Microneedles for Continuous, Minimally Invasive Monitoring: A Technology Overview

Abstract

Microneedles are small piercing structures, with sizes in the micron-to-millimeter range, designed to penetrate painlessly the outer skin layer, known as stratum corneum, providing minimally invasive access to interstitial fluid (ISF), which enables the monitoring of biochemical parameters in real-time. This review covers recent progress to date in the area of electrochemical sensing using microneedles, and provides an overview of fabrication materials and processes, as well as applications. The main body of the review focuses on the fabrication of microneedle structures and their transformation into electrochemical biosensors for continuous monitoring. To this end, the main recognition elements and electrode functionalization ways are described, paying closer attention to aptamers and continuous aptamer-based sensing, whose importance, merits, and limitations are highlighted. In addition to covering the main current applications, the review discusses the future threats and opportunities of microneedle-based in vivo monitoring.