Evaluation of a rapid-release mitomycin C-loaded porous microcapsule formulation (MitoCap) in a human...

Intravesical mitomycin C (MMC) is limited by short bladder exposure and incomplete delivery to residual tumour tissue. We developed MitoCap, a porous MMC-loaded microcapsule formulation, and evaluated its formulation properties and antitumour performance in a human three-dimensional urothelium-tumour model (3D-UHU-TU). Microcapsules were produced by electrohydrodynamic atomisation using 2% or 5% poly(lactic-co-glycolic acid) (PLGA). Compared with 5% PLGA, the 2% formulation generated smaller microcapsules (2.90 ± 0.30 versus 4.03 ± 0.81 µm), greater apparent surface porosity and faster MMC release, with approximately 60% released within 15 min. The 2% formulation achieved an MMC loading capacity of 4.99 ± 0.16% (w/w), corresponding to 95.78 ± 3.09% recovery relative to the theoretical loading, and was selected for biological evaluation. The 3D-UHU-TU model integrates RT112 or T24 bladder cancer spheroids into a differentiated, urine-tolerant human urothelium, enabling tumour and urothelial responses to be assessed within the same construct. FITC-loaded microcapsules increased fluorescent model cargo signal within tumour regions compared with equivalent free FITC. Following 1 h apical exposure and 72 h recovery, MitoCap increased tumour-associated cleaved caspase-3 and tumour cell death relative to dose-matched free MMC. Tumour cell death increased from 62.3 ± 7.9% to 94.2 ± 1.3% in RT112 models and from 36.6 ± 4.7% to 52.8 ± 4.8% in T24 models, without increasing urothelial cell death relative to dose-matched free MMC. These findings support MitoCap as a rapid-release intravesical MMC formulation and demonstrate the value of compartment-resolved human urothelium-tumour models for evaluating local drug delivery.