Sovan Lal Banerjee

Biofunctionalized surface-modified silver nanoparticles for gene delivery

Silver nanoparticles (AgNPs) find use in different biomedical applications including wound healing and cancer. We propose that the efficacy of the nanoparticles can be further augmented by using these particles for gene delivery applications. The objective of this work was to engineer biofunctionalized stable AgNPs with good DNA binding ability for efficient transfection and minimal toxicity. Herein, we report on the one-pot facile green synthesis of polyethylene glycol (PEG) stabilized chitosan-g-polyacrylamide modified AgNPs. The size of the PEG stabilized AgNPs was 38 ± 4 nm with a tighter size distribution compared to the unstabilized nanoparticles which showed bimodal distribution of particle sizes of 68 ± 5 nm and 7 ± 4 nm. To enhance the efficiency of gene transfection, the Arg-Gly-Asp-Ser (RGDS) peptide was immobilized on the silver nanoparticles. The transfection efficiency of AgNPs increased significantly after immobilization of the RGDS peptide reaching up to 42 ± 4% and 30 ± 3% in HeLa and A549 cells, respectively, and significantly higher than 34 ± 3% and 23 ± 2%, respectively, with the use of polyethyleneimine (25 kDa). These nanoparticles were found to induce minimal cellular toxicity. Differences in cellular uptake mechanisms with RGDS immobilization resulting in improved efficiency are elucidated. This study presents biofunctionalized AgNPs for potential use as efficient nonviral carriers for gene delivery with minimal cytotoxicity toward augmenting the therapeutic efficacy of AgNPs used in different biomedical products.

Removal of Anionic Dye in Acid Solution by Self Crosslinked Insoluble Dendronized Chitosan

Insoluble Dendronized Chitosan (DCTS) was prepared to improve the adsorption capacity of chitosan (CTS) as well as to lower its solubility at lower pH for efficient removal of acid dye, Acid Blue 9 (AB 9) from aqueous solutions. Dendronized chitosan was prepared by grafting ‘dendrimer-like’ Polyamidoamine (PAMAM) onto CTS surface using Michael addition reaction followed by amidation reaction. The obtained CTS derivative became insoluble at any pH medium due to self inter- and intra-molecular cross linking during the reaction without any external crosslinker. The adsorption capacity of the CTS derivative was studied using batch method with respect to various parameters like, initial pH of the dye solution, initial dye concentration, adsorption temperature and adsorption time. The batch study showed that the adsorption capacity of CTS derivative increased many times than that of chitosan. From the adsorption kinetic study, it was found that the adsorption of dye molecule on the adsorbent surface obeyed pseudosecond- order kinetic instead of generally reported pseudo-first-order kinetic. Dsorbent surface obeyed pseudo-second-order kinetic instead of generally reported pseudo-first-order kinetic. The adsorption equilibrium showed that the Langmuir equation represented best fit of the experimental data than that of Freundlich equation. The desorbed DCTS could be reused for the adsorption of the acid dyes. The results in this study showed that DCTS may be an attractive candidate for removing anionic dyes from the wastewater.

Engineered elastomeric bio-nanocomposites from linseed oil/organoclay tailored for vibration damping

This study deals with the preparation and characterization of elastomeric nanocomposites from renewable resources for vibration damping applications. The nanocomposites were synthesized by in situ cationic polymerization technique in the presence of organophilic montmorillonite (modified nanoclay) filler. The clay filled nanocomposites showed superior dynamic moduli in comparison with the pure elastomers. The storage modulus at room temperature (25 °C) was improved by 1.56 to 2 times with respect to pure elastomers with an increase in the filler content from 1 to 4 %. A good and stable vibration damping is observed in a wide temperature and frequency region (1–50 Hz). The loss factor, tan δmax obtained from dynamic mechanical analysis varies from 0.58 to 0.87. Under laboratory fabricated testing systems, the transient attenuation with the complete decay of applied vibration within nanocomposites demonstrates that the elastomeric nanocomposites have potential as effective damping materials.

Modified chitosan encapsulated core-shell Ag Nps for superior antimicrobial and anticancer activity.

This investigation reports a one pot synthesis of silver nanoparticles (Ag Nps) using aqueous solution of chitosan-graft-poly(acrylamide) (Cts-g-PAAm) as a reducing agent and polyethylene glycol (PEG) as a stabilizing agent. The as synthesized Ag Nps was characterized by ultra violet-visible (UV-vis), Fourier transform infrared (FTIR) and X-ray diffraction (XRD) analysis. Field emission scanning electron microscopy (FESEM), dynamic light scattering (DLS) and transmission electron microscopy (TEM) showed that Ag Nps, which were stable upto more than 60 days, were spherical in shape and the particle size was in the range of 5-50 nm. Atomic force microscopy (AFM) image also supported the above obtained result. The prepared Ag Nps exhibited strong antimicrobial activity against different gram positive bacteria (Alkaliphilus, Bascillus substillis, Lysinibascillus) and gram negative bacteria (Enterobacter aerogenus, Vivbrio vulnificus and Escherichia coli) and haemolytic assay revealed its blood compatible nature. The synthesized Ag Nps showed significant cytotoxicity over human cervical HeLa cancer cells and it was found that the inhibitory concentration for 50% cell death (IC50) was 8 μg/ml.

Synthesis of a self-healable and pH responsive hydrogel based on an ionic polymer/clay nanocomposite

This investigation reports the preparation of a pH responsive self-healing nanocomposite hydrogel based on the in situ polymerization of 2-(acryloyloxy)ethyl trimethylammonium chloride and acrylic acid using N,N′-methylenebisacrylamide as a crosslinker and ammonium persulfate (APS) as a thermal initiator in the presence of soluble starch and organically modified montmorillonite (OMMT). The hydrogel was characterized using FTIR, SEM and TEM analyses. The influence of different parameters in swelling was investigated. The self-healing ability of the hydrogel was measured in different pH media and it was observed that it can show self-healing ability in physiological pH (pH = 7.4), in acidic pH (pH = 1.2) and in saline solution. This developed hydrogel showed excellent swelling ratio, mechanical strength, and elasticity. The hydrogel exhibited modulus values (G′, G′′) in the range of 102 Pa.

Fabrication and characterization of in situ graphene oxide reinforced high-performance shape memory polymeric nanocomposites from vegetable oil

Polymeric nanocomposites have been fabricated via in situ cationic polymerization of linseed oil in the presence of surface-modified graphene oxide (SGO). The interfacial interactions between SGO nanoplatelets and the polymer matrix were investigated by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), which revealed a uniform distribution of SGO throughout the polymer matrix at a lower concentration (<2 wt%), but that higher loading of SGO (2 wt%) results in agglomeration. Nanomechanical characterization revealed the enhancement of the mechanical properties of nanocomposites at low concentrations of nanofillers (<2 wt%). Under dynamic mechanical analysis, the nanocomposites exhibited superior dynamic modulus with respect to the polymer matrix, demonstrating the great reinforcement potential of SGO nanofillers. Also, the thermal stabilities of the nanocomposites effectively improved with an increase in the filler loading. In shape memory tests, the nanocomposites fully recovered their original shape under different stimuli, and the fast shape recovery was observed with an increase in the content of SGO nano fillers.

Organically modified clay supported chitosan/hydroxyapatite-zinc oxide nanocomposites with enhanced mechanical and biological properties for the application in bone tissue engineering

The objective of this study is to design biomimetic organically modified montmorillonite clay (OMMT) supported chitosan/hydroxyapatite-zinc oxide (CTS/HAP-ZnO) nanocomposites (ZnCMH I-III) with improved mechanical and biological properties compared to previously reported CTS/OMMT/HAP composite. Fourier transform infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy and transmission electron microscopy were used to analyze the composition and surface morphology of the prepared nanocomposites. Strong antibacterial properties against both Gram-positive and Gram-negative bacterial strains were established for ZnCMH I-III. pH and blood compatibility study revealed that ZnCMH I-III should be nontoxic to the human body. Cytocompatibility of these nanocomposites with human osteoblastic MG-63 cells was also established. Experimental findings suggest that addition of 5wt% of OMMT into CTS/HAP-ZnO (ZnCMH I) gives the best mechanical strength and water absorption capacity. Addition of 0.1wt% of ZnO nanoparticles into CTS-OMMT-HAP significantly enhanced the tensile strengths of ZnCMH I-III compared to previously reported CTS-OMMT-HAP composite. In absence of OMMT, control sample (ZnCH) also showed reduced tensile strength, antibacterial effect and cytocompatibility with osteoblastic cell compared to ZnCMH I. Considering all of the above-mentioned studies, it can be proposed that ZnCMH I nanocomposite has a great potential to be applied in bone tissue engineering.

A self-healable fluorescence active hydrogel based on ionic block copolymers prepared via ring opening polymerization and xanthate mediated RAFT polymerization

In this work we report a facile method to prepare a fluorescence active self-healable hydrogel via incorporation of fluorescence responsive ionic block copolymers (BCPs). Ionic block copolymers were prepared via a combined effect of ring opening polymerization (ROP) of e-caprolactone and xanthate mediated reversible addition–fragmentation chain transfer (RAFT) polymerization. Here polycaprolactone (PCL) was modified with xanthate to prepare a PCL based macro-RAFT agent and then it was utilized to prepare block copolymers with cationic poly(2-(methacryloyloxy)ethyltrimethyl ammonium chloride) (PCL-b-PMTAC) and anionic poly(sodium 4-vinylbenzenesulfonate) (PCL-b-PSS). During the block formation, the cationic segments were randomly copolymerized with a trace amount of fluorescein O-acrylate (FA) (acceptor) whereas the anionic segments were randomly copolymerized with a trace amount of 9-anthryl methylmethacrylate (AMMA) (donor) to make both the segments fluorescent. The block copolymers form micelles in a DMF : water mixture (1 : 4 volume ratio). The ionic interaction of two BCPs was monitored via Forster resonance energy transfer (FRET) and zeta potential measurements. The oppositely charged BCPs were incorporated into a polyacrylamide (PAAm) based hydrogel that demonstrated self-healing behavior and is also highly fluorescent.