Protein targets in Mycobacterium tuberculosis and their inhibitors for therapeutic implications: A narrative review.

Advancement in the area of anti-tubercular drug development has been full-fledged, yet, a very less number of drug molecules have reached phase II clinical trials, and therefore "End-TB" is still a global challenge. Inhibitors to specific metabolic pathways of Mycobacterium tuberculosis (Mtb) gain importance in strategizing anti-tuberculosis drug discovery. The lead compounds that target DNA replication, protein synthesis, cell wall biosynthesis, bacterial virulence and energy metabolism are emerging as potential chemotherapeutic options against Mtb growth and survival within the host. In recent times, the in silico approaches have become most promising tools in the identification of suitable inhibitors for specific protein targets of Mtb. An update in the fundamental understanding of these inhibitors and the mechanism of interaction may bring hope to future perspectives in novel drug development and delivery approaches. This review provides a collective impression of the small molecules with potential antimycobacterial activities and their target pathways in Mtb such as cell wall biosynthesis, DNA replication, transcription and translation, efflux pumps, antivirulence pathways and general metabolism. The mechanism of interaction of specific inhibitor with their respective protein targets has been discussed. The comprehensive knowledge of such an impactful area of research would essentially reflect in the discovery of novel drug molecules and effective delivery approaches. This narrative review encompasses the knowledge of emerging targets and promising chemical inhibitors that could potentially translate in to the anti-TB-drug discovery.

Analysis of Silicon Quantum Dots and Serum Proteins Interactions Using Asymmetrical Flow Field-Flow Fractionation.

Semiconductor nanocrystals or quantum dots (QDs) have gained significant attention in biomedical research as versatile probes for imaging, sensing, and therapies. However, the interactions between proteins and QDs, which are crucial for their use in biological applications, are not yet fully understood. Asymmetric flow field-flow fractionation (AF4) is a promising method for analyzing the interactions of proteins with QDs. This technique uses a combination of hydrodynamic and centrifugal forces to separate and fractionate particles based on their size and shape. By coupling AF4 with other techniques, such as fluorescence spectroscopy and multi-angle light scattering, it is possible to determine the binding affinity and stoichiometry of protein-QD interactions. Herein, this approach has been utilized to determine the interaction between fetal bovine serum (FBS) and silicon quantum dots (SiQDs). Unlike metal-containing conventional QDs, SiQDs are highly biocompatible and photostable in nature, making them attractive for a wide range of biomedical applications. In this study, AF4 has provided crucial information on the size and shape of the FBS/SiQD complexes, their elution profile, and their interaction with serum components in real time. The differential scanning microcalorimetric technique has also been employed to monitor the thermodynamic behavior of proteins in the presence of SiQDs. We have investigated their binding mechanisms by incubating them at temperatures below and above the protein denaturation. This study yields various significant characteristics such as their hydrodynamic radius, size distribution, and conformational behavior. The compositions of SiQD and FBS influence the size distribution of their bioconjugates; the size increases by intensifying the concentration of FBS, with their hydrodynamic radii ranging between 150 and 300 nm. The results signify that in the alliance of SiQDs to the system, there is an augmentation of the denaturation point of the proteins and hence their thermal stability, providing a more comprehensive understanding of the interactions between FBS and QDs.

The combined effect of thermal-acid hydrolysis, periodate oxidation, and iodine species removal on the properties of native tapioca (Manihot esculenta Crantz) starch.

Through a four-step top-down approach, native tapioca starch (NTS) was thermally acid-hydrolyzed, periodate-oxidized with subsequent removal of iodine species (i.e., IO4(-), IO3(-), I(-), and I2), and dialdehyde tapioca starch (DTS) alcohol-precipitation. The percent yield was ∼91%. Analyses confirmed the presence of aldehydic functionalities (∼71%), effectual iodine species removal (∼98%), and enhanced water-solubility (∼96.57%). Besides, the combined treatment significantly reduced the Mw (∼57.81 kDa) and ameliorated homogeneity as well as thermal stability (Tmax âˆ¼ 667.15 °C). Structural-spectral characterization also confirmed the presence of aldehydic functionality, polymorphic transition (C- to A-type), and a higher degree of crystallinity (∼91.77%), the latter further corroborated by thermal analysis. The morphological study revealed that the combined treatment reduced size (∼393.55-nm-diameter and ∼5.22-µm-length) and changed shape into rod-like crystals. DTS showed considerably and significantly low cytotoxicity to HaCaT cells in vitro at the concentrations assayed over the test period (24 h). DTS's conformation was most stable at -289 kcal/mol and -151.7 au heat formation and minimum potential energies, respectively. Overall, these results demonstrated that the combined treatment had no deleterious effects on NTS's properties, thus yielded DTS with ideal properties for multifarious uses.

Polymeric Nanoparticles Limit the Collective Migration of Cellular Aggregates.

Controlling the propagation of primary tumors is fundamental to avoiding the epithelial to mesenchymal transition process leading to the dissemination and seeding of tumor cells throughout the body. Here we demonstrate that nanoparticles (NPs) limit the propagation of cell aggregates of CT26 murine carcinoma cells used as tumor models. The spreading behavior of these aggregates incubated with NPs is studied on fibronectin-coated substrates. The cells spread with the formation of a cell monolayer, the precursor film, around the aggregate. We study the effect of NPs added either during or after the formation of aggregates. We demonstrate that, in both cases, the spreading of the cell monolayer is slowed down in the presence of NPs and occurs only above a threshold concentration that depends on the size and surface chemistry of the NPs. The density of cells in the precursor films, measured by confocal microscopy, shows that the NPs stick cells together. The mechanism of slowdown is explained by the increase in cell-cell interactions due to the NPs adsorbed on the membrane of the cells. The present results demonstrate that NPs can modulate the collective migration of cells; therefore, they may have important implications for cancer treatment.

Nanostickers for cells: a model study using cell-nanoparticle hybrid aggregates.

We present direct evidence that nanoparticles (NPs) can stick together cells that are inherently non-adhesive. Using cadherin-depleted S180 murine cells lines, which exhibit very low cell-cell adhesion, we show that NPs can assemble dispersed single cells into large cohesive aggregates. The dynamics of aggregation, which is controlled by diffusion and collision, can be described as a second-order kinetic law characterized by a rate of collision that depends on the size, concentration, and surface chemistry of the NPs. We model the cell-cell adhesion induced by the "nanostickers" using a three-state dynamical model, where the NPs are free, adsorbed on the cell membrane or internalized by the cells. We define a "sticking efficiency parameter" to compare NPs and look for the most efficient type of NP. We find that 20 nm carboxylated polystyrene NPs are more efficient nanostickers than 20 nm silica NPs which were reported to induce fast wound healing and to glue soft tissues. Nanostickers, by increasing the cohesion of tissues and tumors, may have important applications for tissue engineering and cancer treatment.

Functional double-shelled silicon nanocrystals for two-photon fluorescence cell imaging: spectral evolution and tuning.

Functional near-IR (NIR) emitting nanoparticles (NPs) adapted for two-photon excitation fluorescence cell imaging were obtained starting from octadecyl-terminated silicon nanocrystals (ncSi-OD) of narrow photoluminescence (PL) spectra having no long emission tails, continuously tunable over the 700-1000 nm window, PL quantum yields exceeding 30%, and PL lifetimes of 300 µs or longer. These NPs, consisting of a Pluronic F127 shell and a core made up of assembled ncSi-OD kept apart by an octadecyl (OD) layer, were readily internalized into the cytosol, but not the nucleus, of NIH3T3 cells and were non-toxic. Asymmetrical field-flow fractionation (AF4) analysis was carried out to determine the size of the NPs in water. HiLyte Fluor 750 amine was linked via an amide link to NPs prepared with Pluronic-F127-COOH, as a first demonstration of functional NIR-emitting water dispersible ncSi-based nanoparticles.

Fabrication of solid collagen nanoparticles using electrospray deposition.

Collagen is a promising biomaterial for drug delivery due to advantages including high biocompatibility and biodegradable property. However, transforming collagen into solid nanoparticles is difficult, although the solid dosage form is advantageous for some administration routes including pulmonary and oral drug delivery. In this study, collagen solid nanoparticles are prepared in one-step using electrospray deposition under ambient temperature and pressure conditions. Although collagen molecules formed micron-sized aggregates in acetic acid solutions spontaneously, electrospraying the collagen solutions resulted in formation of nanofibers. Solid nanoparticles were obtained by increasing conductivity of the solution and/or inducing structural perturbation of the collagen molecules using salts. The ability of solid collagen particles as a drug carrier was demonstrated by incorporating theophylline as a model drug using a coaxial spray technique. Release of theophylline was controlled by cross-linking collagen molecules. Electrospray deposition was proved to be a powerful method for producing solid collagen nanoparticles for drug delivery.

Studies on the chemico-biological characteristics of bilirubin binding with collagen.

The clinical impact of bilirubin on collagen is investigated using various physical, chemical and biological methods. Thermo gravimetric analysis and differential scanning analysis of collagen-bilirubin complex matrices indicate that crosslinking does not alter their thermal behavior of collagen. The polydispersity of collagen-bilirubin complex increases in the reacting medium suggesting that there is an increase in the number of interacting points between them. Based on the zeta potential values, the rate of mobility of interacted complex decreases by inferring the extent of binding compared to the control collagen. Emission intensity begins to increase with increase in concentration of bilirubin which ascribes the conformational changes around the aromatic amino acids in collagen. Binding is indicated by an increase in resonance units and the responses are corrected by subtraction of those obtained for native collagen. Bilirubin showed a higher affinity for collagen at a concentration of about 25 nM/mg. In this study, the association rate has been calculated which depicts the increased affinity of bilirubin to collagen. Affinity for bilirubin to collagen has been found to be 8.89×10(-3) s(-1). The greater part of binding of bilirubin to collagen is found to be electrostatic in nature. The investigation leads to comprehend the affinity of collagen-bilirubin complex during jaundice diseased tissues.

Studies on the molecular significance in the interaction of bilirubin with collagen.

The present investigation is aimed to understand the physiological significance of bilirubin interaction with collagen. In human skin, collagen absorbs both free bilirubin and serum bound bilirubin from the human system. Interaction between bilirubin and collagen depends on time, temperature and concentration of bilirubin. There is an increase in the aggregation rate of collagen in the presence of biliruibin. At physiological condition, 125 nM of bilirubin is the maximum concentration absorbed by per mg of collagen molecule. Bilirubin accelerates the lateral growth of collagen fibrils by shifting its rate of nucleation. Moreover, collagen-bilirubin complex exhibit a tendency to undergo adsorption onto the surface of the fibroblast cells, showing detrimental effects on fibroblasts proliferations. Based on the collagen binding assays, the binding of bilirubin to collagen is found to be electrostatic in nature, which confirms binding between the amino acid fragment of α1 (I) region of collagen and carboxyl group of bilirubin. The biotinylated bilirubin derivatives show better binding to α1 (I) chain rather than α2 (I) chains which clearly designates that bilirubin shows greater affinity to α1 chains of collagen. This novel approach directs to reduce the occurrence of bilirubin in hyperbilirubinemia patients.