High-intensity narrow-spectrum (HINS) 405-nm light is a novel technology developed to address the significant problem of health-care associated infection. Its potential for wound-decontamination applications is assessed on mammalian cells and bacteria. The fibroblast-populated collagen lattice (FPCL) is used as an in vitro model of wound healing, and the effect of HINS light on contraction is examined. Effects on cell proliferation, morphological changes, and α-smooth muscle actin (α-SMA) expression are investigated. Bactericidal effects are assessed using the bacterium Staphylococcus epidermidis. Low doses of HINS light were found to have no significant inhibitory effects on FPCL contraction, cell proliferation, or α-SMA expression. Doses of up to 18 Jcm(-2) had no significant inhibitory effects on FPCL cell numbers, and this dose was shown to cause almost complete inactivation of bacteria. These results show that HINS light has potential for disinfection applications without adversely influencing wound healing.

Infection rates after arthroplasty surgery are between 1-4 %, rising significantly after revision procedures. To reduce the associated costs of treating these infections, and the patients' post-operative discomfort and trauma, a new preventative method is required. High intensity narrow spectrum (HINS) 405 nm light has bactericidal effects on a wide range of medically important bacteria, and it reduced bacterial bioburden when used as an environmental disinfection method in a Medical Burns Unit. To prove its safety for use for environmental disinfection in orthopaedic theatres during surgery, cultured osteoblasts were exposed to HINS-light of intensities up to 15 mW/cm 2 for 1 h (54 J/ cm 2 ). Intensities of up to 5 mW/cm 2 for 1 h had no effect on cell morphology, activity of alkaline phosphatase, synthesis of collagen or osteocalcin expression, demonstrating that under these conditions this dose is the maximum safe exposure for osteoblasts; after exposure to 15 mW/cm 2 all parameters of osteoblast function were significantly decreased. Viability (measured by protein content and Crystal Violet staining) of the osteoblasts was not influenced by exposure to 5 mW/cm 2 for at least 2 h. IntroductionHealthcare associated infections (HAI), defined as infections which are not present at the time the patient enters hospital, are an ever increasing problem in modern healthcare affecting approximately 1 in 10 patients admitted to UK hospitals (Reilly et al., 2007). Despite current attempts to resolve the problem, including campaigns to improve hygiene in hospitals, particularly hand washing, HAI still causes significant patient mortality. A report published by the House of Commons in 2004 found that HAIs are responsible for over 5,000 deaths in the UK each year, and are a contributory factor in over 1,500 deaths (National Audit Office, 2004). In the USA, deaths associated with HAI in hospitals exceeded the number attributable to several of the top ten leading causes of death. A survey performed in 2002 found 1.7 million patients with an HAI, of which 155,668 died (Klevens et al., 2007). The rise in prevalence of HAI can partly be attributed to the increased use of antibiotics leading to antibiotic resistant strains of many bacteria (McGowan, 1983). It is clear that novel approaches to bacterial inactivation are required.HAI take many forms. The most common type of infection reported by the Scottish National HAI Prevalence Survey was found to be urinary tract infection (UTI), accounting for 17.9 % of cases (Reilly et al., 2008), with a major risk factor being the use of indwelling catheters. Surgical site infections (SSI) are the next most common, accounting for 16 %. The use of indwelling or implanted medical devices is increasing with technological advances, and so the incidence of device-related infection is increasing (von Eiff et al., 2005). Taking infection acquired during hip replacement surgery as a specific example of HAI, studies have shown incidence rates from 1-5 %, increasing considerably after revi...

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