Showing papers by "Nikhil K. Singha published in 2022"

Gold Nanoparticle Embedded Stimuli-Responsive Functional Glycopolymer: A Potential Material for Synergistic Chemo-Photodynamic Therapy of Cancer Cells.

Abstract: Photodynamic therapy has emerged as a non-invasive treatment modality for several types of cancers. However, conventional hydrophobic photosensitizers (PS) suffer from low water solubility and poor tumor-targeting ability. Therefore, PS modified with glycopolymers can offer adequate water solubility, biocompatibility and tumor-targeting ability due to the presence of multiple sugar units. In this study, a well-defined block copolymer (BCP) poly(3-O-methacryloyl-D-glucopyranose)-b-poly(2-(4-formylbenzoyloxy)ethylmethacrylate) (PMAG-b-PFBEMA) containing pendant glucose and aldehyde units was synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization method. A water-soluble PS (toluidine blue O; TBO) and a potent anti-cancer drug, Doxorubicin (Dox) were introduced to the polymer backbone via acid-labile Schiff-base reaction (PMAG-b-PFBEMA_TBO_Dox). The PMAG-b-PFBEMA_TBO_Dox was then anchored on the surface of AuNP via electrostatic interaction. This hybrid system exhibited excellent reactive oxygen species (ROS) generating ability under exposure of 630 nm LED along with triggered release of Dox under the acidic pH of tumor cells. The in vitro cytotoxicity study on human breast cancer cell line, MDA MB 231, for this hybrid system showed promising results due to the synergistic effect of ROS and Dox released. Thus, this glycopolymer-based dual (chemo-photodynamic) therapy model can work as potential material for future therapeutics. This article is protected by copyright. All rights reserved.

Ultrafast Derived Self-Healable, Reprocessable Polyurethane Elastomer Based on Dynamic “Electrophilic Substitution (ES)-Click” Chemistry

Abstract: Conventional self-healable polyurethanes (PUs) based on the furan–maleimide combination take several hours to prepare and require an elevated temperature to endow self-healing characteristics via Diels–Alder (DA) chemistry. In this work, furan end-capped triarm PU prepolymers (FAPUs) were prepared using polycaprolactone triol, 4,4′-methylene bis(phenyl isocyanate) (MDI), and furfuryl alcohol in the presence of a tin(II) catalyst. Cross-linked FAPUs were accomplished within 10 s under ambient conditions after reaction with bis-1,2,4-triazoline-3,5-dione (bis-TAD) via ES-Click chemistry. Structural elucidation of the synthesized prepolymer and ES-cross-linked FAPUs was carried out by 1H NMR and FTIR analyzes. Differential scanning calorimetric (DSC) analysis revealed that TAD-derived FAPU elastomers were thermoreversible at 110 °C and room temperature via ES-Click chemistry, and the thermoreversibility of FAPUs was confirmed via solution reprocessability. The self-healing behavior of PUs was monitored under an optical microscope, by scanning electron microscopy, and by tensile measurement. Unlike pristine prepolymer with a tensile strength of σ = 0.1 N/mm2, TAD-derived FAPU1 polymer showed a significant tensile strength of σ = 34.68 N/mm2 with healing efficiency (Hσ = 83%) without using any additive. The surface microhardness and depth penetration of FAPUs improved significantly after cross-linking with bis-TAD and retained their properties even after healing. Similarly, the resultant TAD-derived PUs had improved surface hydrophobicity compared to pristine PU prepolymers as supported by AFM analysis. These ES-Click-derived PU polymer materials showed significant mechanical, good self-healing, and hydrophobic characteristics and will be potential materials for advanced coatings, adhesives, and paint applications.

Glycopolymer Decorated pH-Dependent Ratiometric Fluorescent Probe Based on Förster Resonance Energy Transfer for the Detection of Cancer Cells.

Abstract: Development of fluorescent imaging probes is an important topic of research for the early diagnosis of cancer. Based on the difference between the cellular environment of tumor cells and normal cells, several "smart" fluorescent probe has been developed. In this work, we developed a glycopolymer functionalized Förster resonance energy transfer (FRET) based fluorescent sensor, which can monitor the pH change in cellular system. One-pot sequential RAFT polymerization technique was employed to synthesize fluorescent active triblock glycopolymer that can undergo FRET change on the variation of pH. A FRET pair, fluorescein o-acrylate (FA) and 7-amino-4-methylcoumarin (AMC) was linked via a pH-responsive polymer poly [2-(diisopropylamino)ethyl methacrylate] (PDPAEMA), which can undergo reversible swelling/deswelling under acidic/neutral condition. The presence of glycopolymer segment, provided stability, water solubility and specificity towards cancer cells. The cellular FRET experiments on cancer cells (MDA MB 231) and normal cells (3T3 fibroblast cells) demonstrated that the material is capable of distinguishing cells as a function of pH change. This article is protected by copyright. All rights reserved.