Label-Free, Ultra-low Detection Limit DNA Biosensor Employing Tilted Fiber Bragg Grating Functionalized by 3D Nanostructure Probes

A label-free, ultra-low detection limit DNA biosensor based on tilted fiber Bragg grating (TFBG) is proposed and demonstrated. Optical sensing interface of the TFBG is functioned by self-assembled 3D tetrahedral DNA nanostructure (TDN) probes with size of 17 base pairs to greatly enhance the sensing performance for DNA detection. DNA hybridization processes in various concentration of target DNA solutions are monitored according to the transmission spectral evolution of the TFBG in real-time, interrogated by narrow-linewidth laser source. Experimental results show that the detection response of the proposed DNA biosensor is ranged from 1 fM to 10 pM, with an ultra-low detection limit of ~3.4 aM. Single nucleotide mismatch recognition is also achieved. As compared to the sensing performance using single-strand DNA (ssDNA) probes, the detection limit is about 1000 times lower for using the TDN probes. The proposed DNA biosensor possesses desirable merits as label-free method, ultra-low detection limit, high specificity and fast response, making it a promising candidate for sensing applications in bioengineering, disease diagnosis and environmental science.