New Family of Water-Soluble Sulfo-Fluoro Polyphosphazenes and Their Assembly within Hemocompatible Nanocoatings

In this work, novel sulfo-fluoro polyphosphazenes (PPzs) were synthesized via macromolecular substitution of polydichlorophosphazene utilizing "non-covalent protection" methodology by converting acid functionalities into hydrophobic alkylammonium salts. Resulting PPzs showed excellent solubility in aqueous solutions over a broad pH range and contained similar to 25% sulfo-groups and 20% either trifluoroethoxy(FESP) or trifluoromethylphenoxy-(FPSP) side groups, as determined by NMR spectroscopy. Their polyelectrolyte behavior was evaluated by binding with an oppositely charged polyion, branched polyethylenimine (PEI), which resulted in the formation of interpolymer complexes as shown by dynamic light scattering (DLS). Contrary to a sulfonated, nonfluorinated PPz homopolymer (SP), fluorinated macromolecules effectively bound human serum albumin (HSA) as revealed by dynamic light scattering and asymmetric flow field flow fractionation (AF4) studies. Moreover, FESP and FPSP both displayed low hemolytic activity as evaluated in solution using porcine red blood cells. Using the layer-by-layer (LbL) technique, FESP and FPSP were assembled into nanocoatings with PEI. Both fluorinated and nonfluorinated sulfo PPzs showed linear growth with PEI because of strong ionic pairing between sulfo and amino groups. However, films of fluorinated PPzs displayed higher hydrophobicity, lower swelling, and improved stability in high ionic strength environment when compared to coatings formed by a sulfonated, nonfluorinated SP, or a carbon-chain polymer poly(styrene sulfonic acid). Hemocompatibility of FESP and FPSP nanofilms was demonstrated in vitro using whole rabbit blood hemolysis tests, which showed less than 1% hemolysis. Altogether, the present study introduces a new class of hemocompatible, sulfo-fluoropolymers that shows promise for life science applications.