A review of integrating electroactive polymers as responsive systems for specialized drug delivery applications

Abstract

Electroactive polymers (EAPs) are promising candidate materials for the design of drug delivery technologies, especially in conditions where an "on-off" drug release mechanism is required. To achieve this, EAPs such as polyaniline, polypyrrole, polythiophene, ethylene vinyl acetate, and polyethylene may be blended into responsive hydrogels in conjunction with the desired drug to obtain a patient-controlled drug release system. The "on-off" drug release mechanism can be achieved through the environmental-responsive nature of the interpenetrating hydrogel-EAP complex via (i) charged ions initiated diffusion of drug molecules; (ii) conformational changes that occur during redox switching of EAPs; or (iii) electroerosion. These release mechanisms are not exhaustive and new release mechanisms are still under investigation. Therefore, this review seeks to provide a concise incursion and critical overview of EAPs and responsive hydrogels as a strategy for advanced drug delivery, for example, controlled release of neurotransmitters, sulfosalicyclic acid from cross-linked hydrogel, and vaccine delivery. The review further discusses techniques such as linear sweep voltammetry, cyclic voltammetry, impedance spectroscopy, and chronoamperometry for the determination of the redox capability of EAPs. The future implications of the hydrogel-EAP composites include, but not limited to, application toward biosensors, DNA hybridizations, microsurgical tools, and miniature bioreactors and may be utilized to their full potential in the form of injectable devices as nanorobots or nanobiosensors.

Electroactive Polymers and Coatings

“…This has enabled, for example, the mimicry of basic insect and animal movements by investigators in the fi eld of biomimetics. There has been a shift in focus on EAPs as their actuation ability improves, as well as the availability of a wider selection of biomaterials [ 11 ]. However, this brings concerns with regard to the biocompatibility of these new materials [ 57 ].…”

“…Current intensity is infl uenced by the electrolyte employed, which ultimately affects the EAP quantity formed [ 65 ]. Solvents possess [ 11 ] various donor numbers infl uencing cationic monomer radical deprotonation, as well as possessing varying dielectric constants, infl uencing chain propagation [ 66 ]. Solvent choice further depends on it providing a medium with ionic conductivity and on its stability at the monomer's oxidation potential [ 64 ].…”

“…A limitation is that the alternating current can affect the results recorded. The employment of CA is important where determination of the migration fl ux of charged particles in EAPs is required through analysis in a constant electric fi eld of the concentration distribution and current-time plots of a polymer fi lm [ 11 ]. With regard to conductive EAPs, they can be applied in CA as sensors enabling detection of simple and complex electroactive or nonactive substances [ 83 ].…”

“…Inert materials (e.g., gold, platinum, or glass-like carbon) commonly comprise the anode employed for the polymerization reaction; partially reactive materials may dissolve with polarization of the anode [ 69 , 70 ]. The physicochemical properties of the synthesized EAP are implicitly based on the electropolymerization method instituted, but generally this approach imparts EAPs with comparable conductivity, for application in research and system design [ 11 ].…”

Electrochemical Activity and Electrical Properties of Optimized Polypyrrole Coatings on Iron

“…[18][19][20][21][22][23] Depending on the type of the doping agents, chemical, physical and electrical properties including electroactivity and redox capability of electrodeposited PPy film can be altered. 11 Many investigations have been performed in order to evaluate the redox capability based on * Electrochemical Society Active Member.…”