Encapsulation of hydroxycamptothecin within porous and hollow poly(l-lactide-co-ε-caprolactone) microspheres as a floating delivery system for intravesical instillation†

Intravesical instillation is an effective post-treatment for bladder cancer performed by delivering medications directly into the bladder to target the remaining cancer cells. The current study thus aimed to develop porous poly(L-lactide-co-ε-caprolactone) (PLCL) microspheres encapsulated with 10-hydroxycamptothecin (HCPT) via microfluidics to serve as a drug delivery system with persistent floating capacity and sustained HCPT-release property for intravesical instillation. A microfluidic device was designed to fabricate PLCL microspheres and encapsulate HCPT (HCPT-MS) within them; methanol and tridecane were introduced into an oil phase as a co-solvent and pore-forming agent, respectively, to regulate the floating ability of microspheres. The physicochemical properties of the resulting microspheres were characterized, and the floating behavior, release profile and anti-tumor effects of HCPT-MS were investigated. The obtained spherical HCPT-MS were 119.23 μm in size, monodisperse, and featured a porous concave surface and hollow structure. The encapsulation efficiency and drug loading of HCPT within HCPT-MS was around 67% and 4.9%, respectively. HCPT-MS exhibited impressive floating capabilities in water, PBS and artificial urine even in a simulated bladder dynamic environment. These microspheres remained afloat after being subjected to 90 repeated simulated urination processes. The sustained release of HCPT from these floating microspheres lasted for more than 10 days. The IC50 (half maximal inhibitory concentration) of HCPT-MS was calculated to be 52.14 μg mL⁻¹. T24 cells (human bladder cancer cells) when cultured with HCPT-MS at such a concentration were severely inhibited, and the inhibition further enhanced with an increase in culture time. Hence, the feasibility of the current porous and floating HCPT-MS as a formulation for intravesical instillation to deliver medications into the bladder with sustained release and stability was thus substantiated.