Dual-Wavelength Sensor System for Fluorescence Detection of Bacillus subtilis Endospores

Biological threats to military and civilian sectors underscore the need for compact, cost-effective, and durable sensor systems capable of the sensitive and selective detection of bio-threat agents. Fluorescence-based techniques, particularly those employing UV light, have proven effective for detecting biological fluorophores such as proteins and cofactors. However, conventional laser-induced fluorescence (LIF) systems, while highly sensitive, are bulky, expensive, and require significant power and maintenance. To address these limitations, light-emitting diodes (LEDs) have emerged as a promising alternative, offering compact, robust, and low-maintenance solutions. Recent advancements in UV LEDs, spanning 200–400 nm, align with the excitation of natural fluorophores found in bacteria, spores, and viruses, enabling the development of practical fluorescence sensors. In this study, we developed a dual-wavelength fluorescence sensor system employing UV LEDs at 280 nm and 365 nm for the selective detection of Bacillus subtilis endospores, a surrogate for the pathogenic Bacillus anthracis. The system integrates optimized optical lenses and a bio-cell utilizing replaceable quartz sample tubes to minimize contamination and enhance usability. The sensor demonstrated selective detection at concentrations as low as 10⁷ spores/mL. This portable, cost-effective system provides a practical solution for rapid and reliable detection of biological threats, meeting critical field requirements for size, weight, and durability.