Design parameter effects on controlled drug delivery through implantable hydrogels.

Glioblastoma recurrence after surgery is a major contributor to its high mortality, primarily occurring near the original tumour margin. Various hydrogels have been developed to fill the post-surgical cavity and deliver drugs to the surrounding brain tissue to eliminate residual cells. However, the impact of tissue, hydrogel, and drug properties on delivery outcomes remains unclear. Here, a parametric study is conducted to investigate these effects using mathematical modelling. The results show that post-surgical oedema strongly influences delivery: longer duration or delayed onset of oedema can homogenise drug distribution, with delayed onset yielding a larger and more sustained therapeutic drug volume. Hydrogels with higher permeability or lower drug affinity enhance early concentration and distribution but decline faster over time. Drugs with lower intracellular partitioning improve early efficacy, whereas those with stronger binding to cellular or extracellular components sustain delivery longer. Lower transvascular permeability and slower elimination further enhance outcomes, while extracellular diffusivity must be optimised to maximise drug concentration and distribution. These findings provide guidance for optimising hydrogel-based drug delivery systems to prevent glioblastoma recurrence.