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Acute myocardial infarction (AMI) is the world's leading cause of mortality and morbidity. Therefore, quick and reliable diagnostics of AMI is extremely critical. Compared to the traditionally used central laboratory tests (CLT), which can be time-consuming and expensive, point-of-care testing (POCT) for AMI-indicative cardiac markers provides a convenient means for rapid diagnostic assays to be performed at the site of patient care delivery. In this article, the etiology and diagnosis of AMI are introduced, and some typical cardiac markers and their clinical applications are reviewed. Furthermore, the various POC cardiac marker devices that are currently available, the benefits of using cardiac marker POC assays, and challenges that cardiac marker POCT are facing are also discussed.

A biosensor has been designed for measuring plasma fibrinogen concentrations based on an enzyme kinetic model. The values obtained correspond linearly to those of a clinical method but have a higher sensitivity within the normal range of fibrinogen. By using the disposable biosensor technology, this method is easy to follow, quick (within 2 min) and precise (with coefficients of variation to be as low as below 5%) and requires only a small amount of plasma sample (50 microl). This biosensor technology also holds potential for use in point-of-care diagnostics.

A.c. impedance spectroscopy has been used to study the adsorption of a protein (bovine serum albumin) on calcium-ion-selective electrode, poly(vinyl chloride) (PVC) membranes. Protein adsorption reduced the exchange of ions across the membrane—solution interface as shown by the presence of a second semicircle in the spectra. Adsorption is fast and its extent smaller if a high ratio of ligand to calcium ion is used in the membrane. Protein can be removed from the surface by successive washing.

The properties of calcium ion-selective, polyvinyl chloride membranes have been determined from ac impedance spectra. The bulk membrane resistance does not stabilize before 2 days of contact with aqueous solutions, suggesting that the usually adopted overnight conditioning period is too short. The effect of using different plasticisers and ligand/calcium ion ratios in the membrane permits optimization of membrane composition for the chosen ionophore ETH1001.

Two-dimensional (2D) and three-dimensional (3D) patternable conductive structures such as entire neural stimulation circuit are created by using metal nanoparticles and a nanopowder molding process. Fabricated structures retain a height-to-width ratio of up to 10:1. The described process is able to fuse the stimulating electrode, connection trace, and contact pad into one continuous, integrated structure where different sections can have different heights, widths, and shapes. The batch process is suitable for mass production, and the fabricated electrode is robust and very flexible. Additionally, the completed structure can be packed onto a biocompatible flexible substrate, such as poly-dimethylsiloxane, parylene, and polyimide as well as other temperature-sensitive or vacuum-sensitive materials at room temperature which make it more suitable for biomedical applications. Experimental data show that the electrodes and wires have about the same electrical resistivities as their bulk materials and desirable electrochemical properties, including low impedance. The nanoscale feature on the electrode surface enhanced the interface and contact quality between electrode and bio-substrate that led to better electrochemical performance.

Electrochemically modified screen-printed carbon electrode (SPCE) has been prepared by electrodepositing nickel hexacyanoferrate(III) (NiHCF) onto the electrode surface using cyclic voltammetry (CV). The performance of NiHCF-SPCE sensor was characterized and optimized by controlling several operational parameters. The NiHCF film has been proven to remain stable after CV scanning from 0 to +1.0 V vs. Ag/AgCl in the pH range of 3 to 10 and is re-useable. The most favourable supporting electrolyte solution exhibiting the optimum electroanalytical performance of the NiHCF-SPCE sensor was found to be 0.2 mol/L sodium nitrate. The electrochemical response toward ascorbic acid (AA) and H2O2 in 0.2 mol/L sodium nitrate solution was studied by using CV and the results showed that both analytes were electrocatalytically oxidized at approximately +0.4 V, while H2O2 also revealed a reduction signal at -0.8 V vs. Ag/AgCl. The NiHCF-SPCE sensor exhibited highly linear response for AA and H2O2 in the examined concentration range from 5.0x10-5 to 1.5x10-3 mol/L and from 2.0x10-5 to 1.0x10-3 mol/L (at +0.4 V), with the correlation coefficients of 0.999 and 0.998, respectively. The reproducibility of the NiHCF-SPCE sensor was followed for the determination of AA by using four individual electrodes, and the relative standard deviation of CV peak currents varied between 0.9 % and 2.2 %. The proposed NiHCF-SPCE has been shown to be a very attractive electrochemical sensor for AA and H2O2, also in a view of inexpensive mass production of disposable single-use sensors. The NiHCF-SPCE sensor was tested by measuring AA in multivitamin tablets, with recoveries obtained between 94.4 % and 108.2 % (n=5).

Thin film gold electrodes on flexible PTFE substrates are produced for medical implantation. The electrical interface impedance of the electrodes is measured in vitro as a function of surface roughness of the gold as quantified using atomic force microscopy. Alternating current impedance measurements show a linear relationship between the reactive component of the impedance and the surface roughness. Surface features below a few tens of nanometres root mean square deviation from the average surface height are shown to result in a reduction in interface impedance and improved matching to a 1% NaCl solution. The surface roughness of the gold is controlled using an electrolytic etch in an NaCl solution which causes electropitting and therefore allows the electrical characteristics of the interface to be influenced.

Thin film gold electrodes on flexible Polytetrafluoroethylene (PTFE) substrates are produced for medical implantation. The electrical interface impedance of the electrodes is measured in vitro as a function of surface roughness of the gold as quantified using atomic force microscopy. Alternating current (AC) impedance measurements show a linear relationship between the reactive component of the impedance and the surface roughness. Surface features below 42 nm root mean square deviation from the average surface height are shown to result in a reduction in interface impedance and improved impedance matching to a 1% NaCl solution. The surface roughness of the gold is controlled using an electrolytic etch in a NaCl solution allowing the electrical characteristics of the interface to be influenced. Plasma modification of the PTFE substrate is seen to increase the surface energy by changing the chemical nature of the polymer and lead to enhanced adhesion of the gold layers. Applications of such techniques are expected to improve the current design of physiological signal sensors as well as enhance the reproducibility of biosensing devices.