A chitosan leaky waveguide biosensor for measurement of DNA biomarkers

Sustainable polymers such as chitosan are gaining popularity for diverse applications including sensing. Electrochemical sensors with chitosan-nanocomposite electrodes have been reported, but the use of undoped chitosan can reduce the cost of sensors. Chitosan films deposited on glass substrates can serve as optical label-free leaky waveguide (LW) sensors, providing high sensitivity at low cost compared to other optical sensors. Here, for the first time, we report chitosan LW biosensors for sequence-specific quantification of ∼7.9 kDa target DNA. The target DNA sequence selected in this work is strongly associated with low-grade, non-muscle-invasive bladder cancer. The chitosan LW biosensor offered a limit of detection (LOD) of 1.4 nM for the target DNA in buffer without amplification and an analysis time of 30 min. In comparison, the LOD for the target DNA in 50% and 100% synthetic urine was 18.7 and 33.2 nM, respectively.