Elucidating Silver Nanocluster-Protein Binding Mechanism: From Ensemble Measurements to Single-Particle Dynamics.

Area of Science:

• Nanomaterials science
• Biophysics
• Biochemistry

Background:

• Classical protein corona formation on larger nanoparticles influences their biological fate.
• Understanding protein interactions with ultrasmall nanomaterials is critical for their application.
• Silver nanoclusters (AgNCs) represent a class of ultrasmall nanomaterials with unique properties.

Purpose of the Study:

• To investigate the interaction mechanism between ultrasmall glutathione-capped silver nanoclusters (GSH-AgNCs) and bovine serum albumin (BSA).
• To determine if AgNCs form a protein corona or a different type of complex with proteins.
• To provide mechanistic insights for the rational design of AgNCs in biomedical applications.

Main Methods:

• Synthesis and characterization of GSH-AgNCs.
• Ensemble-averaged fluorescence spectroscopy, ζ-potential measurements, and isothermal titration calorimetry.
• Single-particle fluorescence techniques, including fluorescence correlation spectroscopy, circular dichroism, and synchronous fluorescence measurements.

Main Results:

• BSA-to-AgNCs binding stoichiometry indicated a nanocluster-rich binding regime, below the threshold for stable protein corona formation.
• Fluorescence correlation spectroscopy revealed a hydrodynamic radius smaller than expected for a protein corona.
• Circular dichroism and synchronous fluorescence confirmed that BSA retains its native secondary structure upon association with AgNCs.

Conclusions:

• Ultrasmall AgNCs associate with proteins via complex formation, not a classical protein corona.
• BSA maintains its native structure when interacting with AgNCs.
• This study provides a mechanistic understanding crucial for developing AgNC-based biosensors and biomedical devices.