Fluorescence Enhancement Based Quantification of Human Serum Albumin from Biological Sample Using Indole Based Nanosuspension: Molecular Interactions and Molecular Docking Studies.

Fluorescent 3-[(E)-(2-phenylhydrazinylidene) methyl]-1H-indole (PHI) was synthesized by condensation of indole-3-carboxaldehyde and phenyl hydrazine in presence of acetic acid and ethanol and after spectral characterization used further to prepare its aqueous nano suspension by reprecipitation method using polyvinylpyrrolidone (PVP) as stabilizer. The average particle size of nano suspension measured by Dynamic Light Scattering (DLS) was found 77.5 nm while FESEM microphotograph showed spherical morphology. The blue shift in the absorption spectrum and stokes shifted fluorescence of nanosuspension of PHI compared to its monomer spectrum in dilute solution indicate formation of H-type aggregate by face to face overlapping of the molecules.The aggregation induced enhanced emission (AIEE) of PVP capped nanosuspension of PHI is increased appreciably by presence of aqueous solution of human serum albumin (HSA). A suitable mechanism of molecular binding interactions based on complex formation between PHI nanoaggregate and HSA through PVP is proposed. Fluorescence life time, zeta potential and particle size data of PHI nanoparticles (PHINPs) obtained in presence of different amounts of HSA are in support of molecular interactions leading to complex formation. The molecular docking studies showed that HSA and PVP capped PHINPs exhibit strong hydrogen bonding interaction. The fluorescence enhancement effect induced in PHI nanosuspension is used further to develop analytical method for quantitative estimation of HSA in aqueous biological sample solution.

FRET Between Riboflavin and 9-Anthraldehyde Based Fluorescent Organic Nanoparticles Possessing Antibacterial Activity.

The aqueous suspension of fluorescent nanoparticles were prepared by using 9-anthradehdye derivative (AH). The nanoparticles (AHNPs) were characterized using DLS-zeta sizer and SEM techniques. The photo physical properties of nanoparticles and precursor were measured and compared using UV-absorption spectroscopy, fluorescence spectroscopy and fluorescence lifetime studies. The significant overlap between fluorescence spectrum of AHNPs and excitation spectrum of Riboflavin (RF) led us to explore Fluorescence Resonance Energy Transfer (FRET) studies between AHNPs and RF in aqueous medium. The mechanism of FRET from AHNPs to RF discussed on spectral observations, thermodynamic parameters and changes produces in fluorescence lifetime in absence and presence of different concentrations of RF to AHNPs. The limit of detection for RF (0.071 µM) is considerably low compared with reported methods. Thus, we explore AHNPs as novel nano probe for quantitative determination of RF in pharmaceutical samples based on FRET study. In addition with this, AHNPs has excellent antibacterial activity than the bulk material for two different bacteria culture viz. E. coli and Bacillus sps. Graphical Abstract 9-anthradehdye based fluorescent nanoparticles (AHNPs) explores as nano probe to detect Riboflavin (RF) in aqueous medium based on Fluorescence Resonance Energy Transfer (FRET) studies. The proposed analytical method successfully applied for quantitative determination of RF in pharmaceutical samples. In addition, with this, AHNPs has excellent antibacterial activity than the bulk material for two different bacteria culture suspension viz. E. coli and Bacillus sps.

Carbazole based nanoprobe for selective recognition of Fe3+ ion in aqueous medium: Spectroscopic insight.

A simple carbazole based nanoprobe prepared by reprecipitation method shows selective sensing behavior for Fe3+ ion in aqueous medium. The prepared SDS capped 9-phenyl carbazole nanoparticles (9-PCzNPs) has narrower particle size distribution with an average diameter 35nm and zeta potential of -34.3mV predicted a good stability with negative surface charge over the nanoparticles. The Field Emission Scanning Electron Microscopy (FE-SEM) image showed cubic shape morphology of nanoparticles. The aqueous suspension of SDS capped 9-phenyl carbazole nanoparticles exhibited aggregation induced enhanced red shifted intense emission in comparison with the emission arising from dilute solution of 9-phenyl carbazole in DCM. The cation recognition test based on fluorescence change shows Fe3+ ion induce significant fluorescence quenching, however remaining cations responds negligibly. The obtained quenching data fit into Stern-Volmer relation in the concentration range of 0.0-1.0µg·mL-1 of Fe3+ ion solution and the detection limit is 0.0811µg·mL-1. The probable mechanism of fluorescence quenching of SDS capped 9-PCzNPs is because of adsorption of Fe3+ ion over the negatively charged surface of NPs through electrostatic interaction. Thus the proposed method was successfully applied for the detection of Fe3+ ion in environmental water sample.