Nanometer-scale pores have demonstrated potential for the electrical detection, quantification, and characterization of molecules for biomedical applications and the chemical analysis of polymers. Despite extensive research in the nanopore sensing field, there is a paucity of theoretical models that incorporate the interactions between chemicals (i.e., solute, solvent, analyte, and nanopore). Here, we develop a model that simultaneously describes both the current blockade depth and residence times caused by individual poly(ethylene glycol) (PEG) molecules in a single α-hemolysin ion channel. Modeling polymer-cation binding leads to a description of two significant effects: a reduction in the mobile cation concentration inside the pore and an increase in the affinity between the polymer and the pore. The model was used to estimate the free energy of formation for K þ -PEG inside the nanopore (≈ − 49.7 meV) and the free energy of PEG partitioning into the nanopore (≈0.76 meV per ethylene glycol monomer). The results suggest that rational, physical models for the analysis of analyte-nanopore interactions will develop the full potential of nanopore-based sensing for chemical and biological applications.alpha-hemolysin | nanopore-based sensing | polymer confinement | polymer analysis P olymers play a fundamental role in life (1) and are central to many emerging technologies (2). Many of these applications require a detailed understanding of the structure, morphology, and chemical interactions of polymers under confinement in either 2-dimensional films (3) or narrow tubes (4). The ability to isolate and study single molecules has shown promise in overcoming the limitations of measurements with ensemble averages and permits probing the inter-and intra-molecular forces, structural changes, and dynamics of polymers (for a detailed review of single-molecule polymer analysis see refs. 5 and 6).Molecules partition into a nanopore and alter the flow of ions resulting in distinct current blockades that can be used to detect, characterize, and quantify a wide range of polymer types (7). These include single-stranded RNA and DNA (8-10), proteins (11-14), biowarfare agents (15), therapeutic agents against anthrax toxins (15, 16), and chemically synthesized molecules (14,(17)(18)(19)(20). More recently, single nanopores were used to determine the size distribution of polymers in a manner akin to mass spectrometry (19).To fully realize the potential of nanopore-based sensors, it is important to develop a detailed understanding of the physical and chemical interactions of polymers with the nanopore, solvent, electrolyte, and other components. In this work, the interaction between poly(ethylene glycol) (PEG) and the α-hemolysin (αHL) channel in a high ionic strength electrolyte was used to develop a unique model of polymers confined within single nanopores.Previous attempts to describe the magnitude of PEG-induced nanopore current blockades focused on volume exclusion (21) and/or microviscosity (22), which required adjustable ad hoc...

Nitric oxide (NO)-releasing sol-gel materials are synthesized by combining aminefunctionalized alkoxysilanes (aminosilanes) with alkyltrimethoxysilanes (alkylsilanes). Upon hydrolysis and condensation, the amine-functionalized silanes are covalently bound to the alkyltrimethoxysilane backbone and easily converted to diazeniumdiolate NO donors via exposure to high pressures of NO. Immersion of the sol-gel into solution is not required to initiate NO release. The NO-release characteristics of the sol-gels are easily controlled by varying the type and amount of the aminosilane precursor in the sol. The sol-gel coatings release NO for up to 20 d with average fluxes between 8.0 × 10 -12 and 5.6 × 10 -11 mol‚s -1 ‚cm -2 (coating thickness of 50 µm) over the first 10 h. These materials exhibit reduced platelet and bacterial adhesion. The results indicate that sol-gel chemistry may be an effective strategy for preparing coatings that release NO both controllably and locally for a range of applications including blood-and tissue-based devices.

No abstract

No abstract

No abstract