Kamalesh Prasad

Weak gel of chitin with ionic liquid, 1-allyl-3-methylimidazolium bromide

This paper reports the formation of weak gel of chitin with an ionic liquid, 1-allyl-3-methylimidazolium bromide (IL). When a mixture of 5% (w/w) chitin with IL was heated at 100 degrees C for 48h, the clear liquid was obtained. The experimental process was observed by the CCD camera view and the SEM analysis. From a mixture of chitin with IL in the higher concentration (7%, w/w), a more viscous material, i.e., a gel-like material was obtained. The rheological evaluations showed that both 5% (w/w) and 7% (w/w) chitins with IL behaved as weak gels.

Dissolution of α-chitin in deep eutectic solvents

Deep eutectic solvents (DESs) consisting of mixtures of choline halide (chloride/bromide)–urea, choline chloride–thiourea, chlorocholine chloride–urea and betaine hydrochloride–urea were demonstrated to be effective solvent systems for α-chitin. The dissolution of the biopolymer in the DESs was carried out by conventional heating, heating under microwave irradiation and heating assisted by ultrasonication under an inert atmosphere. Microwave and ultrasonication helped to reduce the time and temperature required for dissolution. Maximum dissolution of the biopolymer (9% w/w) was observed in the DES consisting of choline chloride–thiourea. The absence of insoluble particles in the solutions was confirmed by optical light microscope. No remarkable degradation of chitin during the dissolution process was observed upon investigations using FT-IR, XRD, 1H NMR, TGA, viscometry and rheology.

Detection and quantification of some plant growth regulators in a seaweed-based foliar spray employing a mass spectrometric technique sans chromatographic separation.

The sap expelled from the fresh harvest of Kappaphycus alvarezii , a red seaweed growing in tropical waters, has been reported to be a potent foliar spray. Tandem mass spectrometry of various organic extracts of the sap confirmed the presence of the plant growth regulators (PGRs) indole 3-acetic acid, gibberellin GA(3), kinetin, and zeatin. These PGRs were quantified in fresh state and after 1 year of storage by ESI-MS without recourse to chromatographic separation. Quantification was validated against HPLC data. The results may be useful in correlating with the efficacy of the sap. The methodology was extended to two other seaweeds. The method developed is convenient and precise and may find application in other agricultural formulations containing these growth hormones.

Rapid dissolution of DNA in a novel bio-based ionic liquid with long-term structural and chemical stability: successful recycling of the ionic liquid for reuse in the process

DNA from salmon testes was solubilised in two bio-based ionic liquids up to 3.5% w/w in 6 h. No structural degradation of the molecule was observed for the sample solubilised in choline-indole-3-acetate (chol-IAA). However, the molecule was found to be denatured in choline-indole-3-butyrate (chol-IBA). The structural and chemical stability of the DNA molecules after six months of storage in the former was established. Further recyclability of the ionic liquid with very high yield (90-95%) for consecutive reuse in the redissolution of DNA was demonstrated.

Profiling of cellulose content in Indian seaweed species.

Cellulose contents were estimated in 12 seaweed samples belonging to different families e.g. red, brown and green, growing in Indian waters. Each cellulose sample was fractionated to yield alpha (alpha) and beta (beta) celluloses. Characterization was done using various analytical tools and results were validated by comparison with those of the cellulose obtained from Whatman filter paper No. 4. The greatest yields of cellulose (crude), alpha- and beta-cellulose were obtained from Gelidiella acerosa (13.65%), Chamaedoris auriculata (9.0%) and G. acerosa (3.10%). G. acerosa was also found to contain relatively high amount of alpha-cellulose (8.19%). The lowest cellulose contents were recorded from Kappaphycus alvarezii (2.00%) and Sarconema scinaioides (2.1%), while the latter contained the lowest alpha-, and beta-celluloses (1.0% and 0.30%, respectively). It appears that agarophytic and alginophytic algae contain high cellulose and alpha-cellulose contents, while the carrageenophyte contains low cellulose. The brown algae, in general contain high cellulose as well as alpha- and beta-celluloses.

Deep eutectic solvents as efficient solvent system for the extraction of κ-carrageenan from Kappaphycus alvarezii.

Three different deep eutectic solvents (DESs) prepared by the complexation of choline chloride with urea, ethylene glycol and glycerol along with their hydrated counterparts were used for the selective extraction of κ-carrageenan from Kappaphycus alvarezii. Upon comparison of the quality of the polysaccharide with the one obtained using water as extraction media as well as the one extracted using widely practiced conventional method, it was found that, the physicochemical as well as rheological properties of κ-carrageenan obtained using DESs as solvents was at par to the one obtained using conventional method and was superior in quality when compared to κ-carrageenan obtained using water as solvent. Considering the tedious nature of the extraction method employed in conventional extraction process, the DESs can be considered as suitable alternative solvents for the facile extraction of the polysaccharide directly from the seaweed. However, among the hydrated and non-hydrated DESs, the hydrated ones were found to be more effective in comparison to their non-hydrated counterparts.

Preparation of temperature-induced shapeable film material from guar gum-based gel with an ionic liquid

A temperature-induced shapeable film material was prepared from guar gum-based gel with an ionic liquid, 1-butyl-3-methylimidazolium chloride, by soaking and compression techniques.

Choline chloride-thiourea, a deep eutectic solvent for the production of chitin nanofibers.

Deep eutectic solvents (DESs) consisting of the mixtures of choline halide (chloride/bromide)-urea and choline chloride-thiourea were used as solvents to prepare α-chitin nanofibers (CNFs). CNFs of diameter 20-30 nm could be obtained using the DESs comprising of the mixture of choline chloride and thiourea (CCT 1:2); however, NFs could not be obtained using the DESs having urea (CCU 1:2) as hydrogen bond donor. The physicochemical properties of thus obtained NFs were compared with those obtained using a couple of imidazolium based ionic liquids namely, 1-butyl-3-methylimidazolium hydrogen sulphate [(Bmim)HSO4] and 1-methylimidazolium hydrogen sulphate [(Hmim)HSO4] as well as choline based bio-ILs namely, choline hydrogen sulphate [(Chol)HSO4] and choline acrylate. The CNFs obtained using the DES as a solvent were used to prepare calcium alginate bio-nanocomposite gel beads having enhanced elasticity in comparison to Ca-alginate beads. The bio-nanocomposite gel beads thus obtained were used to study slow release of 5-fluorouracil, an anticancer drug.

Preparation of tamarind gum based soft ion gels having thixotropic properties

Tamarind gum was used to prepare ion gels using both synthetic ionic liquids (ILs) namely 1-butyl-3-methylimidazolium chloride and 1-butyl-3-methylimidazolium bromide and bio-based ionic liquids (Bio-ILs) namely choline acrylate, choline caproate and choline caprylate by heating cooling process. The gels were found to have good thermal stability and exhibited thixotropic behaviour. Upon relaxation after applied breaking strain, the recovery of gel structures after ten consecutive cycles was observed. The hydrogel of the gum prepared using ethanol aqueous solution had much inferior quality in terms of viscosity, viscoelasticity, thermal stability and thixotropicity when compared with the ion gels. The ion gels also showed very good adherence to human finger muscles and skin. The ion gels thus prepared may find application in electrochemistry, sensors, actuators and the gels prepared with Bio-ILs could even be useful in biomedical applications.

Microwave-induced facile synthesis of water-soluble fluorogenic alginic acid derivatives

A facile microwave-induced method was developed for synthesizing water-soluble fluorescent derivatives of alginic acid (ALG) with four different diamines, hydrazine (HY), ethylenediamine (EDA), 1,6-hexanediamine (HDA), and 1,4-cyclohexanediamine (CHDA), followed by a cross-linking reaction with a natural cross linker genipin. The ethylenediamine derivative of alginic acid (ALG-EDA) exhibited good fluorescent activity, which upon cross linking was enhanced threefold. The other amide derivatives, for example, ALG-HY, ALG-HDA, and ALG-CHDA, were not fluorescent, but their respective crosslinked products exhibited excellent fluorescent activity. The fluorescence intensity had an inverse correlation with the number of carbon atoms present in the amine, which in turn was a function of degree of substitution (DS). These fluorescent polysaccharide derivatives are of potential utility in the domain of sensor applications.