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...

A sensitive and versatile methodology involving recordable compact disks as molecular screening surfaces and a standard optical CD/DVD drive as detector, is reported. Quantitative immunoanalysis, in microarray format, of a cancer marker (alpha-fetoprotein, AFP) and a selective herbicide (atrazine) on four types of audio-video disc was conducted. Enzyme or gold nanoparticle-labeled antibodies were used as tracers, forming a precipitate on the sensing disk surface. The principle of disk reading is based on capture of analog signals with the disk drive that were proportional to the darkness of the immunoreaction product. Detection limits for AFP (8.0 microg L(-1)) and for atrazine (0.04 microg L(-1)) were under the threshold needed to detect nonseminomatous testicular cancer, and below the maximum E.U. residue limit for drinking water, respectively. The described methodology improves the previous developments using CDs and highlights the enormous potential of immunoassay methods using standard audio-video disk surfaces in combination with the CD/DVD drive for clinical analysis, drug discovery, or high-throughput multiresidue screening applications.

One-dimensional photonic crystal slabs are periodic optical nanostructures that produce guided-mode resonance. They couple part of the incident light into the waveguide generating bandgaps in the transmittance spectrum, whose position is sensitive to refractive index variations on their surface. In this study, we present one-dimensional photonic crystal slab biosensors based on the internal nanogrooved structure of Blu-ray disks for label-free immunosensing. We demonstrated that this polycarbonate structure coated with a critical thickness of TiO2 generates guided-mode resonance. Its optical behavior was established comparing it with other compact disk structures. The results were theoretically calculated and experimentally demonstrated, all them being in agreement. The bioanalytical performance of these photonic crystals was experimentally demonstrated in a model assay to quantify IgGs as well as in two immunoassays to determine the biomarkers C-reactive protein and lactate dehydrogenase (detection limits of 0.1, 87, and 13 nM, respectively). The results are promising towards the development of new low-cost, portable, and label-free optical biosensors that join these photonic crystals with dedicated bioanalytical scanners based on compact disk drives.

A novel label-free biosensing approach based on bioreceptor networks patterned as diffractive gratings (biogratings) has been developed. Nanogrooved structures were used as optically active scaffolds for producing arrays of functional BSA biogratings on low energy surfaces by a water-assisted variant of microcontact printing. An analytical scanner, comprising a LightScribe compact disk drive, was developed to measure the diffraction patterns of these biogratings, thus allowing biointeractions to be quantitatively sensed in a multiplex and label-free fashion by means of diffraction efficiency changes. The approach was demonstrated by immunoassaying IgGs, reaching well-correlated responses with quantification and detection limits of 1.3 and 5.2 nM, respectively. These results provide appealing insights into cost-effective, portable, and scalable alternatives for designing new analytical technologies based on diffractive gratings of bioreceptors.