Tissue-Integrated Sensitive Glucose Nanosenor to Revolutionize Diabetes Management

The key task of monitoring blood glucose levels is typically accomplished through the use of enzyme glucose oxidase (GOx)-based electrochemical sensors. Despite their effectiveness, these sensors produce the toxic byproduct hydrogen peroxide and also require cumbersome electrical components and batteries, complicating the development of continuous, implantable monitoring devices. An alternative approach involves single-wall carbon nanotubes (SWCNTs), which, when excited by light, emit near-infrared fluorescence that penetrates tissue and can be captured by non-invasive bioimaging techniques. However, integrating GOx with SWCNTs to create nanosensors is challenging as the typical method for attaching molecules to SWCNTs, sonication, deactivates the GOx molecules.

To address these challenges, scientists at the University of California, Berkeley (Berkeley, CA, USA) have innovated a battery-free fluorescent nanosensor that combines SWCNTs with an inactive form of GOx. This groundbreaking design allows for the continuous, reversible, and non-invasive bioimaging of glucose levels in body fluids and tissues. This development overturns the prevailing belief that GOx-based sensors require active GOx for effective glucose sensing. Through sonication, the team produced GOx-loaded SWCNT sensors capable of accurately and selectively detecting glucose in various mediums like serum, plasma, and even within mouse brain tissue.

According to the researchers, inactive GOx enzyme can still bind to glucose without converting it, and binding alone proved sufficient to modulate the fluorescence signal. In order to be completely independent of GOx activity, the researchers also created a GOx enzyme that even lacked the reactive group for glucose conversion. The resulting apo-GOx-SWCNT sensor was able to detect glucose in body fluids and mouse brain slices as reliably as the original conjugate of SWCNT and natural GOx. The researchers suggest that the use of inactive GOx molecules offers key advantages. For instance, it is possible to simplify the manufacturing process of the GOx-SWCNT nanosensors by utilizing sonication as an effective preparation step. Additionally, since the analyte is not consumed by the enzyme reaction, there are no toxic byproducts produced, and the measurements are intrinsically reversible, enabling the non-invasive continuous monitoring of glucose in tissue fluids.

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University of California, Berkeley