Cohesion of Hyaluronic Acid Fillers: Correlation Between Cohesion and Other Physicochemical Properties

Abstract

BACKGROUNDThere are several published articles on characterization of fillers, describing methods for both chemical and physicochemical characterization. Recently a lot of focus has been on the development of methods for measuring cohesion of hyaluronic acid (HA) fillers.OBJECTIVEThe aim of this study is to investigate and compare the drop-weight method and the correlation between cohesion and other physicochemical properties using a variety of HA fillers.MATERIALS AND METHODSHA fillers covering several product families and manufacturing techniques were used. The HA fillers also covered a range of HA concentrations from 12 to 24 mg/mL. Cohesion was determined using sensory evaluation and the drop-weight method. Other physicochemical properties evaluated were rheology and the swelling factor.RESULTSIn this study, it was verified that values obtained by the drop-weight method reflect the perceived cohesion very well. The correlation with rheology is affected by the HA concentration in the products. A remarkably good correlation between swelling factor and cohesion was found.CONCLUSIONCohesion correlates with other physicochemical methods. It could be discussed whether there is a need for a separate cohesion method because other already established physicochemical methods such as rheology and swelling factor can describe the underlying properties that affect cohesion.

Hyaluronan-based hydrogels as dermal fillers: The biophysical properties that translate into a “volumetric” effect

“…The manufacturing parameters directly related to this property have still to be fully identified. However, it is noteworthy that the data obtained here are in agreement with a correlation previously suggested between swelling /rigidity and cohesive properties: the higher the water uptake ability and the lower the G’ value, the higher the cohesivity of the gel [22].…”

“…The projection capacity is the main characteristic for a “volumetric” filler and is related to the gel’s rheological properties, especially to rigidity. Compared to the literature, the gels tested here exhibited high G’ values (Fig 4A) that are in agreement with already reported data and consistent with their volumizing indications and suggested application site [22]. While J V , T RH4 and A SV presented similar G’ values (200-300Pa) in the physiologically relevant frequency range, R L stands out with far higher rigidity thus suggesting, for this filler, the highest projection capacity.…”

“…Fillers ranking in terms of complex viscosity resembles, as expected, the one in rigidity (Fig 4B). Besides affecting ease of delivery, viscosity, along with cohesivity, is supposed to play a key role in tissue integration pattern [3, 22]. Cohesivity, a recently investigated parameter, is conceived as a measure of the integrity maintenance of the gel in physiological conditions.…”

“…The literature is now in agreement on the importance of the biophysical characterization of HA fillers to guide physicians in selecting the most appropriate product, depth of injection and administration technique for an optimal clinical outcome [1, 3, 6, 22–27]. Additionally, such evaluations, combined with clinical studies, are key to tailor gels towards specific requisites.…”

Toward Physicochemical and Rheological Characterization of Different Injectable Hyaluronic Acid Dermal Fillers Cross-Linked with Polyethylene Glycol Diglycidyl Ether

“…For a more complete assessment of cohesivity, we integrated the study of the behavior in water (physiological condition), the rheological data and the evaluation of the resistance to elongation. The protocol proposed by Sundaram represents a qualitative way to investigate this intrinsic property based on the subjective assessment of photographs without the discrimination of large or small particles [ 18 ]. Many studies correlated cohesivity with the rheological properties of the filler.…”