Ultra-sensitive 17β-estradiol detection using optical fiber plasmonic spectra based on ssDNA-modified gold-coated tilted fiber Bragg grating

17β-estradiol, a crucial female sex hormone involved in various physiological processes, is of significant importance in clinical diagnosis. Here, a single-stranded DNA (ssDNA) aptamer-functionalized gold-coated tilted fiber Bragg grating (TFBG) was proposed for high-sensitivity 17β-estradiol detection. Surface plasmon resonance (SPR) could be excited on the gold-coated tilted fiber Bragg grating surface. The ssDNA self-assembled on this surface facilitated the binding of 17β-estradiol molecules, leading to localized refractive index alterations, resulting in a high-sensitivity 17β-estradiol detection. Experimental results indicate that the proposed sensor exhibits a sensitivity of 0.14 nm/lg(M) and a low limit of detection of 0.28 fM under the concentration range of 0.1 fM to 1 pM, representing a significant improvement in the field of SPR-based fiber-optic sensor.