Minimally invasive and continuous glucose monitoring sensor based on non-enzymatic porous platinum black-coated gold microneedles

Abstract

Individuals with diabetes can considerably benefit from continuous glucose monitoring (CGM). Addressing this challenge, a proof-of-concept for a pain-free CGM was presented based on a highly porous platinum black (Pt-black)-modified non-enzymatic microneedle electrode arrays (MNEAs). Porous Pt-black was electrodeposited on microneedle substrates using potentiometry by employing a charge density of -2.5 mA cm˗2. The surface of the porous Pt-black-modified microneedles (MNs) was optimally packed using Nafion (Nf) biocompatible ionomer. The dimensions of the fabricated microneedles were 650 µm × 110 µm × 150 µm in height, width, and thickness, respectively. The surface morphology of the modified MNs was studied using scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The microneedle sensor showed a wide glucose dynamic range (1 − 20 mM) in phosphate buffer saline (PBS) and artificial interstitial fluid (ISF) in-vitro with good sensitivities (PBS: 5.786 µA mM−1 cm−2, ISF: 4.380 µA mM−1 cm−2), detection limits (PBS: 10 µM, ISF: 22.5 µM), stability (2% lost at the end of 7 h), selectivity, reproducibility (2.32% RSD), and a response time of 2 s with good glucose recoveries in ISF (98%-102.5%). The device exhibited good stability (7 days) as a sensor in-vivo and lost its functional activity after 7 days due to electrode biofouling.