Deepali Sharma

Biosynthesis of ZnO nanoparticles using Jacaranda mimosifolia flowers extract: Synergistic antibacterial activity and molecular simulated facet specific adsorption studies.

The naturally occurring biomolecules present in the plant extracts have been identified to play an active role in the single step formation of nanoparticles with varied morphologies and sizes which is greener and environmentally benign. In the present work, spherical zinc oxide nanoparticles (ZnO NPs) of 2-4nm size were synthesized using aqueous extract of fallen Jacaranda mimosifolia flowers (JMFs), treated as waste. The microwave assisted synthesis was completed successfully within 5min. Thereafter, phase identification, morphology and optical band gap of the synthesized ZnO NPs were done using X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and UV-Visible spectroscopy techniques. The composition of JMFs extract was analyzed by gas chromatography-mass spectrometry (GC-MS) and the ZnO NPs confirmation was further explored with fourier transform infrared spectroscopy (FTIR). The GC-MS results confirmed the presence of oleic acid which has high propensity of acting as a reducing and capping agent. The UV-Visible data suggested an optical band gap of 4.03eV for ZnO NPs indicating their small size due to quantum confinement. Further, facet specific adsorption of oleic acid on the surface of ZnO NPs was studied computationally to find out the impact of biomolecules in defining the shape and size of NPs. The viability of gram negative Escherichia coli and gram positive Enterococcus faecium bacteria was found to be 48% and 43%, respectively at high concentration of NPs.

Electrochemical sensing platform amplified with a nanobiocomposite of L-phenylalanine ammonia-lyase enzyme for the detection of capsaicin.

The present study involves the development of a sensitive electrochemical biosensor for the determination of capsaicin extracted from chilli fruits, based on a novel signal amplification strategy using enzyme technology. For the first time, platinum electrode modified with multiwalled carbon nanotubes where phenylalanine ammonia-lyase enzyme was immobilized using nafion was characterized by attenuated total reflectance infrared spectroscopy, transmittance electron microscopy and thermo-gravimetric analysis supported by computational methods. Cyclic and differential pulse voltammetry measurements were performed to better understand the redox mechanism of capsaicin. The performance of the developed electrochemical biosensor was tested using spiked samples with recoveries ranging from 98.9 to 99.6%. The comparison of the results obtained from bare and modified platinum electrodes revealed the sensitivity of the developed biosensor, having a detection limit (S/N=3) of 0.1863µgmL(-1) and electron transfer rate constant (ks) of 3.02s(-1). Furthermore, adsorption and ligand-enzyme docking studies were carried out to better understand the redox mechanisms supported by density functional theory calculations. These results revealed that capsaicin forms hydrogen bonds with GLU355, GLU541, GLU586, ARG and other amino acids of the hydrophobic channel of the binding sites thereby facilitating the redox reaction for the detection of capsaicin.

Studies on Bacterial Proteins Corona Interaction with Saponin Imprinted ZnO Nanohoneycombs and Their Toxic Responses

Molecular imprinting generates robust, efficient, and highly mesoporous surfaces for biointeractions. Mechanistic interfacial interaction between the surface of core substrate and protein corona is crucial to understand the substantial microbial toxic responses at a nanoscale. In this study, we have focused on the mechanistic interactions between synthesized saponin imprinted zinc oxide nanohoneycombs (SIZnO NHs), average size 80-125 nm, surface area 20.27 m(2)/g, average pore density 0.23 pore/nm and number-average pore size 3.74 nm and proteins corona of bacteria. The produced SIZnO NHs as potential antifungal and antibacterial agents have been studied on Sclerotium rolfsii (S. rolfsii), Pythium debarynum (P. debarynum) and Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), respectively. SIZnO NHs exhibited the highest antibacterial (∼50%) and antifungal (∼40%) activity against Gram-negative bacteria (E. coli) and fungus (P. debarynum), respectively at concentration of 0.1 mol. Scanning electron spectroscopy (SEM) observation showed that the ZnO NHs ruptured the cell wall of bacteria and internalized into the cell. The molecular docking studies were carried out using binding proteins present in the gram negative bacteria (lipopolysaccharide and lipocalin Blc) and gram positive bacteria (Staphylococcal Protein A, SpA). It was envisaged that the proteins present in the bacterial cell wall were found to interact and adsorb on the surface of SIZnO NHs thereby blocking the active sites of the proteins used for cell wall synthesis. The binding affinity and interaction energies were higher in the case of binding proteins present in gram negative bacteria as compared to that of gram positive bacteria. In addition, a kinetic mathematical model (KMM) was developed in MATLAB to predict the internalization in the bacterial cellular uptake of the ZnO NHs for better understanding of their controlled toxicity. The results obtained from KMM exhibited a good agreement with the experimental data. Exploration of mechanistic interactions, as well as the formation of bioconjugate of proteins and ZnO NHs would play a key role to interpret more complex biological systems in nature.

CHAPTER 1:Perspective on Analytical Sciences and Nanotechnology

This chapter discusses the reciprocal impact of analytical science and nanotechnology and demonstrates how this technology can be expected to reinforce the responsibility of chemists in the field of analytical chemistry. Does analytical nanotechnology constitute the last step in the technical trend for miniaturization via the macro-to-micro-to-nano sequence? It obviously does. However, the “nanoscale” concept has introduced a new scenario where physicochemical principles, laws and properties are quite different from those of the macro and micro worlds. Since then, this concept has been gaining interest, but it is only in recent years that a great development effort has been made to obtain analytical technologies that are able to do direct analysis, using miniaturized equipment, with reduced amounts of solvents, on-site and with reduced energy costs and wastes. These improvements were linked to advances in other research areas (e.g., microelectronics, material sciences, biochemistry and, recently, nanotechnology). To this end, this chapter defines the limits of actual nanotechnological approaches and uses selected examples to illustrate the major relationships between analytical science and nanotechnology, for example: the design and use of nanodevices; the use of nanoparticles (and nanostructures) in analytical processes; and the extraction of accurate chemical information from the nano-world.