亲水性纤维含银敷料覆盖肛瘘术后创面的作用

背景：亲水性纤维含银敷料在其他创面治疗中目前已取得较多临床证据,但其 对肛瘘患者术后创面康复的作用研究较少。 目的：观察亲水性纤维含银敷料覆盖对肛瘘患者术后创面康复的作用。 方法：将57例肛瘘术后患者随机分为试验组29例和对照组28例,试验组在术后给予亲水性纤维含银敷料换药,3 d 1次,对照组术后给予无菌凡士林纱布换药,1次/d,观察两组患者的首次换药创面疼痛程度、渗液明显减少时间、换药次数、创面康复时间及换药费用等指标。 结果与结论：试验组首次换药时创面疼痛程度明显轻于对照组(P < 0.05),渗液明显减少时间、换药次数、创面康复时间明显少于对照组(P < 0.05);但试验组换药费用明显高于对照组(P < 0.05)。表明亲水性纤维含银敷料覆盖于肛瘘患者术后创面可减少刺激,明显减轻疼痛,提供湿性修复环境,加速创面愈合,减少换药次数,提高患者满意度。     

Development of a chitosan-based wound dressing with improved hemostatic and antimicrobial properties

Hemorrhage remains a leading cause of early death after trauma, and infectious complications in combat wounds continue to challenge caregivers. Although chitosan dressings have been developed to address these problems, they are not always effective in controlling bleeding or killing bacteria. We aimed to refine the chitosan dressing by incorporating a procoagulant (polyphosphate) and an antimicrobial (silver). Chitosan containing different amounts and types of polyphosphate polymers was fabricated, and their hemostatic efficacies evaluated in vitro. The optimal chitosan-polyphosphate formulation (ChiPP) accelerated blood clotting (p = 0.011), increased platelet adhesion (p=0.002), generated thrombin faster (p = 0.002), and absorbed more blood than chitosan (p < 0.001). Silver-loaded ChiPP exhibited significantly greater bactericidal activity than ChiPP in vitro, achieving a complete kill of Pseudomonas aeruginosa and a > 99.99% kill of Staphylococcus aureus consistently. The silver dressing also significantly reduced mortality from 90% to 14.3% in a P. aeruginosa wound infection model in mice. Although the dressing exerted severe cytotoxicity against cultured fibroblasts, wound healing was not inhibited. This study demonstrated for the first time, the application of polyphosphate as a hemostatic adjuvant, and developed a new chitosan-based composite with potent hemostatic and antimicrobial properties.     

Hyalomatrix: a temporary epidermal barrier, hyaluronan delivery, and neodermis induction system for keratinocyte stem cell therapy

Keratinocyte stem cell technology provides at least an adjuvant therapy to clinically close large cutaneous wounds (e.g., burn wounds). Here, the performance of keratinocyte cultures depends primarily on the quality of the bed to which they are applied. Clinical take rates for cultured keratinocyte grafts are optimal when applied to a vascularized dermal bed with minimal bacterial colonization. In the absence of autologous dermis, staged reconstruction with a dermal equivalent or dermal regeneration template is required. A novel product, Hyalomatrix, is a bilayer of an esterified hyaluronan scaffold beneath a silicone membrane. The scaffold delivers hyaluronan to the wound bed, and the silicone membrane acts as a temporary epidermal barrier. The product has been investigated in a controlled, porcine, acute full-thickness excisional wound model. Cultured autologous keratinocytes (CAKs) were delivered on Laserskin to acute full-thickness wounds treated with Hyalomatrix within chambers, and graft take rates were assessed longitudinally using image analysis. In the absence of chambers, wound contraction was assessed. Clinical CAK take rates fall sequentially with delay in application post-Hyalomatrix pre-treatment, but repeated pre-treatment removed this, with maximal take of 57.2% at 5 weeks post-wounding. In the absence of chambers, more-complete wound closure resulted from edge re-epithelialization and contraction, by a factor of 5 at 1 month, and was achieved at least 2 weeks sooner in the gold standard controls of split-thickness autograft to an acute or pre-treated wound bed. Wound contraction and late neodermal morphology (1 year) were similar in pre-treated CAKs and split-thickness autograft wounds. In this model, the Hyalomatrix wound bed pre-treatment increase in CAK take appeared to be dose dependent. The product appeared to act as a hyaluronan delivery system rather than a dermal regeneration template. The silicone membrane may limit wound bed colonization, and the combination of this temporary barrier with hyaluronan delivery and neodermis induction has been termed a barrier-delivery-induction system. The development of similar systems for serial application offers an alternative to a dermal regeneration template when CAKs are engrafted in the hostile, colonized environment of large burn wounds.     

Impact of heat on nanocrystalline silver dressings. Part I: Chemical and biological properties

Thermal stability of heat-treated nanocrystalline silver dressings was investigated using chemical techniques and biological assays. Dressings were heat-treated for 24h at temperatures from 23 to 110 degrees C. Bactericidal efficacy of heat-treated dressings was measured using a log reduction assay, while antibacterial longevity was determined via plate-to-plate transfer corrected zone of inhibition assays. Over the temperature range tested, biological activity dropped from excellent to negligible. Biological longevity results showed that controlled release properties of the dressings were significantly reduced by heat treatments above 75 degrees C. These data illustrate nanocrystalline silver sensitivity to heat. Further, it was clear that dressing efficacy is determined by total available soluble silver, not total silver in the dressing. It was determined that the quantity of soluble silver decreased significantly with increased heat treatment temperatures. These results should be considered in developing new nanocrystalline drug delivery systems.     

Control of wound infections using a bilayer chitosan wound dressing with sustainable antibiotic delivery.

A novel bilayer chitosan membrane was prepared by a combined wet/dry phase inversion method and evaluated as a wound dressing. This new type of bilayer chitosan wound dressing, consisting of a dense upper layer (skin layer) and a sponge-like lower layer (sublayer), is very suitable for use as a topical delivery of silver sulfadiazine (AgSD) for the control of wound infections. Physical characterization of the bilayer wound dressing showed that it has excellent oxygen permeability, that it controls the water vapor transmission rate, and that it promotes water uptake capability. AgSD dissolved from bilayer chitosan dressings to release silver and sulfadiazine. The release of sulfadiazine from the bilayer chitosan dressing displayed a burst release on the first day and then tapered off to a much slower release. However, the release of silver from the bilayer chitosan dressing displayed a slow release profile with a sustained increase of silver concentration. The cultures of Pseudomonas aeruginosa and Staphylococcus aureus in agar plates showed effective antimicrobial activity for 1 week. In vivo antibacterial tests confirmed that this wound dressing is effective for long-term inhibition of the growth of Pseudomonas aeruginosa and Staphylococcus aureus at an infected wound site. The results in this study indicate that the AgSD-incorporated bilayer chitosan wound dressing may be a material with potential antibacterial capability for the treatment of infected wounds.     

纳米银抗菌医用敷料创面外用后纳米银在体内的分布

背景：纳米银以小尺寸效应、量子效应和极大的比表面积优势,较传统银制品抗菌效果更为突出,但有关其进入体内后产生的负面生物效应或不良反应尚不明确。 目的：观察创面外用纳米银敷料后纳米银在兔体内的分布变化。  方法：将新西兰白兔以抽签法随机分为正常对照组(创面自然愈合)、单次敷料组(又分为6小组)、多次敷料组(分为6小组)。均于兔双耳腹侧制作创面,单次敷料组单次使用纳米银敷料外敷,不更换敷料;多次敷料组多次使用纳米银敷料外敷,其6小组分别于0 d,2 d,2 d和4 d,2 d和4 d,2 d和4 d,2 d和4 d更换敷料。于创面制作后2,4,7,14,30,60 d检测兔血、肝、肾、脾中银浓度。 结果与结论：应用纳米银敷料2d后,单次敷料组、多次敷料组血液、肝、肾、脾中银浓度均明显高于正常对照组(P < 0.01)。应用第4天,单次敷料组、多次敷料组各脏器银浓度仍明显高于正常对照组(P < 0.01),但多次敷料组各脏器银浓度随时间呈进行性上升趋势,而单次敷料组各脏器银浓度呈进行性下降,这种变化在第7天时更为明显,多次敷料组各脏器银浓度显著高于单次敷料组(P < 0.01)。移除纳米银敷料后,单次敷料组、多次敷料组各脏器银含量均较前一时间点银浓度显著降低,尤以多次敷料组更为明显(P < 0.01)。制作创面后第30,60天,单次敷料组、多次敷料组各脏器银浓度与正常对照组已无差异(P > 0.05)。说明纳米银敷料用于创伤创面时能迅速入血,通过血液循环分布于肝、肾、脾等脏器;移除敷料后,血、肝、肾、脾中纳米银含量迅速下降至正常值,不会产生累积现象。     

藻酸盐敷料联合rhGM-CSF用水胶体封闭治疗肌腱、骨外露的疗效研究

目的探讨藻酸盐敷料联合重组人粒细胞巨噬细胞集落刺激因子(rhGM-CSF)凝胶和莫匹罗星软膏混合物覆盖创面后，用水胶体敷料封闭肌腱、骨外露创面的临床疗效。 方法选取2018年10月至2020年5月在达州市中心医院烧伤整形科住院和伤口治疗中心门诊治疗的肌腱、骨外露面积>0. 5 cm²的50例患者，采用抽签法分为实验组(藻酸盐＋rhGM-CSF＋莫匹罗星软膏＋水胶体封闭)和对照组(凡士林油纱＋rhGM-CSF＋莫匹罗星软膏)，每组各25例。连续观察肉芽组织完全覆盖外露肌腱、骨所需时间、创面愈合时间、前3次换药时疼痛视觉模拟评分(VAS)。数据比较采用t检验和χ²检验。 结果实验组肉芽组织完全覆盖外露肌腱、骨所需时间(20.556±10.214) d少于对照组(28.040±11.929)d，差异有统计学意义(t＝2.436，P＝0.019)；实验组创面愈合时间(30.778±12.762) d少于对照组[(40.600±17.231) d]，差异有统计学意义(t＝2.348，P＝0.023)；前3次换药实验组VAS(1.893±0.924)分明显低于对照组(5.067±1.223)分，差异有统计学意义(t＝17.933，P<0.001)。 结论藻酸盐敷料联合rhGM-CSF和莫匹罗星软膏混合物并用水胶体敷料封闭创面可加速创面肉芽组织生长，使其早期覆盖肌腱、骨骼，加快创面愈合，减轻患者换药疼痛，提高换药效率，降低皮瓣手术率，为无皮瓣手术条件及拒绝皮瓣手术患者提供新的治疗方案，可在门诊及基层医院得到推广。     

Survival of Apligraf in acute human wounds

Apligraf consists of bovine collagen dermis seeded with allogeneic male fibroblasts and keratinocytes. It is been shown to promote healing, but the length of persistence and pathological features have not been characterized previously in acute wounds. Forty-eight deep dermal wounds were created and Apligraf, a split-skin graft (SSG), or a dressing was applied. Biopsies of wounds were taken for immunohistochemical analysis and polymerase chain reaction was performed to detect the Y chromosome from Apligraf cells in 14 female wounds. Male allogeneic DNA was detected in wounds for the first 4 weeks. All subsequent time points were negative apart from one biopsy at 6 weeks. The wounds took 4-9 weeks to heal, with the Apligraf exhibiting no features of engraftment. This was in contrast to the rapid healing seen in the SSG control group. Histology revealed a more intense cellular infiltrate, but less vascularization below Apligraf compared with controls. Evidence of an epidermal-mesenchymal interaction was observed. This is the first article to elucidate the survival of Apligraf allogeneic cells in acute wounds in immunocompetent human subjects for up to 6 weeks and demonstrates that in the management of acute surgical wounds, Apligraf has a role only as a temporary biological dressing.     

-80℃冻干猪二道皮用于Ⅱ度烧伤创面换药方法的改进

目的应用自制-80％冻干猪二道皮（类似仿猪真皮）覆盖Ⅱ度烧伤创面，改进传统的换药方法并评价其效果。方法取小型健康白色家猪的新鲜皮，经常规清洁剃毛，以电动取皮机去脂，制成去表皮刃厚猪二道皮，经处理后放入-80％冰箱冻存备用。临床分为两组：A组为观察组共42例，以猪二道皮覆盖创面，B组为对照组共76例，以10％磺胺嘧啶银霜油纱布传统方法交敷创面。结果浅Ⅱ度创面愈合时间，A组平均（10．67±2．08）天，B组（13．1±1．73）天（P〈0．01）；深Ⅱ度创面愈合时间，A组平均（20．8±2．03）天，B组（23．20±2．60）天（P〈0．01）。结论与传统的换药方法相比，以猪二道皮覆盖烧伤创面，能促进上皮细胞生长，减轻疼痛，缩短愈合时间，减少疤痕和畸形的产生。     

Systematic evaluation of six dressings on wound safety following total hip and knee arthroplasty北大核心

OBJECTIVE: In recent years, the operation rate of total hip and knee arthroplasty has been increasing, and postoperative wounds need to be covered with dressings to protect newborn skin tissues. Choosing a high-safety medical dressing is an important issue at present. This study systematically evaluated the safety of six kinds of medical dressings on wounds after total hip and knee arthroplasty. METHODS: The computer search was conducted on CNKI, Wanfang, VIP and China Biomedical Literature Database, PubMed, Embase, Web of Science, Cochrane Library and Scopus. Clinical studies of different medical dressings applied to wound after total hip and knee arthroplasty were collected. The search time was from the database establishment to December 2021. Two researchers independently screened the literature and extracted the data. Using Stata 16.0 and RevMan 5.4 software, the blister rate of the primary outcome measure was analyzed by network meta-analysis. The infection rate, dressing change times and erythema of the secondary outcome measures were analyzed by meta-analysis. RESULTS: (1) A total of 20 included studies contained 14 randomized controlled trials and 6 cohort studies involving 6 474 patients and 6 dressings, i.e., conventional dressings, thin film dressings, foam dressings, silver ion dressings, hydrophilic fiber silver-containing dressings, and alginate dressings. (2) The results of the network meta-analysis showed that in terms of reducing postoperative wound blister rate, which ranked as follows: alginate dressing (98.6%) > hydrophilic fiber silver dressing (75.4%) > film dressing (45.0%) > foam dressing (37.4%) > silver ion dressing (26.3%) > traditional dressing (2.0%). (3) The results of direct meta-analysis showed that hydrophilic fiber silver dressing was superior to traditional dressing in reducing postoperative wound infection rate and dressing change times [OR=0.36, 95%CI(0.23,0.58), P < 0.05; MD=-1.85, 95%CI(-2.40, -1.30), P < 0.000 01]. There was no statistical significance in reducing postoperative wound erythema (P > 0.05). CONCLUSION: For patients after total hip and knee arthroplasty, alginate dressing has the best overall effect on reducing the rate of postoperative blisters, while hydrophilic fiber silver-containing dressing has the best overall effect on reducing the number of postoperative dressing changes and infection rate. Therefore, these two dressings should be given priority after total hip and knee arthroplasty, and more high-quality randomized controlled trials are needed to confirm this conclusion. © 2023, Chinese Journal of Tissue Engineering Research. All rights reserved.     

Development of fungal mycelia as a skin substitute: characterization of keratinocyte proliferation and matrix metalloproteinase expression during improvement in the wound-healing process

SACCHACHITIN membranes, prepared from the waste residue of the fruiting body of Ganoderma taugae, were used in our previous study to enhance skin wound healing in animal models. In the present study, the effects of the membrane on the growth of keratinocytes and the activity of matrix metalloproteinases (MMPs), as well as on the healing of skin wounds in humans, were estimated. Fresh human foreskin was employed as the source of the keratinocyte culture, and a modified keratinocyte-SFM medium supplemented with 0.2 ng/mL of recombinant epidermal growth factor and 30 microg/mL bovine pituitary extract was used to enhance the successful growth of keratinocytes under an atmosphere of 5% CO2, at 37 degrees C. The results indicated that 0.01% SACCHACHITIN enhanced the proliferation of keratinocytes in the culture on the fourth and fifth days, and cells showed neither morphological alteration nor disordered proliferation. This evidence clearly indicated that SACCHACHITIN was not cytotoxic to and was safe for the growth of keratinocytes. Thus, SACCHACHITIN might play a positive role in the proliferation and differentiation of keratinocytes around wounds and in accelerated wound healing of epidermal tissue. In addition, microscopic observations during the growth of keratinocytes showed that normal proliferation and differentiation took place along the margin of the SACCHACHITIN membrane. This indicates that SACCHACHITIN is possibly cytocompatible with keratinocytes. Electrophoretic analysis and inhibition tests for the binding effect of SACCHACHITIN on MMPs showed that SACCHACHITIN reduced MMPs in extracellular matrix degradation and facilitated establishment of an extracellular matrix around wounds; these effects resulted in rapid wound healing. SACCHACHITIN was used as a skin dressing for patients who had skin chronicle ulcer, which had not healed for over 7 months. Preliminary clinical observations showed that the wound improved and began to heal. An analysis of MMPs by ELISA in tissue of the wound indicated a significant decrease in MMP levels.     

新型复合生物抗菌敷料的抗菌强度、吸湿能力及细胞毒性

背景：细菌感染是影响伤口愈合的主要因素之一,伤口渗出液里含有的大量炎症因子、蛋白酶和自由基都会减缓伤口的愈合速度。新型复合生物抗菌敷料的研发对治疗外科感染伤口有重要的意义,是创伤敷料发展的必然趋势。 目的：观察添加纳米银的海藻酸钙敷料的抗菌活性、吸湿能力及细胞毒性。 方法：将纳米银材料添加到海藻酸钙中制备新型复合生物抗菌敷料,并通过使用平板计数法、MTT法、电子显微镜观察法观察敷料的抗菌活性、吸湿能力及细胞毒性,再与银离子海藻酸钙敷料和海藻酸钙敷料进行对比,以期显示出新型复合生物抗菌敷料的具有强抗菌性及低细胞毒性的优势。 结果与结论：与银离子海藻酸钙敷料和海藻酸钙敷料相比,添加纳米银的新型复合生物抗菌敷料对金黄色葡萄球菌、铜绿假单胞菌均有更强的抑菌作用(P < 0.01),细胞毒性较低(P < 0.01);3种敷料的吸湿能力差异无显著性意义。证实此添加纳米银的海藻酸钙敷料的具有强抗菌性及低细胞毒性。      

The kinetics of thermal instability in nanocrystalline silver and the effect of heat treatment on the antibacterial activity of nanocrystalline silver dressings

The kinetics of nanocrystalline silver dressing heat treatment was investigated via isothermal heat treatments at 90 °C, 100 °C, and 110 °C lasting 2–50 h. Bactericidal efficacy of the dressings was measured via log reductions, while bacteriostatic longevity was determined via plate-to-plate transfer corrected zones of inhibition. Morphological evolution of the dressing was studied by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy, while changes in heat flow were measured by differential scanning calorimetry. Increasing temperature increased the rate at which dressing bactericidal activity and bacteriostatic longevity decreased. Once changes in dressing properties began, they occurred nonlinearly with time. The earliest biological, chemical, and physical indicators of altered dressing properties were loss of bacteriostatic longevity, silver–oxygen bonds, and fine features, respectively. An early change in heat flow appeared to be responsible for these indicators, while a later change corresponded to rapid grain growth occurring after a critical crystallite size (30 nm) was reached. The grain growth exponent was determined to be 2.8 for temperatures of 100–110 °C, with an activation energy of 177 kJ/mol, suggesting that normal grain growth occurred, with volume and/or grain boundary diffusion as the dominant forms of diffusion. The thermal instability of nanocrystalline silver should be accounted for during production, storage, and use of dressings. The properties required for nanosilver antimicrobial efficacy demonstrated in this study, as well as its thermal instability, should be taken into consideration for the development of nanosilver products in the future.     

Cytotoxicity testing of wound dressings using normal human keratinocytes in culture

Comparative cytotoxicity testing of 16 wound dressings of different composition show that normal human keratinocytes (NHK) growing on a fibroblastic feeder layer are as sensitive to toxic materials by direct contact as the confluent MRC5 fibroblasts used for standard cell culture cytotoxicity testing, and slightly more sensitive when extracts of the dressings were tested. After direct contact with each of the cell types, we found effects due to 12 dressing samples (75%), but the extracts of only 6 of them induced changes in cell shape or cell death on NHK, and 4 of them on MRC5 cells. In order to assess the compatibility of these dressings with a pure population of epidermal cells, the cell type responsible for reepidermization of healing wounds, we then tested the sensitivity, both to dressing samples and extracts, of normal human keratinocytes (NHK) grown in chemically defined medium and without a feeder layer: The results show epidermal cytocompatibility of 10 dressing extracts, while 6 others induced cytopathic effects. Three of these extracts specifically damaged epidermal cells and inhibited their proliferation. When comparing the sensitivities of NHK (in defined medium) and MRC5 cells, we observed complete correlation for 75% of the dressings by extract testing and in 94% of the cases after direct contact.     

Skin regeneration using keratinocytes and dermal fibroblasts cultured on biodegradable microspherical polymer scaffolds

Bioartificial skin sheet grafts have been utilized to treat large burns and chronic ulcers. However, the trypsinization step to harvest cultured skin grafts from culture dishes damages the cells by breaking the anchoring proteins and lowers their uptake ratio after transplantation. In addition, epidermal sheet grafts require a long fabrication period. To overcome these limitations, we utilized biodegradable poly(lactide-co-glycolide) (PLGA) microspheres as both cell culture matrix and transplantation vehicle of skin cells for skin regeneration in this study. This method could avoid the trypsinization step and have a relatively short preparation period. Human keratinocytes and dermal fibroblasts cultured on PLGA microspheres in spinner flasks proliferated by 3.0-fold and 9.4-fold, respectively, after 10 days. When both types of cells cultured on PLGA microspheres were reinoculated onto culture dishes, the cells migrated from the PLGA microspheres to the culture dish surface, grew, and formed a confluent cell layer within 5 days, showing the growth and migration abilities of the cells cultured on PLGA microspheres. Full-thickness skin wounds created on the back of athymic mice were either treated with transplantation of keratinocytes and dermal fibroblasts cultured on microspheres (cell-transplanted group), treated with PLGA microspheres alone (microsphere-implanted group), or covered with dressing materials without treatment (untreated group). Three weeks after the treatments, differentiated epithelium that stained positively for cytokeratin, a marker of epidermis, was observed in the cell-transplanted group, while the microsphere-implanted group and untreated group showed incomplete reepithelialization. Dermal regeneration with positive staining for vimentin, a marker of dermal fibroblast, was observed in the cell-transplanted group. Regenerated dermis with positive staining for vimentin was partly observed in the microsphere-implanted group and untreated group. These results suggest that transplantation of keratinocytes and dermal fibroblasts cultured on PLGA microspheres could be potentially useful as an alternative to bioartificial skin grafts for the treatment of skin wounds.     

Spontaneous skin erosions and reduced skin and corneal wound healing characterize CLIC4(NULL) mice

Cutaneous wound healing is a complex process involving blood clotting, inflammation, migration of keratinocytes, angiogenesis, and, ultimately, tissue remodeling and wound closure. Many of these processes involve transforming growth factor-β (TGF-β) signaling, and mice lacking components of the TGF-β signaling pathway are defective in wound healing. We show herein that CLIC4, an integral component of the TGF-β pathway, is highly up-regulated in skin wounds. We genetically deleted murine CLIC4 and generated a colony on a C57Bl/6 background. CLIC4(NULL) mice were viable and fertile but had smaller litters than did wild-type mice. After 6 months of age, up to 40% of null mice developed spontaneous skin erosions. Reepithelialization of induced full-thickness skin wounds and superficial corneal wounds was delayed in CLIC4(NULL) mice, resolution of inflammation was delayed, and expression of β4 integrin and p21 was reduced in lysates of constitutive and wounded CLIC4(NULL) skin. The induced level of phosphorylated Smad2 in response to TGF-β was reduced in cultured CLIC4(NULL) keratinocytes relative to in wild-type cells, and CLIC4(NULL) keratinocytes migrated slower than did wild-type keratinocytes and did not increase migration in response to TGF-β. CLIC4(NULL) keratinocytes were also less adherent on plates coated with matrix secreted by wild-type keratinocytes. These results indicate that CLIC4 participates in skin healing and corneal wound reepithelialization through enhancement of epithelial migration by a mechanism that may involve a compromised TGF-β pathway.     

Cultured epidermal keratinocytes on a microspherical transport system are feasible to reconstitute the epidermis in full-thickness wounds

Research efforts to modify cultured autologous skin transplants for large full-thickness burn wounds and in chronic ulcers have shifted from multilayered differentiated grafts ("sheet" grafts) toward smaller units of basal undifferentiated single cell suspensions in a transport medium and subconfluently covered static carriers. It has been shown that wounds transplanted with single cell suspensions reconstitute the epidermis. However, this technique requires the detachment of the keratinocytes from the culture flasks by enzymatic digestion-digestion that might alter the anchoring proteins of the cells. A new approach might be to circumvent the enzymatic digestion to harvest the keratinocytes. This study reports a technique to culture epidermal cells on spherical microcarriers as a suspension culture and transport vehicle. The spherical microcarrier consists of a 100-microm-diameter collagen-coated dextran carrier (Cytodex 3 Pharmacia) and has been used previously for enzyme production commercially. With this new approach, we seeded the human keratinocytes in a spinner-like system onto microspheres and transplanted these micrografts onto full-thickness wounds on the back of nude mice. After 14 days, we showed a reconstituted epithelium that was multilayered and keratinized compared to control wounds. We believe that this is the first step of a new approach to increase the cell yield for seeding without altering the anchoring proteins by enzymatic steps, leading to a superior transplantation method for keratinocytes.     

水凝胶联合藻酸盐银敷料在面部深Ⅱ度烧伤创面治疗中的应用研究

目的 探讨水凝胶联合藻酸盐银敷料在面部深Ⅱ度烧伤治疗中的应用效果.方法 选取2017年2月至2020年2月新疆维吾尔自治区人民医院烧伤创面修复科收治的82例面部深Ⅱ度烧伤患者,使用随机数字表法将患者分为干预组和对照组,每组各41例.2组患者均于治疗前根据临床操作规范去除创面失活组织,0.9％氯化钠溶液冲洗创面后使用无菌...     

Cultured human keratinocytes on type I collagen membranes to reconstitute the epidermis

The development of new techniques and modifications to overcome some of the disadvantages in cultured keratinocyte grafting has been motivated by several well-known drawbacks in the use of cultured epithelial autografts such as long culture periods, lack of adherence, difficulty in handling, lack of dermal substrates, and high costs. Two recent insights have influenced further research. On the one hand, it has been shown that the use of undifferentiated proliferative cells in fibrin glue suspensions is effective in epithelial reconstitution. On the other hand, the enzymatic release of cells from the culture surfaces is a critical step leading to at least temporary destruction of anchoring structures of the cultured cells. In this study, we tried to combine these two aspects in an attempt to modify common modalities of keratinocyte transplantation. To avoid dispase dissolving of the cultured cells, keratinocytes were seeded onto bovine collagen type I membranes without feeder layers and under serum-free culture conditions. Subconfluent monolayers of cultured human keratinocytes were transplanted as an upside-down graft on collagen membranes (keratinocyte collagen membrane grafts [KCMG], n = 12) after 3 days of culture or as membrane grafts alone (n = 12) onto standard nude mice full-thickness wounds. Fully differentiated epidermis was found at 21 days after grafting KCMG with persistence of human keratinocytes. This study demonstrates that upside-down grafts of undifferentiated monolayers of keratinocytes on non-cross-linked bovine type I collagen membranes do lead to an early reconstitution of multilayered squamous epithelium with enhanced wound healing compared to the control group. The upside down KCMG grafting technique is able to transfer actively proliferative keratinocytes and simplifies the application compared to conventional epithelial sheet grafting.     

Impact of heat on nanocrystalline silver dressings. Part II: Physical properties

This work explores the effects of elevated temperature on the physical and chemical properties of nanocrystalline silver, and relates it to previously observed thermally induced changes in biological activity [Taylor PL et al. Biomaterials, in press, doi:10.1016/j.biomaterials.2005.05.040]. Microstructural evolution of nanocrystalline silver dressings, heat-treated for 24 h at temperatures from 23 to 110 degrees C, was studied in detail using X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). These analyses indicated that silver nanocrystalline coatings undergo significant changes in structure when exposed to elevated temperature. XRD analysis showed a rapid increase in crystallite size above 75 degrees C along with decomposition of crystalline silver oxide (Ag2O) at the onset of crystallite growth. SEM imaging showed a loss of fine features and sintering of the structure at elevated temperatures. The XPS data indicated that silver-oxygen bonds disappeared completely, with the initial decomposition occurring between 23 and 37 degrees C, and total oxygen in the coating decreased from 16-17% to 6.5% over the temperature range of 75-110 degrees C. A comparison of these results to the data of Taylor et al. [Biomaterials, in press, doi:10.1016/j.biomaterials.2005.05.040] indicates that the unique biological properties of nanocrystalline silver are related to its nanostructure. This should guide future development of therapeutic nanocrystalline silver delivery systems.