(150b) High Throughput Platform for Macromolecular Transport Screening

The mass transport of a therapeutic injected into the subcutaneous tissue is dictated by physiochemical properties of the molecule such as size and electrostatic charge. Bioavailability and efficacy of the therapeutic formulation depend on efficient transport of the molecule from the injection site to lymphatic or blood vessels. In vitro transport screening platforms provide insights into the effects of tissue and therapeutic properties on macromolecular transport through biological barriers. In this work, we focus on Transwell macromolecular recovery platform, which is an economical and high-throughput method, to systematically evaluate effects of extracellular matrix components (e.g. collagen types I, II and III, and hyaluronic acid (HA)) on mass transport properties of model macromolecules. Transport of macromolecules which are representative of current therapeutics in subcutaneous injections was examined.

We demonstrate that macromolecular transport within collagen hydrogels is inversely related to the hydrodynamic radius of the diffusing macromolecules. Blended collagen hydrogels containing collagen type I and II, or I and III had altered fibril morphologies (smaller fibril formation) compared to pure collagen type I hydrogels. The smaller fibrils of blended collagen hydrogels resulted in decreased molecular mass recovery rate compared to pure collagen type I gels. Transport through combined collagen type I and HA (ColHA) hydrogels was also assessed. Increasing HA concentration within the ColHA hydrogels decreased macromolecular recovery due to increased viscosity within the matrix. The inverse relationship between hydrodynamic radius of the diffusing molecules and recovery rates persisted in both blended collagen and ColHA hydrogels.

Recovery rates of large molecules such as immunoglobulin G (IgG), a molecule similar in size to therapeutic antibodies, were highly sensitive to HA concentration in col hydrogels. Smaller molecules, such as myoglobin and lysozyme, that are similar in size to insulin, experience electrostatic effects as HA concentration increases within collagen gels. Recovery of macromolecules in HA solution was a function of both electrostatic and steric interactions. Our results demonstrate that the Transwell platform can be utilized for systematic evaluation of therapeutic transport as a function of molecular characteristics. The results presented can inform biotherapeutic physiochemical properties for efficient transport within the subcutaneous tissue.