Post-PCR sterilization: development and application to an HIV-1 diagnostic assay

Area of Science:

• Molecular Biology
• Photochemistry
• Diagnostic Assays

Background:

• Polymerase Chain Reaction (PCR) is a powerful tool for DNA amplification.
• Amplicon carryover, the contamination of new PCR reactions with products from previous ones, is a significant challenge in molecular diagnostics.
• Existing sterilization methods often compromise assay performance or require open-tube systems.

Purpose of the Study:

• To develop and validate an effective post-PCR sterilization process to eliminate amplicon carryover.
• To assess the suitability of isopsoralen photochemistry for a practical diagnostic assay, specifically for HIV-1 detection.
• To ensure the sterilization method meets both inactivation and hybridization requirements for reliable molecular testing.

Main Methods:

• A novel sterilization process based on isopsoralen photochemistry was developed.
• Isopsoralen compounds were used to form covalent photochemical adducts with DNA amplicons.
• The method was applied to a diagnostic assay for Human Immunodeficiency Virus type 1 (HIV-1).

Main Results:

• Isopsoralens effectively prevent Taq polymerase extension of previously amplified sequences by forming covalent adducts with DNA.
• The photochemical treatment has minimal inhibitory effect on PCR, is activated by long-wavelength UV light, and modifies amplicons to remain single-stranded.
• The method demonstrated effective sterilization with little impact on subsequent hybridization, suitable for closed-tube systems and common detection formats.

Conclusions:

• The developed photochemical sterilization protocol is an effective and pragmatic solution to the amplicon carryover problem in PCR.
• This isopsoralen-based method ensures assay integrity and accuracy, particularly in clinical settings.
• The technique is broadly applicable to various amplicons beyond HIV-1, enhancing the reliability of PCR-based diagnostics.