An integrated device for fast and sensitive immunosuppressant detection.

The present paper describes a compact point of care (POC) optical device for therapeutic drug monitoring (TDM). The core of the device is a disposable plastic chip where an immunoassay for the determination of immunosuppressants takes place. The chip is designed in order to have ten parallel microchannels allowing the simultaneous detection of more than one analyte with replicate measurements. The device is equipped with a microfluidic system, which provides sample mixing with the necessary chemicals and pumping samples, reagents and buffers into the measurement chip, and with integrated thin film amorphous silicon photodiodes for the fluorescence detection. Submicrometric fluorescent magnetic particles are used as support in the immunoassay in order to improve the efficiency of the assay. In particular, the magnetic feature is used to concentrate the antibody onto the sensing layer leading to a much faster implementation of the assay, while the fluorescent feature is used to increase the optical signal leading to a larger optical dynamic change and consequently a better sensitivity and a lower limit of detection. The design and development of the whole integrated optical device are here illustrated. In addition, detection of mycophenolic acid and cyclosporine A in spiked solutions and in microdialysate samples from patient blood with the implemented device are reported.

Size does matter! Label-free detection of small molecule-protein interaction.

This review is focused on methods for detecting small molecules and, in particular, the characterisation of their interaction with natural proteins (e.g. receptors, ion channels). Because there are intrinsic advantages to using label-free methods over labelled methods (e.g. fluorescence, radioactivity), this review only covers label-free techniques. We briefly discuss available techniques and their advantages and disadvantages, especially as related to investigating the interaction between small molecules and proteins. The reviewed techniques include well-known and widely used standard analytical methods (e.g. HPLC-MS, NMR, calorimetry, and X-ray diffraction), newer and more specialised analytical methods (e.g. biosensors), biological systems (e.g. cell lines and animal models), and in-silico approaches.

Label-free optical biosensor for detection and quantification of the non-steroidal anti-inflammatory drug diclofenac in milk without any sample pretreatment.

A label-free optical biosensor for detection and quantification of diclofenac in bovine milk has been developed. This was achieved by using reflectometric interference spectroscopy as detection method. In a first step, the immunosensor was developed and optimised in buffer concerning sensitivity, selectivity, stability and reproducibility. By comparing recovery rates­not only the good intra- but also the good inter-chip­reproducibility could be proven. Consequently, the assay was transferred in the more complex matrix milk. By utilising an optimised surface modification and evaluation method, matrix effects could successfully be prevented or circumvented. As a result, the developed immunosensor does not need sample pretreatment at all. By obtaining a limit of detection of 0.112 µg L(−1) (0.108 µg kg(−1)), the capability of the developed biosensor is comparable or better than those of standard detection methods. Moreover, the presented biosensor reaches the range of the maximum residue limit (0.1 µg kg(−1)) set by the European Union. Thus, for the first time, diclofenac was successfully quantified at relevant levels in milk by using an optical biosensor.

A biomimetic sensor surface to detect anti-ß2-glycoprotein-I antibodies as a marker for antiphospholipid syndrome.

A biomimetic sensor has been developed, that allows for quantification of autoantibodies related to the antiphospholipid syndrome (APS). Autoantibodies directed against the ß(2)-glycoprotein-I (ß(2)GP-I) are known as the best markers for diagnosis of APS, however, detection of such antibodies is still a challenge. The epitopes of ß(2)GP-I are exposed upon binding to negatively charged membranes. The surface of the sensor chips was therefore modified with such type of membranes, on which ß(2)GP-I molecules were subsequently immobilized as recognition elements. Using the label-free method, reflectometric interference spectroscopy, it was possible to quantify anti-ß(2)GP-I antibodies and to calibrate the sensor chip in buffer. A mild regeneration procedure allows for many consecutive measurements without stripping off the membrane in between.