Functionally modified gelatin microspheres impregnated collagen scaffold as novel wound dressing to attenuate the proteases and bacterial growth

Human Mesenchymal Stem Cells on Size-Sorted Gelatin Hydrogel Microparticles Show Enhanced In Vitro Wound Healing Activities

The demand for innovative therapeutic interventions to expedite wound healing, particularly in vulnerable populations such as aging and diabetic patients, has prompted the exploration of novel strategies. Mesenchymal stem cell (MSC)-based therapy emerges as a promising avenue for treating acute and chronic wounds. However, its clinical application faces persistent challenges, notably the low survivability and limited retention time of engraftment in wound environments. Addressing this, a strategy to sustain the viability and functionality of human MSCs (hMSCs) in a graft-able format has been identified as crucial for advanced wound care. Hydrogel microparticles (HMPs) emerge as promising entities in the field of wound healing, showcasing versatile capabilities in delivering both cells and bioactive molecules/drugs. In this study, gelatin HMPs (GelMPs) were synthesized via an optimized mild processing method. GelMPs with distinct diameter sizes were sorted and characterized. The growth of hMSCs on GelMPs with various sizes was evaluated. The release of wound healing promoting factors from hMSCs cultured on different GelMPs were assessed using scratch wound assays and gene expression analysis. GelMPs with a size smaller than 100 microns supported better cell growth and cell migration compared to larger sizes (100 microns or 200 microns). While encapsulation of hMSCs in hydrogels has been a common route for delivering viable hMSCs, we hypothesized that hMSCs cultured on GelMPs are more robust than those encapsulated in hydrogels. To test this hypothesis, hMSCs were cultured on GelMPs or in the cross-linked methacrylated gelatin hydrogel (GelMA). Comparative analysis of growth and wound healing effects revealed that hMSCs cultured on GelMPs exhibited higher viability and released more wound healing activities in vitro. This observation highlights the potential of GelMPs, especially those with a size smaller than 100 microns, as a promising carrier for delivering hMSCs in wound healing applications, providing valuable insights for the optimization of advanced therapeutic strategies.

Formulation and Comprehensive Evaluation of Biohybrid Hydrogel Membranes Containing Doxycycline or Silver Nanoparticles

Complicated wounds often require specialized medical treatments, and hydrogels have emerged as a popular choice for wound dressings in such cases due to their unique properties and the ability to incorporate and release therapeutic agents. Our focus was to develop and characterize a new optimized formula for biohybrid hydrogel membranes, which combine natural and synthetic polymers, bioactive natural compounds, like collagen and hyaluronic acid, and pharmacologically active substances (doxycycline or npAg). Dynamic (oscillatory) rheometry confirmed the strong gel-like properties of the obtained hydrogel membranes. Samples containing low-dose DOXY showed a swelling index of 285.68 ± 6.99%, a degradation rate of 71.6 ± 0.91% at 20 h, and achieved a cumulative drug release of approximately 90% at pH 7.4 and 80% at pH 8.3 within 12 h. The addition of npAg influenced the physical properties of the hydrogel membranes. Furthermore, the samples containing DOXY demonstrated exceptional antimicrobial efficacy against seven selected bacterial strains commonly associated with wound infections and complications. Biocompatibility assessments revealed that the samples exhibited over 80% cell viability. However, the addition of smaller-sized nanoparticles led to decreased cellular viability. The obtained biohybrid hydrogel membranes show favorable properties that render them suitable for application as wound dressings.

Microwave-Treated Physically Cross-Linked Sodium Alginate and Sodium Carboxymethyl Cellulose Blend Polymer Film for Open Incision Wound Healing in Diabetic Animals-A Novel Perspective for Skin Tissue Regeneration Application

This study aimed at developing the microwave-treated, physically cross-linked polymer blend film, optimizing the microwave treatment time, and testing for physicochemical attributes and wound healing potential in diabetic animals. Microwave-treated and untreated films were prepared by the solution casting method and characterized for various attributes required by a wound healing platform. The optimized formulation was tested for skin regeneration potential in the diabetes-induced open-incision animal model. The results indicated that the optimized polymer film formulation (MB-3) has significantly enhanced physicochemical properties such as high moisture adsorption (154.6 ± 4.23%), decreased the water vapor transmission rate (WVTR) value of (53.0 ± 2.8 g/m²/h) and water vapor permeability (WVP) value (1.74 ± 0.08 g mm/h/m²), delayed erosion (18.69 ± 4.74%), high water uptake, smooth and homogenous surface morphology, higher tensile strength (56.84 ± 1.19 MPa), and increased glass transition temperature and enthalpy (through polymer hydrophilic functional groups depicting efficient cross-linking). The in vivo data on day 16 of post-wounding indicated that the wound healing occurred faster with significantly increased percent re-epithelialization and enhanced collagen deposition with optimized MB-3 film application compared with the untreated group. The study concluded that the microwave-treated polymer blend films have sufficiently enhanced physical properties, making them an effective candidate for ameliorating the diabetic wound healing process and hastening skin tissue regeneration.

Review: Multimodal bioactive material approaches for wound healing

Wound healing is a highly complex process of tissue repair that relies on the synergistic effect of a number of different cells, cytokines, enzymes, and growth factors. A deregulation in this process can lead to the formation of a non-healing chronic ulcer. Current treatment options, such as collagen wound dressings, are unable to meet the demand set by the wound environment. Therefore, a multifaceted bioactive dressing is needed to elicit a targeted affect. Wound healing strategies seek to develop a targeted effect through the delivery of a bioactive molecule to the wound by a hydrogel or a polymeric scaffold. This review examines current biomaterial and small molecule-based approaches that seek to develop a bioactive material for targeted wound therapy and accepted wound healing models for testing material efficacy.

Collagen/Gelatin/Hydroxyethyl Cellulose Composites Containing Microspheres Based on Collagen and Gelatin: Design and Evaluation

The objective of this study was to develop three-dimensional collagen/gelatin/hydroxyethyl cellulose composites in combination with gelatin or collagen-gelatin loaded microspheres. Microspheres were prepared by an emulsification/crosslinking method. A 1-Ethyl-3-(3-dimethyl-aminopropyl)-carbodiimide (EDC) and N-hydroxysuccinimide (NHS) mixture were used as a crosslinking agent for the obtained materials. The structure of the materials was studied using scanning electron microscopy (SEM) and infrared spectroscopy. Moreover, a Calendula officinalis (pot marigold) flower extract release profile of the microsphere-loaded matrices was assessed in vitro. Additionally, porosity, density, stability, swelling and mechanical properties were tested. On the basis of SEM images, the microspheres exhibited a spherical shape and were irregularly dispersed in the polymer matrix. However, it was found that the addition of microparticles to obtained materials did not significantly change their microstructure. We observed a slight decrease in the swelling properties of matrices and an increase in values of Young's modulus. Significantly, the addition of microspheres to the polymer matrices led to improved loading capacity of materials and release performance of Calendula officinalis flower extract. This makes the collagen/gelatin/hydroxyethyl cellulose composites containing microspheres a promising and suitable vehicle for biomedical, dermatological, or cosmetic applications.

Advances in Protein-Based Materials: From Origin to Novel Biomaterials

Biomaterials play a very important role in biomedicine and tissue engineering where they directly affect the cellular activities and their microenvironment . Myriad of techniques have been employed to fabricate a vast number natural, artificial and recombinant polymer s in order to harness these biomaterials in tissue regene ration , drug delivery and various other applications. Despite of tremendous efforts made in this field during last few decades, advanced and new generation biomaterials are still lacking. Protein based biomaterials have emerged as an attractive alternatives due to their intrinsic properties like cell to cell interaction , structural support and cellular communications. Several protein based biomaterials like, collagen , keratin , elastin , silk protein and more recently recombinant protein s are being utilized in a number of biomedical and biotechnological processes. These protein-based biomaterials have enormous capabilities, which can completely revolutionize the biomaterial world. In this review, we address an up-to date review on the novel, protein-based biomaterials used for biomedical field including tissue engineering, medical science, regenerative medicine as well as drug delivery. Further, we have also emphasized the novel fabrication techniques associated with protein-based materials and implication of these biomaterials in the domain of biomedical engineering .

Drug delivery systems for wound healing

Protein, gene, and small molecule therapies hold great potential for facilitating comprehensive tissue repair and regeneration. However, their clinical value will rely on effective delivery systems which maximize their therapeutic benefit. Significant advances have been made in recent years towards biomaterial delivery systems to satisfy this clinical need. Here we summarize the most outstanding advances in drug delivery technology for cutaneous wound healing.

Recent developments in novel drug delivery systems for wound healing

INTRODUCTION

Complete regeneration and restoration of the skin's structure and function with no or minimal scarring remains the goal of wound healing research. Novel pharmaceutical carriers have the potential to deliver wound healing drugs such as antibiotics, antimicrobials, human EGFs, and so on. Thus, offering a potential platform to overcome the limitations of conventional wound dressings.

AREAS COVERED

This review will describe various techniques such as microspheres, nanoparticles, liposomes, solid lipid nanoparticles, nano and microemulsions, sponges and wafers, and so on, that are successfully applied as carriers for wound healing drugs. Results of various studies including in vitro and in vivo experiments are also discussed.

EXPERT OPINION

Controlled and localized delivery of wound healing drugs to the wounds is more convenient than systemic administration as higher concentrations of the medication are delivered directly to the desired area in a sustained manner. They are also capable of providing optimum environmental conditions to facilitate wound healing while eliminating the need for frequent changes of dressings. As the number of people suffering from chronic wounds is increasing around the world, controlled delivery of wound healing agents have enormous potential for patient-friendly wound management.

Multi-scale mechanical characterization of highly swollen photo-activated collagen hydrogels

Biological hydrogels have been increasingly sought after as wound dressings or scaffolds for regenerative medicine, owing to their inherent biofunctionality in biological environments. Especially in moist wound healing, the ideal material should absorb large amounts of wound exudate while remaining mechanically competent in situ. Despite their large hydration, however, current biological hydrogels still leave much to be desired in terms of mechanical properties in physiological conditions. To address this challenge, a multi-scale approach is presented for the synthetic design of cyto-compatible collagen hydrogels with tunable mechanical properties (from the nano- up to the macro-scale), uniquely high swelling ratios and retained (more than 70%) triple helical features. Type I collagen was covalently functionalized with three different monomers, i.e. 4-vinylbenzyl chloride, glycidyl methacrylate and methacrylic anhydride, respectively. Backbone rigidity, hydrogen-bonding capability and degree of functionalization (F: 16 ± 12–91 ± 7 mol%) of introduced moieties governed the structure–property relationships in resulting collagen networks, so that the swelling ratio (SR: 707 ± 51–1996 ± 182 wt%), bulk compressive modulus (E_c: 30 ± 7–168 ± 40 kPa) and atomic force microscopy elastic modulus (E_AFM: 16 ± 2–387 ± 66 kPa) were readily adjusted. Because of their remarkably high swelling and mechanical properties, these tunable collagen hydrogels may be further exploited for the design of advanced dressings for chronic wound care.

Microstructure, rheological and wound healing properties of collagen-based gel from cuttlefish skin

Collagen-based biomaterials are of the utmost importance for tissue engineering and regenerative medicine. The aims of the present investigation were to evaluate structural and rheological properties of collagen-based gel obtained from cuttlefish skin, and to investigate its ability to enhance wound healing. Scanning electron microscopy of resulted gel showed a dense fibrillar microstructure with high interconnection network with a smaller pore size. In addition, the rheological characterization of collagen gel showed an excellent reversibility, when subjected to a temperature variation. Moreover, in the wound-healing study, topical application of collagen based gel increased significantly the percentage of wound closure over a period of 12 days, when compared to the untreated and CICAFLORA(®)-treated groups. Wound-healing activity of collagen gel was confirmed by histopathology study. Thus, cuttlefish collagen based gel might be useful as a wound healing agent.

Effective release of a broad spectrum antibiotic from elastin-like polypeptide-collagen composite

Preparation of hydrogels that possess an effective antibiotic release profile and better mechanical properties compared to the traditionally used collagen hydrogels has the potential to minimize post-surgical infections and support wound healing. Toward this goal, we prepared elastin-like polypeptide (ELP)-collagen composite hydrogels that displayed a significantly higher elastic modulus compared to the collagen hydrogels. We then characterized the release behavior of the collagen and ELP-collagen hydrogels loaded with varying dosages (1-5% w/w) of a commonly used broad spectrum antibiotic, doxycycline hyclate. Both collagen and ELP-collagen hydrogels showed a gradual time dependent doxycycline release over a period of 5 days. The ELP-collagen hydrogels, in general, showed a slower release of the doxycycline compared to the collagen hydrogels. The released doxycycline was found to be effective against four bacterial strains (Escherichia coli, Pseudomonas aeruginosa, Streptococcus sanguinis, and methicillin-resistant Staphylococcus aureus) in a dose dependent manner. Combined with their improved mechanical properties, the gradual and effective drug release from the biocompatible ELP-collagen hydrogels shown here may be beneficial for drug delivery and tissue engineering applications.

Proteases and Delayed Wound Healing

SIGNIFICANCE

Proteases and their inhibitors contribute to the balance between extracellular matrix (ECM) degradation and deposition, creating an equilibrium that is essential for the timely and coordinated healing of cutaneous wounds. However, when this balance is disrupted, wounds are led into a state of chronicity characterized by abundant levels of proteases and decreased levels of protease inhibitors.

RECENT ADVANCES

Researchers have sought to investigate the roles of proteases within both acute and chronic wounds and how the manipulation of protease activity may aid healing. Indeed, numerous wound dressings have been developed that target such proteases in an attempt to promote wound healing.

CRITICAL ISSUES

The normal tissue response to injury involves a complex interaction between cells and cellular mediators. In particular, the inflammatory response is augmented in chronic wounds which are characterized by elevated levels of proinflammatory cytokines and proteases. While controlling levels of inflammation and protease expression is a critical part of normal wound healing, elevated and prolonged expression of proteases produced during the inflammatory phase of healing can lead to excessive ECM degradation associated with impaired healing.

FUTURE DIRECTIONS

It seems plausible that future research should aim to investigate the ways in which proteases may be targeted as an alternative therapeutic approach to wound management and to assess the benefits and draw-backs of utilizing wound fluids to assess wound progression in terms of proteolytic activity.

Current trends in the development of wound dressings, biomaterials and devices

Wound management covers all aspects of patient care from initial injury, treatment of infection, fluid loss, tissue regeneration, wound closure to final scar formation and remodeling. There are many wound-care products available including simple protective layers, hydrogels, metal ion-impregnated dressings and artificial skin substitutes, which facilitate surface closure. This review examines recent developments in wound dressings, biomaterials and devices. Particular attention is focused on the design and manufacture of hydrogel-based dressings, their polymeric constituents and chemical modification. Finally, topical negative pressure and hyperbaric oxygen therapy are considered. Current wound-management strategies can be expensive, time consuming and labor intensive. Progress in the multidisciplinary arena of wound care will address these issues and be of immense benefit to patients, by improving both clinical outcomes and their quality of life.

Synthesis and characterization of hybrid hyaluronic acid-gelatin hydrogels

Biomimetic hybrid hydrogels have generated broad interest in tissue engineering and regenerative medicine. Hyaluronic acid (HA) and gelatin (hydrolyzed collagen) are naturally derived polymers and biodegradable under physiological conditions. Moreover, collagen and HA are major components of the extracellular matrix (ECM) in most of the tissues (e.g., cardiovascular, cartilage, neural). When used as a hybrid material, HA-gelatin hydrogels may enable mimicking the ECM of native tissues. Although HA-gelatin hybrid hydrogels are promising biomimetic substrates, their material properties have not been thoroughly characterized in the literature. Herein, we generated hybrid hydrogels with tunable physical and biological properties by using different concentrations of HA and gelatin. The physical properties of the fabricated hydrogels including swelling ratio, degradation, and mechanical properties were investigated. In addition, in vitro cellular responses in both two and three-dimensional culture conditions were assessed. It was found that the addition of gelatin methacrylate (GelMA) into HA methacrylate (HAMA) promoted cell spreading in the hybrid hydogels. Moreover, the hybrid hydrogels showed significantly improved mechanical properties compared to their single component analogs. The HAMA-GelMA hydrogels exhibited remarkable tunability behavior and may be useful for cardiovascular tissue engineering applications.

Improved fibronectin-immobilized fibrinogen microthreads for the attachment and proliferation of fibroblasts

The aim of this study was to fabricate fibrinogen (Fbg) microfibers with different structural characteristics for the development of 3-D tissue-engineering scaffolds. Fabricated Fbg microfibers were investigated for their biomolecule encapsulation, cell adhesion, and proliferations. Microfibers with three different concentrations of Fbg (5, 10, and 15 wt%) were prepared by a gel solvent-extraction method using a silicone rubber tube. Fbg microfibers were covalently modified with fibronectin (FN) by using water-soluble 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide as the cross-linking agent. Fbg microfibers were characterized by their FN cross-linking properties, structural morphology, and in vitro degradation. Furthermore, FN/Fbg microfibers were evaluated for cell attachment and proliferation. The bio-compatibility and cell proliferation of the microfibers were assessed by measuring adenosine triphosphate activity in C2C12 fibroblast cells. Cell attachment and proliferation on microfibers were further examined using fluorescence and scanning electron microscopic images. FN loading on the microfibers was confirmed by fluorescence and infrared spectroscopy. Surface morphology was characterized by scanning electron microscopy, and showed highly aligned nanostructures for fibers made with 15 wt% Fbg, a more porous structure for fibers made with 10 wt% Fbg, and a less porous structure for those made with 5 wt% Fbg. Controlled biodegradation of the fiber was observed for 8 weeks by using an in vitro proteolytic degradation assay. Fbg microfibers with highly aligned nanostructures (15 wt%) showed enhanced biomolecule encapsulation, as well as higher cell adhesion and proliferation than another two types of FN/Fbg fibers (5 and 10 wt%) and unmodified Fbg fibers. The promising results obtained from the present study reveal that optimal structure of Fbg microfibers could be used as a potential substratum for growth factors or drug release, especially in wound healing and vascular tissue engineering, in which fibers could be applied to promote and orient cell adhesion and proliferation.

Preparation and evaluation of mesalamine collagen in situ rectal gel: a novel therapeutic approach for treating ulcerative colitis

Ulcerative colitis (UC) is a chronic inflammatory disease that primarily affects the colonic mucosa. Mesalamine had been established as a first line drug for treating mild to moderate UC. A continued availability of the drug for treatment of damaged tissues remains a great challenge today. In the present study, a novel mesalamine collagen in situ gel has been prepared using type I collagen, which is pH/temperature sensitive. This hydrogel undergoes sol-gel transition under physiological pH and temperature which was confirmed by rheological studies. The in vitro release profile demonstrated sustained release of mesalamine over a period of 12h. The in vivo efficacy of the in situ gel was performed using dextran sodium sulphate induced ulcerative colitis model in BALB/c mice. The clinical parameters such as, body weight changes, rectal bleeding and stool consistency were evaluated. In addition, the histopathological investigation was conducted to assess severity of mucosal damage and inflammation infiltrate. There was a significant reduction in rectal bleeding and mucosal damage score for collagen-mesalamine in situ gel group compared to the reference group. Apart from releasing mesalamine in controlled manner, the strategy of administering mesalamine through collagen in situ gel facilitates regeneration of damaged mucosa resulting in a synergistic effect for the treatment of ulcerative colitis.

Preparation of PLGA scaffolds with graded pores by using a gelatin-microsphere template as porogen

Porous scaffolds with graded pores are crucial to osteochondral regeneration. In this study, a technique combining solution casting with gelatin-microsphere template leaching has been developed to produce poly(L-lactide-co-glycolide) (PLGA) scaffolds with graded pores. The traditional emulsification and solvent extraction method was improved by using the gradient ethanol/water solutions to extract water to prepare gelatin microspheres with a smooth surface without the use of any surfactant. Gelatin microspheres with different diameters were in sequence put into a custom-made cylindrical Teflon mold and bonded together to obtain gelatin-microsphere templates. By using the gelatin-microsphere templates as porogen, PLGA scaffolds with graded pore size across the cylindrical axis were prepared. The porosity of the scaffold was as high as 95%. The pore size effect on osteoblasts was studied. The results showed that the graded scaffolds possessed good biocompatibility for osteoblast growth. During the 14 days culture, the cell proliferation of all the three pore layers displayed the trend of increasing. The proliferation rate of the large pore layer was lower than the other two layers. However, the difference of alkaline phosphatase activity on the three pore layers was not statistically significant. We assumed that it was probably because of the hydrophobicity and the short culture time. It was demonstrated that gradient ethanol/water solutions provided a simple way to prepared gelatin microspheres. The graded scaffolds would provide potential application for osteochondral regeneration.

Natural and Genetically Engineered Proteins for Tissue Engineering

To overcome the limitations of traditionally used autografts, allografts and, to a lesser extent, synthetic materials, there is the need to develop a new generation of scaffolds with adequate mechanical and structural support, control of cell attachment, migration, proliferation and differentiation and with bio-resorbable features. This suite of properties would allow the body to heal itself at the same rate as implant degradation. Genetic engineering offers a route to this level of control of biomaterial systems. The possibility of expressing biological components in nature and to modify or bioengineer them further, offers a path towards multifunctional biomaterial systems. This includes opportunities to generate new protein sequences, new self-assembling peptides or fusions of different bioactive domains or protein motifs. New protein sequences with tunable properties can be generated that can be used as new biomaterials. In this review we address some of the most frequently used proteins for tissue engineering and biomedical applications and describe the techniques most commonly used to functionalize protein-based biomaterials by combining them with bioactive molecules to enhance biological performance. We also highlight the use of genetic engineering, for protein heterologous expression and the synthesis of new protein-based biopolymers, focusing the advantages of these functionalized biopolymers when compared with their counterparts extracted directly from nature and modified by techniques such as physical adsorption or chemical modification.

Macrophage-specific targeting of isoniazid through mannosylated gelatin microspheres

Active targeting of drug molecules can be achieved by effective attachment of suitable ligands to the surface of carriers. The present work was attempted to prepare mannosylated gelatin microspheres (m-GMs) so as to achieve targeted delivery of isoniazid (INH) to alveolar macrophages (AMs) and maintain its therapeutic concentration for prolonged period of time. Microspheres were prepared by emulsification solvent extraction method and evaluated for physicochemical characteristics, drug release, ex vivo drug uptake by AMs and pharmacokinetic characteristics. Fourier transform infrared spectroscopy and nuclear magnetic resonance spectral analysis confirmed that mannosylation took place through Schiff base formation between aldehyde and amino groups of mannose and gelatin, respectively. Prepared microspheres offered suitable physicochemical characteristics for their delivery to AMs. Their average size was about 4 μm and drug entrapment efficiency of 56% was achieved with them. Ex vivo uptake results indicated that in comparison to plain microspheres, m-GMs were selectively uptaken and were found to be associated with phago-lysosomal vesicles of AMs. Pharmacokinetic studies showed the formulation could maintain the therapeutic concentration of INH for prolonged period of time even with a reduced clinical dose. m-GMs were found to be stable in broncheo-alveolar lavage fluid. The study concluded that ligand decorated carriers could be a potential strategy to improve the therapeutic properties of INH.

Fabrication of three-dimensional porous cell-laden hydrogel for tissue engineering

For tissue engineering applications, scaffolds should be porous to enable rapid nutrient and oxygen transfer while providing a three-dimensional (3D) microenvironment for the encapsulated cells. This dual characteristic can be achieved by fabrication of porous hydrogels that contain encapsulated cells. In this work, we developed a simple method that allows cell encapsulation and pore generation inside alginate hydrogels simultaneously. Gelatin beads of 150-300 microm diameter were used as a sacrificial porogen for generating pores within cell-laden hydrogels. Gelation of gelatin at low temperature (4 degrees C) was used to form beads without chemical crosslinking and their subsequent dissolution after cell encapsulation led to generation of pores within cell-laden hydrogels. The pore size and porosity of the scaffolds were controlled by the gelatin bead size and their volume ratio, respectively. Fabricated hydrogels were characterized for their internal microarchitecture, mechanical properties and permeability. Hydrogels exhibited a high degree of porosity with increasing gelatin bead content in contrast to nonporous alginate hydrogel. Furthermore, permeability increased by two to three orders while compressive modulus decreased with increasing porosity of the scaffolds. Application of these scaffolds for tissue engineering was tested by encapsulation of hepatocarcinoma cell line (HepG2). All the scaffolds showed similar cell viability; however, cell proliferation was enhanced under porous conditions. Furthermore, porous alginate hydrogels resulted in formation of larger spheroids and higher albumin secretion compared to nonporous conditions. These data suggest that porous alginate hydrogels may have provided a better environment for cell proliferation and albumin production. This may be due to the enhanced mass transfer of nutrients, oxygen and waste removal, which is potentially beneficial for tissue engineering and regenerative medicine applications.

Cyto- and genotoxicological assessment and functional characterization of N-vinyl-2-pyrrolidone-acrylic acid-based copolymeric hydrogels with potential for future use in wound healing applications

This study investigated the toxicity of N-vinyl-2-pyrrolidone-acrylic acid copolymer hydrogels crosslinked with ethylene glycol dimethacrylate or poly(ethylene glycol) dimethacrylate. There is a pressing need to establish the toxicity status of these new copolymers because they may find applications in future wound healing processes. Investigations revealed that the capacity of these hydrogels for swelling permitted the retention of high amounts of water yet still maintaining structural integrity. Reverse phase HPLC analysis suggested that unreacted monomeric base material was efficiently removed post-polymerization by applying an additional purification process. Subsequently, in vitro toxicity testing was performed utilizing direct and indirect contact exposure of the polymers to human keratinocytes (HaCaT) and human hepatoma (HepG2) cells. No indication of significant cell death was observed using the established MTT, neutral red (NR) and fluorescence-based toxicity endpoint indicators. In addition, the alkaline Comet assay showed no genotoxic effects following cell exposure to hydrogel extracts. Investigations at the nucleotide level using the Ames mutagenicity assay demonstrated no evidence of mutagenic activity associated with the polymers. Findings from this study demonstrated that these hydrogels are non-cytotoxic and further work can be carried out to investigate their potential as a wound-healing device that will impact positively on patient health and well-being.

Collagen-based wound dressing for doxycycline delivery: in-vivo evaluation in an infected excisional wound model in rats

Objectives

A novel collagen-based dressing consisting of 2,3-dihydroxybenzoic-acid-modified gelatin microspheres loaded with doxycycline has previously been reported to address both infection and matrix degradation. In the present study the potential benefits of the dressing were investigated in an excisional wound model in rats challenged with Pseudomonas aeruginosa.

Methods

A full-thick excisional wound (1.5 times 1.5 cm) was created on the dorsum of the rats and infection induced by injecting 105 colony-forming units (CFU) of P. aeruginosa. The healing pattern was assessed from wound reduction, matrix metalloprotease (MMP) levels, CFU reduction and histological and biochemical analysis.

Key findings

The treated group exhibited complete healing by day 15, compared with day 24 in the control group. Early subsidence of infection (99.9% by day 9) resulted in faster epidermal resurfacing and fibroplasias, whereas the microbial load exceeded 103 CFU even on day 15 in the control group and caused severe inflammation. Biochemical analysis showed that the expression of both collagen and hexosamine was significantly increased in the treated group. Gelatin zymography revealed prolonged expression of MMPs 2, 8 and 9 in the control group compared with the treated group.

Conclusions

The study indicates that the developed dressing attenuated both infection and metalloprotease levels, and may therefore have potential application in wound healing.