Biomedical subjects

Malika Jeffries-El

Publications and source records attributed to Malika Jeffries-El.

3 recordsLinked to original sources

PubMed2006

Self-assembled monolayers of polythiophene conductive polymers improve biocompatibility and electrical impedance of neural electrodes.

There is continued interest in the development of conductive polymer coatings to improve the electrical properties and biocompatibility of electrodes for neural prostheses. We present here a new type of coating, based on mixed self-assembled monolayers (SAMs) of thiolated poly(alkylthiophene)s and functionalized alkanethiols. When assembled as a SAM on electrodes designed for in vitro electrophysiology, these polymers are able to significantly lower electrode impedance at 1 kHz. The same mixed formulation is able to promote the outgrowth of neurites from primary mouse cortical neurons when the alkanethiol component is functionalized with a neural cell adhesion molecule (NCAM) binding antibody. Atomic force microscopy of the SAMs shows that they exert their effect through the well-known mechanism of increasing electrode surface area. These new covalently bound films have the potential to be more robust and are more controllable in their composition than existing electrodeposited conductive polymer coatings.

Animals↗

PubMed2006

Nanostructure dependence of field-effect mobility in regioregular poly(3-hexylthiophene) thin film field effect transistors.

Low polydispersity regioregular polythiophenes with number average molecular weights ranging from 2 to 13 kDa were cast under the same conditions from solution to form a series of field effect transistors (FETs). Tapping mode AFM and grazing incidence small-angle X-ray scattering revealed that in all cases the polymers formed regular nanofibrillar morphologies with the width of nanofibrils proportional to the weight average contour length of polymer chains, indicating that conjugated backbones were oriented perpendicular to the nanofibril axes. FET charge carrier mobilities exhibited exponential dependence on nanofibril width, pointing to the decisive role of extended conjugated pathways in charge transport.

Microscopy, Atomic Force↗

PubMed2006

Volatile organic compound detection using nanostructured copolymers.

Regioregular polythiophene-based conductive copolymers with highly crystalline nanostructures are shown to hold considerable promise as the active layer in volatile organic compound (VOC) chemresistor sensors. While the regioregular polythiophene polymer chain provides a charge conduction path, its chemical sensing selectivity and sensitivity can be altered either by incorporating a second polymer to form a block copolymer or by making a random copolymer of polythiophene with different alkyl side chains. The copolymers were exposed to a variety of VOC vapors, and the electrical conductivity of these copolymers increased or decreased depending upon the polymer composition and the specific analytes. Measurements were made at room temperature, and the responses were found to be fast and appeared to be completely reversible. Using various copolymers of polythiophene in a sensor array can provide much better discrimination to various analytes than existing solid state sensors. Our data strongly indicate that several sensing mechanisms are at play simultaneously, and we briefly discuss some of them.

Electrochemistry↗