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

A label-free, ultralow detection limit deoxyribonucleic acid (DNA) biosensor based on tilted fiber Bragg grating (TFBG) is proposed and demonstrated. The optical sensing interface of the TFBG is functioned by self-assembled 3-D tetrahedral DNA nanostructure (TDN) probes with the size of 17 base pairs to greatly enhance the sensing performance for DNA detection. DNA hybridization processes in various concentrations of target DNA solutions are monitored according to the transmission spectral evolution of the TFBG in real-time, interrogated by a 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 ultralow detection limit of similar to 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 a label-free method, ultralow detection limit, high specificity, and fast response, making it a promising candidate for sensing applications in bioengineering, disease diagnosis, and environmental science.