Initial Biological Assessment of Upconversion Nanohybrids.

Area of Science:

• Materials Science
• Nanotechnology
• Biomedical Engineering

Background:

• Upconversion nanoparticles (UCNPs) are inorganic-organic hybrid materials with potential biological applications.
• Potential cytotoxicity of UCNPs due to fluoride and lanthanide release necessitates thorough safety evaluation.
• Cucurbit[7]uril (CB[7]) coating can modify UCNP properties for enhanced biocompatibility.

Purpose of the Study:

• To evaluate the cytotoxicity and endotoxin contamination of bare UCNPs (UCn) and UC@CB[7] nanohybrids.
• To investigate the cellular uptake and mode of cell death induced by these nanohybrids.
• To assess the suitability of UC@CB[7] nanohybrids for biological applications.

Main Methods:

• Dehydrogenase activity assays to determine cell viability.
• Lactate dehydrogenase release assays to detect necrotic cell death.
• Calcein AM/Ethidium homodimer-1 staining to identify apoptosis.
• Near-infrared (NIR) laser scanning microscopy for cellular uptake studies.

Main Results:

• UCNPs and UC@CB[7] nanohybrids demonstrated no significant cytotoxicity in endothelial cells.
• Apoptosis was identified as the primary mode of cell death in exposed cells.
• Endotoxin contamination was absent in the tested nanoparticle samples.
• Higher cytotoxicity was observed in HeLa and RAW 264.7 cells, potentially due to differences in lysosome content and uptake rates.
• Cellular internalization of both UCn and UC@CB[7] nanohybrids was confirmed via NIR microscopy.

Conclusions:

• UC@CB[7] nanohybrids are non-cytotoxic to endothelial cells and free from bacterial contamination, indicating their safety for biological applications.
• The observed cell death mechanism is primarily apoptosis, suggesting controlled cellular interactions.
• Differences in cytotoxicity across cell lines highlight the importance of cell-specific safety assessments for nanomaterials.