Microarray continues to hold its place among newer technologies

Microarray technology has empowered the scientific community understand and explore the gene functions and related causes of medical anomalies. And it continues to be considered a simple and time-honoured method.

Microarray is a tried and tested technology since years. Although, it is being overshadowed by newer, faster and fancy methods such as next-generation sequencing (NGS), microarray analysis is still a preferred method in many areas. The biochip technology evolved from its use in research labs for studying expression of genes to a biotechnological tool with a wide range of applications in medical and related fields.

A miniaturize process that allows detection of DNA or RNA molecules as they hybridize or bind with target molecules on a glass slide, the adherent molecule is detected by various labels or dyes which enables their visualization under a microscope. The system has been utilized for genotyping, antibody detection and comparative genome analysis, where it finds purpose in medical diagnosis and treatment, biotechnological research fields as well as for crime and security.

A spectrum of applications
Microarray device, is of various types depending on the type of immobilized sample used to construct arrays and the information detected. Although, it is primarily being used for drug discovery, diagnostics, and pharmacogenomics and theranostics, the potential usage of microarray systems surpasses its current applications.

Microarray applications in the field of oncology are well known, especially in analysing large number of samples, which are either previously recorded or new samples, and testing the incidence of a particular marker in tumours. It is also being used in the study of various cardiovascular, inflammatory, infectious diseases, and psychiatric disorders.

Arrays are also progressively playing a significant role in detecting Biological Warfare Agents (BWAs), the microorganisms or toxins produced and intentionally dispersed by terrorists to spread diseases. The gene chip provides a platform that enables fast, sensitive, and simultaneous identification of such agents. It has been found to be very useful for national security and general protection of life in terms of threat. SNP microarrays, a type of DNA microarray, has importance in forensic analysis. It aids in acquiring the details of DNA that helps with investigation purposes. The recent discovery of a number of SNPs and the ease of automation along with availability of miniaturization detection techniques has paved the way for the implementation of microarray tools in forensic science.

Global scenario
The global microarray systems revenue estimated at USD 1377 million in 2019, and at a CAGR of 4.56 percent during 2020-2025, is projected to reach USD 1799 million in 2025, according to Market Watch. Leading vendors include Applied Microarrays, Qiagen, Thermo Fisher Scientifix, Illumina, Merck, Affymetrix, Agilent Technologies, GE Healthcare, Arrayit, Roche NimbleGen, and Biometrix Technology.

By category, the consumables segment has a majority revenue share over its counterparts, software and services, and instruments. Bulk and repeat purchase for diverse applications drive this segment. This trend is expected to continue in the near future.

The global DNA microarray market size accounted for USD 1119.4 million in 2019 and is expected to reach USD 1243.8 million by the end of 2026, with a CAGR of 1.5 percent during 2021-2026.

The global protein chip market size is estimated at USD 2.01 billion in 2020 and estimated to be growing at a CAGR of 18.21 percent to reach USD 4.64 billion by 2025.

The driving factors are the growing need for personalized medicines and rising incidences of cancer around the world. The massive investments in research and development of these methods have further contributed to the market growth.

Factors that can possibly hinder the global market growth for microarray are the upcoming advances of more cost-effective and accurate next-generation DNA sequencing, combined with stringent government regulations, scarcity of skilled professionals, and the standardization of microarray data.

A new platform. Fiber optic microarray is a new dynamic platform for the measurement of complex molecular, biological, and environmental systems.

A typical microarray system comprises a substrate with several different binding sites (feature) deposited on it. The substrate can be glass, silicon, nylon, or a variety of plastics. A feature has a unique binding specificity which allows multiple analytes in a mixture to be separated from each other and analysed serially. A signal change occurs upon binding with the feature and gets detected.

In a fiber-optic microarray system, optical fibers are used as the substrate as well as the detection method. The optical fibers are made of two different types of glass: a core glass surrounded by a glass cladding having a lower refraction index. This allows the fiber to transmit light over long distances with less attenuation.

Challenges 
Microarrays or biochips have been the technology of choice for large-scale studies of gene expression since their inception in the 1990s. Although the technology continues to evolve, transcriptomics has dramatically expanded in the recent past, owing to the availability of advanced technology, such as RNA-sequencing (RNA-seq) and Next Generation Sequencing (NGS), which are more accurate and cost-effective alternatives. While there are several advantages of microarray technology, such as less labor intensivity and are economical, the availability of alternative technologies and their benefits would be a welcome development.

Microarray technology has both low sensitivity and low specificity. Accuracy can get negatively affected because of low dynamic range in the existing microarrays. The accuracy of expression measurement, particularly for transcripts that are available in small amounts, may also be limited by background hybridization. The probes differ substantially in their hybridization properties and microarray technology becomes limited to investigation of only those genes for which probes have been designed. Low commercial acceptability due to the higher costs and lack of skilled professionals also pose a challenge.

Microarrays in conjunction with NGS
As the demand for sequencing services rises, the requirement for microarray processing and analysis is still holding up. However, many users are tilting toward NGS and other alternative gene sequencing technology. Many institutions have even been eliminating microarray cores altogether. But researchers still believe that arrays have significant benefits over RNA-seq. The workflow is much simpler, and it reduces the technical expertise required. Microarrays can yield results quicker – a boon for contract research organizations (CROs) and clinical labs. The technology boasts a lower cost per sample, especially in case of larger studies. Also, the data analysis and storage requirements are significantly lower, and it’s not necessary to have a bioinformatician on the team to interpret the results.

In certain labs, use of microarrays and NGS in conjunction is being promoted. Users run preliminary experiments on microarrays to get the feeling of the direction while looking for genome-wide expression changes before proceeding to NGS. This helps achieve a balance between experimental time and costs, without compromising performance.