Microchip electrophoresis with enhanced dark-field illumination detection for fast separation of native single super-paramagnetic nanoparticles

Abstract

Fast microchip electrophoretic (ME) separation of native super-paramagnetic nanoparticles (SPMNPs) with different functional groups (i.e., - NH 2, - OH, and - COOH) was investigated at the single-particle level using enhanced dark-field illumination detection with high signal-to-noise ratio. The dynamics provide evidence of the random motion of individual native nanoparticles and their real-time velocities within a microchip with or without an electric field. The SPMNPs were introduced into the microchip by magnetic force, and separation was performed at different electric field strengths; neither low (≤30 V/cm) nor high (≥70 V/cm) applied electric field strengths provided separation above baseline (resolution > 1.5) due to the random motion of the nanoparticles. Based on the optimized separation conditions obtained at the single-particle level, the individual SPMNPs were separated successfully from the model nanoparticle mixture within ∼75 s using differences in acid dissociation constants and zeta potentials.