Attaching DNA to Nanoceria: Regulating Oxidase Activity and Fluorescence Quenching

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Applied Materials and Interfaces copyright © American Chemical Society after peer review and technical editing by publisher. To access the final edited and published work see Pautler, R., Kelly, E. Y., Huang, P.-J. J., Cao, J., Liu, B., & Liu, J. (2013). Attaching DNA to Nanoceria: Regulating Oxidase Activity and Fluorescence Quenching. ACS Applied Materials & Interfaces, 5(15), 6820–6825. https://doi.org/10.1021/am4018863Cerium oxide nanoparticles (nanoceria) have recently emerged as a nanozyme with oxidase activity. In this work, we present a few important interfacial properties of nanoceria. First, the surface charge of nanoceria can be controlled not only by adjusting pH but also by adsorption of simple inorganic anions. Adsorption of phosphate and citrate gives negatively charged surface over a broad pH range. Second, nanoceria adsorbs DNA via the DNA phosphate backbone in a sequence-independent manner; DNA adsorption inhibits its oxidase activity. Other anionic polymers display much weaker inhibition effects. Adsorption of simple inorganic phosphate does not have the inhibition effect. Third, nanoceria is a quencher for many fluorophores. These discoveries provide an important understanding for further use of nanoceria in biosensor development, materials science, and nanotechnology.University of Waterloo || Canadian Foundation for Innovation || Natural Sciences and Engineering Research Council || Ontario Ministry of Research and Innovation |

Coupling of biocomputing systems with electronic chips: Electronic interface for transduction of biochemical information

Electronic transduction of biochemical signals processed by the enzyme-based OR-Reset/AND-Reset logic systems was achieved using field-effect Si chips. The developed enzyme logic systems produced pH changes as the result of biochemical reactions activated by different combinations of the chemical input signals. Signal transduction was performed by pH-responding gold nanoparticles associated with the chip interface. The transformation of the nanoparticle shells between the dissociated (negatively charged) and protonated (neutral) states was determined using capacitance-voltage or impedance spectroscopy measurements, resulting in an electronic signal that reflects the state of the system corresponding to the logic output produced by the enzymes. The developed systems are the first examples of enzyme-based biocomputing systems interfaced with ordinary Si-based electronics

Synthesis and Properties of Asymmetric Heteroarm PEO n -b-PS m Star Polymers with End Functionalities

ABSTRACT: We report on the "core-first" synthesis of asymmetric three-and four-arm poly(ethylene oxide) (PEO)-polystyrene (PS) star polymers with functional terminal groups of a general formula PEO nb-PSm with n ) 0, 1, and 2 and n + m e 4. The synthesis was conducted by anionic polymerization of ethylene oxide and followed by atom transfer radical polymerization (ATRP) of styrene. The properties of asymmetric star-shaped macromolecules with different numbers of arms (n ) 1; m ) 2 and 3) and similar lengths of the PEO arm were compared with homoarm star polymers (PEO4 and PS4) and corresponding linear polymers. All star polymers obtained here possessed well-defined architecture with a relatively narrow molecular weight distribution as confirmed by NMR, FTIR, and arm-disassembling techniques. Star polymers showed suppression of melting temperature and lower crystallinity PEO phase due to the presence of a junction point. Preliminary studies demonstrated surface activities of these block copolymers with a rich polymorphism of micellar surface structures expected for amphiphilic block copolymers despite the presence of the bulky terminal functionalized groups

Hydrogel-Encapsulated Microfabricated Haircells Mimicking Fish Cupula Neuromast

A hydrogel-capped hair-cell flow microsensor, which closely mimics a superficial neuromast of a fish, is introduced. By encapsulating the hair sensor into the artificial hydrogel cupula a dramatic increase in hair-sensor sensitivity to the oscillating and the steady flow is achieved. It opens the way toward the remote monitoring of the underwater environment by autonomous, unmanned microvehicles with self-navigating capability

Gating-associated conformational changes in the mechanosensitive channel MscL

Bacterial cells avoid lysis in response to hypoosmotic shock through the opening of the mechanosensitive channel MscL. Upon channel opening, MscL is thought to expand in the plane of the membrane and form a large pore with an estimated diameter of 3–4 nm. Here, we set out to analyze the closed and open structure of cell-free MscL. To this end, we characterized the function and structure of wild-type MscL and a mutant form of the protein (G22N MscL) that spontaneously adopts an open substate. Patch-clamp analysis of MscL that had been reconstituted into liposomes revealed that wild-type MscL was activated only by mechanical stimuli, whereas G22N MscL displayed spontaneous opening to the open substate. In accord with these results, Ca2+ influx into G22N MscL-containing liposomes occurred in the absence of mechanical stimulation. The electrophoretic migration of chemically cross-linked G22N MscL was slower than that of cross-linked wild-type MscL, suggesting that G22N MscL is in an expanded form. Finally, electron microscopy using low-angle rotary shadowing revealed the presence of a pore at the center of G22N MscL. No pore could be detected in wild-type MscL. However, wild-type MscL possessed a protrusion at one end, which was absent in G22N MscL. The deletion of carboxyl-terminal 27 residues resulted in the loss of protrusion and proper multimerization. The structures of wild-type and G22N MscL reveal that the opening of MscL is accompanied by the dissociation of a carboxyl-terminal protrusion and pore formation