Peptide functionalized gold nanoparticles: the influence of pH on binding efficiency

Area of Science:

• Nanotechnology
• Bioconjugation Chemistry
• Materials Science

Background:

• Gold nanoparticles (AuNPs) are versatile nanomaterials with applications in diagnostics and therapeutics.
• Surface functionalization of AuNPs with peptides and polymers like polyethylene glycol (PEG) is crucial for targeted delivery and biocompatibility.
• Understanding the influence of environmental factors, such as pH, on peptide attachment is essential for reproducible synthesis.

Purpose of the Study:

• To synthesize mixed monolayer gold nanoparticles (AuNPs) functionalized with polyethylene glycol (PEG) and specific targeting peptides.
• To investigate the impact of pH on the attachment efficiency and stability of cysteine-containing peptides to AuNPs.
• To determine the optimal pH for co-functionalization of AuNPs with PEG and peptides, including RGD and H5WYG.

Main Methods:

• Synthesis of AuNPs functionalized with PEG and three distinct peptides: a receptor-mediated endocytosis peptide, an endosomal escape peptide (H5WYG), and an RGD peptide (CRGDK).
• Manipulation of pH conditions around the isoelectric points of the peptides prior to co-functionalization.
• Characterization of peptide attachment using dynamic light scattering (DLS), UV-Vis spectroscopy, FTIR, and photoluminescence spectroscopy.

Main Results:

• Successful synthesis of mixed monolayer AuNPs with PEG and peptides.
• UV-Vis spectroscopy, protein assays, and photoluminescence confirmed peptide attachment.
• A pH of approximately 8 was identified as optimal for robust cysteine binding and overall nanoparticle stability, regardless of the specific peptide used.

Conclusions:

• The study demonstrates that pH plays a critical role in the successful conjugation of peptides to PEGylated AuNPs.
• An optimal pH of ~8 enhances the binding and stability of peptides via cysteine residues to the AuNP surface.
• These findings provide a foundation for optimizing the synthesis of functionalized AuNPs for biomedical applications.