Diffusion-Controlled Release of Bromelain from κ-Carrageenan Nanocomposite Hydrogels Reinforced with Bio-Derived Nanofillers

Biopolymer hydrogels are attractive matrices for localised enzyme and drug delivery owing to their intrinsic biocompatibility, biodegradability, and controlled release capacity. In this study, κ-carrageenan hydrogels were engineered as enzyme-delivery systems by reinforcing the matrix with cellulose nanocrystals (CNC) or chitin nanowhiskers (ChNW) and loading bromelain as a model enzyme. The objective was to evaluate how nanofiller chemistry and morphology influence network structure and release behaviour. Parallel fabrication under identical conditions enabled a direct CNC-ChNW comparison. CNC reinforcement compacted the network and reduced swelling, whereas ChNW produced more hydrated and open architectures. Both fillers enhanced surface wettability, while their concentration modulated bulk hydration and diffusivity. Bromelain release over 24 h followed diffusion-controlled kinetics, tunable by filler type and loading. Quantitative topography and pore-size mapping supported structure-function correlations between morphology and transport. All hydrogels were bio-based, biodegradable, and fully cytocompatible, highlighting their suitability for sustainable biomedical applications. Overall, this work provides a quantitative structure-property-function framework for designing enzyme-active κ-carrageenan systems for tunable bromelain release and related biomedical applications.