A Graphene-Based Enzymatic Biosensor Using a Common-Gate Field-Effect Transistor for L-Lactic Acid Detection in Blood Plasma Samples

Abstract

Lactate is an important organic molecule that is produced in excess during anaerobic metabolism when oxygen is absent in the human organism. The concentration of this substance in the body can be related to several medical conditions, such as hemorrhage, respiratory failure, and ischemia. Herein, we describe a graphene-based lactate biosensor to detect the concentrations of L-lactic acid in different fluids (buffer solution and plasma). The active surface (graphene) of the device was functionalized with lactate dehydrogenase enzyme using different substances (Nafion, chitosan, and glutaraldehyde) to guarantee stability and increase selectivity. The devices presented linear responses for the concentration ranges tested in the different fluids. An interference study was performed using ascorbic acid, uric acid, and glucose, and there was a minimum variation in the Dirac point voltage during detection of lactate in any of the samples. The stability of the devices was verified at up to 50 days while kept in a dry box at room temperature, and device operation was stable until 12 days. This study demonstrated graphene performance to monitor L-lactic acid production in human samples, indicating that this material can be implemented in more simple and low-cost devices, such as flexible sensors, for point-of-care applications.

Microfluidic sensors based on two-dimensional materials for chemical and biological assessments

“…This work proved graphene's ability to monitor L-lactic acid accumulation in human samples, implying that this material might be employed in more basic and low-cost equipment, such as flexible sensors for POC 129 .…”

“…This work proved graphene's ability to monitor L-lactic acid accumulation in human samples, implying that this material might be employed in more basic and low-cost equipment, such as flexible sensors for POC. 129 Cystatin C (Cys C) is a 13 kDa protein made up of a single 120-amino-acid polypeptide chain. 130 This serum's abnormally high levels have recently been revealed to be a prognostic sign for various conditions, including neurological problems, cardiovascular disorders, and cancer.…”

Critical review of polymer and hydrogel deposition methods for optical and electrochemical bioanalytical sensors correlated to the sensor’s applicability in real samples

“…It is best suited for coating of a small and defined area, because for larger areas, controlling thickness, porosity, and uniformity of the film is more difficult [34]. The general process includes the mixing of recognition elements such as enzymes [8,9,35,36], DNA derivatives [10,37], or probes such as fluorescent dyes, luminophores [38], or nanoparticles [39,40] with an evaporable solvent and a binder (e.g., hydrogels, polymers, or cross-linkers like glutaraldehyde), followed by application of this cocktail to the desired surface. In addition to the cocktail composition and surface conditions, drying time, annealing temperature, and the applied volume are contributing factors toward the final homogeneity and morphology of the deposited material.…”

A photonic crystal fiber–based fluorescence sensor for simultaneous and sensitive detection of lactic acid enantiomers

“…While the normal level of d -LA is only ~ 1.0% of l -LA, the elevated d -LA level in the blood and urine, which may be caused by an overproduction of intestinal bacteria, or in cases of infection, ischemia, or traumatic shock, would ultimately result in metabolic acidosis and lead to severe neurological symptoms [ 12 , 13 ]. On the other hand, a high l -LA level can also lead to the drop in blood pH value in the body, and even acidosis in severe cases [ 14 , 15 ]. For coronavirus disease 2019 (COVID-19), LA levels in blood have been proposed as an important indicator for its stratification, therapeutic effect evaluation, and prognosis estimation [ 16 ].…”