Optically Robust and Biocompatible Mechanosensitive Upconverting Nanoparticles.

Area of Science:

• Nanotechnology
• Biomedical Engineering
• Materials Science

Background:

• Upconverting nanoparticles (UCNPs) offer background-free imaging and sensing capabilities.
• Biocompatibility, encompassing optical performance and toxicity, is crucial for in vivo UCNP applications.
• Mechanosensitive UCNPs require stable optical properties under non-mechanical stimuli.

Purpose of the Study:

• To evaluate the biocompatibility and mechanosensitivity of ligand-stripped α-NaYF4:Yb,Er@NaLuF4 nanoparticles.
• To assess the optical stability and toxicity of UCNPs in various biological conditions.
• To determine the suitability of UCNPs as in vivo sensors for studying digestion.

Main Methods:

• Ligand-stripping of UCNPs for aqueous dispersibility.
• Characterization of UCNP mechanosensitivity and optical properties under varying pH and buffer conditions.
• In vivo assessment of UCNP behavior in Caenorhabditis elegans digestive tracts and chronic toxicity testing via reproductive brood assays.

Main Results:

• Ligand-stripped UCNPs exhibited significantly enhanced mechanosensitivity compared to oleic acid-coated UCNPs.
• UCNPs demonstrated optical robustness and stability in various biorelevant conditions, including ex vivo and in vivo environments.
• No perturbation of biological function was observed in C. elegans, indicating low chronic toxicity.

Conclusions:

• Mechanosensitive UCNPs are optically robust and nontoxic, confirming their biocompatibility for in vivo applications.
• These UCNPs are suitable for use as in vivo sensors to investigate physiological processes like animal digestion.
• The study provides a framework for assessing UCNP biocompatibility for advanced biomedical applications.