Arnab De

Targeted Delivery of Pesticides Using Biodegradable Polymeric Nanoparticles

In the current scenario the persistent challenge is to produce more food and secure the cultivated food to feed the world. The green revolution has brought tremendous increase in the worldwide crop production. Protecting the growing crop and securing the yielded gains by using pesticide has additionally helped in the production. However, the amazing performance of pesticides has encouraged their excessive use and is now causing accumulation in the environment. It has been found that the residue of pesticides can contaminate soil, water, and through crops can enter the food chain. Over the past few years there has been an increasing pressure from government and regulatory authorities to develop formulations which can have less impact on the environment and be safe for nontargeted species. In this direction, conventional formulations like granules, emulsions, and suspensions are being continuously replaced by novel formulations like microemulsions and multiple-emulsions and further by upcoming nano-formulations. Nano-formulations have the advantage that less quantity of pesticide can be used to target large area and thereby made to exert lesser impact on pesticide accumulation in the environment. Moreover, selection of biologically nontoxic ingredient for nano-formulations can additionally ensure the safety of the products.

Investigation of the Feasibility of an Amide-based Prodrug Under Physiological Conditions

Two different chemical classes of putative amide-based prodrugs of glucagon-like peptide-1 (GLP), one with an amino and the other with α hydroxyl terminal extension have been synthesized and biochemically characterized. The conversion of these terminally-extended peptide hormone analogs to a peptide of much enhanced potency through cyclization of the terminal dipeptide was studied under physiological conditions. The peptides studied demonstrated great stability and little propensity to cyclize to DKP and DMP under physiological conditions. These results stand in contrast to previous reports with model amide-based peptides and indicate that such cleavage is unlikely in larger peptides constituted by naturally coded amino acids.

Synthesis and characterization of ester‐based prodrugs of glucagon‐like peptide 1

Peptides represent a rich natural source of potential medicines with one notable pharmaceutical limitation being their relatively short duration of action. A particularly good example of this phenomenon is glucagon-like peptide 1 (GLP), a hormone of appreciable interest for the treatment of type II diabetes. In the native form, GLP demonstrates an extremely short half-life in plasma and a relatively narrow therapeutic index with gastrointestinal adverse pharmacology. We envisioned a prodrug of GLP as a means to extend the duration of action and broaden the therapeutic index of this peptide hormone. We designed, synthesized, and characterized ester-based prodrugs of GLP that differentially convert to the parent drug under physiological conditions driven by their inherent chemical instability. In a set of dipeptide extended GLP-analogs we explored the rate of diketopiperazine (DKP) and diketomorpholine (DMP) formation, and the release of the active peptide. The rate of cleavage was observed to be a function of the conformation of the dipeptide promoiety and the strength of the cyclization nucleophile. Through the careful selection of chemical functionality, a set of GLP ester prodrugs of variable half-lives has been identified.

Biginelli Reaction Catalyzed by Copper Nanoparticles

We recently reported a novel synthesis of copper nanoparticles from copper sulphate utilizing the charge-compensatory effect of ionic liquid [bmim]BF4 and ethylene glycol. The nanoparticles were characterized and found to be stable for one year. Here we hypothesize that the stabilized nanoparticles should be able to catalyze one-pot multicomponent organic reactions. We show that the nanoparticles catalyzed Biginelli reaction at room temperature to give the product 3,4-dihydopyrimidinone (>90% yield in ∼15 minutes) from aldehydes, β-diketoester (ethylacetoacetate) and urea (or thiourea). ). Remarkably, such high yields and rapid kinetics was found to be independent of the electronic density on the reactant aryl-aldehyde. This was probably because even the surface-active particles reacted faster in the presence of ionic liquid as compared to conventional methods. The heterocyclic dihydropyrimidinones (DHPMs) and their derivatives are widely used in natural and synthetic organic chemistry due to their wide spectrum of biological and therapeutic properties (resulting from their antibacterial, antiviral, antitumor and anti-inflammatory activities. Our method has an easy work-up procedure and the nanoparticles could be recycled with minimal loss of efficiency.

Synthesis and characterization of thermoresponsive copolymers for drug delivery

We report the synthesis and characterization of two nontoxic, thermogelling drug delivery systems which are liquid at room temperatures but become a gel at physiological temperature (37°C) potentially leading to release of a drug molecule. We selected temperature as the stimulus for drug release as it is physiologically invariant. A free radical polymerization of N-isopropylacrylamide (NIPAM) and N-vinylpyrrolidone (VP) was carried out under nitrogen atmosphere in double-distilled water at two different temperatures (30°C and 70°C), and the copolymers obtained were characterized by various analytical techniques. The molar ratios of the two monomers were altered with increasing NIPAM content and their cloud point temperature or least critical solution temperature (LCST) was determined. The copolymer at 9:1 ratio of NIPAM to VP resulted in the formation of nanoparticle-based gel (NG1) at 30°C; however, at 70°C, a microgel (MG1) was formed. The LCST of the nanogel and microgel was 33.5-34°C and 36.5-37°C, respectively. Thus, both the copolymers are water soluble at room temperature, but distinct phases appear at physiological temperatures. We hypothesized that these copolymers on entrapment with a drug could be used for topical application to the skin or eye for controlled drug delivery applications. Toxicological studies revealed that the copolymers are nontoxic in HeLa cells. Finally, our experiments show that a model drug [bovine serum albumin (BSA)] is released at 37°C with zero-order kinetics and confirmed using multiple well-known mathematical models.

Can molecular biology and bioinformatics be used to probe an evolutionary pathway

Williamson has proposed an interesting hypothesis regarding the evolution of caterpillars from onycophorans by hybridogenesis “as an addition to Darwins great insight into the generation of diversity ” (1). He has proposed some molecular biology-/ bioinformatics-based experiments to test his theory of hybridogenesis. Although his theory is interesting, we think that the experiments he proposes are too simplistic and will not necessarily shed much light on the topic.

Quantitative evaluation reveals taxonomic over-splitting in extinct marine invertebrates: implications in conserving biodiversity

Till date, morphology in general was characterized qualitatively to support the traditional classification system. This study for the first time uses an integrated approach to explore the appropriateness of traditional classification by superposing quantitative characters on qualitative classification using advanced mathematical techniques. Here, a quantitative method was applied that calculates changes in body shape by digitizing the inferred ecological niche and functional attributes of relevant morphological traits. Subsequently, absolute values were assigned to structural–functional traits of extinct atrypids to determine their taxonomy at a higher resolution. Investigating phenotypic diversity in these once abundant Paleozoic brachiopods from deep time is important for predicting future marine biodiversity of their closest living relatives and in conserving the marine ecosystem at large. Results show taxonomic over-splitting, a possible consequence of qualitative taxonomy. This study highlights the necessity of revisiting prior taxonomy by incorporating quantified traits and elicits the hazards of proposing classification based on qualitative traits alone. Perhaps, this study can be a starting point to improve the biological classification system in places where it must be based on morphology alone.

Perspectives on Regulatory Ubiquitination

While in vitro biochemical data has suggested multiple targets for regulatory ubiquitination, a bona fide ubiquitination target has to be ultimately substantiated by genetic complementation experiments (such as generation of knock-in mouse, where the knock-in mutation selectively impairs the process of regulatory ubiquitination). The knock-in mouse that we have generated selectively abrogates the deubiquitinase function of A20 in vivo. These mice display normal NF-κB activation without showing any inflammatory phenotype. Our results clearly demonstrate that the well-characterized role of A20 in limiting inflammatory responses is due to effects other than deubiquitination of K63-ubiquitin chains. This is the concluding chapter which reiterates our finding that the “the deubiquitinase activity of A20 is dispensable for its role in NF-κB signaling” and provides a perspective on regulatory ubiquitination. As A20 clearly has an important role in many diseases, understanding the true molecular function of A20 remains an important and worthwhile goal for the future.

Regulation of NF-κB Signaling by Regulatory Ubiquitination: Specific Pathways and A20

Upregulation of NF-κB proceeds through the inducible phosphorylation and resulting activation of the IκB kinase (IKK) complex. However 16 years after the IKK complex was first characterized, and in spite of the large volume of publications, it is still not completely clear how IKK is activated. Over the past decade, an increasing body of mostly in vitro data suggests a role for regulatory (K63-linked) polyubiquitination in IKK activation. The first part of this chapter critically examines the literature for the evidence of regulatory ubiquitination in different NF-κB pathways. Activation of NF-κB by regulatory ubiquitination has been proposed to be balanced by deubiquitinases which cleave the regulatory ubiquitin chains, thereby downregulating NF-κB activation. The second part of the chapter therefore takes a look at these deubiquitinases, focusing on a specific deubiquitinase called A20, which has been shown to be critical in downregulating NF-κB-mediated inflammation.

The Deubiquitinase Activity of A20 Is Dispensable for Its Role in NF-κB Signaling

Ubiquitination of multiple signaling adaptor molecules by K63-linked ubiquitin chains have been proposed to be a key regulatory mechanism in NF-κB activation. Deubiquitinase enzymes such as A20 have been suggested to limit the persistence of NF-κB activation by removing regulatory ubiquitin chains from ubiquitinated substrates. A20 has garnered significant interest as mice lacking A20 die prematurely from multiorgan inflammation and cachexia, as a result of increased NF-κB signaling. Thus, it is evident that A20 is nonredundant in its ability to limit the persistence of NF-κB signaling. To understand the physiological relevance of A20-mediated deubiquitination, we generated knock-in mice that lack the deubiquitinating function of A20 (A20-OTU mice). We hypothesized that these mice would have an inflammatory phenotype because of increased, persistent NF-κB signaling. However our results show that A20 OUT mice display normal NF-κB activation and no inflammatory phenotype, thereby demonstrating that the deubiquitinase activity of A20 is dispensable for normal NF-κB signaling.