Single-molecule sizing through nano-cavity confinement

An approach relying on nano-cavity confinement is developed in this paper for the sizing of nanoscale particles and single biomolecules in solution. The approach, termed nano-cavity diffusional sizing (NDS), measures particle residence times within fluidic nano-cavities to determine their hydrodynamic radii. Using theoretical modeling and simulation, we show that the residence time of particles within nano-cavities above a critical timescale depends on the diffusion coefficient of the particle, which allows estimation of the particles size. We demonstrate this approach experimentally through measurement of particle residence times within nano-fluidic cavities using single-molecule confocal microscopy. Our data show that the residence times scale linearly with the sizes of nanoscale colloids, protein aggregates and single DNA oligonucleotides. NDS thus constitutes a new single molecule optofluidic approach that allows rapid and quantitative sizing of nanoscale particles for potential application in nanobiotechnology, biophysics, and clinical diagnostics. Table of content graphic O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=110 SRC="FIGDIR/small/472369v2_ufig1.gif" ALT="Figure 1"> View larger version (34K): org.highwire.dtl.DTLVardef@15abf7eorg.highwire.dtl.DTLVardef@d2180dorg.highwire.dtl.DTLVardef@1290f57org.highwire.dtl.DTLVardef@ae2087_HPS_FORMAT_FIGEXP M_FIG C_FIG