Dynamic Single-Binding Event Profiling With on-Chip Microlenses for Wash-Free Digital Biosensing

Area of Science:

• Biomedical Engineering
• Nanotechnology
• Analytical Chemistry

Background:

• Conventional assays struggle with long incubation times and nonspecific binding.
• Kinetic assays offer real-time monitoring but require complex optics, limiting point-of-care use.
• There is a need for portable, user-friendly biosensors with high sensitivity and specificity.

Purpose of the Study:

• To develop a microlens-assisted platform for kinetic single-molecule detection using conventional microscopy.
• To enable wash-free digital biosensing with high sensitivity and specificity.
• To demonstrate the platform's utility for point-of-care diagnostics.

Main Methods:

• Utilized an on-chip microlens array to amplify scattering from gold nanoparticle labels.
• Employed conventional bright-field microscopy for real-time tracking of single-binding events.
• Analyzed dynamic fingerprints of binding events to differentiate specific from nonspecific interactions.

Main Results:

• Achieved kinetic monitoring with low-magnification optics and a compact optical configuration.
• Demonstrated wash-free digital biosensing with high sensitivity and specificity.
• Detected cardiac troponin I at an ultralow limit of 0.051 pg mL^-1 in undiluted serum samples.

Conclusions:

• The microlens-assisted platform provides a portable and user-friendly solution for kinetic biosensing.
• This technology enables laboratory-grade diagnostics at the point of need, improving acute myocardial infarction detection.
• The approach overcomes limitations of conventional assays and complex kinetic setups, paving the way for advanced point-of-care devices.