In this study, diselenide (Se–Se) and disulfide (S–S) redox-responsive core-cross-linked (CCL) micelles were synthesized using poly(ethylene oxide)_2k-b-poly(furfuryl methacrylate)_1.5k (PEO_2k-b-PFMA_1.5k), and their redox sensitivity was compared. A single electron transfer-living radical polymerization technique was used to prepare PEO_2k-b-PFMA_1.5k from FMA monomers and PEO_2k-Br initiators. An anti-cancer drug, doxorubicin (DOX), was incorporated into PFMA hydrophobic parts of the polymeric micelles, which were then cross-linked with maleimide cross-linkers, 1,6-bis(maleimide) hexane, dithiobis(maleimido) ethane and diselenobis(maleimido) ethane via Diels–Alder reaction. Under physiological conditions, the structural stability of both S–S and Se–Se CCL micelles was maintained; however, treatments with 10 mM GSH induced redox-responsive de-cross-linking of S–S and Se–Se bonds. In contrast, the S–S bond was intact in the presence of 100 mM H₂O_2, while the Se–Se bond underwent de-crosslinking upon the treatment. DLS studies revealed that the size and PDI of (PEO_2k-b-PFMA_1.5k-Se)₂ micelles varied more significantly in response to changes in the redox environment than (PEO_2k-b-PFMA_1.5k-S)₂ micelles. In vitro release studies showed that the developed micelles had a lower drug release rate at pH 7.4, whereas a higher release was observed at pH 5.0 (tumor environment). The micelles were non-toxic against HEK-293 normal cells, which revealed that they could be safe for use. Nevertheless, DOX-loaded S–S/Se–Se CCL micelles exhibited potent cytotoxicity against BT-20 cancer cells. Based on these results, the (PEO_2k-b-PFMA_1.5k-Se)₂ micelles can be more sensitive drug carriers than (PEO_2k-b-PFMA_1.5k-S)₂ micelles.

Poly(N-vinyl pyrrolidone) (PNVP)-grafted graphene oxide (GO) (GO-PNVP) has been synthesized using a GO-based macro-RAFT agent prepared via click reaction of alkyne-terminated RAFT agent (S)-2-(propynyl propionate)-(o-ethyl xanthate) and azide-functionalized GO (GO-N₃). FTIR, XPS, Raman, TGA and DSC studies confirmed its formation. Silver nanoparticles are then immobilized on GO-PNVP and GO via in situ reduction of silver nitrate in the presence and absence of glucose at 40 and 95 °C, respectively. FT-IR, UV-Vis, XRD, SEM and TGA studies supported the incorporation of silver (Ag) nanoparticles. Ag nanoparticles immobilized on GO-PNVP are small, spherical and narrowly distributed (homogenous, monodisperse) compared to GO. These nanocomposites are explored as catalysts for the reduction of p-nitrophenol into p-aminophenol and also as antibacterial agents towards Gram(+) S. aureus and Gram(−) E. coli bacteria. Ag nanoparticle immobilized GO-PNVP showed efficient catalytic activity and excellent reusability along with an excellent antibacterial activity. Hence, grafting of PNVP enhances the catalytic and antibacterial properties of GO.

Tadpole-shaped β-cyclodextrin-tagged poly(N-vinylpyrrolidone) (β-CD-PNVP) has been synthesised via the click reaction of alkyne-terminated PNVP and azide-functionalized β-CD. The formed polymer is characterized by ¹H NMR, FTIR, and TGA study. The complexing ability of such a polymer with phenolphthalein is considerably lower with respect to that with β-CD alone. Doxorubicin (DOX)-loaded β-CD-PNVP (DOX-β-CD-PNVP) exhibits higher tumoricidal activity against a panel of tumor cell lines derived from sarcoma (U2-OS) and carcinomas (MCF-7 and HEPG2), causing significant lysis of tumor cells compared to free DOX. The formulation also demonstrates significantly higher uptake by the tumor cells and enhances apoptosis compared to free DOX.