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Olfactory receptors are known for their high specificity, sensitivity, and nanometer‐sized sensing element, making them ideal for in situ odorant sensor applications. However, one of the major limitations of these sensors is the requirement for an aqueous environment to maintain their function, while most odorants are poorly soluble in water. To address this issue, a microfluidic device consisting of a gas‐flow channel and a microwell is proposed that enables the effective dissolution of a gaseous odorant in an aqueous solution. Computational simulations are used to design the gas‐flow channel and the well, and the performance of the odorant dissolution is verified using the fabricated device. This study considers that convection in water induced by the gas flow enhances the dissolution of a gaseous odorant. The feasibility of the device is demonstrated for on‐site detection of a gaseous odorant. This approach facilitates the development of highly responsive and portable sensors utilizing olfactory receptors, offering a promising solution to the limitations of current odorant sensors. [ABSTRACT FROM AUTHOR]

We present a microarray system that enables simultaneous monitoring of multiple ionic currents through transmembrane a-hemolysin nanopores arrayed at bilayer lipid membranes. We applied the self-assembling ability of lipid molecules interfaced between an aqueous solution and organic solvent to induce bilayer membrane formation at a microfluidic device; the device consists of a hydrophobic polymer film that serves to suspend the lipid-containing solvent at micrometer-sized apertures as well as to separate the aqueous solution into two chambers. In this study, we confirmed that expeditious and reproducible bilayer formation is realized by control of the composition of the solvent, a mixture of n-decane and 1-hexanol, which permits simultaneous incorporation of the a-hemolysin nanopores to the membrane array. Monitoring the eight wells on the array at once, we obtained a maximum of four relevant, synchronous signals of translocating ionic current through the nanopores. The system was also able to detect translocation events of nucleic acid molecules through the pore via the profile of a blocked current, promising its potential for high-throughput applications. 10.1021/ac901732z

Structural integrity and functional characteristics of biomacromolecules are largely defined by electrostatic forces between ionized moieties, which are often altered at interfaces. Unraveling these changes requires access to charge state and structure of surface-confined biopolymers in aqueous environments. We therefore combined electrokinetic measurements of interracial electrical potentials with the simultaneous determination of the optical layer thickness by reflectometric interference spectroscopy. Two examples are summarized to demonstrate the resulting options: The pH-switching of grafted poly(L-glutamic acid) layers caused by dissociation-dependent helix--coil transitions was studied; potential distribution and ion mobility within the grafted polyelectrolyte were unraveled using an new theoretical model for the charging of polyelectrolyte layers. The charge-driven modulation of biopolymers at interfaces was furthermore analyzed in the adsorption of fibronectin onto polymer substrates with varied charge density; the results permit us to reach a conclusion about the relevance of electrostatic matching for orientation and anchorage of the protein. Altogether, the introduced methodology was found suitable to follow the electrosurface characteristics of biomacromolecules in situ.

Adsorption and desorption of fibronectin (FN) were investigated at thin films of alternating maleic acid copolymers with octadecene (POMA) and with propene (PPMA). The results reveal that the interfacial mode of adsorbed FN depends on the predominant interactions and large amounts of FN were tightly bound to POMA by hydrophobic interactions whereas FN adsorbed on PPMA was concluded to attain an unfolded structure allowing for the electrostatic matching of positively charged residues on FN with the maleic acid groups.