Fluorescent Sensor Array for Quantitative Determination of Saccharides

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2021-2022

The use of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry for the analysis of carbohydrates and glycoconjugates is a well-established technique and this review is the 12th update of the original article published in 1999 and brings coverage of the literature to the end of 2022. As with previous review, this review also includes a few papers that describe methods appropriate to analysis by MALDI, such as sample preparation, even though the ionization method is not MALDI. The review follows the same format as previous reviews. It is divided into three sections: (1) general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation, quantification and the use of computer software for structural identification. (2) Applications to various structural types such as oligo- and polysaccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals, and (3) other general areas such as medicine, industrial processes, natural products and glycan synthesis where MALDI is extensively used. Much of the material relating to applications is presented in tabular form. MALDI is still an ideal technique for carbohydrate analysis, particularly in its ability to produce single ions from each analyte and advancements in the technique and range of applications show little sign of diminishing.

A fluorescent NBD "turn-on" probe for the rapid and on-site analysis of fructose in food

High fructose intake is an important cause of metabolic disease. Due to the increasing prevalence of metabolic diseases worldwide, the development of an accurate and efficient tool for monitoring fructose in food is urgently needed to control the intake of fructose. Herein, a new fluorescent probe NBD-PQ-B with 7-nitrobenz-2-oxa-1, 3-diazole (NBD) as the fluorophore, piperazine (PQ) as the bridging group and phenylboronic acid (B) as the recognition receptor, was synthesized to detect fructose. The fluorescence of NBD-PQ-B increased linearly at 550 nm at an excitation wavelength of 497 nm with increasing fructose concentration from 0.1 to 20 mM. The limit of detection (LOD) of fructose was 40 μM. The pKa values of NBD-PQ-B and its fructose complexes were 4.1 and 10.0, respectively. In addition, NBD-PQ-B bound to fructose in a few seconds. The present technique was applied to determine the fructose content in beverages, honey, and watermelon with satisfactory results. Finally, the system could not only be applied in an aqueous solution with a spectrophotometer, but also be fabricated as a NBD-PQ-B/polyvinyl oxide (PEO) film by electrospinning for on-site food analysis simply with the assistance of a smartphone.

Food for Thought: Optical Sensor Arrays and Machine Learning for the Food and Beverage Industry

Arrays of cross-reactive sensors, combined with statistical or machine learning analysis of their multivariate outputs, have enabled the holistic analysis of complex samples in biomedicine, environmental science, and consumer products. Comparisons are frequently made to the mammalian nose or tongue and this perspective examines the role of sensing arrays in analyzing food and beverages for quality, veracity, and safety. I focus on optical sensor arrays as low-cost, easy-to-measure tools for use in the field, on the factory floor, or even by the consumer. Novel materials and approaches are highlighted and challenges in the research field are discussed, including sample processing/handling and access to significant sample sets to train and test arrays to tackle real issues in the industry. Finally, I examine whether the comparison of sensing arrays to noses and tongues is helpful in an industry defined by human taste.

A multi-wavelength cross-reactive fluorescent sensor ensemble for fingerprinting flavonoids in serum and urine

Flavonoids are a kind of natural polyphenols which are closely related to human health, and the identification of flavonoids with similar structures is an important but difficult issue. We herein easily constructed a powerful fluorescent sensor ensemble by using surfactant cetyltrimethylammoniumbromide (CTAB) encapsulating two commercially available fluorescent probes (F1 and F2) with multi-wavelength emission. Fluorescence measurements illustrate the present sensor ensemble exhibits turn-off responses to flavones and flavonols but ratiometric responses to isoflavones, owing to different FRET processes. The heat map and linear discriminant analysis (LDA) results show that this single sensor can effectively distinguish 6 flavonoids belong to three subgroups by collecting the fluorescence variation at four typical wavelengths. Moreover, it can be applied to identify different flavonoids even in biofluids like serum and urine, providing potential practical application.

Enhanced "Electronic Tongue" for Dental Bacterial Discrimination and Elimination Based on a DNA-Encoded Nanozyme Sensor Array

Bacterial infections are the second leading cause of death around the world, especially those caused by delayed treatment and misdiagnosis. Therefore, rapid discrimination and effective elimination of multiple bacteria are of great importance for improving the survival rate in clinic. Herein, a novel colorimetric sensor array for bacterial discrimination and elimination is constructed using programmable DNA-encoded iron oxide nanoparticles (IONPs) as sensing elements. Utilizing differential interactions of bacteria on DNA-encoded IONPs, 11 kinds of dental bacteria and 6 kinds of proteins have been successfully identified by linear discriminant analysis (LDA). Moreover, the developed sensing system also performs well in the quantitative determination of individual bacteria and identification of bacterial mixtures. More importantly, the practicability of this sensing strategy is further verified by precise differentiation of blind and artificial saliva samples. Furthermore, the sensor array is used for efficiently killing multiple bacteria, demonstrating great potential in clinical prophylaxis and therapy.

Synthesis of unique three-dimensional CoMn2O4@Ni(OH)2 nanocages via Kirkendall effect for non-enzymatic glucose sensing

Transition metal oxides / hydroxides, which have the advantages of wide distribution, low price, low toxicity, and stable chemical properties, have attracted much attention from researchers. Therefore, this work reports the construction of the unique CoMn2O4 nanocages assisted by the Kirkendall effect, and worm-like Ni(OH)2 nanoparticles were grown on the surface via hydrothermal method, the final product CoMn2O4@Ni(OH)2 nanocages were applied to construct efficient and sensitive non-enzymatic glucose electrochemical sensing. The stable three-dimensional hollow CoMn2O4 nanocages structure, not only can provide a wider specific surface area and more abundant active sites, its porous structure also can effectively inhibit the aggregation of nanoparticles, increase the ion diffusion path, shorten the electron transport distance, and improve the electrical conductivity. Loading Ni(OH)2 nanoparticles on the CoMn2O4 nanocages can increase catalytic sites, and further strengthen the electrocatalytic performance. Due to the good synergistic effect between CoMn2O4 and Ni(OH)2, CoMn2O4@Ni(OH)2 nanocages electrochemical sensor can achieve sensitive and rapid detection of trace glucose, with excellent linear range (8.5-1830.5 μM), low limit of detection (0.264 μM), high sensitivity of 0.00646 μA mM-1 cm-2, and outstanding repeatability. More importantly, the sensor has been successfully applied to the determination of blood glucose in human serum with good recoveries (95.64-104.3 %). This work provides a novel scheme for blood glucose detection and expands the application of transition metal oxides / hydroxides in the field of electrochemical sensing.

Sensitive and specific detection of saccharide species based on fluorescence: update from 2016

Increasing evidence supports the critical role of saccharides in various pathophysiological steps of tumor progression, where they regulate tumor proliferation, invasion, hematogenic metastasis, and angiogenesis. The identification and recognition of these saccharides provide a solid foundation for the development of targeted drug preparations, which are however not fully understood due to their complex and similar structures. In order to achieve fluorescence sensing of saccharides, extensive research has been conducted to design molecular probes and nanoparticles made of different materials. This paper aims to provide in-depth discussion of three main topics that cover the current status of the carbohydrate sensing based on the fluorescence sensing mechanism, including a phenylboronic acid-based sensing platform, non-boronic acid entities, as well as an enzyme-based sensing platform. It also highlights efforts made to understand the recognition mechanisms and improve the sensing properties of these systems. Finally, we present the challenge of achieving high selectivity and sensitivity recognition of saccharides, and suggest possible future avenues for exploration.

Molecular Level Sucrose Quantification: A Critical Review

Sucrose is a primary metabolite in plants, a source of energy, a source of carbon atoms for growth and development, and a regulator of biochemical processes. Most of the traditional analytical chemistry methods for sucrose quantification in plants require sample treatment (with consequent tissue destruction) and complex facilities, that do not allow real-time sucrose quantification at ultra-low concentrations (nM to pM range) under in vivo conditions, limiting our understanding of sucrose roles in plant physiology across different plant tissues and cellular compartments. Some of the above-mentioned problems may be circumvented with the use of bio-compatible ligands for molecular recognition of sucrose. Nevertheless, problems such as the signal-noise ratio, stability, and selectivity are some of the main challenges limiting the use of molecular recognition methods for the in vivo quantification of sucrose. In this review, we provide a critical analysis of the existing analytical chemistry tools, biosensors, and synthetic ligands, for sucrose quantification and discuss the most promising paths to improve upon its limits of detection. Our goal is to highlight the criteria design need for real-time, in vivo, highly sensitive and selective sucrose sensing capabilities to enable further our understanding of living organisms, the development of new plant breeding strategies for increased crop productivity and sustainability, and ultimately to contribute to the overarching need for food security.

Diboronate Fluorophore for the Measurement of l-Glucose and Other Carbohydrates and Its Interaction with Albumin

l-Glucose has recently been investigated as an artificial sweetener, but no facile method is established for the measurement of l-glucose. The commercial probe Eversense employs a fluorescent diboronate in a small device for the optical monitoring of d-glucose in people with diabetes. Being achiral, the Eversense probe should be able to detect l-glucose as well as native d-glucose, but the probe is designed for fixation under the skin, and our attempts to use the probe at laboratory conditions failed, as the probe was resetting when moved between compartments. We thus designed a water-soluble anthracene diboronate 8 similar to the fluorophore used in Eversense and found 8 to respond well to l-glucose and other carbohydrates and artificial sweeteners, thus enabling measurements of l-glucose with the limit of quantification of 12 μM. Notably, the fluorescent signal of diboronate 8 was largely quenched in buffers with the physiological concentration of albumin (0.5 mM), so the given analytical method would need more optimization to be useful for measuring l-glucose and other carbohydrates in blood samples. We suspect that other diboronate fluorophores from the literature may be similarly quenched if applied in the presence of albumin.

Printed 384-Well Microtiter Plate on Paper for Fluorescent Chemosensor Array in Food Analysis

We propose a printed 384-well microtiter paper-based fluorescent chemosensor array device (384-well microtiter PCAD) to simultaneously categorize and discriminate saccharides and sulfur-containing amino acids for food analysis. The 384-well microtiter PCAD required 1 μL/4 mm 2 of each well can allow high-throughput sensing. The device embedded with self-assembled fluorescence chemosensors displayed a fingerprint-like response pattern for targets, the image of which was rapidly captured by a portable digital camera. Indeed, the paper-based chemosensor array system combined with imaging analysis and pattern recognition techniques successfully not only categorized saccharides and sulfur-containing amino acids but also classified mono- and disaccharide groups. Furthermore, the quantitative detectability of the printed device was revealed by a spike recovery test for fructose and glutathione in a diluted freshly made tomato juice. We believe that the 384-well microtiter PCAD using the imaging analysis system will be a powerful sensor for multi-analytes at several categorized groups in real samples.