Quantification of Internalized Silica Nanoparticles via STED Microscopy

Area of Science:

• Nanotechnology
• Cell Biology
• Toxicology

Background:

• Understanding nanoparticle (NP) interactions with cells is vital for developing safe nanomaterials.
• Quantifying NP internalization is essential for predicting cellular NP doses, aiding risk assessment and drug delivery applications.

Purpose of the Study:

• To quantify the internalization of 25 nm and 85 nm silica nanoparticles (SNPs) in alveolar type II cells (A549).
• To assess the influence of particle size and serum presence on SNP uptake and cytotoxicity.

Main Methods:

• Super-resolution STED microscopy was employed to visualize and quantify SNP internalization.
• Cells were exposed to equal particle number concentrations of different sized SNPs.
• The in vitro sedimentation, diffusion, and dosimetry (ISDD) model was used to account for particle sedimentation.

Main Results:

• Both 25 nm and 85 nm SNPs were internalized by A549 cells within 5 hours in both serum-supplemented and serum-free media.
• Intracellular NP concentrations ranged from 10^2 to 10^3 NPs per cell in serum-containing medium.
• No cytotoxicity was observed in the presence of serum, while high concentrations of smaller SNPs induced cytotoxicity in serum-free conditions.

Conclusions:

• Particle size and serum presence are critical factors influencing SNP cellular uptake and toxicity.
• Accurate dosimetry, considering sedimentation, is necessary for reliable NP risk assessment.
• These findings provide valuable data for the safe design of engineered nanoparticles for biomedical applications.