Betulin-loaded PEDOT films for regional chemotherapy.

Chemotherapy is one of the most commonly used cancer treatments. Even so, it has significant adverse effects on healthy tissues. These effects can be avoided through the use of regional chemotherapy, an approach based on delivering the anti-cancer agents locally, to the site of cancer tissue accumulation. Among the different classes of biomaterials that are used as drug carriers, conducting polymers allow reversible, electrostatic immobilization and controlled release of a variety of compounds. In this work, we describe a method for producing surfaces possessing anti-cancer activity, which are a potential tool for regional chemotherapy. Our method consists of covering the surface with a conducting polymer matrix, followed by loading that matrix with cytotoxic compounds. We have chosen betulin as the model compound for this study, as it is commonly available triterpene that exhibits cytotoxicity against a variety of tumor cell lines. The presence of betulin in the polymer matrix is confirmed by SEM, EDS and IR spectroscopy. The release of betulin is carried out using two protocols, i.e. passive mode (open circuit conditions) or active (application of constant potential) mode. The biological activity of betulin that was released from the matrix is confirmed by its toxic effect against KB and MCF-7 cancer cell lines (IC50 values of 13.34±0.88µg/mL and 12.57±1.81µg/mL for KB and MCF-7, respectively). The described method of surface modification is shown to be an effective mean of producing surfaces that possess anti-cancer activity, serving as advantageous materials for regional chemotherapy applications.

Biomaterial-based regional chemotherapy: Local anticancer drug delivery to enhance chemotherapy and minimize its side-effects.

Since the majority of anticancer pharmacological agents affect not only cancer tissue but also normal cells, chemotherapy is usually accompanied with severe side effects. Regional chemotherapy, as the alternative version of conventional treatment, leads to the enhancement of the therapeutic efficiency of anticancer drugs and, simultaneously, reduction of toxic effects to healthy tissues. This paper provides an insight into different approaches of local delivery of chemotherapeutics, such as the injection of anticancer agents directly into tumor tissue, the use of injectable in situ forming drug carriers or injectable platforms in a form of implants. The wide range of biomaterials used as reservoirs of anticancer drugs is described, i.e. poly(ethylene glycol) and its copolymers, polyurethanes, poly(lactic acid) and its copolymers, poly(ɛ-caprolactone), polyanhydrides, chitosan, cellulose, cyclodextrins, silk, conducting polymers, modified titanium surfaces, calcium phosphate based biomaterials, silicone and silica implants, as well as carbon nanotubes and graphene. To emphasize the applicability of regional chemotherapy in cancer treatment, the commercially available products approved by the relevant health agencies are presented.

An electrically controlled drug delivery system based on conducting poly(3,4-ethylenedioxypyrrole) matrix.

As numerous therapeutic agents are not well tolerated when administrated systemically, localized and controlled delivery can help to decrease their toxicity by applying an optimized drug concentration at extended exposure time. Among different types of drug delivery systems, conjugated polymers are considered as promising materials due to their biocompatibility, electrical conductivity and ability to undergo controllable redox reactions. In this work poly(3,4-ethylenedioxypyrrole), PEDOP, matrix is described for the first time as a reservoir of a model drug, ibuprofen (IBU). Drug immobilization process is performed in situ, during the electrochemical polymerization of 10 mM EDOP in the presence of 5-50 mM IBU. The loading efficiency of polymer matrix is dependent on IBU concentration and reaches 25.0±1.3 µg/cm2. The analysis of PEDOP-IBU chemical structure based on Raman spectroscopy, energy dispersive spectroscopy and surface morphology data provided by scanning electron microscopy shows that IBU is accumulated in the structure of matrix and evidently influences its morphology. IBU is then released in a controlled way under the influence of applied potential (-0.7 V vs. Ag/AgCl). It is demonstrated that the judicious choice of the synthesis conditions leads to a tailored loading efficiency of PEDOP matrix and to a tunable drug release.

Two approaches to the model drug immobilization into conjugated polymer matrix.

The purpose of this study is to develop biocompatible and conducting coating being carrier of biologically active compounds with the potential use in neuroprosthetics. Conducting polypyrrole matrix has been used to immobilize and release model drugs, quercetin and ciprofloxacin. Two routes of immobilization are described: drugs have been incorporated in the polymer matrix in the course of the electropolymerization process or after polymerization, in the course of polymer oxidation. Using UV/Vis spectroscopic detection we demonstrate that both immobilization approaches display different drug-loading efficiencies. In the case of ciprofloxacin, drug incorporation following synthesis is a more efficient immobilization approach (final drug concentration: 43.3 (±9.5) µM/cm(2)), while for quercetin the highest loading is accomplished by drug incorporation during synthesis (final drug concentration: 29.1 (±5.9) µM/cm(2)). The process of drug incorporation results in the variation of surface morphology with respect to the method of immobilization as well as the choice of drug. The results prove that electrochemical methods are efficient procedures for making multifunctional polymer matrices which might be perspective bioactive coatings for implantable neuroprosthetic devices.

Advancing the delivery of anticancer drugs: Conjugated polymer/triterpenoid composite.

Exemplifying the synergy of anticancer properties of triterpenoids and ion retention qualities of conjugated polymers, we propose a conducting matrix to be a reservoir of anticancer compounds. In this study, poly(3,4-ethylenedioxythiophene), PEDOT, based matrix for electrically triggered and local delivery of the ionic form of anticancer drug, oleanolic acid (HOL), has been investigated. An initial, one-step fabrication procedure has been proposed, providing layers exhibiting good drug release properties and biological activity. Investigation of obtained systems and implementation of modifications revealed another route of fabrication. This procedure was found to yield layers possessing a significantly greater storage capacity of OL(-), as evidenced by the 52% increase in the drug concentrations attainable through electro-assisted release. Examination of the biological activity of immobilised and released OL(-) molecules proved that electrochemical treatment has negligible impact on the anticancer properties of OL(-), particularly when employing the three-step procedure, in which the range of applied potentials is limited. PEDOT/OL(-) composite has been demonstrated to be a robust and cost-effective material for controlled drug delivery.

Radical cation of helical, cross-conjugated beta-oligothiophene.

The radical cation of carbon-sulfur [7]helicene is configurationally stable in solution at room temperature. In contrast to the radical cations of alpha-oligothiophenes, which form diamagnetic pi-dimers at low temperature, the radical cation of this helical, cross-conjugated beta-oligothiophene shows a low propensity toward dimerization.

Optically transparent diamond electrode for use in ir transmission spectroelectrochemical measurements.

A new analytical spectroelectrochemical methodology is reported on that utilizes an optically transparent boron-doped diamond thin film. The film was deposited on undoped Si by microwave-assisted chemical vapor deposition using a 4-h growth with a 0.5% CH4/H2 source gas mixture and 2 ppm B2H6 added for boron doping. The thin-film electrode possessed a transparency of 40-60% in the mid- and far-IR regions of the electromagnetic spectrum. The physical, electrical, optical, and electrochemical properties of the electrode were characterized by scanning electron microscopy, Raman spectroscopy, X-ray diffraction, four-point probe electrical resistance measurements, IR spectroscopy, and cyclic voltammetry. The film's electrochemical behavior was evaluated using both aqueous (Fe(CN)(6)3-/4-, methyl viologen, Ru(NH3)(6)3+/2+, and IrCl(6)2-/3-) and nonaqueous (ferrocene) redox systems. The film exhibited a low and stable background current and a nearly reversible voltammetric response for all these redox systems. The diamond/Si optically transparent electrode (OTE) and a thin-layer transmission cell were used to record the spectroelectrochemical response for 10 mM Fe(CN)(6)3-/4- in 1 M KCl. Difference IR spectra (oxidized minus reduced), recorded at various applied potentials, showed that the CN vibrational mode at 2039 cm-1 for Fe(CN)(6)4- reversibly shifted to 2116 cm-1 upon oxidation to Fe(CN)(6)3-, as expected. Difference IR spectra (oxidized minus reduced) were also recorded for 20 mM ferrocene in 0.1 M TBABF4/CH3CN. A shift of the C-H bending mode of the cyclopentadienyl ring from 823 to 857 cm-1 occurred upon oxidation of ferrocene to ferricenium. The key finding from the work is that the diamond OTE provides sensitive, reproducible, and stable spectroelectrochemical responses for aqueous and nonaqueous redox systems in the mid- and far-IR.