Studies on gelatin-based sponges. Part III: a comparative study of cross-linked gelatin/alginate, gelatin/hyaluronate and chitosan/hyaluronate sponges and their application as a wound dressing in full-thickness skin defect of rat

Microalgae Photo-Protectants and Related Bio-Carriers Loaded with Bioactive Entities for Skin Applications—An Insight of Microalgae Biotechnology

Microalgae are photosynthetic organisms known for producing valuable metabolites under different conditions such as extreme temperatures, high salinity, osmotic pressure, and ultraviolet radiation. In recent years, these metabolites have become a trend due to their versatility in applications such as pharmaceuticals, cosmetics, and others. They have even been proposed as an alternative source of bioactive metabolites to avoid the harmful effects on the environment produced by active compounds such as oxybenzone in commercials sunscreens. One of the most studied applications is the use of microalgae for skin care and topical use as cosmeceuticals. With the increasing demand for more environmentally friendly products in cosmetics, microalgae have been further explored in relation to this application. It has been shown that some microalgae are resistant to UV rays due to certain compounds such as mycosporine-like amino acids, sporopollenin, scytonemin, and others. These compounds have different mechanisms of action to mitigate UV damage induced. Still, they all have been proven to confer UV tolerance to microalgae with an absorbance spectrum like the one in conventional sunscreens. This review focuses on the use of these microalgae compounds obtained by UV stimulation and takes advantage of their natural UV-resistant characteristics to potentially apply them as an alternative for UV protection products.

Melatonin pre-treated bone marrow derived-mesenchymal stem cells prompt wound healing in rat models

Bone marrow derived-mesenchymal stem cells (BMSCs)-based therapy is an outstanding candidate for cutaneous wound healing. Melatonin (MEL) has been reported for its anti-inflammatory as well as tissue regenerative properties. Existing work aimed to explore the potential healing power of BMSCs pre-treated with MEL in a skin wound model. Adult rats were allocated into control, PIO, BMSCs (1 × 10⁵ cells), and MEL/BMSCs groups. On the 21 days post-wounding, tissues were sampled for analysis. The results demonstrated that compared to the control group, MEL/BMSCs therapy induced noticeable decline in wound area and elevated rate of wound retraction. Furthermore, marked increases in tissue hydroxyproline, as well as tissue content and gene expression level of vascular endothelial growth factor in MEL/BMSCs treated-wounded animals. Compared to the untreated control group, marked increases were found in antioxidant enzymatic activities together with elevated GSH levels in wounded tissues after MEL/BMSCs treatment. Moreover, therapeutically handled wounds with MEL/BMSCs revealed low levels of MDA, NO and protein carbonyls. Combined therapy with MEL/BMSCs relieved the inflammation witnessed by decreasing IL-1β, TNF-α and NF-κB levels in wounded tissues. Furthermore, noteworthy rises in levels of TGF-β and gene expression of α-SMA were noticed after MEL/BMSCs application that reveals their anti-scarring properties. Histologically, noticeable improvement in histopathological skin lesions in wound area and elevated the collagen synthesis and deposition. Collectively, the obtained data depict that the pre-treatment of BMSCs with MEL could potentially be a successful strategy for scaling-up the wound healing outcomes more than using BMSCs monotherapy in rat models.

Current Trends in Advanced Alginate-Based Wound Dressings for Chronic Wounds

Chronic wounds represent a major public health issue, with an extremely high cost worldwide. In healthy individuals, the wound healing process takes place in different stages: inflammation, cell proliferation (fibroblasts and keratinocytes of the dermis), and finally remodeling of the extracellular matrix (equilibrium between metalloproteinases and their inhibitors). In chronic wounds, the chronic inflammation favors exudate persistence and bacterial film has a special importance in the dynamics of chronic inflammation in wounds that do not heal. Recent advances in biopolymer-based materials for wound healing highlight the performance of specific alginate forms. An ideal wound dressing should be adherent to the wound surface and not to the wound bed, it should also be non-antigenic, biocompatible, semi-permeable, biodegradable, elastic but resistant, and cost-effective. It has to give protection against bacterial, infectious, mechanical, and thermal agents, to modulate the level of wound moisture, and to entrap and deliver drugs or other molecules This paper explores the roles of alginates in advanced wound-dressing forms with a particular emphasis on hydrogels, nanofibers networks, 3D-scaffolds or sponges entrapping fibroblasts, keratinocytes, or drugs to be released on the wound-bed. The latest research reports are presented and supported with in vitro and in vivo studies from the current literature.

An Overview on Collagen and Gelatin-Based Cryogels: Fabrication, Classification, Properties and Biomedical Applications

Decades of research into cryogels have resulted in the development of many types of cryogels for various applications. Collagen and gelatin possess nontoxicity, intrinsic gel-forming ability and physicochemical properties, and excellent biocompatibility and biodegradability, making them very desirable candidates for the fabrication of cryogels. Collagen-based cryogels (CBCs) and gelatin-based cryogels (GBCs) have been successfully applied as three-dimensional substrates for cell culture and have shown promise for biomedical use. A key point in the development of CBCs and GBCs is the quantitative and precise characterization of their properties and their correlation with preparation process and parameters, enabling these cryogels to be tuned to match engineering requirements. Great efforts have been devoted to fabricating these types of cryogels and exploring their potential biomedical application. However, to the best of our knowledge, no comprehensive overviews focused on CBCs and GBCs have been reported currently. In this review, we attempt to provide insight into the recent advances on such kinds of cryogels, including their fabrication methods and structural properties, as well as potential biomedical applications.

Antibacterial polyvinyl alcohol/bacterial cellulose/nano-silver hydrogels that effectively promote wound healing

The lack of antibacterial properties limits the application of bacterial cellulose hydrogels in wound dressings. To overcome this deficiency, silver nanoparticles (AgNPs) were introduced as antibacterial agents into a polyvinyl alcohol (PVA)/bacterial cellulose (BC) solution. A freeze-thaw method promoted formation of PVA/BC/Ag hydrogels and improved their mechanical properties. The physicochemical and biological properties of this hydrogel were systematically characterized. Those results showed the hydrogels contained a porous three-dimensional reticulum structure and had high mechanical properties. Also, the hydrogels possessed outstanding antibacterial properties and good biocompatibilities. More importantly, it effectively repaired wound defects in mice models and wound healing reached 97.89% within 15 days, and far exceeded other groups and indicated its potential for use in wound treatment applications.

Studies on novel chitosan/alginate and chitosan/bentonite flexible films incorporated with ZnO nano particles for accelerating dermal burn healing: In vivo and in vitro evaluation

This research work was performed to prepare chitosan-alginate-gelatin and chitosan-bentonite-gelatin films in different mass ratios incorporated with nano particles of Zinc Oxide, which were achieved through the method of green synthesis from Nettle leaf extract. The films were prepared and characterized based on their physicochemical properties, such as water absorption and porosity and surface morphology. Bentonite containing films illustrate more flexibility than alginate ones while the chitosan/bentonite composite films have a maximum water absorption capacity of about 170%. The antibacterial activity of the films was investigated against Staphylococcus aureus and Pseudomonas aeruginosa bacteria and it presents good inhibitory activities against the tested bacteria as compared to the control sample. Furthermore, vivo animal tests were performed to confirm the applicability of the prepared films as a healing material for burned skin. Skin appendages, such as hair follicles and sebaceous gland in the dermis, were detected in normal structures by applying both of the composites to damaged skin. In the control sample (gauze), no re-epithelialized area was observed, except in close proximity of the wound border. The results show that due to its full coverage of the wounds with new epithelium and hair follicles, bentonite-containing composites are more preferred.

Argon and Argon-Oxygen Plasma Surface Modification of Gelatin Nanofibers for Tissue Engineering Applications

In the present study, we developed a novel approach for functionalization of gelatin nanofibers using the plasma method for tissue engineering applications. For this purpose, tannic acid-crosslinked gelatin nanofibers were fabricated with electrospinning, followed by treatment with argon and argon–oxygen plasmas in a vacuum chamber. Samples were evaluated by using scanning electron microscopy (SEM), atomic force microscopy (AFM), attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, contact angle (CA) and X-ray diffraction (XRD). The biological activity of plasma treated gelatin nanofibers were further investigated by using fibroblasts as cell models. SEM studies showed that the average diameter and the surface morphology of nanofibers did not change after plasma treatment. However, the mean surface roughness (RMS) of samples were increased due to plasma activation. ATR-FTIR spectroscopy demonstrated several new bands on plasma treated fibers related to the plasma ionization of nanofibers. The CA test results stated that the surface of nanofibers became completely hydrophilic after argon–oxygen plasma treatment. Finally, increasing the polarity of crosslinked gelatin after plasma treatment resulted in an increase of the number of fibroblast cells. Overall, results expressed that our developed method could open new insights into the application of the plasma process for functionalization of biomedical scaffolds. Moreover, the cooperative interplay between gelatin biomaterials and argon/argon–oxygen plasmas discovered a key composition showing promising biocompatibility towards biological cells. Therefore, we strongly recommend plasma surface modification of nanofiber scaffolds as a pretreatment process for tissue engineering applications.

Formulation and Evaluation of Microwave-Modified Chitosan-Curcumin Nanoparticles-A Promising Nanomaterials Platform for Skin Tissue Regeneration Applications Following Burn Wounds

Improved physicochemical properties of chitosan-curcumin nanoparticulate carriers using microwave technology for skin burn wound application are reported. The microwave modified low molecular weight chitosan variant was used for nanoparticle formulation by ionic gelation method nanoparticles analyzed for their physicochemical properties. The antimicrobial activity against Staphylococcus aureus and Pseudomonas aeruginosa cultures, cytotoxicity and cell migration using human dermal fibroblasts-an adult cell line-were studied. The microwave modified chitosan variant had significantly reduced molecular weight, increased degree of deacetylation and decreased specific viscosity. The nanoparticles were nano-sized with high positive charge and good dispersibility with entrapment efficiency and drug content in between 99% and 100%, demonstrating almost no drug loss. Drug release was found to be sustained following Fickian the diffusion mechanism for drug release with higher cumulative drug release observed for formulation (F)2. The microwave treatment does not render a destructive effect on the chitosan molecule with the drug embedded in the core of nanoparticles. The optimized formulation precluded selected bacterial strain colonization, exerted no cytotoxic effect, and promoted cell migration within 24 h post application in comparison to blank and/or control application. Microwave modified low molecular weight chitosan-curcumin nanoparticles hold potential in delivery of curcumin into the skin to effectively treat skin manifestations.

Freeze-gelled alginate/gelatin scaffolds for wound healing applications: An in vitro, in vivo study

In this study, fabrication of a three-dimensional porous scaffold was performed using freeze gelation method. Recently, fabrication of scaffolds using polymer blends has become common for many tissue engineering applications due to their unique tunable properties. In this work, we fabricated alginate-gelatin porous hydrogels for wound healing application using a new method based on some modifications to the freeze-gelation method. Alginate and gelatin were mixed in three different ratios and the resulting solutions underwent freeze gelation to obtain 3D porous matrices. We analyzed the samples using different characterization tests. The scanning electron microscopy (SEM) results indicated that the freeze gelation method was successful in obtaining porous morphologies for all the fabricated alginate-gelatin samples as previously was seen in single-polymer fabrication using this method. The alginate to gelatin ratio affected swelling, biodegradation, cell culture and mechanical properties of the matrices. The scaffold with the lowest content of gelatin had the highest swelling ratio while biodegradation and cell proliferation and viability were increased with the gelatin content. Regarding the mechanical properties, as the gelatin content increased, the scaffold became more ductile and showed higher tensile strength. The in-vivo results also showed the biocompatibility of the blend scaffold and its positive role in wound healing process in rats. The low-cost procedure used in this study to fabricate the porous alginate-gelatin scaffolds can be adapted and modified to suit different tissue engineering applications.

Cell-cell interaction in a coculture system consisting of CRISPR/Cas9 mediated GFP knock-in HUVECs and MG-63 cells in alginate-GelMA based nanocomposites hydrogel as a 3D scaffold

The interaction between osteogenic and angiogenic cells through a coculturing system in biocompatible materials has been considered for successfully engineering vascularized bone tissue equivalents. In this study, we developed a hydrogel-blended scaffold consisted of gelatin methacryloyl (GelMA) and alginate enriched with hydroxyapatite nanoparticles (HAP) to model an in vitro prevascularized bone construct. The hydrogel-based scaffold revealed a higher mechanical stiffness than those of pure (GelMA), alginate, and (GelMA+ HAP) hydrogels. In the present study, we generated a green fluorescent protein (GFP) knock-in umbilical vein endothelial cells (HUVECs) cell line using the CRISPR/Cas9 technology. The GFP was inserted into the human-like ROSA locus of HUVECs genome. HUVECs expressing GFP were cocultured with OB-like cells (MG-63) within three-dimensionally (3D) fabricated hydrogel to investigate the response of cocultured osteoblasts and endothelial cells in a 3D structure. Cell viability under the 3D cocultured gel was higher than the 3D monocultured. Compared to the 3D monocultured condition, the cells were aligned and developed into the vessel-like structures. During 14 days of culture periods, the cells displayed actin protrusions by the formation of spike-like filopodia in the 3D cocultured model. Angiogenic and osteogenic-related genes such as CD31, vWF, and osteocalcin showed higher expression in the cocultured versus the monocultured. These results have collectively indicated that the 3D cocultured hydrogel facilitates interaction among cells, thereby having a greater effect on angiogenic and osteogenic properties in the absence of induction media.

A review on recent advances in chitosan based composite for hemostatic dressings

High mortality rate in potentially survivable casualties due to severe hemorrhage is a major challenge in today's battlefield because technological advancements have revolutionized the combat tactics and complicated the type and severity associated with wound grades. Quality of pre-hospital care prior to patient evacuation is crucial in determining the survival rate in injured patients. To deal with this challenge, considerable improvements in the hemostatic dressings have been introduced and pre-hospital care has been upgraded in many tactical combat casually care guidelines. Combat Gauze has been widely used bandage which is now been replaced by different chitosan based hemostatic dressings. It not only exhibits anti-bacterial activity but also induces hemostasis via direct interaction with erythrocytes and platelets. Its hemostasis mechanism is not dependent on host coagulation pathway which makes it an ideal dressing to stop bleeding in coagulopathic patients. Different generations of chitosan bandages have been developed to overcome the limitations of previous ones. This review provides performance analysis of chitosan bandage generations and discusses the progress made in its fabrication methods during the recent years.

Biomaterial Strategies to Reduce Implant-Associated Infections

Although the prophylaxis in controlling sterility within the operating room environment has been greatly improved, implant-associated infection is still one of the most serious complications in implant surgeries due to the existence of immune depression in the peri-implant area. The antibacterial ability of materials themselves logically becomes an important factor in preventing implant-associated infections. With the understanding of the pathogenesis of implant-associated infections, many approaches have been developed through providing an anti-adhesive surface, delivering antibacterial agents to disrupt cell-cell communication and preventing bacteria aggregation or biofilm formation, or killing bacteria directly (lysing the cell membrane). In this article, we review the current strategies in improving the antibacterial ability of materials to prevent implant infection and further present promising tactics in materials design and applications.

Biocomposite nanofiber matrices to support ECM remodeling by human dermal progenitors and enhanced wound closure

Cell-based therapies have recently been the focus of much research to enhance skin wound healing. An important challenge will be to develop vehicles for cell delivery that promote survival and uniform distribution of cells across the wound bed. These systems should be stiff enough to facilitate handling, whilst soft enough to limit damage to newly synthesized wound tissue and minimize patient discomfort. Herein, we developed several novel modifiable nanofibre scaffolds comprised of Poly (ε-caprolactone) (PCL) and gelatin (GE). We asked whether they could be used as a functional receptacle for adult human Skin-derived Precursor Cells (hSKPs) and how naked scaffolds impact endogenous skin wound healing. PCL and GE were electrospun in a single facile solvent to create composite scaffolds and displayed unique morphological and mechanical properties. After seeding with adult hSKPs, deposition of extracellular matrix proteins and sulphated glycosaminoglycans was found to be enhanced in composite grafts. Moreover, composite scaffolds exhibited significantly higher cell proliferation, greater cell spreading and integration within the nanofiber mats. Transplantation of acellular scaffolds into wounds revealed scaffolds exhibited improvement in dermal-epidermal thickness, axonal density and collagen deposition. These results demonstrate that PCL-based nanofiber scaffolds show promise as a cell delivery system for wound healing.

Evaluation of gelatin-hyaluronic acid composite hydrogels for accelerating wound healing

Excellent wound dressings maintain a warm and moist environment, thus accelerating wound healing. In this study, we cross-linked gelatin and hyaluronic acid with ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride in different ratios (gelatin/hyaluronic acid = 8:2, gelatin/hyaluronic acid = 5:5, gelatin/hyaluronic acid = 2:8), and explored the effects and mechanisms of gelatinhyaluronic acid hydrogels on wound healing. This was done by examining dressing properties, such as fluid uptake ability, water vapor transmission rate, and the rate of water evaporation. We further verified biological function by using in vitro and in vivo wound models. The hydrogels display appropriate fluid uptake ability and good water vapor transmission rate and rate of water evaporation all of which can provide an adequate moisture environment for wound healing. Cell cytotoxicity and proliferation tests show that the hydrogels have no cytotoxicity, furthermore, gelatin/hyaluronic acid = 8:2 hydrogels have the potential to promote cell proliferation. Animal wound models demonstrate that the hydrogels can effectively promote wound healing in vivo, in particular, the gelatin/hyaluronic acid = 8:2 group which promoted the most rapid healing. Accordingly, gelatin-hyaluronic acid dressings, especially the gelatin/hyaluronic acid = 8:2 hydrogels, have a promising outlook for clinical applications in wound healing.

Future Prospects for Scaffolding Methods and Biomaterials in Skin Tissue Engineering: A Review

Over centuries, the field of regenerative skin tissue engineering has had several advancements to facilitate faster wound healing and thereby restoration of skin. Skin tissue regeneration is mainly based on the use of suitable scaffold matrices. There are several scaffold types, such as porous, fibrous, microsphere, hydrogel, composite and acellular, etc., with discrete advantages and disadvantages. These scaffolds are either made up of highly biocompatible natural biomaterials, such as collagen, chitosan, etc., or synthetic materials, such as polycaprolactone (PCL), and poly-ethylene-glycol (PEG), etc. Composite scaffolds, which are a combination of natural or synthetic biomaterials, are highly biocompatible with improved tensile strength for effective skin tissue regeneration. Appropriate knowledge of the properties, advantages and disadvantages of various biomaterials and scaffolds will accelerate the production of suitable scaffolds for skin tissue regeneration applications. At the same time, emphasis on some of the leading challenges in the field of skin tissue engineering, such as cell interaction with scaffolds, faster cellular proliferation/differentiation, and vascularization of engineered tissues, is inevitable. In this review, we discuss various types of scaffolding approaches and biomaterials used in the field of skin tissue engineering and more importantly their future prospects in skin tissue regeneration efforts.

Enhanced bioadhesivity of dopamine-functionalized polysaccharidic membranes for general surgery applications

An emerging strategy to improve adhesiveness of biomaterials in wet conditions takes inspiration from the adhesive features of marine mussel, which reside in the chemical reactivity of catechols. In this work, a catechol-bearing molecule (dopamine) was chemically grafted onto alginate to develop a polysaccharide-based membrane with improved adhesive properties. The dopamine-modified alginates were characterized by NMR, UV spectroscopy and in vitro biocompatibility. Mechanical tests and in vitro adhesion studies pointed out the effects of the grafted dopamine within the membranes. The release of HA from these resorbable membranes was shown to stimulate fibroblasts activities (in vitro). Finally, a preliminary in vivo test was performed to evaluate the adhesiveness of the membrane on porcine intestine (serosa). Overall, this functionalized membrane was shown to be biocompatible and to possess considerable adhesive properties owing to the presence of dopamine residues grafted on the alginate backbone.

STATEMENT OF SIGNIFICANCE

This article describes the development of a mussels-inspired strategy for the development of an adhesive polysaccharide-based membrane for wound healing applications. Bioadhesion was achieved by grafting dopamine moieties on the structural component on the membrane (alginate): this novel biomaterial showed improved adhesiveness to the intestinal tissue, which was demonstrated by both in vitro and in vivo studies. Overall, this study points out how this nature-inspired strategy may be successfully exploited for the development of novel engineered biomaterials with enhanced bioadhesion, thus opening for novel applications in the field of general surgery.

Development of bioresorbable bilayered systems for application as affordable wound dressings

The objective of this work was the preparation and evaluation of a bioresorbable bilayered system for application in the treatment of dermal lesions. The system was based on a polyesterurethane as the external layer and a gelatin membrane as the internal layer. The polyesterurethane was synthesized from poly(ε-caprolactone), polyethylene glycol of 1 or 10 kDa as a hydrophilic component or Pluronic F127 as an amphiphilic component and l-lysine ethyl ester diisocyanate as an urethane precursor. Gelatin membrane was obtained by crosslinking with the naturally occurring crosslinker genipin. Three important points were addressed in this study: the physicochemical characterization of the system, the in vitro behaviour and the in vivo performance on a full-thickness wound defect of rat. The polyesterurethane containing polyethylene glycol of 10 kDa presented the optimum properties for the designed application as to be tested in animal experiments. The in vivo results showed good healing of the lesion with the formation of epidermis similar to normal rat skin. These promising results suggest the potential of this system to be used as an affordable wound dressing in the treatment of different dermal lesions.

Evaluation of a bilayered, micropatterned hydrogel dressing for full-thickness wound healing

Nearly 12 million wounds are treated in emergency departments throughout the United States every year. The limitations of current treatments for complex, full-thickness wounds are the driving force for the development of new wound treatment devices that result in faster healing of both dermal and epidermal tissue. Here, a bilayered, biodegradable hydrogel dressing that uses microarchitecture to guide two key steps in the proliferative phase of wound healing, re-epithelialization, and revascularization, was evaluated in vitro in a cell migration assay and in vivo in a bipedicle ischemic rat wound model. Results indicate that the Sharklet™-micropatterned apical layer of the dressing increased artificial wound coverage by up to 64%, P = 0.024 in vitro. In vivo evaluation demonstrated that the bilayered dressing construction enhanced overall healing outcomes significantly compared to untreated wounds and that these outcomes were not significantly different from a leading clinically available wound dressing. Collectively, these results demonstrate high potential for this new dressing to effectively accelerate wound healing.

Electrophoretically prepared hybrid materials for biopolymer hydrogel and layered ceramic nanoparticles

Background

In order to obtain biomaterials with controllable physicochemical properties, hybrid biomaterials composed of biocompatible biopolymers and ceramic nanoparticles have attracted interests. In this study, we prepared biopolymer/ceramic hybrids consisting of various natural biopolymers and layered double hydroxide (LDH) ceramic nanoparticles via an electrophoretic method. We studied the structures and controlled-release properties of these materials.

Results and discussion

X-ray diffraction (XRD) patterns and X-ray absorption spectra (XAS) showed that LDH nanoparticles were formed in a biopolymer hydrogel through electrophoretic reaction. Scanning electron microscopic (SEM) images showed that the ceramic nanoparticles were homogeneously distributed throughout the hydrogel matrix. An antioxidant agent (i.e., ferulic acid) was loaded onto agarose/LDH and gelatin/LDH hybrids, and the time-dependent release of ferulic acid was investigated via high-performance liquid chromatography (HPLC) for kinetic model fitting.

Conclusions

Biopolymer/LDH hybrid materials that were prepared by electrophoretic method created a homogeneous composite of two components and possessed controllable drug release properties according to the type of biopolymer.

Application of hyaluronic acid in the healing of non-experimental open wounds: A pilot study on 12 wounds in 10 client-owned dogs

Aim:

Veterinarians have frequently to deal with wounds to the skin, subcutis, and underlying muscle. The aim was to explore the application of hyaluronic acid (HA)-containing dressing on open skin wounds in dogs. The progress of healing was assessed by wound area reduction and two scoring scales applied in human medicine.

Materials and Methods:

Ten client-owned dogs with 12 cutaneous open wounds healed by the second intention were included. All wounds were treated using available in commerce HA-containing wound dressing from admission to complete re-epithelialization. At every clinical examination, wound area and scale scoring assessments were performed.

Results:

After debridement, an increased wound size was obtained while an improvement was determined by both grading systems. The median numbers of return to the clinic for bandage change were 5 times. The median time to complete wound healing was 34.5 days. The mean wound area at day 7, 14, 21, and 28 were, respectively, 90.4%, 47.7%, 22.4%, and 14.8% of the original size (for linear measurement) and 95.5%, 54.4%, 23.10%, and 14.8% of the original size (for software measurement). Regarding wound healing assessment tools, the agreement between two operators was considered high for both scales.

Conclusions:

HA-containing dressing may be a possible wound treatment for cutaneous open wounds in dogs. The assessment of wound quality using scale scoring system could be useful especially in the 1^st week and to direct clinical decision-making process.

The Effect of Mesenchymal Stem Cells and Chitosan Gel on Full Thickness Skin Wound Healing in Albino Rats: Histological, Immunohistochemical and Fluorescent Study

Background

Wound healing involves the integration of complex biological processes. Several studies examined numerous approaches to enhance wound healing and to minimize its related morbidity. Both chitosan and mesenchymal stem cells (MSCs) were used in treating skin wounds. The aim of the current work was to compare MSCs versus chitosan in wound healing, evaluate the most efficient route of administration of MSCs, either intradermal or systemic injection, and elicit the mechanisms inducing epidermal and dermal cell regeneration using histological, immunohistochemical and fluorescent techniques.

Material and Methods

Forty adult male Sprague Dawley albino rats were divided into four equal groups (ten rats in each group): control group (Group I); full thickness surgical skin wound model, Group II: Wound and chitosan gel. Group III: Wound treated with systemic injection of MSCs and Group IV: Wound treated with intradermal injection of MSCs. The healing ulcer was examined on day 3, 5, 10 and 15 for gross morphological evaluation and on day 10 and 15 for histological, immunohistochemical and fluorescent studies.

Results

Chitosan was proved to promote wound healing more than the control group but none of their wound reached complete closure. Better and faster healing of wounds in MSCs treated groups were manifested more than the control or chitosan treated groups. It was found that the intradermal route of administration of stem cells enhanced the rate of healing of skin wounds better than the systemic administration to the extent that, by the end of the fifteenth day of the experiment, the wounds were completely healed in all rats of this group. Histologically, the wound areas of group IV were hardly demarcated from the adjacent normal skin and showed complete regeneration of the epidermis, dermis, hypodermis and underlying muscle fibers. Collagen fibers were arranged in many directions, with significant increase in their area percent, surrounding fully regenerated hair follicles and sebaceous glands in the dermis of the healed areas more than in other groups.

Conclusion

MSCs enhanced the healing process of wound closure more than chitosan gel treatment. Furthermore, MSCs injected intradermally, were more efficient in accelerating wound healing than any other mode of treatment.

Interaction of human plasma proteins with thin gelatin-based hydrogel films: a QCM-D and ToF-SIMS study

In the fields of surgery and regenerative medicine, it is crucial to understand the interactions of proteins with the biomaterials used as implants. Protein adsorption directly influences cell-material interactions in vivo and, as a result, regulates, for example, cell adhesion on the surface of the implant. Therefore, the development of suitable analytical techniques together with well-defined model systems allowing for the detection, characterization, and quantification of protein adsorbates is essential. In this study, a protocol for the deposition of highly stable, thin gelatin-based films on various substrates has been developed. The hydrogel films were characterized morphologically and chemically. Due to the obtained low thickness of the hydrogel layer, this setup allowed for a quantitative study on the interaction of human proteins (albumin and fibrinogen) with the hydrogel by Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D). This technique enables the determination of adsorbant mass and changes in the shear modulus of the hydrogel layer upon adsorption of human proteins. Furthermore, Secondary Ion Mass Spectrometry and principal component analysis was applied to monitor the changed composition of the topmost adsorbate layer. This approach opens interesting perspectives for a sensitive screening of viscoelastic biomaterials that could be used for regenerative medicine.

The in vitro characterization of a gelatin scaffold, prepared by cryogelation and assessed in vivo as a dermal replacement in wound repair

A sheet gelatin scaffold with attached silicone pseudoepidermal layer for wound repair purposes was produced by a cryogelation technique. The resulting scaffold possessed an interconnected macroporous structure with a pore size distribution of 131 ± 17 μm at one surface decreasing to 30 ± 8 μm at the attached silicone surface. The dynamic storage modulus (G') and mechanical stability were comparable to the clinical gold standard dermal regeneration template, Integra®. The scaffolds were seeded in vitro with human primary dermal fibroblasts. The gelatin based material was not only non-cytotoxic, but over a 28 day culture period also demonstrated advantages in cell migration, proliferation and distribution within the matrix when compared with Integra®. When seeded with human keratinocytes, the neoepidermal layer that formed over the cryogel scaffold appeared to be more advanced and mature when compared with that formed over Integra®. The in vivo application of the gelatin scaffold in a porcine wound healing model showed that the material supports wound healing by allowing host cellular infiltration, biointegration and remodelling. The results of our in vitro and in vivo studies suggest that the gelatin based scaffold produced by a cryogelation technique is a promising material for dermal substitution, wound healing and other potential biomedical applications.

Natural and synthetic polymers for wounds and burns dressing

In the last years, health care professionals faced with an increasing number of patients suffering from wounds and burns difficult to treat and heal. During the wound healing process, the dressing protects the injury and contributes to the recovery of dermal and epidermal tissues. Because their biocompatibility, biodegradability and similarity to macromolecules recognized by the human body, some natural polymers such as polysaccharides (alginates, chitin, chitosan, heparin, chondroitin), proteoglycans and proteins (collagen, gelatin, fibrin, keratin, silk fibroin, eggshell membrane) are extensively used in wounds and burns management. Obtained by electrospinning technique, some synthetic polymers like biomimetic extracellular matrix micro/nanoscale fibers based on polyglycolic acid, polylactic acid, polyacrylic acid, poly-ɛ-caprolactone, polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, exhibit in vivo and in vitro wound healing properties and enhance re-epithelialization. They provide an optimal microenvironment for cell proliferation, migration and differentiation, due to their biocompatibility, biodegradability, peculiar structure and good mechanical properties. Thus, synthetic polymers are used also in regenerative medicine for cartilage, bone, vascular, nerve and ligament repair and restoration. Biocompatible with fibroblasts and keratinocytes, tissue engineered skin is indicated for regeneration and remodeling of human epidermis and wound healing improving the treatment of severe skin defects or partial-thickness burn injuries.

Ultrasound stimulus to enhance the bone regeneration capability of gelatin cryogels

In the present study, gelatin-based cryogels have been seeded with human SAOS-2 osteoblasts. In order to overcome the drawbacks associated with in vitro culture systems, such as limited diffusion and inhomogeneous cell-matrix distribution, this work describes the application of ultrasounds (average power, 149 mW; frequency, 1.5 MHz) to physically enhance the cell culture in vitro. The results indicate that the physical stimulation of cell-seeded gelatin-based cryogels upregulates the bone matrix production.

Synthetic and bio-artificial tactile sensing: a review

This paper reviews the state of the art of artificial tactile sensing, with a particular focus on bio-hybrid and fully-biological approaches. To this aim, the study of physiology of the human sense of touch and of the coding mechanisms of tactile information is a significant starting point, which is briefly explored in this review. Then, the progress towards the development of an artificial sense of touch are investigated. Artificial tactile sensing is analysed with respect to the possible approaches to fabricate the outer interface layer: synthetic skin versus bio-artificial skin. With particular respect to the synthetic skin approach, a brief overview is provided on various technologies and transduction principles that can be integrated beneath the skin layer. Then, the main focus moves to approaches characterized by the use of bio-artificial skin as an outer layer of the artificial sensory system. Within this design solution for the skin, bio-hybrid and fully-biological tactile sensing systems are thoroughly presented: while significant results have been reported for the development of tissue engineered skins, the development of mechanotransduction units and their integration is a recent trend that is still lagging behind, therefore requiring research efforts and investments. In the last part of the paper, application domains and perspectives of the reviewed tactile sensing technologies are discussed.

PLLA-collagen and PLLA-gelatin hybrid scaffolds with funnel-like porous structure for skin tissue engineering

In skin tissue engineering, a three-dimensional porous scaffold is necessary to support cell adhesion and proliferation and to guide cells moving into the repair area in the wound healing process. Structurally, the porous scaffold should have an open and interconnected porous architecture to facilitate homogenous cell distribution. Moreover, the scaffolds should be mechanically strong to protect deformation during the formation of new skin. In this study, the hybrid scaffolds were prepared by forming funnel-like collagen or gelatin sponge on a woven poly(l-lactic acid) (PLLA) mesh. The hybrid scaffolds combined the advantages of both collagen or gelatin (good cell-interactions) and PLLA mesh (high mechanical strength). The hybrid scaffolds were used to culture dermal fibroblasts for dermal tissue engineering. The funnel-like porous structure promoted homogeneous cell distribution and extracellular matrix production. The PLLA mesh reinforced the scaffold to avoid deformation. Subcutaneous implantation showed that the PLLA-collagen and PLLA-gelatin scaffolds promoted the regeneration of dermal tissue and epidermis and reduced contraction during the formation of new tissue. These results indicate that funnel-like hybrid scaffolds can be used for skin tissue regeneration.

Electromagnetic stimulation to optimize the bone regeneration capacity of gelatin-based cryogels

One of the key challenges in reconstructive bone surgery is to provide living constructs that possess the ability to integrate in the surrounding host tissue. Bone graft substitutes and biomaterials have already been widely used to heal critical-size bone defects due to trauma, tumor resection and tissue degeneration. In the present study, gelatin-based cryogels have been seeded with human SAOS-2 osteoblasts followed by the in vitro culture of the cells. In order to overcome the drawbacks associated with static culture systems, including limited diffusion and in homogeneous cell-matrix distribution, the present work describes the application of a bioreactor to physically enhance the cell culture in vitro using an electromagnetic stimulus. The results indicate that the physical stimulation of cell-seeded gelatin-based cryogels upregulates the bone matrix production. We anticipate that the scaffolds developed consisting of human bone proteins and cells could be applied for clinical purposes related to bone repair.

CHITOSAN IN APPLICATIONS OF BIOMEDICAL DEVICES

Chitosan is a natural polysaccharide with great potential for biomedical applications due to its biocompatibility, biodegradable capability, and nontoxicity. Various techniques used for preparing chitosan microspheres/membranes and evaluations of these fabrications have also been reviewed. The hydrophilicity of chitosan provides unique characteristics of hydrogel formation with the acidic media and may entrap the drug content inside of the matrix for controlled release. In order to improve upon the scope of preparation of chitosan microspheres, we had successfully employed and incorporated a high-voltage system into the direct pumping injection process. The wide range of drug release profiles could be attributed to the surface characteristics, porosities, and various structures of chitosan microspheres upon treatment with Na5P3O10/NaOH solutions of various volume ratios. We also demonstrated that with the addition of chitosan/β-TCP microspheres as a constituent into the PMMA cement significantly decreases the curing peak temperature and increases the setting time. The excellent gelforming property of chitosan offers another biomedical application in membrane separation fields. Chitosan membranes were prepared by a thermal induced phase separation method, following treatment with nontoxic NaOH gelating and Na5P3O10, Na2SO3 crosslinking agents. In order to further improve the mechanical strength and biocompatibility and to expand the potential of chitosan GTR membranes in periodontal applications, various chitosan membranes incorporating with negatively charged alginate, bioactive tricalcium phosphate, and platelet rich plasma, respectively, were also prepared and characterized. Moreover, we had also utilized chitosan, which with good blood-clotting, cheap, and easy preparation characteristics, as the raw material to prepare rapid clotting wound dressing and tooth plug.

Bone tissue engineering using bone marrow stromal cells and an injectable sodium alginate/gelatin scaffold

To investigate the potential application of bone marrow stromal cells (BMSCs) and an injectable sodium alginate/gelatin scaffold for bone tissue engineering (BTE). The phenotype of osteogenic BMSCs was examined by mineralized nodules formation and type I collagen expression. Cell proliferation was evaluated by MTT assay. The biocompatibility of scaffold and osteogenic cells were examined by hematoxylin and eosin (H&E) staining. Ectopic bone formation as well as closure of rabbit calvarial critical-sized defects following scaffold-cell implantation were analyzed by histological examination and computed tomography (CT) scanning. Spindle-shaped osteogenic cells of high purity were derived from BMSCs. The osteogenic cells and sodium alginate/gelatin (2:3) scaffold presented fine biocompatibility following cross-linking with 0.6% of CaCl(2). After implantation, the scaffold-cell construct promoted both ectopic bone formation and bone healing in the rabbit calvarial critical-sized defect model. Our data demonstrated that the sodium alginate/gelatin scaffold could be a suitable biomaterial for bone engineering, and the scaffold-osteogenic cells construct is a promising alternative approach for the bone healing process.

Thiolated carboxymethyl-hyaluronic-Acid-based biomaterials enhance wound healing in rats, dogs, and horses

The progression of wound healing is a complicated but well-known process involving many factors, yet there are few products on the market that enhance and accelerate wound healing. This is particularly problematic in veterinary medicine where multiple species must be treated and large animals heal slower, oftentimes with complicating factors such as the development of exuberant granulation tissue. In this study a crosslinked-hyaluronic-acid (HA-) based biomaterial was used to treat wounds on multiple species: rats, dogs, and horses. The base molecule, thiolated carboxymethyl HA, was first found to increase keratinocyte proliferation in vitro. Crosslinked gels and films were then both found to enhance the rate of wound healing in rats and resulted in thicker epidermis than untreated controls. Crosslinked films were used to treat wounds on forelimbs of dogs and horses. Although wounds healed slower compared to rats, the films again enhanced wound healing compared to untreated controls, both in terms of wound closure and quality of tissue. This study indicates that these crosslinked HA-based biomaterials enhance wound healing across multiple species and therefore may prove particularly useful in veterinary medicine. Reduced wound closure times and better quality of healed tissue would decrease risk of infection and pain associated with open wounds.

Mesenchymal Stem Cells in Combination with Scaffolds for Bone Tissue Engineering

This article reviews past and current strategies of the use of bone graft substitutes along with the future biologic alternatives that can enhance the functional capabilities of those grafts. Many of these bone graft substitute alternatives include ceramic-based, allograft-based, factor-based and polymer-based whereas others are cell-based. The ways of achieving the goal of tissue engineering using stem cells and their lineage to regenerate tissue have been detailed with regard to both the generation of sufficient vascular invasion of the tissue to improve oxygen and nutrient supply, and the development of innovative physical/chemical stimuli to induce bone formation with the proper biomaterial to carry the cells. It is imperative to integrate basic polymer science with molecular biology and stem cell biology, in the design of new materials that perform very sophisticated signaling needed for integration and function.

Potential applications of natural origin polymer-based systems in soft tissue regeneration

Despite the many advances in tissue engineering approaches, scientists still face significant challenges in trying to repair and replace soft tissues. Nature-inspired routes involving the creation of polymer-based systems of natural origins constitute an interesting alternative route to produce novel materials. The interest in these materials comes from the possibility of constructing multi-component systems that can be manipulated by composition allowing one to mimic the tissue environment required for the cellular regeneration of soft tissues. For this purpose, factors such as the design, choice, and compatibility of the polymers are considered to be key factors for successful strategies in soft tissue regeneration. More recently, polysaccharide-protein based systems have being increasingly studied and proposed for the treatment of soft tissues. The characteristics, properties, and compatibility of the resulting materials investigated in the last 10 years, as well as commercially available matrices or those currently under investigation are the subject matter of this review.

Preparation of aligned porous gelatin scaffolds by unidirectional freeze-drying method

Porous gelatin scaffolds with microtubule orientation structure were manufactured by unidirectional freeze-drying technology, and their porous structure was characterized by scanning electron microscopy. Scaffolds with tunable pore size and high porosity up to 98% were obtained by adjusting the concentration of the gelatin solution and crosslinking agent during the preparation process. All the porous gelatin scaffolds exhibited oriented microtubule pores, with width and length from 50 to 100 microm and 100 to 500 microm, respectively. Meanwhile, the properties of the scaffolds, such as porosity, water adsorption ability and compressive strength, were studied. In vitro enzymatic degradation results showed that the absolute weight loss of the gelatin scaffolds exhibited an increasing trend from low to high gelatin concentration used to prepare gelatin scaffolds; in vitro cell culture results indicated that the porous gelatin scaffolds were non-toxic to cartilage cells, since the cells spread and grew well.