Methylglyoxal - An emerging biomarker for diabetes mellitus diagnosis and its detection methods.

Diabetes Mellitus (DM) is one among the supreme metabolic issues observed in history since 3000 BCE and has gained much interest recently due to the increasing number of diabetic cases every year. Glucose is considered as the most iconic biomarker for diabetes detection, and fluctuations in its levels are related to different stages of DM. However, methylglyoxal (MG) is evolving as a diabetes marker since it plays a significant role in biological processes Apart from DM, MG causes several metabolic irregularities like hypertension, neuropathy, nephropathy, oxidative stress. Besides, MG is a predominant precursor of advanced glycation end products (AGEs), which result in protein dysfunction, glycation of vascular tissues and aging. In this background, detection of MG has much importance, and the design of smart models is desirable. MG formation, detoxification, and its glycation effects have paved the way for the development of detection strategies which are described in detail here. The direct and indirect methods of MG measurement have been established in the past. At present, techniques like high-performance liquid chromatography, gas chromatography-mass spectrometry, enzyme-linked immunosorbent assay, capillary electrophoresis, electrochemical biosensors have been used to quantify MG present in the samples. Here, we have tried to correlate the function of MG and detection strategies to explain the major challenges posed towards implementation of easy, efficient and accurate standardization.

Fabrication of an electrochemical biosensor with ZnO nanoflakes interface for methylglyoxal quantification in food samples.

Increased consumption of fried foods such as grilled chicken contains elevated levels of methylglyoxal (MG), which is associated with diabetes mellitus. Hence, in this work, glyoxalase 1(GLO 1) based, zinc oxide (ZnO) flakes interfaced mediator free electrochemical biosensor was developed to detect MG in grilled chicken. ZnO flakes were synthesized by direct precipitation method. X-ray diffractometer and field emission scanning electron microscope were used to study the structural and morphological characteristics of ZnO flakes. The immobilization of GLO 1 on Pt/ZnO flakes modified electrode was confirmed by Fourier transform infrared spectroscopy. Cyclic voltammetric and amperometric studies were carried out using Pt/ZnO flakes/GLO 1 working electrode. The developed biosensor exhibited linear range of 0.6-2.0 µM, sensitivity of 0.281 µA µM-1, LOD of 9 nM with a response time of <4 s and shelf life of 18 days (89%).

Fabrication of Electrochemical Biosensor with ZnO-PVA Nanocomposite Interface for the Detection of Hydrogen Peroxide.

Hydrogen peroxide (H2O2) is considered to be highly toxic and its increased concentration in human body may lead to diseases like alzheimer's, parkinson's, cardiovascular, tumor and cancer. Hence, there is an increasing demand for the detection of H2O2 in human blood serum. In this context, an electrochemical sensor was developed using zinc oxide-polyvinyl alcohol (ZnO-PVA) nanocomposite as a nano-interface. The fabricated Au/ZnO-PVA/CAT/Chitosan bio-electrode exhibited a well-defined redox peak with anodic and cathodic peak potential of -0.408 V and 0.259 V for Fe(III):Fe(II) and H2O2:1/2 O2 redox couples respectively. The developed biosensor exhibited a linear range of 1 µM-17 µM with a sensitivity of 210.49 µA µM-1 cm-2, response time of less than 1 s, limit of detection of 9.13 nM and a limit of quantification of 30.13 nM. The developed bio-electrode showed a Michaelis-Menten constant (KM) of 0.39 µM and dry stability of 93% up to 20 days. The obtained biosensor was successfully utilized to determine the H2O2 concentration in human blood serum sample.

A non-enzymatic two step catalytic reduction of methylglyoxal by nanostructured V2O5 modified electrode.

Methylglyoxal (MG) is a predominant precursor for advanced glycation end products (AGEs) due to its protein glycation reactions, which are the major causes of diabetic complications. MG is explored as a significant biomarker towards the prediction of diabetic complications. With this background, a non-enzymatic electrochemical biosensor has been developed to detect MG in human blood plasma samples. Microwave synthesized V2O5 nanoplates were used as interface material in the fabrication of modified gold (Au) working electrode for electrochemical MG biosensor. Orthorhombic crystal structured V2O5 with an oxidation state of +5 exhibited specific MG sensing performance. Cyclic voltammetry and amperometry studies confirmed the electrocatalytic nature of V2O5 nanoplates modified Au electrode in the detection of MG. Non-enzymatic V2O5 modified Au electrode showed a sensitivity of 4.519µAµM-1 with a linear range of 3-30µM, limit of detection (LOD) of 0.24µM, limit of quantification (LOQ) of 0.80µM and a response time less than 8s towards MG. The lifetime and percentage recovery of the sensor was found to be 25 days (90%) and 102.5-108.7% respectively.

Fabrication of electrochemical biosensor with vanadium pentoxide nano-interface for the detection of methylglyoxal in rice.

Increased consumption of raw and par-boiled rice results in the formation of methylglyoxal (MG) at higher concentration and leads to complications in diabetic patients. Highly sensitive electrochemical biosensor was developed using glutathione (GSH) as a co-factor with vanadium pentoxide (V2O5) as a nano-interface for MG detection in rice samples. The Pt/V2O5/GSH/Chitosan bioelectrode displayed two well-defined redox peaks in its cyclic voltammograms for MG reduction. This occurred as two electron transfer process where MG gained two electrons from oxidized glutathione disulfide and formed hemithioacetal. The current density response of the fabricated bioelectrode was linear towards MG in the concentration range of 0.1-100 µM with the correlation coefficient of 0.99, sensitivity of 1130.86 µA cm-2 µM-1, limit of detection of 2 nM and response time of less than 18 s. The developed bioelectrode was used for the detection of MG in raw and par-boiled rice samples.

Evaluation of Inhibition Efficiency for the Detection of Captan, 2,3,7,8-Tetrachlorodibenzodioxin, Pentachlorophenol and Carbosulfan in Water: An Electrochemical Approach.

A novel bio-analytical method has been devised based on the change in catalytic activity of acetylcholinesterase (AChE) enzyme induced by captan, carbosulfan, 2,3,7,8-tetrachlorodibenzodioxin (TCDD) and pentachlorophenol (PCP) for the investigation of inhibition efficiency and sensitivity using Pt/ZnO/AChE/Chitosan bioelectrode. The inhibition curves of captan, carbosulfan, TCDD and PCP were similar to Michaelis-Menten curve. TCDD held the minimum inhibitor Michaelis-Menten constant ([Formula: see text]) value (10.2 nM) in comparison with PCP (10.9 nM), carbosulfan (14.5 nM) and captan (7.9 × 10(3) nM). The maximum inhibition of AChE enzyme by captan was about 100 %, which was much higher than that of TCDD (72.7 %), PCP (68.1 %) and carbosulfan (47.7 %). The calculated theoretical sensitivity was in the order of TCDD > PCP > carbosulfan > captan. Comparing with TCDD (35.3 %), PCP (47.8 %) and carbosulfan (20.9 %), only the inhibition efficiency of captan (55.0 %) was the maximum. The developed bioelectrode exhibited high recovery and low relative standard deviation in local tap water samples.