Traditionally, light for phototherapy and photodynamic therapy has been administered in a clinical environment using lasers or bulky lamp systems; however light-emitting diodes (LEDs) for phototherapy and photodynamic therapy are gaining in popularity due to their high efficiencies, low-cost designs, and design versatility. In addition, LEDs can be assembled into flexible bandages to be worn on the patient’s skin to replace traditional lamp systems and increase patient comfort. However, because this brings the LEDs closer to the skin, light intensity hot spots form which is not desirable for phototherapy where uniform irradiance is required to inactivate target cells most effectively. We present an optical simulation of a blue LED array to evaluate the effects of immersion media of varying thickness on the uniformity of light distribution for near-field illumination in phototherapeutic applications. We have compared different immersion materials (air, water, and optical-grade silicone) placed in between the LED array and the skin with the goal of uniform irradiance distribution and optimized lighting efficiency. The irradiance incident on the tissue over an area of 60 cm2 was simulated and compared for the three materials. Both silicone and water showed an increase in uniformity over an area of 14.4 cm2 as the thickness increased without a significant decrease in irradiance at the tissue. These results show promise for future flexible photonic devices where a high degree of uniformity is required in situations where the device needs to be placed on or near the skin.
Surgical site infections (SSIs) are a leading cause of morbidity and mortality and a significant expense to the healthcare system and hospitals. The majority of these infections are preventable; however, increasing bacterial resistance, biofilm persistence, and human error contribute to the occurrence of these healthcare-associated infections. We present a flexible antimicrobial blue-light emitting bandage designed for use on postoperative incisions and wounds. The photonic device is designed to inactivate bacteria present on the skin and prevent bacterial colonization of the site, thus reducing the occurrence of SSIs. This antimicrobial light emitting bandage uses blue light’s proven abilities to inactivate a wide range of clinical pathogens regardless of their resistance to antibiotics, inactivate bacteria without harming mammalian cells, improve wound healing, and inactivate bacteria in biofilms. The antimicrobial bandage consists of a thin 2”x2” silicone sheet with an array of 77 LEDs embedded in multiple layers of the material for thermal management. The 405 nm center wavelength LED array is designed to be a wearable device that integrates with standard hospital infection prevention protocols. The device was characterized for irradiance of 44.5 mW/cm2. Methicillin-resistant Staphylococcus aureus seeded in a petri dish was used to evaluate bacterial inactivation in vitro. Starting with a concentration of 2.16 x 107 colony forming units (CFU)/mL, 45% of the bacteria was inactivated within 15 minutes, 65% had been inactivated by 30 minutes, 99% was inactivated by 60 minutes, and a 7 log reduction and complete sterilization was achieved within 120 minutes.
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