Improved fluorescence-based medical tools

Fluorescence upconversion nanoparticles that absorb light in the IR range and emit in a higher-energy visible range are gaining growing interest for biomedical imaging applications. The possibility for IR excitation is a major advantage because IR is not absorbed by tissues so it has deeper tissue penetration depth and does not damage biological tissues. Nanoparticles functionalised with IR-excitable upconverting labels offer the possibility to activate photosensitive agents for applications such as cancer treatment.

An EU-funded team initiated the project 'Novel luminescent upconversion nanoparticles for diagnostic and therapeutic nanomedicine' (LUNAMED) to investigate the potential of novel upconversion nanoparticles. Creating such materials by doping with lanthanide ions is a route not fully explored to date. The nanoparticles were functionalised for bioactivity by attaching carefully selected molecules to their surfaces.

Scientists successfully synthesised composite nanoparticles and functionalised them for therapeutic applications. Various functionalisations were studied and their uptake by cancer cells versus healthy cells was compared. In the end, the team demonstrated their use for both optical imaging of cancer cells and for photodynamic therapy. Specifically, IR excitation induced visible emission by the nanoparticles. The visible emission was used to excite the photosensitiser that then destroyed cancerous cells in the vicinity.

LUNAMED paved the way to use of a relatively under-explored synthesis route to create nanoparticles functionalised with IR-excitable upconverting labels. The IR sensitivity enables deeper tissue penetration and minimal effects on healthy cells. Targeted biomedical applications include ultra-sensitive cell targeting, imaging and therapy, and published results are proof of the potential.