What Are Upconverting Nanoparticles?

Upconverting nanoparticles (UCNPs) are nanoscale particles, with diameter from 1nm to 100 nm that can exhibit photon upconversion. Since François formally proposed the concept of upconversion luminescence in 1966, to the introduction of nanotechnology in the 1990s, scientists have synthesized many new functional inorganic upconversion nanoparticles with water solubility and high luminous efficiency. This functional upconversion nanomaterial has promoted the development of the diagnosis, treatment, imaging, and biological monitoring in the field of biomedicine. Applications of upconverting nanoparticles Due to UCNPs’ unique photophysical properties, including light-emitting stability, excellent upconversion luminescence efficiency, low autofluorescence, and high detection sensitivity, and high penetration depth in samples, UCNPs have been widely applied in biomedical applications, such as biosensing, imaging and theranostics. BioimagingrnAs an important technology in modern medical diagnosis, bio-fluorescence imaging has attracted much attention. Since the organism itself cannot provide fluorescent information for diagnosis, it is necessary to develop bio-fluorescence probes for bio-fluorescence imaging. Traditional bio-fluorescence probes mainly include organic dyes and quantum dots. In recent years, UCNPs have the advantages of good light stability, low detection limit of in vivo imaging, high signal-to-noise ratio and large penetration depth, making them more ideal biomarkers than organic dyes and quantum dots, but there are also shortcomings such as single imaging mode, weak luminescence of rare-earth ions, and energy backflow between the photosensitizer Er3+ and the activator. Photodynamic therapyrnPhotodynamic therapy (PDT) refers to an emerging technology for the diagnosis and treatment of diseases that uses photodynamic effects. In PDT treatment technology, the photosensitizer and its excitation light are the key elements. The excitation light source must have the spectrum and energy that the photosensitizer can absorb, as well as a certain degree of tissue penetration. However, the traditional excitation light cannot fully penetrate the tissue. PDT is only suitable for shallow tumors, but not for deep tumors, which greatly limits the scope of clinical application of PDT. The emergence of UCNPs makes it possible for PDT to use near-infrared light and other tissue-penetrating light sources as excitation light. This overcomes the shortcomings and limitations of traditional PDT technology that cannot fully penetrate tissues, improves the therapeutic effect of PDT, and broadens its clinical application range. TherapeuticsrnHow to learn about the tumor treatment status in real-time while performing treatment, so as to adjust the treatment method is a hot research topic in recent years. UCNPs themselves are also a kind of fluorescent materials, which can provide high-sensitivity optical imaging. Utilizing the natural optical imaging potential of UCNPs and the realization of multi-mode imaging by doping with a variety of lanthanide ions with imaging potential, it has unparalleled advantages for timely improvement of drug tracking during treatment.