Single-molecule force manipulation facilitated multiple rereads of a drug-bound DNA at specified sites by surface-enhanced Raman spectroscopy.

Abstract

Single-molecule surface-enhanced Raman spectroscopy (SERS) directly probes the vibrational characteristics of individual molecules to uncover the information inaccessible from ensemble measurements. As a surface-sensitive technique, the amplification of SERS signal occurs upon the excitation of localized surface plasmon resonance in metallic nanostructures, which can overcome optical diffraction limit for spatial detections at a nanometer scale. Complementary to this passive detection technique, optical tweezers-based single-molecule force manipulation method enables the active control of a target molecule with the restricted orientation in three dimensions. By applying a stretching force to the target molecule, it provides high-frequency feedback in sub-milliseconds with sub-piconewton force resolution and sub-nanometer distance sensitivity. Combining the active molecular control and the passive molecular vibrational measurement, we have integrated the dual-traps optical tweezers technique with the Raman spectroscopic detection platform. Under precise single-molecule force manipulations, the real-time SERS readout of the specified sites of a drug-bound DNA are recorded and re-recorded multiple times in a programmable manner. Our results showcase the promise of this correlative molecular manipulation and detection approach for real-time, label-free, and multi-dimensional characterizations of a single target biomacromolecule with both high spatial resolution and high site-specified recognition accuracy.