Polypyrrole biocompatibility

Due to the inherent conductivity and electroactivity of conducting polymers, they act as suitable substrates for the in vitro stucfy of excitable cells, including skeletal muscle cells. Biocompatible conducting polymers, such as polypyrrole, polyaniline, and PEDOT, have been used as substrates for the culture of a range of cell types, including PC12 cells, endothelial cells, fibroblasts, and keratinoqftes. 

A microfluidic sensing application has been reported by Ghodssi and coworkers [151], who electro-deposited chitosan, a biopolymer, on polypyrrole tracks. Polypyrrole was specifically chosen because of its biocompatibility. The chitosan was functionalized to bind with various biomolecules. 

Aoki T, Tanino M, Sanui K, Ogata N, Kumakura K, Okano T, et al. Culture of mammalian cells on polypyrrole-coated TTO as a biocompatible electrode. Synth Met 1995 71. 

Disks of PLGA-laminated polypyrrole thick (2-4 pm) films have been evaluated for their in vivo biocompatibility in rat models with excellent results. Tubular guidance channels fabricated from laminated polypyrrole films have been utilized successfully to bridge a 10-mm. sciatic nerve gap in rat models [52]. These studies have demonstrated the potential of polypyrrole scaffold in particular and electroactive polymers in general in stimulated tissue regeneration. 

Polymers that, to date, have been investigated for their electrical conducting properties include polypyrrole, polyaniline, polythiophene, and polymer nanotube composites. The advantages of conducting polymers include good conductivity, biocompatibility, good stability, low impedance ability to entrap molecules, efficient charge transfer, and ability to entrap biomolecules. 

The biocompatibility of polypyrrole has been assessed in vitro and in vivo as an effective guidance channel for the regeneration of nervous tissue and as a method of conducting current to enhance the repair of a nerve [115], A PPy coating of 25 ttm was electrochemically deposited on a platinum wire. In vitro, the cell responses from L929 mouse fibroblast and neuro2a neuroblastoma cells to the polymer coatings were evaluated under a constant current. The results indicated that the polypyrrole was cytocompatible in vitro if prepared by appropriate extraction techniques. After polymerization, extraction in methanol for a period of 1 week was carried out to remove residual electrolyte. Some evidence of toxicity was evident when a current of 1 mA was applied across the polymer for periods up to 96 h. In vivo results show there was only minimal response from tissue after 4 weeks of implantation in a rat model. 

George PM, Lyckman AW, La Van DA et al (2005) Fabrication and biocompatibility of polypyrrole implants suitable for neural prosthetics. Biomaterials 26 3511-3519 Adhikari B, Majumdar S (2004) Polymers in sensor applications. Prog Polym Sci 29 699-766... 

Polyanitine was the first CP polymer, which was described in the mid-19th century by Henry Letheby [36]. Since then numerous intrinsically CP have been developed, among others polyacetylene, polythiophene, polypyrrole. CPs, also referred to as synthetic metals, have found applications in many fields. They are integrated for example in solar cells, rechargeable batteries and biomedical devices [37]. CPs are also very attractive for biosensors. In biosensors, CP can be used as excellent non-metallic electrodes. Numerous biosensors have been developed over the past 20 years with electrodes made of CP. The fabrication is fairly easy and flexible. This allows the biosensors to be single-use system avoiding any risk of contamination and adaptation of the biosensors to new targets can be rapidly made. They are mostly biocompatible, can easily be synthesized and can be modified for immobilization of bioelements [38]. These conductive polymers are referred to as intrinsic conductive polymers in comparison to extrinsic conductive polymers that are a polymer matrix in which some metal particles have been entrapped [39]. 

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