A biodegradable electrical bioconductor made of polypyrrole nanoparticle/poly(D,L‐lactide) composite: A preliminary in vitro biostability study

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Abstract
The electrical stability of a novel polypyrrole (PPy)/poly(D,L-lactide) (PDLLA) composite was studied in vitro and compared with that of PPy-coated polyester fabrics. Specimens were incubated in Ringer's solution at 37°C for up to 8 weeks with or without the circulation of DC current under a constant 100 mV voltage. In situ current variation with incubation time was recorded. The AC volume electrical conductivity of the specimens before and after incubation in phosphate-buffered saline was recorded using a frequency analyzer. Water absorption and weight loss were monitored metrologically. Changes in the oxidation state of incubated PPy were analyzed with X-ray photoelectron spectroscopy. The morphological changes were observed with scanning electron microscopy, and the glass transition temperature of the PDLLA was investigated using differential scanning calorimetry. The PPy/PDLLA composite in Ringer's solution sustained a relatively stable conductivity up to 8 weeks after an initial period of “conditioning.” The PPy-coated fabrics experienced a rapid loss of conductivity when subjected to electrical circulation and regained part of it when disconnected. The volume conductivity of the nonincubated PPy/PDLLA membrane behaved as a typical conductor in the low-frequency range. The mechanisms involved in the various electrical behaviours of the PPy/PDLLA composite and PPy-coated fabrics are discussed. In conclusion, the PPy/PDLLA composite was able to deliver a biologically significant electrical current in a simulated biological solution for up to 8 weeks and therefore may be considered as a first-generation synthetic biodegradable bioconductor. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 738–746, 2003