Optimization and Physicochemical Characterization of Chitosan Nanoparticles Encapsulating Extracts from Three Colored Opuntia ficus-indica Peels Using Box–Behnken Design

Recent research shows a paradigm shift in using agro-industrial byproducts, turning food waste into valuable resources. However, oxidative sensitivity and low stability limit their use, requiring new technologies. Opuntia Ficus Indica peels (OPE) from red, green, and yellow cultivars are rich in phytochemicals with color-dependent compositional differences as revealed by LCMS analysis. Encapsulating OPE into chitosan nanoparticles (CSNPs) preserves labile phytochemicals and ensures controlled release. This is the first comparative study developing CSNPs loaded with three OPE colors, optimizing parameters, and evaluating their antioxidant and antibacterial activities. TEM analysis showed spherical NPs (∼20-70nm), with good stability (ZP⁓25mV), acceptable uniformity (PDI⁓0.25), encapsulation efficiency (EE %∼70%), and loading capacity (LC%∼22% w/w of extract relative to the total experimental nanoparticle mass). The nanoformulations exhibited enhanced thermal stability and reduced crystallinity compared to their relative free extracts. FTIR analysis confirmed the entrapment of the extract within the CSNPs matrix. The i n vitro release study validated the structural stability through a controlled release profile consistent with findings of TPC and DPPH assays. The antibacterial assessment of OPE and their corresponding nanoparticles revealed significant activity against various pathogenic Gram-positive and Gram-negative strains, particularly from the green and red varieties. Overall, the formulated nanosystem represented an effective delivery platform for bioactive compounds derived from OPE byproducts.