Study reveals potential of paper sensors to measure glucose levels in tears
Diabetes mellitus is a metabolic condition characterized by insulin deficiency, resulting in elevated blood glucose levels (hyperglycemia) and leading to glucose intolerance in patients with diabetes.
This is fundamental. monitor your blood glucose levels several times a dayusually by pricking the patient’s fingers or forearms to obtain a small blood sample. However, this method has some limitations, such as callus formation on the fingers, discomfort, dilution of the sample when the patient applies pressure to the wound to obtain more blood, and excessive use of materials.
Over the years, various noninvasive methods of collecting or monitoring fluid have been studied. Some studies suggest creating a noninvasive method for measuring blood glucose levels. analysis of other physiological fluidssuch as saliva, interstitial fluid, sweat, urine or tears, the latter being one of the most promising for collecting information.
In this direction, a new study from the Autonomous University of Madrid (UAM), published in the journal Colloids and Surfaces B: Biointerfaces, has developed a new technique for the rapid, efficient and minimally invasive determination of glucose levels in humans.
tear fluid
Various studies have shown that most of the proteins present in human plasma are also present in the tear fluid. Some have found correlations between the concentrations of albumin, urea, glucose and cholesterol in the tears of semi-aquatic, terrestrial and marine reptiles. For this reason, this fluid has attracted the interest of the scientific community due to its potential for diagnosis and monitoring of various diseases such as cystic fibrosis, Parkinson’s disease, Alzheimer’s disease, cancer, sclerosis and diabetes.
In addition, one of the strengths is the ability to collect tear fluid. non-invasive method in a few secondsavoiding discomfort for the patient and allowing volumes from nanoliters to microliters to be obtained. However, the concentration of components such as glucose in tear fluid is significantly lower than in blood, which is one of the main problems in its use for monitoring body fluids. Therefore, the development of highly sensitive and specific sensors is crucial to improve the quality of life of patients with diabetes.
Nanoparticle sensors
Researchers claim that rare earth doped up-conversion nanoparticles (UCNPs) They stand out among fluorescent detectors used to measure blood glucose levels due to their unique optical properties. They have been shown to be able to detect changes in their optical properties depending on various factors such as pH, pressure, temperature or the presence of high-energy vibrational states. Therefore, they are an excellent choice for advanced sensor applications.
Another fundamental factor to consider when fabricating a sensor is the selection of a suitable substrate, as this directly affects its performance. Flexible substrates are particularly suitable for developing wearable and disposable sensors due to their special characteristics, including: The paper is characterized by mechanical flexibility, durability and porous structure.combined with its low cost and ease of functionalization. In addition, as the researchers explain in their paper, the use of paper sensors can have a significant impact on reducing the amount of consumables used in traditional blood glucose monitoring methods.
These nanoparticles were integrated into paper sensors as a first approach to develop novel enzyme-free and non-invasive D-glucose luminescence sensors.
In this work, the authors synthesized upconversion (UC) nanoparticles doped with Nd³⁺ ions acting as sensitizers and Er³⁺ ions acting as activators. These nanoparticles were integrated into paper sensors as a first approach to develop novel enzyme-free and noninvasive D-glucose luminescence sensors. The used nanoparticles exhibit intense upconversion emissions that correspond to the vibration levels of the OH group of D-glucose, causing changes in its red-green ratio, and this can be used as Luminescence based detection mechanism.
Detector potential
This study demonstrates the ability of 31 nm NaGdF₄ nanoparticles: 5% Er³⁺, 3% Nd³⁺ to D-glucose. Firstly, the interaction between the nanoparticles and D-glucose was investigated and evidence of this interaction was provided through various measurements, obtaining optimal results.
The detection mechanism of D-glucose was then tested, showing that the dispersion of these nanoparticles exhibited changes in the green band of upconversion radiation in the presence of D-glucose, confirming its detection capabilities. Subsequently, the nanoparticles were successfully coated onto paper substrates. different concentrations of D-glucose were used test the sensor by observing changes in the ratio of red and green nanoparticles for each concentration.
These results provided a calibration model for detection D-glucose concentrations from 0 to 200 mg/dL.Based on the emission changes of ErNd-NP, a paper-based enzyme-free luminescent sensor for detecting D-glucose with a detection limit of 22 mg/dL was successfully fabricated, which represents a breakthrough in future non-invasive tear fluid detection.
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