Abstract
Today, the application of polyaniline in biomedicine is widely discussed. However, information about impurities released from polyaniline and about the cytotoxicity of its precursors aniline, aniline hydrochloride, and ammonium persulfate are scarce. Therefore, cytotoxicity thresholds for the individual precursors and their combinations were determined (MTT assay) and the type of cell death caused by exposition to the precursors was identified using flow-cytometry. Tests on fibroblasts revealed higher cytotoxicity of ammonium persulfate than aniline hydrochloride. Thanks to the synergic effect, both monomers in combination enhanced their cytotoxicities compared with individual substances. Thereafter, cytotoxicity of polyaniline doped with different acids (sulfuric, nitric, phosphoric, hydrochloric, and methanesulfonic) was determined and correlated with impurities present in respective sample (HPLC). The lowest cytotoxicity showed polyaniline doped with phosphoric acid (followed by sulfuric, methanesulfonic, and nitric acid). Cytotoxicity of polyaniline was mainly attributed to the presence of residual ammonium persulfate and low-molecular-weight polar substances. This is crucial information with respect to the purification of polyaniline and production of its cytocompatible form.
Highlights
The number of studies dealing with biomedical applications of conducting polymers in general, and polyaniline in particular, notably increased during the last decade
Together with the determination of the cytotoxicity of precursors (An, aniline hydrochloride (AnH), ammonium persulfate (APS)), it provides substantial information needed for the purification of polyaniline and its modifications leading to preparation of noncytotoxic, biocompatible form of this polymer
Tests performed on fibroblast cell line NIH/3T3 revealed higher cytotoxicity of APS in comparison with An and AnH
Summary
The number of studies dealing with biomedical applications of conducting polymers in general, and polyaniline in particular, notably increased during the last decade. An understanding of the cytotoxicity of polyaniline, including the cytotoxicity of impurities leaching from the polymer, is crucial for its practical application. Polyaniline can be prepared in various forms, each differing in their chemical and physical properties. The three fundamental forms of the polymer can be synthetized [1]. The green emeraldine salt is produced directly by the oxidative polymerization. After the oxidant is consumed, it converts to the emeraldine. If placed in alkaline media, conducting emeraldine salt converts to a nonconducting emeraldine base. Of the mentioned polyaniline forms, green polyaniline salt is of particular interest with respect to medical applications. This conducting polymer can be used, Polymers 2019, 11, 362; doi:10.3390/polym11020362 www.mdpi.com/journal/polymers
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