Study of cell and drug interactions based on dual-mode detection using SPR and fluorescence imaging.

The investigation of the interactions between cells and drugs forms a crucial aspect of biological and clinical medical studies. Generally, single-cell or local-cellular studies require a microscopic imaging system with high magnifications, which suffers from low detection throughputs and poor time responses. The study presented in this paper combined SPR and fluorescence to achieve cell localization, real-time monitoring of cell images and quantitative analysis of drugs. In order to obtain more comprehensive, accurate and real-time data, a dual-mode system based on surface plasmon resonance (SPR) and fluorescence was constructed based on a 4× magnification lens. This enables simultaneous studies of an entire cell and a specific region of the cell membrane. An adaptive adjustment algorithm was established for distorted SPR images, achieving temporal and spatial matching of the dual-mode detection. The combination of SPR and fluorescence not only achieved micro-detection but also complemented the qualitative or quantitative limitations of SPR or fluorescence method alone. In system characterization, the response signal of SPR was noticed to increase with the increasing concentration of EGF in stimulated cells. It indicated that this platform could be employed for quantitative detection of the cell membrane region. Upon addition of EGF, a peak in the SPR curve was observed, and the cells in the corresponding SPR image turned whiter. This indicated that the platform can simultaneously monitor the SPR response signal and image changes. The response time of fluorescence in EGF testing was several seconds earlier than SPR, revealing that signal transduction first occurred in the whole cell and then propagated to the cell membrane region. The inhibitory ability of Gefitinib on cells was verified in a fast and real-time manner within 20 min. The results indicated that the detection limit of this method was 20 IU/mL for EGF and 10 µg/mL for Gefitinib. In conclusion, this study demonstrates the advantages of SPR and fluorescence dual-mode techniques in the analysis of cell-drug interactions, as well as their strong potential in drug screening.

Multi-parameter surface plasmon resonance instrument for multiple nucleic acid quantitative detection.

Multiplex nucleic acid assays can simultaneously detect the characteristics of different target nucleic acids in complex mixtures and are used in disease diagnosis, environmental monitoring, and food safety. However, traditional nucleic acid amplification assays have limitations such as complicated operation, long detection time, unstable fluorescent labeling, and mutual interference of multiplex nucleic acids. We developed a real-time, rapid, and label-free surface plasmon resonance (SPR) instrument for multiplex nucleic acid detection. The multiparametric optical system based on total internal reflection solves the multiplex detection problem by cooperating with linear light source, prism, photodetector, and mechanical transmission system. An adaptive threshold consistency correction algorithm is proposed to solve the problem of inconsistent responsiveness of different detection channels and the inability of quantitative comparison. The instrument achieves label-free and amplification-free rapid detection of these biomarkers for miRNA-21 and miRNA-141, which are widely expressed in breast cancer and prostate cancer. The multiplex nucleic acid detection takes 30 min and the biosensor has good repeatability and specificity. The instrument has a limit of detection (LODs) of 50 nM for target oligonucleotides, and the smallest absolute amount of sample that can be detected is about 4 pmol. It provides a simple and efficient point-of-care testing (POCT) detection platform for small molecules such as DNA and miRNA.