Pooja Ghosh

Bioassays for toxicological risk assessment of landfill leachate: A review

Landfilling is the most common solid waste management practice. However, there exist a potential environmental risk to the surface and ground waters due to the possible leaching of contaminants from the landfill leachates. Current municipal solid waste landfill regulatory approaches consider physicochemical characterization of the leachate and do not assess their potential toxicity. However, assessment of toxic effects of the leachates using rapid, sensitive and cost-effective biological assays is more useful in assessing the risks as they measure the overall toxicity of the chemicals in the leachate. Nevertheless, more research is needed to develop an appropriate matrix of bioassays based on their sensitivity to various toxicants in order to evaluate leachate toxicity. There is a need for a multispecies approach using organisms representing different trophic levels so as to understand the potential impacts of leachate on different trophic organisms. The article reviews different bioassays available for assessing the hazard posed by landfill leachates. From the review it appears that there is a need for a multispecies approach to evaluate leachate toxicity.

Preparation of albumin based nanoparticles for delivery of fisetin and evaluation of its cytotoxic activity

Fisetin is a well known flavonoid that shows several properties such as antioxidant, antiviral and anticancer activities. Its use in the pharmaceutical field is limited due to its poor aqueous solubility which results in poor bioavailability and poor permeability. The aim of our present study is to prepare fisetin loaded human serum albumin nanoparticles to improve its bioavailability. The nanoparticles were prepared by a desolvation method and characterized by spectroscopic and microscopic techniques. The particles were smooth and spherical in nature with an average size of 220 ± 8 nm. The encapsulation efficiency was found to be 84%. The in vitro release profile showed a biphasic pattern and the release rate increases with increase in ionic strength of solution. We have also confirmed the antioxidant activity of the prepared nanoparticles by a DPPH (2,2-diphenyl-1-picrylhydrazyl) assay. Further its anticancer activity was evaluated using MCF-7 breast cancer cell lines. Our findings suggest that fisetin loaded HSA nanoparticles could be used to transfer fisetin to target areas under specific conditions and thus may find use as a delivery vehicle for the flavonoid.

Binding of naringin and naringenin with hen egg white lysozyme: A spectroscopic investigation and molecular docking study

The interactions of naringenin (NG) and naringin (NR) with Hen Egg White Lysozyme (HEWL) in aqueous medium have been investigated using UV-vis spectroscopy, steady-state fluorescence, circular dichroism (CD), Fourier Transform infrared spectroscopy (FT-IR) and molecular docking analyses. Both NG and NR can quench the intrinsic fluorescence of HEWL via static quenching mechanism. At 300K, the value of binding constant (Kb) of HEWL-NG complex (5.596±0.063×104M-1) was found to be greater than that of HEWL-NR complex (3.404±0.407×104M-1). The negative ΔG° values in cases of both the complexes specify the spontaneous binding. The binding distance between the donor (HEWL) and acceptor (NG/NR) was estimated using the Försters theory and the possibility of non-radiative energy transfer from HEWL to NG/NR was observed. The presence of metal ions (Ca2+, Cu2+ and Fe2+) decreased the binding affinity of NG/NR towards HEWL. Synchronous fluorescence studies indicate the change in Trp micro-environment due to the incorporation of NG/NR into HEWL. CD and FT-IR studies indicated that the α-helicity of the HEWL was slightly enhanced due to ligand binding. NG and NR inhibited the enzymatic activity of HEWL and exhibited their affinity for the active site of HEWL. Molecular docking studies revealed that both NG and NR bind in the close vicinity of Trp 62 and Trp 63 residues which is vital for the catalytic activity.

Characterization of non-covalent binding of 6-hydroxyflavone and 5,7-dihydroxyflavone with bovine hemoglobin: Multi-spectroscopic and molecular docking analyses

Flavonoids are biologically imperative compounds used as anti-oxidants, anti-cancer, anti-bacterial agents etc. The current work reports comprehensive binding studies of two important flavonoids, 6-hydroxyflavone and 5,7-dihydroxyflavone (chrysin) with bovine hemoglobin (BHb) at 298K and 308K, in aqueous medium using UV-vis spectroscopy, steady state fluorescence, circular dichroism (CD) measurements, Fourier Transform infrared spectroscopy (FT-IR) and molecular docking studies. Both 6-hydroxyflavone and chrysin can quench the intrinsic fluorescence intensity of BHb via static quenching mechanism. The values of binding constant (Kb) for BHb-chrysin complex (3.177±0.992×104M-1, at 298K) was found to be greater than that of BHb-6-hydroxyflavone complex (2.874±0.863×104M-1, at 298K) and the Kb values decreased with the rise in temperature. The thermodynamic parameters indicated that hydrophobic forces and H-bonding play crucial role in BHb-6-hydroxyflavone complexation whereas electrostatic interaction plays the major role in the binding of BHb and chrysin. The binding distances from donor BHb to the acceptor ligands (6-hydroxyflavone and chrysin) were estimated using the Fösters theory and the possibility of non-radiative energy transfer from BHb to 6-hydroxyflavone/chrysin was observed. The ligands, 6-hydroxyflavone and chrysin induced conformational change around Trp residues in BHb as confirmed by synchronous and 3D fluorescence results. CD and FT-IR studies indicated that the % α-helicity of BHb was enhanced due to 6-hydroxyflavone/chrysin binding. Both the flavonoids showed remarkable inhibitory effect towards BHb glycation. Hydrophobic probe (8-anilino-1-naphthalenesulfonic acid, ANS) displacement and molecular docking studies revealed that the ligands bind within the hydrophobic pocket of BHb.

Recovery of polyhydroxyalkanoates from municipal secondary wastewater sludge

In the current study, the feasibility of utilizing municipal secondary wastewater sludge for Polyhydroxyalkanoate (PHA) extraction was improved by optimization of various parameters (temperature, duration and concentration of sludge solids). Optimized process parameters resulted in PHA recovery of 0.605 g, significantly higher than un-optimized conditions. The characterization of PHA was carried out by GC-MS, FT-IR and NMR (1H and 13C) spectroscopy. The PHA profile was found to be dominated by mcl PHA (58%) along with other diverse PHA. The results of the present study show rich diversity of PHA extracted from a raw material which is readily available at minimal cost. In conclusion, exploring the potential of wastes for production of bioplastics not only reduces the cost of bioplastic production, but also provides a sustainable means for waste management.

Solubility enhancement of morin and epicatechin through encapsulation in an albumin based nanoparticulate system and their anticancer activity against the MDA-MB-468 breast cancer cell line

The polyphenols morin and epicatechin exhibit properties that include antioxidant, anticancer, and anti-inflammatory activities, etc. However, their clinical application is hampered by their poor aqueous solubility and bioavailability. In the present study an attempt has been made to overcome these drawbacks by encapsulating morin and epicatechin separately into a suitable nanocarrier. We have prepared morin loaded human serum albumin (HSA) nanoparticles (Mor-HSA-NPs) and epicatechin loaded HSA nanoparticles (EC-HSA-NPs) using a desolvation technique, which have been further characterised for particle size, morphology, morin/epicatechin content in nanoparticles, and their in vitro release. The particle size of the prepared formulation was ∼170 ± 6 nm for Mor-HSA-NPs and ∼200 ± 12 nm for EC-HSA-NPs with an almost spherical shape and smooth surface. The release profile exhibited an initial burst release followed by a sustained release. The cytotoxicity of Mor-HSA-NPs and EC-HSA-NPs against the MDA-MB-468 breast cancer cell line has been investigated by MTT assay and the results show that the nanoparticles are capable of destroying the cancer cells more potently than morin/epicatechin alone. This is also supported by fluorescence microscopy images. This result is likely to facilitate an understanding of how to enhance the delivery of flavonoids like morin and epicatechin by encapsulation.

Glycation of human serum albumin alters its binding efficacy towards the dietary polyphenols: a comparative approach.

Diabetes is a major problem in the world. The proteins became modified during glycation after reacting with the reducing sugars (e.g. D-glucose) via non-enzymatic pathways. The glycated analogue of human serum albumin (HSA) has been characterized with the help of multi-spectroscopic methods. It has been observed that six glucose molecules can bind covalently to HSA under experimental condition. The binding affinity of the modified HSA towards the dietary polyphenols has been estimated using UV–vis and fluorescence spectroscopic techniques. The binding constant values of the ligands were found to decrease after the modification of HSA. Graphical abstract The binding affinities (Kb) of the polyphenols decreased towards human serum albumin after its structural modification with D-glucose. Highest percentage decrease in the binding is observed for quercetin among all the polyphenols.

Glycation of human γB-crystallin: A biophysical investigation.

Glycation of ocular lens proteins plays a vital role in the development of diabetic cataract. In order to investigate the role of glycation in cataractogenesis, the extent of glycation of human γB-crystallin was determined by an in vitro glycation study in a solution of high glucose content for upto 28days. The glycated protein has been purified and the formation of advanced glycation end products (AGEs) has been monitored spectroscopically. Size exclusion chromatographic studies showed that the covalent intermolecular crosslinking in the dimer formed was not due to disulfide bond formation. MALDI-TOF spectroscopy was employed to determine the number of glucose moieties attached to the protein due to glycation.

Complexation With Human Serum Albumin Facilitates Sustained Release of Morin From Polylactic-Co-Glycolic Acid Nanoparticles

Understanding the interaction of proteins with nanoparticles has become an important area of research in biomedical and pharmaceutical fields. Morin is a flavonol which shows several properties including antioxidant, anticancer, and anti-inflammatory activities. However, the major limitation is its poor aqueous solubility. Therefore, morin-loaded polylactic-co-glycolic acid (PLGA) nanoparticles (MPNPs) were prepared to improve the solubility of morin. The resulting MPNPs were characterized by spectroscopic and microscopic techniques. The nanoparticles were spherical with an average size of 237 ± 17 nm. UV-visible, fluorescence, and circular dichroism (CD) spectroscopy were employed to study the interaction of the MPNPs with human serum albumin (HSA). Our study revealed that a static fluorescence quenching mechanism was involved in the interaction between HSA and MPNPs. Hydrophobic interactions also play an important role in stabilizing the HSA-MPNP complex. CD results suggest that there is an alteration of the secondary structure of HSA in the presence of MPNPs. MPNPs exhibit antioxidant properties which are supported by the DPPH assay. We have further checked the effect of HSA on the antioxidant property of morin and MPNPs. HSA binding with MPNPs was also found to influence the in vitro release property of morin from MPNPs wherein a delayed release response is observed.

Application of Microbes in Remediation of Hazardous Wastes: A Review

Currently, pollution control, environmental management, treatment and recycling of wastes have become critical issues. One of the major reasons behind the growing environmental pollution is illegal disposal of waste. Due to the toxicity of waste, establishing efficient and environmentally friendly method to degrade and detoxify these wastes represent an important research challenge. Various physiochemical methods are applied all over the world for solid waste management. The application of microbes to degrade waste is gaining attention due to its environmental and economic benefits. The present review deals with application of microbes in bioremediation of hazardous wastes. This review also outlines the various factors that limit the use of microbial waste bioremediation technologies. Moreover, the prospects of waste valorization for the production of biopolymers, biofuels, biocompost and industrial enzymes are also discussed in the review article.