Insights into the Structure of Ultrasmall Fluorescent Core-Shell Silica Nanoparticles

Area of Science:

• Nanotechnology
• Materials Science
• Biomedical Engineering

Background:

• Ultrasmall fluorescent core-shell nanoparticles with silica cores and poly(ethylene glycol) shells are FDA-approved for clinical trials.
• These hybrid nanoparticles are among the few inorganic nanoparticles translated for human safety, diagnostic, and therapeutic use.
• The precise structure of their 3-4 nm silica cores remains largely unknown.

Purpose of the Study:

• To elucidate the exact core structure of ultrasmall silica nanoparticles.
• To understand the formation mechanism and stability of these nanoparticles.
• To correlate structural findings with synthesis scale-up and therapeutic potential.

Main Methods:

• Characterization using reverse-phase high-performance liquid chromatography.
• High-resolution imaging via cryogenic transmission electron microscopy.
• Computational analysis using coarse-grained simulations.

Main Results:

• Discovery of a well-defined pentagonal bipyramidal structure formed by seven primary silica nanoparticles.
• Identification of magic-size cluster formation and unusual stability.
• Rationalization of successful synthesis scale-up from 1 mL to 50 L.

Conclusions:

• The pentagonal bipyramidal core structure is key to the formation and stability of these clinically relevant nanoparticles.
• Understanding this structure provides insights into their self-therapeutic properties via ferroptosis in oncology.
• Chromatographic separation methods promise improved control over nanoparticle size distribution.