Deciphering biophysical signatures for microbiological applications.

Identification and classification of microbes are vital for maintenance of normal and altered state of human health and have applications in pharmaceutical industries, food processing, clinical analysis, and treatment. Development of methods aimed towards achieving these goals must be rapid and reliable. Conventional physiochemical and morphology-based methods of identification are often ambiguous, while newer molecular methods such as flow cytometry and polymerase chain reaction, though reliable, are time and resource intensive. Spectroscopic methods provide advantages over conventional methods as these can be fast, non-destructive, and highly specific. Surface charge of bacteria is an important parameter which can reveal composition of cell wall and is attributed to the presence of carboxyl and phosphoryl groups. Interaction of the cell with the solvent and response to various stresses can hence be measured by the changes in surface charge. In this study, we have obtained auto-fluorescence spectra (tryptophan) and dynamic light scattering (DLS) measurements from common pathogenic strains of Pseudomonas aeruginosa and Staphylococcus aureus. Fluorescence emission spectra were obtained in the range of 300-550 nm at excitation wavelength of 280 nm and DLS measurements comprised zeta potential and size parameters. Both types of measurements were performed in physiological and stress-induced conditions such as heat, sonication, and antibiotic treatment with vancomycin and cetylpyridinium chloride. Effects of these antibiotics on membrane integrity and cell viability, as obtained by DLS measurements, were statistically significant and comparable with conventional methods. Multivariate analysis enabled clustering of 83% of the samples at the genera level, based on variances from auto-fluorescence and DLS measurements.

Recent trends in two-photon auto-fluorescence lifetime imaging (2P-FLIM) and its biomedical applications.

Two photon fluorescence microscopy and the numerous technical advances to it have served as valuable tools in biomedical research. The fluorophores (exogenous or endogenous) absorb light and emit lower energy photons than the absorption energy and the emission (fluorescence) signal is measured using a fluorescence decay graph. Additionally, high spatial resolution images can be acquired in two photon fluorescence lifetime imaging (2P-FLIM) with improved penetration depth which helps in detection of fluorescence signal in vivo. 2P-FLIM is a non-invasive imaging technique in order to visualize cellular metabolic, by tracking intrinsic fluorophores present in it, such as nicotinamide adenine dinucleotide, flavin adenine dinucleotide and tryptophan etc. 2P-FLIM of these molecules enable the visualization of metabolic alterations, non-invasively. This comprehensive review discusses the numerous applications of 2P-FLIM towards cancer, neuro-degenerative, infectious diseases, and wound healing.

Enantiomeric Recognition and Separation by Chiral Nanoparticles.

Chiral molecules are stereoselective with regard to specific biological functions. Enantiomers differ considerably in their physiological reactions with the human body. Safeguarding the quality and safety of drugs requires an efficient analytical platform by which to selectively probe chiral compounds to ensure the extraction of single enantiomers. Asymmetric synthesis is a mature approach to the production of single enantiomers; however, it is poorly suited to mass production and allows for only specific enantioselective reactions. Furthermore, it is too expensive and time-consuming for the evaluation of therapeutic drugs in the early stages of development. These limitations have prompted the development of surface-modified nanoparticles using amino acids, chiral organic ligands, or functional groups as chiral selectors applicable to a racemic mixture of chiral molecules. The fact that these combinations can be optimized in terms of sensitivity, specificity, and enantioselectivity makes them ideal for enantiomeric recognition and separation. In chiral resolution, molecules bond selectively to particle surfaces according to homochiral interactions, whereupon an enantiopure compound is extracted from the solution through a simple filtration process. In this review article, we discuss the fabrication of chiral nanoparticles and look at the ways their distinctive surface properties have been adopted in enantiomeric recognition and separation.