A label-free biosensor based on E-SMS optical fiber structure for anti BSA detection

• Etched single–multimode–singlemode fiber optics is evaluated as a biosensor. • The functionalized E-SMS biosensor provides high selectivity in the detection of anti-BSA. • E-SMS sensor demonstrates tailored geometry, tailored spectral response, and repeatable sensitivity. • This sensor is highly reproducible, simple to construct and easy to implement. • E-SMS biosensor detects biological interactions up to 100 ng/mL. • This wavelength-modulated biosensor presents a sensitivity of up to 2.3 nm/(µg/ml). In this work, a novel, compact and highly sensitive Bovine Serum Albumin (BSA)–anti-BSA biosensor based on an etched single-mode–multimode–single-mode (E-SMS) optical fiber structure is presented. This biosensor based on the multimode interference produced into an E-SMS structure was fabricated by chemical etching of the cladding region of the multimode fiber, followed by the functionalization of this etched region with BSA. The functionalized E-SMS biosensor provided high selectivity in the detection of anti-BSA, with the ability to detect biological interactions up to 100 ng/mL and a sensitivity of 2.3 nm/(µg/ml). This sensitive label-free biosensor has potential to be widely applied to various areas such as disease detection, medical diagnosis, and food safety inspection.