A near-infrared (NIR) responsive DNA probe has been developed for DNA hybridization detection with characteristics of high efficient Förster resonance energy transfer (FRET) from small (∼10 nm) upconversion nanoparticles (UCNPs) to nucleic acid stain SYBR Green I (SG, a specific intercalator of double-stranded DNA). The positively charged UCNPs were prepared and facilely attached with single DNA strands by coordination interaction, which acted as probes to detect the DNA targets in the presence of SG. This probe possesses not only the superiority of the NIR-excitation nature of UCNPs which could minimize the autofluorescence background from biomolecules and the photodamage to biological specimens, but also the advantages of facile preparation and high FRET signals. The FRET efficiencies could increase significantly from 2.6% to 12.5% and then to 26% when the size of UCNPs reduced from 94 nm to 30 nm and to 10 nm, respectively. The 10 nm-UCNP-based DNA probe could reach a lower detection limit of complementary ssDNA2 at 3.2 nM and three-base mismatched ssDNA2-M3 at 7.6 nM. The high sensitivity and selectivity of the probe may endow the system with great potential in fluorescence-based biosensing under the irradiation of NIR light.

已开发出一种近红外（NIR）反应型DNA探针，用于DNA杂交检测，具有从小（〜10 nm）上转换纳米粒子（UCNP）到核酸染料SYBR Green I（SG）的高效Förster共振能量转移（FRET）的特性，一种特定的双链DNA嵌入剂）。制备带正电荷的UCNP，并通过配位相互作用轻松地与单条DNA链连接，在SG存在下，UCNP充当探针检测DNA靶标。该探针不仅具有UCNPs的NIR激发性质的优势（可以使生物分子的自发荧光背景和对生物标本的光损伤最小化），而且还具有制备简便和FRET信号高的优点。FRET效率可以从2.6％显着提高到12。当UCNP的大小分别从94 nm减小到30 nm和减小到10 nm时，分别为5％和26％。基于10 nm-UCNP的DNA探针可达到3.2 nM的互补ssDNA2和7.6 nM的三碱基错配ssDNA2-M3的较低检测限。探针的高灵敏度和选择性可以使系统在近红外光的照射下在基于荧光的生物传感中具有很大的潜力。