Japanese scientists use tiny silver particles to make DNA assembly up to 5x more efficient
Silver nanoparticles can precisely slice DNA and create longer “sticky ends,” helping genetic fragments join up to five times more efficiently than conventional methods. The breakthrough could eventually simplify the construction of large DNA sequences for gene therapies, cancer vaccines, engineered drugs, and advanced crops.
Japanese scientists have discovered a method that utilizes silver nanoparticles to enhance DNA assembly by up to five times compared to traditional techniques. DNA consists of long chains that carry genetic instructions, and researchers cut and reconnect these pieces to create various applications such as improved crop breeding and treatments for genetic diseases.
Sticky ends, overhanging sequences, facilitate the binding of DNA fragments. Existing technologies, however, often struggle with producing precise sticky ends. To address this issue, researchers at Nagoya University and Gifu University developed a technique using silver nanoparticles to cut and reconnect DNA at targeted sites. The technique proved to be two to five times more efficient than conventional restriction enzyme methods.
The findings were published in Nucleic Acids Research. Standard methods for assembling long DNA molecules typically use restriction enzymes and T4 DNA ligase. Restriction enzymes can only cut specific DNA sequences and produce short sticky ends, reducing joining efficiency. The team sought an alternative by revisiting a 1990s reaction where silver ions cut 3-thiol-modified DNA at specific sites.
However, silver ions attached nonspecifically and caused precipitation, recovering only 14% of the DNA. To improve DNA recovery, the researchers replaced silver ions with nanoparticles and coated them with polyethylene glycol (PEG) to enhance stability and dispersion. This modification increased DNA cleavage efficiency from 36% to 92% at 37°C within 31 hours.
The nanoparticle approach also provided built-in purification, recovering 98% of the desired DNA fragments. The silver nanoparticles allowed the generation of 8-base sticky ends, which are difficult to create using conventional restriction enzymes. When these fragments were joined using T4 DNA ligase, the joining efficiency was twice as high as traditional methods.
For DNA fragments with an 18-base overhang, the joining efficiency reached 44%, a fivefold improvement over traditional 4-base overhangs. To validate the method's practicality, the researchers assembled a DNA fragment encoding green fluorescent protein (GFP) and demonstrated successful expression in human HeLa cells. The technique holds potential for synthesizing genomic DNA, with applications in mRNA library establishment for cancer vaccines, gene therapy, and the development of artificial protein drugs and genome crops.
Researchers are now exploring whether the method can join multiple DNA fragments simultaneously, a crucial step for building genome-scale DNA.
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