Sensitive and specific DNA biomarker detection is critical for accurately diagnosing a broad range of clinical conditions. However, the incorporation of such biosensing structures in integrated microfluidic devices is often complicated by the need for an additional labelling step to be implemented on the device. In this review we focused on presenting recent advances in label-free DNA biosensor technology, with a particular focus on microfluidic integrated devices. The key biosensing approaches miniaturized in flow-cell structures were presented, followed by more sophisticated microfluidic devices and higher integration examples in the literature. The option of full DNA sequencing on microfluidic chips via nanopore technology was highlighted, along with current developments in the commercialization of microfluidic, label-free DNA detection devices.

More than 783 million people worldwide are currently without access to clean and safe water. Approximately 1 in 5 cases of mortality due to waterborne diseases involve children, and over 1.5 million cases of waterborne disease occur every year. In the developing world, this makes waterborne diseases the second highest cause of mortality. Such cases of waterborne disease are thought to be caused by poor sanitation, water infrastructure, public knowledge, and lack of suitable water monitoring systems. Conventional laboratory-based techniques are inadequate for effective on-site water quality monitoring purposes. This is due to their need for excessive equipment, operational complexity, lack of affordability, and long sample collection to data analysis times. In this review, we discuss the conventional techniques used in modern-day water quality testing. We discuss the future challenges of water quality testing in the developing world and how conventional techniques fall short of these challenges. Finally, we discuss the development of electrochemical biosensors and current research on the integration of these devices with microfluidic components to develop truly integrated, portable, simple to use and cost-effective devices for use by local environmental agencies, NGOs, and local communities in low-resource settings.

The evolution of label‐free electrochemical biosensors has revolutionized the field of analytical detection by enabling rapid, direct, and sensitive detection of a wide range of analytes. Electrochemical impedance spectroscopy (EIS) provides mechanistic insight into the interfacial changes occurring at the electrode/electrolyte interface, thereby enabling real‐time monitoring. Direct detection of molecular binding events at the electrode interface is made possible by sensing measurable shifts in interfacial impedance characteristics. Despite their versatility, the commercial translation of EIS‐enabled biosensors has been hindered by challenges in achieving robust sensitivity, specificity, and reproducibility. Recent progress in the field, including integration of nanoengineered electrode materials and novel biorecognition elements, has addressed some of these limitations, resulting in marked improvements in EIS‐based biosensor performance. This review discusses the mechanistic principles underlying label‐free EIS biosensing and highlights recent developments in electrode surface modification and sensor architecture. It also explores the integration of novel biorecognition elements and describes how their impact on sensor performance may be assessed. Current limitations and future directions for the application of EIS‐enabled sensors in clinical diagnostics, environmental analysis, and food safety monitoring are also considered.

Printed circuit boards (PCBs) offer a promising platform for the development of electronics-assisted biomedical diagnostic sensors and microsystems. The long-standing industrial basis offers distinctive advantages for cost-effective, reproducible, and easily integrated sample-in-answer-out diagnostic microsystems. Nonetheless, the commercial techniques used in the fabrication of PCBs produce various contaminants potentially degrading severely their stability and repeatability in electrochemical sensing applications. Herein, we analyse for the first time such critical technological considerations, allowing the exploitation of commercial PCB platforms as reliable electrochemical sensing platforms. The presented electrochemical and physical characterisation data reveal clear evidence of both organic and inorganic sensing electrode surface contaminants, which can be removed using various pre-cleaning techniques. We demonstrate that, following such pre-treatment rules, PCB-based electrodes can be reliably fabricated for sensitive electrochemical biosensors. Herein, we demonstrate the applicability of the methodology both for labelled protein (procalcitonin) and label-free nucleic acid (E. coli-specific DNA) biomarker quantification, with observed limits of detection (LoD) of 2 pM and 110 pM, respectively. The proposed optimisation of surface pre-treatment is critical in the development of robust and sensitive PCB-based electrochemical sensors for both clinical and environmental diagnostics and monitoring applications.

A novel cobalt-based compound, [Co(GA) ₂ (aqphen)]Cl, was characterized for electrochemical signal amplification to detect DNA relevant to E. coli by utilizing its characteristic redox-active and intercalative properties.