Rheological Considerations of Pharmaceutical Formulations: Focus on Viscoelasticity

Abstract

Controlling rheological properties offers the opportunity to gain insight into the physical characteristics, structure, stability and drug release rate of formulations. To better understand the physical properties of hydrogels, not only rotational but also oscillatory experiments should be performed. Viscoelastic properties, including elastic and viscous properties, are measured using oscillatory rheology. The gel strength and elasticity of hydrogels are of great importance for pharmaceutical development as the application of viscoelastic preparations has considerably expanded in recent decades. Viscosupplementation, ophthalmic surgery and tissue engineering are just a few examples from the wide range of possible applications of viscoelastic hydrogels. Hyaluronic acid, alginate, gellan gum, pectin and chitosan are remarkable representatives of gelling agents that attract great attention applied in biomedical fields. This review provides a brief summary of rheological properties, highlighting the viscoelasticity of hydrogels with great potential in biomedicine.

Rheology of Complex Topical Formulations: An Analytical Quality by Design Approach to Method Optimization and Validation

“…At lower temperatures, most of the LVR response is higher. In line with this observation, the interaction between the temperature and the sample rest time also proved to have a statistically significant effect on this CAA, with lower temperatures and lower rest times, yielding higher LVR values [84][85][86]. At higher temperatures, material components have more thermal energy and, hence, a lower stress input is required to initiate flow.…”

Investigation of Crosslinking Parameters and Characterization of Hyaluronic Acid Dermal Fillers: From Design to Product Performances

“…Rheological characterization of the dermal filler allows for evaluation of the response of the material to mechanical forces during the injection and once implanted [ 6 , 18 ]. Characteristic shear thinning behavior allows the gels to flow easily during extrusion and remain in place after implantation [ 36 ].…”

“…Crosslinking density is correlated with hydrogel strength, which is the result of covalent crosslinking and intermolecular physical interactions, such as hydrogen bonding and physical entanglements [ 4 , 5 ]. In vitro hydrogel characterization, with a specific focus on viscoelastic behaviors, has been extensively reported, in order to compare hydrogel properties, correlate them with clinical performances and assist clinicians in selecting the appropriate attributes [ 5 , 6 , 7 , 8 , 9 ]. However, despite principal manufacturers of dermal fillers using the same crosslinking agent, 1,4-butanediol diglycidyl ether (BDDE), which is the most commonly used reagent for HA crosslinking in alkaline conditions, different technologies afford a plethora of dermal fillers with peculiar characteristics [ 7 , 10 ].…”

Development and Characterization of Thermosensitive and Bioadhesive Ophthalmic Formulations Containing Flurbiprofen Solid Dispersions

“…In particular, the formulations were subjected to oscillation measurements, which apply a constant shear stress value (chosen in the linear viscoelastic region, previously determined) and measure the viscoelastic response of the formulation expressed by the storage (G ′ ) and loss (G ′′ ) moduli, which are characteristic of the stored elastic energy and the viscous dissipated energy, respectively. It is known that the elastic and viscous moduli values and their ratios provide information about rheological characteristics and comparison of various viscoelastic formulations [85]. The oscillation measurements were performed as follows: The evaluations were conducted in triplicate [84].…”