Factors Affecting the Rheological Measurement of Hyaluronic Acid Gel Fillers

Area of Science:

• Dermatology
• Materials Science
• Rheology

Background:

• Increasing availability of dermal fillers necessitates scientifically validated comparisons.
• Rheological properties are a key focus for evaluating filler performance.
• Variability in instrument settings impacts analytical results, highlighting the need for standardized methods.

Purpose of the Study:

• To propose preferred measurement settings for rheological analysis of hyaluronic acid (HA) fillers.
• To demonstrate the impact of different measurement settings on commercial HA fillers.
• To provide a basis for more consistent and comparable rheological data.

Main Methods:

• Rheological properties of 8 HA fillers were assessed.
• Measurements were conducted using an Anton Paar MCR 301 with a PP-25 system.
• A frequency sweep from 10 to 0.01 Hz at 0.1% strain, 1 mm gap, and 25°C was employed, with a 30-min relaxation period.

Main Results:

• Significant variations in elastic modulus (G') were observed, ranging from 1.6 to 7.4 times for the same product.
• These differences underscore the sensitivity of rheological measurements to experimental parameters.
• Previously published data corroborate the observed variability.

Conclusions:

• Discrepancies in rheological data are largely attributable to variations in measurement settings.
• Standardization of rheometry settings is essential for reliable product comparison.
• The elastic modulus (G') is proposed as a straightforward parameter for differentiating HA filler products.