«graft-from» synthesis of functionalized poly (2-ethyl-2-oxazoline), poly (2-ethyl-2-oxazoline) -b-poly (benzyl L-glutamate) nano-assembly and its block ionomer derivative for potential biomedical applications

Recent advances in the field of poly (2-oxazolines) as bio-inspired synthetic pseudopeptides have proven their potential biomedical applications such as drug delivery and tissue engineering.
In order to fabricate a biodegradable nano-assembly of poly (2-ethyl 2-oxazoline)-b-poly (benzyl L-glutamate), "graft-from" block copolymer synthesis method was used involving consecutive steps of cationic ring opening polymerization (CROP) of 2-ethyl-2-oxazoline (EOx), amine functionalization of pEOx using 1-Boc-piperazine and N-carboxyanhydride polymerization of γ-Benzyl-L-glutamate. Following hydrolysis of the protecting γ-Benzyl group, the double-hydrophilic block ionomer of pEOx-b-poly (L-glutamic acid) was prepared. The polymer samples were characterized by FTIR, 1H-NMR, size exclusion chromatography and differential scanning calorimetry (DSC). Self-assembling properties of the polymer samples in aqueous media was investigated by pyrene assay, dynamic light scattering, and transmission electron microscopy. MTT cytotoxicity assay was performed to determine the biocompatibility of pEOx-b-poly (L-glutamic acid) as a new compound in various tumor cell lines.
The polymeric nano-assembly presented a uni-modal size distribution with the mean hydrodynamic diameter of 149.8 ± 10.6 nm and critical aggregation concentration of 60 µg/mL. The molecular weight of pEOx (~ 14 kDa) increased to ~20 kDa for pEOx-b-poly (L-glutamic acid) as determined by Debye plot, indicating a successful copolymerization. MTT assay showed that little to no practical cytotoxicity was found at concentrations below 1 mg/ mL.Therefore, a soluble and biocompatible block ionomer can be formed through hydrolysis of the copolymer nano-assembly.
Both pEOx-based copolymers can be considered for various potential applications such as loading and delivery of drugs, genes, and contrast agents either by chemical conjugation or physical loading.