Biological threats to military and civilian sectors underscore the need for compact, cost-eff ective, 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 eff ective for detecting biological fl uorophores such as proteins and cofactors. However,

conventional laser-induced fl uorescence (LIF) systems, while highly sensitive, are bulky, expensive, and require signifi cant

power and maintenance. To address these limitations, light-emitting diodes (LEDs) have emerged as a promising alternative,

off ering compact, robust, and low-maintenance solutions. Recent advancements in UV LEDs, spanning 200–400 nm, align

with the excitation of natural fl uorophores found in bacteria, spores, and viruses, enabling the development of practical

fl uorescence sensors. In this study, we developed a dual-wavelength fl uorescence 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 10 7 spores/

mL. This portable, cost-eff ective system provides a practical solution for rapid and reliable detection of biological threats,

meeting critical fi eld requirements for size, weight, and durability.