Electrically tunable organic bioelectronics for spatial and temporal manipulation of neuron-like pheochromocytoma (PC-12) cells.

BACKGROUND: Organic bioelectronic devices consisting of alternating poly(3,4-ethylenedioxythiophene) (PEDOT) and reduced graphite oxide (rGO) striped microelectrode arrays were fabricated by lithography technology. It has been demonstrated that the organic bioelectronic devices can be used to spatially and temporally manipulate the location and proliferation of the neuron-like pheochromocytoma cells (PC-12 cells). METHODS: By coating an electrically labile contact repulsion layer of poly(l-lysine-graft-ethylene glycol) (PLL-g-PEG) on the PEDOT electrode, the location and polarity of the PC-12 cells were confined to the rGO electrodes. RESULTS: The outgrowth of spatially confined bipolar neurites was found to align along the direction of the 20µm wide electrode. The location of the PC-12 cells can also be manipulated temporally by applying electrical stimulation during the neurite differentiation of PC-12 cells, allowing the PC-12 cells to cross over the boundary between the PEDOT and the rGO regions and construct neurite networks in an unconfined manner where the contact repulsive coating of PLL-g-PEG was removed. CONCLUSIONS: This adsorption and desorption of the PLL-g-PEG without and with electrical stimulation can be attributed to the tunable surface properties of the PEDOT microelectrodes, whose surface charge can switch from being negative to positive under electrical stimulation. GENERAL SIGNIFICANCE: The electrically tunable organic bioelectronics reported here could potentially be applied to tissue engineering related to the development and regeneration of mammalian nervous systems. The spatial and temporal control in this device would also be used to study the synapse junctions of neuron-neuron contacts in both time and space domains. This article is part of a Special Issue entitled Organic Bioelectronics - Novel Applications in Biomedicine.

Surface modification of poly(2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH-PPV) by confined photo-catalytic oxidation.

In this study, the surface of π-conjugated polymer, poly(2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH-PPV), was successfully modified with the sulfate anion (SO(4-)) groups by the confined photo-catalytic oxidation (CPO). After the surface modification, the water contact angle of MEH-PPV is changed from 95.5° to 82.1° without influence on its optical properties (based on the UV and PL spectra), and the water droplet can be absorbed on the modified MEH-PPV surface without sliding even at substrate tilt angles of 90° and 180°. The CPO on the MEH-PPV surface is able to further expand the use of MEH-PPV for applications. In addition, the water transport test indicates that the modified MEH-PPV can be a candidate for transporting water droplet.

Self-assembly behavior and photoluminescence property of bispyrenyl-POSS nanoparticle hybrid.

Two flexible ether bonds were designed to connect two pyrene rings on a polyhedral oligomeric silsesquioxane (BPy-POSS) to enrich the fraction of "intrinsic intramolecular pyrene-dimer" on the surface of crystal isobutyl-POSS (iBu-POSS) thin-films. Compared to the monomer emission of 1-pyrenemethanol (Py-OH), the emission spectra of BPy-POSS in dichloromethane show the large proportion of intramolecular and intermolecular excimers due to the formation of pyrenyl dimers or aggregates via the easy rotation of two adjacent ether bonds and the π-π interaction of pyrene rings, respectively. By blending inert iBu-POSS, the fluorescent dimers or aggregates of 5 wt.% and 20 wt.% BPy-POSS are distributed on the surface of iBu-POSS crystal fractal pattern as shown by confocal photoluminescence microscopy. Upon exposure to the vapors of nitrobenzene, the 5 wt.% BPy-POSS blend shows the similar quenching efficiency as 100 wt.% BPy-POSS blends, indicating the better excimer dispersion for vapor permeability of blend thin-films.

The Self-Assembled Structure of the Diblock Copolymer PCL-b-P4VP Transforms Upon Competitive Interactions with Octaphenol Polyhedral Oligomeric Silsesquioxane.

This paper describes the miscibility and self-assembly, mediated by hydrogen-bonding interactions, of new block copolymer/nanoparticle blends. The morphologies adopted by the immiscible poly[(ε-caprolactone)-block-(4-vinyl pyridine)] (PCL-b-P4VP) diblock copolymer changes upon increasing the number of competitive hydrogen-bonding interactions after adding increasing amounts of octaphenol polyhedral oligomeric silsesquioxane (OP-POSS). Transmission electron microscopy reveals morphologies that exhibit high degrees of long-range order, such as cylindrical and spherical structures, at relatively low OP-POSS contents, and short-range order or disordered structures at higher OP-POSS contents. Analyses performed using differential scanning calorimetry, wide-angle X-ray diffraction, and FT-IR spectroscopy provide positive evidence that the pyridyl units of the P4VP block are significantly stronger hydrogen-bond acceptors toward the OH group of OP-POSS than are the CO groups of the PCL block, thereby resulting in excluded and confined PCL phases.