Solution thermal properties of a family of thermo-responsive N-isopropyl acrylamide-co-N-hydroxymethyl acrylamide copolymers – Aspects intrinsic to the polymers

Dual-responsive polymer coated superparamagnetic nanoparticle for targeted drug delivery and hyperthermia treatment

In this work, we have prepared water-soluble superparamgnetic iron oxide nanoparticles (SPIONs) coated with a dual responsive polymer for targeted delivery of anticancer hydrophobic drug (curcumin) and hyperthermia treatment. Herein, superparamagnetic mixed spinel (MnFe2O4) was used as a core material (15-20 nm) and modified with carboxymethyl cellulose (water-soluble component), folic acid (tagging agent), and dual responsive polymer (poly-N isopropylacrylamide-co-poly glutamic acid) by microwave radiation. Lower critical solution temperature (LCST) of the thermoresponsive copolymer was observed to be around 40 °C, which is appropriate for drug delivery. The polymer-SPIONs show high drug loading capacity (89%) with efficient and fast drug release at the desired pH (5.5) and temperature (40 °C) conditions. Along with this, the SPIONs show a very fast increase in temperature (45 °C in 2 min) when interacting with an external magnetic field, which is an effective and appropriate temperature for the localized hyperthermia treatment of cancer cells. The cytocompatibility of the curcumin loaded SPIONs was studied by the methyl thiazol tetrazolium bromide (MTT) assay, and cells were imaged by fluorescence microscopy. To explore the targeting behavior of curcumin loaded SPIONs, a simple magnetic capturing system (simulating a blood vessel) was constructed and it was found that ∼99% of the nanoparticle accumulated around the magnet in 2 min by traveling a distance of 30 cm. Along with this, to explore an entirely different aspect of the responsive polymer, its antibacterial activity toward an E. coli strain was also studied. It was found that responsive polymer is not harmful for normal or cancer cells but shows a good antibacterial property.

Activity and stability of urease entrapped in thermosensitive poly(N-isopropylacrylamide-co-poly(ethyleneglycol)-methacrylate) hydrogel

Urease was entrapped in thermally responsive poly(N-isopropylacrylamide-co-poly(ethyleneglycol)-methacrylate), p[NIPAM-p(PEG)-MA], copolymer hydrogels. The copolymer membrane shows temperature-responsive properties similar to conventional p(NIPAM) hydrogels, which reversibly swell below and de-swell above the lower critical solution temperature of p(NIPAM) hydrogel at around 32 °C. The retained activities of the entrapped urease (in p[NIPAM-p(PEG)-MA]-4 hydrogels) were between 83 and 53% compared to that of the same quantity of free enzyme. Due to the thermo-responsive character of the hydrogel matrix, the maximum activity was achieved at around 25 °C with the immobilized urease. Optimum pH was the same for both free and entrapped enzyme. Operational, thermal and storage stabilities of the enzyme were found to increase with entrapment of urease in the thermoresponsive hydrogel matrixes. As for reusability, the immobilized urease retained 89% of its activity after ten repeated uses.