U-Shaped SPR Optical Fiber Sensor for the Detection of Acid Phosphatase

Acid phosphatase (ACP) holds significant importance in aspects related to human life and well-being. Consequently, there is a need to design a sensitive and accurate sensor. Herein, a sensitive and convenient U-shaped surface plasmon resonance (SPR) optical fiber sensor used for detecting ACP is developed. The U-shaped optical fiber sensor demonstrates remarkable sensitivity in the course of detection. A 50-nm-thick Au film was deposited on the surface of the U-bent optical fiber. When the radius of the fiber is 1 mm, the refractive index sensitivity can reach 5855 nm/RIU. Subsequently, a 20-nm-thick MnO₂ film was deposited on top of the Au film. Ascorbic acid (AA produced by ACP-catalyzed trisodium L-ascorbate-2-phosphate (AAP) can reduce MnO₂, as a result, it alters the refractive index (RI) on the surface of the optical fiber and brings about short-wavelength direction shift in the resonance wavelength. The linear detection range of this sensor is 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup>-1 mU/mL and the limit of detection (LOD) is 9.4×10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> mU/mL. With the high selectivity, and high sensitivity, this sensor is utilized for the detection of ACP within human urine samples, which indicates that this sensor is promising for application in real sample.