Evaluation of a novel biodegradable polymer for the generation of a dermal matrix

Acellular dermal matrices in reconstructive surgery; history, current implications and future perspectives for surgeons

Large-scale defects of body in the reconstructive surgical practice, and the helplessness of their repair with autologous tissues, have been an important factor in the development of artificial biological products for the temporary, definitive, or staged repair of these defects. A major advance in the field of plastic and other reconstructive surgery in this regard has been the introduction and successful use of acellular dermal matrices (ADMs). In recent years, not only the type of tissue from which ADMs are produced, product range, diversity and areas of use have increased, but their use in reconstructive fields, especially in post oncologic breast surgery, has become highly regarded and this has favored ADMs to be a potential cornerstone in specific and well-defined surgical fields in future. It is essential that reconstructive surgeons become familiar with some of the ADM’s as well as the advantages and limitations to their use. This review not only provides basic science and clinical evidence of the current use of ADMs in wide range of surgical fields but also targets to keep them as an important backdrop in the armamentarium of reconstructive surgeons. Brief considerations of possible future directions for ADMs are also conducted in the end.

Novosorb Biodegradable Temporizing Matrix for Reconstruction of Complex Upper-Extremity Wounds

Purpose

Dermal matrices can be used in management of upper-extremity wounds to create vascularized wound beds in the setting of exposed bone or tendon. Early outcomes of Novosorb biodegradable temporizing matrix (BTM) demonstrated success when used in the treatment of complex wounds. We hypothesize that BTM is effective for reconstruction of upper-extremity wounds.

Methods

A retrospective review was performed for patients who underwent reconstruction of upper-extremity wounds with BTM between January 2017 and May 2022.

Results

In total, 51 patients (39 males and 12 females) were included. Wound etiology included trauma (n = 30), burn (n = 12), infection (n = 8), and vasopressor-related injury (n = 1). The average size of BTM was 162.5 cm2, and the average time from BTM application to wound closure was 90.1 days. Twenty-seven (52.9%) patients required skin grafting, whereas 20 (39.2%) did not and re-epithelialized spontaneously. Those who did not require skin grafting had significantly smaller wound sizes compared to those who required skin grafting (58.5 cm2 vs 248.6 cm2; P = .002). Complications occurred in 14 patients, including infection (n = 5), fluid collection (n = 5), and template dehiscence (n = 4). Wound closure was successful in 92% of patients.

Conclusions

Novosorb BTM is effective for the management of upper-extremity wounds with exposed bone and tendon.

Clinical relevance

In the management of complex upper-extremity wounds with exposed bone and tendon, even when devoid of paratenon or periosteum, Novosorb BTM provides a safe and effective alternative to more complex reconstructive options.

In Vivo Formation of Adrenal Organoids in a Novel Porcine Model of Adrenocortical Cell Transplantation

Recognizing the limitations of current therapies for Addison's disease, novel treatments that replicate dynamic physiologic corticosteroid secretion, under control of ACTH, are required. The aim of these experiments was to evaluate the feasibility of adrenocortical cell transplantation (ACT) in a large animal model, adapting methods successfully used for intracutaneous pancreatic islet cell transplantation, using a fully biodegradable temporizing matrix. Autologous porcine ACT was undertaken by bilateral adrenalectomy, cell isolation, culture, and intracutaneous injection into a skin site preprepared using a biodegradable temporizing matrix (BTM) foam. Hydrocortisone support was provided during adrenocortical cell engraftment and weaned as tolerated. Blood adrenocortical hormone concentrations were monitored, and the transplant site was examined at endpoint. Outcome measures included cellular histochemistry, systemic hormone production, and hydrocortisone independence. Transplanted adrenocortical cells showed a capability to survive and proliferate within the intracutaneous site and an ability to self-organize into discrete tissue organoids with features of the normal adrenal histologic architecture. Interpretation of systemic hormone levels was confounded by the identification of accessory adrenals and regenerative cortical tissue within the adrenal bed postmortem. Corticosteroids were unable to be completely ceased. ACT in a large animal model has not previously been attempted, yet it is an important step toward clinical translation. These results demonstrate rhe potential for ACT based on the development of adrenal organoids at the BTM site. However, the inability to achieve clinically relevant systemic hormone production suggests insufficient function, likely attributable to insufficient cells through delivered dose and subsequent proliferation.

Outcomes of Biodegradable Temporizing Matrix for Soft Tissue Reconstruction of the Hand and Extremities

Background

NovoSorb biodegradable temporizing matrix (BTM) is a novel, bilayer, synthetic skin substitute made of biodegradable polyurethane foam covered with a sealing membrane. BTM has demonstrated excellent outcomes in burn literature; however, few studies have been published for hand and extremity soft tissue reconstruction.

Methods

All patients who underwent extremity reconstruction with BTM from 2018 to 2023 were reviewed. Demographics, presentations, and clinical outcomes were recorded.

Results

A total of 86 cases from 54 patients (53.7% pediatric; age range: 0-81 years) were included. Common indications included trauma (36%), infection (18.6%), and malignancy (11.6%). BTM was placed over exposed tendon (38.4%), bone (19%), joints (12.8%), nerves (8.1%), and/or blood vessels (7%). BTM served as temporary wound coverage in 26 cases. Complications included hematoma (8.1%), infection (4.7%), and spontaneous delamination (4.7%). Wound closure was successfully obtained without flap use in 93.3%. Poor BTM take was associated with peripheral vascular disease, hypertension, immunosuppression, and BTM hematoma and infection (<0.05).

Conclusion

This study contributes to the growing body of evidence favoring BTM use in challenging reconstructive cases. Although prospective comparative studies are forthcoming, BTM likely has broad applications in reconstructive surgery.

The use of biodegradable temporising matrix (BTM) for facial unit reconstruction with adjuvant radiotherapy-A case study

Synthetic Biodegradable Temporising Matrix (BTM, NovoSorb; PolyNovo Biomaterials Pty Ltd, Port Melbourne, Victoria, Australia) has proven useful in the resurfacing of large burns,1 necrotising infection debridement2 and tumour excision with exposed bone.3 We present a case report of a large BCC invading three aesthetic subunits of the face which was successfully reconstructed with BTM, split-thickness skin graft with subsequent adjuvant radiotherapy due to the high risk nature of the BCC. We present our series of images illustrating the timeline of BTM, and the ability to achieve a good skin colour match with minimal contour deformity, even in the event of post operative radiotherapy use.

NovoSorb® Biodegradable Temporising Matrix (BTM): What we learned from the first 300 consecutive cases

INTRODUCTION

Extensive full-thickness soft-tissue defects remain a challenge in reconstructive surgery. NovoSorb® Biodegradable Temporising Matrix (BTM) represents a novel dermal substitute and was evaluated in wounds deriving from different aetiologies and to highlight risk factors for poor take rates.

METHODS

All patients treated with BTM at our department between March 2020 and October 2022 were included. Differences in univariate and linear regression models identified predictors and risk factors for take rates of BTM and split-thickness skin grafts (STSG).

RESULTS

Three hundred patients (mean age 54.2 ± 20.1 years, 66.3% male, 59.7% burns, 19.7% trauma and 20.6% others) were evaluated. Mean take rates of BTM and STSG after BTM delamination were 82.7 ± 25.2% and 86.0 ± 22.6%, respectively. Multiple regression analyses showed that higher body mass index (BMI, OR 0.43, 95% CI 0.86, -0.01, p = 0.44), prior allograft transplantation (OR 15.12, 95% CI 26.98, -3.31, p = 0.041), longer trauma-to-BTM-application intervals (OR 0.01, 95% CI 0.001, -0.001, p = 0.038), positive wound swabs before BTM (OR 7.15, 95% CI 13.50, -0.80, p = 0.028) and peripheral artery disease (OR 10.80, 95% CI 18.63, -2.96, p = 0.007) were associated with poorer BTM take. Higher BMI (OR 0.40, 95% CI 0.76, -0.08, p = 0.026), increasing BTM graft surface areas (OR 0.58, 95% CI -1.00, -0.17, p = 0.005), prior allograft (OR 12.20, 95% CI -21.99, -2.41, p = 0.015) or autograft transplantations (OR 22.42, 95% CI 38.69, -6.14, p = 0.001), tumour as the aetiology of the wound (OR 37.42, 95% CI 57.41, -17.83, p = 0.001), diabetes (OR 6.64, 95% CI 12.80, -0.48, p = 0.035) and impaired kidney function (OR 5.90, 95% CI 10.94, -0.86, p = 0.021) were associated with poorer STSG take after delamination of BTM, whereas higher BTM take rates were associated with better STSG take (OR 0.40, 95% CI 0.31,0.50, p < 0.001).

CONCLUSION

Extensive complex wounds of different aetiologies unsuitable for immediate STSG can be successfully reconstructed by means of two-staged BTM application and subsequent skin grafting. Importantly, presence of wound contamination or infection and prior allograft coverage appear to jeopardise good BTM and STSG take.

The Application of a Synthetic Biodegradable Temporizing Matrix in Extensive Burn Injury: A Unicenter Experience of 175 Cases

Objectives: Addressing extensive and deep burn wounds poses considerable challenges for both patients and surgeons. The NovoSorb® Biodegradable Temporizing Matrix (BTM) emerged as a novel dermal substitute and has been subjected to evaluation in large burn wound cases, with a specific focus on identifying risk factors associated with suboptimal take rates. Methods: All patients with burn wounds greater than 10% body surface that underwent BTM treatment between March 2020 and November 2023 were eligible for inclusion. Univariate analyses and linear regression models were employed to discern risk factors and predictors influencing the take rates of both the BTM and split-thickness skin grafts (STSGs). Results: A total of 175 patients (mean age 56.2 ± 19.8 years, 70.3% male) were evaluated. The mean take rates of the BTM and STSGs were 82.0 ± 24.7% and 87.3 ± 19.0%, respectively. There were significant negative correlations between BTM take and the number of surgeries before BTM application (r = -0.19, p = 0.01), %TBSA and STSG take (r = -0.36, p = <0.001) and significant positive correlations between BTM and STSG take (r = 0.41, p ≤ 0.001) in addition to NPWT and STSG take (r = 0.21, p = 0.01). Multivariate regression analyses showed that a larger number of surgeries prior to BTM application (OR -3.41, 95% CI -6.82, -0.03, p = 0.04) was associated with poorer BTM take. Allograft treatment before BTM application (OR -14.7, 95% CI -23.0, -6.43,p = 0.01) and failed treatment with STSG before BTM application (OR -20.8, 95% CI -36.3, -5.23, p ≤ 0.01) were associated with poorer STSG take, whereas higher BTM take rates were associated with overall higher STSG take (OR -0.15, 95% 0.05, 0.26, p = 0.01). The Meek technique was used in 24 patients and showed similar take rates (BTM: 76.3 ± 28.0%, p = 0.22; STSG: 80.7 ± 21.1, p = 0.07). Conclusions: This study summarizes our findings on the application of a BTM in the context of large burn wounds. The results demonstrate that successful treatment can be achieved even in patients with extensive burns, resulting in satisfying take rates for both the BTM and STSG. The data underscore the importance of promptly applying a BTM to debrided wounds and indicate good results when using Meek.

Comparative Analysis of Animal-Derived vs Fully Synthetic Acellular Dermal Matrices in Reconstructive Surgery: An Examination of Clinical, Aesthetic, and Economic Measures

INTRODUCTION

The fully synthetic skin substitute, NovoSorb Biodegradable Temporizing Matrix (BTM), may be a cost-effective alternative to the animal-derived Integra Dermal Regeneration Template (IDRT). However, the current literature insufficiently compares the two. Therefore, our study compared clinical, aesthetic, and economic outcomes in treating soft tissue wounds with IDRT, an animal-derived template, vs BTM, a fully synthetic template.

METHODS

Our single-center retrospective study compared outcomes of 26 patient cases treated with BTM (57.7%) or IDRT (42.3%) during 2011-2022.

RESULTS

The mean surgery time was significantly shorter in BTM cases (1.632 ± 0.571 hours) compared with IDRT cases (5.282 ± 5.102 hours, P = 0.011). Median postoperative hospital stay was notably shorter for BTM placement than IDRT placement (0.95 vs 6.60 days, P = 0.003). The median postoperative follow-up length approached a shorter duration in the BTM group (P = 0.054); however, median follow-up visits were significantly lower in the BTM group compared with the IDRT group (5 vs 14, P = 0.012). The median duration for complete wound closure was shorter for BTM (46.96 vs 118.91 days, P = 0.011). Biodegradable Temporizing Matrix demonstrated a notably lower infection rate (0.0%) compared with IDRT (36.4%, P = 0.022). Integra Dermal Regeneration Template exhibited higher wound hypertrophy rates (81.8%) than BTM (26.7%, P = 0.015). Revisionary surgeries were significantly more frequent in the BTM group (P < 0.001). Failed closure, defined as requiring one or more attempts, exhibited a significant difference, with a higher risk in the IDRT group (26.7%) compared with BTM (6.7%, P = 0.003). Biodegradable Temporizing Matrix showed a lower mean Vancouver Scar Scale adjusted fraction (0.279) compared with IDRT (0.639, P < 0.001). Biodegradable Temporizing Matrix incurred lower costs compared with IDRT but displayed a lower mean profit per square centimeter ($10.63 vs $22.53, P < 0.001).

CONCLUSION

Economically, although the net profit per square centimeter of dermal template may favor IDRT, the ancillary benefits associated with BTM in terms of reduced hospital stay, shorter surgery times, fewer follow-up visits, and lower revisionary surgery rates contribute substantially to overall cost-effectiveness. Biodegradable Temporizing Matrix use reflects more efficient resource use and potential cost savings, aligning with broader trends in healthcare emphasizing value-based and patient-centered care.

Upper Extremity Wounds Treated with Biodegradable Temporizing Matrix versus Collagen-Chondroitin Silicone Bilayer

Objective  This study aims to compare outcomes between Novosorb Biodegradable Temporizing Matrix (BTM) and Integra collagen-chondroitin silicone for upper-extremity wound reconstruction. Methods  This retrospective study analyzed adult patients who underwent wound reconstruction with either BTM or Integra at our institution between 2015 and 2020. Results  Forty-eight patients were included: 31 (64.6%) BTM and 17 (35.4%) Integra. Mean age was 44.0 (range: 18-68) years. Age, race, sex, smoking, comorbidities, and defect size were similar between groups. Wound etiologies included 12 (25.0%) burn, 22 (45.8%) trauma, and others. Median template size was 133 cm 2 for BTM and 104 cm 2 for Integra ( p  = 0.526). Skin grafting was performed after 14 (45.2%) and 14 (82.4%) wounds treated with BTM and Integra, respectively ( p  = 0.028). Template complications of infection and dehiscence were comparable. Skin-graft complications occurred in five (35.7%) and three (21.4%) wounds in BTM and Integra, respectively ( p  = 0.031). Skin-graft failure rates were comparable ( p  = 0.121). Mean number of secondary procedures required after template placement was higher in the Integra group (BTM, 1.0; Integra, 1.9; p  = 0.090). Final healing was achieved in 17 (54.8%) BTM and 11 (64.7%) Integra wounds ( p  = 0.694). Median time to healing was 4.1 months after BTM and 2.6 months after Integra placement ( p  = 0.014). Conclusion  Compared with Integra, BTM achieved comparable wound healing and complication rates. Fewer secondary procedures and skin grafts were observed in BTM wounds, likely as a result of the coronavirus disease 2019 pandemic. At our institution, 100 cm 2 of product costs $850 for BTM and $3,150 for Integra, suggesting BTM as an economical alternative to fulfill the high functional and aesthetic requirements of upper-extremity wounds.

Clinical outcomes and resource utilisation in patients with major burns treated with NovoSorb® BTM

INTRODUCTION

Patients with major burns can undergo temporary coverage while skin graft donor sites heal, where dermal templates have an emerging role. The aim of this study was to evaluate the clinical outcomes and resource utilisation in patients with major burns treated with a bilayer biodegradable synthetic matrix (NovoSorb BTM).

METHOD

This retrospective cohort study included patients admitted to the Royal Brisbane and Women's Hospital Adult Burn Unit with burns to at least 40 % TBSA who survived their acute admission. Patients treated from July 2017 to June 2022 with BTM were compared with patients with similar injuries treated using cadaveric allograft as temporising full thickness wound coverage between January 2013 and June 2017. Outcomes measures included number of operations, total operative time, hospital and intensive care unit (ICU) length of stay (LOS), cadaveric allograft and BTM use, and blood product use. Unadjusted comparisons were made with Wilcoxon Rank-Sum tests and Fisher's exact tests. Multivariate linear regression was used to adjust for the effect of TBSA on each outcome.

RESULTS

Fifty-five patients were included (78 % male), 22 of whom were treated with BTM. We found no significant differences in age, sex, or TBSA between groups. One patient had half of the BTM removed due to infection and replaced with allograft. Patients treated with BTM had significantly less operative theatre time (median 1361.5 min [BTM] vs 1768 min [no BTM], P = 0.044). Number of operations, allograft use, hospital and ICU LOS, and blood product use were similar between groups. Adjusted models accounting for TBSA supported unadjusted models.

CONCLUSION

Resource utilisation and clinical outcomes were similar in patients with at least 40 % TBSA treated with BTM and those who were treated with allograft before the introduction of BTM. Patients treated with BTM had significantly less total operative time and no difference in number of operations, allograft use and ICU LOS.

Evaluation of Topical Off-The-Shelf Therapies to Improve Prolonged Field Care of Burn-Injured Service Members

INTRODUCTION

Burns are common injuries on the battlefield. Given austere environments, surgical debridement of injured service members is often not feasible in these settings. Delays in surgical debridement create a risk of infection and deranged healing for burn patients. As such, this study attempts to identify the best commercially available off-the-shelf (OTS) therapies with field-deployable potential to improve prolonged field care (PFC) of burn-injured soldiers.

METHODS

Deep partial-thickness (DPT) burns (25 cm2) were created on the dorsum of 5 anesthetized pigs utilizing a thermocouple burn device at 100°C for 15 seconds. Nonsurgical debridement was done 1-hour after burn creation using sterile saline water and gauze to remove excess eschar tissue. Animals were then randomized into 5 experimental groups, and OTS therapies were applied to 6 of the 12 created DPT burns. The remaining 6 burns were treated with 1% silver sulfadiazine cream (Ascend Laboratories, LLC, Parsippany, NJ) as the PFC standard of care (SOC) controls. The 5 randomized OTS therapies were: irradiated sterile human skin allograft (IHS), biodegradable temporizing matrix (BTM), polylactic acid skin substitute, hyaluronic acid ester matrix (HAM), and decellularized fish skin graft (FSG). Wounds were serially assessed on post-burn days 3, 7, 14, 21, and 28. Assessments were conducted using a combination of photographs, histology, and quantitative bacteriology. Endpoints included burn wound progression, re-epithelialization, wound contraction, scar elevation index, and colony-forming units (CFU).

RESULTS

The analysis demonstrated that by day 3, the FSG prevented burn wound progression the most efficiently. In terms of wound healing, the results showed re-epithelialization percentages close to 100% by day 28 for all treatment groups. No statically significant differences were observed. Quality of healing analyses demonstrated that the BTM-treated wounds had contracted less and the difference to the IHS-treated wounds was statistically significant (P < .05). As regards to antimicrobial properties, the CFU results showed no statistically significant differences between the OTS therapies and the SOC on days 3, 7, and 14.

CONCLUSIONS

The impact of Food and Drug Administration-approved OTS therapies was compared to the current PFC SOC for the treatment of DPT burns in a porcine model. Several topical options exist for the management of burns prior to definitive treatment in the operating room and warrant further evaluation. These therapies are actively used on civilian burn counterparts and have far-forward, field-deployable potential for use at the point of injury so that injured service members may not need evacuation to higher roles of care and combat power may be preserved. Our results demonstrated that all the studied OTS therapies performed well when compared to the SOC in terms of burn wound progression, wound healing, quality of healing, and quantitative bacteriology.

Design matters: A comparison of natural versus synthetic skin substitutes across benchtop and porcine wound healing metrics: An experimental study

Background and Aims

Skin substitutes, essential tools for helping close full thickness wounds with minimal scarring, are available in both collagen-based and synthetic polyurethane constructions. Here we explore fundamental differences between two frequently used skin substitutes and discuss how these differences may impact in vivo performance.

Methods

Polyurethane- and collagen-based matrices were characterized in vitro for pore size via scanning electron microscopy, hydrophobicity via liquid contact angle, conformability via bending angle, and biocompatibility via fibroblast and keratinocyte adhesion and proliferation. These matrices were then evaluated in a full-thickness excisional pig wound study followed by histological analysis. Statistical analysis was performed using t-tests or one-way analysis of variances with Tukey's multiple post hoc comparisons, where appropriate.

Results

Average pore diameter in the tested polyurethane matrix was over four times larger than that of the collagen matrix (589 ± 297 µm vs. 132 ± 91 µm). Through liquid contact angle measurement, the collagen matrix (not measurable) was found to be hydrophilic compared to the hydrophobic polyurethane matrix (>90°). The collagen matrix was significantly more conformable than the polyurethane matrix (9 ± 2° vs. 84 ± 5° bending angle, respectively). Fibroblast and keratinocyte adhesion and proliferation assays elucidated a significantly greater ability of both cell types to attach and proliferate on collagen versus polyurethane. While the porcine study showed minimal contraction of either matrix material, histological findings between the two treatments were markedly different. Collagen matrices were associated with early fibroblast infiltration and fibroplasia, whereas polyurethane matrices elicited a strong multinucleated giant cell response and produced a network of comparatively aligned collagen fibrils.

Conclusions

The more favorable in vitro properties of the collagen matrix led to less inflammation and better overall tissue response in vivo. Overall, our findings demonstrate how the choice of biomaterial and its design directly translate to differing in vivo mechanisms of action and overall tissue quality.

Treatment of Complex Wounds with NovoSorb® Biodegradable Temporising Matrix (BTM)-A Retrospective Analysis of Clinical Outcomes

Complex and chronic wounds represent a highly prevalent condition worldwide that requires a multimodal and interdisciplinary treatment approach to achieve good functional and aesthetic outcomes. Due to increasing costs of health care, an aging population and an increase in difficult-to-treat microbial colonization of wounds, complex wounds will become a substantial clinical, social and economic challenge in the upcoming years. In plastic reconstructive surgery, a variety of dermal skin substitutes have been established for clinical use. Since its approval as a dermal skin substitute in Germany, NovoSorb^® Biodegradable Temporising Matrix (BTM) has become a valuable therapeutic option for the treatment of full-thickness wound defects. The clinical data published to date are limited to case reports and small-scale case series with the main focus on single wounds. The aim of this single-center study was a retrospective analysis of our own patient collective that has received treatment with BTM for complex wounds. Overall, BTM showed to be a reliable and versatile reconstructive option, especially for patients with multiple co-morbidities and microbiologically colonized wounds. Although the preliminary findings have produced promising results, further investigation and research are warranted regarding long-term outcomes and additional clinical applications.

Thermoresponsive and Injectable Hydrogel for Tissue Agnostic Regeneration

Injectable hydrogels can support the body's innate healing capability by providing a temporary matrix for host cell ingrowth and neovascularization. The clinical adoption of current injectable systems remains low due to their cumbersome preparation requirements, device malfunction, product dislodgment during administration, and uncontrolled biological responses at the treatment site. To address these challenges, a fully synthetic and ready-to-use injectable biomaterial is engineered that forms an adhesive hydrogel that remains at the administration site regardless of defect anatomy. The product elicits a negligible local inflammatory response and fully resorbs into nontoxic components with minimal impact on internal organs. Preclinical animal studies confirm that the engineered hydrogel upregulates the regeneration of both soft and hard tissues by providing a temporary matrix to support host cell ingrowth and neovascularization. In a pilot clinical trial, the engineered hydrogel is successfully administered to a socket site post tooth extraction and forms adhesive hydrogel that stabilizes blood clot and supports soft and hard tissue regeneration. Accordingly, this injectable hydrogel exhibits high therapeutic potential and can be adopted to address multiple unmet needs in different clinical settings.

In Vivo Comparison of Synthetic Macroporous Filamentous and Sponge-like Skin Substitute Matrices Reveals Morphometric Features of the Foreign Body Reaction According to 3D Biomaterial Designs

Synthetic macroporous biomaterials are widely used in the field of skin tissue engineering to mimic membrane functions of the native dermis. Biomaterial designs can be subclassified with respect to their shape in fibrous designs, namely fibers, meshes or fleeces, respectively, and porous designs, such as sponges and foams. However, synthetic matrices often have limitations regarding unfavorable foreign body responses (FBRs). Severe FBRs can result in unfavorable disintegration and rejection of an implant, whereas mild FBRs can lead to an acceptable integration of a biomaterial. In this context, comparative in vivo studies of different three-dimensional (3D) matrix designs are rare. Especially, the differences regarding FBRs between synthetically derived filamentous fleeces and sponge-like constructs are unknown. In the present study, the FBRs on two 3D matrix designs were explored after 25 days of subcutaneous implantation in a porcine model. Cellular reactions were quantified histopathologically to investigate in which way the FBR is influenced by the biomaterial architecture. Our results show that FBR metrics (polymorph-nucleated cells and fibrotic reactions) were significantly affected according to the matrix designs. Our findings contribute to a better understanding of the 3D matrix tissue interactions and can be useful for future developments of synthetically derived skin substitute biomaterials.

Head and Neck Wound Reconstruction Using Biodegradable Temporizing Matrix Versus Collagen-Chondroitin Silicone Bilayer

BACKGROUND

Head and neck reconstruction is challenging because of the functional requirements of movement, sensation, and cosmesis of this highly visible region. This study is the first to compare Novosorb biodegradable temporizing matrix (BTM) and Integra collagen-chondroitin silicone (CCS) skin substitutes for reconstruction of soft tissue head and neck wounds.

METHODS

This retrospective review included adults who underwent wound reconstruction of the head/neck with either BTM or CCS between 2015 and 2020. Patient-level data, complications, and closure rates were compared.

RESULTS

The review identified 15 patients: 5 who received BTM and 10 who received CCS. Mean age at dermal template placement was 55 (range, 28-79) years. Race, sex, smoking status, medical comorbidities, defect size, radiation history, prior surgeries, and follow-up time were not significantly different between groups. Wound etiologies for BTM and CCS included burn (40% vs 60%), trauma (20% vs 20%), surgical wounds (20% vs 20%), and skin cancer (20% vs 0%), respectively (P = .026). Skin grafts were placed in 8 (80%) wounds after CCS placement, compared with 3 (60%) after BTM (P = .670). Template reapplication was required in 2 (40%) BTM wounds and 3 (30%) CCS wounds (P = 1.0). Infection, hematoma, and seroma were comparable between groups, although skin graft failure was higher in the CCS group at 3 (37.5%) compared with 0 for BTM (P = .506). More secondary procedures were required after CCS placement (CCS, 1.9 ± 2.2; BTM, 0.9 ± 0.8; P = .090). Definitive closure in patients not lost to follow-up occurred in 4 (100%) BTM and 6 (75%) CCS cases (P = 1.0).

CONCLUSIONS

Head and neck wounds treated with BTM had comparable closure and complication rates as CCS bilayer and required fewer secondary procedures and skin grafts. These findings suggest that BTM is safe and efficacious for application in head and neck wounds and may be considered as an economical alternative.

Wound healing and dermal regeneration in severe burn patients treated with NovoSorb® Biodegradable Temporising Matrix: A prospective clinical study

INTRODUCTION

For extensive burns, autologous donor skin may be insufficient for early debridement and grafting in a single stage. A novel, synthetic polyurethane dermal template (NovoSorb® Biodegradable Temporising Matrix, BTM) was developed to address this need. The aim of this study was to evaluate use of BTM for primary dermal repair after deep burn injury.

METHODS

A multicentre, prospective, clinical study was conducted from September 2015 to May 2018. The primary endpoint was % split skin graft take over applied BTM at 7-10 days after grafting. Secondary endpoints included % BTM take, incidence of infection and adverse events, and scar quality to 12 months after BTM application.

RESULTS

Thirty patients were treated with BTM and delayed split skin grafting. The % graft take had a mean of 81.9% and % BTM take had a mean of 88.6%, demonstrating effective integration of BTM. When managed appropriately, it was possible for BTM to integrate successfully despite findings suggestive of infection. Scar quality improved over time.

DISCUSSION

These results provide additional clinical evidence on the safety and performance of BTM as an effective dermal substitute in the treatment of patients with deep burn injuries.

Reactive oxygen species-degradable polythioketal urethane foam dressings to promote porcine skin wound repair

Porous, resorbable biomaterials can serve as temporary scaffolds that support cell infiltration, tissue formation, and remodeling of nonhealing skin wounds. Synthetic biomaterials are less expensive to manufacture than biologic dressings and can achieve a broader range of physiochemical properties, but opportunities remain to tailor these materials for ideal host immune and regenerative responses. Polyesters are a well-established class of synthetic biomaterials; however, acidic degradation products released by their hydrolysis can cause poorly controlled autocatalytic degradation. Here, we systemically explored reactive oxygen species (ROS)-degradable polythioketal (PTK) urethane (UR) foams with varied hydrophilicity for skin wound healing. The most hydrophilic PTK-UR variant, with seven ethylene glycol (EG7) repeats flanking each side of a thioketal bond, exhibited the highest ROS reactivity and promoted optimal tissue infiltration, extracellular matrix (ECM) deposition, and reepithelialization in porcine skin wounds. EG7 induced lower foreign body response, greater recruitment of regenerative immune cell populations, and resolution of type 1 inflammation compared to more hydrophobic PTK-UR scaffolds. Porcine wounds treated with EG7 PTK-UR foams had greater ECM production, vascularization, and resolution of proinflammatory immune cells compared to polyester UR foam-based NovoSorb Biodegradable Temporizing Matrix (BTM)-treated wounds and greater early vascular perfusion and similar wound resurfacing relative to clinical gold standard Integra Bilayer Wound Matrix (BWM). In a porcine ischemic flap excisional wound model, EG7 PTK-UR treatment led to higher wound healing scores driven by lower inflammation and higher reepithelialization compared to NovoSorb BTM. PTK-UR foams warrant further investigation as synthetic biomaterials for wound healing applications.

Non-Invasive and Surgical Modalities for Scar Management: A Clinical Algorithm

Scars can lead to aesthetic and functional impairments. The treatment of scars requires meticulous planning and an individually adapted therapeutic strategy. A conceptual algorithm for scar treatment makes everyday clinical work easier for the practitioner and offers more safety for the patient. Based on a retrospective analysis of 1427 patients who presented for treatment of a variety of scars, we developed an algorithm for scar management and treatment. The treatments are presented using case descriptions. Additionally, an electronic search of MEDLINE, EMBASE, and ClinicalTrials.gov databases was performed utilizing combinations of relevant medical subject headings for "scar treatment", "hypertrophic scar treatment" and "keloid treatment". Reference lists of relevant articles and reviews were hand-searched for additional reports. Observed outcomes included: conservative scar therapy, minimally invasive scar therapy, and surgical scar therapy using local, regional and free flaps. With this work, we provide an algorithm for safe scar treatment. For better understanding, we have described a clinical case for each algorithm modality.

Scale-up of a Composite Cultured Skin Using a Novel Bioreactor Device in a Porcine Wound Model

Extensive deep-burn management with a two-stage strategy can reduce reliance on skin autografts; a biodegradable polyurethane scaffold to actively temporize the wound and later an autologous composite cultured skin (CCS) for definitive closure. The materials fulfilling each stage have undergone in vitro and in vivo pretesting in "small" large animal wounds. For humans, producing multiple, large CCSs requires a specialized bioreactor. This article reports a system used to close large porcine wounds. Three Large White pigs were used, each with two wounds (24.5 cm × 12 cm) into which biodegradable dermal scaffolds were implanted. A sample from discarded tissue allowed isolation/culture of autologous fibroblasts and keratinocytes. CCS production began by presoaking a 1-mm-thick biodegradable polyurethane foam in autologous plasma. In the bioreactor cassette, fibroblasts were seeded into the matrix with thrombin until established, followed by keratinocytes. The CCSs were applied onto integrated dermal scaffolds on day 35, alongside a sheet skin graft (30% of one wound). Serial punch biopsies, trans-epidermal water loss readings (TEWL), and wound measurements indicated epithelialization. During dermal scaffold integration, negligible wound contraction was observed (average 4.5%). After CCS transplantation, the control skin grafts were "taken" by day 11 when visible islands of epithelium were clinically observed on 2/3 CCSs. Closure was confirmed histologically, with complete epithelialization by day 63 post-CCS transplantation (CCS TEWL ~ normal skin average 11.9 g/m2h). Four of six wounds demonstrated closure with robust, stratified epithelium. Generating large pieces of CCS capable of healing large wounds is thus possible using a specialized designed bioreactor.

Advances in Skin Tissue Bioengineering and the Challenges of Clinical Translation

Skin tissue bioengineering is an emerging field that brings together interdisciplinary teams to promote successful translation to clinical care. Extensive deep tissue injuries, such as large burns and other major skin loss conditions, are medical indications where bioengineered skin substitutes (that restore both dermal and epidermal tissues) are being studied as alternatives. These may not only reduce mortality but also lessen morbidity to improve quality of life and functional outcome compared with the current standards of care. A common objective of dermal-epidermal therapies is to reduce the time required to accomplish stable closure of wounds with minimal scar in patients with insufficient donor sites for autologous split-thickness skin grafts. However, no commercially-available product has yet fully satisfied this objective. Tissue engineered skin may include cells, biopolymer scaffolds and drugs, and requires regulatory review to demonstrate safety and efficacy. They must be scalable for manufacturing and distribution. The advancement of technology and the introduction of bioreactors and bio-printing for skin tissue engineering may facilitate clinical products' availability. This mini-review elucidates the reasons for the few available commercial skin substitutes. In addition, it provides insights into the challenges faced by surgeons and scientists to develop new therapies and deliver the results of translational research to improve patient care.

Surviving an Extensive Burn Injury Using Advanced Skin Replacement Technologies

There have been significant improvements in the technology available for treating extensive burns in the past decade. This case presents two unique, skin replacement technologies that were used to treat an 86% surface area flame burn in a pediatric patient. A temporary dermal replacement, known as "Novosorb™ Biodegradable Temporizing Matrix" was first used to stabilize the burn injury and remained in place for approximately three months. Given the large burn size and lack of available donor skin for grafting, a permanent skin replacement product known as "Self-Assembled Skin Substitute (SASS)" was then utilized to cover the burns. SASS is a novel technology that was developed to replace skin as an autologous skin graft and is currently available in Canada through a clinical trial for major burns. Ultimately, the concurrent use of these two technologies allowed for the unprecedented survival of a child following an extensive and life-threatening burn injury.

Experience with NovoSorb® Biodegradable Temporising Matrix in reconstruction of complex wounds

BACKGROUND

The NovoSorb® Biodegradable Temporising Matrix (BTM) is a synthetic polyurethane dermal matrix used to reconstruct complex wounds including deep dermal and full-thickness burns, necrotising fasciitis and free flap donor site. We hope to further explore its potential applications in this series.

METHODS

Patients who received BTM application across four centres over an 18-month period were included. Patients were followed up to assess BTM and graft take, the aesthetic, the return of sensation and complications.

RESULTS

A total of 27 patients with 35 wounds were identified with a range of aetiologies. Thirty-three wounds had 100% integration of BTM at the time of sealing membrane removal. Seven wounds had partial graft loss that later healed by secondary intention. In two cases, re-epithelialisation occurred with BTM alone without split-skin graft.

CONCLUSION

BTM offers a safe and reliable reconstructive option in challenging wounds that would otherwise require more complex operations.

Contemporary Aspects of Burn Care

The past one hundred years have seen tremendous improvements in burn care, allowing for decreased morbidity and mortality of this pathology. The more prominent advancements occurred in the period spanning 1930-1980; notably burn resuscitation, early tangential excision, and use of topical antibiotic dressings; and are well documented in burn literature. This article explores the advancements of the past 40 years and the areas of burn management that are presently topics of active discussion and research.

A Short History of Skin Grafting in Burns: From the Gold Standard of Autologous Skin Grafting to the Possibilities of Allogeneic Skin Grafting with Immunomodulatory Approaches

Due to groundbreaking and pioneering developments in the last century, significant improvements in the care of burn patients have been achieved. In addition to the still valid therapeutic standard of autologous split-thickness skin grafting, various commercially available skin substitutes are currently available. Significant progress in the field of tissue engineering has led to the development of promising therapeutic approaches. However, scientific advances in the field of allografting and transplant immunology are of great importance. The achievement of various milestones over the past decades has provided thought-provoking impulses in the field of skin allotransplantation. Thus, biologically viable skin allotransplantation is still not a part of the clinical routine. The purpose of this article is to review the achievements in burn surgery with regards to skin allotransplantation in recent years.

A consecutive case series of defects reconstructed using NovoSorbⓇ Biodegradable Temporising Matrix: Initial experience and early results

BACKGROUND

NovoSorb^Ⓡ Biodegradable Temporising Matrix (BTM) is a synthetic dermal template recently approved for treatment of full thickness defects of the skin. It requires a two-stage reconstruction where it is initially placed into a defect to generate a neodermis, which is later covered by a split skin graft. It has previously been described for the treatment of acute full thickness burn injury, necrotising fasciitis and free flap donor site reconstruction.

METHODS

A consecutive case series review of patients treated with BTM at Middlemore Hospital was performed. Patient demographics, defect aetiology, indications for dermal matrix use, surgical details, and complications were recorded using information gathered from the medical records.

RESULTS

This case series included 25 patients with a range of defects resulting from acute full thickness burn injury, burn scar revision, necrotising soft-tissue infection, tumour excision and traumatic loss. In these patients, 72% of wounds were identified as complex defects with exposed bone or tendon. Complications encountered included infection, non-adherence and incomplete vascularisation.

CONCLUSION

BTM provided a good reconstructive option for a wide range of defects, many of which were not amenable to immediate skin grafting. Once vascularised and ready for the second stage, it developed a red-pink colour and demonstrated capillary refill. Similar to other dermal matrices, infection was a commonly encountered problem. However, BTM proved more tolerant to this and was able to be salvaged in most cases, allowing the second stage to proceed as normal.

A paradigm shift in practice-the benefits of early active wound temporisation rather than early skin grafting after burn eschar excision

After major burn injury, once survival is achieved by the immediate excision of all deep burn eschar, we are faced with a patient who is often physiologically well but with very extensive wounds. While very early grafting yields excellent results after the excision of small burns, it is not possible to achieve the same results once the wound size exceeds the available donor site. In patients where 50%-100% of the total body surface area is wound, we rely on serial skin graft harvest, from finite donor site resources, and the massive expansion of those harvested grafts to effect healing. The result is frequently disabling and dysaesthetic. Temporisation of the wounds both passively, with cadaver allograft, and actively, with dermal scaffolds, has been successfully employed to ameliorate some of the problems caused by our inability to definitively close wounds early. Recent advances in technology have demonstrated that superior functional and cosmetic outcomes can be achieved in actively temporised areas even when compared with definitive early closure with skin graft. This has several beneficial implications for both patient and surgeon, affecting the timing of definitive wound closure and creating a paradigm shift in the care of the burned patient.

Treatment of a Full-Thickness Burn Injury With NovoSorb Biodegradable Temporizing Matrix and RECELL Autologous Skin Cell Suspension: A Case Series

Dermal substitutes coupled with split thickness skin graft are the primary method of treating most severe full-thickness burns particularly when there is a lack of healthy donor skin. Although dermal replacements optimize functional and aesthetic outcomes in patients, the risk of infection and the amount of time required to process most dermal substitutes delay treatment potentially compromising graft take and the overall healing process. The purpose of this case series is to describe the treatment course of patients with severe burn injuries using a novel synthetic Biodegradable Temporizing Matrix (NovoSorb BTM) in conjunction with RECELL Autologous Cell Harvesting Device, a new methodology allowing for a timely point-of-care preparation of an autologous skin cell suspension in combination with a 3:1 split-thickness skin graft. To the best of our knowledge, this is the first reported case series to describe the treatment algorithm and clinical outcomes of deep full-thickness burns utilizing BTM in conjunction with RECELL ASCS.

Bio-engineering a tissue flap utilizing a porous scaffold incorporating a human induced pluripotent stem cell-derived endothelial cell capillary network connected to a vascular pedicle

Tissue flaps are used to cover large/poorly healing wounds, but involve complex surgery and donor site morbidity. In this study a tissue flap is assembled using the mammalian body as a bioreactor to functionally connect an artery and vein to a human capillary network assembled from induced pluripotent stem cell-derived endothelial cells (hiPSC ECs). In vitro: Porous NovoSorb™ scaffolds (3 mm × 1.35 mm) were seeded with 200,000 hiPSC ECs ± 100,000 human vascular smooth muscle cells (hvSMC), and cultured for 1-3 days, with capillaries formed by 24 h which were CD31⁺, VE-Cadherin⁺, EphB4⁺, VEGFR2⁺ and Ki67⁺, whilst hvSMCs (calponin⁺) attached abluminally. In vivo: In SCID mice, bi-lateral epigastric vascular pedicles were isolated in a silicone chamber for a 3 week 'delay period' for pedicle capillary sprouting, then reopened, and two hiPSC EC ± hvSMCs seeded scaffolds transplanted over the pedicle. The chamber was either resealed (Group 1), or removed and surrounding tissue secured around the pedicle + scaffolds (Group 2), for 1 or 2 weeks. Human capillaries survived in vivo and were CD31⁺, VE-Cadherin⁺ and VEGFR2⁺. Human vSMCs remained attached, and host mesenchymal cells also attached abluminally. Systemically injected FITC-dextran present in human capillary lumens indicated inosculation to host capillaries. Human iPSC EC capillary morphometric parameters at one week in vivo were equal to or higher than the same parameters measured in human abdominal skin. This 'proof of concept' study has demonstrated that bio-engineering an autologous human tissue flap based on hiPSC EC could minimize the use of donor flaps and has potential applications for complex wound coverage. STATEMENT OF SIGNIFICANCE: Tissue flaps, used for surgical reconstruction of wounds, require complex surgery, often associated with morbidity. Bio-engineering a simpler alternative, we assembled a human induced pluripotent stem cell derived endothelial cell (hiPSC ECs) capillary network in a porous scaffold in vitro, which when transplanted over a mouse vascular pedicle in vivo formed a functional tissue flap with mouse blood flow in the human capillaries. Therefore it is feasible to form an autologous tissue flap derived from a hiPSC EC capillary network assembled in vitro, and functionally connect to a vascular pedicle in vivo that could be utilized in complex wound repair for chronic or acute wounds.

Xeno-free expansion of adult keratinocytes for clinical application: the use of human-derived feeder cells and serum

Cultured epithelial autograft (CEA) was the birth of skin tissue engineering and encompassed methodologies for the isolation and expansion of autologous basal keratinocytes for burn treatment that are still practiced at some specialised units around the world. One of the limitations of CEA, however, is the reliance on animal-derived material during the manufacturing process and despite all efforts to date, no xeno-free alternative with proven efficacy has been reported. Here, we investigate whether human-derived fibroblast feeder cells and human serum can sufficiently and effectively provide a suitable microenvironment for adult keratinocyte isolation and expansion. Human dermal fibroblasts and epidermal keratinocytes were isolated from discarded skin during abdominoplasty and breast reduction procedures and cultured in xeno-free conditions. We report that these xeno-free adult keratinocytes form similar numbers of colony-forming units as those cultured using the Green's methods; however, xeno-free keratinocytes express lower levels of α6 integrin (CD49f; a progenitor and stem cell marker). We identified IL-8 as a potential growth factor secreted by adult human fibroblasts that may enhance keratinocyte colony formation in human serum. Finally, we propose a step-by-step xeno-free isolation and cultivation methodology for adult keratinocytes that can be tested further in serial cultivation for clinical application.

Osteoclastic Bioresorption of Biomaterials: Two- and Three-Dimensional Imaging and Quantification

Purpose

Bioresorbable materials have been developed in the hope that the body will replace them with newly formed tissue. The first step of this remodeling process in bone is the bioresorption of the material by osteoclasts. The aim of this study was to analyze osteoclastic resorption of biomaterials in vitro using the commonly used two-dimensional methods of light-microscopy (LM) and scanning electron microscopy (SEM) in comparison with infinite focus microscopy (IFM), a recently developed imaging method allowing for three-dimensional surface analysis.

Methods

Human hematopoietic stem cells were cultivated in the presence of the cytokines M-CSF and RANK-L for 4 weeks directly on dentin and a calcium phosphate cement. Osteoclast development was surveyed with standard techniques. After removal of the cells, resorption was characterized and quantified by LM, SEM and IFM.

Results

Osteoclast cultures on the biomaterials presented the typical osteoclast-specific markers. On dentin samples LM, SEM as well as IFM allowed for discrimination of resorption. Quantification of the resorbed area showed a linear correlation between the results (LM vs. SEM: r=0.996, p=0.004; SEM vs. IFM: r=0.989, p=0.011; IFM vs. LM: r=0.995). It was not possible to demarcate resorption pits on GB14 using LM or SEM. With IFM, resorption on GB14 could be visualized and quantified two- and three-dimensionally.

Conclusions

In this paper we introduce IFM as a technology for three-dimensional visualization and quantification of resorption of biomaterials. Better understanding of the bioresorption of biomaterials may help in the design of better materials and might therefore constitute an important step on the avenue to the development of artificial bone.

A Novel Biodegradable Polyurethane Matrix for Auricular Cartilage Repair: An In Vitro and In Vivo Study

Auricular reconstruction poses a challenge for reconstructive and burns surgeons. Techniques involving cartilage tissue engineering have shown potential in recent years. A biodegradable polyurethane matrix developed for dermal reconstruction offers an alternative to autologous, allogeneic, or xenogeneic biologicals for cartilage reconstruction. This study assesses such a polyurethane matrix for this indication in vivo and in vitro. To evaluate intrinsic cartilage repair, three pigs underwent auricular surgery to create excisional cartilage ± perichondrial defects, measuring 2 × 3 cm in each ear, into which acellular polyurethane matrices were implanted. Biopsies were taken at day 28 for histological assessment. Porcine chondrocytes ± perichondrocytes were cultured and seeded in vitro onto 1 × 1 cm polyurethane scaffolds. The total culture period was 42 days; confocal, histological, and immunohistochemical analyses of scaffold cultures were performed on days 14, 28, and 42. In vivo, the polyurethane matrices integrated with granulation tissue filling all biopsy samples. Minimal neocartilage invasion was observed marginally on some samples. Tissue composition was identical between ears whether perichondrium was left intact, or not. In vitro, the polyurethane matrix was biocompatible with chondrocytes ± perichondrocytes and supported production of extracellular matrix and Type II collagen. No difference was observed between chondrocyte culture alone and chondrocyte/perichondrocyte scaffold coculture. The polyurethane matrix successfully integrated into the auricular defect and was a suitable scaffold in vitro for cartilage tissue engineering, demonstrating its potential application in auricular reconstruction.

Stem cells, niches and scaffolds: Applications to burns and wound care

The importance of skin to survival, and the devastating physical and psychological consequences of scarring following reparative healing of extensive or difficult to heal human wounds, cannot be disputed. We discuss the significant challenges faced by patients and healthcare providers alike in treating these wounds. New state of the art technologies have provided remarkable insights into the role of skin stem and progenitor cells and their niches in maintaining skin homeostasis and in reparative wound healing. Based on this knowledge, we examine different approaches to repair extensive burn injury and chronic wounds, including full and split thickness skin grafts, temporising matrices and scaffolds, and composite cultured skin products. Notable developments include next generation skin substitutes to replace split thickness skin autografts and next generation gene editing coupled with cell therapies to treat genodermatoses. Further refinements are predicted with the advent of bioprinting technologies, and newly defined biomaterials and autologous cell sources that can be engineered to more accurately replicate human skin architecture, function and cosmesis. These advances will undoubtedly improve quality of life for patients with extensive burns and difficult to heal wounds.

The evolution of acute burn care - retiring the split skin graft

The skin graft was born in 1869 and since then, surgeons have been using split skin grafts for wound repair. Nevertheless, this asset fails the big burn patient, who deserves an elastic, mobile and robust outcome but who receives the poorest possible outcome based on donor site paucity. Negating the need for the skin graft requires an autologous composite cultured skin and a material capable of temporising the burn wound for four weeks until the composite is produced. A novel, biodegradable polyurethane chemistry has been used to create two such products. This paper describes the design, production, optimisation and evaluation of several iterations of these products. The evaluation has occurred in a variety of models, both in vitro and in vivo, employing Hunterian scientific principles, and embracing Hunter's love and appreciation of comparative anatomy. The process has culminated in significant human experience in complex wounds and extensive burn injury. Used serially, the products offer robust and elastic healing in deep burns of any size within 6 weeks of injury.

Artificial dermal templates: A comparative study of NovoSorb™ Biodegradable Temporising Matrix (BTM) and Integra(®) Dermal Regeneration Template (DRT)

BACKGROUND

Artificial dermal templates play an important role in physiologic wound closure after injury. In addition to contributing to stable, durable and flexible wound closure, they provide a scaffold for tissue repair. Several dermal templates are commercially available, with animal-derived Integra(®) dermal regeneration template perhaps the most widely used. NovoSorb™ Biodegradable Temporising Matrix (BTM) is a fully synthetic alternative that eliminates any risk of cross-species residual antigenicity. In this study, we aimed to compare early response after application of NovoSorb™ BTM with Integra(®) in terms of temporary wound closure, host cell infiltration, neovascularisation and collagen deposition in a mouse model.

METHODS

Twenty athymic nude mice received full-thickness skin excision followed by grafting of the dermal template (n=10 NovoSorb™ BTM, n=10 Integra(®)), with the grafts excised and assessed after two weeks.

RESULTS

All twenty mice achieved temporary wound closure with no evidence of wound contracture. Microscopically, all twenty grafts became infiltrated with host cells along the entire length of the template, with NovoSorb™ BTM demonstrating a particular abundance of host inflammatory cells. Evidence of new collagen deposition and neovascularisation was observed in both templates, with NovoSorb™ BTM demonstrating a more extensive vascular network at this time point. However, a greater inflammatory response was also observed in the NovoSorb™ BTM grafts at this time point.

CONCLUSIONS

In this study, NovoSorb™ BTM demonstrates favourable properties as a dermal template, but further investigation is required to assess the significance of the differing inflammatory and vascular response to its implantation compared with Integra(®).

Toward a skin-material interface with vacuum-integrated capped macroporous scaffolds

Avulsion, epidermal marsupialization, and infection cause failure at the skin-material interface. A robust interface would permit implantable robotics, prosthetics, and other medical devices; reconstruction of surgical defects, and long-term access to blood vessels and body cavities. Torus-shaped cap-scaffold structures were designed to work in conjunction with negative pressure to address the three causes of failure. Six wounds were made on the backs of each of four 3-month old pigs. Four unmodified (no caps) scaffolds were implanted along with 20 cap-scaffolds. Collagen type 4 was attached to 21 implants. Negative pressure then was applied. Structures were explanted and assessed histologically at day 7 and day 28. At day 28, there was close tissue apposition to scaffolds, without detectable reactions from defensive or interfering cells. Three cap-scaffolds explanted at day 28 showed likely attachment of epidermis to the cap or cap-scaffold junction, without deeper marsupialization. The combination of toric-shaped cap-scaffolds with negative pressure appears to be an intrinsically biocompatible system, enabling a robust skin-material interface. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1307-1318, 2017.

In vitro investigations of a novel wound dressing concept based on biodegradable polyurethane

Non-healing and partially healing wounds are an important problem not only for the patient but also for the public health care system. Current treatment solutions are far from optimal regarding the chosen material properties as well as price and source. Biodegradable polyurethane (PUR) scaffolds have shown great promise for in vivo tissue engineering approaches, but accomplishment of the goal of scaffold degradation and new tissue formation developing in parallel has not been observed so far in skin wound repair. In this study, the mechanical properties and degradation behavior as well as the biocompatibility of a low-cost synthetic, pathogen-free, biocompatible and biodegradable extracellular matrix mimicking a PUR scaffold was evaluated in vitro. The novel PUR scaffolds were found to meet all the requirements for optimal scaffolds and wound dressings. These three-dimensional scaffolds are soft, highly porous, and form-stable and can be easily cut into any shape desired. All the material formulations investigated were found to be nontoxic. One formulation was able to be defined that supported both good fibroblast cell attachment and cell proliferation to colonize the scaffold. Tunable biodegradation velocity of the materials could be observed, and the results additionally indicated that calcium plays a crucial role in PUR degradation. Our results suggest that the PUR materials evaluated in this study are promising candidates for next-generation wound treatment systems and support the concept of using foam scaffolds for improved in vivo tissue engineering and regeneration.

High Modulus Biodegradable Polyurethanes for Vascular Stents: Evaluation of Accelerated in vitro Degradation and Cell Viability of Degradation Products

We have recently reported the mechanical properties and hydrolytic degradation behavior of a series of NovoSorb™ biodegradable polyurethanes (PUs) prepared by varying the hard segment (HS) weight percentage from 60 to 100. In this study, the in vitro degradation behavior of these PUs with and without extracellular matrix (ECM) coating was investigated under accelerated hydrolytic degradation (phosphate buffer saline; PBS/70°C) conditions. The mass loss at different time intervals and the effect of aqueous degradation products on the viability and growth of human umbilical vein endothelial cells (HUVEC) were examined. The results showed that PUs with HS 80% and below completely disintegrated leaving no visual polymer residue at 18 weeks and the degradation medium turned acidic due to the accumulation of products from the soft segment (SS) degradation. As expected the PU with the lowest HS was the fastest to degrade. The accumulated degradation products, when tested undiluted, showed viability of about 40% for HUVEC cells. However, the viability was over 80% when the solution was diluted to 50% and below. The growth of HUVEC cells is similar to but not identical to that observed with tissue culture polystyrene standard (TCPS). The results from this in vitro study suggested that the PUs in the series degraded primarily due to the SS degradation and the cell viability of the accumulated acidic degradation products showed poor viability to HUVEC cells when tested undiluted, however particles released to the degradation medium showed cell viability over 80%.

"Take" of a polymer-based autologous cultured composite "skin" on an integrated temporizing dermal matrix: proof of concept

This study aimed to investigate the ability of an autologous cultured composite skin (CCS) to close similar biodegradable temporizing matrix (BTM)-integrated wounds, and its effectiveness in healing fresh full-thickness wounds after the failure of cultured epithelial autograft in its two forms (sheets and suspensions) to epithelialize over an integrated polymer BTM. Using a porcine model, autologous split-skin grafts were harvested three of four dorsal 8 × 8 cm treatment sites. These three sites were subsequently converted to full-thickness wounds and BTMs were implanted. The grafts were used to produce autologous CCSs for each pig. These consisted of a 1 mm thick biodegradable polymer foam scaffold into which fibroblasts and keratinocytes harvested from the grafts were cocultured. At Day 28, on each animal, the autologous CCSs were applied to two of the integrated BTMs, an autologous split-skin graft was applied to the third integrated BTM, and one CCS was applied immediately into a fresh, "naked" (no BTM applied) wound. The CCSs were capable of generating a bilayer repair over the naked wound's fat base and BTM-integrated wounds, which consisted of dermal elements and a keratinized stratified squamous epidermis anchored with a basement membrane by day 7. The CCSs behaved in different ways: either as a delivery vehicle allowing similar development of a bilayer repair while the polymer foam was shed from the wound, or generating a bilayer repair with the foam scaffold being retained (composite "take"). These results conclude our porcine program and provide proof of concept that the integrated BTM can be closed with an autologous CCS. Once fully optimized, this may provide robust repair without resorting to the split-skin graft, important in those cases where unburned donor site is unavailable.