Evolution of myoglobin diffusion mechanisms: exploring pore and surface diffusion in a single silica particle

Area of Science:

• Biophysics
• Materials Science
• Physical Chemistry

Background:

• Myoglobin (Mb) is crucial for oxygen transport.
• Understanding protein diffusion in porous materials is vital for applications like drug delivery and biosensing.
• Silica nanoparticles offer a versatile matrix for protein encapsulation.

Purpose of the Study:

• To elucidate the mass transfer mechanism of myoglobin within silica particles.
• To investigate the influence of pH on myoglobin distribution and diffusion kinetics.
• To determine the contributions of pore and surface diffusion to myoglobin transport.

Main Methods:

• Absorption microspectroscopy was employed to study myoglobin distribution and kinetics.
• Analysis of intraparticle diffusion coefficient (D p) using a first-order reaction model.
• Evaluation of pore and surface diffusion models based on D p-(1+R) -1 plots at various pH levels.

Main Results:

• The highest myoglobin distribution ratio (R) was observed at pH 6.8, near the protein's isoelectric point.
• At pH 6.0, myoglobin diffusion occurred exclusively via surface diffusion.
• Pore diffusion became a significant factor at pH levels above 6.0, with diffusion hindered by slow desorption due to electrostatic charge.

Conclusions:

• pH significantly impacts myoglobin diffusion mechanisms within silica nanoparticles.
• Surface diffusion dominates at acidic pH, while pore diffusion increases with pH.
• Electrostatic interactions play a key role in myoglobin desorption and overall diffusion kinetics.