The presence of approximately 200-bp cell-free DNA (cfDNA) in the urine has attracted attention as a biomarker for liquid biopsy. However, it is currently useful only for diagnoses of cancers in which a large amount of cfDNA is excreted in the urine. Therefore, the development of an efficient method for extracting cfDNA existing in small amounts in the urine is essential for diagnosing many other diseases. We examined the effect of particle size, small pore size (surface area), and surface modification of porous silica particles on the efficiency of DNA extraction. Our observations suggested that cfDNA could be captured by tertiary amine–modified particles and then removed from the particles by repeatedly washing with sodium bicarbonate (pH 11). Using this method with 30 mg of triamine-modified particles, we succeeded in extracting a few hundred nanograms of cfDNA from 15 mL urine. Furthermore, we could detect ~ 67 fg/mL caries DNA (211 bp) in 15 mL urine sample, suggesting that this method may be suitable for the extraction of genetic biomarkers for cfDNA-based liquid biopsy.

尿液中大约200 bp的无细胞DNA（cfDNA）的存在作为液体活检的生物标志物引起了人们的关注。然而，目前它仅用于诊断其中尿中排泄大量cfDNA的癌症。因此，开发一种有效的方法来提取尿液中少量存在的cfDNA，对于诊断许多其他疾病至关重要。我们检查了粒径，小孔径（表面积）和多孔二氧化硅颗粒的表面改性对DNA提取效率的影响。我们的观察结果表明，cfDNA可以被叔胺修饰的颗粒捕获，然后通过用碳酸氢钠（pH 11）反复洗涤从颗粒中去除。使用此方法处理30 mg三胺改性的颗粒，我们成功地从15 mL尿液中提取了数百纳克的cfDNA。此外，我们可以在15 mL尿液样品中检测到〜67 fg / mL龋齿DNA（211 bp），这表明该方法可能适用于基于cfDNA的液体活检的遗传生物标记物的提取。