The rapid and reliable detection of cyanobacterial toxins remains a pressing challenge for environmental monitoring. In this work, we present a novel portable optical biosensor fabricated entirely from commercially available liquid crystal monomers and reagents. The device is based on a porous cholesteric liquid crystal network (CLCN) functionalized with anatoxin-specific aptamers, which transduces molecular binding events into visible colorimetric shifts observable by the naked eye. The fabrication process yields a robust photonic matrix that remains stable under hot and humid conditions, ensuring suitability for on-site analysis in diverse environments. This work marked the first use of a porous CLCN in an aptameric biosensor, introducing a novel approach to optical sensing. The biosensor demonstrates a low nanomolar detection limit (4.75 nM), strong selectivity against co-occurring cyanotoxins, and reliable performance in realwater matrices with recoveries within 85−110%. Importantly, the clear, color-based output eliminates the need for bulky instrumentation, making the system highly adaptable for field deployment. This study highlights the potential of chip-based photonic biosensors as practical, cost-effective, and globally accessible tools for water quality monitoring.