Biophysical and biochemical data on hyaluronan (HA)-based dermal fillers strongly support their optimal use and design to meet specific requisites. Here, four commercially available (in Europe) HA “volumetric” fillers, among the most used in the clinical practice, have been characterized
in vitro
. Analyses revealed the highest amounts of water-soluble HA reported so far and provided hydrodynamic data for these soluble polymeric fractions. Volumetric gels exhibit a wide range of rigidity with most of them showing G’ values around 200-300Pa. They greatly differ in cohesivity. 1mL of gel hydrates up to 2.4–3.2mL. The products completely solubilize due to Bovine Testicular Hyaluronidase (BTH)’s action, thus predicting
in vivo
complete resorption. For the first time, filler degradation due to reactive oxygen species (ROS) was studied by rheological measurements and a rank in stability was established. Studies using Human Dermal Fibroblasts (HDF) indicated a positive biological response to the HA networks. Further, gel capacity to prompt collagen I, elastin and aquaporin3 synthesis was demonstrated, thus suggesting a positive effect on skin elasticity and hydration, besides the physical volumetric action. The findings are the first wide assessment of features for the volumetric class of HA-fillers and include first data on their resistance to degradation by ROS and biological effects on HDF. The study represents a valuable contribution to the understanding of HA-fillers, useful to optimize their use and manufacture.
Chemico-physical and biological characterization of hyaluronan-based dermal fillers is of key importance to differentiate between numerous available products and to optimize their use. These studies on fillers are nowadays perceived as a reliable approach to predict their performance in vivo. The object of this paper is a recent line of hyaluronic acid (HA)-based dermal fillers, Aliaxin®, available in different formulations that claim a complete facial restoration. The aim of the study is to provide biophysical and biological data that may support the clinical indications and allow to predict performance possibly with respect to similar available products. Aliaxin® formulations were tested for their content in soluble HA, water uptake capacity, rheological behavior, stability to enzymatic degradation, and for in vitro capacity to stimulate extracellular matrix components production. The formulations were found to contain a low amount of soluble HA and were equivalent to each other regarding insoluble hydrogel concentration. The different crosslinking degree declared by the producer was consistent with the trend in water uptake capacity, rigidity, viscosity. No significant differences in stability to enzymatic hydrolysis were found. In vitro experiments, using a full thickness skin model, showed an increase in collagen production in the dermoepidermal junction. Results support the claims of different clinical indications, the classification of products regarding hydro-, lift-action and the specifically suggested needle gauge for the delivery. The biological outcomes also support products effectiveness in skin structure restoration. These data predicted a better performance regarding hydro-action, tissue integration, clinical management during delivery, and a high durability of the aesthetic effect when compared to data on marketed similar products.
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