1. Plasmonic Single-Molecule Affinity Detection at 10 -20 Molar.
- Author
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Macchia E, Franco CD, Scandurra C, Sarcina L, Piscitelli M, Catacchio M, Caputo M, Bollella P, Scamarcio G, and Torsi L
- Abstract
DNA can be readily amplified through replication, enabling the detection of a single-target copy. A comparable performance for proteins in immunoassays has yet to be fully assessed. Surface-plasmon-resonance (SPR) serves as a probe capable of performing assays at concentrations typically around 10⁻⁹ molar. In this study, plasmonic single-molecule assays for both proteins and DNA are demonstrated, achieving limits-of-detections (LODs) as low as 10⁻
2 ⁰ molar (1 ± 1 molecule in 0.1 mL), even in human serum, in 1 h. This represents an improvement in typical SPR LODs by eleven orders-of-magnitude. The single-molecule SPR assay is achieved with a millimeter-wide surface functionalized with a physisorbed biolayer comprising trillions of recognition-elements (antibodies or protein-probe complexes) which undergo an acidic or alkaline pH-conditioning. Potentiometric and surface-probing imaging experiments reveal the phenomenon underlying this extraordinary performance enhancement. The data suggest an unexplored amplification process within the biomaterial, where pH-conditioning, driving the biolayer in a metastable state, induces a self-propagating aggregation of partially misfolded proteins, following single-affinity binding. This process triggers an electrostatic rearrangement, resulting in the displacement of a charge equivalent to 1.5e per 102 recognition elements. Such findings open new opportunities for reliable SPR-based biosensing at the physical detection limits, with promising applications in point-of-care plasmonic systems., (© 2025 The Author(s). Advanced Materials published by Wiley‐VCH GmbH.)- Published
- 2025
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