Controlled pH stability and adjustable cellular uptake of mixed-charge nanoparticles

Area of Science:

• Materials Science
• Nanotechnology
• Surface Chemistry

Background:

• Nanoparticles functionalized with mixed self-assembled monolayers (m-SAMs) exhibit pH-dependent stability.
• The precipitation point (pH(prec)) is critical for nanoparticle application and handling.

Purpose of the Study:

• To investigate the relationship between m-SAM composition, particle size, and pH-dependent precipitation.
• To explore how these factors influence nanoparticle cellular uptake.

Main Methods:

• Synthesis of nanoparticles functionalized with mixed self-assembled monolayers (m-SAMs) containing varying ratios of charged thiols.
• Characterization of nanoparticle stability and precipitation pH (pH(prec)) across a range of pH values.
• Assessment of cellular uptake of functionalized nanoparticles with different surface charges and compositions.

Main Results:

• Nanoparticles with m-SAMs are stable at low and high pH but precipitate at pH(prec) where charges balance.
• pH(prec) can be precisely tuned between approximately 4 and 7 by altering the m-SAM ligand ratio or particle size.
• Nanoparticle surface charge and m-SAM composition significantly impact cellular uptake efficiency.
• Positively charged thiols in m-SAMs facilitate cellular uptake even for nanoparticles with a net negative charge.

Conclusions:

• Mixed self-assembled monolayers provide a versatile platform for controlling nanoparticle precipitation pH.
• Tunable surface chemistry of nanoparticles influences their interaction with biological systems, including cellular uptake.
• Strategic design of m-SAMs can overcome charge-related barriers to nanoparticle delivery.