Cellular analyses for label-free and rapid HER2-positive cancer diagnosis based on SPRi-modified with nanobody

Overexpression of human epidermal growth factor receptor-2 (HER2) is an important prognostic indicator for clinical diagnosis, as it results in more invasive cancer cells and lower survival rates. In this study, we developed a novel immunosensor based on surface plasmon resonance imaging (SPRi) modified with nanobody 2 (NB2) to detect the HER2 expression of various cancer cells. Firstly, we established a multi-channel intensity interrogation SPRi system with a refractive index resolution (RIR) of 1 × 10−6 RIU. Then, we fabricated the immunosensor by immobilizing NB2 nanobody on the sensor chip through affinity-based orientation. The NB2 exhibited high specificity for HER2 extracellular domain, enabling specific capture of HER2-positive cancer cells. The results revealed that the sensor could detect the HER2 expression of various living cancer cells by directly injecting cell suspensions. Compared with flow cytometry, SPRi system could obtain similar HER2 expression results with better performance, such as faster response time (<30 min), smaller sample volume (<200 μL), and lower cell concentration (105 cells/mL). The most important of all is that researchers do not need to take complex fluorescent labeling pretreatment of cell samples. Therefore, such immunosensors may offer great potential for rapid personalized treatment planning and enhanced patient outcomes.