Principles of Gene Microarray Technology and Analysis of Common Hybridization Platforms and Signal Detection

Basic Principles of Gene Chips

A gene chip is a technical platform that enables parallel detection based on complementary hybridization between probes of known sequence and labeled nucleic acids in a sample to be tested. Its core feature is the immobilization of a large number of oligonucleotide or cDNA probes at predetermined positions on a solid support. After extraction, amplification, and labeling, the sample hybridizes with the probes, and signals are read via fluorescence, chemiluminescence, or electrochemical detection to obtain relative abundance or typing information for multiple targets in the sample. Common solid supports include glass slides, silicon wafers, and nylon membranes, among others, and microarray density varies depending on the probe preparation process and detection purpose. Because the probe sequences and positions are known, gene chips can simultaneously detect hundreds to thousands of known targets in a single experiment, which is an important feature distinguishing them from single PCR or sequencing.

Common Preparation Processes and Classification

The preparation routes for gene chips are mainly divided into two categories: in situ synthesis and spotting. In situ synthesis involves the stepwise synthesis of oligonucleotides on a chip substrate according to predetermined sequences, resulting in relatively high probe density and generally being suitable for whole-genome coverage or large-scale SNP screening. Spotting involves immobilizing pre-synthesized or amplified probes onto the substrate surface using contact or non-contact spotting equipment; this preparation method is relatively flexible and suitable for custom gene panels or small- to medium-scale screening scenarios. According to probe type, chips can also be divided into cDNA chips, oligonucleotide chips, and others. Selection should be comprehensively evaluated based on the number of detection targets, sample type, throughput requirements, and budget; there is no universal solution suitable for all projects.

In situ synthesized chips: relatively high probe density, suitable for large-scale locus coverage and expression profiling studies.

Spotting chips: flexible probe design, suitable for specific gene panels and customized detection.

Liquid-phase chips: probes immobilized on the surface of microspheres and read through flow cytometry or similar detection systems, mostly used for multiplex protein or nucleic acid analysis.

Signal Detection and Data Interpretation

Signal acquisition after hybridization usually relies on laser scanners, CCD imaging systems, or dedicated chip readers. Data analysis includes background correction, normalization, quality control probe filtering, and differential expression or typing algorithms. Because chip experiments involve multiple steps, including extraction, labeling, hybridization, washing, and scanning, fluctuations in any step may introduce systematic error; therefore, experimental design should include internal reference genes, negative controls, and replicate samples. Batch-to-batch comparisons should use the same normalization method, and caution should be maintained for low-signal and high-background regions. Interpretation of results cannot rely on a single threshold alone and requires comprehensive judgment in combination with probe design, hybridization efficiency, and sample quality.

Common Application Directions

Gene chips are used in gene expression profiling, single nucleotide polymorphism typing, copy number variation detection, DNA methylation analysis, and multilocus identification of pathogenic microorganisms, among other directions. In research settings, they are often used to screen disease-related candidate genes or compare expression differences under different treatment conditions; in clinical auxiliary diagnosis, they can be used to detect known variants or expression patterns related to specific medications or typing. It should be clearly understood that gene chips detect signals within the range of predetermined probes, and results should be interpreted in combination with other molecular detection methods and clinical information, and cannot alone serve as the sole basis for diagnosis or medication decisions.