Hydrogel-forming microneedle arrays exhibit antimicrobial properties: potential for enhanced patient safety.

We describe, for the first time, the microbial characterisation of hydrogel-forming polymeric microneedle arrays and the potential for passage of microorganisms into skin following microneedle penetration. Uniquely, we also present insights into the storage stability of these hydroscopic formulations, from physical and microbiological viewpoints, and examine clinical performance and safety in human volunteers. Experiments employing excised porcine skin and radiolabelled microorganisms showed that microorganisms can penetrate skin beyond the stratum corneum following microneedle puncture. Indeed, the numbers of microorganisms crossing the stratum corneum following microneedle puncture were greater than 105 cfu in each case. However, no microorganisms crossed the epidermal skin. When using a 21G hypodermic needle, more than 104 microorganisms penetrated into the viable tissue and 106 cfu of Candida albicans and Staphylococcus epidermidis completely crossed the epidermal skin in 24 h. The hydrogel-forming materials contained no microorganisms following de-moulding and exhibited no microbial growth during storage, while also maintaining their mechanical strength, apart from when stored at relative humidities of 86%. No microbial penetration through the swelling microneedles was detectable, while human volunteer studies confirmed that skin or systemic infection is highly unlikely when polymeric microneedles are used for transdermal drug delivery. Since no pharmacopoeial standards currently exist for microneedle-based products, the exact requirements for a proprietary product based on hydrogel-forming microneedles are at present unclear. However, we are currently working towards a comprehensive specification set for this microneedle system that may inform future developments in this regard.

Efficacy of topical PUVA soaks for palmoplantar dermatoses: an audit.

BACKGROUND: With a lack of evidence base for individual topical PUVA protocols, treatment is presently based on the consensus of current practice. This audit was designed to investigate the effectiveness of topical PUVA for palmoplantar dermatoses. METHODS: Phototherapy notes were reviewed on all patients who received hand and/or foot PUVA 2002-2007 in the Northern Health and Social Care Trust (NHSCT), Northern Ireland. RESULTS: Thirty patients met the inclusion criteria for the study. The mean number of treatments, maximum single UVA dose, and cumulative dose, were 18.4, 4.2 J/cm2, and 48.3 J/cm2, respectively. A positive response to treatment occurred in 51.3% of patients, which fell short of the 70% standard set. In a multivariate logistic regression analysis, number of treatments (P=0.04) and maximum single UVA dose (P=0.03) were the only variables associated with positive treatment outcome. The response was not influenced significantly by skin type, concurrent topical treatments, or cumulative UVA dose. Limitations to the study: Small patient numbers may have prevented the statistical significance of individual variables. CONCLUSIONS: UV dose increments should be clearly defined to avoid excess caution at the expense of an adequate patient response, and a minimum of 20 treatments administered to all patients, if tolerated.

Aminolaevulinic acid diffusion characteristics in 'in vitro' normal human skin and actinic keratosis: implications for topical photodynamic therapy.

BACKGROUND: The response rate of aminolaevulinic acid (ALA)-based photodynamic therapy (PDT) in certain subtypes of actinic keratosis (AK), such as hypertrophic and hyperkeratotic lesions, is variable, an effect attributable to a supposed lack of ALA penetration. A detailed and depth-related profile of spatial ALA permeation in AK following drug administration would lead to a greater understanding of concentrations achievable before protoporphyrin IX biosynthesis and subsequent PDT. METHODS: ALA penetration through excised normal human skin (NS) and AK lesions was evaluated using a cryostatic sectioning technique and radio-isotope counting following drug delivery using a novel, bioadhesive patch, loaded with 19, 38 or 50 mg/cm(2) ALA. RESULTS: Distinct differences in ALA concentration with respect to depth between AK and NS samples were shown, particularly within the superficial layers of the tissue structure, down to a depth of 1.0 mm. Patch application times were shown to influence ALA concentrations in tissue, but there was no clear correlation between ALA penetration in AK lesions taken from different body locations and from patients of different age. Similarly, the thickness of stratum corneum was not related to the ALA distribution profiles. CONCLUSIONS: Sizable variation in ALA concentration was a prominent feature of profiles through AK lesions, which may explain the variation of observed protoporphyrin IX production seen in the clinical implementation of AK PDT. That said, the results of this study show sufficient ALA penetration to a depth of 1.0 mm, which should be satisfactory for successful treatment of the majority of non-hyperkeratotic, hypertrophic AK using patch-based delivery methods.

Evaluating a walk-in clinic for detecting skin cancers.

AIM: To evaluate the effectiveness of a walk-in clinic in detecting skin cancers. METHOD: Questionnaires were completed by 283 patients attending the walk-in clinic at a dermatology outpatients department. The questionnaire was used to gather data on demographics, sun exposure, and personal and family history of skin cancers. Completion of the questionnaire was followed by an examination by a dermatologist. RESULTS: Three patients were diagnosed with malignant melanoma as a result of evaluation at the walk-in clinic. CONCLUSION: The walk-in clinic was an effective method of identifying patients with melanomas who might not have seen a GP. The authors believe that though effective at the screening, the clinic could be refined and improved.