Research trends and hotspots of upconversion nanoparticles for drug delivery and biomedical targeting in photodynamic therapy

AIM: This study presents a bibliometric analysis of research trends and emerging hotspots in upconversion nanoparticles (UCNPs) for drug delivery and biomedical targeting in photodynamic therapy (PDT). METHODS: We retrieved 474 publications from the Web of Science (2007-2025) and analyzed publication trends, contributions from countries, institutions, and authors, keyword co-occurrence, citation bursts, and co-citation networks using CiteSpace, VOSviewer, HistCite, and R software. RESULTS: UCNP-PDT research progressed through three distinct phases, with China and the USA contributing the most publications. Nanoscale published the highest number of articles, while high-impact reviews appeared in Chemical Society Reviews and Advanced Materials. Emerging research focuses include the tumor microenvironment, metal-organic frameworks, combination therapies, and antimicrobial PDT. CONCLUSION: UCNP-PDT has evolved from simple photosensitizer loading to multifunctional nanoplatforms, expanding applications to cancer therapy, infection control, and immune modulation. Clinical translation remains limited by size-efficiency trade-offs, low-power irradiation, hypoxia, tissue heating under 980 nm excitation, GMP-compliant production, and insufficient long-term biosafety data. Future advances require coordinated strategies integrating material optimization, mechanistic insight, and translational considerations to achieve safe, scalable, and effective UCNP-PDT for clinical use.