Tissue Reactions to Polypyrrole‐Coated Polyesters: A Magnetic Resonance Relaxometry Study

Abstract

The electrically conductive properties of polypyrrole (PPy) as a coating on polyester material are very attractive for the manufacture of small diameter blood conduits. However, before these PPy-coated materials can be investigated for their capacity to generate endothelialized luminal surfaces, they must first be studied for their innocuousness in a living environment. The specific goal of the present study was to investigate the in vivo interactions of PPy-coated and noncoated woven polyester materials implanted subcutaneously in rats for prescheduled periods of 2, 5, 10, 20, and 30 days. The in vivo magnetic resonance (MR) relaxation times were computed for a small area of muscle tissue adjacent to the implants. A correlation was concurrently attempted with blood monocyte activation studies as well as histological observations of the tissue-material interface. The progressive pattern of the slower transversal relaxation time (T2s) values revealed a more persistent tissue reaction for the most conductive PPy-coated materials and a shorter acute tissue response as the surface resistivity increased. Similarly, the blood monocyte activation studies indicated that the thickness of the PPy coating, which correlated with the conductivity, was directly related to tissue response. Furthermore, both the MR and biological studies showed that the PPy-coated material with a high surface resistivity displayed the lowest tissue reaction over the entire period of implantation. The results obtained from the blood monocyte activation studies and histological observations correlate well with the noninvasive MR measurements of the body's healing process. The conductive materials with high surface resistivities must be further investigated. Finally, the noninvasive nature of MR relaxometry reveals its outstanding potential for future in vivo investigations of the body's tissue interactions with polymers and nonferromagnetic biomaterials.

Fabrication and biocompatibility of polypyrrole implants suitable for neural prosthetics

“…A unique subset of these materials, conducting polymers, has been investigated for use in biomedical applications [9][10][11]. Polypyrrole (PPy) has emerged as a promising candidate material that has been effective as a coating in both in vitro and in vivo neural studies [12][13][14]. PPy also has shown promise as a scaffold material for nerve regeneration [15].…”

Biostability of electrically conductive polyester fabrics: An in vitro study

“…7 Furthermore, PPy-coated polyester fabrics prepared through novel surface coating processes 8,9 revealed both good in vitro and in vivo biocompatibility. [10][11][12] However, the biostability of the conductive polymers, namely, the stability of the electrical conductivity and the chemical structure in a biologically relevant environment, has not been studied.…”

Foreign Body Response Investigated With an Implanted Biosensor by In Situ Electrical Impedance Spectroscopy

“…The water content of scar tissue varies as compared to healthy tissue. Alikacem et al [10] used magnetic resonance relaxometry to study tissue healing responses to coated polymer surfaces. This method cannot be used for metallic or ferromagnetic materials due to the induced currents caused by the high magnetic fields utilized.…”