Electrospun multifunctional nanofibrous mats loaded with bioactive anemoside B4 for accelerated wound healing in diabetic mice

With the worldwide prevalence of diabetes and considering the complicated microenvironment of diabetic wounds, the design and development of innovative multifunctional wound dressing materials are much wanted for the treatment of hard-to-heal wounds in diabetic patients. In the present study, anti-inflammatory ingredients loaded with nanofibrous wound dressing materials were manufactured by a promising blend-electrospinning strategy, and their capability for treating the diabetic wound was also systematically explored. A polymer blend consisting of Chitosan (CS) and polyvinyl alcohol (PVA) was electrospun into CS-PVA nanofibrous mats as control groups. In the meanwhile, a bioactive ingredient of Chinese medicine Pulsatilla, anemoside B4(ANE), with different contents were loaded into the electrospinning solution to construct CS-PVA-ANE nanofibrous mats. The developed CS-PVA-ANE wound dressing materials exhibited multifunctional properties including prominent water absorption, biomimetic elastic mechanical properties, and sustained ANE releasing behavior, as well as outstanding hemostatic properties. The in vitro studies showed that the CS-PVA-ANE nanofiber mats could significantly suppress lipopolysaccharide (LPS)-stimulated differentiation of pro-inflammatory (M1) macrophage subsets, and notably reduce the reactive oxygen species (ROS) generation, as well as obviously decrease inflammatory cytokine release. The in vivo animal studies showed that the CS-PVA-ANE nanofiber mats promoted the healing of diabetic wounds by significantly enhancing wound closure rates, accelerating excellent angiogenesis, promoting re-epithelization and collagen matrix deposition throughout all stages of wound healing. The present study demonstrated that CS-PVA-ANE nanofiber mats could effectively shorten the wound-healing time by inhibiting inflammatory activity, which makes them promising candidates for the treatment of hard-to-heal wounds caused by diabetes.     

Thermosensitive Hydrogel as a Tgf-β1 Gene Delivery Vehicle Enhances Diabetic Wound Healing

PURPOSE: To accelerate diabetic wound healing with TGF-beta1 gene delivery system using a thermosensitive hydrogel made of a triblock copolymer, PEG-PLGA-PEG. METHODS: Two 7 x 7 mm full thickness excisional wounds were created in parallel at the back of each genetically diabetic mouse. The hydrogel containing plasmid TGF-beta1 was administered to the wound and formed an adhesive film in situ. Controls were either untreated or treated with the hydrogel without DNA. We used a commercial wound dressing, Humatrix, either with or without DNA, to compare the therapeutic effect with the thermosensitive hydrogel. RESULTS: We found that thermosensitive hydrogel alone is slightly beneficial for reepithealization at early stage of healing (day 1-5), but significantly accelerated repithelializaion, increased cell proliferation, and organized collagen were observed in the wound bed treated with thermosensitive hydrogel containing plasmid TGF-beta1. The accelerated reepithelialization was accompanied with enhanced collagen synthesis and more organized extracellular matrix deposition. Humatrix alone or with plasmid TGF-beta1, had little effect. CONCLUSIONS: Thermosensitive hydrogel made of PEG-PLGA-PEG triblock copolymer provides excellent wound dressing activity and delivers plasmid TGF-beta1 to promote wound healing in a diabetic mouse model.     

Local anesthetic lidocaine-encapsulated polymyxin–chitosan nanoparticles delivery for wound healing: in vitro and in vivo tissue regeneration

In relieving local pains, lidocaine, one of ester-type local anesthetics, has been used. To develop the lidocaine membranes of enhanced local anesthetic effects, we have designed to establish the composition of wound dressings based on lidocaine chloride (LCH) (anesthetic drug)-loaded chitosan (CS)/polymyxin B sulfate (PMB). The LCH membranes (LCH-CS/PMB) was fabricated by the LCH oxide solutions within the CS/PMB matrix. The influences of different experimental limitations on CS/PMB membrane formations were examined. The double membrane particle sizes were evaluated by scanning electron microscopy (HR-SEM). Additionally, antibacterial efficacy was developed for gram-positive and negative microorganisms. Moreover, we examined in vivo healing of skin wounds formed in mouse models over 16 days. In contrast to the untreated wounds, rapid healing was perceived in the LCH-CS/PMB-treated wound with less damaging. These findings indicate that LCH-CS/PMB-based bandaging materials could be a potential innovative biomaterial for tissue repair and regeneration for wound healing applications in an animal model.     

封闭负压引流技术联合人工真皮修复慢性创面的临床研究

目的 观察封闭负压引流技术（VSD）联合人工真皮修复慢性创面的临床疗效.方法 66例慢性创面患者随机分成两组.对照组33例：予抗感染,改善微循环,聚维酮纱外敷,经换药治疗创面未愈者行植皮或皮瓣修复术.观察组33例：予抗感染,改善微循环,早期应用VSD处理创面,创面有新鲜肉芽组织后植入人工真皮（皮耐克）,待其肉芽生长满意后行植皮术.结果 对照组平均住院天数（55.3±1.2）天,其中植皮或皮瓣修复术修复30例,创面换药愈合者3例,创面愈合后疤痕增生明显.观察组平均住院天数（31.6±1.2）天,其中20例患者创面较大,经外敷人工真皮,肉芽生长满意后予植皮手术,其余患者经植入人工真皮换药,创面治愈后外观满意,疤痕增生轻或不明显.结论 VSD联合人工真皮修复慢性创面可以有效的促进慢性创面愈合,减少疤痕增生,缩短住院时间.     

Hybrid thermosensitive-mucoadhesive in situ forming gels for enhanced corneal wound healing effect of L-carnosine

PurposeThermosensitive in situ gels have been around for decades but only a few have been translated into ophthalmic pharmaceuticals. The aim of this study was to combine the thermo-gelling polymer poloxamer 407 and mucoadhesive polymers chitosan (CS) and methyl cellulose (MC) for developing effective and long-acting ophthalmic delivery systems for L-carnosine (a natural dipeptide drug) for corneal wound healing.MethodsThe effect of different polymer combinations on parameters like gelation time and temperature, rheological properties, texture, spreading coefficients, mucoadhesion, conjunctival irritation potential, in vitro release, and ex vivo permeation were studied. Healing of corneal epithelium ulcers was investigated in a rabbit’s eye model.ResultsBoth gelation time and temperature were significantly dependent on the concentrations of poloxamer 407 and additive polymers (chitosan and methyl cellulose), where it ranged from <10 s to several minutes. Mechanical properties investigated through texture analysis (hardness, adhesiveness, and cohesiveness) were dependent on composition. Promising spreading-ability, mucoadhesion, transcorneal permeation of L-carnosine, high ocular tolerability, and enhanced corneal epithelium wound healing were recorded for poloxamer 407/chitosan systems.ConclusionIn situ gelling systems comprising combinations of poloxamer-chitosan exhibited superior gelation time and temperature, mucoadhesion, and rheological characteristics suitable for effective long-acting drug delivery systems for corneal wounds.     

VSD治疗神经缺血性糖尿病足溃疡的效果探讨

目的探讨封闭负压引流(VSD)治疗神经缺血性糖尿病足溃疡的临床效果。方法 60例(60肢)神经缺血性糖尿病足溃疡患者,随机分为VSD技术治疗组和湿性换药治疗组,各30例(30肢)。湿性换药治疗组患者接受湿性换药治疗, VSD技术治疗组患者接受VSD技术治疗。统计比较两组患者的肉芽组织生长活跃时间、创面床准备完成时间、伤口愈合情况、感染发生情况。结果 VSD技术治疗组患者肉芽组织生长活跃时间(7.6±1.8)d、创面床准备完成时间(15.4±2.8)d均显著短于湿性换药治疗组的(15.3±2.8)、(29.3±5.3)d,差异有统计学意义(P<0.05)。VSD技术治疗组患者伤口总愈合率96.7%(29/30)显著高于湿性换药治疗组的56.7%(17/30),差异有统计学意义(P<0.05)。VSD技术治疗组患者感染发生率3.3%(1/30)显著低于湿性换药治疗组的26.7%(8/30),差异有统计学意义(P<0.05)。结论 VSD治疗神经缺血性糖尿病足溃疡的效果显著,可有效缩短肉芽组织生长活跃时间,降低感染情况发生,值得推广。     

人工真皮修复慢性创面疗效观察

目的 探索慢性创面治疗方法.方法 回顾性分析我院2008年至2011年62例慢性创面患者的治疗方法.将其随机分成两组:对照组32例,予抗感染,改善微循环,聚维酮纱外敷,经换药治疗创面未愈者行植皮或皮瓣修复术;观察组30例,予抗感染,改善微循环,早期清创,感染控制后外敷人工真皮(皮耐克),诱导真皮重建,促进肉芽组织生长和创面愈合,创面较大者待其肉芽生长满意后行植皮术.结果 对照组平均住院天数( 58.2±1.3)d,其中植皮或皮瓣修复术修复18例,创面换药愈合者14例,创面愈合后疤痕增生明显.观察组平均住院天数( 31.4±1.1)d,其中7例患者创面较大,经外敷人工真皮,肉芽生长满意后予植皮手术,其余患者经外敷人工真皮、换药,创面治愈后外观满意,疤痕增生轻或不明显.结论 应用人工真皮可促进慢性创面愈合,减少疤痕增生,有效缩短住院天数,降低手术率和手术风险,值得借鉴、推广.     

应用负压封闭引流综合治疗慢性难愈性创面的临床体会

目的 探讨应用负压封闭引流(VSD)综合治疗慢性难愈性创面的临床疗效,为临床应用、推广提供治疗依据.方法 选择40例慢性难愈性创面患者,其中20例行VSD序贯治疗,包括全身综合治疗、创面清创、常规换药、VSD治疗和手术治疗来修复难愈性创面(观察组),20例采用除去VSD治疗的传统治疗(对照组),对两组创面换药次数、创面愈合情况、手术成功率进行比较.结果 40例患者中观察组创面换药次数明显少于对照组[(13.55±6.87)次比(29.25±24.13)次,t=2.319,P<0.05];10例非手术患者中观察组可促进创面愈合,治愈率明显高于对照组(100％比40％,P<0.05);30例手术患者中观察组手术修复成功率明显高于对照组(100％比60％,P<0.05).结论 VSD对于难愈性创面,尤其窦道性创面及肌腱甚至骨质外露创面均有显著效果,值得推广应用.     

Delivery of Therapeutics from Layer-by-Layer Electrospun Nanofiber Matrix for Wound Healing: An Update

Increasing incidences of chronic wounds urge the development of effective therapeutic wound treatment. As the conventional wound dressings are found not to comply with all the requirements of an ideal wound dressing, the development of alternative and effective dressings is demanded. Over the past few years, electrospun nanofiber has been recognized as a better system for wound dressing and hence has been studied extensively. Most of the electrospun nanofiber dressings were fabricated as single-layer structure mats. However, this design is less favorable for the effective healing of wounds mainly due to its burst release effect. To address this problem and to simulate the organized skin layer's structure and function, a multilayer structure of wound dressing had been proposed. This design enables a sustained release of the therapeutic agent(s), and more resembles the natural skin extracellular matrix. Multilayer structure is also referred to layer-by-layer (LbL), which has been established as an innovative method of drug incorporation and delivery, combines a high surface area of electrospun nanofibers with the multilayer structure mat. This review focuses on LbL multilayer electrospun nanofiber as a superior strategy in designing an optimal wound dressing.     

加温涡流式冲洗结合VSD在慢性伤口中的应用研究

目的 研究加温涡流式冲洗结合VSD在慢性伤口中的应用价值.方法 将30例慢性创面患者随机分为观察组和对照组,各15例.实验组伤口清创后接受加温涡流式冲洗和VSD,对照组常规处理.比较两组伤口清洁时间、愈合率、疗效、换药次数、住院天数及治疗费用.结果 观察组伤口清洁时间、愈合率和疗效、换药次数、住院天数及治疗费用明显优于对照组(P＜0.05).结论 加温涡流式冲洗结合VSD治疗慢性创面的疗效明显优于常规治疗.     

In situ injectable nano-composite hydrogel composed of curcumin, N,O-carboxymethyl chitosan and oxidized alginate for wound healing application

In this paper, an in situ injectable nano-composite hydrogel composed of curcumin, N,O-carboxymethyl chitosan and oxidized alginate as a novel wound dressing was successfully developed for the dermal wound repair application. Nano-curcumin with improved stability and similar antioxidant efficiency compared with that of unmodified curcumin was developed by using methoxy poly(ethylene glycol)-b-poly(?-caprolactone) copolymer (MPEG-PCL) as carrier followed by incorporating into the N,O-carboxymethyl chitosan/oxidized alginate hydrogel (CCS-OA hydrogel). In vitro release study revealed that the encapsulated nano-curcumin was slowly released from CCS-OA hydrogel with the diffusion-controllable manner at initial phase followed by the corrosion manner of hydrogel at terminal phase. In vivo wound healing study was performed by injecting hydrogels on rat dorsal wounds. Histological study revealed that application of nano-curcumin/CCS-OA hydrogel could significantly enhance the re-epithelialization of epidermis and collagen deposition in the wound tissue. DNA, protein and hydroxyproline content in wound tissue from each group were measured on 7th day of post wounding and the results also indicated that combined using nano-curcumin and CCS-OA hydrogel could significantly accelerate the process of wound healing. Therefore, all these results suggested that the developed nano-curcumin/CCS-OA hydrogel as a promising wound dressing might have potential application in the wound healing.     

Management of acute and chronic open wounds: the importance of moist environment in optimal wound healing

The history of wound care and management closely parallels that of military surgery which has laid down the principles and dictated the practices of wound cleansing, debridement and coverage. From a treatment standpoint, there are essentially two types of wounds: those characterized by loss of tissue and those in which no tissue has been lost. In the event of tissue loss it is critical to determine whether vital structures such as bone, tendons, nerves and vessels have been exposed. It is also important to determine the amount of soft tissue contusion and contamination. In any case primary wound healing by early closure either primarily or with the help of grafts or flaps is preferred to secondary healing and wound contraction with subsequent contractures which interfere with range of motion and function. Whether the wound is acute or chronic, essential principles of wound care must be observed in order to avoid wound sepsis and achieve rapid and optimal wound healing. - Tissues must be handled gently. - Caustic solutions capable of sterilizing the skin should never be applied to the wound. It is desirable never to put anything in the wound that cannot be tolerated comfortably in the conjunctival sac. - All devitalized tissues must be debrided either hydrodynamically, chemically, mechanically or surgically. - All dead space must be obliterated. - Exposed vital structures must be covered by well vascularized tissues. An essential part of any wound management protocol is wound dressing. It cannot be too strongly emphasized that a wound dressing may have a profound influence on healing particularly of secondary type healing, a critical feature being the extent to which such dressing restricts the evaporation of water from the wound surface. A review of available dressing materials is reported with emphasis on the newly developed concept of moist environment for optimal healing. a practical guide for dressing selection is also proposed.     

Drug-Loaded Polymeric Composite Skin Graft for Infection-Free Wound Healing: Fabrication, Characterization, Cell Proliferation, Migration, and Antimicrobial Activity

Purpose

A new, injectable, drug-loaded composite graft was developed to enable infection free wound healing.

Methods

The graft was fabricated using gentamicin and biomimetic microparticulate scaffolds in gelatin gel and characterized for biologically relevant properties like fluid uptake, evaporative water loss (EWL), water vapor transmission rate (WVTR), Young’s modulus and degradation. It was evaluated for drug release, cytocompatibility and antimicrobial efficacy against Staphylococcus aureus and Pseudomonas aeruginosa.

Results

Graft exhibited fluid uptake of 13.79%, EWL of 60–70% in 10?h, WVTR of 5480.31?g/m²/d, and Young’s modulus as 2.1–10.8?kPa. It exhibited 99.36% degree of crosslinking and a dual degradation behavior wherein, the carrier gel, gelatin, degraded rapidly leaving the microparticulate scaffolds intact. Drug release studies showed a sustained release of gentamicin for 13?days sufficient to inhibit the infection at the wound site. Cytocompatibility assessment of the graft revealed that graft supported cell adhesion, proliferation and migration. The antibacterial efficacy of the graft was assessed using Kirby-Bauer method and time kill assay, wherein results indicated a quick, effective (≥5-log reduction in CFU/ml) and long lasting antimicrobial effect.

Conclusions

These results as a whole indicate that the graft represents an effective alternative for infection-free healing of full thickness wounds.

An innovative bi-layered wound dressing made of silk and gelatin for accelerated wound healing

In this study, the novel silk fibroin-based bi-layered wound dressing was developed. Wax-coated silk fibroin woven fabric was introduced as a non-adhesive layer while the sponge made of sericin and glutaraldehyde-crosslinked silk fibroin/gelatin was fabricated as a bioactive layer. Wax-coated silk fibroin fabrics showed improved mechanical properties compared with the non-coated fabrics, but less adhesive than the commercial wound dressing mesh. This confirmed by results of peel test on both the partial- and full-thickness wounds. The sericin-silk fibroin/gelatin spongy bioactive layers showed homogeneous porous structure and controllable biodegradation depending on the degree of crosslinking. The bi-layered wound dressings supported the attachment and proliferation of L929 mouse fibroblasts, particularly for the silk fibroin/gelatin ratio of 20/80 and 0.02% GA crosslinked. Furthermore, we proved that the bi-layered wound dressings promoted wound healing in full-thickness wounds, comparing with the clinically used wound dressing. The wounds treated with the bi-layered wound dressings showed the greater extent of wound size reduction, epithelialization, and collagen formation. The superior properties of the silk fibroin-based bi-layered wound dressings compared with those of the clinically used wound dressings were less adhesive and had improved biological functions to promote cell activities and wound healing. This novel bi-layered wound dressing should be a good candidate for the healing of full-thickness wounds.     

胰岛素联合纳米银和湿润烧伤膏治疗中度烧伤创面感染的临床研究

目的探讨胰岛素注射液联合纳米银抗菌凝胶和湿润烧伤膏治疗中度烧伤创面感染的临床疗效。方法选取2013年1月—2015年1月黄石市第五医院收治的中度烧伤创面感染患者66例(75个创面)作为研究对象,随机分为对照组(33例39个创面)和治疗组(33例36个创面)。对照组将纳米银抗菌凝胶和湿润烧伤膏按照1∶1比例混合,均匀涂抹于烧伤创面,厚度1 mm,无菌纱布加压包扎。治疗组在对照组基础上烧伤创面皮下浸润注射胰岛素注射液1 U/m L,无菌纱布加压包扎。记录两组患者创面愈合时间、创面细菌培养转阴换药次数,计算两组创面愈合率。治疗前、治疗第7、14、21天发放视觉模拟评分(VAS)评估患者换药疼痛程度。治疗前和治疗7 d测定白介素-6(IL-6)、白介素8(IL-8)、肿瘤坏死因子α(TNF-α)水平。结果治疗组创面浅Ⅱ度和深Ⅱ度创面愈合时间短于对照组,创面细菌培养转阴换药次数少于对照组,两组比较差异具有统计学意义(P0.05)。治疗组浅Ⅱ度第7、14天创面愈合率高于对照组,深Ⅱ度第14、21天创面愈合率高于对照组,两组比较差异具有统计学意义(P0.05)。两组治疗第7、14、21天VAS评分均下降,同组治疗前后差异具有统计学意义(P0.05);治疗组治疗第7、14、21天VAS评分明显低于对照组,两组比较差异具有统计学意义(P0.05)。治治疗7 d后,两组TNF-α、IL-6、IL-8水平均显著升高,同组治疗前后差异有统计学意义(P0.05);且治疗组治疗7 d后这些观察指标的升高程度明显低于对照组,两组比较差异具有统计学意义(P0.05)。结论局部注射胰岛素注射液联合纳米银抗菌凝胶和湿润烧伤膏治疗中度烧伤创面感染,能减轻创面炎性水平,缩短创面感染病程,提高创面愈合率,具有一定的临床推广应用价值。     

Bilayer hydrogel dressing with lysozyme-enhanced photothermal therapy for biofilm eradication and accelerated chronic wound repair

Biofilms are closely associated with the tough healing and dysfunctional inflammation of chronic wounds. Photothermal therapy (PTT) emerged as a suitable alternative which could destroy the structure of biofilms with local physical heat. However, the efficacy of PTT is limited because the excessive hyperthermia could damage surrounding tissues. Besides, the difficult reserve and delivery of photothermal agents makes PTT hard to eradicate biofilms as expectation. Herein, we present a GelMA-EGF/Gelatin-MPDA-LZM bilayer hydrogel dressing to perform lysozyme-enhanced PTT for biofilms eradication and a further acceleration to the repair of chronic wounds. Gelatin was used as inner layer hydrogel to reserve lysozyme (LZM) loaded mesoporous polydopamine (MPDA) (MPDA-LZM) nanoparticles, which could rapidly liquefy while temperature rising so as to achieve a bulk release of nanoparticles. MPDA-LZM nanoparticles serve as photothermal agents with antibacterial capability, could deeply penetrate and destroy biofilms. In addition, the outer layer hydrogel consisted of gelatin methacryloyl (GelMA) and epidermal growth factor (EGF) promoted wound healing and tissue regeneration. It displayed remarkable efficacy on alleviating infection and accelerating wound healing in vivo. Overall, the innovative therapeutic strategy we came up with has significant effect on biofilms eradication and shows promising application in promoting the repair of clinical chronic wounds.     

Efficacy and tolerance of a hydrocolloid dressing containing hyaluronic acid for the treatment of leg ulcers of venous or mixed origin

ABSTRACT

Objective: This study was aimed at comparing efficacy and tolerance of a new hydrocolloid dressing containing hyaluronic acid (HC?+?HA) to a reference hydrocolloid not containing hyaluronic acid (HC) in the treatment of leg ulcers of venous or mixed origin.

Research design and methods: This was an open, prospective study, randomized in parallel groups, in which 125 patients were enrolled and treated for up to 42 days. The primary efficacy criterion was the reduction of the wound area; other efficacy criteria were the condition of the wound bed, and of the surrounding skin, and presence and severity of symptoms such as pain and itching.

Results: After 42 days of treatment the median reduction of ulcer area was ?42.6% (95% confidence interval [CI]: ?66.6; ?5.7) and ?31.0% (95% CI: ?51.6; ?8.8) in the HC?+?HA group and in the reference HC group, respectively. The difference between treatments was not statistically significant. A reduction ≥?90% of the initial ulcer area was seen in 15 patients in the HC?+?HA dressing group and in only seven patients in the HC dressing group. Changes in wound bed condition in the two groups were not significantly different, except for a more marked reduction of fibrinous tissue in the HC?+?HA dressing group (?p?=?0.04), at Day 28. Both treatments were well tolerated.

Conclusions: The HC?+?HA dressing was equally well tolerated and with a trend to be more effective than the reference HC dressing in the treatment of leg ulcers of venous or mixed origin. Further research is needed to confirm these findings.     

四肢闭合骨折内固定术后伤口深部感染的治疗

目的探讨四肢闭合骨折内固定术后伤口深部感染的治疗效果。方法回顾18例四肢闭合骨折术后伤口深部感染患者的治疗经过。全身营养支持及合理抗生素治疗下,9例采取伤口清创换药,9例采取伤口对口置管冲洗引流,分析四肢闭合骨折术后伤口深部感染的疗效。结果患者感染伤口均获延期愈合,时间21～60d,平均27d。对口置管冲洗引流组的伤口愈合时间明显短于清创换药组。结论四肢闭合骨折术后伤口深部感染的综合治疗效果良好。在基础治疗前提下,伤口清创换药或对口置管冲洗引流各有优势。     

负压引流术治疗深度难治性创面疗效观察

【摘要】目的探讨负压引流术（VSD）在深度难治性创面修复中的应用效果。方法对本院2010年7月-2011年10月收治的19例深度组织缺损患者实施负压引流术治疗,观察患者的临床治疗效果。结果19例患者使用VSD次数为l～6次,平均2．2次;治疗时间2～7周,平均3周;患者创面修复情况均完全修复;无患者发生死亡及严重并发症。经过2个月随访,19例患者创面外观及功能均恢复良好。11例（57．89％）患者创面使用VSD后,创面与创腔显著缩小,经换药治疗后愈合良好;5例（26．32％）患者创面使用VSD后,肉芽组织生长良好,进行游离植皮,创面愈合良好;3例（15．79％）患者创面使用VSD后,创腔闭合良好,进行皮瓣移植,创面愈合良好。结论负压引流术可以有效清除局部渗出物与创面的坏死组织,显著改善血液循环,加速创面的愈合,对深度难治性创面治疗效果良好。具有重要的临床应用价值。     

An in vitro method for the quantitative determination of the antimicrobial efficacy of silver-containing wound dressings

Treatment with silver-containing wound dressings is becoming an increasingly popular strategy to eliminate growth of opportunistic wound pathogens during the healing process. However, there are concerns over the possible side-effects of silver to the patient; coupled to the cost of silver as an ingredient there is a desire to ensure that wound dressings contain the least quantity of active ingredient to ensure the minimum bactericidal concentration (MBC) of silver is maintained in the wound environment. This requires the ability to determine the efficacy of silver directly within the wound environment; an extremely complicated task that is difficult using classical (plate counting) microbiological assays because these cannot be conducted in situ. Here, we report a quantitative method for determining the efficacy of silver in wound dressings using an isothermal calorimetric method. The growth curves of P. aeruginosa (NCIMB 8628) were recorded in growth medium and in growth medium containing AQUACEL Ag Hydrofiber dressing. It was found that 10 mg of dressing was sufficient to ensure no detectable growth of organism in 2.5 mL of medium inoculated to 10(6) cfu/mL. This corresponded to a silver load of 1.1x10(-6) moles (equivalent to 4.4x10(-4) M, in the volume of medium used in the experiment). Experiments conducted with silver nitrate rather than dressing indicated the MBC of silver against P. aeruginosa was 1x10(-4) M. The results suggested that not all of the silver in the dressing was bioavailable, at least over the lifetime of the experiment. One advantage of this effect would be the lack of excess availability of the silver, which allays fears of potential toxicity to the patient and may provide an extended period of time over which the dressing is bactericidal.