Uptake of PHMB in a bacterial nanocellulose-based wound dressing: A feasible clinical procedure

BackgroundWith the increase of antimicrobial resistance in recent decades, other methods of preventing and fighting infections must be considered. Burn patients, whose wound areas are often extensive, are especially prone to wound infections. The loading of bacterial nanocellulose (BNC) with antiseptics has already been successfully performed but unfortunately, the described procedure is time-consuming and thus not applicable in a clinical emergency setting. Therefore, a clinically feasible approach was established.Material and methodsSheets of BNC-based wound dressings were placed into antiseptic solutions containing PHMB (Prontosan^® and LAVANID^® 2) and were left to soak for up to two hours. At different time points, samples were analysed for their concentration of PHMB and antiseptic efficacy.ResultsWithin 30 min, clinically relevant concentrations of PHMB were achieved in the BNC-based wound dressing. The 30-min PHMB uptake for Prontosan^® and LAVANID^® 2 resulted in concentrations of 0.05% and 0.019%, respectively. Samples from the PHMB loaded dressing showed a dose dependent antiseptic efficacy for Staphylococcus aureus.ConclusionThis experiment showed that the loading of BNC-based wound dressings with PHMB-containing antiseptics was achieved by a simple and quick procedure. According to studies a PHMB concentration of 0.001% can already inhibits all bacterial growth, indicating that the concentrations of PHMB in the BNC-based wound dressings after 30 min are higher than the minimal inhibitory concentration and the antiseptic efficacy after 120 min loading analysed by an standardized bacterial disk diffusion assay was shown to be comparable to the clinically used Suprasorb^® X + PHMB wound dressing.     

Evaluation of a bi-layer wound dressing for burn care I. Cooling and wound healing properties

Severe burns remain a significant cause of morbidity and mortality despite the availability of numerous therapies. We assessed the wound healing and skin-cooling properties of a DRDC hydrogel/polyurethane wound dressing using different pre-clinical models. Our results show that 85% of partial-thickness, non-contaminated porcine wounds treated with our dressing healed within 6 days. In contrast, 85% of the wounds treated with commercial dressings healed within 8 days. Application of a moist DRDC dressing (to simulate a condition of exudate absorption) on a scald burn covering 25% of the dorsal area in rats reduced skin temperature by 1.70 +/- 0.14 degrees C for 5 min, the skin temperature being comparable to that of control burned rats after 20 min. The application of a moist DRDC dressing did not induce significant differences in body temperatures compared with that of burned animals without dressing coverage throughout the 90-min experiment. While no change in body temperatures were observed when standard dressings (i.e., not pre-moistened) were applied, skin temperature increased gradually. These data show that our dressing is effective in promoting faster healing of the treated wound; and providing a transient, but beneficial cooling effect to the skin contact-site, without the adverse effect of inducing whole-body hypothermia.     

A novel human ex-vivo burn model and the local cooling effect of a bacterial nanocellulose-based wound dressing

BackgroundBurn wound progression is a significant problem as burns initially thought to be superficial can actually become full thickness over time. Cooling is an efficient method to reduce burn wound conversion. However, if the cooling agent is below room temperature, depending on the wound size the patient is at risk of hypothermia. Additionally, tissue perfusion is reduced leading to an aggravation of burn wound progression. We investigated if wound dressings based on non-pre-cooled bacterial nanocellulose (BNC) with a high water content cool a burn just by evaporation and reduce the intradermal damages in the skin.Material and methodsIn a human ex-vivo model, skin explants underwent contact burns using a 100 °C hot steel block. The burned areas were divided into two groups of which one was cooled with a BNC-based wound dressing. Intradermal temperature probes measured temperature in cooled and uncooled burn sites over 24 h. For histological assessments of the burned areas biopsies were taken at different time points. High mobility group box-1 (HMBG1) staining served as marker for cell vitality and necrosis in the different skin layers.ResultsIntradermal temperature measurement showed that application of the BNC-based wound dressing reduced temperature significantly in burned skin. This cooling effect resulted in a maximum temperature difference of 6.4 ± 1.9 °C and a significant mean reduction of the area under the curve in the first hour after burn of 62% (p < 0.0001). The histological results showed less necrosis and less dermal-epidermal separation in the cooled areas. The HMGB1 staining revealed more vital cells in the cooled group than in the uncooled group.ConclusionBased on our results, BNC-based wound dressings cool a burn. Intradermal temperature as well as thermal damage of the tissue was reduced. The tested BNC-based wound dressing can be used without pre-cooling to cool a burn as well as to reduce the burn BNC-based wound progression through its evaporation cooling effect.     

Use of a new hemicellulose dressing (Veloderm) for the treatment of split-thickness skin graft donor sites A within-patient controlled study

A multi-centre, open, within-patient controlled study was performed on 23 adult burnt patients to investigate the effectiveness, safety and tolerability of Veloderm^® in comparison with Algisite M™ and Jaloskin^® in split-thickness skin graft donor site care. The areas dressed with Veloderm^® completely healed within 10–13 days in a significant higher proportion than the other two dressings (47.6% for Veloderm^® versus 26.3% for Algisite M™ and 10% for Jaloskin^®, P < 0.03), showing during the whole study less incidence of exudates and of peri-lesional erythema. The aesthetic outcome of the treated lesions after healing was significantly better for Veloderm^® (P = 0.0016). Veloderm^® and Jaloskin^® required very few renewals of the medication during the first week of treatment, while Algisite M™ needed several multiple re-dressings. Veloderm^® was judged better than the other two treatments as far as the acceptability (P < 0.001), ease of use (P < 0.001) and efficacy (P < 0.00001). Both pain during application or at removal of dressings and local infections were negligible with all treatments. No scars were formed in any skin donor site. In conclusion Veloderm^® is a safe and effective dressing for the re-epithelialization of the skin graft donor sites: it showed higher activity than the other two compared dressings.     

In vivo study of the efficacy of bupivacaine-eluting novel soy protein wound dressings in a rat burn model

Dealing with wound related pain is an integral part of treatment. Systemic administration of analgesic and anesthetic agents is a common solution for providing pain relief to patients but comes at a risk of severe side effects as well as addiction. To overcome these issues, research efforts were madeto provide a platform for local controlled release of pain killers. We have developed a bilayer soy protein-based wound dressing for the controlled local release of bupivacaine to the wound site. The combination of a dense and a porous layer provides a platform for cell growth and proliferation as well as physical protection to the wound site. The current study focuses on the in vitro bupivacaine release profile from the dressing and the corresponding in vivo results of pain levels in a second-degree burn model on rats. The Rat Grimace Scale method and the Von Frey filaments method were used to quantify both, spontaneous pain and mechanically induced pain. A high burst release of 61.8 ± 1.9% of the loaded drug was obtained during the initial hour, followed by a slower release rate during the following day. The animal trials show that the RGS scores of the bupivacaine-treated group were significantly lower than these of the untreated group, proving a decrease of 51–68% in pain levels during days 1–3 after burn. Hence, successful pain reduction of spontaneous pain as well as mechanically induced pain, for at least three days after burn was achieved. It is concluded that our novel bupivacaine eluting soy protein wound dressings are a promising new concept in the field of local controlled drug release for pain management.     

Preclinical assessment of novel longer-duration wear negative pressure wound therapy dressing in a porcine model

While reticulated open cell foam (ROCF) is a well-established dressing for negative pressure wound therapy (NPWT), there is the known potential for granulation tissue ingrowth if left in place for longer than 72 h. This may cause wound bed disruption, bleeding, and pain upon dressing removal. In addition, any retained foam fragments may elicit an adverse tissue reaction. A novel, easy to use dressing designed to utilise the advantages of ROCF while addressing its challenges has recently been created. This 7 day study investigated the utility of a novel NPWT dressing under longer-duration wear circumstances while assessing the prevalence of tissue ingrowth and ease of dressing removal in full-thickness excisional wounds utilising a porcine model. Histopathology and morphometry evaluations indicated thicker granulation tissue with, depending on the parameters assessed, either comparable or better tissue quality for wounds treated with the novel dressing. Greater re-epithelialization levels were also evident compared with ROCF. Three-dimensional imaging analysis indicated faster wound fill with a corresponding decrease in wound area with the novel dressing. Furthermore, tissue ingrowth was limited to only ROCF-treated wounds, which was not unexpected in this longer-duration wear study. The force required to remove the novel dressing was considerably lower compared with ROCF, correlating to the tissue ingrowth results. Results of this study illustrate that the novel dressing provided more favourable wound healing results compared with traditional ROCF. In addition, reduction in the risk of tissue ingrowth and low dressing peel force may allow it to be used as a longer-wear dressing.     

A recombinant signalling-selective activated protein C that lacks anticoagulant activity is efficacious and safe in cutaneous wound preclinical models

Various preclinical and clinical studies have demonstrated the robust wound healing capacity of the natural anticoagulant activated protein C (APC). A bioengineered APC variant designated 3K3A-APC retains APC's cytoprotective cell signalling actions with <10% anticoagulant activity. This study was aimed to provide preclinical evidence that 3K3A-APC is efficacious and safe as a wound healing agent. 3K3A-APC, like wild-type APC, demonstrated positive effects on proliferation of human skin cells (keratinocytes, endothelial cells and fibroblasts). Similarly it also increased matrix metollaproteinase-2 activation in keratinocytes and fibroblasts. Topical 3K3A-APC treatment at 10 or 30 μg both accelerated mouse wound healing when culled on Day 11. And at 10 μg, it was superior to APC and had half the dermal wound gape compared to control. Further testing was conducted in excisional porcine wounds due to their congruence to human skin. Here, 3K3A-APC advanced macroscopic healing in a dose-dependent manner (100, 250 and 500 μg) when culled on Day 21. This was histologically corroborated by greater collagen maturity, suggesting more advanced remodelling. A non-interference arm of this study found no evidence that topical 3K3A-APC caused either any significant systemic side-effects or any significant leakage into the circulation. However the female pigs exhibited transient and mild local reactions after treatments in week three, which did not impact healing. Overall these preclinical studies support the hypothesis that 3K3A-APC merits future human wound studies.     

A human skin equivalent burn model to study the effect of a nanocrystalline silver dressing on wound healing

In this study, a deep burn wound model was established using a 3D human skin equivalent (HSE) model and this was compared to native skin. HSEs were constructed from dermis derived from abdominoplasty/breast surgery and this dermal template was seeded with primary keratinocytes and fibroblasts. The HSE model was structurally similar to native skin with a stratified and differentiated epidermis. A contact burn (60 °C, 80 °C, 90 °C) was applied with a modified soldering iron and wounds were observed at day 1 and 7 after burn. The HSEs demonstrated re-growth with keratinocyte proliferation and formation of a neo-epidermis after burn injury, whereas the ex vivo native skin did not. To assess the suitability of the 3D HSE model for penetration and toxicity studies, a nanocrystalline silver dressing was applied to the model for 7 days, with and without burn injury. The effect of silver on skin re-growth and its penetration and subcellular localization was assessed in HSEs histologically and with laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS). The silver treatment delayed or reduced skin re-growth, and silver particles were detected on the top of the epidermis, and within the papillary dermis. This novel in vitro 3D multicellular deep burn wound model is effective for studying the pathology and treatment of burn wound injury and is suitable for penetration and toxicity studies of wound healing treatments.     

Early intervention by Captopril does not improve wound healing of partial thickness burn wounds in a rat model

The Renin Angiotensin System is involved in fibrotic pathologies in various organs such as heart, kidney and liver. Inhibition of this system by angiotensin converting enzyme antagonists, such as Captopril, has been shown beneficial effects on these pathologies. Captopril reduced the inflammatory reaction but also directly influenced the fibrotic process.Prolonged and excessive inflammatory response is a major cause of hypertrophic scar formation in burns. We therefore evaluated the effect of Captopril on the healing of partial thickness burn wounds in a rat model.Partial thickness contact burns were inflicted on the dorsum of the rats. The rats received either systemic or local treatment with Captopril. The inflammatory reaction and wound healing (scar) parameters were investigated and compared to control animals.In this study we could not detect positive effects of either administration route with Captopril on the inflammatory reaction, nor on wound healing parameters. The local treatment showed reduced wound closure in comparison to the systemic treatment and the control group.Early Captopril treatment of burn wounds did not show the beneficial effects that were reported for fibrotic disorders in other tissues. To influence the fibrotic response Captopril treatment at a later time point, e.g. during the remodeling phase, might still have beneficial effects.     

Evaluation of warm ischemia-reperfusion injury using heat shock protein in the rat liver

We focused on heat shock protein 70 (HSP70) as a marker of viability in hepatic warm ischemia-reperfusion. Segmental hepatic warm ischemia was produced in rats for 15, 30, 60, 90, 120, or 180 min. Liver sections were evaluated at 30, 60, and 120 min of reperfusion. Expression of HSP70 and messenger RNA (mRNA), apoptosis, and apoptosis-associated genes such as Bcl-2 and Bax were studied. Expression of HSP70 and mRNA was augmented as warm ischemia was prolonged, but was markedly suppressed in livers with more than 120 min of ischemia. The highest accumulation of HSP70 was observed in the nucleus. In livers subjected to longer duration of warm ischemia, necrosis and apoptosis were evident and Bcl-2 mRNA expression and Bcl-2/Bax protein ratio were markedly diminished. Apoptosis may be related to the process of cellular injury induced by warm ischemia-reperfusion. Expression of HSP70 and the Bcl-2 family can be effective markers of viability in hepatic warm ischemia-reperfusion.     

Effectiveness of using a new polyurethane foam multi‐layer dressing in the sacral area to prevent the onset of pressure ulcer in the elderly with hip fractures: A pragmatic randomised controlled trial

Hip fractures in the elderly are a serious problem for the health service due to the high rate of complications. One of these complications is pressure ulcers that, according to the literature, occur in 8.8% to 55% of patients and mainly arise in the sacral area. The present randomised controlled trial tests whether applying a new innovative multi‐layer polyurethane foam dressing (ALLEVYN LIFE™), reduces the onset of pressure ulcers in the sacral area. From March to December 2016, 359 fragility hip fracture patients were randomly divided into 2 groups: 182 in the control group and 177 in the experimental group. Pressure ulcers occurred overall in 36 patients (10%): 8 patients (4.5%) in the experimental group compared to 28 (15.4%) in the control group: P = 0.001, relative risk 0.29 (95% CI 0.14‐0.61) with NNT of 9 (95% CI 6‐21). In the experimental group the onset of pressure ulcers occurred on average on the 6th day compared to the 4th day in the control group (HR 4.4). Using polyurethane foam is effective at reducing the rate of pressure ulcers in the sacrum in elderly patients with hip fracture. The adhesiveness of this device also enables costs to be kept down.     

BMP-HA人工听骨在显微外科鼓室成形术中的应用

目的探时骨形态发牛蛋白(BMP)复合多孔羟基磷灰石(HA)人工听骨在鼓室成形术的应用效果，以寻找较理想的听骨链重建材料。方法回顾分析1999至2001年间采用BMP复合HA人工听骨行鼓室成形术63例(69耳)，其中45耳用部分听骨赝复物(PORP)，24耳用全听骨赝复物(TORP)、结果术后听力提高超过15dB HL者65耳(94．2％)，气骨导差小于20dB HL者48耳(69．6％)，听力达应用水平者55耳(79．7％)，尢排斥反应，无听骨脱出，无中耳炎复发。结论BMP／HA人工听骨生物相容好，是一种理想的中耳传音结构重建材料     

The wound‐healing effects of a next‐generation anti‐biofilm silver Hydrofiber wound dressing on deep partial‐thickness wounds using a porcine model

Topical antimicrobials are widely used to control wound bioburden and facilitate wound healing; however, the fine balance between antimicrobial efficacy and non‐toxicity must be achieved. This study evaluated whether an anti‐biofilm silver‐containing wound dressing interfered with the normal healing process in non‐contaminated deep partial thickness wounds. In an in‐vivo porcine wound model using 2 pigs, 96 wounds were randomly assigned to 1 of 3 dressing groups: anti‐biofilm silver Hydrofiber dressing (test), silver Hydrofiber dressing (control), or polyurethane film dressing (control). Wounds were investigated for 8 days, and wound biopsies (n = 4) were taken from each dressing group, per animal, on days 2, 4, 6, and 8 after wounding and evaluated using light microscopy. No statistically significant differences were observed in the rate of reepithelialisation, white blood cell infiltration, angiogenesis, or granulation tissue formation following application of the anti‐biofilm silver Hydrofiber dressing versus the 2 control dressings. Overall, epithelial thickness was similar between groups. Some differences in infiltration of specific cell types were observed between groups. There were no signs of tissue necrosis, fibrosis, or fatty infiltration in any group. An anti‐biofilm silver Hydrofiber wound dressing did not cause any notable interference with normal healing processes.     

杀菌/通透性增加蛋白对内毒素休克大鼠微循环灌注的保护作用

目的 探讨杀菌／通透性增加蛋白（ＢＰＩ）对内毒素休克时血液动力学和内脏微徨灌注的保护作用及其机制。方法 采用大鼠内毒素休克模型,动态观察血液动力学、内脏微循环灌注量和血浆生物喋吟、一氧化氮（ＮＯ）水平的变化。结果 休克早期给予重组ＢＰＩ,可显著提高平均支流压、心脏指数及每搏输出量,明显改善肝、肾、小肠抽徨灌注量及动物预后（Ｐ〈０．０５～０．０１）,循环ＮＯ产生亦不同程度受到抑制。结论 早期应用ＢＰ     

Directing the expression of a green fluorescent protein transgene in differentiated osteoblasts: comparison between rat type I collagen and rat osteocalcin promoters

The osteocalcin (OC) and a 2.3 kb fragment of the collagen promoter (Col2.3) have been used to restrict transgenic expression of a variety of proteins to bone. Transgenic mice carrying a green fluorescent protein (GFP) gene driven by each promoter were generated. Strong GFP expression was detected in OC-GFP mice in a few osteoblastic cells lining the endosteal bone surface and in scattered osteocytes within the bone matrix in long bones from 1-day-old to 6-month-old transgenic animals. Similar findings were noted in the forming tooth in which only individual odontoblasts expressed GFP without detectable expression from the dental pulp. This limited pattern of OC-GFP-positive cells contrasts with the uniform expression in the Col2.3GFP mice in which large proportion of osteoblasts, odontoblasts, and osteocytes strongly expressed the transgene. To assess transgene expression during in vitro differentiation, marrow stromal cell and neonatal calvarial osteoblast cultures were analyzed. The activity of both transgenes was restricted to mineralized nodules but the number of positive cells was lower in the OC-GFP-derived cultures. The different temporal and spatial pattern of each transgene in vivo and in vitro reveals potential advantages and disadvantages of these two transgene models.     

Evaluation of a novel reconstituted bone xenograft using processed bovine cancellous bone in combination with purified bovine bone morphogenetic protein

Long B, Dan L, Jian L, Yunyu H, Shu H, Zhi Y. Evaluation of a novel reconstituted bone xenograft using processed bovine cancellous bone in combination with purified bovine bone morphogenetic protein. Xenotransplantation 2012; 19: 122–132. © 2012 John Wiley & Sons A/S. Abstract: Background: Xenogeneic grafting represents an alternative to autogenous grafting in osseous reconstruction and exhibits many beneficial properties. However, the usefulness of xenogeneic bone relies on necessary processing procedures for removing antigens and viruses, and preserving biological activities simultaneously. By chemical treatment of bovine cancellous bone to make it an antigen‐free scaffold, and extraction of bone morphogenetic protein (BMP) from bovine cortical bone, followed by recombination of the scaffold with the BMP, we developed a new grafting material, reconstituted bone xenograft (RBX). Methods: In this study, scanning electron microscope and energy dispersive X‐ray were first employed to observe the structure and components of RBX. Then the biomechanical property was evaluated by applying compression in a materials testing machine. Subsequently, the immunologic evaluation was performed by measuring galactose‐alpha‐1,3‐galactose (α‐gal) epitope in vivo and proinflammatory cytokine (TNF‐α) secreted by human monocytic cell line (THP‐1) in vitro. Finally, this RBX was implanted into segmental radial defects in a rabbit model, and its ability to treat large bone defects was specifically evaluated. Results: Although the compressive strength of RBX was 10% lower than that of unprocessed bovine cancellous bone (UBCB), the basic porous structure and natural components were still kept in this composite. The α‐gal xenoantigen level was significantly lower in RBX (P < 0.05) compared with UBCB. Moreover, the TNF‐α level was significantly (P < 0.05) reduced compared with UBCB when THP‐1 was exposed to RBX. On the other hand, RBX appeared to induce cartilage formation from immature cell populations and resulted in osteogenesis through endochondral‐like ossification from 4 to 12 weeks in repairing segmental bone defects. Conclusions: These results demonstrate that RBX, with its natural microstructure and components, certain mechanical strength and strong osteoinductivity without evoking immune rejection, has significant potential for the treatment of bone defects.     

A proof‐of‐concept study of the removal of early and late phase biofilm from skin wound models using a liquid acoustic stream

Chronic wounds fail to progress through the normal stages of healing, with the largest remediable cause of chronicity being presence of a multi‐species biofilm. Removal of biofilm from the wound environment is central to wound care. A device for mechanically removing biofilms from wounds has been devised. The removal is caused by small‐scale liquid currents and shear, generated by acoustically activated microscopic air bubbles. These bubbles and acoustic waves are delivered onto the wound by a gentle liquid stream, allowing cleaning in situ and removal of debris in the run‐off liquid. We have investigated if this liquid acoustic wound stream (LAWS) can remove bacterial biofilm from soft biological wound models and studied the effect of LAWS on the cellular tissues of the substrate. LAWS will efficiently remove early Pseudomonas aeruginosa biofilm from an artificial wound in a pig''s trotter, 24 hours‐mature biofilm of P. aeruginosa from a pre‐wounded human full thickness skin model (EpiDerm FT), and 3‐day mature biofilm of P. aeruginosa or Staphylococcus aureus from a porcine skin explant. Histological examinations of uninfected EpiDerm models that had been treated by LAWS and then stained with Haematoxylin and Eosin, demonstrated no damage to the human tissue, and wound diameter was smaller in the treated skin models compared with untreated samples. Immunofluorescence staining for cytokeratin 14 showed that keratinocytes had migrated further across the wound in the uninfected samples treated by LAWS. We discuss the implications for wound healing and propose further laboratory and clinical studies to demonstrate the removal of biofilm from patients with chronic leg ulcers and the impact on healing.