Wound Milieu Research Articles

Chemokine-Capturing Wound Contact Layer Rescues Dermal Healing.

Excessive inflammation often impedes the healing of chronic wounds. Scavenging of chemokines by multiarmed poly(ethylene glycol)‐glycosaminoglycan (starPEG‐GAG) hydrogels has recently been shown to support regeneration in a diabetic mouse chronic skin wound model. Herein, a textile‐starPEG‐GAG composite wound contact layer (WCL) capable of selectively sequestering pro‐inflammatory chemokines is reported. Systematic variation of the local and integral charge densities of the starPEG‐GAG hydrogel component allows for tailoring its affinity profile for biomolecular signals of the wound milieu. The composite WCL is subsequently tested in a large animal (porcine) model of human wound healing disorders. Dampening excessive inflammatory signals without affecting the levels of pro‐regenerative growth factors, the starPEG‐GAG hydrogel‐based WCL treatment induced healing with increased granulation tissue formation, angiogenesis, and deposition of connective tissue (collagen fibers). Thus, this biomaterials technology expands the scope of a new anti‐inflammatory therapy toward clinical use.

Collagen in Wound Healing.

Normal wound healing progresses through inflammatory, proliferative and remodeling phases in response to tissue injury. Collagen, a key component of the extracellular matrix, plays critical roles in the regulation of the phases of wound healing either in its native, fibrillar conformation or as soluble components in the wound milieu. Impairments in any of these phases stall the wound in a chronic, non-healing state that typically requires some form of intervention to guide the process back to completion. Key factors in the hostile environment of a chronic wound are persistent inflammation, increased destruction of ECM components caused by elevated metalloproteinases and other enzymes and improper activation of soluble mediators of the wound healing process. Collagen, being central in the regulation of several of these processes, has been utilized as an adjunct wound therapy to promote healing. In this work the significance of collagen in different biological processes relevant to wound healing are reviewed and a summary of the current literature on the use of collagen-based products in wound care is provided.

Photobiomodulation as an Adjunct Therapy in Wound Healing.

"Light amplification by stimulated emission of radiation" or more commonly known as Laser has become very popular in the field of dermatology and aesthetic medicine over the past decades. For the treatment of wound healing, a combination of different wavelengths for laser therapy has been introduced which includes 660, 800, and 970 nm. The aim of this study was to note wound healing utilizing photobiomodulation as an adjunct therapy by measuring the wound size in terms of length and width (area measurement). Study participants were selected randomly from a pool of patients who were attending for their routine follow-up visits in the Wound Care Unit in Hospital Kuala Lumpur. Eleven patients with chronic wounds of different etiologies, ie, diabetic foot ulcer and nonhealing ulcer, were recruited for this study . Wound assessment was done prior to cleansing using distilled water and followed by debridement if necessary. Subsequently, the laser technician and patients used protective goggles before applying a super intense continuous flow of laser with 3 wavelengths, ie, 660, 800, and 970 nm with 30 kJ of energy with the handpiece over a 3 min period whereby it is focused on the wound milieu and then rotated around the periwound area. There were 9 diabetic foot ulcers and 2 nonhealing ulcers treated with photobiomodulation as an adjunct therapy. All wounds were managed with the standard of care. Three wounds ie, 3 diabetic foot ulcers and 1 nonhealing ulcer were closed completely. Meanwhile, the other 7 ulcers are at 68.2% to 99% in terms of wound area reduction and new granulomatous tissue was present indicating high healing potential. Therefore, the photobiomodulation was effective as an adjunct in the management of diabetic foot and nonhealing ulcers in this case series. A larger sample size would be able to show the significance of this finding.

Milieu matters: An in vitro wound milieu to recapitulate key features of, and probe new insights into, mixed-species bacterial biofilms

Bacterial biofilms are a major cause of delayed wound healing. Consequently, the study of wound biofilms, particularly in host-relevant conditions, has gained importance. Most in vitro studies employ refined laboratory media to study biofilms, representing conditions that are not relevant to the infection state. To mimic the wound milieu, in vitro biofilm studies often incorporate serum or plasma in growth conditions, or employ clot or matrix-based biofilm models. While incorporating serum or plasma alone is a minimalistic approach, the more complex in vitro wound models are technically demanding, and poorly compatible with standard biofilm assays. Based on previous reports of clinical wound fluid composition, we have developed an in vitro wound milieu (IVWM) that includes, in addition to serum (to recapitulate wound fluid), matrix elements and biochemical factors. With Luria-Bertani broth and Fetal Bovine Serum (FBS) for comparison, the IVWM was used to study planktonic growth, biofilm features, and interspecies interactions, of common wound pathogens, Staphylococcus aureus and Pseudomonas aeruginosa. We demonstrate that the IVWM recapitulates widely reported in vivo biofilm features such as biomass formation, metabolic activity, increased antibiotic tolerance, 3D structure, and interspecies interactions for monospecies and mixed-species biofilms. Further, the IVWM is simple to formulate, uses laboratory-grade components, and is compatible with standard biofilm assays. Given this, it holds potential as a tractable approach to study wound biofilms under host-relevant conditions.

Nanoparticle-Based Rifampicin Delivery System Development

The alkaline milieu of chronic wounds severely impairs the therapeutic effect of antibiotics, such as rifampicin; as such, the development of new drugs, or the smart delivery of existing drugs, is required. Herein, two innovative polyelectrolyte nanoparticles (PENs), composed of an amphiphilic chitosan core and a polycationic shell, were synthesized at alkaline pH, and in vitro performances were assessed by 1H NMR, elemental analysis, FT-IR, XRD, DSC, DLS, SEM, TEM, UV/Vis spectrophotometry, and HPLC. According to the results, the nanostructures exhibited different morphologies but similar physicochemical properties and release profiles. It was also hypothesized that the simultaneous use of the nanosystem and an antioxidant could be therapeutically beneficial. Therefore, the simultaneous effects of ascorbic acid and PENs were evaluated on the release profile and degradation of rifampicin, in which the results confirmed their synergistic protective effect at pH 8.5, as opposed to pH 7.4. Overall, this study highlighted the benefits of nanoparticulate development in the presence of antioxidants, at alkaline pH, as an efficient approach for decreasing rifampicin degradation.

Epigenetic regulation of cellular functions in wound healing.

Stringent spatiotemporal regulation of the wound healing process involving multiple cell types is associated with epigenetic mechanisms of gene regulation, such as DNA methylation, histone modification and chromatin remodelling, as well as non-coding RNAs. Here, we discuss the epigenetic changes that occur during wound healing and the rapidly expanding understanding of how these mechanisms affect healing resolution in both acute and chronic wound milieu. We provide a focussed overview of current research into epigenetic regulators that contribute to wound healing by specific cell type. We highlight the role of epigenetic regulators in the molecular pathophysiology of chronic wound conditions. The understanding of how epigenetic regulators can affect cellular functions during normal and impaired wound healing could lead to novel therapeutic approaches, and we outline questions that can provide guidance for future research on epigenetic-based interventions to promote healing. Dissecting the dynamic interplay between cellular subtypes involved in wound healing and epigenetic parameters during barrier repair will deepen our understanding of how to improve healing outcomes in patients affected by chronic non-healing wounds.

Proximal digit tip amputation initiates simultaneous blastema and transient fibrosis formation and results in partial regeneration

Complete extremity regeneration in mammals is restricted to distal amputations of the digit tip, the terminal phalanx (P3). In mice, P3 regeneration is mediated via the formation of a blastema, a transient population of progenitor cells that form from the blending of periosteal and endosteal/marrow compartmentalized cells that undergo differentiation to restore the amputated structures. Compartmentalized blastema cells are formed independently, and periosteal compartment-derived cells are required for restoration of amputated skeletal length. P3 regenerative capacity is progressively attenuated at increasingly more proximal amputation levels, eventually resulting in regenerative failure. The continuum of regenerative capacity within the P3 wound milieu is a unique model to investigate mammalian blastema formation in response to distal amputation, as well as the healing response associated with regenerative failure at proximal amputation levels. We report that P3 proximal amputation healing, previously reported to result in regenerative failure, is not an example of complete regenerative failure, but instead is characterized by a limited bone regeneration response restricted to the endosteal/marrow compartment. The regeneration response is mediated by blastema formation within the endosteal/marrow compartment, and blastemal osteogenesis progresses through intramembranous ossification in a polarized proximal to distal sequence. Unlike bone regeneration following distal P3 amputation, osteogenesis within the periosteal compartment is not observed in response to proximal P3 amputation. We provide evidence that proximal P3 amputation initiates the formation of fibrotic tissue that isolates the endosteal/marrow compartment from the periosteal compartment and wound epidermis. While the fibrotic response is transient and later resolved, these studies demonstrate that blastema formation and fibrosis can occur in close proximity, with the regenerative response dominating the final outcome. Moreover, the results suggest that the attenuated proximal P3 regeneration response is associated with the absence of periosteal-compartment participation in blastema formation and bone regeneration.

Wound Healing and Wound Care in Neonates: Current Therapies and Novel Options.

To provide wound care information that considers the specific physiology of neonates. This continuing education activity is intended for physicians, physician assistants, nurse practitioners, and nurses with an interest in skin and wound care. After participating in this educational activity, the participant will:1. Differentiate the use of hydrocolloids, hydrogels, foam dressings, and barrier creams in the neonatal population.2. Identify issues related to the use of solvents, alginates, collagen dressings, and negative-pressure wound therapy in neonates. OBJECTIVETo discuss what is known about the wound milieu in premature and full-term neonates, including the unique challenges pediatric clinicians face, the therapies that have proven effective, and the therapies contraindicated for use in neonatal wound healing to guide treatment that accounts for the specific physiological characteristics of this often overlooked population. Data were collected on neonatal wound healing from a wide variety of sources, including PubMed, Google Scholar, journals, and textbooks. Selection criteria included publications focused on the differences and nuances of wound healing in neonates in comparison with all other age groups. Data were extracted based on articles covering wound healing therapies with proven effectiveness in neonates. Terms for neonatal wound care were compiled, and then a comprehensive literature search was performed by the authors. Although many therapies are safe for treatment of older children and adolescents, most have not been explicitly tested for neonatal use. This article reviews therapies with proven effectiveness and/or specific concerns in the neonatal population. This review sheds light on the advantages and disadvantages of current standards of care regarding wound healing for neonates to direct researchers and clinicians toward developing treatments specifically for this delicate population.

Biological characterization of dehydrated amniotic membrane allograft: Mechanisms of action and implications for wound care.

There is a growing clinical demand in the wound care market to treat chronic wounds such as diabetic foot ulcers. Advanced cell and tissue-based products (CTPs) are often used to address challenging chronic wounds where healing has stalled. These products contain active biologics such as growth factors and cytokines as well as structural components that support and stimulate cell growth and assist in tissue regeneration. This study addresses the in vitro biologic effects of a clinically available dehydrated amniotic membrane allograft (DAMA). The broad mechanism of action results from DAMA's biologic composition that leads to stimulation of cell migration cell proliferation, and reduction of pro-inflammatory cytokines. Results show that DAMA possesses growth factors and cytokines such as EGF, FGF, PDGFs, VEGF, TGF-β, IL-8, and TIMPs 1 and 2. Furthermore, in vitro experiments demonstrate that DAMA stimulates cell proliferation, cell migration, secretion of collagen type I, and the reduction of pro-inflammatory cytokines IL-1β, IL-6, and TNF-α. This study findings are consistent with the clinical benefits previously published for DAMA and other CTPs in chronic wounds suggesting that the introduction of DAMA to non-healing, complex wounds helps to improve the wound milieu by providing essential structural components, cytokines, and growth factors to create an appropriate environment for wound healing.

Modulation of Epidermal Growth Factor Release by Biopolymer-Coated Liposomes

This work describes the development of polysaccharide-coated liposomes to modulate the delivery of epidermal growth factor (EGF), with the aim to produce different EGF release profiles depending on the milieu of infected wounds. For this purpose, cationic liposomes were coated with one layer of sodium alginate (ALG) followed by one layer of chitosan (CHI) using the layer-by-layer (LbL) technique. The coated liposomes exhibited apparent hydrodynamic diameters of 278 ± 36 and 216 ± 96 nm for Lip-ALG and Lip-ALG-CHI, respectively. Thus, it appears that adding the CHI layer compacted the Lip-ALG one. The incorporation efficiency of EGF was a maximum of 55% for liposomes with a polymeric coating. In vitro release experiments showed that Lip-ALG-CHI exhibits a higher release rate constant under acidic pH conditions, resembling those of infected tissue. Using an ex vivo model of EGF release in porcine ear skin, these liposomes were found to accumulate in the epidermis. Thus, coated liposomes could represent a local EGF delivery mechanism to promote healing.

Antimicrobial Biohybrid Nanofibrous Wound Dressings

Globally, chronic wounds impose a notable burden to patients and healthcare systems. Such non-healing wounds are readily subjected to bacteria that provoke inflammation and hence challenge the healing process. Furthermore, bacteria induce infection impeding re-epithelialization and collagen synthesis, thereby increasing hospital stay and costs. Appropriate wound dressing materials alleviate the infection incidence and accelerate the healing process. In this regard, biopolymeric nanofibers show promising potential for prevention of infection and promotion of the healing rate. They are biocompatible and mostly biodegradable and biomimic the extracellular matrix structure. Also, they provide a high surface area, surface nanoporosity, and the ability to deliver drugs and antibiotics locally into the wound milieu. Drug delivery by nanofibers has proved efficient in the control of infection. Yet, due to emergence of antibiotic resistant bacteria, there is an urgent need to replacing the antibiotic delivery systems with other reliable options such as bionanohybrids containing antimicrobial nanoparticles/ions, nature-derived compounds and biofunctional agents. Here, the most recent (since 2015) developments of antimicrobial biopolymeric nanofibrous wound dressings, particularly those based on bionanohybrids, are reviewed and evaluated in terms of antimicrobial efficiency. Lastly, the prospects and challenges are discussed to draw a roadmap for further progresses in this area.

CD163 overexpression using a macrophage-directed gene therapy approach improves wound healing in ex vivo and in vivo human skin models.

Large tissue damage or wounds cause serious comorbidities and represent a major burden for patients, families, and health systems. Due to the pivotal role of immune cells in the proper resolution of inflammation and tissue repair, we focus our current study on the interaction of macrophages with skin cells, and specifically on the effects of CD163 gene induction in macrophages in wound healing. We hypothesize that the over-expression of the scavenger receptor gene CD163 in human macrophages would result in a more efficient wound healing process. Using 3D human wounded skin organotypic tissues, we observed that CD163 overexpression in THP-1 and human primary macrophages induced a more efficient re-epithelization when compared to control cells. Using human primary skin cells and an in vitro scratch assay we observed that CD163 overexpression in THP-1 macrophages promoted a more rapid and efficient wound healing process through a unique interaction with fibroblasts. The addition of CD163-blocking antibody, but not isotype control, blocked the efficient wound healing process induced by CD163 overexpression in macrophages. We found that the co-culture of skin cells and CD163 overexpressing macrophages reduced monocyte chemoattractant protein (MCP)-1 and enhanced tumor growth factor (TGF)-α, without altering interleukin (IL)-6 or TGF-β. Our findings show that CD163 induces a more efficient wound healing and seems to promote a wound milieu with a pro-resolution molecular profile. Our studies set the foundation to study this approach in in vivo clinically relevant settings to test its effects in wound healing processes such as acute major injuries, large surgeries, or chronic ulcers.

A near-infrared fluorescent pH sensing film for wound milieu pH monitoring.

Studies have shown that wound pH is a potentially influential factor in the healing process. Due to the flaws of traditional pH measurement approaches, wound pH measurement has not become part of current standard of care. A near-infrared pH-sensitive ratiometric film was created and characterized for measuring wound pH. This film was fabricated by physically absorbing poly (N-isopropyl Acrylamide) nanoparticles conjugated with pH-sensitive (CypHer5E) and pH-insensitive (Cy7) fluorescent dyes into 2-hydroxyethyl methacrylate hydrogel film. The pH pattern on wounds can be indirectly measured by pressing freshly discarded wound dressing on top of the pH-sensitive film and imaging it. In vitro tests show that the film can accurately and rapidly detect a wide range of pH (from pH 4 to 8) in wound milieu. Further, patient studies showed that, by measuring pH on wound contact side of discarded wound gauze, the pH and its non-homogeneous distribution on wounds can be indirectly determined. By comparing patients with different wound conditions, we find that near-infrared pH sensing film can be used to measure wound exudate pH with high accuracy and efficiency. In addition, wound pH determination can provide an accurate assessment of wound healing activity in real time.

Impact of probiotics on pathogen survival in an innovative human plasma biofilm model (hpBIOM)

BackgroundDespite of medical advances, the number of patients suffering on non-healing chronic wounds is still increasing. This fact is attended by physical and emotional distress and an economic load. The majority of chronic wounds are infected of harmful microbials in a protecting extracellular matrix. These biofilms inhibit wound healing. Biofilm-growing bacteria developed unique survival properties, which still challenge the appropriate wound therapy. The present in-vitro biofilm models are not suitable for translational research. By means of a novel in-vivo like human plasma biofilm model (hpBIOM), this study systematically analysed the influence of 3 probiotics on the survival of five clinically relevant pathogenic microorganisms.MethodsHuman plasma was used to produce the innovate biofilm. Pathogenic microorganisms were administered to the plasma. By stimulating the production of a fibrin scaffold, stable coagula-like discs with integrated pathogens were produced. The five clinically relevant pathogens P. aeruginosa, S. aureus, S. epidermidis, E. faecium and C. albicans were challenged to the probiotics L. plantarum, B. lactis and S. cerevisiae. The probiotics were administered on top of the biofilm and the survival was quantified after 4 h and 24 h of incubation. For statistics, two-way ANOVA with post-hoc Tukey’s HSD test was applied. P-value > 0.05 was considered to be significant.ResultsSEM micrographs depicted the pathogens on the surface of the fibrin scaffold, arranged in close proximity and produced the glycocalyx. The application of probiotics induced different growth-reducing capacities towards the pathogens. B. lactis and S. cerevisiae showed slight bacteria-reducing properties. The survival of C. albicans was not affected at all. The most antimicrobial activity was detected after the treatment with L. plantarum.ConclusionsThis study successfully reproduced a novel human biofilm model, which provides a human wound milieu and individual immune competence. The success of bacteriotherapy is dependent on the strain combination, the number of probiotics and the activity of the immune cells. The eradicating effect of L. plantarum on P. aeruginosa should be emphasized.

Gum acacia-PVA hydrogel blends for wound healing

Hydroactive wound dressings ensure a physiologically moist wound milieu which enhances healing and patient comfort. Polymers like polyurethane, salts of alginic acid, collagen, cellulose and other gelable polysaccharides are commonly used for preparation of hydrogels but have their own limitations. In the present study acacia gum, a natural polysaccharide having known antioxidant and wound healing properties has been blended with polyvinyl alcohol and prepared hydrogel matrix further explored for its wound healing potential. Structural characterization of blended films by FTIR and XRD method showed that polysaccharide gum associated with PVA molecules via acetal bridges and they were amorphous in nature. The gel exhibited free swell capacity of 64 g 0.100 cm−2, which is comparable to the commercially available films recommended for heavily exuding wounds. The GA/PVA blends showed 34% moisture retention (Rh) ability after 24 h and their fluid absorbing (26%) and fluid donation (16%) ability make them suitable for moist and fibrinous wounds. They also exhibited blood compatibility, oxygen permeability, bacterial impermeability, antioxidant activity, iron chelation ability and biodegradability. In vivo healing potential has been evaluated on Swiss albino mice where hydrogel coated wounds showed faster and scar-less wound regeneration. In vitro Povidone-Iodine loading and release studies showed that iodine release followed Fickian diffusion process. Prepared hydrogels are breathable and hydrophilic in nature and are able to maintain appropriate moisture level at wound surface, suitable for acceleration of wound healing process. Based upon the studied properties the designed hydrogels are recommended for dry, necrotic and low exuding wounds.

Nitric oxide regulates intussusceptive-like angiogenesis in wound repair in chicken embryo and transgenic zebrafish models

Angiogenesis is the formation of new blood vessels that occurs by two distinct processes following sprouting angiogenesis (SA) and intussusceptive angiogenesis (IA). Nitric oxide (NO) is known for its pro-angiogenic functions. However, no clear mechanisms are delineated on its role in promoting angiogenesis in reparative wound healing. We propose that NO regulates SA to IA transition and vice versa in wound milieu. We have used three models which include a new chick embryo extra-vasculature (CEV) burn wound model, adult Tie2-GFP transgenic Zebrafish caudal fin regeneration model and Zebrafish skin wound model to study the mechanisms underlying behind the role of NO in wound healing. Wounds created in CEV were treated with NO donor (Spermine NONOate (SPNO)), NOS inhibitor (L-nitro-l-arginine-methyl ester (l-NAME)), NaNO2, NaNO3, and beetroot juice, a nitrite-rich juice respectively and the pattern of wound healing was assessed. Morphological and histological techniques tracked the wound healing at the cellular level, and the molecular changes were investigated by using real-time RT-PCR gene expression analysis. The result concludes that NO donor promotes wound healing by activating SA at an early phase of healing while NOS inhibitor induces wound healing via IA. At the later phase of wound healing NO donor followed IA while NOS inhibitor failed to promote wound repair. The current work underpinned a differential regulation of NO on angiogenesis in wound milieu and this study would provide new insights in designing therapeutics for promoting wound repair.

Outcomes of Split Thickness Skin Grafting on Lower Extremity Wounds in Diabetics

Background: Split thickness skin grafting is a widely used surgical technique for wound coverage. Despite the popularity of this procedure, outcomes data has been poorly reported. Methods: Under IRB approval we reviewed the records of all patients receiving split thickness skin grafting for lower extremity wounds from 2014 to 2016. We have defined success as wound healing of ≥99.5%. Results: 180 diabetic patients were included in this study. 103 (95%) had hypertension, 75 (69%) had hyperlipidemia, 29 (27%) had congestive heart failure, and 22 (20%) had venous stasis. Complete epithelialization was obtained for 29 (22%) patients at 30d, 48 (36%) patients at 60d, 63 (48%) patients at 90d, and 77 (58%) patients at 365d of follow-up. At last available follow-up 79 (60%) wounds obtained complete healing (≥99.5% coverage). Venous stasis led to inadequate healing at 30d (p<0.0371), 90d (p<0.0006), and 365d (p<0.0005) and trended toward significance at 60d (p<0.0809). Congestive heart failure led to inadequate healing at 60d (p<0.0334), and 90d (p<0.0015). The presence of bacteria on wound bed cultures did not show a significant effect on wound healing. The most common bacteria were coagulase negative Staphylococcus, MRSA, and Enterococcus faecalis. Only enterococcus faecalis showed significance at 30d if present following the initial debridement. Conclusion: The data suggests that split thickness skin grafting can be a successful coverage technique for diabetic patients with chronic lower extremity wounds. The bacterial milieu of chronic wounds in diabetics is diverse but with excisional debridement these bacteria have little impact on wound healing after split-thickness skin grafting. However, comorbidities (i.e., congestive heart failure and venous stasis) can significantly impact the healing of skin grafts and should be taken into consideration when contemplating split thickness skin grafting in a diabetic patient. Disclosure E. Walters: None. G. Stimac: None. N. Rajpal: None. I. Naz: None. T. Elmarsafi: None. J. Steinberg: Consultant; Self; Acelity, Integra LifeSciences. K. Evans: None. C. Attinger: Consultant; Self; Acelity, Integra LifeSciences. P. Kim: Consultant; Self; Acelity, Integra LifeSciences.

Engineered delivery strategies for enhanced control of growth factor activities in wound healing.

Growth factors (GFs) are versatile signalling molecules that orchestrate the dynamic, multi-stage process of wound healing. Delivery of exogenous GFs to the wound milieu to mediate healing in an active, physiologically-relevant manner has shown great promise in laboratories; however, the inherent instability of GFs, accompanied with numerous safety, efficacy and cost concerns, has hindered the clinical success of GF delivery. In this article, we highlight that the key to overcoming these challenges is to enhance the control of the activities of GFs throughout the delivering process. We summarise the recent strategies based on biomaterials matrices and molecular engineering, which aim to improve the conditions of GFs for delivery (at the 'supply' end of the delivery), increase the stability and functions of GFs in extracellular matrix (in transportation to target cells), as well as enhance the GFs/receptor interaction on the cell membrane (at the 'destination' end of the delivery). Many of these investigations have led to encouraging outcomes in various in vitro and in vivo regenerative models with considerable translational potential.

Moderators of angiogenesis in muscle flaps: A non-randomised animal study

A muscle flap can survive a pedicle injury under favourable conditions. In the reconstruction of compound limb injuries, the wound milieu is variable and may affect the rate and manner of neovascularisation. Our aim is to determine the effect of some key clinical variables on neovascularisation in muscle flaps in an animal model. The pectoralis profundus was raised in 60 rats and covered with a skin graft. Fifteen rats were allocated to each of the following groups: separation of the flap from the skin inset (S), inflammation by inoculation with Staphylococcus aureus (I), flap elevation with harmonic scalpel (H) and preservation of the motor nerve (N) as well as compared to controls (C). Graft take and wound complications were assessed five days later, as well as perfusion before and after pedicle ligation, by laser Doppler flowmetry and neovascularisation using barium angiography. Flaps with an intact motor nerve had significantly higher graft take than controls (59% vs 29%). Perfusion change was lesser in all study groups than in controls, although the extent of flap necrosis was not significantly different. Only flaps raised with the harmonic scalpel generated more new vessels than controls at the inset (9.6 vs 3.2), particularly at the origin of the muscle (1.10 vs 0.19). All study groups were less dependent on their pedicle for perfusion than controls. The use of the harmonic scalpel and increased inflammation seem pro-angiogenic, although they do not reduce flap necrosis after simulated pedicle injury. Neovascularisation will preferentially bridge to the skin at the inset rather than tissues in the base of the wound. It is likely that flap necrosis is the result of a combination of unfavourable variables rather than one in isolation.

Laser-enabled fabrication of flexible and transparent pH sensor with near-field communication for in-situ monitoring of wound infection

The pH of the wound milieu can provide valuable information regarding wound condition as related to early diagnosis of infection. Existing devices for measurement of wound pH are often expensive with readout systems that require trained personnel, making them impractical for clinical or home usage. This work reports on the development of a low-cost smartphone-based pH sensing platform that consists of a disposable, flexible, and transparent pH sensor interfaced with a custom-designed flexible, battery-less, and reusable near-field communication tag. The fabrication of the disposable potentiometric pH sensor, combines low-cost screen-printing with electro-polymerization of polyaniline on transparent electrodes that are fabricated by direct laser scribing of indium tin oxide (ITO) films. The sensors have a high sensitivity of −55 mV/pH within the physiologically relevant range of pH 4–10, with optical transparency to enable visual inspection of the underlying tissue. The sensor was demonstrated to successfully monitor pH changes in simulated in vitro wound conditions infected with gram-positive Staphylococcus epidermidis, as a proof-of-concept towards future use in vivo. Biocompatibility of all the materials used in the sensor was confirmed with dermal fibroblast cells (Clone B52).