes was proposed to confer adhesive properties. Moreover, the films were myoconductive even in the absence of crosslinking just by the presence of L-S. This study provides a promising strategy to develop biological adhesives and for cardiac tissue engineering applications.

The bioconjugation mechanism of purine cross-linkers affects microstructure and cell response to ultra rapidly gelling purine–chitosan sponges

As a cell carrier, cross-linking is one of the most common approaches used to provide chitosan with greater structural integrity.

Preparation and characterization of novel chitosan and β-cyclodextrin polymer sponges for wound dressing applications

Chitosan (CS) presents antibacterial, mucoadhesive and hemostatic properties and is an ideal candidate for wound dressing applications. This work reports the development of sponge-like materials obtained from physical hydrogels after the interaction between CS and a β-cyclodextrin polymer (PCD) in acidic conditions to provoke immediate gelation. Characterization consisted of zeta potential (ZP) measurements, rheology analysis, Fourier transform infrared (FTIR), Raman spectroscopy, wide angle X-ray scattering (WAXS) and scanning electron microscopy (SEM). Swelling behavior, cytotoxicity, drug sorption and drug delivery properties of sponges were assessed. ZP indicated that CS and PCD presented opposite charges needed for physical crosslinking. Rheology, swelling, and cytotoxicity of sponges depended on their CS:PCD weight ratios. Increasing PCD in the mixture delayed the gel time, reduced the swelling and increased the cytotoxicity. FTIR and Raman confirmed the physical crosslinking between CS and PCD through ionic interactions, and WAXS showed the amorphous state of the sponges. Finally, the efficiency of chlorhexidine loaded sponge against S. aureus bacteria was proved for up to 30days in agar diffusion tests.

Tuning cell adhesive properties via layer-by-layer assembly of chitosan and alginate

Understanding the mechanisms controlling cell-multilayer film interactions is crucial to the successful engineering of these coatings for biotechnological and biomedical applications. Herein, we present a strategy to tune the cell adhesive properties of multilayers based on marine polysaccharides with and without cross-linking and/or coating with extracellular matrix proteins. Chemical cross-linking of multilayers improved mechanical properties of the coatings but also elicited changes in surface chemistry that alter the adhesion of human umbilical vein endothelial cells. We evaluated a strategy to decouple the mechanical and chemical properties of these films, enabling the transition from cell-adhesive to cell-resistant multilayers. Addition of chitosan/alginate multilayers on top of cross-linked films decreased endothelial cell adhesion, spreading, and proliferation to similar levels as uncross-linked films. Our findings highlight the key role of surface chemistry in cell-multilayer film interactions, and these engineered nanocoatings represent a tunable model of cell adhesive and non-adhesive multilayered films.

STATEMENT OF SIGNIFICANCE

Multilayered films based on marine-derived polysaccharides were obtained by layer-by-layer (LbL). Biological tests with human umbilical vein endothelial cells (HUVECs) showed the potential of these films to tailor cell adhesion, spreading and proliferation. These multilayered films promise to be versatile and tunable model of cell adhesive and non-adhesive films.

Chitosan/Mimosa tenuiflora films as potential cellular patch for skin regeneration

Bio-composites films were prepared by casting and drying of aqueous solutions containing different weight ratios of chitosan and bark of Mimosa tenuiflora. The physico-chemical and functional properties of the films were characterized by scanning electron microscopy, dynamical mechanical analysis, wettability, cytotoxicity and in vitro antibacterial activities. The morphology studies confirmed that the presence of Mimosa tenuiflora change the surface of films. Moreover, the incorporation of Mimosa tenuiflora improved the thermal stability of the films, as it was indicated by the changes in the glass temperatures obtained. Water-uptake ability changed in relation to polymeric composition of film. This property increased by the addition of Mimosa tenuiflora to the film. Improved antibacterial properties were measured against Escherichia Coli and Micrococcus lysodeikticus or luteus. Finally, cytotoxicity was studied by MTT assay and the films were non-toxic. These preliminary results provide a cheap way to prepare chitosan/Mimosa tenuiflora films for wound healing and skin regeneration.

A photo-polymerized poly(Nε-acryloyl l-lysine) hydrogel for 3D culture of MCF-7 breast cancer cells

The most common in vitro cell culture platform, standard two-dimensional (2D) monolayer cell culture, often fails to mimic the tumor microenvironment, while animal models complicate research on the effect of individual factors on cell behaviors. Both are unsatisfactory in the research of molecular mechanisms of tumor development and progression and the discovery and development of anticancer drugs. In vitro three-dimensional (3D) cell culture can partially simulate in vivo conditions and 3D-cultured cancer cells can recapture many essential features of native tumor tissues. In this study, to mimic the in vivo breast tumor microenvironment, novel reduction-responsive poly(N_ε-acryloyl l-lysine) (pLysAAm) hydrogels were synthesized by rapid photo-polymerization of N_ε-acryloyl l-lysine and using N,N'-bis(acryloyl)-(l)-cystine as a crosslinker, and their physicochemical properties were characterized systemically. The results showed that the pLysAAm hydrogels were formed within 93 s under UV irradiation and exhibited almost total elastic recovery from compressions as high as 75%. The lyophilized hydrogel samples displayed a highly porous structure with interconnected pores, had an equilibrium swelling ratio of about 20, and were degraded faster in a glutathione-containing solution than in PBS solution. The biological versatility of the pLysAAm hydrogels was demonstrated by both in vitro MCF-7 cell culture and in vivo tumor formation. Compared to cells cultured as 2D monolayers, the 3D-cultured cells presented 3D cell morphology, exhibited better cell viability, expressed higher levels of pro-angiogenic factors, and showed significantly greater migration and invasion abilities. The results from assay of tumorigenicity in nude mice and histologic analysis demonstrated the enhanced tumorigenic and angiogenic capabilities of the MCF-7 cells pre-cultured in pLysAAm hydrogels. These findings suggest that pLysAAm hydrogels may be used to bridge the gap between standard in vitro cell cultures and living tissues, aid breast cancer research, and help researchers to develop novel anticancer therapeutics.