Parallel Tapered Optical Fiber Biosensor for Highly Sensitive Detection of Mucin 1

We built a reflective parallel tapered optical fiber structure and used it as a biosensor for highly sensitive in situ detection of label-free Mucin 1 (MUC1). A sensing tapered optical fiber probe was prepared, and a reference probe of similar free spectral range (FSR) was connected in parallel to establish the optical Vernier effect. This arrangement amplified the refractive index (RI) sensitivity to 8.4 times that of a single sensing probe with 19845.22 nm/RIU. Meanwhile, the aptamer was chemically bonded to the surface of sensing probe to specifically detect MUC1. This biosensor has a linear wide detection range from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{-{10}}$ </tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{-{1}}$ </tex-math></inline-formula> mg/mL, with a high sensitivity of 12.56 nm/log(C/C0) and a low limit of detection (LOD) of 0.012 pg/mL. Significantly, the reflective structures, unlike transmissive ones, could be inserted into samples rather than requiring samples to be moved to the sensing area, which not only reduces the contamination of samples during movement but also enables the measurement of trace samples that cannot be transferred. Furthermore, this novel sensing structure with high sensitivity holds promise for the preliminary diagnosis and prognostic monitoring of cancer and has broad development prospects in clinical and therapeutic applications.