适配子是对靶分子有高特异性和亲合力的单链寡核苷酸。 由于其结构特性, 常用于生物检测。 目前的适配子光传感器多采用染料或量子点为标记物, 存在背景高, 不稳定等缺点。 新型的荧光材料上转换纳米晶(UCNPs)因其特殊的发光性质颇受关注。 与传统的下转换材料相比, 它是近红外光激发, 避免产生背景荧光和杂散光。 利用聚乙酰亚胺为表面配体, 水热法合成了NaYF4∶Yb3+, Er3+, 并设计了UCNPs标记的适配子“光开关”。 无目标蛋白时, 适配子和标记TAMRA序列形成双链结构, UCNPs和TAMRA距离靠近, 荧光共振能量传递发生。 有目标蛋白时, 适配子倾向于和蛋白结合, 能量传递被破坏。 UCNPs荧光增强而TAMRA荧光减弱。 这种目标分子的依赖性变化就像一个“光开关”, 可用于生物分子的识别。

As new class of fluorescent biolabels, upconversion nanoparticles (UCNPs) were very attractive for use as labels, compared with these traditional downconversion materials. It can eliminate problems associated with autofluorescence and scattered excitation light under near infrared light (NIR) excitation. In the present work, water-soluble NaYF4∶Yb3+, Er3+ UCNPs were successfully prepared by solvothermal synthesis, using branched polyethylenimine as the surfactants, and a generic design strategy for UCNPs conjugated aptamer based optical switch was presented. In the absence of the target thrombin protein, such a duplex structure brings the UCNPs and TAMRA close proximity of each other, leading to luminescence resonance energy transfer from UCNPs to TAMRA upon near-infrared light irradiation. When target is introduced, the quadruplex conformation of the aptamer should be preferentially stabilized, resulting in the displacement of the TAMRA labelled oligonucleotide conjugate and triggering UCNPs fluorescence intensity to increase and the corresponding TAMRA fluorescence intensity to decrease. Since the aptamer responds to its target molecule by switching on its fluorescent properties, the authors named this an “optical switch”.