Rheological and syringeability properties of highly concentrated human polyclonal immunoglobulin solutions

Area of Science:

• Biochemistry
• Materials Science
• Rheology

Background:

• Understanding the rheological properties of concentrated protein solutions like immunoglobulin G (IgG) is crucial for pharmaceutical formulation and delivery.
• Protein aggregation and intermolecular interactions significantly influence solution viscosity and injectability.
• Previous studies have explored viscosity but often lack detailed analysis of concentrated polyclonal IgG and its correlation with injection parameters.

Purpose of the Study:

• To investigate the relationship between protein concentration, aggregation, and viscosity in highly concentrated polyvalent immunoglobulin G (IgG) solutions.
• To analyze the rheological behavior of IgG solutions and correlate it with syringeability through hypodermic needles.
• To identify optimal conditions for injecting concentrated IgG solutions based on viscosity, flow rate, and needle characteristics.

Main Methods:

• Viscosity measurements of polyvalent immunoglobulin G (IgG) solutions at varying concentrations.
• Fitting viscosity data to the Mooney model to assess intermolecular interactions and particle shape.
• Syringeability tests evaluating injection force through hypodermic needles under different conditions.

Main Results:

• IgG solutions displayed Newtonian behavior at low concentrations and shear-thinning behavior at high concentrations.
• The Mooney model accurately described the viscosity, indicating IgG solutions behave as non-interacting hard particles, likely due to their polyclonal nature.
• Injection force increased with IgG concentration and flow rate but decreased with larger needle diameters, with an optimal injection zone identified below 30N.

Conclusions:

• The polyclonal nature of IgG prevents intermolecular interactions, leading to predictable rheological behavior described by the Mooney model.
• Rheological properties, particularly viscosity, are key determinants of injection force for concentrated IgG solutions.
• Optimal injection parameters can be defined to ensure safe and effective manual administration of immunoglobulin G therapies.