Electrochemically controlled release of dexamethasone from conducting polymer polypyrrole coated electrode

Abstract

Chronic recordings from micromachined neural electrode arrays often fail a few weeks after implantation primarily due to the formation of an astro-glial sheath around the implant. We propose a drug delivery system, from conducting polymer (CP) coatings on the electrode sites, to modulate the inflammatory implant-host tissue reaction. In this study, polypyrrole (PPy) based coatings for electrically controlled and local delivery of the ionic form of an anti-inflammatory drug, dexamethasone (Dex), was investigated. The drug was incorporated in PPy via electropolymerization of pyrrole and released in PBS using cyclic voltammetry (CV). FTIR analysis of the surface showed the presence of Dex and polypyrrole on the coated electrode. The thickness of the coated film was estimated to be ~50 nm by ellipsometry. We were able to release 0.5 µg/cm 2 Dex in 1 CV cycle and upto 92% Dex after 30 CV cycles. In-vitro studies and immunocytochemistry on murine glial cells suggest that the released drug lowers the count of reactive astrocytes to the same extent as the added drug. In addition, the released drug is not toxic to neurons as seen by healthy neuronal viability in the released drug treated cells.

Electrodeposited conductive polymers for controlled drug release: polypyrrole

“…Additionally, a drug delivery system should provide the drug locally, for example, making neuro-growth factors in the brain available to treat neurodegenerative conditions such as Parkinsons, Alzheimers and Huntingtons and to overcome the blood-brain barrier that prevents the drug entering the brain. It has been suggested that drug delivery systems can provide anti-inflammatory medicaments and growth factors directly into the local vicinity of the implant [31]. Another application is in bone and tissue engineering where growth factors can be locally delivered at high concentrations with precise control [32][33][34].…”

“…By applying a negative potential, the polymer film is reduced and its cationic charge is neutralised, which causes the ejection of the anionic drug by electrostatic force synchronised with the ingress of hydrated cations into the polymer bulk. This leads to the film swelling [31,58]. However, holding the film under a negative stimulus potential for a period of time can cause the film to lose its electrical conductivity which is not always possible to recover [31].…”

Tunable conjugated polymers for bacterial differentiation

“…They have been used for bio-sensing [5][6][7], as electrodes for stimulation or recording [8,9], for controlling cell adhesion, proliferation [10][11][12] and stem-cell differentiation [13], for controlled drug release [14,15] and even to mechanically stimulate cells [16]. They can be fabricated electrochemically using various counter ions [17,18] and modified with a variety of biomolecules [5,6,19].…”

Enhanced drug loading capacity of polypyrrole nanowire network for controlled drug release

“…Recently, our group extended the application of PPy nanowire network to this field, obtaining an effective drug release system with high adenosine triphosphate (ATP) release efficiency [5]. 2 It is well known that CPs can be used as drug carriers due to their unique dopingdedoping and stimulus-responsive property [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22], where drugs can be incorporated into CPs as dopants and then be released upon electrical stimulation. Therefore, the capacity of drug loading is dependent on the doping level (which is usually low) and the type of drugs is restricted to the charged and small molecules.…”