Another subcutaneous glucose indicator
The glowing glucose sensor is visible through the skinChemPort.Ru
Researchers from Japan have developed micro-sized beads, the intensity of the glow of which depends on the concentration of glucose in the medium in which they are located.
The glow of microbusins can be observed directly through the skin. This allows us to consider the new material as a possible alternative to those methods of monitoring glucose in the blood of diabetic patients, which are associated with the need for regular blood sampling for analysis.
Currently, sensors implanted into the patient's body to continuously determine the concentration of glucose in the blood are inconvenient to use, since they need to be connected to external power sources and monitors. As an alternative to sensors with the need to connect to systems outside the body, it is proposed to use fluorescent sensors, however, sensors of this type received so far have not emitted enough intensity for their light to pass through the skin and often turned out to be toxic to the body.
To solve the problems associated with the intensity of fluorescence, researchers from the Shoji Takeuchi group from the University of Tokyo have developed long-lasting fluorescent biologically compatible beads capable of continuous determination of blood glucose and do not require external power sources. The researchers synthesized a monomer containing fragments capable of glucose recognition, a fluorogenic fragment, spacers and fragments through which polymerization proceeds. The fluorescence intensity increases symbatically with an increase in glucose concentration.
The fluorescent glow of the beads is intense enough to be observed through the pale pink skin of a laboratory mouse.
The fluorescent indicator for determining glucose in the new sensor is a molecule that is a derivative of diboronic acid and anthracene. This molecule selectively and reversibly binds to glucose, the product of this interaction fluoresces without the help of additional reagents or enzymes. Long hydrophilic spacers and polymerization sites were introduced into the molecule, allowing the molecule to flexibly bind to the carrier substrate, thereby increasing the probability of binding to the glucose molecule. The last stage of work on the sensors was that the researchers received injectable fluorescent polyamide hydrogel beads, inside of which a monomer sensor was packed.
After injecting beads with a diameter of 130 microns into the ears of mice, the researchers observed how the intensity of fluorescent radiation passing through the skin of the ear changes, depending on the forced change in blood glucose. It was found that the intensity of fluorescence increases with an increase in the concentration of glucose in the blood and decreases with a decrease in the concentration of glucose. Takeuchi hopes that the system he developed will soon be able to find application for continuous determination of glucose levels in the body.
Raoul Kopelman, an expert on nanoscale chemical sensors for solving biomedical problems from the University of Michigan, notes that the work of Japanese colleagues is an elegant example of organic synthesis, which made it possible to incorporate an indicator for glucose determination into a biologically compatible microparticle. However, he emphasizes that before using the new systems in practice, a number of tasks have yet to be solved, including not only those related to clinical trials, but also the fact that diabetic patients will need to be convinced to use glowing indicators for glucose concentration.
Source: Proc. Natl. Acad. Sci. USA, 2010: Hideaki Shibata et al., Injectable hydrogel microbeads for fluorescence-based in vivo continuous glucose monitoringPortal "Eternal youth" http://vechnayamolodost.ru