Detection of glucose, galactose, and lactose in milk with a microdialysis-coupled flow injection amperometric sensor

Quantitative analysis of galactose using LDI-TOF MS based on a TiO2 nanowire chip

A novel method for quantifying galactose was developed to serve as a newborn screening test for galactosemia using laser desorption/ionization time-of-flight (LDI-TOF) mass spectrometry (MS) with a TiO2 nanowire chip. Herein, phosphate citrate buffer, serum, and dried blood spot (DBS) were employed for the quantitative analysis of galactose. To quantitatively analyze galactose, its reduction potential was used to oxidize o-phenylene diamine (OPD) into 2,3-diaminophenazine (DA), which were both detected using LDI-TOF MS with a TiO2 nanowire chip according to the concentration of galactose. The reproducibility and the interference of glucose were determined to demonstrate the applicability of this method. Moreover, mixtures of galactose, phenylalanine, and 17 α-OHP were analyzed to determine the interference induced by other biomarkers of metabolic disorders. The OPD oxidation of galactose was found to be selectively achieved under high-glucose conditions, similar to human blood, thereby showing good reproducibility. The intensities of the mass peaks of OPD and DA based on LDI-TOF MS with a TiO2 nanowire chip were linearly correlated in the galactose concentration range of 57.2–220.0 μg/mL (r2 = 0.999 and 0.950, respectively) for serum samples and 52.5–220.0 μg/mL (r2 = 0.993 and 0.985, respectively) for DBS after methanol precipitation/extraction. The enzyme immunoassay and LDI-TOF MS analysis results were statistically analyzed, and a mixture of phenylalanine, 17 α-OHP, and galactose was simultaneously investigated quantitatively at the cutoff level.

Nitrogen Doped Carbon Quantum Dots Modified by Lens culinaris β-Galactosidase as a Fluorescent Probe for Detection of Lactose

Nitrogen doped carbon quantum dots (NCQDs) were synthesized via hydrothermal route. The NCQDs are thermally and optically stable with high flouresence yield. For the synthesis of NCQDs, citric acid and urea was taken as carbon and nitrogen sources, respectively. The Transmission Electron Microscopy (TEM) of these quantum dots revealed nearly spherical shape and average size of 1.5 nm, which was calculated using Image J software. The quantum dots were also well-characterized using spectroscopic techniques such as FTIR, UV-Visible absorption and fluorescence. These synthesized and characterized dots were utilized for selective detection of lactose in Milli Q water. The bioprobe provide a wide linear range varying from (10.00-77.41) μM with limit of detection 11.36 μM and sensitivity equal to (0.0065 ± 0.0002) μM^-1. Graphical Abstract.

Sensors Based on Bio and Biomimetic Receptors in Medical Diagnostic, Environment, and Food Analysis

Analytical chemistry is now developing mainly in two areas: automation and the creation of complexes that allow, on the one hand, for simultaneously analyzing a large number of samples without the participation of an operator, and on the other, the development of portable miniature devices for personalized medicine and the monitoring of a human habitat. The sensor devices, the great majority of which are biosensors and chemical sensors, perform the role of the latter. That last line is considered in the proposed review. Attention is paid to transducers, receptors, techniques of immobilization of the receptor layer on the transducer surface, processes of signal generation and detection, and methods for increasing sensitivity and accuracy. The features of sensors based on synthetic receptors and additional components (aptamers, molecular imprinted polymers, biomimetics) are discussed. Examples of bio- and chemical sensors' application are given. Miniaturization paths, new power supply means, and wearable and printed sensors are described. Progress in this area opens a revolutionary era in the development of methods of on-site and in-situ monitoring, that is, paving the way from the "test-tube to the smartphone".

Selection of DNA aptamers against penicillin G using Capture-SELEX for the development of an impedimetric sensor

This paper describes for the first time the selection of aptamers selective to penicillin. Aptamers were selected using a specific process called Capture-SELEX (Systematic Evolution of Ligands by Exponential Enrichment). This technique is based on the selection of DNA aptamers using penicillin G in solution while the ssDNA library is fixed on a support. One aptamer showing a good affinity to penicillin was finally selected and tested in electrochemical sensor configuration, using electrochemical impedance spectroscopy as detection technique. The developed aptasensor allowed the detection of penicillin in a wide concentration range, comprised between 0.4 and 1000µgL^-1 Such performance was compatible with milk analysis, as the maximum residue limit tolerated in this matrix is 4µgL^-1. The selectivity of the developed sensor was also studied, showing that the sensor was also able to bind other beta-lactam antibiotics, although with a weaker affinity. Finally the sensor was used for detection of penicillin G in milk. It was shown that a simple sample treatment with isopropanol followed by filtration was sufficient to eliminate matrix effects, allowing the determination of penicillin in milk at concentrations compatible with legislation requirements.

Lactate and glucose measurement in subepidermal tissue using minimally invasive microperfusion needle

Knowing the concentrations of biological substances can help ascertain physiological and pathological states. In the present study, a minimally invasive microperfusion needle was developed for measuring the concentrations of biological substances in subepidermal tissue. The microperfusion needle has a flow channel with a perforated membrane through which biological substances from subepidermal tissue are extracted. Since this device uses a thin steel acupuncture needle as the base substrate, it has sufficient rigidity for insertion through the skin. The efficacy of the needle was examined by measuring lactate and glucose concentrations in mice. Lactate was injected intraperitoneally, and changes in lactate concentrations in subepidermal tissue over time were measured using the device. Lactate concentrations of blood were also measured as a reference. Lactate was successfully collected using the microperfusion needle, and the lactate concentration of perfused saline was significantly correlated with blood lactate concentration. Glucose solution was administered orally, and the glucose concentration of perfused saline was also correlated with blood glucose concentration. The newly developed microperfusion needle can be used for minimally invasive monitoring of the concentrations of biological substances.

Sampling, Dilution, and Loading Device-coupled High-Performance Liquid Chromatography Method for Successive On-line Analyses of Major Carbohydrate Products in Immobilized Cellulase Hydrolysate of Paper Cellulose

A device with direct sampling, dilution, and sample loading has been utilized to couple a vertically hanging immobilized cellulase bioreactor with a high-performance liquid chromatography system to make a successful on-line analysis of the 3 major carbohydrate products: glucose, xylose, and cellobiose in the cellulase hydrolysate. The coupled analysis system for successive on-line monitoring of the enzymatic hydrolysis of paper cellulose was stable over a period of 96 h. A comparative study involving 4 different quantification methods for the 3 carbohydrates was conducted. The internal standard calibration method with on-line dilution was observed to be the best procedure in terms of accuracy, precision, limit of detection, and systematic error reduction. With this method, the analysis for glucose had 99.9% accuracy, RSD below 2.4%, and a 2.1 ppm detection limit. Matrix matching was found important in the preparation of standard calibration curves with refractive index detection.

Isolation and characterization of the human monoclonal antibodies C10 in single-chain fragment variable (scFv) format to glucose oxidase from Aspergillus niger

Despite biotechnological and clinical applications very few monoclonal antibodies (MAbs) directed to the enzyme glucose oxidase, have been produced so far because of the heavy side effects of the immunization schedule for conventional MAb preparation. In contrast, the phage display method allows for the selection of monoclonal human antibody fragments against any antigens, including toxic proteins. Furthermore, cDNA sequences encoding selected antibody fragments are readily identified, facilitating various molecular targeting approaches. In order to obtain such human fragments recognizing glucose oxidase, we used the large synthetic ETH-2 library based on the principle of protein design. Phage displaying glucose oxidase reactive scFvs were obtained after three rounds of selection on glucose oxidase-coated immunotubes and subsequent amplification in TG1 E. coli cells. Eventually, one high reactive scFv clone was selected and further examined. The anti-glucose oxidase scFv C10 was found suitable for Western blot; Biacore analysis showed that the binding affinity of the glucose oxidase-reactive scFv is almost equal that of MAbs prepared with conventional hybridoma technology. Finally, the cDNA sequence of this human scFv may be exploited to generate bispecific antibodies to target in the tumor environment-specific toxic enzymatic reaction.