Nanoscale Molecular Traps and Dams for Ultrafast Protein Enrichment in High-Conductivity Buffers

We report a new approach, <i>molecular dam</i>, to enhance mass transport for protein enrichment in nanofluidic channels by nanoscale electrodeless dielectrophoresis under physiological buffer conditions. Dielectric nanoconstrictions down to 30 nm embedded in nanofluidic devices serve as field-focusing lenses capable of magnifying the applied field to 10⁵-fold when combined with a micro- to nanofluidic step interface. With this strong field and the associated field gradient at the nanoconstrictions, proteins are enriched by the molecular damming effect faster than the trapping effect, to >10⁵-fold in 20 s, orders of magnitude faster than most reported methods. Our study opens further possibilities of using nanoscale molecular dams in miniaturized sensing platforms for rapid and sensitive protein analysis and biomarker discovery, with potential applications in precipitation studies and protein crystallization and possible extensions to small-molecules enrichment or screening

Nanoscale Molecular Traps and Dams for Ultrafast Protein Enrichment in High-Conductivity Buffers

We report a new approach, <i>molecular dam</i>, to enhance mass transport for protein enrichment in nanofluidic channels by nanoscale electrodeless dielectrophoresis under physiological buffer conditions. Dielectric nanoconstrictions down to 30 nm embedded in nanofluidic devices serve as field-focusing lenses capable of magnifying the applied field to 10⁵-fold when combined with a micro- to nanofluidic step interface. With this strong field and the associated field gradient at the nanoconstrictions, proteins are enriched by the molecular damming effect faster than the trapping effect, to >10⁵-fold in 20 s, orders of magnitude faster than most reported methods. Our study opens further possibilities of using nanoscale molecular dams in miniaturized sensing platforms for rapid and sensitive protein analysis and biomarker discovery, with potential applications in precipitation studies and protein crystallization and possible extensions to small-molecules enrichment or screening

Nanoscale Molecular Traps and Dams for Ultrafast Protein Enrichment in High-Conductivity Buffers

We report a new approach, <i>molecular dam</i>, to enhance mass transport for protein enrichment in nanofluidic channels by nanoscale electrodeless dielectrophoresis under physiological buffer conditions. Dielectric nanoconstrictions down to 30 nm embedded in nanofluidic devices serve as field-focusing lenses capable of magnifying the applied field to 10⁵-fold when combined with a micro- to nanofluidic step interface. With this strong field and the associated field gradient at the nanoconstrictions, proteins are enriched by the molecular damming effect faster than the trapping effect, to >10⁵-fold in 20 s, orders of magnitude faster than most reported methods. Our study opens further possibilities of using nanoscale molecular dams in miniaturized sensing platforms for rapid and sensitive protein analysis and biomarker discovery, with potential applications in precipitation studies and protein crystallization and possible extensions to small-molecules enrichment or screening

Nanoscale Molecular Traps and Dams for Ultrafast Protein Enrichment in High-Conductivity Buffers

We report a new approach, <i>molecular dam</i>, to enhance mass transport for protein enrichment in nanofluidic channels by nanoscale electrodeless dielectrophoresis under physiological buffer conditions. Dielectric nanoconstrictions down to 30 nm embedded in nanofluidic devices serve as field-focusing lenses capable of magnifying the applied field to 10⁵-fold when combined with a micro- to nanofluidic step interface. With this strong field and the associated field gradient at the nanoconstrictions, proteins are enriched by the molecular damming effect faster than the trapping effect, to >10⁵-fold in 20 s, orders of magnitude faster than most reported methods. Our study opens further possibilities of using nanoscale molecular dams in miniaturized sensing platforms for rapid and sensitive protein analysis and biomarker discovery, with potential applications in precipitation studies and protein crystallization and possible extensions to small-molecules enrichment or screening

Nanoscale Molecular Traps and Dams for Ultrafast Protein Enrichment in High-Conductivity Buffers

We report a new approach, <i>molecular dam</i>, to enhance mass transport for protein enrichment in nanofluidic channels by nanoscale electrodeless dielectrophoresis under physiological buffer conditions. Dielectric nanoconstrictions down to 30 nm embedded in nanofluidic devices serve as field-focusing lenses capable of magnifying the applied field to 10⁵-fold when combined with a micro- to nanofluidic step interface. With this strong field and the associated field gradient at the nanoconstrictions, proteins are enriched by the molecular damming effect faster than the trapping effect, to >10⁵-fold in 20 s, orders of magnitude faster than most reported methods. Our study opens further possibilities of using nanoscale molecular dams in miniaturized sensing platforms for rapid and sensitive protein analysis and biomarker discovery, with potential applications in precipitation studies and protein crystallization and possible extensions to small-molecules enrichment or screening

Effects of Topology and Ionic Strength on Double-Stranded DNA Confined in Nanoslits

We investigate experimentally the effects of electrostatic interactions and topological constraints on DNA dynamics in nanoslit confinement by studying the equilibrium shape and dynamics of single linear and circular λ-DNA confined in a silicon/glass nanoslit. Having examined the dependence of chain radius of gyration <i>R</i>_∥, shape asphericity <i>A</i>, and relaxation time τ on chain topology, slit height <i>h</i> (20–782 nm), and solvent ionic strength <i>I</i> (8.2–268.8 mM), it is found that the chain shape becomes more aspherical as <i>h</i> and <i>I</i> decrease. Moreover, in strong sub-Kuhn length confinement, the DNA relaxation time increases with decreasing <i>h</i> in a smooth and broad transition. Our results provide experimental evidence to confirm that the scaling exponents of radius of gyration and of relaxation time are the same for linear and circular DNA and help resolve conflicting observations of the qualitative dependencies of chain radius of gyration and relaxation time in sub-Kuhn length slits

Electrokinetic Preconcentration and Detection of Neuropeptides at Patterned Graphene-Modified Electrodes in a Nanochannel

Neuropeptides are vital to the transmission and modulation of neurological signals, with Neuropeptide Y (NPY) and Orexin A (OXA) offering diagnostic information on stress, depression, and neurotrauma. NPY is an especially significant biomarker, since it can be noninvasively collected from sweat, but its detection has been limited by poor sensitivity, long assay times, and the inability to scale-down sample volumes. Herein, we apply electrokinetic preconcentration of the neuropeptide onto patterned graphene-modified electrodes in a nanochannel by frequency-selective dielectrophoresis for 10 s or by electrochemical adsorptive accumulation for 300 s, to enable the electrochemical detection of NPY and OXA at picomolar levels from subnanoliter samples, with sufficient signal sensitivity to avoid interferences from high levels of dopamine and ascorbic acid within biological matrices. Given the high sensitivity of the methodology within small volume samples, we envision its utility toward off-line detection from droplets collected by microdialysis for the eventual measurement of neuropeptides at high spatial and temporal resolutions

Low-Copy Number Protein Detection by Electrode Nanogap-Enabled Dielectrophoretic Trapping for Surface-Enhanced Raman Spectroscopy and Electronic Measurements

We report a versatile analysis platform, based on a set of nanogap electrodes, for the manipulation and sensing of biomolecules, as demonstrated here for low-copy number protein detection. An array of Ti nanogap electrode with sub-10 nm gap size function as templates for alternating current dielectrophoresis-based molecular trapping, hot spots for surface-enhanced Raman spectroscopy as well as electronic measurements, and fluorescence imaging. During molecular trapping, recorded Raman spectra, conductance measurements across the nanogaps, and fluorescence imaging show unambiguously the presence and characteristics of the trapped proteins. Our platform opens up a simple way for multifunctional low-concentration heterogeneous sample analysis without the need for target preconcentration