The negative differential resistance (NDR) peak current observed in redox active self-assembled monolayer-based molecular junctions has been attenuated by controlling the composition of the molecular junction. Two approaches studied here include capping the electroactive ferrocenyl groups with beta-cyclodextrin and functionalizing the scanning tunneling microscope tip used to probe the self-assembled monolayer (SAM) with n-alkanethiols of different lengths. These are the first examples of systematic modification of the magnitude of the NDR response in a molecule-based system.

The relative conductance of two different electroactive thiol molecules (containing ferrocene and viologen headgroups) inserted into an n-alkanethiolate background SAM was tracked over time using a scanning tunneling microscope. Both types of inserted molecules exhibited stochastic variation in their conductance. This phenomenon of “blinking” thus appears to be quite general, despite the fact that these two molecules are structurally different from one another and from molecules in which this phenomenon had been studied previously. This behavior is most simply rationalized as conformational and/or orientational changes of one or a small collection of molecules over time.

PLGA-NP applied to the RWM may have potential for sustained therapy to the inner ear.

Superparamagnetic iron oxide nanoparticles (SNP) composed of magnetite (Fe₃O₄) were studied preliminarily as vehicles for therapeutic molecule delivery to the inner ear and as a middle ear implant capable of producing biomechanically relevant forces for auditory function. Magnetite SNP were synthesized, then encapsulated in either silica or poly (D,L,-Lactide-co-glycolide) or obtained commercially with coatings of oleic acid or dextran. Permanent magnetic fields generated forces sufficient to pull them across tissue in several round window membrane models (in vitrocell culture, in vivo rat and guinea pig, and human temporal bone) or to embed them in middle ear epithelia. Biocompatibility was investigated by light and electron microscopy, cell culture kinetics, and hair cell survival in organotypic cell culture and no measurable toxicity was found. A sinusoidal magnetic field applied to guinea pigs with SNP implanted in the middle ear resulted in displacements of the middle ear comparable to 90 dB SPL.

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