Screen‐printed electrodes are widely used in modern biosensor applications. The conditions under which screen‐printing takes place contribute to the electrical properties of the electrodes produced. This article describes a disposable carbon paste electrode that is used as the basis of an amperometric immunosensor incorporating the electroactive polymer polyaniline. The electrodes are manufactured using a semiautomated screen‐printing system. The conditions used for the screen‐printing of the carbon ink were investigated using physical methods such as scanning electron microscopy and cyclic voltammetry to establish how differences in the carbon surface translated into changes in the performance characteristics of the electrode. A process of electrochemical surface pretreatment was studied with a view to maximizing amperometric responses for subsequent enzyme and antibody‐based biosensor applications. Comparisons between the screen‐printed electrodes and glassy carbon electrodes are also made.

This work describes the development of an electrochemical immunosensor for the analysis of atrazine using recombinant single-chain antibody (scAb) fragments. The sensors are based on carbon paste screen-printed electrodes incorporating the conducting polymer polyaniline (PANI)/poly(vinylsulphonic acid) (PVSA), which enables direct mediatorless coupling to take place between the redox centres of antigen-labelled horseradish peroxidase (HRP) and the electrode surface. Competitive immunoassays can be performed in real-time using this separation-free system. Analytical measurements based on the pseudo-linear relationship between the slope of a real-time amperometric signal and the concentration of analyte, yield a novel immunosensor setup capable of regenerationless amperometric analysis. Multiple, sequential measurements of standards and samples can be performed on a single scAb-modified surface in a matter of minutes. No separation of bound and unbound species was necessary prior to detection. The system is capable of measuring atrazine to a detection limit of 0.1 ppb (0.1 g l −1). This system offers the potential for rapid, cost-effective immunosensing for the analysis of samples of environmental, medical and pharmaceutical significance.

Immunoanalytical techniques have found widespread use due to the characteristics of specificity and wide applicability for many analytes, from large polymer antigens, to simple haptens, and even single atoms. Electrochemical sensors offer benefits of technical simplicity, speed and convenience via direct transduction to electronic equipment. Together, these two systems offer the possibility of a convenient, ubiquitous assay technique with high selectivity. However, they are still not widely used, mainly due to the complexity of the associated immunoassay methodologies. A separation-free immunoanalytical technique is described here, which has allowed for the analysis of atrazine in real time and in both quasi-equilibrium and stirred batch configurations. It illustrated that determinations as low as 0.13 M (28 ppb) could be made using equilibrium incubation with an analytical range of 0.1-10 M. Measurements could be made between 1 and 10 mM within several minutes using a real-time, stirred batch method. This system offers the potential for fast, simple, cost-effective biosensors for the analysis of many substances of environmental, biomedical and pharmaceutical concern.

With lower limits of detection and increased stability constantly being demanded of biosensor devices, characterisation of the constituent layers that make up the sensor has become unavoidable, since this is inextricably linked with its performance. This work describe the optimisation and characterisation of two aspects of sensor performance: a conductive polymer layer (polyaniline) and the immobilised protein layer. The influence of the thickness of polyaniline films deposited electrochemically onto screen-printed electrode surfaces is described in this work in terms of its influence on a variety of amperometric sensor performance characteristics: time to reach steady state, charging current, catalytic current, background current and signal/background ratios. The influence of polymer film thickness on the conductivity and morphology of finished films is also presented. An electrostatic method of protein immobilisation is used in this work and scanning electron microscopy in conjunction with gold-labelled antibodies and back-scattered electron detection has enabled the direct visualisation of individual groups of proteins on the sensor surface. Such information can provide an insight into the performance of sensors under influence of increasing protein concentrations.

The widespread use of screen-printed electrodes in biosensor applications has meant that mass-production of disposable, inexpensive sensors has become feasible. However, the complexity of surface coatings that require difficult and time-consuming deposition procedures do not lend themselves to the same production conveniences. This article describes moves towards the development of an alternative to the electrochemical deposition of polyaniline on electrode surfaces for incorporation into an established sensor format. Chemical rather than electrochemical polymerization of the conducting polymer polyaniline enables a multitude of electrodes to be coated simultaneously, without the need for complex instrumentation. The aim of this work was to control the coating parameters such that a coating of polymer was deposited that displayed the optimum thickness and electrochemical properties of that previously optimized electrochemically. Deposition procedures were found to depend on the hydrophilicity of the underlying carbon paste electrode as well as on a variety of polymerization parameters.