Dhruba Jyoti Sarkar

Release kinetics of controlled release formulations of thiamethoxam employing nano-ranged amphiphilic PEG and diacid based block polymers in soil

Amphiphilic copolymers, synthesized from poly(ethylene glycols) and various aliphatic and aromatic diacids, which self-assemble into nanomicellar aggregates in aqueous media, were used to develop controlled release (CR) formulations of thiamethoxam (3-(2-chloro-1,3-thiazol-5-ylmethyl)-5-methyl-1,3,5-oxadiazinan-4-ylidene(nitro)amine) using encapsulation technique Formulations were characterised by Infrared (IR) spectroscopy, Dynamic Light Scattering (DLS) and Transmission Electron Microscope (TEM). Encapsulation efficiency, loading capacity and stability after accelerated storage test of the developed formulations were checked. The kinetics of thiamethoxam, released in sandy loam soil from the different formulations was studied. Release from the commercial formulation was faster than the CR formulations. The time taken for release of 50 % of thiamethoxam ranged from 3.56 to 6.07 days for the CR formulations. Although the diffusion exponent (n value) of thiamethoxam in soil ranged from 0.532 to 0.881 in the tested formulations showing non-Fickian transport. These CR formulations may be used in safer, effective and economic crop protection.

Synthesis and Characterization of Poly (CMC-g-cl-PAam/Zeolite) Superabsorbent Composites for Controlled Delivery of Zinc Micronutrient: Swelling and Release Behavior

A series of novel superabsorbent hydrogel composites, poly(CMC-g-cl-PAam/Zeolite) (ZSAPC) were prepared by in situ graft polymerization using a cellulosic backbone, acrylamide and natural zeolite. The swelling and deswelling behavior of the prepared composites was evaluated and analyzed by different empirical models. The composite with optimum water absorption capacity were impregnated with ZnSO4 in situ during polymerization reaction. Zincated composites showed less water absorption capacity as compared to non-zincated ones. Zinc release behavior of zincated test hydrogel composites was studied in water and soil. All the test compositions exhibited non-Fickian or anomalous transport (0.43 < n < 0.84) and behaved as slow release products. GRAPHICAL ABSTRACT

Synthesis and Characterization of Amphiphilic PEG Based Aliphatic and Aromatic Polymers and their Self-Assembling Behavior

Twelve amphiphilic polymers were synthesized using poly(ethylene glycols) (PEGs) of different molecular weights, viz. 1000, 2000 and 4000 as hydrophilic block and linkers namely azelaic acid, sebacic acid, dimethyl isophthalate acid and dimethyl terephthalate as hydrophobic block in the presence of catalyst Conc. H2SO4. Synthesized polymers were characterized by using 1H-NMR, 13C-NMR and IR spectroscopy. Micellar sizes of the polymers were determined using Dynamic Light Scattering (DLS) which ranged from 51.6–174 nm for aliphatic polymers and 135.5–371 nm for aromatic polymers. Transmission Electron Microscope (TEM) results confirm the findings of DLS. Critical Micelle Concentrations (CMC) of the synthesized polymers were determined using electrical conductivity meter which ranged from 95 to 130 mg L−1 for aliphatic polymers and 420–1500 mg L−1 for aromatic polymers.

Base triggered release of insecticide from bentonite reinforced citric acid crosslinked carboxymethyl cellulose hydrogel composites

Biopolymeric clay hydrogels composites, synthesized from crosslinking of carboxymethyl cellulose with citric acid in the presence of bentonite, were used to develop base triggered release formulations (TRFs) of thiamethoxam (3-(2-chloro-1,3-thiazol-5-ylmethyl)-5-methyl-1,3,5-oxadiazinan-4-ylidene(nitro)amine) through an ex-situ encapsulation technique. Hydrogels, hydrogel-bentonite composites and their formulations were characterized by 1H NMR, IR spectroscopy, XRD, and SEM-EDS. Triggered release of thiamethoxam from the developed formulations was studied in water (pH 7-11) with the help of HPLC and subjected to kinetics analysis using different models. The kinetics study showed the release from developed TRFs followed Gallagher-Corrigan equation with an immediate burst release phenomena and higher release rate of thiamethoxam was observed at alkaline pH than neutral condition (pH 7.0). These TRFs of thiamethoxam may be useful for the efficient control of insects which are having alkaline pH in their gut.

Release behavior and bioefficacy of imazethapyr formulations based on biopolymeric hydrogels

ABSTRACT Controlled release formulations of imazethapyr herbicide have been developed employing guar gum-g-cl-polyacrylate/bentonite clay hydrogel composite (GG-HG) and guar gum-g-cl-PNIPAm nano hydrogel (GG-NHG) as carriers, to assess the suitability of biopolymeric hydrogels as controlled herbicide release devices. The kinetics of imazethapyr release from the developed formulations was studied in water and it revealed that the developed formulations of imazethapyr behaved as slow release formulations as compared to commercial formulation. The calculated diffusion exponent (n) values showed that Fickian diffusion was the predominant mechanism of imazethapyr release from the developed formulations. Time for release of half of the loaded imazethapyr (t1/2) ranged between 0.06 and 4.8 days in case of GG-NHG and 4.4 and 12.6 days for the GG-HG formulations. Weed control index (WCI) of GG-HG and GG-NHG formulations was similar to that of the commercial formulation and the herbicidal effect was observed for relatively longer period. Guar gum-based biopolymeric hydrogels in both macro and nano particle size range can serve as potential carriers in developing slow release herbicide formulations.

pH-triggered Release of Boron and Thiamethoxam from Boric Acid Crosslinked Carboxymethyl Cellulose Hydrogel Based Formulations

ABSTRACT Boric acid crosslinked carboxymethyl cellulose hydrogels were synthesized to develop pH-triggered release formulations (pH-TRFs) of boron and thiamethoxam. The developed hydrogels showed pH sensitive water absorption capacity (16.75 to 110.80 g/g xerogel). Entrapment of thiamethoxam was done through an ex-situ loading technique. The boron and thiamethoxam release was studied in pH buffer solutions (4.0, 7.0 and 9.2). Release kinetics analysis using mathematical models showed fast release in high pH solution as compared to acidic pH. These pH-TRFs may find usefulness in selective release of nutrients and pesticides in plant rhizospheric zone of problem soils viz. acidic soils and alkaline soils. GRAPHICAL ABSTRACT

Evaluation of fipronil nanoformulations for effective management of brown plant hopper (Nilaparvata lugens) in rice

ABSTRACT In this paper, we report the development, characterization and bioefficacy evaluation of fipronil nanoformulations against brown plant hopper (BPH); Nilaparvata lugens in rice. Nanoformulations were characterized for nanosizing and stability under variable conditions. Bioefficacy of nanoformulations were evaluated under field condition at farms of Indian Agricultural Research Institute, New Delhi during Kharif 2015. At milking stage BPH populations were above economic threshold level; followed by foliar application of fipronil nanoformulations at four doses (viz., 30, 45, 60 and 90 g a.i./ha) along with commercial formulation of fipronil. The mean mortality clearly indicated that all the insecticidal treatments were significantly superior over untreated control where, highest mortalities were observed in nanodispersions followed by monolithic dispersion and commercial formulation of fipronil. Treated plots 7 days after application @ 60 g a.i./ha has shown 93.47%, 86.89% and 80.47% reduction BPH population in nanodispersion, encapsulated monolithic dispersion and commercial formulation treated plots respectively. In comparison to commercial formulation @ 60 g a.i./ha yield has increased by 0.56 t ha−1 (28.76%) and 0.26 t ha−1 (14.04%) in nanodispersion and monolithic dispersion.

Insecticidal effect of citronella and neem oil Nanoemulsions against Spodoptera litura (Fab)

In order to develop innovative botanical formulations, nanoemulsion formulations of oils (neem oil & citronella oil) mixture were developed and their physiochemical properties were studied. The size of the nanoemulsions was found to be in the range of 11.23 to 17.80 nm using Dynamic Light Scattering analysis and confirmed by Transmission Electron Microscopy. The nanoemulsions were found to be stable as per CIPAC guidelines (MT 36.1). The nanoemulsion formulations were evaluated for their larvicidal and growth regulatory activities against 3rd instars of Spodoptera litura laboratory conditions. Results showed that increased concentration of citronella oil in the nanoemulsion resulted in enhanced larval mortality. The nanoemulsions, NNE-8 with 4.0% citronella oil showed highest larval mortality (80.0%) as compared to only neem oil nanoemulsion. Also, insect growth regulatory activity was found high with increase in concentration of citronella oil till 4.0%, thereafter no significant difference was observed.