Synthesis of CdSe quantum dots using selenium dioxide as selenium source and its interaction with pepsin

Learning from human metabolism for nanomedicine: a convertible bismuth-agent for tumour-selective theranostics

Tumour-selective theranostic agents have attracted considerable interest over the past decade in oncology owing to their extraordinary anticancer efficacy. However, it still remains a challenge to develop theranostic agents balancing biocompatibility, multidimensional theranostics, tumour-selectivity, and simple components. Inspired by the metabolic pathways of exogenous sodium selenite against selenium-deficient diseases, reported here is the first convertible bismuth-based agent for tumour-selective theranostic functionalities. The specifically overexpressed substances in tumour tissue enable it to act as a natural reactor for the conversion from bismuth selenite to bismuth selenide, activating the theranostic functionalities specifically in tumour tissues. The converted product exhibits excellent multidimensional imaging-guided therapy. This study not only demonstrates a simple agent with both biocompatibility and sophisticated tumour-selective theranostic functionalities, but also pioneers a new approach from emulating nature towards oncological theranostic applications.

HOCl-Activated Reactive Organic Selenium Delivery Platform for Alleviation of Inflammation

Selenium plays an important role in the biological system and can be used to treat various types of diseases. However, the current selenium delivery systems face the problems of low activity of released Se-containing compounds or nonspecific toxicity of reactive organic selenium donors in living systems. In response to these problems, we constructed a reactive organic selenium delivery platform by the activation of HOCl. Compared with prodrugs without activation capability, the hypochloroselenoite derivatives released from the present platform after activation displayed higher reactivity and could react with various nucleophiles to participate in specific life processes. Taking the selected compound (DHU-Se1) as an example, we found that it could alleviate the process of inflammation by blocking the polarization of macrophages from M0 to M1. Therefore, the development of this system is of great significance for expanding the application of selenium-containing compounds and treating related diseases.

Investigation on the interaction between myricetin and dihydromyricetin with trypsin, α-chymotrypsin, lysozyme by spectroscopy and molecular docking methods

The interaction between myricetin and dihydromyricetin with trypsin, α-chymotrypsin and lysozyme was investigated using multispectral and molecular docking methods. The results of fluorescence quenching revealed that myricetin and dihydromyricetin could quench the intrinsic fluorescence of three different proteinases through a static quenching procedure. The binding constant and number of binding sites at different temperatures were measured. The thermodynamic parameters obtained at different temperatures showed van der Waals' interactions and hydrogen bonds played the main roles in the interaction of myricetin with trypsin and lysozyme, hydrophobic force was dominant both in myricetin with α-chymotrypsin interaction and dihydromyricetin with trypsin and lysozyme interaction, as for the electrostatic forces, it was the mainly driving force in dihydromyricetin binding to α-chymotrypsin. There was non-radiative energy transfer between three proteinases and myricetin or dihydromyricetin with high probability. The microenvironment of trypsin, α-chymotrypsin and lysozyme is changed. The docking studies revealed that myricetin and dihydromyricetin entered the hydrophobic cavity of three proteinases and formed hydrogen bond. The binding affinity of myricetin or dihydromyricetin is difference with the trypsin, α-chymotrypsin and lysozyme due to the different molecular structure.

Exploring the interactions of naringenin and naringin with trypsin and pepsin: Experimental and computational modeling approaches

Naringenin and naringin are two natural compounds with important health benefits, whether as food or drug. It is necessary to study the interactions between naringenin/naringin and digestive proteases, such as trypsin and pepsin. In this study, the bindings of naringenin and naringin to trypsin and pepsin were investigated using multi-spectroscopy analysis and computational modeling approaches. Fluorescence experiments indicate that both naringenin and naringin can quench the intrinsic fluorescence of trypsin/pepsin via static quenching mechanism. Naringin binds trypsin/pepsin in a more firmly way than naringenin. Thermodynamic analysis reveals that the interactions of naringenin/naringin and trypsin/pepsin are synergistically driven by enthalpy and entropy, and the major driving forces are hydrophobic, electrostatic interactions and hydrogen bonding. Synchronous fluorescence spectroscopy, circular dichroism spectroscopy and FT-IR show that naringenin/naringin may induce microenvironmental and conformational changes of trypsin and pepsin. Molecular docking reveals that naringenin binds in the close vicinity of the active site (Ser-195) of trypsin and Asp-32 (the catalytic activity of pepsin) appears in naringin-pepsin system. The direct interactions between naringenin or naringin and catalytic amino acid residues will inhibit the catalytic activity of trypsin and pepsin, respectively. The results of molecular dynamic simulation validate the reliability of the docking results.

CdSe quantum dots capped with a deep eutectic solvent as a fluorescent probe for copper(II) determination in various drinks

The present study shows that copper(II) ions can be determined with a new fluorescent probe that is based on the use of CdSe quantum dots capped with deep eutectic solvent (DES-CdSe QDs). The capped QDs were prepared in aqueous phase by a one-step procedure under ambient atmosphere using selenium dioxide as a stable precursor for selenium, and ascorbic acid as non-toxic reducing agent. The deep eutectic solvent is composed of choline chloride and thioglycolic acid and acts as stabilizing and functionalizing agent. The fluorescent probe undergoes an increase in the fluorescence intensity (with excitation/emission wavelengths at 380/560 nm) in the presence of Cu(II). Other ions display no significant effect on fluorescence. The effects of sample pH value, concentration of buffer, and volume of QDs solution were optimized by response surface methodology using a Box-Behnken statistical design. Under the optimal conditions, the response of the probe is linear in the 10-600 nM Cu(II) concentration range, with a 5.3 nM limit of detection. This is lower than the allowable maximum Cu(II) concentration in drinking water. The relative standard deviation of the method for five replicate measurements of Cu(II) at a 100 nM concentration level is 2.0%. The probe was successfully applied to the determination of Cu(II) in various drinks. Graphical abstractSchematic representation of a fluorometric method for the determination of Cu(II) at nanomolar concentration levels. The fluorescent system consists of deep eutectic solvent-capped cadmium selenide quantum dots (DES-CdSe QDs). Fluorescence is strongly enhanced by copper(II).

Mutual influence of piceatannol and bisphenol F on their interaction with pepsin: Insights from spectroscopic, isothermal titration calorimetry and molecular modeling studies

The individual and combined interactions of bisphenol F and piceatannol with pepsin were investigated using spectroscopic methods (fluorescence, UV-vis absorption, and circular dichroism spectroscopy), combined with isothermal titration calorimetry and molecular docking. Thermodynamic data showed that hydrogen bonds and van der Waals forces might play a major role for the binding process. Site marking experiments and molecular docking confirmed the binding sites of these two ligands on pepsin. The discrepancy in the binding constant between the binary and ternary systems indicated the competitive binding of piceatannol and bisphenol F to pepsin. Circular dichroism spectra studies suggested that the binding of the two ligands led to a loosening of pepsin backbone. Enzyme activity assays indicated that the inhibition of pepsin activity by piceatannol and bisphenol F was competitive. These results will be helpful to understand the mechanism of piceatannol and bisphenol F affecting the activity of digestive proteases in the sight of the food security.

Interactions of carbon quantum dots from roasted fish with digestive protease and dopamine

The carbon quantum dots from roasted fish interacted with digestive protease and dopamine.

Thermodynamic and conformational changes of protein toward interaction with nanoparticles: a spectroscopic overview

Nanoparticles (NPs) in different forms have been widely used in medicine and pharmaceutics for diagnosis and drug delivery.

Interaction of digestive enzymes with tunable light emitting quantum dots: a thorough Spectroscopic investigation

In this article, we have examined the direct spectroscopic and microscopic evidence of efficient quantum dots-α-chymotrypsin (ChT) interaction. The intrinsic fluorescence of digestive enzyme is reduced in the presence of quantum dots through ground-state complex formation. Based on the fluorescence data, quenching rate constant, binding constant, and number of binding sites are calculated under optimized experimental conditions. Interestingly, fluorescence quenching method clearly illustrated the size dependent interaction of MPA-CdTe quantum dots. Conformational change of ChT was traced using synchronous fluorescence measurements, circular dichroism and FTIR spectroscopic methods. Furthermore, the AFM results revealed that the individual enzyme molecule dimensions were changed after interacting with quantum dot. Consequently, this result could be helpful for constructing safe and effective utilisation of QDs in biological applications.

Investigation on interaction between Ligupurpuroside A and pepsin by spectroscopic and docking methods

Ligupurpuroside A is one of the major glycoside in Ku-Din-Cha, a type of Chinese functional tea. In order to better understand its digestion and metabolism in humans, the interaction between Ligupurpuroside A and pepsin has been investigated by fluorescence spectra, UV-vis absorption spectra and synchronous fluorescence spectra along with molecular docking method. The fluorescence experiments indicate that Ligupurpuroside A can effectively quench the intrinsic fluorescence of pepsin through a combined quenching way at the low concentration of Ligupurpuroside A, and a static quenching procedure at the high concentration. The binding constant, binding sites of Ligupurpuroside A with pepsin have been calculated. The thermodynamic analysis suggests that non-covalent reactions, including electrostatic force, hydrophobic interaction and hydrogen bond are the main forces stabilizing the complex. According to the Förster's non-radiation energy transfer theory, the binding distance between pepsin and Ligupurpuroside A was calculated to be 3.15 nm, which implies that energy transfer occurs between pepsin and Ligupurpuroside A. Conformation change of pepsin was observed from UV-vis absorption spectra and synchronous fluorescence spectra under experimental conditions. In addition, all these experimental results have been validated by the protein-ligand docking studies which show that Ligupurpuroside A is located in the cleft between the domains of pepsin.