High sensitivity of biosensor is one of the most important factor to realize the accurate detection of biomarkers. To achieve this purpose, enhancing initial signal and amplifying the value of signal change are two main approaches. In this study, a novel signal-off photoelectrochemical (PEC) immunosensor for highly sensitive determination of insulin was developed upon dual inhibition effect of CuS-SiO₂ composites toward CdS sensitized carbon doped titanium dioxide (C-TiO₂/CdS). Due to the doping of carbon and sensitization of CdS, C-TiO₂/CdS sensitized structure was employed as ideal photoactive matrix, which provided stable and enhanced basal signal. To achieve the amplification of signal change value, CuS-SiO₂ composites were prepared and used as labels. On account of the competitively light harvesting and electron donors consuming by p-type semiconductor CuS, less light energy and electron donors arrived at the C-TiO₂/CdS sensitized structure. Besides, the remarkable steric hindrance effect of CuS-SiO₂ labeled secondary antibodies (CuS-SiO₂-Ab₂) conjugates obstructed the transfer of electrons and diffusion of the electron donors to the photoelectrode surface, leading to further decrease of photocurrent compared with the pure CuS nanoparticles. Greatly enhanced sensitivity is achieved due to the dual inhibition effect of CuS-SiO₂ composites on C-TiO₂/CdS. Taking advantage of the synergy effect of C-TiO₂/CdS sensitized structure and dual inhibition effect of CuS-SiO₂-Ab₂ bioconjugates, the as-prepared immunosensor for insulin exhibited high sensitivity and good stability with a low detection limit of 0.03 pg mL⁻¹. Additionally, the strategy provided an efficient and simple approach for signal amplification and held great promise for other PEC immunoassay development.

生物传感器的高灵敏度是实现生物标志物准确检测的最重要因素之一。为了达到这个目的，增强初始信号和放大信号变化的值是两种主要方法。在这项研究中，基于CuS-SiO ₂复合材料对CdS敏化的碳掺杂二氧化钛（C-TiO ₂ / CdS）的双重抑制作用，开发了一种用于高灵敏度测定胰岛素的新型信号关闭光电化学（PEC）免疫传感器。由于碳的掺杂和CdS的增感作用，C-TiO ₂ / CdS增感结构被用作理想的光敏基质，提供了稳定而增强的基础信号。为了实现信号变化值的放大，CuS-SiO ₂制备复合材料并用作标签。由于竞争性的光收集和电子给体被p型半导体CuS消耗，较少的光能和电子给体到达C-TiO ₂ / CdS敏化结构。此外，CuS-SiO ₂标记的二抗（CuS-SiO ₂ -Ab ₂）偶联物的显着的位阻效应阻碍了电子的转移和电子给体向光电极表面的扩散，从而导致光电流进一步降低。纯CuS纳米粒子。CuS-SiO ₂复合材料对C-TiO ₂的双重抑制作用极大地提高了灵敏度/ CdS。利用C-TiO ₂ / CdS敏化结构的协同作用和CuS-SiO ₂ -Ab ₂生物共轭物的双重抑制作用，所制备的胰岛素免疫传感器显示了高灵敏度和良好的稳定性，检出限低至0.03 pg mL ^-1。此外，该策略为信号放大提供了一种有效而简单的方法，并为其他PEC免疫测定的发展带来了广阔前景。