Synthesis and biocompatibility evaluation of partially fluorinated pyridinium bromides

Although cationic surfactants are of general interest for a variety of consumer and biomedical applications, only a limited number of partially fluorinated, single-tailed, cationic surfactants have been synthesized. To study the potential usefulness of fluorinated cationic surfactants for these applications we synthesized a series of partially fluorinated pyridinium bromide surfactants. Three 10-perfluoroalkyldecyl pyridinium surfactants were synthesized by coupling a perfluoroalkyl iodide with 9-decene-1-yl acetate using an AIBN mediated radical reaction. The resulting 9-iodo-10-perfluoroalkyldec-1- yl acetates were deiodinated using HI-Zn-EtOH and hydrolyzed using KOH-EtOH to yield the corresponding 10-perfluoroalkyldecanol. The partially fluorinated alcohol was converted into the bromide using Br₂-PPh₃. Alkylation of excess pyridine with the bromides gave the desired 10-perfluoroalkyldecyl pyridinium bromides in good yields. Three 10-perfluoroalkylundecyl surfactants were synthesized using a similar approach with 10-undecenoic acid methyl ester as starting material. Based on an initial in vitro toxicity assessment, the toxicity of the partially fluorinated pyridinium surfactants was slightly lower or comparable to benzalkonium chloride, a typically cationic surfactant (with IC₅₀s of tested compounds ranging from 5 to 15 μM). An increase in the length and/or the degree of fluorination of the hydrophobic tail correlated with a mild decrease of cytotoxicity and haemolytic activity. Partially fluorinated pyridinium surfactants may, therefore, be useful for biomedical applications such as components for novel gene and drug delivery systems.