Surfactant Structure-Dependent Interactions with Modified Starch Nanoparticles Probed by Fluorescence Spectroscopy

Area of Science:

• Colloid and Surface Science
• Materials Chemistry
• Nanotechnology

Background:

• Hydrophobically modified starch nanoparticles (SNPs) often aggregate in aqueous solutions.
• Surfactants are commonly used to stabilize nanoparticles, but their specific interactions with modified SNPs require detailed investigation.

Purpose of the Study:

• To investigate the interactions between sodium dodecyl sulfate (SDS) and sodium dioctyl sulfosuccinate (AOT) with pyrene-modified starch nanoparticles (Py-SNPs) in water.
• To elucidate the mechanism by which surfactants influence the aggregation and stability of Py-SNPs.

Main Methods:

• Steady-state and time-resolved fluorescence spectroscopy were employed to monitor Py-SNP behavior.
• Fluorescence resonance energy transfer (FRET) experiments were conducted using naphthalene-labeled SNPs (Np-SNPs) to confirm aggregate disruption.
• Critical micelle concentration (CMC) of SDS was considered in relation to observed interactions.

Main Results:

• SDS disrupted Py-SNP aggregates at concentrations significantly lower than its CMC.
• SDS-Py-SNP interactions below CMC were attributed to inclusion complex formation, leading to electrostatic stabilization.
• No significant interaction was observed between AOT and Py-SNPs at comparable concentrations, unlike SDS.
• Pyrene excimer formation indicated interactions with hydrophobic pyrene aggregates only above the SDS CMC.

Conclusions:

• SDS, below its CMC, stabilizes hydrophobically modified starch nanoparticles through inclusion complex formation and electrostatic stabilization, not by directly interacting with hydrophobic domains.
• This mechanism offers a novel approach for stabilizing modified SNPs in aqueous dispersions.
• The findings suggest potential future applications for SDS-stabilized modified SNPs.