The use of fibrin glue in skin grafts and tissue-engineered skin replacements: a review

Biopolymer hydrogels and synergistic blends for tailored wound healing

Biopolymers have a transformative role in wound repair due to their biocompatibility, ability to stimulate collagen production, and controlled drug and growth factor delivery. This article delves into the biological parameters critical to wound healing emphasizing how combinations of hydrogels with reparative properties can be strategically designed to create matrices that stimulate targeted cellular responses at the wound site to facilitate tissue repair and recovery. Beyond a detailed examination of various biopolymer types and their functionalities in wound dressings acknowledging that the optimal choice depends on the specific wound type and application, this evaluation provides concepts for developing synergistic biopolymer blends to create next-generation dressings with enhanced efficiencies. Furthermore, the incorporation of therapeutic agents such as medications and wound healing accelerators into dressings to enhance their efficacy is examined. These agents often possess desirable properties such as antibacterial activity, antioxidant effects, and the ability to promote collagen synthesis and tissue regeneration. Finally, recent advancements in conductive hydrogels are explored, highlighting their capabilities in treatment and real-time wound monitoring. This comprehensive resource emphasizes the importance of optimizing ingredient efficiency besides assisting researchers in selecting suitable materials for personalized wound dressings, ultimately leading to more sophisticated and effective wound management strategies.

Securing skin grafts: A network meta-analysis

BACKGROUND

Skin grafting is one of the most common procedures in plastic surgery. However, there are no defined guidelines for optimal fixation. The aim of this network meta-analysis (NMA) was to consolidate existing evidence by comparing various graft securing methods and determining the most effective approach for clinical practice.

METHODS

An NMA was conducted using a predetermined protocol after searching several electronic databases from inception to October 2023 for studies examining skin grafting fixation outcomes in adults.

RESULTS

A total of 27 studies were included in the analysis involving 1937 patients. Negative pressure wound therapy (NPWT) was the only method to significantly improve graft take percentages in comparison with the other modalities, whereas tie-over bolster (TOB) provided the worst results in take rates when examined as events. Fibrin glue (FIB) and TOB reduced hematoma and seroma rates when data were investigated in conjunction.

CONCLUSIONS

NPWT appears to be the most effective for skin graft adherence as opposed to traditional techniques. Its cost-effectiveness remains unclear, as NPWT is a relatively costly intervention compared with other methods. FIB and TOB are methods that can serve as a method of reducing hematoma and seroma rates in patients at high risk of bleeding.

LEVEL OF EVIDENCE

I.

Continuous negative-pressure wound therapy improves the survival rate of skin grafts and shortens the time required for skin graft survival

BACKGROUND

The effectiveness of negative-pressure wound therapy (NPWT) in skin graft fixation has been demonstrated in several clinical studies. However, in vitro and in vivo studies on skin graft fixation with NPWT have been scarce. In this in vivo study, we aimed to determine whether NPWT fixation enhances skin graft survival and how it contributes to improving skin graft survival biologically.

MATERIALS AND METHODS

We harvested skin from the bilateral abdominal wall of 88 mice after anesthetizing them. Full-thickness skin grafts (FTSGs) were performed on contralateral harvest sites, and grafts were fixed using NPWT (continuous and intermittent modes), conventional compression methods, and wrapping with polyurethane foam as a control group. On days 5 and 10 of grafting, the survival rates of the FTSGs were evaluated. Immunohistopathological analysis and measurement of the expression levels of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (FGF-2), and epidermal growth factor (EGF) were performed.

RESULTS

The survival rates of FTSG in the continuous NPWT group were significantly higher than those in the other groups. The number of capillaries in the dermis was significantly higher in the continuous NPWT group than in the other groups. In the wound bed, VEGF levels were significantly higher in both NPWT groups than in the other groups.

CONCLUSION

Continuous NPWT increases the survival rate of FTSGs and shortens the duration of skin graft survival.

Sticking to What Matters: A Matched Comparative Study of Fibrin Glue and Mechanical Fixation for Split-Thickness Skin Grafts in the Lower Extremity

Background: Split-thickness skin grafts (STSGs) remain a valuable tool in the reconstructive surgeons' armamentarium. Staple or suture mechanical fixation (MF) serves as the gold standard of care, though fibrin glue (FG) has gained popularity as a fixation modality. We compare STSG outcomes following application of FG versus MF through a study of lower extremity wounds. Methods: A retrospective review (2016-2019) of patients who underwent a STSG was performed. Two cohorts consisting of patients undergoing a STSG with FG or MF (suture or staple) were matched according to wound size, wound location, and body mass index. Results: A total of 67 patients with 79 wounds were included (FG: n = 30, wounds = 39; MF: n = 37; wounds = 40). There was no significant difference between groups regarding time to 100% graft take (FG: 39 days, MF: 35.1 days; P < .384) or 180-day graft complications (FG: 10.3%, MF: 15%; P < .737). Adjusted operative time for FG (51.8 min) was lower than for MF cases (67.5 min) at a level that approached significance (P < .094). FG patients were significantly less likely to require a postoperative wound vacuum-assisted closure (VAC) (FG: 16.7%; MF: 76.7%; P < .001) and required a significantly lower number of 30-day postoperative visits (FG: 1.5 ± .78 visits; MF: 2.5 ± .03 visits; P < .001). The MF group had higher mean aggregate charges ($211,090) compared with the FG group (mean: $149,907), although these were not statistically significant (P > .05). Conclusion: The use of FG for STSG shows comparable clinical outcomes to MF, with a significantly decreased need for postoperative wound VAC, the number of 30-day postoperative visits, and a lower wound-adjusted operative time.

3D Lipogluing: Preliminary Results of a Novel Technique for Direct Three-dimensional Fat Grafting in Breast Reconstruction Surgery

Lipofilling has emerged as an effective technique in breast reconstruction for enhancing aesthetic outcomes and addressing residual deformities. Traditionally, fat grafting has been performed as a secondary step in implant-based breast reconstruction during the replacement of the expander with a breast implant or as a revisional procedure. Our study investigates the technical feasibility and presents preliminary results of a new promising technique for delivering fat grafting in a three-dimensional (3D) shape, directly during mastectomy with immediate breast reconstruction or in delayed breast reconstructive procedures. Our new 3D lipogluing technique involves securing the fat tissue in a 3D manner using fibrin glue. This method enhances the coverage of soft tissues and provides improved volume and shape supplementation. In selected cases between December 2015 and September 2023, we treated 24 patients using the 3D lipogluing technique and five patients using 3D lipocubing (without use of fibrin glue).The patient cohort consisted of different indications for breast reconstructions: direct-to-implant, expander-based breast reconstruction, and "conservative" surgery. Preliminary findings suggest the technique is a safe and effective approach that can enhance the soft-tissue envelope of reconstructed breasts by acting as an autologous scaffold, owing to its regenerative properties. This technique not only improves the overall aesthetic outcome but also has the potential to reduce implant-related complications. Furthermore, ongoing studies are investigating methods to optimize the results and explore the potential application of 3D lipogluing and 3D lipocubing in breast-conserving oncoplastic surgery, cosmetic breast surgery, and other areas of plastic reconstructive and aesthetic surgery.

Fabrication of chitosan/fibrin-armored multifunctional silver nanocomposites to improve antibacterial and wound healing activities

A wound healing substitute promotes rapid tissue regeneration and protects wound sites from microbial contamination. The silver-based antiseptic frequently moist skin stains, burns and irritation, penetrates deep wounds and protects against pathogenic infections. Thus, we formulated a novel fibrin/chitosan encapsulated silver nanoparticle (CH:F:SPG-CH:SNP) composites bandage accelerating the polymicrobial wound healing. Electrospinning method was employed to form the nano-porous, inexpensive, and biocompatible smart bandages. The structural, functional, and mechanical properties were analyzed for the prepared composites. The biological capacity of prepared CH:F:SPG-CH:SNP bandage was assessed against NIH-3 T3 fibroblast and HaCaT cell lines. In vitro hemolytic assays using red blood cells were extensively studied and explored the low hemolytic effect (4.5 %). In addition, the improved drug delivery nature captured for the CH:F:SPG-CH:SNP composite bandage. Antibacterial experiments were achieved against Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus and Lactobacillus bulgaricus using zone inhibition method. Moreover, in-vivo wound healing efficacy of fabricated smart bandage was evaluated on the albino Wistar rats which revealed the significant improvement on the postoperative abdomen wounds.

Novel Local "Off-the-Shelf" Immunotherapy for the Treatment of Myeloma Bone Disease

Myeloma bone disease (MBD) is one of the major complications in multiple myeloma (MM)-the second most frequent hematologic malignancy. It is characterized by the formation of bone lesions due to the local action of proliferating MM cells, and to date, no effective therapy has been developed. In this study, we propose a novel approach for the local treatment of MBD with a combination of natural killer cells (NKs) and mesenchymal stem cells (MSCs) within a fibrin scaffold, altogether known as FINM. The unique biological properties of the NKs and MSCs, joined to the injectable biocompatible fibrin, permitted to obtain an efficient "off-the-shelf" ready-to-use composite for the local treatment of MBD. Our in vitro analyses demonstrate that NKs within FINM exert a robust anti-tumor activity against MM cell lines and primary cells, with the capacity to suppress osteoclast activity (~60%) within in vitro 3D model of MBD. Furthermore, NKs' post-thawing cytotoxic activity is significantly enhanced (~75%) in the presence of MSCs, which circumvents the decrease of NKs cytotoxicity after thawing, a well-known issue in the cryopreservation of NKs. To reduce the tumor escape, we combined FINM with other therapeutic agents (bortezomib (BZ), and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)), observing a clear therapeutic synergistic effect in vitro. Finally, the therapeutic efficacy of FINM in combination with BZ and TRAIL was assessed in a mouse model of MM, achieving 16-fold smaller tumors compared to the control group without treatment. These results suggest the potential of FINM to serve as an allogeneic "off-the-shelf" approach to improve the outcomes of patients suffering from MBD.

A Novel Perspective on Tissue Engineering Potentials of Periodontal Ligament Stem Cells

It is challenging to completely and predictably regenerate the missing periodontal tissues caused by the trauma or disease. To regenerate the periodontium, there is a need to consider several aspects that co-occur with periodontal development. This study provides an overview of the most up-to-date investigations on the characteristics and immunomodulatory features of Periodontal Ligament Stem Cells (PDLSCs) and the recent interventions performed using these cells, focusing on cell survival, proliferation, and differentiation. Keeping in mind the relationship between age and potency of PDLSCs, this work also demonstrates the necessity of establishing dental-derived stem cell banks for tissue regeneration applications. The data were collected from Pubmed and Google Scholar databases with the keywords of periodontal ligament stem cells, tissue engineering, characteristics, and stem cell therapy. The results showed the presence of wide-ranging research reports supporting the usability of PDLSCs for periodontal reconstruction. However, a better understanding of self-restoration for adequate regulation of adult stem cell growth is needed for various applied purposes.

Protocol for an open randomised controlled trial investigating Fibrin Glue in Skin grafts for Skin cancer (FiGSS)

INTRODUCTION

Skin cancer is a common disease in the tropics, and oncological resection typically requires reconstruction with skin grafts. Fibrin glue, initially established as a haemostatic agent, has been studied extensively as an adhesive for skin grafts in burns. This study aims to investigate the use of fibrin as an adhesive for split skin grafts in skin cancers.

METHODS AND ANALYSIS

The study design is a prospective randomised controlled trial with the aim of investigating the impact of two different methods of split skin graft fixation. The intervention of fibrin glue will be compared with the control of staples or sutures. The trial will be conducted at two sites, a public hospital and a private hospital in Townsville, Australia, over a 24-month period with 334 participants to be recruited. Consecutive patients presenting for skin excisions and grafting will be eligible to participate in this study. Randomisation will be on the level of the patient. The primary outcome is graft take based on wound healing at 1 month. Secondary outcomes will be pain on dressing changes and operative time.

ETHICS AND DISSEMINATION

The study has been approved by The Townsville University Hospital Human Research Ethics Committee. Findings will be disseminated in conference presentations and journals and through online electronic media.

TRIAL REGISTRATION NUMBER

ACTRN12618000484246.

Platelet-rich plasma: a comparative and economical therapy for wound healing and tissue regeneration

Rise in the incidences of chronic degenerative diseases with aging makes wound care a socio-economic burden and unceasingly necessitates a novel, economical, and efficient wound healing treatment. Platelets have a crucial role in hemostasis and thrombosis by modulating distinct mechanistic phases of wound healing, such as promoting and stabilizing the clot. Platelet-rich plasma (PRP) contains a high concentration of platelets than naïve plasma and has an autologous origin with no immunogenic adverse reactions. As a consequence, PRP has gained significant attention as a therapeutic to augment the healing process. Since the past few decades, a robust volume of research and clinical trials have been performed to exploit extensive role of PRP in wound healing/tissue regeneration. Despite these rigorous studies and their application in diversified medical fields, efficacy of PRP-based therapies is continuously questioned owing to the paucity of large samplesizes, controlled clinical trials, and standard protocols. This review systematically delineates the process of wound healing and involvement of platelets in tissue repair mechanisms. Additionally, emphasis is laid on PRP, its preparation methods, handling, classification,application in wound healing, and PRP as regenerative therapeutics combined with biomaterials and mesenchymal stem cells (MSCs).

Membranes for the life sciences and their future roles in medicine

Since the global outbreak of COVID-19, membrane technology for clinical treatments, including extracorporeal membrane oxygenation (ECMO) and protective masks and clothing, has attracted intense research attention for its irreplaceable abilities. Membrane research and applications are now playing an increasingly important role in various fields of life science. In addition to intrinsic properties such as size sieving, dissolution and diffusion, membranes are often endowed with additional functions as cell scaffolds, catalysts or sensors to satisfy the specific requirements of different clinical applications. In this review, we will introduce and discuss state-of-the-art membranes and their respective functions in four typical areas of life science: artificial organs, tissue engineering, in vitro blood diagnosis and medical support. Emphasis will be given to the description of certain specific functions required of membranes in each field to provide guidance for the selection and fabrication of the membrane material. The advantages and disadvantages of these membranes have been compared to indicate further development directions for different clinical applications. Finally, we propose challenges and outlooks for future development.

Medical Adhesives and Their Role in Laparoscopic Surgery—A Review of Literature

Laparoscopic surgery is undergoing rapid development. Replacing the traditional method of joining cut tissues with sutures or staples could greatly simplify and speed up laparoscopic procedures. This alternative could undoubtedly be adhesives. For decades, scientists have been working on a material to bond tissues together to create the best possible conditions for tissue regeneration. The results of research on tissue adhesives achieved over the past years show comparable treatment effects to traditional methods. Tissue adhesives are a good alternative to surgical sutures in wound closure. This article is a review of the most important groups of tissue adhesives including their properties and possible applications. Recent reports on the development of biological adhesives are also discussed.

Combinatorial wound healing therapy using adhesive nanofibrous membrane equipped with wearable LED patches for photobiomodulation

Wound healing is the dynamic tissue regeneration process replacing devitalized and missing tissue layers. With the development of photomedicine techniques in wound healing, safe and noninvasive photobiomodulation therapy is receiving attention. Effective wound management in photobiomodulation is challenged, however, by limited control of the geometrical mismatches on the injured skin surface. Here, adhesive hyaluronic acid-based gelatin nanofibrous membranes integrated with multiple light-emitting diode (LED) arrays are developed as a skin-attachable patch. The nanofibrous wound dressing is expected to mimic the three-dimensional structure of the extracellular matrix, and its adhesiveness allows tight coupling between the wound sites and the flexible LED patch. Experimental results demonstrate that our medical device accelerates the initial wound healing process by the synergetic effects of the wound dressing and LED irradiation. Our proposed technology promises progress for wound healing management and other biomedical applications.

Chorion-derived extracellular matrix hydrogel and fibronectin surface coatings show similar beneficial effects on endothelialization of expanded polytetrafluorethylene vascular grafts

The endothelium plays an important regulatory role for cardiovascular homeostasis. Rapid endothelialization of small diameter vascular grafts (SDVGs) is crucial to ensure long-term patency. Here, we assessed a human placental chorionic extracellular matrix hydrogel (hpcECM-gel) as coating material and compared it to human fibronectin in-vitro. hpcECM-gels were produced from placental chorion by decellularization and enzymatic digestion. Human umbilical vein endothelial cells (HUVECs) were seeded to non-, fibronectin- or hpcECM-gel-coated expanded polytetrafluorethylene (ePTFE) SDVGs. Coating efficiency as well as endothelial cell proliferation, migration and adhesion studies on grafts were performed. hpcECM-gel depicted high collagen and glycosaminoglycan content and neglectable DNA amounts. Laminin and fibronectin were both retained in the hpcECM-gel after the decellularization process. HUVEC as well as endothelial progenitor cell attachment were both significantly enhanced on hpcECM-gel coated grafts. HUVECs seeded to hpcECM-gel depicted significantly higher platelet endothelial cell adhesion molecule-1 (PECAM-1) expression in the perinuclear region. Cell retention to flow was enhanced on fibronectin and hpcECM-gel coated grafts. Since hpcECM-gel induced a significantly higher endothelial cell adhesion to ePTFE than fibronectin, it represents a possible alternative for SDVG modification to improve endothelialization.

Revisiting the potential of South American rattlesnake Crotalus durissus terrificus toxins as therapeutic, theranostic and/or biotechnological agents

The potential biotechnological and biomedical applications of the animal venom components are widely recognized. Indeed, many components have been used either as drugs or as templates/prototypes for the development of innovative pharmaceutical drugs, among which many are still used for the treatment of human diseases. A specific South American rattlesnake, named Crotalus durissus terrificus, shows a venom composition relatively simpler compared to any viper or other snake species belonging to the Crotalus genus, although presenting a set of toxins with high potential for the treatment of several still unmet human therapeutic needs, as reviewed in this work. In addition to the main toxin named crotoxin, which is under clinical trials studies for antitumoral therapy and which has also anti-inflammatory and immunosuppressive activities, other toxins from the C. d. terrificus venom are also being studied, aiming for a wide variety of therapeutic applications, including as antinociceptive, anti-inflammatory, antimicrobial, antifungal, antitumoral or antiparasitic agent, or as modulator of animal metabolism, fibrin sealant (fibrin glue), gene carrier or theranostic agent. Among these rattlesnake toxins, the most relevant, considering the potential clinical applications, are crotamine, crotalphine and gyroxin. In this narrative revision, we propose to organize and present briefly the updates in the accumulated knowledge on potential therapeutic applications of toxins collectively found exclusively in the venom of this specific South American rattlesnake, with the objective of contributing to increase the chances of success in the discovery of drugs based on toxins.

Nonviral Expression of LL-37 in a Human Skin Equivalent to Prevent Infection in Skin Wounds

Inefficient autologous tissue recovery in skin wounds increases the susceptibility of patients to infections caused by multidrug resistant microorganisms, resulting in a high mortality rate. Genetic modification of skin cells has become an important field of study because it could lead to the construction of more functional skin grafts, through the overexpression of antimicrobial peptides that would prevent early contamination and infection with bacteria. In this study, we produce and evaluate human skin equivalents (HSEs) containing transfected human primary fibroblasts and keratinocytes by polyplexes to express the antimicrobial peptide LL-37. The effect of LL-37 on the metabolic activity of normal HSEs was evaluated before the construction of the transfected HSEs, and the antimicrobial efficacy against Pseudomonas aeruginosa and Staphylococcus aureus was evaluated. Subsequently, the levels of LL-37 in the culture supernatants of transfected HSEs, as well as the local expression, were determined. It was found that LL-37 treatment significantly promoted the cellular proliferation of HSEs. Furthermore, HSEs that express elevated levels of LL-37 were shown to possess histological characteristics close to the normal skin and display enhanced antimicrobial activity against S. aureus in vitro. These findings demonstrate that HSEs expressing LL-37 through nonviral modification of skin cells are a promising approach for the prevention of bacterial colonization in wounds.

Role for fibrin glue (sealant) in seroma reduction after inguinal lymphadenectomy; a randomized controlled trial

BACKGROUND

Seroma is one of the most commonly encountered morbidities after inguinal lymph node dissection (ILND). It causes much nuisance to both patients and doctors and its presence can lead to many complications. This study aimed to evaluate the role and impact of using fibrin glue to decrease seroma formation in patients undergoing ILND.

MATERIALS AND METHODS

Thirty-two patients underwent ILND for various reasons. The patients were randomly divided into two groups; 16 in each group. In one group, fibrin glue sealant was applied with a dosage of 2 ml per 100 cm² surface area. Drain placement was then performed. In the control group, only drain placement was used. Preoperative, operative and postoperative data were recorded and analyzed.

RESULTS

There was a significant reduction in the incidence of seroma formation favoring the fibrin glue group when compared to the control group (P = 0.022). There was also a significant reduction of total cumulative amount of serous fluid (P < 0.001), time to remove drains (P < 0.001), and hospital stay (P = 0.012). There was no significant difference between the two groups in occurrences of hematoma, infection or superficial skin edge necrosis.

CONCLUSION

Fibrin glue sealant has a role to play in ILND as it significantly reduced the incidence of seroma formation. Standardization of definition of seroma as well as dosage and technique of fibrin glue have to be reached in future studies to determine the true role of fibrin glue in ILND.

Soft Materials by Design: Unconventional Polymer Networks Give Extreme Properties

Hydrogels are polymer networks infiltrated with water. Many biological hydrogels in animal bodies such as muscles, heart valves, cartilages, and tendons possess extreme mechanical properties including being extremely tough, strong, resilient, adhesive, and fatigue-resistant. These mechanical properties are also critical for hydrogels' diverse applications ranging from drug delivery, tissue engineering, medical implants, wound dressings, and contact lenses to sensors, actuators, electronic devices, optical devices, batteries, water harvesters, and soft robots. Whereas numerous hydrogels have been developed over the last few decades, a set of general principles that can rationally guide the design of hydrogels using different materials and fabrication methods for various applications remain a central need in the field of soft materials. This review is aimed at synergistically reporting: (i) general design principles for hydrogels to achieve extreme mechanical and physical properties, (ii) implementation strategies for the design principles using unconventional polymer networks, and (iii) future directions for the orthogonal design of hydrogels to achieve multiple combined mechanical, physical, chemical, and biological properties. Because these design principles and implementation strategies are based on generic polymer networks, they are also applicable to other soft materials including elastomers and organogels. Overall, the review will not only provide comprehensive and systematic guidelines on the rational design of soft materials, but also provoke interdisciplinary discussions on a fundamental question: why does nature select soft materials with unconventional polymer networks to constitute the major parts of animal bodies?

Treatment of Chronic Venous Ulcers With Heterologous Fibrin Sealant: A Phase I/II Clinical Trial

Background

Heterologous fibrin sealant (HFS) consists of a fibrinogen-rich cryoprecipitate extracted from Bubalus bubalis buffalo blood and a thrombin-like enzyme purified from Crotalus durissus terrificus snake venom. This study evaluated the safety and immunogenicity of HFS, estimated the best dose, and assessed its preliminary efficacy in the treatment of chronic venous ulcers (CVU).

Methods

A phase I/II non-randomized, single-arm clinical trial was performed on 31 participants, accounting for a total of 69 active CVUs. All ulcers were treated with HFS, essential fatty acid, and Unna boot for 12 weeks. The outcomes assessed were: (1) primary safety, immunogenicity analyses, and confirmation of the lowest safe dose; (2) secondary promising efficacy by analyzing the healing process. Immunogenicity was evaluated using the serum-neutralizing (IgM and IgG) and non-neutralizing (IgA and IgE) antibody techniques against the product. The immuno-detection of IgE class antibodies was assessed using dot-blot assay before and at the end of treatment. Positive samples on dot-blot assays were subsequently analyzed by western blotting to verify the results.

Results

No severe systemic adverse events related to the use of HFS were observed. Local adverse events potentially related to treatment include ulcer pain (52%), peri-ulcer maceration (16%), peri-ulcer pruritus (12%), critical colonization (8%), peri-ulcer eczema (4%), the opening of new ulcers (4%), and increased ulcerated area 4%). Neutralizing and non-neutralizing antibodies did not show significant deviations at any of the evaluated time points. Blot assays showed that all patients presented negative immunological reactions, either before or after treatment, with the thrombin-like enzyme component. In addition, two participants showed a positive immunological reaction to the cryoprecipitate component, while another two were positive before and during treatment. Regarding the secondary outcomes of preliminary efficacy, a total healing and significant reduction of the area was observed in 47.5 and 22%, respectively. A qualitative improvement was observed in the wound beds of unhealed ulcers.

Conclusions

The investigational HFS bioproduct proved to be safe and non-immunogenic with a good preliminary efficacy for the treatment of CVU, according to the protocol and doses proposed. A multicentric phase III clinical trial will be necessary to verify these findings.

Concepts in Early Reconstruction of the Burned Hand

BACKGROUND

Early reconstruction of burn sequelae of the hand can be challenging owing to high goals for functional and aesthetic outcome. A variety of reconstructive procedures with ascending levels of complexity exists and warrants careful indication.

METHODS

In this case series, the main reconstructive techniques for reconstruction of burn defects of the hand are described, illustrated, and discussed: split thickness skin grafting (STSG) with fibrin glue, dermal matrices with STSG, distant random pattern (abdominal bridge) flap, distant pedicled flap (superficial circumflex iliac artery flap), and free microvascular tissue transfer (anterolateral thigh flap). An algorithm for decision making in the reconstructive process is proposed.

RESULTS

Split thickness skin grafting provides sufficient coverage for partial thickness defects without exposure of functional structures; fixation with fibrin glue avoids unnecessary stapling. Dermal matrices under STSG provide vascularized granulation tissue on full thickness defects and can be used as salvage procedure on functional structures. Distant random pattern or pedicled flaps provide sufficient coverage of large full thickness defects with exposed functional structures but pose some challenges regarding patient compliance and immobilization. Free tissue transfer allows tailored reconstruction of large full thickness defects with exposed functional structures and can be safely and feasibly performed. Secondary and tertiary procedures are needed with more complex techniques; if applied correctly and consequently, all methods can yield favorable functional and aesthetic outcomes.

CONCLUSIONS

Reconstruction of the burned hand may require a broad armamentarium of surgical techniques with different levels of complexity, versatility, and applicability. Excellent results can be achieved with the right procedure for the right patient.

Early Clinical Results of the Tolerability, Safety, and Efficacy of Autologous Platelet-Rich Plasma Administration in Erectile Dysfunction

Introduction

Platelet-rich plasma (PRP) is useful in the treatment of different conditions and diseases as it contains concentrated levels of many growth factors.

Aim

The aim of this study was to investigate the effectiveness of autologous PRP application in the treatment of erectile dysfunction (ED) in patients with metabolic syndrome.

Methods

In this prospective study conducted in June 2019, 31 patients with ED were included. The International Index of Erectile Function–Erectile Function domain (IIEF-EF) questionnaires were used to evaluate erectile function (EF). After administering the intracavernous autologous PRP 3 times with an interval of 15 days, IIEF-EFs were evaluated 1, 3, and 6 months later.

Main Outcome Measure

IIEF in the 1st, 3rd, and 6th months and adverse events.

Results

While the mean IIEF-EF was 18 before the application, the mean IIEF-EF was 20 in the first, third, and sixth months after the procedure (P < .001). However, even though IIEF-EF values increased numerically, median value remained within the mild-moderate classification (scores between 17 and 21). Postprocedure sexual satisfaction scores were significantly higher than preprocedure values (8 vs 6, respectively; P = .002). In the first follow-up of a patient after the 3rd injection, a 4-mm diameter fibrotic plaque was observed on the ventral side in the middle of the penis shaft.

Conclusion

In conclusion, our findings suggest that larger studies as well as placebo-controlled studies are needed to add PRP to the treatment protocol in ED.

T Taş,Çakıroğlu, E Arda, et al. Early Clinical Results of the Tolerability, Safety, and Efficacy of Autologous Platelet-Rich Plasma Administration in Erectile Dysfunction. Sex Med 2021;9:100313.

Polymeric Tissue Adhesives

Polymeric tissue adhesives provide versatile materials for wound management and are widely used in a variety of medical settings ranging from minor to life-threatening tissue injuries. Compared to the traditional methods of wound closure (i.e., suturing and stapling), they are relatively easy to use, enable rapid application, and introduce minimal tissue damage. Furthermore, they can act as hemostats to control bleeding and provide a tissue-healing environment at the wound site. Despite their numerous current applications, tissue adhesives still face several limitations and unresolved challenges (e.g., weak adhesion strength and poor mechanical properties) that limit their use, leaving ample room for future improvements. Successful development of next-generation adhesives will likely require a holistic understanding of the chemical and physical properties of the tissue-adhesive interface, fundamental mechanisms of tissue adhesion, and requirements for specific clinical applications. In this review, we discuss a set of rational guidelines for design of adhesives, recent progress in the field along with examples of commercially available adhesives and those under development, tissue-specific considerations, and finally potential functions for future adhesives. Advances in tissue adhesives will open new avenues for wound care and potentially provide potent therapeutics for various medical applications.

The Impact of Fibrin Sealant Volume on Skin Graft Contraction in a Full-Thickness Skin Graft Model

BACKGROUND

Fibrin sealant has been used for skin grafting in anatomically difficult facial areas. Although biodegradable, an excess of fibrin sealant may inhibit skin graft healing by inhibiting diffusion at the graft-recipient bed interface. The impact of fibrin sealant volume on graft healing was examined in a rat full-thickness skin graft model.

METHODS

Seventy-two full-thickness 2.5 × 2.5-cm skin grafts were used on the dorsum of male Sprague-Dawley rats. The grafts were treated with three different volumes of fibrin sealant placed onto the recipient bed: 0.0 mL or normal saline (group 1), 0.1 mL (group 2), and 0.4 mL (group 3). Graft healing and complications were assessed using digital photographs and necropsies on postoperative days 3, 7, and 21.

RESULTS

Group 3 showed the greatest graft contraction on days 3 and 21, while group 2 showed the least contraction on all 3 postoperative days (P = 0.002, 0.004, and <0.001, respectively). Histopathologic analysis showed inflammatory foreign body reactions in group 3 on days 3 and 7, and less vascular density on day 21 (P = 0.003). Group 1 showed the highest incidence of hematoma (P = 0.004).

CONCLUSION

An excess volume of fibrin sealant may produce pathologic wound contraction in skin grafting because a skin graft lacks a vascular pedicle and is highly dependent on diffusion from the host environment. Before using fibrin sealant for skin grafting in facial areas where the aesthetic outcome is important, the appropriate volume to use can be determined.

Using fibrin sealant for skin graft fixation to avoid sedation in children with burns: a prospective study

OBJECTIVE

To investigate whether a fibrin sealant, Fitrix (Sanquin Blood Supply Foundation, The Netherlands), for fixation of skin grafts in children with burn wounds is less invasive and equally effective in comparison with skin staples.

METHOD

A single-centre prospective observational cohort study was conducted. Children requiring skin grafting after burns were included and received the fibrin sealant. This group was compared with a retrospective control group of children whose skin grafts were fixed with skin staples. Study outcomes were graft take, graft dislocation, other wound complications, healing and need for sedation.

RESULTS

In the fibrin sealant and the control groups, 17 and 27 patients were included, respectively. The percentage of total body surface area (%TBSA) grafted was smaller (p=0.028) in the fibrin sealant group (median 1.0, interquartile range (IQR) 1.5 versus 2.0, IQR 2.5). There was no significant difference in graft take or wound healing. There were two graft dislocations in the fibrin sealant group and none in the control group. Other complications included a patient with graft failure in the fibrin sealant group, and another patient with a vanishing graft and wound infection in the control group. There were fewer sedations in the fibrin sealant group compared with the control group (one versus 20, p<0.0001).

CONCLUSION

The fibrin sealant used in this study was non-inferior for the fixation of skin grafts in comparison with skin staples, and avoided sedation procedures.

Use of fibrin glue in bariatric surgery: analysis of complications after laparoscopic sleeve gastrectomy on 450 consecutive patients

Laparoscopic Sleeve Gastrectomy (LSG) is one of the most performed surgical procedures in bariatric surgery. Staple line leak and bleeding are by far the two most feared complications after LSG. In this study, we retrospectively compared the efficacy of Fibrin Glue in preventing staple line leak and bleeding. From September 2019 to January 2020, 450 obese patients underwent elective LSG and were placed into groups with Fibrin Glue reinforcement (Group A) or without Fibrin Glue reinforcement (Group B). Primary endpoints were postoperative staple line leak and bleeding; while, secondary endpoints were reintervention rate, total operative time and mortality. Mean Body Mass Index (BMI) was 45.4 ± 7.9 kg/m² (range: 35.1-81.8). Mean age was 43.3 ± 11.8 years (range: 18-65). No intraoperative complications or conversion to laparotomy were reported. Mean operative time was comparable between the groups (48 ± 18 min in Group A vs 48 ± 14 min in Group B; p > 0.05). No decrease in overall postoperative complications was found in Group A (5.1% vs 7.0%; p > 0.05), but after stratification according to Clavien-Dindo classification, we found a higher rate of Grade II (0.0% vs 1.6%; p < 0.05) and Grade IIIb (0.0% vs 1%; p < 0.05) complications in group B. Our study showed that Fibrin Glue as a reinforcement method during LSG is a reliable tool, without affecting the operative time of surgery and mortality. A significant reduction in complications (Clavien-Dindo grade II and grade IIIb) was observed in patients undergoing LSG with Fibrin Glue.

Effectiveness of fibrin glue in skin graft survival: A systematic review and meta-analysis

Background

The objective of this study is to assess the current literature on the effectiveness of fibrin glue on survival of skin grafts. Fibrin glue is a possible alternative to secure skin grafts instead of traditional methods (i.e. sutures or staples).

Methods

Data Sources: MEDLINE, Scopus, Embase, Informit, CINAHL and the Cochrane Central Register of Controlled Trials, no limit on the earliest date of publication.

Study eligibility criteria

Randomised, non-randomised controlled trials and cohort studies.

Participants

and Interventions: Participants were patients with skin grafting/skin transplantation. The intervention was fibrin glue in any form (bovine, human pooled plasma or autologous) and comparator any form of affixing skin grafts (e.g. sutures or staples).

Study Appraisal and Synthesis Methods: Studies were appraised using the Cochrane risk of bias tool and assessed for clinical heterogeneity. Effect sizes were calculated and illustrated with forest plots.

Results

190 publications were narrowed to 15 relevant publications, of which eight were pooled in meta-analysis. The outcomes examined were: graft survival by percentage; graft survival reported as events; post-operative incidence of haematoma or seroma; pain reported after dressing changes via a visual analogue scale; length of stay in days (Glass's delta 2 was 0.48 95% CI 0.09, 0.97); and surgical time in minutes. Only length of stay showed a difference between groups and it favoured fibrin glue.

Conclusions

While there may be benefits to the use of fibrin glue in skin graft patients, it is difficult to conclude this from the current evidence. Limitations were significant heterogeneity in outcomes measured and exclusion off non-English papers.

•

Largest systematic review of fibrin glue in skin grafts to date.

•

Both clinical and patient reported outcomes important in assessing skin grafts.

•

Significant Improvement in length of stay for skin graft patients with fibrin glue.

•

Meta-Analysis of graft survival, pain and operative time for skin graft patients who had fibrin glue.

Chronic venous ulcers: a review on treatment with fibrin sealant and prognostic advances using proteomic strategies

Venous ulcers are the main causes of chronic lower-limb ulcers. The healing difficulties encourage the research and development of new products in order to achieve better therapeutic results. Fibrin sealant is one of these alternatives. Besides being a validated scaffold and drug delivery system, it possesses excellent healing properties. This review covered the last 25 years of the literature and showed that the fibrin sealant is used in various clinical situations to promote the healing of different types of ulcers, especially chronic ones. These are mostly venous in origin and usually does not respond to conventional treatment. Commercially, only the homologous fibrin sealants obtained from human blood are available, which are highly efficient but very expensive. The heterologous fibrin sealant is a non-commercial experimental low-cost product and easily produced due to the abundance of raw material. The phase I/II clinical trial is already completed and showed that the product is safe and promisingly efficacious for the treatment of chronic venous ulcers. In addition, clinical proteomic strategies to assess disease prognosis have been increasingly used. By analyzing liquid samples from the wounds through proteomic strategies, it is possible to predict before treatment which ulcers will evolve favorably and which ones will be difficult to heal. This prognosis is only possible by evaluating the expression of isolated proteins in exudates and analysis using label-free strategies for shotgun. Multicentric clinical trials will be required to evaluate the efficacy of fibrin sealant to treat chronic ulcers, as well as to validate the proteomic strategies to assess prognosis.

Evaluation of a cell-based osteogenic formulation compliant with good manufacturing practice for use in tissue engineering

Proper bony tissue regeneration requires mechanical stabilization, an osteogenic biological activity and appropriate scaffolds. The latter two elements can be combined in a hydrogel format for effective delivery, so it can readily adapt to the architecture of the defect. We evaluated a Good Manufacturing Practice-compliant formulation composed of bone marrow-derived mesenchymal stromal cells in combination with bone particles (Ø = 0.25 to 1 µm) and fibrin, which can be readily translated into the clinical setting for the treatment of bone defects, as an alternative to bone tissue autografts. Remarkably, cells survived with unaltered phenotype (CD73⁺, CD90⁺, CD105⁺, CD31^-, CD45^-) and retained their osteogenic capacity up to 48 h after being combined with hydrogel and bone particles, thus demonstrating the stability of their identity and potency. Moreover, in a subchronic toxicity in vivo study, no toxicity was observed upon subcutaneous administration in athymic mice and signs of osteogenesis and vascularization were detected 2 months after administration. The preclinical data gathered in the present work, in compliance with current quality and regulatory requirements, demonstrated the feasibility of formulating an osteogenic cell-based tissue engineering product with a defined profile including identity, purity and potency (in vitro and in vivo), and the stability of these attributes, which complements the preclinical package required prior to move towards its use of prior to its clinical use.

A Novel Surgical Technique for Resuspension of Digital Pulp Tissue after Degloving Injuries

Adherence of pulp tissue to the underlying distal phalanx is required for fundamental actions including grip, proprioception, and fine motor skills. Disruption of the fibrous septa causes sliding between the distal phalanx and overlying soft tissues, hindering basic hand function. The authors present a novel surgical technique in which the fibrous pulp septa are resuspended to the distal phalanx with bone anchors and sclerosing agents after a closed degloving injury.

Bioengineering Vascular Networks to Study Angiogenesis and Vascularization of Physiologically Relevant Tissue Models in Vitro

Angiogenesis assays are essential for studying aspects of neovascularization and angiogenesis and investigating drugs that stimulate or inhibit angiogenesis. To date, there are several in vitro and in vivo angiogenesis assays that are used for studying different aspects of angiogenesis. Although in vivo assays are the most representative of native angiogenesis, they raise ethical questions, require considerable technical skills, and are expensive. In vitro assays are inexpensive and easier to perform, but the majority of them are only two-dimensional cell monolayers which lack the physiological relevance of three-dimensional structures. Thus, it is important to look for alternative platforms to study angiogenesis under more physiologically relevant conditions in vitro. Accordingly, in this study, we developed polymeric vascular networks to be used to study angiogenesis and vascularization of a 3D human skin model in vitro. Our results showed that this platform allowed the study of more than one aspect of angiogenesis, endothelial migration and tube formation, in vitro when combined with Matrigel. We successfully reconstructed a human skin model, as a representative of a physiologically relevant and complex structure, and assessed the suitability of the developed in vitro platform for studying endothelialization of the tissue-engineered skin model.

Lipoconstruct surface topography grating size influences vascularization onset in the dorsal skinfold chamber model

After skin tissue injury or pathological removal, vascularization timing is paramount in graft survival. As full thickness skin grafts often fail to become perfused over larger surfaces, split-thickness grafts are preferred and can be used together with biomaterials, which themselves are non-angiogenic. One way of promoting vascular ingrowth is to "pre-vascularize" an engineered substitute by introducing endothelial cells (ECs). Since it has been previously demonstrated that surface structured biomaterials have an effect on wound healing, skin regeneration, and fibrosis reduction, we proposed that a microvascular-rich lipoconstruct with anisotropic topographical cues could be a clinically translatable vascularization approach. Murine lipofragments were formed with three polydimethylsiloxane molds (flat, 5 µm, and 50 µm parallel gratings) and implanted into the dorsal skinfold chamber of male C57BL/6 mice. Vascular ingrowth was observed through intravital microscopy over 21 days and further assessed by histology and protein identification. Our investigation revealed that topographical feature size influenced the commencement of neovascular ingrowth, with 5 µm gratings exhibiting early construct perfusion at 3 days post-operation, and 50 µm being delayed until day 5. We therefore postulate that surface structured lipoconstructs may serve as an easily obtained and produced construct suitable for providing soft tissue and ECs to tissue defects. STATEMENT OF SIGNIFICANCE: Skin graft failures due to inadequate or uneven perfusion frequently occur and can be even more complicated in deep, difficult to heal wounds, or bone coverage. In complex injuries, biomaterials are often used to cover bone structures with a standard split thickness graft; however, perfusion can take up to 3 weeks. Thus, any means to promote faster and uniform vascularization could significantly reduce healing time, as well as lower patient down-time. As pre-vascularized constructs have reported success in research, we created a cost-efficient, translatable method with no additional laboratory time as adipose tissue can be harvested and used immediately. We further used surface topography as an aspect to modulate construct perfusion, which has been reported for the first time here.

Double crosslinked HLC-CCS hydrogel tissue engineering scaffold for skin wound healing

Skin defects caused by various reasons are currently common clinical problems. At present, hydrogels have been proposed as tissue-engineered skin scaffolds to regenerate the tissues of the defect. We used human-like collagen (HLC), which was isolated and purified after high-density fermentation of recombinant E. coli BL21 The gel uses HLC and carboxymethylated chitosan (CCS) as raw materials and combines enzyme-chemical double cross-linking technology to form a three-dimensional porous network structure that mimics the human extracellular matrix, providing attachment points and nutrients for cell growth and proliferation. For comparison, we used a common hydrogel raw material, gelatin, to prepare a hydrogel in the same way. The experimental results show that the HLC-CCS skin scaffold hydrogel has good mechanical properties, high porosity and good histocompatibility. And full-thickness skin defect repair experiments show that this hydrogel has a good ability to promote skin tissue regeneration at the wound. In summary, this HLC-based double-crosslinked hydrogel can be used as a project strategy for skin defect repair.

Fibrin Glue Used Successfully in Peritoneal Dialysis Catheter Leakage in Children

Background

Acute renal failure in infants and small children is generally treated with peritoneal dialysis (PD). Dialysis has to be started immediately after catheter implantation. Early dialysate leakage can complicate the effectiveness of dialysis. Fibrin glue applied to the external part of the tunnel may stop dialysate leakage and eliminate the need for surgical intervention. The use of fibrin glue in the treatment of PD catheter leakage in children was studied.

Methods

Fibrin glue was used in 8 children (age 0.8 – 57 months) on PD in whom dialysate leakage was seen during the first 24 to 48 hours after catheter insertion. The dialysis volume initially administered was 20 mL/kg body weight. Fibrin glue (1 mL) was applied to the external part of the subcutaneous catheter tunnel through the exit site, as close to the cuff as possible. The occurrence of dialysate leakage and complications such as exit-site or tunnel infection and peritonitis were evaluated.

Results

Nine single-cuff straight Tenckhoff catheters were implanted in 8 children. In 5 cases, no subcutaneous tunnel was created. One child had catheter replacement due to obstruction of the catheter; on both occasions, catheter leakage was seen and treated with fibrin glue. In all 8 patients, no relapse of dialysate leakage was seen after application of the fibrin glue. During the time of PD, exit-site infections, tunnel infections, and peritonitis did not occur.

Conclusion

Fibrin glue is a successful, simple, and safe substance for the treatment of peritoneal dialysate leakage in infants and small children with acute renal failure treated with PD.

Fibrin Matrices as (Injectable) Biomaterials: Formation, Clinical Use, and Molecular Engineering

This review focuses on fibrin, starting from biological mechanisms (its production from fibrinogen and its enzymatic degradation), through its use as a medical device and as a biomaterial, and finally discussing the techniques used to add biological functions and/or improve its mechanical performance through its molecular engineering. Fibrin is a material of biological (human, and even patient's own) origin, injectable, adhesive, and remodellable by cells; further, it is nature's most common choice for an in situ forming, provisional matrix. Its widespread use in the clinic and in research is therefore completely unsurprising. There are, however, areas where its biomedical performance can be improved, namely achieving a better control over mechanical properties (and possibly higher modulus), slowing down degradation or incorporating cell-instructive functions (e.g., controlled delivery of growth factors). The authors here specifically review the efforts made in the last 20 years to achieve these aims via biomimetic reactions or self-assembly, as much via formation of hybrid materials.

The clot thickens: Autologous and allogeneic fibrin sealants are mechanically equivalent in an ex vivo model of cartilage repair

Fibrin sealants are commonly used in cartilage repair surgeries to adhere cells or grafts into a cartilage defect. Both autologous and commercial allogeneic fibrin sealants are used in cartilage repair surgeries, yet there are no studies characterizing and comparing the mechanical properties of fibrin sealants from all-autologous sources. The objectives of this study were to investigate (i) the effect of fibrinogen and thrombin sources on failure mechanics of sealants, and (ii) how sealants affect the adhesion of particulated cartilage graft material (BioCartilage) to surrounding cartilage under physiological loading. Allogeneic thrombin and fibrinogen were purchased (Tisseel), and autologous sources were prepared from platelet-rich plasma (PRP) and platelet-poor plasma (PPP) generated from human blood. To compare failure characteristics, sealants were sandwiched between cartilage explants and pulled to failure. The effect of sealant on the adhesion of BioCartilage graft to cartilage was determined by quantifying microscale strains at the graft-cartilage interface using an in vitro cartilage defect model subjected to shear loading at physiological strains well below failure thresholds. Fibrinogen sources were not equivalent; PRP fibrinogen created sealants that were more brittle, failed at lower strains, and resulted in sustained higher strains through the graft-cartilage interface depth compared to PPP and allogeneic sources. PPP clotted slower compared to PRP, suggesting PPP may percolate deeper into the repair to provide more stability through the tissue depth. There was no difference in bulk failure properties or microscale strains at the graft-cartilage interface between the purely autologous sealant (autologous thrombin + PPP fibrinogen) and the commercial allogeneic sealant. Clinical Significance: All-autologous fibrin sealants fabricated with PPP have comparable adhesion strength as commercial allogeneic sealants in vitro, whereas PRP creates an inferior all-autologous sealant that sustains higher strains through the graft-cartilage interface depth.

Healing of Chronic Wounds: An Update of Recent Developments and Future Possibilities

Chronic wounds are the result of disruptions in the body's usual process of healing. They are not only a source of significant pain and discomfort but also, more importantly, an unguarded port of entry for pathogens into the body. While our current understanding of this phenomenon is far from complete, findings in physiological patterns and advancements in wound healing technologies have helped develop wound management and healing solutions to this long-standing medical challenge. This review presents an overview of known wound healing mechanics, abnormalities that lead to chronic wounds, and a summary of established and new wound healing technologies. Various approaches to heal wounds are discussed, from dermal replacements to advanced biomaterial-based treatments, from cell-, synthetic-, and composite-based approaches to preclinical approaches, which make developing such products possible. While tested breakthrough products are described, the authors focused more on recently developed innovations, which are at varying stages of maturity. The review concludes with a note on future perspectives and opinions on where the field and industry are headed and where they should be. Impact Statement Wound healing is an important area of research and clinical practice, and has captured the attention of tissue engineers since the nascent beginnings of the discipline. Tissue-engineered skin was the first FDA-approved product, achieved in 1996. Despite this success, and the passage of time, healing wounds, particularly chronic wounds, remains a vexing challenge. This comprehensive review article will provide readers with a synopsis of current issues, research approaches, animal models, technologies, and products that span the continuum from early development to clinical studies, in the hope of fueling new interests and ideas to overcome this long-standing medical challenge.

Adhesive Cements That Bond Soft Tissue Ex Vivo

The aim of the present study was to evaluate the soft tissue bond strength of a newly developed, monomeric, biomimetic, tissue adhesive called phosphoserine modified cement (PMC). Two types of PMCs were evaluated using lap shear strength (LSS) testing, on porcine skin: a calcium metasilicate (CS1), and alpha tricalcium phosphate (αTCP) PMC. CS1 PCM bonded strongly to skin, reaching a peak LSS of 84, 132, and 154 KPa after curing for 0.5, 1.5, and 4 h, respectively. Cyanoacrylate and fibrin glues reached an LSS of 207 kPa and 33 kPa, respectively. αTCP PMCs reached a final LSS of ≈110 kPa. In soft tissues, stronger bond strengths were obtained with αTCP PMCs containing large amounts of amino acid (70-90 mol%), in contrast to prior studies in calcified tissues (30-50 mol%). When αTCP particle size was reduced by wet milling, and for CS1 PMCs, the strongest bonding was obtained with mole ratios of 30-50% phosphoserine. While PM-CPCs behave like stiff ceramics after setting, they bond to soft tissues, and warrant further investigation as tissue adhesives, particularly at the interface between hard and soft tissues.

Hydrogels for Liver Tissue Engineering

Bioengineered livers are promising in vitro models for drug testing, toxicological studies, and as disease models, and might in the future be an alternative for donor organs to treat end-stage liver diseases. Liver tissue engineering (LTE) aims to construct liver models that are physiologically relevant. To make bioengineered livers, the two most important ingredients are hepatic cells and supportive materials such as hydrogels. In the past decades, dozens of hydrogels have been developed to act as supportive materials, and some have been used for in vitro models and formed functional liver constructs. However, currently none of the used hydrogels are suitable for in vivo transplantation. Here, the histology of the human liver and its relationship with LTE is introduced. After that, significant characteristics of hydrogels are described focusing on LTE. Then, both natural and synthetic materials utilized in hydrogels for LTE are reviewed individually. Finally, a conclusion is drawn on a comparison of the different hydrogels and their characteristics and ideal hydrogels are proposed to promote LTE.

Functional Skin Grafts: Where Biomaterials Meet Stem Cells

Skin tissue engineering has attained several clinical milestones making remarkable progress over the past decades. Skin is inhabited by a plethora of cells spatiotemporally arranged in a 3-dimensional (3D) matrix, creating a complex microenvironment of cell-matrix interactions. This complexity makes it difficult to mimic the native skin structure using conventional tissue engineering approaches. With the advent of newer fabrication strategies, the field is evolving rapidly. However, there is still a long way before an artificial skin substitute can fully mimic the functions and anatomical hierarchy of native human skin. The current focus of skin tissue engineers is primarily to develop a 3D construct that maintains the functionality of cultured cells in a guided manner over a period of time. While several natural and synthetic biopolymers have been translated, only partial clinical success is attained so far. Key challenges include the hierarchical complexity of skin anatomy; compositional mismatch in terms of material properties (stiffness, roughness, wettability) and degradation rate; biological complications like varied cell numbers, cell types, matrix gradients in each layer, varied immune responses, and varied methods of fabrication. In addition, with newer biomaterials being adopted for fabricating patient-specific skin substitutes, issues related to escalating processing costs, scalability, and stability of the constructs under in vivo conditions have raised some concerns. This review provides an overview of the field of skin regenerative medicine, existing clinical therapies, and limitations of the current techniques. We have further elaborated on the upcoming tissue engineering strategies that may serve as promising alternatives for generating functional skin substitutes, the pros and cons associated with each technique, and scope of their translational potential in the treatment of chronic skin ailments.

Light-Activated Tissue-Integrating Sutures as Surgical Nanodevices

Sutures are typically the primary means of soft tissue repair in surgery and trauma. Despite their widespread use, sutures do not result in immediate sealing of approximated tissues, which can result in bacterial infection and leakage. Nonabsorbable sutures and staples can be traumatic to tissue, and the trauma can be exacerbated by their subsequent removal. Use of cyanoacrylate glues is limited because of their brittleness and toxicity. In this work, laser-activated tissue-integrating sutures (LATIS) are described as novel nanodevices for soft tissue approximation and repair. Incorporation of gold nanorods within fibers generated from collagen result in LATIS fibers which demonstrate robust photothermal responses following irradiation with near infrared laser light. Compared to conventional sutures, LATIS fibers result in greater biomechanical recovery of incised skin in a mouse model of skin closure after spine surgeries. Histopathology analyses show improved repair of the epidermal gap in skin, which indicate faster tissue recovery using LATIS. The studies indicate that LATIS-facilitated approximation of skin in live mice synergizes the benefits of conventional suturing and laser-activated tissue integration, resulting in new approaches for faster sealing, tissue repair, and healing.

Multifunctional Biomedical Adhesives

Currently available biomedical adhesives are mainly engineered to have one function (i.e., providing mechanical support for the repaired tissue). To improve the performance of existing bioadhesives and broaden their applications in medicine, numerous multifunctional bioadhesives are reported in the literature. These adhesives can be categorized as passive or active by design. Passive multifunctional bioadhesives contain inherent compositions and structural designs that can carry out additional functions without added external influences. These adhesives exhibit new functionalities such as antimicrobial properties, self-healing abilities, the ability to promote cellular ingrowth, and the ability to be reshaped. Conversely, active multifunctional bioadhesives respond to environmental changes (e.g., pH, temperature, electricity, light, and biomolecule concentration), which initiate a change in the adhesive to release encapsulated drugs or to activate or deactivate the bioadhesive for interfacial binding. This review article highlights recent advances in multifunctional bioadhesives.

Skin Graft Fixation Using Hydrofiber (Aquacel® Extra)

BACKGROUND

The traditional method of skin graft fixation is with tie-over bollus dressing. The use of splints in the extremities for skin graft fixation is a common practice. However, these splints are heavy and uncomfortable and contribute considerably to our overall medical waste. Hydrofiber (Aquacel Extra) has a strong fluid absorption property and fixates well to the underlying wound once applied. In this study, we used hydrofiber for fixation, avoiding the use of splints after skin grafting.

METHODS

A total of 56 patients reconstructed with split-thickness skin graft that was fixated only with hydrofiber between March 2015 and March 2016 were included in this retrospective study.

RESULTS

There were 44 men and 12 women with a mean age of 61 ± 18 years. The defect size ranged from 1 × 1 cm for fingertips to 30 × 12 cm for lower limb defects. The average defect size was 61 ± 78 cm. The mean skin graft take was 96% ± 6%. Because splints were not required, we saved around 48 kg of medical waste over the space of 1 year.

CONCLUSIONS

The use of hydrofiber for skin graft fixation was effective and technically very simple. Splints were not required with this method, decreasing the medical waste created and increasing patient comfort. We suggest that this is an excellent alternative for skin graft fixation while at the same time decreasing our carbon footprint as surgeons.

In vivo evaluation of an electrospun gelatin nonwoven mat for regeneration of epithelial tissues

One major objective in epithelial tissue engineering is to identify a suitable biomaterial that supports epithelial tissue formation. Therefore, the purpose of this study is to elucidate a novel electrospun gelatin nonwoven mat (NWM) for epithelial tissue engineering purposes in vivo. This NWM was seeded with either human gingival keratinocytes (GK, in coculture with gingival fibroblast) or human skin epithelial keratinocytes (EK, in coculture with skin dermal fibroblasts). These constructs were ex vivo cultured for 4 days before subcutaneous implantation into athymic nude mice. After 7 days, the constructs were explanted and investigated by immunohistology. Our results show that GK form a stratified epithelium on the surface of the NWM, mostly independent of a fibroblastic counterpart. Like native mucosa, the regenerated epithelium showed expression of epidermal growth factor receptor, cytokeratin-14 and -1, and involucrin. Only the expression of the basement membrane constituent laminin 5 was more pronounced in cocultures. Comparing GK and skin EK, we found that skin EK form a less developed epithelial tissue. Furthermore, the NWM allows not only for epithelial tissue formation by GK, but also for infiltration of human fibroblasts and mouse immune cells, thus representing a biomaterial with potential regenerative capacity for oral mucosa tissue engineering applications. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1605-1614, 2019.

Fibrin glue as a local drug-delivery system for bacteriophage PA5

Fibrin glue has been used clinically for decades in a wide variety of surgical specialties and is now being investigated as a medium for local, prolonged drug delivery. Effective local delivery of antibacterial substances is important perioperatively in patients with implanted medical devices or postoperatively for deep wounds. However, prolonged local application of antibiotics is often not possible or simply inadequate. Biofilm formation and antibiotic resistance are also major obstacles to antibacterial therapy. In this paper we test the biocompatibility of bacteriophages incorporated within fibrin glue, track the release of bacteriophages from fibrin scaffolds, and measure the antibacterial activity of released bacteriophages. Fibrin glue polymerized in the presence of the PA5 bacteriophage released high titers of bacteriophages during 11 days of incubation in liquid medium. Released PA5 bacteriophages were effective in killing Pseudomonas aeruginosa PA01. Overall, our results show that fibrin glue can be used for sustained delivery of bacteriophages and this strategy holds promise for many antibacterial applications.

Systematic review of fibrin glue in burn wound reconstruction

Background

In the reconstruction of burns using split-skin grafts (SSGs), fibrin glue can be used to improve graft take and reduce haematoma formation, although the efficacy and cost-effectiveness are unknown. This systematic review evaluated outcomes of fibrin glue compared with conventional SSG attachment techniques. Outcomes of interest included SSG take, haematoma formation, patient satisfaction and cost-effectiveness.

Methods

This PROSPERO-registered review was performed in accordance with the Cochrane Handbook for Systematic Reviews of Interventions and PRISMA statement. Embase, PubMed, Cochrane and ClinicalTrial.gov databases were searched systematically. Observational and experimental studies comparing fibrin glue with other methods of SSG attachment in burn wounds were included. Risk of bias was assessed using the Cochrane risk-of-bias and Risk of Bias In Non-Randomized Studies – of Intervention tools. The quality of the evidence was assessed using the GRADE tool.

Results

Two RCTs and four observational studies were included. Graft take at day 5 was not significantly different between groups (3 studies, 183 individuals). Fibrin glue significantly reduced the risk of postoperative haematoma in two studies and reduced patient-reported pain in two studies, with suggested cost savings in four studies. All studies were at risk of methodological bias and the quality of the evidence was universally very low.

Conclusion

As the evidence is sparse, the quality very low and the risk of bias significant both within and across studies, it is not possible to make any recommendations regarding the use of fibrin glue in burn wounds.

Platelet Rich Plasma Enhancement of Skin Regeneration in an ex-vivo Human Experimental Model

This study reports on the development of an original, ex-vivo wounded skin culture protocol using autologous Platelet Rich Plasma (PRP) and enriched Dulbecco's Modified Eagle's Medium (DMEM). Human skin samples obtained from specimens harvested during reduction mammoplasty procedures, were injured in their central portion—to create a standard wound—and cultured under three different conditions:

– enriched DMEM with saline solution in the central wound (control)

– enriched DMEM with the same medium in the central wound

– enriched DMEM plus 2.5% autologous PRP, with the same PRP added medium in the central wound.

Morphological analysis was carried out at 0 h (T₀) and on days 1, 3, 5 and 10 (T₁-T₃-T₅-T₁₀) using Hematoxylin and Eosin; Masson's trichrome staining; Weigert staining and Ki-67 staining to identify the skin histological features in the different experimental conditions. The combination of DMEM and PRP allowed a favorable modulation of the epithelial cells and fibroblasts proliferation, and a relevant anti-inflammatory action. PRP also demonstrated an inhibitory effect on both the collagen and elastic fibers' de-structuration and a favorable modulation of the re-organization of these fibers. The step by step histological and immune-histo-chemical regenerative effects of PRP on human skin wound repair and regeneration process was observed over a period of 10 days.