Performance and Energy Efficiency of Low Irradiance Antimicrobial Blue Light for Continuous Decontamination Applications

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The emergence of multi-drug resistant microbes presents both a major risk to public health and an economic burden on the global healthcare system. Antimicrobial 405nm blue HINS-light is a unique method of infection control that has been proven to inactivate a broad range of microbial species including those with antibiotic resistance. Due to its unique safety features, it has been developed for use as a passive decontamination technology which permits continuous disinfection of occupied environments. This project aims to generate important new information on this emerging infection control technology by investigating aspects of its fundamental photo-chemical inactivation mechanism, specifically with respect to its operation using low irradiance photon energy. Unlike ultraviolet light, which possesses well-known germicidal action, the recognition of the antimicrobial properties of 405nm light is a relatively recent scientific discovery. Much of the literature in the area has focused on proving the antimicrobial principles, and to do this, studies have tended to utilise high power light sources (up to 150mW/cm2) in order to achieve faster antimicrobial effects. This however, has limitations when translating the findings towards practical applications which are designed to use low irradiance levels. This is particularly significant for the application of the technology for continuous environmental decontamination, as these systems typically utilise irradiance levels of <0.5mW/cm2 in order to permit safe, 24/7, exposure of room occupants.Recent data generated by the ROLEST group has highlighted that use of low irradiance photon levels results in major differences in the microbial inactivation kinetics when compared with high intensity photon levels. Low irradiance illumination of samples demonstrated enhanced antimicrobial efficacy and significantly improved energy efficiency. With the growing industry demand for energy efficiency in lighting systems, the ability to understand this fundamental concept and utilise the knowledge to develop low power, energy efficient antimicrobial lighting systems, will be of significant research and commercial interest. The project aims and objectives will include the following: -An in-depth scientific and technical literature review to establish current knowledge on the fundamental action and application of antimicrobial blue light, including a review of the irradiance levels and energy efficiencies reported in these studies.-Design and build of a bench-top, low irradiance light system which will be used for antimicrobial and energy efficiency testing. Significant technical development will be required for this in order to ensure the use of appropriate LED sources and optical components; cooling/thermal management; controllability of output irradiance; and operator safety. Irradiance profiling of the built system will be conducted to optimise LED configurations and ensure uniformity of the low irradiance light distribution.-Antimicrobial testing will be conducted to evaluate a panel of key organisms for their susceptibility to low irradiance light. Inactivation kinetics for a range of irradiance levels and doses will be established. Key organisms to be tested will include ESKAPE pathogens and viruses. Decontamination efficacy will be evaluated on a range of relevant surfaces common within clinical and industrial environments (e.g. metals, polymers, fabrics, glass). - A key factor to be established will be the minimum threshold level for antimicrobial efficacy. Knowledge of the minimum irradiance levels and exposure times required for successful decontamination will be a key factor in the development of low energy systems for practical infection control applications. -Comparisons will also be made to the energies required for microbial inactivation using high irradiance light in order to quantify improvements in energy and germicidal efficiency.