Design of one-shot graded foams as tunable delivery systems

Uniform and graded polycaprolactone tablet foams were fabricated through CO2-assisted physical foaming, providing a tunable material platform for controlling mass transport in functional delivery systems. Foam morphology was engineered with a controlled porosity gradient to regulate diffusion pathways through interconnected pores. A thermally stable model compound was incorporated at 1–10 (w/w, %) with encapsulation efficiencies above 95%. Morphological analysis by SEM revealed a systematic pore size transition from roughly 70 µm at the external layer to roughly 170 µm at the inner core, directly correlated with the applied saturation pressure. Drug release experiments demonstrated a two-stage kinetic behavior, governed initially by gradient-dependent diffusion followed by polymer degradation after a characteristic lag time, τ. The release rate scaled inversely with pore size, confirming the role of structural design in transport modulation. A five-parameter kinetic model was developed, integrating diffusion and pH-dependent degradation, and accurately predicting cumulative release up to 200 h. This study establishes a morphology-driven design approach for graded polymer foams, enabling predictive control of transport phenomena and offering a rational framework for the design of sustained-release materials and other porous functional systems.