Pronob Gogoi

Biocompatible carboxymethylcellulose-g-poly(acrylic acid)/OMMT nanocomposite hydrogel for in vitro release of vitamin B12

The present work describes the preparation of a biocompatible nanocomposite hydrogel based on CMC-g-PAA and organo-MMT nanoclay by using methylene bis-acrylamide (MBA) as a cross-linker and potassium persulfate (KPS) as an initiator through radical graft polymerization. The nanocomposite hydrogels were characterized by using techniques such as FTIR, SEM and XRD analysis. The effects of various parameters on the swelling behaviour of the hydrogels were studied. The mechanical strength of the nanocomposite hydrogels was determined by dynamic mechanical analysis (DMA) and all the samples showed an increase in the storage modulus (G′) with an increase in cross-linker amount. The in vitro biocompatibility of the nanocomposite hydrogels showed that the presence of nanoclay in the nanocomposite hydrogel enhanced the in vitro blood compatibility. The vitamin B12 release mechanism has been studied during different time periods using a UV-visible spectrophotometer. The drug release kinetics revealed that release of vitamin B12 follows a non-Fickian diffusion mechanism.

Structural and physico-chemical characterization of a dirhamnolipid biosurfactant purified from Pseudomonas aeruginosa: application of crude biosurfactant in enhanced oil recovery

The present study describes the structural characterization and biotechnological application of a dirhamnolipid biosurfactant produced by Pseudomonas aeruginosa strain NBTU-01 isolated from a petroleum oil-contaminated soil sample. Characterization of partially purified biosurfactant by LC-MS/MS analysis indicated predominant production (78%) of dirhamnolipids Rha-Rha-C10-C10 and Rha-Rha-C12-C10 with a minor production of monorhamnolipids (22%). NMR analysis of the purified major biosurfactant produced by P. aeruginosa strain NBTU-01 identified it as dirhamnolipid and its deduced structure was L-rhamnosyl-L-rhamnosyl-β-hydroxydecanoyl-β-hydroxydecanoate. The LC-MS/MS analysis of intracellular proteins of P. aeruginosa strain NBTU-01 identified key enzymes and other proteins associated with regulation and biosynthesis of rhamnolipids. Critical micelle concentration of purified dirhamnolipid biosurfactant was determined at 72 ​± 2.25 mg l−1 and it reduced the surface tension of water from 72.2 to 29.5 mN m−1. The crude rhamnolipid biosurfactant effectively emulsified crude petroleum-oil, diesel, kerosene and coconut oil, and removed 70 ± 3.5% crude petroleum oil from a saturated sand pack column. Heating the crude rhamnolipid biosurfactant at 100 °C for 5 h did not affect oil recovery from the sand pack column. Moreover, rhamnolipid biosurfactant showed stability at pH values between 6.0 and 10.0. The crystallization and melting temperature of purified dirhamnolipid biosurfactant was found to be 99 and 134 °C, respectively, suggesting it can withstand thermal denaturation and is suitable for application in high temperature wells for tertiary oil recovery.

Designing Self-Healing Polymers by Atom Transfer Radical Polymerization and Click Chemistry

The development of smart self-healing polymeric materials and composites has been the subject of a tremendous amount of research over last few years. When self-healing materials are mechanically damaged, either internally (via crack formation) or externally (by scratching), they have the ability of restoring their original strength and recovering their inherent properties. For polymers to exhibit such a healing ability, they must contain some functionality which will either rebound among themselves or have the ability of coupling with other functionalities. Preparation of such multifunctional and well-defined macromolecules requires a smart selection of a controlled polymerization technique in combination with appropriate coupling reactions. Among all the polymerization techniques introduced so far, atom transfer radical polymerization (ATRP) is the most versatile owing to its exceptional properties like preparation of polymer with predetermined molecular weight, narrow polydispersity index, predetermined chain-end functionality, and tunable architecture. Click chemistry is an extremely powerful coupling approach which in combination with ATRP can be used for generation of polymers with almost all of the desired properties. In this chapter, an overview on the use of ATRP and click chemistry for polymerization of various “clickable” monomers using “clickable” ATRP initiators is provided along with other post-polymerization modification strategies that can be used to construct macromolecules with self-healing ability.