A microarray is an analytical tool used by researchers to study complex mixtures of proteins. It comprises a substrate such as glass, silicon, or nylon on which biological materials are deposited for analysis.
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A microarray, or ‘lab-on-a-chip’, is composed of hundreds or thousands of DNA fragments which have been mapped to specific loci in the human genome. The microarray washed with many potential ligands, and one of several detection technologies is then used to identify which fragments have bound ligands, indicating a positive result for the experiment.
In a fiber optic microarray, optical fibers are used as the microarray substrate, as well as a detection method. Optical fibers are made of two different types of glass; a core glass surrounded by a clad which has a lower refraction index. This allows the fiber to transmit light over long distances with little attenuation.
Fiber optics have been used extensively in technology and communications industries, and are now finding their way into biological research application.
In a fiber optic microarray, the sample is immobilized on one end of an optical fiber, then a number of fibers, each with a different immobilized sample probe on its tip, are bundled together. When a ligand binds to the probe, fluorescence emission is triggered and detected by CCD camera.
Applications of fiber optic microarrays
Some applications of fiber optic microarrays include detection of harmful algal bloom species, analysis of proteins, cell migration, and DNA analysis.
A protein detection assay based on enzyme-linked immune sorbent assays (ELISA) can be adapted to a fiber optic microarray format by immobilizing a capture antibody on the surface of a microbead and placing the microbead at the tip of the optic fiber. The detection antibody carrying the fluorophore will then bind to the capture antibody, activating a fluorescent emission.
Fiber optic microarrays can be used for cell migration assays by immobilizing the target proteins (fibronectin and collagen) that enable cell adhesion. The probe tips are then washed with fibroblast cells labeled with a fluorescent dye. Emission of a fluorescent signal occurs when antimigratory substances are present in the cells.
Fiber optic microarray technology has also been used for analysis of DNA. Single-stranded DNA probes are attached to microspheres and affixed to the ends of the optic fibers. Fluorescently labeled single-stranded DNA samples are then placed on the microarray, and the optic fibers are monitored for fluorescence. Complementary DNA strands will hybridize to each other, showing that the target DNA sequence is present in the sample.
Detection of harmful algal bloom species
Algal blooms release toxins that can threaten coastal resources including fish and other organisms. In one study, a fiber optic microarray was used to detect organisms causing harmful algal blooms (HABs) using ribosomal RNA from several target species immobilized on microspheres to create a capture probe and placed in a microarray. The researchers then developed a sandwich immunoassay which was applied to the microarray and used to detect HAB organisms.
The fiber optic microarray is a versatile platform that has been adapted to many different assay formats. It can be applied to many types of investigations including cellular, protein, and DNA analysis, and has utility in many areas of basic and applied biological research.
Reviewed by Afsaneh Khetrapal Bsc (Hons)