ABSTRACT The combined opto‐electrochemical (Opto‐EC) platform enables non‐invasive, real‐time monitoring of biochemical kinetics, electron‐transfer processes, and surface‐binding events. Here, we detect the CA15‐3 breast‐cancer biomarker using free and randomly gold‐nanourchin (GNU)–conjugated antibodies (mAb) within a serum droplet, integrated into a time‐resolved Opto‐EC immunoassay on an indium‐tin‐oxide (ITO) film. Biolayer formation on the ITO surface alters charge‐transfer dynamics and reduces surface‐potential differences. Time‐resolved FT‐NIR spectroscopy reveals peaks at 4083, 4555, and 5560–6000 cm −1 , associated with overtone and combination bands of OH, NH, and mixed NH/CH vibrations. Stochastic FT‐NIR and SERS fluctuations reflect time‐dependent conformational changes, binding‐site accessibility, and vibrational‐mode variations. Correlation‐coefficient dynamics indicate shifts in the analyte's molecular environment, influencing PCA clustering. A time‐mapped Raman heatmap further tracks evolving peak positions and intensities, offering complementary insight into biomarker–sensor interactions. The free and randomly conjugated antigen–antibody system exhibits nonlinear stochastic behavior.
Khosroshahi et al. (Wed,) studied this question.
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