Lanthanide upconversion nanoparticles for clearer bioimaging

Biological images become more useful when the signal from a probe stands above the light emitted by the sample. Lanthanide-based upconversion nanoparticles, also called UCNPs, absorb near-infrared photons and re-emit visible light through an anti-Stokes process. This unusual optical behaviour supports low-background imaging of cells, tumours, vessels and immune-cell movement.

The 16th International Symposium on Applied Bioinorganic Chemistry, held in Ioannina, Greece, in June 2023, brought this work into a forum connecting coordination chemistry, nanomaterials and medicine. Organised by the University of Ioannina, the meeting also highlighted young scientist travel awards, poster prizes, scholarships and clear application routes for delegates.

Why near-infrared excitation reduces biological noise

Near-infrared excitation is valuable because biological tissue absorbs less of it than visible light, while ordinary dyes often generate strong autofluorescence under the same illumination. An upconversion probe can therefore excite at a longer wavelength and report at a shorter one, separating the intended signal from much of the background.

That advantage is especially clear for deep-tissue and single-cell work, although brightness still depends on laser power, particle dose and detector settings. Meaningful comparisons need untreated controls, spectral measurements and checks for photobleaching, heating and light scattering rather than visual appeal alone.

Engineering a bright and stable upconversion core

A useful upconversion particle usually combines a crystalline host with lanthanide dopants. NaYF4 is a common host; Yb3+ absorbs near-infrared energy efficiently, while Er3+ or Tm3+ emitters generate visible or near-infrared output. The result is a nanoscale light source rather than a conventional fluorescent dye.

Core-shell designs can protect the active centre and transfer energy between layers, raising quantum efficiency and photostability. Particle size, phase, ligand shell and surface charge all influence uptake and distribution, so reproducible synthesis and detailed spectroscopy are essential for comparing one laboratory’s result with another.

Making upconversion nanoparticles biocompatible

Biological use begins with safety. Researchers must distinguish intact nanoparticles from released lanthanide ions, assess dose-dependent toxicity, and check that coatings survive in serum or phosphate-rich media. PEG, silica or biomolecule-based coatings can improve dispersion and limit unwanted interactions with proteins and immune cells.

Targeting ligands can direct particles to selected receptors, but attachment must be quantified rather than assumed. Endotoxin, sterility, zeta potential, hydrodynamic size and clearance are routine questions in translation, alongside storage history and batch-to-batch variation. These controls make the difference between a promising microscope image and credible biomedical evidence.

Moving from cell imaging to in vivo studies

At cellular scale, upconversion imaging supports viability assays, nanoparticle uptake studies and long-term tracking with less autofluorescence. In animals, the same particles can follow tumour accumulation, vascular changes or labelled immune cells. Near-infrared emission can also be paired with X-ray or magnetic resonance measurements for multimodal imaging.

Some designs add therapy or imaging functions, creating theranostic candidates rather than diagnostic tracers alone. The route towards clinical use remains demanding: dose, biodistribution, metabolism and clearance require longitudinal evidence, and exposure limits must be kept below levels that cause toxicity or alter tissue function.

What the Ioannina symposium brought together

The Ioannina programme showed how broad the field has become. Presentations linked rare-earth nanophosphors with probe design, tumour targeting, immunotherapy monitoring and assessment of biological effects. The scientific value lay in the exchange of methods and controls, from synthesis and surface analysis to imaging performance in relevant models.

Contributors followed the dedicated portal to submit an abstract, while the wider programme connected oral presentations, posters and discussion. This mix gives early-career researchers direct feedback from specialists and helps experimental findings travel quickly between groups working with different analytical tools.

Supporting students and early-career researchers

Participation was supported through young scientist travel awards and scholarships, with applications asking for evidence of research quality, scientific fit and the expected benefit of attendance. Poster prizes gave students and postdoctoral researchers another route to recognition, while awards reduced the cost of crossing borders for researchers with limited travel funding.

Strong science depends on a well-run meeting, including the practical details that sit around the talks. Although written for weddings, the event-planning advice in vendor meals and breaks is transferable to symposia: meals should fit the scientific timetable, dietary needs should be handled calmly, and short pauses can protect discussion without derailing the programme.

Connecting Australian laboratories with Ioannina

Australian participation has its own practical texture. Researchers often work in Melbourne, Brisbane, Sydney or Perth and compete for support through universities, the NHMRC, the ARC and industry partnerships. That funding market rewards a clear translational case, especially when a lanthanide platform is tied to an unmet clinical or research need.

Distance also shapes the work. Moving cells, tissue or animal samples between Australian states requires biosecurity checks, permits and cold-chain planning, while researchers travelling to Ioannina need registration, accommodation and visa advice from Zita Congress & Event Management, the official symposium secretariat. In June, Greece was seven hours ahead of Sydney and Melbourne and five ahead of Perth. Local habits matter too: Australian English uses “fibre” and “optimisation”, and “morning tea” is a familiar conference pause rather than an all-day meal.

Researchers ready to contribute can read the symposium abstract guidance, prepare a concise account of the chemistry, imaging method and biological evidence, and check the relevant award or scholarship criteria. For registration, accommodation or abstract-related enquiries, contact Zita Congress & Event Management and make the next scientific connection around lanthanide-based bioimaging.