pH and ion strength modulated ionic species loading in mesoporous silica nanoparticles

Area of Science:

• Materials Science
• Nanotechnology
• Physical Chemistry

Background:

• Mesoporous silica nanoparticles (MSN) are versatile hosts for guest molecules in biomedical applications.
• Controlling guest molecule loading within the silica matrix is crucial for optimizing MSN performance.
• Existing methods for modulating loading require further refinement for practical applications.

Purpose of the Study:

• To investigate the impact of pH and ion strength on the loading of charged guest molecules into mesoporous silica nanoparticles (MSN).
• To elucidate the role of electrostatic interactions in governing the adsorption and selectivity of charged species within MSN.
• To establish simple modulation strategies for molecule loading and permselectivity in MSN.

Main Methods:

• Utilized MCM-41 as a model MSN host material.
• Employed methylviologen (MV2+) and 1,5-naphthalene disulfonate (NDS2-) as representative charged guest molecules.
• Systematically varied solution pH (3.0-8.0) and sodium chloride (NaCl) concentration to assess their effects on guest molecule loading.

Main Results:

• Increasing pH from 3.0 to 8.0 enhanced MV2+ loading while decreasing NDS2- loading, attributed to altered electrostatic interactions.
• Addition of NaCl reduced electrostatic interactions, impacting both electrostatic rejection and accumulation of charged guest molecules.
• Demonstrated a clear correlation between solution conditions and the loading capacity and selectivity of MSN.

Conclusions:

• pH and ion strength are effective and simple parameters for modulating the loading of charged molecules in MSN.
• These findings provide guidance for optimizing molecule loading, transport, controlled release, and sensor development based on MSN.
• The study highlights the importance of electrostatic interactions in designing functional MSN systems.