A programmable PNs/Au@PDA NPs double-layer structure modified optical fiber SPR biosensor

At present, optical fiber surface plasmon resonance (SPR) biosensing technology faces two significant challenges, enhancing the detection performance and expanding the detected target types. To address this, this paper proposes a novel optical fiber SPR biosensor, modified with programmable polypeptide nanofibers (PNs) and polydopamine nanospheres covered gold nanoparticles (Au@PDA NPs). Peptide sequences have been applied in optical fiber SPR sensing due to their editable, self-assembling, and low-toxicity properties. In reported sensors, peptide sequences are engineered to self-assemble into peptide nanofibers, increasing the sensor’s specific surface area and providing customizable active sites. Au@PDA NPs further enhance the refractive index sensitivity and surface activity of the sensor. In this study, an SPR biosensor was employed to detect rabbit IgG. The results demonstrate a biological sensitivity of 0.0262 nm/(ng/mL) and a detection limit of 3.85 ng/mL. Compared to SPR sensors modified with single nanoparticles, the proposed sensor exhibits significant improvements in both sensitivity and detection limit. In addition to performance enhancement, this work also offers a systematic approach to improving the performance of sensors for different targets. By programming peptide sequences, various detectable substances can be detected. The method is cost-effective and highly efficient, which holds great significance for improving the commercial value of optical fiber SPR sensors.