Rheological Evaluation of the Physical Properties of Hyaluronic Acid Dermal Fillers

September 2011 | Volume 10 | Issue 9 | Original Article | 974 | Copyright © 2011

David Stocks BSc (Hons),a Hema Sundaram MD,b Jason Michaels MD,c Manzer J. Durrani PhD,d Mitchell S. Wortzman PhD, d Diane B. Nelson BSN MPHd

aIntertek MSG, Redcar, United Kingdom bSundaram Dermatology, Cosmetic & Laser Surgery Center, Rockville, MD and Fairfax, VA cAspire Cosmetic MedCenter, Las Vegas, NV dMedicis Aesthetics Incorporated, Scottsdale, AZ

Abstract

Background: Hyaluronic acid (HA) gels are commonly injected into the skin to lift rhytides and to improve facial appearance. The different processes used in their manufacture and formulation yield products with unique physical characteristics that play an important role in predicting their clinical performance.
Objective: The following rheologic evaluation was performed to objectively measure the physical characteristics of HA dermal filler products derived from similar bacterial sources and containing the same butanediol diglycidyl ether cross-linker, but formulated using different manufacturing techniques. The objective of this study was to evaluate the physical characteristics of two distinct families of HA products, thereby providing clinicians with a greater understanding of these products' attributes and the ability to optimize their use in the treatment of patients seeking facial rejuvenation.
Materials and Methods: The physical properties of commercially-available dermal fillers containing HA were evaluated using rheologic testing methods under clinically-relevant conditions. Additionally, light microscopy was used to assess the particulate nature of each product.
Results: The gels tested demonstrated a broad range of elasticity, firmness and viscosity. Light microscopy confirmed the particulate nature of each product and revealed HA particles of varying size and distribution.
Conclusion: This rheologic evaluation demonstrates that differences exist among the HA products tested including gel elasticity, viscosity, and the range and distribution of gel particle sizes. Understanding the distinct physical characteristics of different HA dermal fillers and how these characteristics may predict their clinical behavior can assist clinicians in achieving the desired results in patients seeking facial rejuvenation.

J Drugs Dermatol. 2011;10(9):974-980.

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INTRODUCTION

Hyaluronic acid (HA) is a glycosaminoglycan that consists of repeating units of glucuronic acid and N-acetyl-glucosamine (hyaluronan) and which readily dissolves in water to form a viscous gel. It is found in the extracellular matrix of many tissues, and approximately one-half of the HA in the human body is found in the skin where it plays an important role in providing structure and maintaining normal moisture content.1 During the aging process, the HA content of the dermis decreases and this contributes to volume loss, diminished dermal water-binding capacity and the development of rhytides.2 As HA is a physiologic component of human skin, HA-containing products are well-suited for use as dermal fillers in treating patients seeking facial rejuvenation.

Commercially-available HA dermal fillers are similar in many respects. They all contain HA obtained through the fermentation of Streptococcus sp. bacteria and the HA molecules are joined together using cross-linkers such as butanediol diglycidyl ether (BDDE) to prevent rapid in vivo enzymatic and oxidative degradation.1,3 Despite these similarities, HA dermal fillers differ in their physical characteristics and therefore may behave clinically in different ways, based upon the manufacturing methods used,2,3 which determine the type and extent of HA cross-linking and the size and concentration of HA particles.1,3

For example, five HA dermal fillers contain HA derived from similar bacterial cultures and are stabilized with the same BDDE

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