Bimetallic nanoparticles for highly sensitive colorimetric detection of glucose on paper

Abstract

Diabetes Mellitus is a metabolic disease that affects 422 million people worldwide and is directly responsible for 1.6 M deaths per year, with an increasing incidence especially in low – and middleincome countries. It is characterized by high-blood glucose levels that may lead to severe damages on the patients’ body tissues as blood vessels, eyes, heart, etc. The need to constantly monitor the blood glucose levels means a daily invasive blood collection that can be very stressful for the patient and frequently leads to a non-acceptance of the disease and the treatments. For this reason, glucose presence in other biofluids rather than blood is increasingly being studied, and it is possible to stablish a relation between the sweat glucose concentration values and the blood glucose levels in diabetic patients. Different enzymatic-based and electrochemical approaches have been taken for monitoring the low-glucose concentrations present in sweat, however most of these techniques are expensive and often relies on complex analysis of the results. For these reasons, in this work was developed a non-enzymatic paper-based colorimetric sensor for the detection of glucose in the range of hyperglycemic sweat glucose values (between 0.1 and 1 mM). The sensor is based on the glucose reduction of silver ions around disperse AuNPs adsorved on paper fibers, forming Au@Ag core-shell bimetallic NPs. The Ag-shell thickness increases with glucose concentration, resulting on colorimetric differences that may be quantified through digital analysis. Paper was utilized as substrate using the Lab-on-paper technology, where the deposition sites for glucose testing were defined by wax barriers diffused along the paper. Paper was chosen for being an abundant, biocompatible and low-cost material with good mechanical properties. Through RGB intensity measurement of the colorimetric results, a linear relation for glucose levels in a range from 0.12 to 1 mM was obtained.