Expanding Analytical Tools for Characterizing Ultrasmall Silica-based Nanoparticles.

Area of Science:

• Nanotechnology
• Analytical Chemistry
• Biomedical Engineering

Background:

• C' dots are hybrid nanoparticles with a silica core, near-infrared dye, and PEG outer layer.
• CycloRGDyC-Cy5-C' dots are the first C' dots approved for human clinical trials, targeting integrins.
• High-resolution analytical methods are crucial for the continued clinical development of C' dots.

Purpose of the Study:

• To investigate the applicability of reversed-phase high-performance liquid chromatography (RP-HPLC) for analyzing cycloRGDyC-Cy5-C' dots.
• To assess the resolution and heterogeneity of C' dots using RP-HPLC.
• To explore a novel method for C' dot ligand release to quantify cycloRGDyC.

Main Methods:

• Utilized RP-HPLC, a technique typically used for peptides and proteins, to analyze C' dots.
• Observed and analyzed C' dot peak profiles and chromatographic behavior.
• Developed and employed a thiol-mediated release mechanism to detach cycloRGDyC ligands from C' dots.

Main Results:

• RP-HPLC demonstrated excellent resolution of C' dots, revealing significant nanoparticle heterogeneity.
• Observed unusual and variable RP-HPLC peak shapes, potentially due to surface conformational or charge heterogeneity from PEGylation.
• Successfully released cycloRGDyC ligands via a thiol-mediated reaction, enabling direct quantification.

Conclusions:

• RP-HPLC is a valuable high-resolution technique for analyzing the heterogeneity of C' dots.
• The observed peak variability in RP-HPLC suggests surface complexities of C' dots that warrant further investigation.
• A novel thiol-mediated ligand release method provides a direct approach for quantifying C' dot ligands.