FDM-based 4D printing of sustainable PVA-Cassava fibre composites: a programmable platform for smart gastroretentive drug delivery.

With the advancing paradigm of smart and sustainable healthcare, four-dimensional (4D) printing and sustainable polymer composites have attracted increasing interest in the development of advanced drug delivery systems. Incorporating agricultural waste-derived fibres into polymer composites provides a sustainable strategy for producing functional printing materials. In this study, we fabricated 4D-printed gastroretentive platforms by fused deposition modelling (FDM) using poly(vinyl alcohol) (PVA)-Cassava fibre composite filaments. The effects of increasing either Eudragit® NE 30 D or Cassava fibre content (up to 15% w/w) on filament flexibility, shape programmability, and drug release were systematically investigated. All developed formulations yielded continuous filaments with smooth extrusion, high structural fidelity, and precise drug loading. While the reference formulation (5% w/w fibre, 5% w/w Eudragit®; F5E5) fractured during compression, increasing either component to 15% w/w improved flexibility, prevented structural failure, and enabled compression into capsules for convenient oral administration. Following capsule disintegration, the programmed structures recovered their original geometry. Notably, F15E5 (15% w/w fibre, 5% w/w Eudragit®) achieved a rapid shape recovery of 93.3 ± 3.6% within 30 min via water-triggered polymer relaxation. Both formulations exhibited a pronounced initial release followed by a slower release phase extending to 24 h. Korsmeyer-Peppas analysis indicated anomalous (non-Fickian) transport, consistent with combined diffusion and matrix relaxation/erosion. Overall, this study establishes a 4D printing platform for sequential gastroretentive drug delivery, combining capsule-mediated buoyancy with mechanical expansion, thereby paving the way for the development of next-generation adaptive oral dosage forms with programmable shape transformation and tuneable drug release behaviour.