Muscle Fatigue Sensor
Researchers have taught a lactate biosensor to detect muscle strain of athletes even in extreme conditions
Scientists have created a biosensor that allows you to determine the overstrain harmful to muscles by the lactate content in sweat, even in extreme heat conditions. In the experiment, the authors managed to show that the concentration of the substance in the blood increases only over the working muscle, which means that the proposed biosensor really characterizes muscle fatigue. Such a development will allow detecting hypoxia in time — a reduced oxygen content in the athlete's body with too intense physical exertion. The results of the study, supported by a grant from the Russian Science Foundation (RNF), are published in the journal Analytical Chemistry (Daboss et al., Ultrastable Lactate Biosensor Linearly Responding in Whole Sweat for Noninvasive Monitoring of Hypoxia).
With heavy physical exertion, a person spends a huge amount of energy. It should be restored in the future due to glycolysis — the oxidation of glucose molecules to pyruvic acid. As a result of further processes, lactate is formed and accumulated, which cannot be neutralized due to the lack of resources and energy in the cell. This process leads not only to a decrease in the effectiveness of training, severe fatigue, but also to hypoxia — a state of acute lack of oxygen in individual organs, tissues or throughout the human body. It can cause irreversible changes and severe pathologies, which is why it is necessary to measure the amount of lactate in the body during intensive classes.
Scientists from Lomonosov Moscow State University (Moscow) a new biosensor has been developed, with the help of which it is possible to determine the lactate content in sweat. It is made on the basis of Prussian blue and nickel hexacyanoferrate and is built into a sweat flow collector connected to an ammeter or potentiometer. The mechanism of the system is the oxidation of lactate by the enzyme lactate oxidase to pyruvic acid and hydrogen peroxide. The latter is restored by Prussian blue to hydroxide ions, which are fixed by the device. It is by them that the initial lactate concentration is determined. This method is non-invasive, which makes monitoring the athlete's condition safe and comfortable. In addition, it allows you to calculate the concentration of lactate in the blood purely mathematically without additional manipulation.
In this work, scientists covered the biosensor with an additional ionomer membrane, which allowed to increase the stability of the device compared to the previous version. In addition, it has significantly expanded the range of detectable concentrations — from 0.5 to 100 mM, while the physiological lactate content in sweat is about 9-40 mM, and with heavy training can reach 40-80 mM. The concentration of the substance in the blood can be calculated by the formula.
The study involved athletes aged 20 to 30 years. Before the experiment, sweating was caused by the action of a solution of a certain chemical substance on the sweat glands — this is necessary to determine the initial lactate concentration. Then the volunteers performed physical exercises — squats. The devices were fixed on a working thigh muscle and a non-working forearm muscle. The values measured in sweat from different places on the body vary greatly, from which it can be concluded that the lactate concentration increases only in active muscles.
Next, the scientists analyzed the properties of the new biosensor both at room temperature and at a temperature raised to 60 ° C. The variants containing an ionomeric membrane were not affected by such changes in conditions, while the performance indicators of the remaining sensors (for example, without membranes) fell by almost half when heated. In addition, the scientists analyzed undiluted sweat and blood for the first time: the stability of the sensor remained constant for three hours.
"Currently, the creation of various biosensors is a very promising direction. Invasive methods of health monitoring, such as blood tests, remain the most reliable, however, due to their traumatism, they do not allow monitoring the concentration of a substance in the human body on a regular basis in everyday life. The highly sensitive sweat sensor developed by us, which has previously unattainable stability, can be used in various conditions for continuous monitoring of the athlete's condition," says Elena Daboss, Candidate of Chemical Sciences, senior researcher at the Faculty of Chemistry of Moscow State University.
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