Injectable amphiphilic hydrogel systems from the self-assembly of partially alkylated poly(2-dimethyl aminoethyl) methacrylate with inherent antimicrobial property and sustained release behaviour

[Display omitted] •Self-assemblies of alkylated poly(dimethyl aminoethyl)methacrylate formed hydrogels.•Hydrogels modulus increased and degradation decreased as alkyl length increased.•Hydrophobic environment and encapsulation properties increased with alkyl length.•Low release at pH 7.4 and triggered release at pH 5 was achieved when alkyl is C12.•Hydrogels of C12 bearing alkyl showed good antibacterial activity and low hemolysis. Inability to encapsulate hydrophobic guest molecules and excessive water swelling by an injectable hydrogel system restrict its application in sustained delivery. Herein, we report the injectable hydrogel system with inherent antimicrobial property for sustained release of hydrophobic/hydrophilic therapeutics. The design of the injectable hydrogel system is based on in situ reaction between the self-assembly of partially alkylated poly(2-dimethyl aminoethyl) methacrylate (QPDMA) and activated halide bearing poly(ethylene glycol). The effect of degree of alkylation (Dalkylation) of PDMA and the chain length of alkyl on the antimicrobial activity, loading of hydrophobic/hydrophilic guest molecules, degradation behaviour and modulus of the resultant hydrogels have been evaluated. Hydrogel formed by the QPDMA bearing long alkyl group (C12) exhibits superior antimicrobial property, loading of hydrophobic guest molecules (pyrene loading = 1 % w/w) and modulus (22 kPa) than that when the alkyl chain length (C1-C8) is relatively shorter (pyrene loading = 0–0.6 % w/w and modulus 1–12 kPa). The C12 alkyl bearing hydrogels exhibit sustained release of hydrophobic (pyrene and prednisolone acetate) and hydrophilic (ornidazole and methotrexate) guest molecules for extended time at pH 7.4 and the triggered release at pH 5. The hydrogels formed by the self-assemblies of long-chain alkylated PDMA show promises in the biological area.