DNA-guided interparticle energy transfer between rare earth doped nanoparticles†

Abstract

Rare earth doped nanoparticles (RENPs) emit upconverted radiation in the ultraviolet (UV), visible (vis), and higher energy near-infrared (NIR) range, and downshifted, lower NIR energy. Most RENP-based optical sensors depend on energy transfer between the RENP and another entity that emits UV/vis light upon detection of the target of interest. However, attenuation of the emitted UV/vis light by biological tissue components prevents in vivo sensing in deep tissue regions. To avoid this, we propose a sensor that works entirely in the NIR range, composed of two RENPs. The sensor is based on core@shell RENPs comprising Tm³⁺ (energy donor) and Nd³⁺ (energy absorber) ions doped in a LiYF₄ host matrix, functionalized with complementary DNA strands. Hybridization of the DNA strands reduces interparticle distance allowing interparticle energy transfer (IPET) to occur, as shown by a decrease in intensity of the NIR emission from the Tm³⁺ doped RENPs observed only in the presence of DNA-functionalized Nd³⁺ doped RENPs. While previous works showed IPET occurring between RENPs held in close proximity by hydrophobic interactions between surface molecules, this work shows that responsive linkers (in our case, DNA) can be used to enable IPET. This result lays the foundation for an RENP-based NIR-excited and NIR-emitting optical sensor for deep tissue sensing.