In this study, we use modified cationic nanocarriers as vehicles for the intracellular delivery of therapeutic siRNA. After developing nanocarrier formulations with appropriate pKa, size, swellability, and cytocompatibility, we investigated the importance of siRNA loading methods by studying the impact of the pH and time over which siRNA is loaded into the nanocarriers. We concentrate on diffusion-based loading in the presence and absence of electrostatic interactions. siRNA release kinetics were studied using samples prepared from nanocarriers loaded by both mechanisms. In addition, siRNA delivery was evaluated for two formulations. While previous studies were conducted with samples prepared by siRNA loading at low pH values, this research provides evidence that loading conditions of siRNA affect the release behavior. This study concludes that this concept could prove advantageous for eliciting prolonged intracellular release of nucleic acids and negatively charged molecules, effectively decreasing dose frequency and contributing to more effective therapies and improved patient outcomes. In addition, our findings could be leveraged for enhanced control over siRNA release kinetics, providing novel methods for the continued optimization of cationic nanoparticles in a wide array of RNA interference-based applications.

Hydrogels are used in drug delivery applications, chromatography, and tissue engineering to control the rate of solute transport based on solute size and hydrogel-solute affinity. Ongoing modeling efforts to quantify the relationship between hydrogel properties, solute properties, and solute transport contribute toward an increasingly efficient hydrogel design process and provide fundamental insight into the mechanisms relating hydrogel structure and function. However, here we clarify previous conclusions regarding the use of mesh size in hydrogel transport models. We use 3D geometry and hydrogel network visualizations to show that mesh size and junction functionality both contribute to the mesh radius, which determines whether a solute can diffuse within a hydrogel. Using mesh radius instead of mesh size to model solute transport in hydrogels will correct junction functionality-dependent modeling errors, improving hydrogel design predictions and clarifying mechanisms of solute transport in hydrogels.