Tuning Chitosan Particle Architecture and Function by Adding Cinnamaldehyde Before or After Assembly

ABSTRACT Chitosan (CS) is a promising natural polymer for fabricating functional particles, but its high hydrophilicity and limited bioactivity restrict its applications. Here, we engineered CS‐based composite particles by strategically controlling the addition sequence of cinnamaldehyde (CA), a bioactive crosslinker, relative to pH‐induced self‐assembly. Adding CA before assembly (CA/CS composite particles) led to its encapsulation within the particle core, producing smaller particles (689.9 ± 70.9 nm) with enhanced thermal stability and potent antibacterial activity (17.33 ± 0.58 mm inhibition zone against E. coli ). Conversely, adding CA after assembly (CS/CA composite particles) resulted in surface‐localized CA, yielding higher particle hydrophobicity (70.24 ± 0.88° contact angle) and superior performance as Pickering emulsion stabilizers, as evidenced by smaller emulsion droplets (31.61 ± 1.50 µm) and reduced creaming (7.06 ± 0.57% index). This study demonstrates that the spatial distribution of CA, dictated solely by its addition sequence, governs particle functionality. The CA/CS composite particles are optimal for sustained antibacterial applications, while the CS/CA composite particles are better suited for stabilizing emulsions. This sequence‐dependent strategy provides a versatile platform for tailoring CS‐based composites. A key limitation of this work is the lack of quantified CA release profiles, which will be the focus of future studies to assess bioavailability in food or pharmaceutical matrices.