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High-density competitive indirect microimmunoassays were performed in both sides of compact discs by direct absorption of immunoreagents on polycarbonate surface, using gold-or enzyme-labeled immunoglobulins as tracers for displaying the immunoreaction. The operational principle is based on the use of a low-reflectivity compact disc as analytical platform that allows the reflection/transmission (30/70%) of the CD reader laser beam (λ 780 nm). The reflected light is used to scan the disc track keeping it in movement. The transmitted light is detected by a planar photodiode integrated on the CD drive. The variation of the optical transmission of the light caused by the immunoreaction products is related to the sample concentration. As a proof of concept, low abundant compounds, commonly used as pesticides, were detected in a 60-min total assay time, with a limit of detection ranging from 0.02 to 0.62 µg/L for 2,4,5-TP, chlorpyriphos, and metolachlor. The obtained results show the enormous prospective of compact discs in combination with CD players for multiresidue and drug discovery applications.The scope of microarrays has expanded impressively in recent years. As a rapidly maturing technology, microarrays pave the way for high-throughput analysis. 1 Conventional microimmunoassay array fabrication involves the immobilization of either coating conjugates (indirect format) or antibodies (direct format) on a solid support depending on the analytical needs. As microarray elements become smaller for larger numbers of simultaneous tests, alternative platforms with high optical quality, chemically derivatizable, and easy manipulation are of huge interest for analytical purposes.Different supports such as glass, silicon, and organic polymers have been used to develop high-density microarray assays. Among them, plastic discs have the advantage of large surface using the centrifugal force for fluid propulsion, performing different steps of the analytical process.The current analytical applications using plastic discs as supports can be classified in two groups. One employs discs about 2-mm thickness and 12-cm diameter to accomplish the development of microfluidic-based assays for proteins and nucleic acids, in which, essentially, different steps including sample treatment are involved. [2][3][4][5] The analytical results are mining through conventional detectors such as densitometers, photometers, fluorometers, etc., adapted to the circular geometry, including modified CD drives as laser scanning microscope. 6 The other group is based on the use of compact discs audio-video technology for management and reading the chemical results.Compact discs (CDs) are made from a 1.2-mm-thick disc of polycarbonate coated with a reflective layer of aluminum, silver, or gold protected by a lacquer resin with outstanding physical properties such as impact resistance, heat stability, large surface (94 cm 2 ), and good protein adsorption efficiency. The high optical quality of the polymeric materials used for CD and DVD audiovideo disc man...

Multiplexed microimmunoassays for five critical compounds were developed using a digital versatile disk (DVD) as an analytical support and detecting technology. To this end, coating conjugates were adsorbed on the polycarbonate face of the disk; a pool of specific antibodies, gold labeled secondary antibodies, and silver amplification were addressed for developing the assays. The detection principle is based on the capture of attenuated analog signals with the disk drive that were proportional to optical density of the immunoreaction product. The multiplexed assay achieved detection limits (IC10) of 0.06, 0.25, 0.37, 0.16, and 0.10 microg/L, sensitivities of (IC50) 0.54, 1.54, 2.62, 2.02, and 5.9 microg/L, and dynamic ranges of 2 orders of magnitude for atrazine, chlorpyrifos, metolachlor, sulfathiazole, and tetracycline, respectively. The features of the methodology were verified by analyzing natural waters and compared with reference chromatographic methods, showing its potential for high-throughput multiplexed screening applications. Analytes of different chemical nature (pesticides and antibiotics) were directly quantified without sample treatment or preconcentration in a total time of 30 min with similar sensitivity and selectivity to the ELISA plate format using the same immunoreagents. The multianalyte capabilities of immunoassaying methods developed with digital disk and drive demonstrated the competitiveness to quantify targets that require different sample treatment and instrumentation by chromatographic methods.

A valid solution for micro-analytical systems is the selection of a compatible 10

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