smartPearls^® for dermal bioavailability enhancement - Long-term stabilization of suspensions by viscoelasticity

smartPearls^® are a novel dermal delivery system based on mesoporous (pores 2-50 nm) particles, developed in 2014. Their pores can be loaded with active which is long-term stabilized in its amorphous state. The increased saturation solubility by the amorphous state leads to an increased dermal bioavailability of poorly soluble actives. To avoid sedimentation of the porous particles (3-50 µm) in dermal formulations, viscoelastic gels were developed using ι-carrageenan, polyacrylate and the viscoelastic Kühne salad dressing as a reference from food industry. Silica particles (company Grace/US, 50 and 150 µm) were loaded into the gels and long-term stability was assessed by a VIS sedimentation test. Furthermore, the gels were characterized by analytical centrifugation (LUMiSizer^®) to assess the critical rpm/g values, allowing to order them after their absolute viscoelastic stabilizing ability. Characterization was complemented by rotation rheology, amplitude sweep and a frequency sweep analysis for the determination of elastic and viscous moduli G' and G'' at varying conditions. Based on the throughout characterization, polymers can be selected to sufficiently stabilize dermal formulations even with large sized smartPearls^® - the prerequisite for using this delivery system in dermal products.