Electrochemical techniques have great promise for low-cost miniaturised easy-to-use portable devices for a wide range of applications–in particular, medical diagnosis and environmental monitoring. Different techniques can be used for biosensing, with amperometric devices taking the central role due to their widespread application in glucose monitoring. In fact, glucose biosensing takes an approximately 70% share of the biosensor market due to the need for diabetic patients to monitor their sugar levels several times a day, making it an appealing commercial market.In this review, we present the basic principles of electrochemical biosensor devices. A description of the different generations of glucose sensors is used to describe in some detail the operation of amperometric sensors and how the introduction of mediators can enhance the performance of the sensors. Electrochemical impedance spectroscopy is a technique being increasingly used in devices due to its ability to detect variations in resistance and capacitance upon binding events. Novel advances in electrochemical sensors, due to the use of nanomaterials such as carbon nanotubes and graphene, are presented as well as future directions that the field is taking.

The discovery of the phenomena known as localized surface plasmon resonance (LSPR) has provided the basis for many research areas, ranging from materials science to biosensing. LSPR has since been viewed as a transduction platform that could yield affordable, portable devices for a multitude of applications. This review aims to outline the potential applications within developing countries and the challenges that are likely to be faced before the technology can be effectively employed.

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Enzymatic biofuel cells are ecofriendly power sources that can deliver μW−mW outputs from renewable substrates, but their stability is a major issue owing to enzyme fragility. The vast majority of reported biofuel cells can only generate power continuously for relatively short periods of time. Here we report a novel "solubilized enzymatic fuel cell (SEFC)" concept for continuous long-term operation. Avoiding surface immobilization techniques allows biocatalytic activity to be easily restored or replenished. The biofuel cell exploits freely diffusing enzymes and β-cyclodextrin-coated glyconanoparticles with entrapped quinone and thiazoline redox mediators, for mediated glucose and oxygen conversion. The cell was designed with permselective membranes to enable substrate and proton diffusion while trapping the enzymes and glyconanoparticles in separate compartments. The SEFC exhibited a peak power loss of only 26.3% after 7 days of continuous charge−discharge cycling at 50 μA; thus, SEFCs may be envisaged to power lab-on-a-chip devices for periods of several weeks.