Comparative evaluation of zein and gliadin as encapsulant materials for antimicrobial delivery: A thermokinetic study

In this study, two food prolamins, zein and gliadin, were used to encapsulate roxithromycin (ROX) as a model antimicrobial. The physical characteristics of both nanoparticles were analyzed, and the inhibition of Staphylococcus aureus by both free and encapsulated ROX was first evaluated using broth dilution growth curves and microcalorimetry analysis.

Analysis of the physical characteristics of the nanoparticles revealed that the gliadin-ROX exhibits greater stability and higher encapsulation efficiency (EE) than zein-ROX. Notably, the freeze-dried gliadin-ROX dispersed well, whereas zein-ROX did not. The scanning electron microscopy (SEM) observations also confirmed that the size of the gliadin-ROX was slightly large. As evidenced by traditional drug susceptibility tests, the gliadin-ROX notably exhibited superior antibacterial efficacy in both micro-broth and macro-broth dilution assays. While the optical density (OD)-based growth curves did not show significant differences, the thermokinetic parameters obtained from microcalorimetry clearly demonstrated that gliadin-ROX was more effective than both free ROX and zein-ROX, evidenced by a much lower half-maximal inhibitory concentration (IC₅₀) and total heat generated over 24 h (Q_24h). Similarly, the SEM cell morphology analysis confirmed that gliadin-ROX has superior antibacterial properties.

This method provides more quantitative information and may offer an alternative approach for evaluating nano-delivery systems for antimicrobials. © 2026 Society of Chemical Industry.