# Photonic Nanochains for Continuous Glucose Monitoring in Physiological Environment

## TL;DR

This paper introduces photonic nanochains that can continuously monitor glucose levels in a physiological environment, offering a noninvasive and color-based solution for diabetes management.

## Contribution

A new type of photonic nanochain is developed that can disperse and function in physiological conditions at pH 7.4 for glucose sensing.

## Key findings

- The PNCs change color from yellow-green to red as glucose concentration increases from 3.9 mM to 11.4 mM.
- The addition of PAA and AFPBA improves the hydrophilicity and glucose-sensing performance of the PNCs.
- The PNCs disperse well in artificial serum, showing potential for real-world CGM applications.

## Abstract

Diabetes is a common disease that seriously endangers human health. Continuous glucose monitoring (CGM) is important for the prevention and treatment of diabetes. Glucose-sensing photonic nanochains (PNCs) have the advantages of naked-eye colorimetric readouts, short response time and noninvasive detection of diabetes, showing immense potential in CGM systems. However, the developed PNCs cannot disperse in physiological environment at the pH of 7.4 because of their poor hydrophilicity. In this study, we report a new kind of PNCs that can continuously and reversibly detect the concentration of glucose (Cg) in physiological environment at the pH of 7.4. Polyacrylic acid (PAA) added to the preparation of PNCs forms hydrogen bonds with polyvinylpyrrolidone (PVP) in Fe3O4@PVP colloidal nanoparticles and the hydrophilic monomer N-2-hydroxyethyl acrylamide (HEAAm), which increases the content of PHEAAm in the polymer shell of prepared PNCs. Moreover, 4-(2-acrylamidoethylcarbamoyl)-3-fluorophenylboronic acid (AFPBA), with a relatively low pKa value, is used as the glucose-sensing monomer to further improve the hydrophilicity and glucose-sensing performances of PNCs. The obtained Fe3O4@(PVP-PAA)@poly(AFPBA-co-HEAAm) PNCs disperse in artificial serum and change color from yellow-green to red when Cg increases from 3.9 mM to 11.4 mM, showing application potential for straightforward CGM.