Accelerated healing of full thickness dermal wounds by macroporous waterborne polyurethane-chitosan hydrogel scaffolds

A review of polysaccharide hydrogels as materials for skin repair and wound dressing: Construction, functionalization and challenges

Hydrogels can imitate the extracellular matrix, therefore facilitating the creation of an ideal healing environment for wounds. Consequently, they are popular as a material choice for wound dressings. Polysaccharides have been widely used in wound dressings due to their good biocompatibility and degradability. In this study, we first discuss skin and wound physiology before summarizing the methods for producing hydrogels from polysaccharides and their derivatized. These include not just normal polysaccharides like chitosan, cellulose, and alginate, but also Chinese medicinal polysaccharides with therapeutic properties. Then, strategies for causing hydrogel production from polysaccharides or their derivatives are briefly explained. Finally, the functions of hydrogel dressings are reviewed, including antibacterial, antioxidant, and adhesive properties, as well as the methods for achieving these properties. Furthermore, current issues and concerns are discussed, with the goal of providing fresh paths for the development of future wound dressings.

Recent Advances in Environment-Friendly Polyurethanes from Polyols Recovered from the Recycling and Renewable Resources: A Review

Polyurethane (PU) is among the most universal polymers and has been extensively applied in many fields, such as construction, machinery, furniture, clothing, textile, packaging and biomedicine. Traditionally, as the main starting materials for PU, polyols deeply depend on petroleum stock. From the perspective of recycling and environmental friendliness, advanced PU synthesis, using diversified resources as feedstocks, aims to develop versatile products with excellent properties to achieve the transformation from a fossil fuel-driven energy economy to renewable and sustainable ones. This review focuses on the recent development in the synthesis and modification of PU by extracting value-added monomers for polyols from waste polymers and natural bio-based polymers, such as the recycled waste polymers: polyethylene terephthalate (PET), PU and polycarbonate (PC); the biomaterials: vegetable oil, lignin, cashew nut shell liquid and plant straw; and biomacromolecules: polysaccharides and protein. To design these advanced polyurethane formulations, it is essential to understand the structure-property relationships of PU from recycling polyols. In a word, this bottom-up path provides a material recycling approach to PU design for printing and packaging, as well as biomedical, building and wearable electronics applications.

A review of the current state of natural biomaterials in wound healing applications

Skin, the largest biological organ, consists of three main parts: the epidermis, dermis, and subcutaneous tissue. Wounds are abnormal wounds in various forms, such as lacerations, burns, chronic wounds, diabetic wounds, acute wounds, and fractures. The wound healing process is dynamic, complex, and lengthy in four stages involving cells, macrophages, and growth factors. Wound dressing refers to a substance that covers the surface of a wound to prevent infection and secondary damage. Biomaterials applied in wound management have advanced significantly. Natural biomaterials are increasingly used due to their advantages including biomimicry of ECM, convenient accessibility, and involvement in native wound healing. However, there are still limitations such as low mechanical properties and expensive extraction methods. Therefore, their combination with synthetic biomaterials and/or adding bioactive agents has become an option for researchers in this field. In the present study, the stages of natural wound healing and the effect of biomaterials on its direction, type, and level will be investigated. Then, different types of polysaccharides and proteins were selected as desirable natural biomaterials, polymers as synthetic biomaterials with variable and suitable properties, and bioactive agents as effective additives. In the following, the structure of selected biomaterials, their extraction and production methods, their participation in wound healing, and quality control techniques of biomaterials-based wound dressings will be discussed.

Supramolecular hydrogels for wound repair and hemostasis

The unique network characteristics and stimuli responsiveness of supramolecular hydrogels have rendered them highly advantageous in the field of wound dressings, showcasing unprecedented potential. However, there are few reports on a comprehensive review of supramolecular hydrogel dressings for wound repair and hemostasis. This review first introduces the major cross-linking methods for supramolecular hydrogels, which includes hydrogen bonding, electrostatic interactions, hydrophobic interactions, host-guest interactions, metal ligand coordination and some other interactions. Then, we review the advanced materials reported in recent years and then summarize the basic principles of each cross-linking method. Next, we classify the network structures of supramolecular hydrogels before outlining their forming process and propose their potential future directions. Furthermore, we also discuss the raw materials, structural design principles, and material characteristics used to achieve the advanced functions of supramolecular hydrogels, such as antibacterial function, tissue adhesion, substance delivery, anti-inflammatory and antioxidant functions, cell behavior regulation, angiogenesis promotion, hemostasis and other innovative functions in recent years. Finally, the existing problems as well as future development directions of the cross-linking strategy, network design, and functions in wound repair and hemostasis of supramolecular hydrogels are discussed. This review is proposed to stimulate further exploration of supramolecular hydrogels on wound repair and hemostasis by researchers in the future.

Chitosan-sodium percarbonate-based hydrogels with sustained oxygen release potential stimulated angiogenesis and accelerated wound healing

The prolonged hypoxic conditions hinder chronic wounds from healing and lead to severe conditions such as delayed re-epithelialization and enhanced risk of infection. Multifunctional wound dressings are highly required to address the challenges of chronic wounds. Herein, we report polyurethane-coated sodium per carbonate-loaded chitosan hydrogel (CSPUO2 ) as a multifunctional dressing. The hydrogels (Control, CSPU, and CSPUO2 ) were prepared by freeze gelation method and the developed hydrogels showed high porosity, good absorption capacity, and adequate biodegradability. The release of oxygen from the CSPUO2 hydrogel was confirmed by the increase in pH and a sustained oxygen release was observed over the period of 21 days, due to polyurethane (CSPU) coating. The CSPUO2 hydrogel exhibited around 2-fold increased angiogenic potential in CAM assay when compared with Control and CSPU dressing. CSPUO2 also showed good level of antibacterial efficacy against E. coli and S. aureus. In a full-thickness rat wound model, CSPUO2 hydrogel considerably accelerated wound healing with exceptional re-epithelialization granulation tissue formation less inflammatory cells and improved skin architecture highlighting the tremendous therapeutic potential of this hydrogel when compared with control and CSPU to treat chronic diabetic and burn wounds.

Chitosan, alginate, hyaluronic acid and other novel multifunctional hydrogel dressings for wound healing: A review

Wound healing is a complex project, and effectively promoting skin repair is a huge clinical challenge. Hydrogels have great prospect in the field of wound dressings because their physical properties are very similar to those of living tissue and have excellent properties such as high water content, oxygen permeability and softness. However, the single performance of traditional hydrogels limits their application as wound dressings. Therefore, natural polymers such as chitosan, alginate and hyaluronic acid, which are non-toxic and biocompatible, are individually or combined with other polymer materials, and loaded with typical drugs, bioactive molecules or nanomaterials. Then, the development of novel multifunctional hydrogel dressings with good antibacterial, self-healing, injectable and multi-stimulation responsiveness by using advanced technologies such as 3D printing, electrospinning and stem cell therapy has become a hot topic of current research. This paper focuses on the functional properties of novel multifunctional hydrogel dressings such as chitosan, alginate and hyaluronic acid, which lays the foundation for the research of novel hydrogel dressings with better performance.

Hemostatic effect and safety evaluation of the absorbable macroporous polysaccharides composite hemostatic material prepared by a green fabrication approach

Carboxymethyl chitosan is widely used in the medical field such as wound healing and other medical fields. We previously fabricated the absorbable macroporous polysaccharides composite hemostatics (AMPCs) mainly composed of carboxymethyl chitosan which possess excellent hemostatic effect. To further elucidate the impact of CMCTs on the hemostatic effect and biosafety of AMPCs, carboxymethyl chitosan with different properties were used to prepare AMPCs. By comparing the physical and chemical properties, AMPCs performed high water absorption ability, especially Group 1 (swelling ratio reached 5792%), which facilitated the rapid formation of blood clots. It was confirmed by blood clotting index (BCI) and blood coagulation tests in vitro that Group 1 showed a slightly higher coagulation capacity than groups 2 and 3, which may be due to the positive charge on the surface of the cations in the salts attaches to the negative charge on the surface of the red blood cells, an electrostatic neutralization reaction occurs. The biosafety was a preliminary evaluation by implanted AMPCs into the back of Sprague-Dawley rats and the tissue was harvested after feeding for 28 days. The AMPCs exhibited good biosafety for whole blood and major organs during the degradation in vivo: during the degradation of AMPCs, excluding changes in some serum indicators, no tissue necrosis or inflammatory cell infiltration was observed in these organs, either by gross observation or histological analysis. These findings demonstrate that expecting to develop a highly functional and safe hemostatic agent based on Group 1 for rapid hemostasis applications in emergencies.

Biodegradable Sodium Alginate/Carrageenan/Cellulose Composite Hydrogel Wound Dressings Containing Herbal Extracts for Promoting Blood Coagulation and Wound Healing

Accelerating the coagulation process and preventing wound infection are major challenges in the wound care process. Therefore, new multifunctional wound dressings with procoagulant, antibacterial, and antioxidant properties have enormous potential for clinical application. In this work, biodegradable hydrogels containing herbal extracts are prepared for wound dressings. First, the active ingredients are extracted from Amaranthus spinosus (A. spinosus) and Rubia cordifolia (R. cordifolia) and added to the hydrogels prepared from microcrystalline cellulose (MCC), carrageenan, and sodium alginate. Then the composite hydrogels are air-dried to obtain the wound dressings. The wound dressings prepared in this work have good biocompatibility and moisture retention. The mechanical properties of the wound dressings are further improved with the addition of MCC. Besides, the wound dressings have excellent procoagulant, antibacterial, and antioxidant properties due to the presence of R. cordifolia extract. Overall, the most effective group of wound dressings with different ingredient formulations reduces clotting time by 75% and largely inhibits bacterial growth. The wound dressings perform well in the animal wound models to promote wound healing. These results indicate that the hydrogel wound dressings prepared in this work have great potential for medical applications.

Progress of Polysaccharide-Contained Polyurethanes for Biomedical Applications

Polyurethane (PU) has been widely examined and used for biomedical applications, such as catheters, blood oxygenators, stents, cardiac valves, drug delivery carriers, dialysis devices, wound dressings, adhesives, pacemaker, tissue engineering, and coatings for breast implants due to its mechanical flexibility, high tear strength, biocompatibility, and tailorable foams although bio-acceptability, biodegradability and controlled drug delivery to achieve the desired properties should be considered. Especially, during the last decade, the development of bio-based PUs has raised public awareness because of the concern with global plastic waste for creating more environmentally friended materials. Therefore, it is desirable to discuss polysaccharide (PS)-contained PU for the wound dressing and bone tissue engineering among bio-based PUs because PS has several advantages, such as biocompatibility, reproducibility from the natural resources, degradability, ease of incorporation of bioactive agents, ease of availability and cost-effectiveness, and structural feature of chemical modification to meet the desired needs to overcome the disadvantages of PU itself by containing the PS into the PU.

Insights into the Design of Polyurethane Dressings Suitable for the Stages of Skin Wound-Healing: A Systematic Review

Dressings made with polyurethanes have been found to exhibit good and varied biological properties that make them good candidates for this application. However, as has been seen, the wound-healing process is complex, which includes four different stages. So far, the design and evaluation of polyurethane for wound dressing has focused on achieving good properties (mechanical, physicochemical, and biological), but each of them separates from the others or even directed at only one of the stages of skin wound-healing. Therefore, the aim of this systematic review is to explore the applications of polyurethanes in wound dressings and to determine whether could be designed to cover more than one stage of skin wound-healing. The PRISMA guidelines were followed. The current research in this field does not consider each stage separately, and the design of polyurethane dressings is focused on covering all the stages of wound healing with a single material but is necessary to replace polyurethanes in short periods of time. Additionally, little emphasis is placed on the hemostasis stage and further characterization of polyurethanes is still needed to correlate mechanical and physicochemical properties with biological properties at each stage of the wound-healing. Current research demonstrates an effort to characterize the materials physiochemically and mechanically, but in terms of their biological properties, most of the literature is based on the performance of histological tests of explants morphologically probing the compromised tissues, which give an indication of the potential use of polyurethanes in the generation of wound-healing dressings.

Environment tolerant, adaptable and stretchable organohydrogels: preparation, optimization, and applications

Multiple stretchable materials have been successively developed and applied to wearable devices, soft robotics, and tissue engineering. Organohydrogels are currently being widely studied and formed by dispersing immiscible hydrophilic/hydrophobic polymer networks or only hydrophilic polymer networks in an organic/water solvent system. In particular, they can not only inherit and carry forward the merits of hydrogels, but also have some unique advantageous features, such as anti-freezing and water retention abilities, solvent resistance, adjustable surface wettability, and shape memory effect, which are conducive to the wide environmental adaptability and intelligent applications. This review first summarizes the structure, preparation strategy, and unique advantages of the reported organohydrogels. Furthermore, organohydrogels can be optimized for electro-mechanical properties or endowed with various functionalities by adding or modifying various functional components owing to their modifiability. Correspondingly, different optimization strategies, mechanisms, and advanced developments are described in detail, mainly involving the mechanical properties, conductivity, adhesion, self-healing properties, and antibacterial properties of organohydrogels. Moreover, the applications of organohydrogels in flexible sensors, energy storage devices, nanogenerators, and biomedicine have been summarized, confirming their unlimited potential in future development. Finally, the existing challenges and future prospects of organohydrogels are provided.

A review of wound dressing materials and its fabrication methods: emphasis on three-dimensional printed dressings

A wound is a trauma caused by some adverse external or blunt forces that can damage the body tissues. Wound healing is a complex process that occurs post-injury which involves the revamping of the structure and function of damaged tissues. Scaffolds are engineered tissue structures manufactured using different materials and methods for facilitating the wound healing process. For external wounds, the antimicrobial property and ability to absorb moisture play an important role in the material selection of the scaffold. Among different methods that exist for designing scaffolds, three-dimensional printing has emerged as a promising technique wherein customised scaffolds can be designed. However, the literature on three-dimensional printed dressings is very much limited compared to conventional ones. Therefore, this review specifically focuses on the methods used to design the scaffolds with special emphasis on different three-dimensional printing techniques. It covers the process of external wound healing, different materials used in the fabrication of scaffolds, and their advantages and drawbacks.

Raman spectroscopy assisted biochemical evaluation of L929 fibroblast cells on differentially crosslinked gelatin hydrogels

Biochemical evaluation of cell-matrix interaction using conventional labelling techniques often possesses limitations due to dye entrapment. In contrast, Raman spectroscopy guided approach offers label-free determination of cell-matrix biochemistry. Herein, gelatin (Gel) matrices modified with 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide/ N-Hydroxysuccinimide (EDC/NHS) and glutaraldehyde (GTA) was used as standards for comparative evaluation. Raman spectroscopy was deployed as a label-free approach to investigate interaction of cells with Gel hydrogels. Raman-based approach assisted in evaluation of cell-matrix interactions by identifying key biomolecular signatures retrospecting the fact that L929 fibroblast cells portrayed excellent growth and proliferation kinetics in crosslinked Gel as compared to its bare counterpart. EDC crosslinked hydrogels exhibited superior cell proliferation than its GTA counterparts. Cell proliferation on differentially crosslinked gel was also confirmed using standard MTT Assay and Rhodamine-DAPI staining thus corroborating the fact that Raman spectroscopy can be deployed as a superior label-free alternative towards real-time determination of cell proliferation and growth.

Designing of new hydrophilic polyurethane using the graft-polymerized poly(acrylic acid) and poly(2-(dimethylamino)ethyl acrylate)

Poly(acrylic acid) and poly(2-(dimethylamino)ethyl acrylate) chains were grafted to polyurethane (PU) using the graft-polymerization method in order to enhance the water compatibility of PU. The grafted chains were ionized into cationic or anionic form depending on the addition of strong acid or base. The grafted polymer chains did not affect the melting, crystallization, and glass transition of the soft segment of PU due to the softness of the chain. The cross-link density and solution viscosity increased due to the linking between the grafted chains, but the slight cross-linking did not disturb the solvation of PU. The slight cross-linking notably enhanced the maximum tensile stress and shape recovery capability, and the water compatibility of PU could be notably enhanced by the grafted ionized chains. Overall, the grafting of ionized polymeric chains onto PU could enhance the hydrophilicity of PU surface, tensile strength, and shape recovery capability.

Edible Materials in Tissue Regeneration

Edible materials have attracted increasing attention because of their excellent properties including availability, biocompatibility, biological activity, and biodegradability. Natural polysaccharides, phenolic compounds, and proteins are widely used in tissue regeneration. To better characterize their healing effect, this review article describes the applications of edible materials in tissue regeneration including wound healing and bone tissue regeneration. As an introduction to the topic, their sources and main bioactive properties are discussed. Then, the mechanism by which they facilitate wound healing based on their hemostasis, antibacterial, anti-inflammatory, and antioxidant properties is systematically investigated. Moreover, a more comprehensive discussion is presented on the approaches by which edible materials can be used as scaffolds or agents for the provision of the components of natural bones for regulating the level of osteogenesis-related cytokines to enhance bone repair. Finally, the prospects of edible materials for tissue regeneration are discussed.

Polymeric drug delivery systems by additive manufacturing

Additive manufacturing (AM) is gaining interests in drug delivery applications, offering innovative opportunities for the design and development of systems with complex geometry and programmed controlled release profile. In addition, polymer-based drug delivery systems can improve drug safety, efficacy, patient compliance, and are the key materials in AM. Therefore, combining AM and polymers can be beneficial to overcome the existing limitations in the development of controlled release drug delivery systems. Considering these advantages, here we are focusing on the recent developments in the field of polymeric drug delivery systems prepared by AM. This review provides a comprehensive overview on a holistic polymer-AM perspective for drug delivery systems with discussion on the materials, properties, design and fabrication techniques and the mechanisms used to achieve a controlled release system. The current challenges and future perspectives for personalized medicine and clinical use of these systems are also briefly discussed.

Bio-based polyurethane aqueous dispersions

With the advances of green chemistry and nanoscience, the synthesis of green, homogenous bio-based waterborne polyurethane (WPU) dispersions with high performance have gained great attention. The presented chapter deals with the recent synthesis of waterborne polyurethane with the biomass, especially the vegetable oils including castor oil, soybean oil, sunflower oil, linseed oil, jatropha oil, and palm oil, etc. Meanwhile, the other biomasses, such as cellulose, starch, lignin, chitosan, etc., have also been illustrated with the significant application in preparing polyurethane dispersions. The idea was to highlight the main vegetable oil-based polyols, and the isocyanate, diols as chain extenders, which have supplied a class of raw materials in WPU. The conversion of biomasses into active chemical agents, which can be used in synthesis of WPU, has been discussed in detail. The main mechanisms and methods are also presented. It is suggested that the epoxide ring opening method is still the main route to transform vegetable oils to polyols. Furthermore, the nonisocyanate WPU may be one of the main trends for development of WPU using biomasses, especially the abundant vegetable oils.

Gamma radiation-induced grafting of poly(2-aminoethyl methacrylate) onto chitosan: A comprehensive study of a polyurethane scaffold intended for skin tissue engineering

A novel brush-like poly(2-aminoethyl methacrylate) (PAEMA) was grafted onto chitosan (CS) through gamma radiation-induced polymerization. The copolymer (CS-g-PAEMA) was used to prepare a sodium acetate leached poly(urethane-urea) scaffold. The above derivatives were developed, synthesized, and characterized to meet the specific characteristics of biomaterials. The results revealed that this method is an easy and successful route for grafting PAEMA onto CS. The feasibility of preparing a CS-g-PAEMA polyurethane foam was confirmed by mechanical, morphometric, spectroscopic, and cytotoxic studies. The scaffold showed high biocompatibility both in vitro and in vivo. The first experiment proved that CS-based polyurethane efficiently allows the dynamic culturing of human fibroblast cells. Additionally, an in vivo study in a murine model indicated a complete integration of the scaffold to surrounding subcutaneous tissue as supported by the histological and histochemical assessments. The aforementioned results support the use of CS-g-PAEMA poly(saccharide-urethane) as a model of in vitro-engineered skin.

Recent advances on polymeric hydrogels as wound dressings

Severe hemorrhage is a leading cause of high mortality in critical situations like disaster, accidents, and warfare. The resulting wounds could induce severe physical and psychological trauma to patients and also bring an immense socio-economic burden. Hence, rapid hemostasis and wound healing techniques have become critical initiatives for life-saving treatment. Although traditional methods relying on bandages and gauzes are effective in controlling hemorrhage, they suffer from several limitations: nonbiodegradability, being susceptible to infection, being unsuitable for the irregular wound, secondary tissue damage, and being almost ineffective for wound healing. Owing to the merits of high porosity, good biocompatibility, tunable physicochemical properties, and being beneficial for wound healing, hydrogels with excellent performance have drawn intensive attention and numerous novel effective hydrogel dressings have been widely developed. In this Review, after introducing some commonly used strategies for the synthesis of hydrogels, the most recent progress on polymer-based hydrogels as wound dressings is discussed. Particularly, their hemostasis, antibacterial, and biodegradation properties are introduced. Finally, challenges and future perspectives about the development of hydrogels for wound dressings are outlined.

Advances in Waterborne Polyurethane and Polyurethane-Urea Dispersions and Their Eco-friendly Derivatives: A Review

Polyurethanes and polyurethane-ureas, particularly their water-based dispersions, have gained relevance as an extremely versatile area based on environmentally friendly approaches. The evolution of their synthesis methods, and the nature of the reactants (or compounds involved in the process) towards increasingly sustainable pathways, has positioned these dispersions as a relevant and essential product for diverse application frameworks. Therefore, in this work, it is intended to show the progress in the field of polyurethane and polyurethane-urea dispersions over decades, since their initial synthesis approaches. Thus, the review covers from the basic concepts of polyurethane chemistry to the evolution of the dispersion's preparation strategies. Moreover, an analysis of the recent trends of using renewable reactants and enhanced green strategies, including the current legislation, directed to limit the toxicity and potentiate the sustainability of dispersions, is described. The review also highlights the strengths of the dispersions added with diverse renewable additives, namely, cellulose, starch or chitosan, providing some noteworthy results. Similarly, dispersion's potential to be processed by diverse methods is shown, evidencing, with different examples, their suitability in a variety of scenarios, outstanding their versatility even for high requirement applications.

Tough and biodegradable polyurethane-curcumin composited hydrogel with antioxidant, antibacterial and antitumor properties

The functionalization of tough and biodegradable hydrogels is an important way to broaden their applications in biomedical field. However, most of the hydrophobic functional drugs are difficult to incorporate with the hydrogels. In this work, curcumin (Cur), a hydrophobic functional drug, was chosen to composite with polyurethane (PU) to obtain PU-Cur hydrogels by a direct and simple in-situ copolymerization. The incorporation of curcumin in PU hydrogel increases the crosslink but reduces the hydrophilicity and degradation rate of PU-Cur hydrogels. Thus, it can increase the mechanical strength to a maximum of 6.4±0.8 MPa and initial modulus to a maximum of 3.0±0.4 MPa. More importantly, curcumin incorporated in PU networks is not deactivated. The degradation products of PU-Curs at relatively low concentrations (2.5 mg/mL) can scavenge free radicals very efficiently (maximum over 90%), which exhibits strong antioxidant properties to improve wound healing. Moreover, based on the photochemical activity of curcumin, notable inhibition effects of the degradation products of PU-Curs against bacteria (maximum over 80%) and cancer cells are demonstrated with blue light treatment as a photodynamic therapy (PDT). Therefore, the beneficial effects of curcumin are retained in PU-Cur hydrogels, suggesting potential use as wound dressings or tumor isolation membranes. This work proposes a promising strategy to combine hydrophobic functional drugs with hydrophilic hydrogels for applications in a wide range of biomaterials.

Synthesis of Water Resistance and Moisture-Permeable Nanofiber Using Sodium Alginate-Functionalized Waterborne Polyurethane

The development of nontoxic and biodegradable alginate-based materials has been a continual goal in biological applications. However, their hydrophilic nature and lack of spinnability impart water instability and poor mechanical strength to the nanofiber. To overcome these limitations, sodium alginate (SA) and waterborne polyurethane (WPU) were blended and crosslinked with calcium chloride; 30 wt % of SA exhibited good compatibility. Further addition of 10 wt % calcium chloride improved the water stability to an extremely humid region. Furthermore, the stress-strain curve revealed that the initial modulus and the elongation strength of the WPU/SA and WPU/CA blends increased with SA content, and the crosslinker concentration clearly indicated the dressing material hardness resulted from this simple blend strategy. The WPU/SA30 electrospun nanofibrous blend contained porous membranes; it exhibited good mechanical strength with water-stable, water-absorbable (37.5 wt %), and moisture-permeable (25.1 g/m2-24 h) characteristics, suggesting our cost-effective material could function as an effective wound dressing material.

Enzymatic Extraction of Bioactive and Self-Assembling Wool Keratin for Biomedical Applications

Keratin is widely recognized as a high-quality renewable protein resource for biomedical applications. Despite their extensive existence, keratin resources such as feathers, wool, and hair exhibit high stability and mechanical properties because of their high disulfide bond content. Consequently, keratin extraction is challenging and its application is greatly hindered. In this work, a biological extraction strategy is proposed for the preparation of bioactive keratin and the fabrication of self-assembled keratin hydrogels (KHs). Based on moderate and controlled hydrolysis by keratinase, keratin with a high molecular weight of approximately 45 and 28 kDa that retain its intrinsic bioactivities is obtained. The keratin products show excellent ability to promote cell growth and migration and are conferred with significant antioxidant ability because of their intrinsically high cysteine content. In addition, without the presence of any cross-linking agent, the extracted keratin can self-assemble into injectable hydrogels. The KHs exhibit a porous network structure and 3D culture ability, showing potential in promoting wound healing. This enzyme-driven keratin extraction strategy opens up a new approach for the preparation of keratin that can self-assemble into injectable hydrogels for biomedical engineering.

Bioinspired 3D porous human placental derived extracellular matrix/silk fibroin sponges for accelerated bone regeneration

Critical bone defects arising from traumatic injury and diseases are of major health concern since they are unable to heal spontaneously without clinical intervention. In this context, bone tissue engineering provides an attractive approach to treat bone defects by providing a bioactive template which has the potential to guide osseous tissue regeneration. In this study, porous hybrid placental extracellular matrix sponge (PIMS) was fabricated by a combinatorial method using silk fibroin (SF)/placental derived extracellular matrix and subsequently evaluated its efficacy towards bone tissue regeneration. The presence of intrinsic growth factors was evidenced by immunoblotting of the extracted proteins derived from the placental derived extracellular matrix. This growth factor rich PIMS lends a unique bioactive scaffolding to human amniotic mesenchymal stem cells (HAMSCs) which supported enhanced proliferation as well as superior osteogenic differentiation. Gene expression studies demonstrated significant up-regulation of osteogenic related genes in the PIMS group. PIMS when implanted in the chick chorioallantoic membrane, significantly attracted allantoic vessels revealing its potential to stimulate angiogenesis ex vivo. Furthermore, no severe immune response to the host was observed on subcutaneous implantation of PIMS in vivo. Instead, it supported the formation of blood vessels, revealing its outstanding biocompatibility. Additionally, critical tibial defects treated with PIMS demonstrated higher bone volume after six weeks when analyzed by micro-CT, which was accompanied by high mineral density. Histological and immunofluorescence studies validated the results and revealed enhanced osseous tissue regeneration after six weeks of surgery. All these findings recapitulated that the growth factors incorporated bioactive PIMS could perform as an appropriate matrix for osteogenic differentiation and efficient bone regeneration.

Osteochondral and bone tissue engineering scaffold prepared from Gallus var domesticus derived demineralized bone powder combined with gellan gum for medical application

Osteochondral (OC) lesions can occur in the knee and ankle. Such lesions induce a fracture in the cartilage protecting the bone joints. Cartilage tissue shows limited self-regeneration ability, hence the tissue is avascular and lack of vascular innervation, while the bone is a unique organ with the capacity to self-repair of small defects. In this present study, we have prepared a scaffold using demineralized bone powder (DBP) extracted from Gallus gallus var domesticus (GD), and Gellan gum (GG) for OC tissue regeneration. They were characterized for their chemical, physical, mechanical and biological properties using different available techniques, in vitro bioactivity was performed in simulated body fluid for 14 days confirming the formation of bone-like apatite. The in vitro biocompatibility was analyzed using chondrocyte cells and osteogenic and chondrogenic marker gene expression using RT-PCR, in vivo experiments performed by implanting scaffold in rabbit and characterized by histology and immunofluorescent stainings. The obtained results indicated that the prepared pores scaffold was biocompatible, and promote OC regeneration and integration of newly formed tissues with the host tissues in a rabbit. The prepared 1% DBP/GG scaffold can be used as a potential and promising alternate material for OC regeneration.

Hydrogel Dressings for Advanced Wound Management

BACKGROUND

Composed in a large extent of water and due to their nonadhesiveness, hydrogels found their way to the wound dressing market as materials that provide a moisture environment for healing while being comfortable to the patient. Hydrogels' exploitation is constantly increasing after evidences of their even broader therapeutic potential due to resemblance to dermal tissue and ability to induce partial skin regeneration. The innovation in advanced wound care is further directed to the development of so-called active dressings, where hydrogels are combined with components that enhance the primary purpose of providing a beneficial environment for wound healing.

OBJECTIVE

The objective of this review is to concisely describe the relevance of hydrogel dressings as platforms for delivery of active molecules for improved management of difficult- to-treat wounds. The emphasis is on the most recent advances in development of stimuli- responsive hydrogels, which allow for control over wound healing efficiency in response to different external modalities. Novel strategies for monitoring of the wound status and healing progress based on incorporation of sensor molecules into the hydrogel platforms are also discussed.

Waterborne poly(urethane-urea)s films as a sustained release system for ketoconazole

Ketoconazole (KTZ) was incorporated in waterborne poly(urethane-urea)s dispersions (WPUU), aiming at the production of films for drug sustained release. Dispersions based on poly(ethylene glycol-block-propylene glycol) (PEG-b-PPG) (four monomers with different contents of PEG hydrophilic segments), poly(propylene glycol), isophorone diisocyanate, dime-thylolpropionic acid and hydrazine were produced and characterized by apparent viscosity and average particle size (APS). Cast films-drug interaction was investigated by Fourier-Transform infrared spectrometry (FTIR). In vitro dissolution assays were performed in simulated gastrointestinal juices, followed by application of kinetic models. Stable pseudoplastic dispersions, with APS between 27 to 320 nm were obtained. FTIR from KTZ-loaded films indicated interactions between polymer and drug. In vitro release of KTZ was achieved above 80%, notably influenced by PEG-based segments content up to 2 h, followed by sustained release for 8 h. Higuchi’s and first-order equations described the drug kinetic profile, as diffusion of the drug and erosion of the swollen polymer, respectively.

Pharmaceutical applications of chitosan

Chitosan (CS) is a linear polysaccharide which is achieved by deacetylation of chitin, which is the second most plentiful compound in nature, after cellulose. It is a linear copolymer of β-(1 → 4)-linked 2-acetamido-2-deoxy-β-d-glucopyranose and 2-amino-2-deoxy-β-d-glucopyranose. It has appreciated properties such as biocompatibility, biodegradability, hydrophilicity, nontoxicity, high bioavailability, simplicity of modification, favorable permselectivity of water, outstanding chemical resistance, capability to form films, gels, nanoparticles, microparticles and beads as well as affinity to metals, proteins and dyes. Also, the biodegradable CS is broken down in the human body to safe compounds (amino sugars) which are easily absorbed. At present, CS and its derivatives are broadly investigated in numerous pharmaceutical and medical applications including drug/gene delivery, wound dressings, implants, contact lenses, tissue engineering and cell encapsulation. Besides, CS has several OH and NH₂ functional groups which allow protein binding. CS with a deacetylation degree of ~50% is soluble in aqueous acidic environment. While CS is dissolved in acidic medium, its amino groups in the polymeric chains are protonated and it becomes cationic which allows its strong interaction with different kinds of molecules. It is believed that this positive charge is responsible for the antimicrobial activity of CS through the interaction with the negatively charged cell membranes of microorganisms. This review presents properties and numerous applications of chitosan-based compounds in drug delivery, gene delivery, cell encapsulation, protein binding, tissue engineering, preparation of implants and contact lenses, wound healing, bioimaging, antimicrobial food additives, antibacterial food packaging materials and antibacterial textiles. Moreover, some recent molecular dynamics simulations accomplished on the pharmaceutical applications of chitosan were presented.

Preparation of Lauroyl Grafted Alginate-Psyllium Husk Gel Composite Film with Enhanced Physicochemical, Mechanical and Antimicrobial Properties

In this study, a lauroyl grafted hydrophobic glycolipid derivative of alginate has been successfully synthesized and characterized. This glycolipid has been incorporated into Psyllium husk gel-alginate composite films and compared with the films containing only Psyllim husk gel and Psyllim husk gel-alginate for its mechanical and physicochemical properties. Additionally, the composite film has also been evaluated for protein adsorption and antimicrobial property to verify its utility in biomedical applications. The results showed that the composite films have enhanced physicochemical and mechanical properties. The film produced better swelling characteristic and lower protein adsorption property indicating the usefulness of the film in wound care dressing, particularly for low suppurating wounds. Incorporation of the synthesised glycolipid derivative also imparts antimicrobial activity to the composite film. Therefore, the developed film is capable of sustaining the microbial contamination during the storage and also valuable in the biomedical utility including wound dressings.

Characterization and Evaluation of Carboxymethyl Cellulose-Based Films for Healing of Full-Thickness Wounds in Normal and Diabetic Rats

Artificial skin substitute made of polymeric films are of great demand in the field of skin tissue engineering. We report here the fabrication of carboxymethyl cellulose (CMC) and poly(ethylene glycol) (PEG) blend films by solution casting method for wound healing applications. The physicochemical characteristics and the thermal stability of the films were analyzed. The surface morphology shows crystalline structures with large hexagonal-like platelet crystals of CMC on the surface of the films. Pure CMC films exhibited higher tensile strength than the CMC/PEG blend films. The swelling ratio (SR) of the films was influenced by the pH of Tris-HCL buffer (2.0, 5.0, and 7.0), which increased with increase in pH. The hemocompatibility assay and cytotoxicity test using NIH 3T3 fibroblast cells showed that the films were biocompatible. To evaluate the wound healing efficacy, the films were applied in full-thickness wounds created in normal and diabetic Wistar albino rats. The wounds healed faster with pure CMC film compared to blend films in both normal and diabetic rats, evidenced by intensive collagen formation in histopathological analysis. Thus, the films have potential application in skin regeneration, thereby to restore the structural and functional characteristics of the skin.

Advances in Waterborne Polyurethane-Based Biomaterials for Biomedical Applications

Polyurethane (PU) is one of the most popular synthetic elastomers and widely employed in biomedical fields owing to the excellent biocompatibility and hemocompatibility known today. In addition, PU is simply prepared and its mechanical properties such as durability, elasticity, elastomer-like character, fatigue resistance, compliance or tolerance in the body during the healing, can be mediated by modifying the chemical structure. Furthermore, modification of bulk and surface by incorporating biomolecules such as anticoagulant s or biorecognizable groups, or hydrophilic/hydrophobic balance is possible through altering chemical groups for PU structure. Such modifications have been designed to improve the acceptance of implant. For these reason, conventional solventborne (solvent-based) PUs have established the standard for high performance systems, and extensively used in medical devices such as dressings, tubing, antibacterial membrane , catheters to total artificial heart and blood contacting materials, etc. However, waterborne polyurethane (WPU) has been developed to improve the process of dissolving PU materials using toxic organic solvents, in which water is used as a dispersing solvent. The prepared WPU materials have many advantages, briefly (1) zero or very low levels of organic solvents, namely environmental-friendly (2) non-toxic, due to absence of isocyanate residues, and (3) good applicability caused by extensive structure/property diversity as well as an environment-friendly fabrication method resulting in increasing applicability. Therefore, WPUs are being in the spotlight as biomaterials used for biomedical applications . The purpose of this review is to introduce an environmental- friendly synthesis of WPU and consider the manufacturing process and application of WPU and/or WPU based nanocomposites as the viewpoint of biomaterials.