Detection of Sialic Acid and Imaging of Cell-Surface Glycan Using a Fluorescence-SERS Dual Probe.

Sialic acid (SA) is an acidic monosaccharide present in the human brain and body fluids in the form of N-acetylneuraminic acid. It is also a well-known cancer biomarker. For decades, it has remained a challenging task to design synthetic receptors for SA. However, mainly because of the interference from other sugars with the receptors, it was challenging to differentiate SA from other sugars. Here, we report the development of a two-component aggregation-induced emissive (AIE) probes that can interact with SA and other saccharides via noncovalent interactions with unique emission fingerprints. Analysis of the output signals enabled the reliable detection and clear discrimination of SA in the presence of other saccharides with high accuracy. Further, its potential application in cellular glycan mapping has been explored by fluorescence imaging and surface-enhanced Raman scattering with MDA-MB-231 breast cancer cells.

Hybrid exosomes, exosome-like nanovesicles and engineered exosomes for therapeutic applications.

Exosomes are endosome-derived nanovesicles involved in cellular communication. They are natural nanocarriers secreted by various cells, making them suitable candidates for diverse drug delivery and therapeutic applications from a material standpoint. They have a phospholipid bilayer decorated with functional molecules and an enclosed parental matrix, which has attracted interest in developing designer/hybrid engineered exosome nanocarriers. The structural versatility of exosomes allows the modification of their original configuration using various methods, including genetic engineering, chemical procedures, physical techniques, and microfluidic technology, to load exosomes with additional cargo for expanded biomedical applications. Exosomes show enormous potential for overcoming the limitations of conventional nanoparticle-based techniques in targeted therapy. This review highlights the exosome sources, characteristics, state of the art in the field of hybrid exosomes, exosome-like nanovesicles and engineered exosomes as potential cargo delivery vehicles for therapeutic applications.

Interfacial Engineering of CuCo2S4/g-C3N4 Hybrid Nanorods for Efficient Oxygen Evolution Reaction.

Altering the morphology of electrochemically active nanostructured materials could fundamentally influence their subsequent catalytic as well as oxygen evolution reaction (OER) performance. Enhanced OER activity for mixed-metal spinel-type sulfide (CuCo2S4) nanorods is generally done by blending the material that has high conductive supports together with those having a high surface volume ratio, for example, graphitic carbon nitrides (g-C3N4). Here, we report a noble-metal-free CuCo2S4 nanorod-based electrocatalyst appropriate for basic OER and neutral media, through a simple one-step thermal decomposition approach from its molecular precursors pyrrolidine dithiocarbamate-copper(II), Cu[PDTC]2, and pyrrolidine dithiocarbamate-cobalt(II), Co[PDTC]2 complexes. Transmission electron microscopy (TEM) images as well as X-ray diffraction (XRD) patterns suggest that as-synthesized CuCo2S4 nanorods are highly crystalline in nature and are connected on the g-C3N4 support. Attenuated total reflectance-Fourier-transform infrared (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy studies affirm the successful formation of bonds that bridge (Co-N/S-C) at the interface of CuCo2S4 nanorods and g-C3N4. The kinetics of the reaction are expedited, as these bridging bonds function as an electron transport chain, empowering OER electrocatalytically under a low overpotential (242 mV) of a current density at 10 mA cm-2 under basic conditions, resulting in very high durability. Moreover, CuCo2S4/g-C3N4 composite nanorods exhibit a high catalytic activity of OER under a neutral medium at an overpotential of 406 mV and a current density of 10 mA cm-2.

A Photoregulated Racemase Mimic.

The racemase enzymes convert L-amino acids to their D-isomer. The reaction proceeds through a stepwise deprotonation-reprotonation mechanism that is assisted by a pyridoxal phosphate (PLP) coenzyme. This work reports a PLP-photoswitch-imidazole triad where the racemization reaction can be controlled by light by tweaking the distance between the basic residue and the reaction centre.

Switching the recognition ability of a photoswitchable receptor towards phosphorylated anions.

An azobenzene based photoswitchable macrocyclic receptor displays different binding affinities in its E and Z forms towards various phosphorylated coenzymes under physiological conditions with remarkable selectivity for ATP in the E-form and selectivity towards GTP in the photoisomerized Z-form. Linear discriminant analysis clearly separated the analytes using the E-form. An application of this method enabled monitoring the progress of enzymatic phosphorylation using a tyrosine kinase enzyme.

Modulation of Electronic Mobility of a One-Dimensional Coordination Polymeric Molecular Wire with Light.

Metal ions often influence the photoswitching efficiency of a photochromic system. This article reports a one-dimensional polymer having cyclic azobenzenes coordinated to silver ions that are bridged by nitrates. The coordination polymer (CP-2) displays a photoresponsive behavior. The switching ability in the polymer form was faster compared to the parent azobenzene ligand without the metal ions. Azobenzenes are reported to be poorly conducting. Here, although the azobenzene ligand does not show significant electronic mobility, the coordination polymer (CP-2) displays a modest conductivity. The conductance in the cis form of the polymer is significantly higher compared to the trans form. Upon exposure to visible light, the cis form undergoes photoisomerization to the trans form with a drastic drop in the electronic mobility. The trans form can be reverted to the cis form thermally or by using UV light. Thus, this system offers a reversible control of the conductivity using light.

Light triggered encapsulation and release of C60 with a photoswitchable TPE-based supramolecular tweezers.

Stimuli responsive hosts for C60 can control its binding and release on demand. A photoswitchable TPE based supramolecular host can encapsulate C60 in the Z-form with a markedly different visual change in the colour. In addition, the Z-1 bound C60 has been characterized by various spectroscopic methods and mass spectrometry. Upon exposure to visible light (>490 nm), the host switches to the E-form where the structural complementarity with the guest is destroyed as a result of which the C60 is disassembled from the host. The results described herein reveals an actionable roadmap to pursue further advances in component self-assembly particularly light-induced association and dissociation of a guest molecule.

Reversible photoresponsive activity of a carbonic anhydrase mimic.

The carbonic anhydrase (CA) enzyme reversibly transforms carbon dioxide and water to a carbonate ion and a proton. Photoresponsive enzyme mimics, where the CA-activity can be turned on and off reversibly with light, have not been reported so far. We have designed an active site mimic that offers reversible control of the catalytic activity using light. Moreover, in the presence of a cationic polymer, we have demonstrated that the CA-activity was further enhanced by stabilizing the transition state with the cis-form of the enzyme mimic which can catalyze the hydration of gaseous CO2.