Microfluidic Platform for Microparticle Fabrication and Release of a Cathepsin Inhibitor

Abstract

Cathepsins are a family of cysteine proteases responsible for a variety of homeostatic functions throughout the body, including extracellular matrix remodeling, and have been implicated in a variety of degenerative diseases. However, clinical trials using systemic administration of cathepsin inhibitors have been abandoned due to side effects, so local delivery of cathepsin inhibitors may be advantageous. In these experiments, a novel microfluidic device platform was developed that can synthesize uniform, hydrolytically degradable microparticles from a combination of poly(ethylene glycol) diacrylate (PEGDA) and dithiothreitol (DTT). Of the formulations examined, the 10-polymer weight percentage 10 mM DTT formulation degraded after 77 days in vitro. A modified assay using the DQ Gelatin Fluorogenic Substrate was used to demonstrate sustained release and bioactivity of a cathepsin inhibitor (E-64) released from hydrogel microparticles over 2 weeks in vitro (up to ∼13 μg/mL released with up to ∼40% original level of inhibition remaining at day 14). Altogether, the technologies developed in this study will allow a small-molecule, broad cathepsin inhibitor E-64 to be released in a sustained manner for localized inhibition of cathepsins for a wide variety of diseases.

Impact statement

Local delivery of cathepsin inhibitors may reduce progression of a wide variety of diseases. This work provides two contributions toward this goal. First, a novel microfluidic device was used to fabricate uniform, hydrolytically degradable poly(ethylene glycol) diacrylate/dithiothreitol microparticles loaded with the cathepsin inhibitor E-64. Subsequently, commercially available fluorogenic assays were validated to simultaneously quantify release and bioactivity of the inhibitor from the biomaterial carriers.