Abstract: Optical fiber surface plasmon resonance (SPR) sensor has some challenges for its wide applications, such as difficulties of fabrication, complexities of sensitivity enhancement methods, and high costs. To solve these problems, a highly sensitive SPR biosensor was fabricated in this study. A commercial multimode optical fiber was used with a conventional coating method. The fiber was pretreated by physical method, and the gold nanoparticle film was plated vertically in the ion sputtering instrument. Following these processes, the optimization of coating parameters was conducted by using the spectral shift sensitivity of the relative refractive index of the solution as the index. Then, an SPR sensing system was developed with this new biosensor, tungsten lamp light source, Y-type optical fiber, spectrometer and spectral test and analysis software. The results demonstrated that the coating current and coating time were 15 mA and 20 s respectively. Characterization of the sensor's structure of this biosensor with scanning electron microscope (SEM) showed that a layer of non-uniform gold nanoparticle film with a gradual decrease in axial particle size from the front end to the tail end was sputtered on the surface of the fiber. The sensitivity of the sensor can reach 3416 nm/RIU in the refractive index range of 1.339~1.384 with different concentrations of glycerol aqueous solution as samples. On this basis, the optical fiber SPR sensor was carboxylated followed by cross-linking with Protein A ligand and an SPR biosensor was prepared for HIgG immunoassay. The results showed that the linear correlation coefficient R2 of the sensor for HIgG immunoassay in the range of 1.25~20.00 μg/mL was 0.9987, and the sensitivity and detection limit were 0.6786 nm/(μg/mL) and 0.15 μg/mL, respectively, which were comparable to those of sensors reported in the literature that underwent complex sensitization processes. In summary, the novel SPR biosensor has the advantages of simple fabrication process, stable performance and high sensitivity, which has a wide range of application prospects.

Key words: surface plasmon resonance, commercial multimode optical fiber, biosensor, non-uniform gold film layer

摘要： 针对光纤SPR传感器制备难度大、增敏手段复杂、成本高等问题，本工作采用商用多模光纤，使用常规镀膜方法，优化镀膜条件后，成功制备出高灵敏度的光纤SPR传感器，并集成了一套光纤SPR传感系统。结果表明，优化后的最佳镀膜条件为：镀膜电流15 mA，镀膜时间20 s。通过SEM对传感器结构进行表征，结果表明光纤表面形成了呈轴向粒径大小渐变的非均匀金纳米颗粒膜层。在折射率1.339~1.384范围内，传感器的灵敏度可达3416 nm/RIU。经羧基化后交联Protein A配体，将制备出的生物传感器对HIgG进行免疫检测，在1.25~20.00 μg/mL HIgG浓度范围内，其线性相关系数R2为0.9987，灵敏度和检测限分别为0.6786 nm/(μg/mL)和0.15 μg/mL，检测性能与文献中经复杂方法增敏后的传感器相当。本研究制备的光纤SPR生物传感器制备工艺简单、性能稳定、灵敏度高，具有广泛的应用前景。

关键词: 表面等离子体共振, 商用多模光纤, 生物传感器, 非均匀金膜层