Microimmunoanalysis on Standard Compact Discs To Determine Low Abundant Compounds

Abstract

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...

Discerning Trends in Multiplex Immunoassay Technology with Potential for Resource-Limited Settings

“…In addition, several attempts have been made to use optical scanning of spinning disks as the basis for immunoassays. A group in Madrid has been developing technology based on standard disks (33)(34)(35)(36)(37)(38). In the most recent version (38 ), 6 environmentally related small molecules are determined in a competition assay with haptens directly linked to the plastic surface, and colloidal gold antibody is used for label with silver intensification.…”

Invited Review Article: Review of centrifugal microfluidic and bio-optical disks

“…33,80,81 These approaches require labels to bring the molecular binding into a strong light scattering regime. Gold nanoparticles and precipitates 80,82,83 have been used for this purpose, and particle labels also have been used to catalyze autometallography to boost the contrast, 32,78,80,81,84,85 similar to silver staining on a Western blot. An alternative colorimetric approach uses calcium-sensitive film on the disk that changes color upon uptake of calcium 86,87 but with significantly lower sensitivity than the silver staining approach.…”

“…91 Assays that have been performed on digital CD/DVD platforms include both immunoassays and oligonucleotide hybridization assays. The immunoassays were competitive inhibition immunoassays for hydroxyatrazine, carbaryl, and molinate, 73 the neurotoxin chlorpyriphos with a limit of detection ͑LOD͒ near 300 pg/ml, 78 AFP with an LOD near 8 ng/ml and atrazine with an LOD near 40 pg/ml, 80 the pesticide metalachlor with an LOD near 600 pg/ml, 84 and c-reactive protein at an LOD of 1 pM. 82 It must be noted that all of these assays consisted of sandwich assays in which a second antibody to an antigen must be bound, often carrying a gold nanoparticle as a catalyst for silver enhancement.…”

Pneumatic pumping in centrifugal microfluidic platforms

“…For example, in the case of in vitro diagnostics, multiplexing of diverse and complex analytical functions is easily achieved by embedding several individual assays and running them simultaneously on identical segments symmetrically arranged on the same CD. Additionally, native CD optics can easily be adapted and modified to interface with disc-based assays enabling the automation of multiple analysis steps from sample preparation to detection (Bañuls et al 2008;Morais et al 2007).…”