Molecular Dynamics Simulations and Experimental Studies of the Microstructure and Mechanical Properties of a Silicone Oil/Functionalized Ionic Liquid-Based Magnetorheological Fluid

Comprehensive Analysis of the Structural Evolution and Dynamic Mechanical Behavior of Ferrofluids through Coarse-Grained Molecular Dynamics and Experimental Testing

Understanding and predicting the relationship between the dynamic structure and dynamic mechanical behavior of ferrofluids at the mesoscale presents a significant challenge. Therefore, in this study, a ferrofluid model that considered the molecular structure of the carrier liquid was constructed to perform coarse-grained molecular dynamics simulations of the mesoscale structural evolution and internal particle arrangement characteristics of ferrofluids under the influence of a magnetic field. Subsequently, oscillatory shear deformation was applied to further investigate the mechanical properties of ferrofluids under dynamic strain, as well as the deformation and disruption of their orientational structures. The simulations show that the columnar aggregation of magnetic particles imparts typical viscoelastic characteristics to the ferrofluid, and these aggregated structures gradually deform and break down as the strain amplitude increases. During dynamic oscillatory shear deformation, the enhancement of the magnetic field allows the aggregated structure of magnetic particles to exhibit better resistance to deformation, thereby improving the absorption and dissipation of mechanical energy. The dynamic mechanical properties of ferrofluids obtained from coarse-grained simulations closely align with the experimental results under moderate to high magnetic fields, allowing for a certain degree of predictive capability regarding the dynamic mechanical behavior of ferrofluids.

Release Kinetics of Metronidazole from 3D Printed Silicone Scaffolds for Sustained Application to the Female Reproductive Tract

Sustained vaginal administration of antibiotics or probiotics has been proposed to improve treatment efficacy for bacterial vaginosis. 3D printing has shown promise for development of systems for local agent delivery. In contrast to oral ingestion, agent release kinetics can be fine-tuned by the 3D printing of specialized scaffold designs tailored for particular treatments while enhancing dosage effectiveness via localized sustained release. It has been challenging to establish scaffold properties as a function of fabrication parameters to obtain sustained release. In particular, the relationships between scaffold curing conditions, compressive strength, and drug release kinetics remain poorly understood. This study evaluates 3D printed scaffold formulation and feasibility to sustain the release of metronidazole, a commonly used antibiotic for BV. Cylindrical silicone scaffolds were printed and cured using three different conditions relevant to potential future incorporation of temperature-sensitive labile biologics. Compressive strength and drug release were monitored for 14d in simulated vaginal fluid to assess long-term effects of fabrication conditions on mechanical integrity and release kinetics. Scaffolds were mechanically evaluated to determine compressive and tensile strength, and elastic modulus. Release profiles were fitted to previous kinetic models to differentiate potential release mechanisms. The Higuchi, Korsmeyer-Peppas, and Peppas-Sahlin models best described the release, indicating similarity to release from insoluble or polymeric matrices. This study shows the feasibility of 3D printed silicone scaffolds to provide sustained metronidazole release over 14d, with compressive strength and drug release kinetics tuned by the fabrication parameters.