Surface modified lanthanide upconversion nanoparticles for drug delivery, cellular uptake mechanism, and current challenges in NIR-driven therapies

Lanthanides(Ln3+) are a particular class of optical materials and are regularly utilized as a structure block for architectures of optoelectronic frameworks because of their excellent emission properties extending from ultraviolet(UV)/Visible to near-infrared (NIR) region. Upconversion nanoparticles (UCNPs) uncovered noteworthy qualities, like the least to-harmfulness, fantastic biocompatibility, excellent colloidal dispersibility, and limited photograph harm, auto-fluorescence free, high thermal, mechanical, and photochemical robustness contrasted with other luminescent NPs. Therefore, UCNPs offer attractive opportunities in nanomedicine to fight against cancerous diseases. Recently, the NIR light irradiation takes into deliberation to enhanced infiltration insight and successful applications in cancer diagnostics and cure because NIR light produces minimum side effects on biological cells/tissues during cancer treatment. In this review, we emphasize the various issues, which are important in theranostics/ drug delivery applications. Surface functionalization to improve the biocompatibility, toxic potentiality, and enhanced the drug loading over the surface of luminescent NPs. The review discussed the mechanism of UCNPs interaction with cells/tissues. The interaction of UCNPs with cells/tissues changed the bio-distribution process, chemically responsive crossing point, and the fusion of solid-state properties and chemical kinetics of the molecules. Moreover, this review discussed the modern development of NIR light-responsive theranostic applications through various techniques such as photodynamic therapy (PDT), photothermal therapy (PTT), chemotherapy, and drug delivery applications. Specifically, the UCNPs will give an ideal multifunctional forum to answers for some center clinical science issues, for example, theranostics, personalized treatment, multimodality medication, and so on. The most successful protocols are implemented in-depth. To include a general overview and recommend future study directions, existing shortcomings, and future opportunities are also included.