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The kynurenine metabolite is associated with many diseases and disorders, ranging from diabetes and sepsis to more recently COVID-19. Here we report a fluorescence-based assay for the detection of kynurenine in urine using a specific chemosensor, 3-formyl-4-(ethylthio)-7-(diethylamino)-coumarin. The assay produces a linear response at clinically relevant ranges (1–20 μM), with a limit of detection of 0.7 μM. The average standard addition recoveries of kynurenine in synthetic urine samples are near to 100%, and the relative standard deviation values are less than 8%. The established fluorescence assay for quantitative analysis of kynurenine in urine is facile, sensitive and accurate and holds great potential for low-cost and high-throughput analysis of kynurenine in clinical laboratory settings. [ABSTRACT FROM AUTHOR]

Glycans – simple or complex carbohydrates – play key roles as recognition determinants and modulators of numerous physiological and pathological processes. Thus, many biotechnological, diagnostic and therapeutic opportunities abound for molecular recognition entities that can bind glycans with high selectivity and affinity. This review begins with an overview of the current biologically and synthetically derived glycan-binding scaffolds that include antibodies, lectins, aptamers and boronic acid-based entities. It is followed by a more detailed discussion on various aspects of their generation, structure and recognition properties. It serves as the basis for highlighting recent key developments and technical challenges that must be overcome in order to fully deal with the specific recognition of a highly diverse and complex range of glycan structures. [ABSTRACT FROM AUTHOR]

Reported herein is a switchable surface that relies on electrically-induced conformational changes within surface-grafted arginine-glycine- aspartate (RGD) oligopeptides as the means of modulating cell adhesion. [ABSTRACT FROM AUTHOR]

Recently, there has been an outburst of research on engineered cell–material interfaces driven by nanotechnology and its tools and techniques. This tutorial review begins by providing a brief introduction to nanostructured materials, followed by an overview of the wealth of nanoscale fabrication and analysis tools available for their development. This background serves as the basis for a discussion of early breakthroughs and recent key developments in the endeavour to develop nanostructured materials as smart interfaces for fundamental cellular studies, tissue engineering and regenerative medicine. The review covers three major aspects of nanostructured interfaces – nanotopographical control, dynamic behaviour and intracellular manipulation and sensing – where efforts are continuously being made to further understand cell function and provide new ways to control cell behaviour. A critical reflection of the current status and future challenges are discussed as a conclusion to the review. [ABSTRACT FROM AUTHOR]

Saccharides – a versatile class of biologically important molecules – are involved in a variety of physiological and pathological processes, but their detection and quantification is challenging. Herein, surface plasmon resonance and self-assembled monolayers on gold generated from bis-boronic acid bearing a thioctic acid moiety, whose intramolecular distance between the boronic acid moieties is well defined, are shown to detect d-glucose with high selectivity, demonstrating a higher affinity than other saccharides probed, namely d-galactose, d-fructose and d-mannose. [ABSTRACT FROM AUTHOR]

A bis-boronic acid modified electrode for the sensitive and selective determination of glucose concentrations has been developed. The electrochemical characteristics of the sensor with added saccharides were investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The bis-boronic acid modified electrode was both sensitive and selective for glucose. [ABSTRACT FROM AUTHOR]

Calcium phosphates are used widely as orthopaedic implants and in nanocrystalline form to enable the transfer of genetic material into cells. Despite widespread use, little is known about their fate after they have crossed the cell membrane. Here we present a method of surface modification of silicon-substituted hydroxyapatite (SiHA) through a silane group, which enables the engraftment of a fluorescent dye to facilitate real-time biological tracking. Surface modification of the nanocrystal surface was undertaken using (3-mercaptopropyl)trimethoxysilane (MPTS), which presented a thiol for the further attachment of a fluorophore. Successful modification of the surface was demonstrated using zeta potential measurements and fluorescence microscopy and the number of thiol groups at the surface was quantified using Ellman's reagent. In vitro experiments using the fluorescently modified particles enabled the discrimination of the calcium phosphate particulate from other biological debris following internalisation by a population of MC3T3 (pre-osteoblast) cells and the particles were shown to maintain fluorescence for 24 hours without quenching. The successful modification of the surface of SiHA with thiol groups offers the tantalising possibility of the intracellular growth factor delivery. [ABSTRACT FROM AUTHOR]

Self-assembled monolayers (SAMs) containing azobenzene moieties are very attractive for a wide range of applications, including molecular electronics and photonics, bio-interface engineering and sensoring. However, very little is known about the aggregation and photoswitching behavior that azobenzene units undergo during the SAM formation process. Here, we demonstrate that the formation of thiol-based SAMs containing azobenzenes (denoted as AzoSH) on gold surfaces is characterised by a two-step adsorption kinetics, while a three-step assembly process has been identified for dithiolane-based SAMs containing azobenzenes (denoted AzoSS). The H-aggregation on the AzoSS SAMs was found to be remarkably dependent on the time of self-assembly, with less aggregation as a function of time. While photoisomerization of the AzoSH was suppressed for all different assembly times, the reversible trans–cis photoisomerization of AzoSS SAMs formed over 24 hours was clearly observed upon alternating UV and Vis light irradiation. We contend that detailed information on formation kinetics and related optical properties is of crucial importance for elucidating the photoswitching capabilities of azobenzene-based SAMs. [ABSTRACT FROM AUTHOR]

Discretely functionalized gold nanoparticles (AuNPs) with an amine surface functional group on each AuNP have been synthesized as a crude mixture with a significant amount of nonfunctional AuNPs. By employing the mechanoresponsive nature and reversible self-assembling properties of the mono-functionalized AuNP on a crown ether-coated gold surface, mono-functionalized AuNPs have been successfully isolated from a crude mixture. A real-time surface plasmon resonance (SPR) with organic solvent-compatible microfluidic device/instrumentation has been built together with a three-step denoising procedure for the detection of SPR absorption dip shifts with high sensitivity. With this instrument, pH-driven self-assembly and disassembly processes of the mono-functionalized gold nanoparticles (AuNPs), non-functional/mono-functionalized (crude) AuNPs, and randomly functionalized AuNPs on a crown ether-coated gold surface have been monitored simultaneously. From the real-time SPR traces, in general, the self-assembled AuNPs are stable on the surface with a solvent flow for a long period of time. These AuNPs possess different self-assembling and disassembling properties. In particular, SPR response traces obtained from mono-functionalized AuNPs reveal complete pH-driven self-assembly and disassembly processes on the gold surface. This device has enabled real-time monitoring of mono-functionalized AuNPs characteristics with the exclusion of non-functional AuNPs in a crude mixture. The SPR trace of self-assembled, randomly functionalized AuNPs indicates that only partial AuNPs were disassembled from the surface and eluted away after base treatment. Residue randomly functionalized AuNPs that were intact with the gold surface might possess higher number of functional group on each NP, rendering multivalent binding with enhanced stability towards the base. This observation has also been confirmed by atomic force microscopy (AFM). SPR monitoring of discretely functionalized AuNPs enables a real-time characterization other than the conventional transmission electron microscopy (TEM) and UV/visible absorption spectroscopic methods. The reported mono-functionalized AuNPs may find applications in single molecular detection and analysis of molecular binding events with a quantification capability with higher sensitivity. [ABSTRACT FROM AUTHOR]

Type III-B first generation [3]rotaxane and second generation [4]rotaxane dendrimers have been synthesized via (1) a modified copper-catalyzed alkyne–azide cycloaddition (CuAAC), (2) Glaser–Hay's acetylenic oxidative homo-coupling, and (3) amide formation. The dendron does not reveal obvious cytotoxicities in L929 fibroblast cells. The rotaxane dendrimers can capture ammonia and are switchable both in solution and on surfaces. [ABSTRACT FROM AUTHOR]

Correction for 'The challenges of glycan recognition with natural and artificial receptors' by Stefano Tommasone et al., Chem. Soc. Rev., 2019, 48, 5488–5505. [ABSTRACT FROM AUTHOR]