Biological matter is intrinsically organic and mostly soft. This is also true for nerve cells, which use electrical signals to detect sensations and control muscles. In contrast, electronic components are usually inorganic and rigid. Although both systems are electronically compatible, new artificial organic materials are needed to achieve neural devices with long-term stability.
In their recent communication in Advanced Materials, Mohammad Reza Abidian (University of Houston) and his co-workers report the fabrication of monodisperse conducting polymer microcups. Modulation of the cups’ physical surface properties precisely controls electrical properties and drug delivery characteristics.
Gold substrates are electrosprayed with monodisperse polylactic-co-glycolic acid (PLGA) microspheres that function as a template for the electrochemical polymerization of poly(pyrrole). Depending on the deposition charge densities, either microcups or spheres are obtained. Poly(pyrrole) deposition charge densities of 30–120 mC cm–2 result in partial coating of the PLGA microspheres with poly(pyrrole). Fully coated spheres appear at 180 mC cm–2 and dominate at 240 mC cm–2. Dissolving the PLGA with chloroform leaves stable poly(pyrrole) microcups, and confocal microscopy imaging of the poly(pyrrole) films shows a clear correlation between deposition charge density and film thickness.
Release of the drug dexamethasone from the microcups into water occurs in two phases—after a burst release of more than 65% within 2 hours, 10–15% undergoes sustained release over 250 hours. This sustained release phase does not depend on the deposition charge density or microcup morphology. Instead, release kinetics represent the release from a poly(pyrrole) film—which accounts for the majority of the surface area. In contrast, the initial burst release increases with deposition charge density and thus surface roughness and surface area.
To find out more about these size-tunable, conductive polymer microcups, please visit the Advanced Materials homepage.