Typical Applications and Operating Procedures of Nucleic Acid Extraction Kits in Clinical and Research Settings

I. Main Application Scenarios

Nucleic acid extraction kits are widely used in clinical testing, basic research, public health, and the biotechnology industry. In pathogen detection, extracting viral or bacterial nucleic acids from samples such as nasopharyngeal swabs, sputum, and blood is a prerequisite for subsequent fluorescence PCR, isothermal amplification, or sequencing. Tumor genetic testing often obtains nucleic acids from samples such as paraffin-embedded tissues, plasma cell-free DNA, and fresh tissues for mutation analysis, methylation studies, or detection of drug-related biomarkers. Genetic disease screening and prenatal diagnosis require extracting high-quality genomic DNA from peripheral blood, amniotic fluid, or chorionic villi. In the fields of food safety and animal quarantine, kits can be used for pre-treatment in the detection of pathogenic microorganisms, genetically modified components, or animal-derived components in food. Forensic samples such as bloodstains, saliva stains, and hair follicles are trace specimens that impose higher requirements on extraction sensitivity and recovery rate.

II. Sample Pre-treatment and Operational Key Points

Pre-treatment varies considerably among different sample types. Blood samples generally require prior removal of red blood cells or direct lysis, tissue samples require homogenization or enzymatic digestion, and paraffin samples require dewaxing and proteinase K digestion. During operation, the sample amount and lysis time recommended in the kit instructions should be followed. Excessive sample may clog the membrane or reduce purification efficiency, while too little may lead to insufficient nucleic acid yield. Incomplete lysis, incomplete digestion, or incomplete washing may leave residual proteins, lipids, or salt ions, affecting downstream amplification.

When extracting RNA, because RNA is easily degraded by RNases in the environment, laboratory benches, pipettes, and consumables should be dedicated or treated with RNase removal whenever possible, and operators should wear gloves and minimize talking. Steps such as low-temperature centrifugation, rapid aliquoting, and addition of RNase inhibitors help maintain RNA integrity. After extraction is completed, it is recommended to perform reverse transcription as soon as possible or store at low temperature, avoiding repeated freeze-thaw cycles.

III. Contamination Prevention and Quality Control

The nucleic acid extraction step is one of the steps in molecular testing laboratories where cross-contamination is more likely to occur. It is recommended to physically separate the sample preparation area, nucleic acid extraction area, amplification area, and product analysis area, use filter tips, and regularly replace disinfectant and wipe bench surfaces. Negative controls, positive controls, and extraction blank controls should be set up for each batch of experiments to monitor whether there is contamination in extraction reagents, consumables, or the environment.

For automated extraction platforms, daily maintenance and regular calibration plans should be established to confirm the accuracy and consistency of magnetic rods or pipetting channels. There may be slight differences between different batches of kits, and it is recommended to use the positive reference materials provided with the kit or in-house laboratory quality control materials for verification in key testing items. Recording the extraction date, lot number, operator, and sample number helps trace the cause when results are abnormal.