Biodegradable sodium citrate-treated hyaluronic acid microspheres for genicular artery embolization

Genicular artery embolization (GAE) using microparticulate embolic agents has recently been shown to improve pain and function in knee osteoarthritis (OA) patients. Despite encouraging outcomes, current clinical embolics are repurposed from non-GAE applications and remain suboptimal due to non-degradability or non-spherical shape, highlighting a need for biodegradable microspherical embolics specifically designed for GAE. Here, we engineered 1,4-butanediol diglycidyl ether (BDDE)-crosslinked hyaluronic acid (HA) microspheres with properties fine-tuned for GAE using a salt treatment approach, targeting a size range of ∼75-300 μm and degradation time of ∼48 h. Sodium citrate (Cit)-treated HA (HACit) microspheres with tunable properties were fabricated via emulsion crosslinking in the presence of varying Cit concentrations (0-20% w/v, named HACit-0 to HACit-20). >92% of microspheres measured between 75-300 µm. Treatment with 10% Cit (HACit-10) reduced the average microsphere size (from 195 ± 55 µm to 151 ± 53 µm), decreased the swelling ratio (from 24.3 ± 3.5 to 7.4 ± 0.1), and prolonged the in vitro degradation time (from 33 ± 3 h to 56 ± 4 h) compared to untreated microspheres (HACit-0). In a microfluidic occlusion test, HACit-10 microspheres exhibited enhanced strength to stably block microchannels, while HACit-0 microspheres failed to cause obstructions. NMR analysis verified complete Cit removal after microsphere washing, leaving FDA-approved BDDE-crosslinked HA as the sole embolic material. Cytotoxicity assessments using human umbilical vein endothelial cells (HUVECs) and human dermal fibroblasts (HDFs) demonstrated cytocompatibility of HACit-10 microspheres. Collectively, HACit-10 microspheres fulfilled the proposed design criteria, representing a promising embolic agent for GAE. STATEMENT OF SIGNIFICANCE: Knee osteoarthritis (OA) is the most common joint disease, with pain being the most prominent symptom. Genicular artery embolization (GAE) provides an alternative option for a substantial subset (∼20%) of OA patients who fall into a treatment gap-those unresponsive to conservative treatments yet ineligible for total knee replacement. Hyaluronic acid (HA) microspheres are promising candidates for developing GAE-indicated embolics, as HA-based products are biocompatible, biodegradable, non-immunogenic, and FDA-approved for intra-articular injections, facilitating clinical translation. However, achieving an optimal balance of size, mechanical properties, and degradation time is challenging through crosslinker concentration adjustment alone. This study employs a recently developed salt treatment method to fabricate HA microspheres with suitable size, enhanced mechanical strength, and fine-tuned degradation kinetics, tailored for GAE.