Modulation of the Drag Force Exerted by Microfluidic Flow on Laser-Trapped Particles: A New Method to Assess Surface-Binding Kinetics, Analyte Size, and Solution Viscosity

Abstract

trap particles under significantly lower Direct Current (DC) compared to the conventional iDEP schemes. The electrokinetic forces and the trapping mechanisms were systematically studied by investigating the relationship between the nanoparticles trapping and physical aspects of the system including the ionic strength of the solution, the electric field strength, and the pore geometry and size. The results indicate that the minimum required voltage to effectively trap particles can be as low as 1 V/cm. The quantity of trapped particles was determined by the net electrokinetic force comprise of the DEP, EP and EOF forces and the initial velocity of the particles before entering the trapping area, which depends on the pore geometry and the ionic strength. This proofof concept study paves the way to further utilize the nanopipette-iDEP device for entrapment of the biomolecular entities from bodyfluids or cell culture media in biosensing applications.

Plasmonic scattering imaging of single proteins and binding kinetics

“…We constructed an image intensity histogram from the PSM images of IgG and obtained the mean intensity by fitting the histogram with a Gaussian function ( Figure 4e ), from which the diameter of IgG was found to be 12.9 ± 2.5 nm. This value agrees with the hydrodynamic diameter measured by DLS (12.0 ± 2.0 nm) and also with the value reported in literature 35 . We performed a control experiment by introducing IgA to the CaM coated surface and did not observe binding of IgA to CaM, which confirms the specific binding of anti-CaM to CaM ( Supplementary Video 3 and Figure 4f ).…”

Quantification of Single-Molecule Protein Binding Kinetics in Complex Media with Prism-Coupled Plasmonic Scattering Imaging

“…After tracking these binding events and calculating their image intensities, the intensity histograms are constructed as shown in Figure a–d. The histogram width results from the intensity fluctuations of binding events, which may be caused by the protein mass, conformation, and orientation heterogeneities. , Gaussian distribution was employed to fit these histograms. The small secondary peaks in the histograms may be created by the formation of dimers or two proteins binding to adjacent locations within the diffraction limit simultaneously.…”