The capability to diagnose and treat a disease using a single platform is a highly desirable goal in the development of new medical products. The combination of diagnostics tools and therapeutic agents in a single nanoplatform, the so-called theranostic agents, together with the addition of targeting agents, is an emerging technology applicable to bioapplications such as cancer treatment.

Nanomaterials are suitable for functionalisation with receptors, sensors and/or drugs due to their high surface-to-volume ratio. However, this feature also bears the greatest challenge in functionalised nanomaterial synthesis as it often results in agglomeration and, thus, poor performance and high toxicity in biological media. Therefore, it is desirable to develop functionalisation strategies that protect particles from agglomeration in biological environments, yet still allow the particle surface to be modified to introduce multifunctionality.

Researchers at the University of East Anglia (UEA), led by Dr María J. Marín, have worked in collaboration with the group of Dr Thomas Hirsch at the University of Regensburg (Germany) to develop a synthetic strategy for the surface modification of hydrophobic nanoparticles. The strategy provides excellent colloidal stability in biological environments and good protection against disintegration, while permitting surface functionalisation via simple carbodiimide chemistry. As a proof-of-concept, the authors have demonstrated the potential of their approach using upconversion nanoparticles (UCNPs), which have shown great potential for biomedical applications due to their near-infrared excitable properties, overcoming some of the drawbacks of currently-used phototherapies in, for example, cancer.

The biological relevance of the novel approach developed by Dr Hirsch and Dr Marín was confirmed with the use of two model dyes, a photosensitizer drug, used for photodynamic therapy of cancer, and a nitric oxide (NO) probe that, when attached to the surface of the UCNPs, retained their functionality to produce singlet oxygen and detect intracellular NO, respectively.

The work, partially funded by the Royal Society of Chemistry, presents a simple and fast strategy to protect and functionalise inorganic nanoparticles in biological media, which is important for controlled surface engineering of nanosized materials for an extensive number of theranostic applications.

The work is published this week in the high impact factor journal, Angewandte Chemie, DOI: doi.org/10.1002/anie.202305165 (open access).