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The objective of this research was to fabricate novel antimicrobial films based on zein colloidal nanoparticles coated with sodium caseinate (SC), an emulsifier/stabilizer. Thymol-loaded zein-SC nanoparticles were prepared using an antisolvent technique, with the average particle size and zeta potential about 200 ± 20 nm and -40 mV, respectively. Zein-SC nanoparticle-based films exhibited higher mechanical resistance and water barrier capacity than the SC films and concomitant good extensibility as compared with zein films. Thymol loadings endowed zein-SC nanoparticle-based films with antimicrobial activity against Escherichia coli and Salmonella as well as DPPH radical scavenging activity. Water vapor permeability, microstructure, mechanical, and controlled release properties of the films were evaluated. The possible relationship between some selected physical properties and microstructure were also discussed. Atomic force microscopy (AFM) analysis indicated that thymol loadings resulted in the emergence phenomena of the nanoparticles to form large particles or packed structure, consisting of clusters of nanoparticles, within the film matrix, in a thymol loading dependent manner. The appearance of large particles or an agglomerate of particles may weaken the compactness of protein network of films and thus impair the water barrier capacity, mechanical resistance, and extensibility of the films. The release kinetics of thymol from nanoparticle-based films can be described as a two-step biphasic process, that is, an initial burst effect followed by subsequent slower release, and zein-SC nanoparticles within the films matrices gave them the ability to sustain the release of thymol. In addition, a schematic illustration of the formation pathway of zein-SC nanoparticle-based films with or without thymol was proposed to illuminate the possible relationship between some selected physical properties and the microstructure of the films.

Protein–polysaccharide complexes can be created in various ways (physical mixing, enzymatic cross-linking, chemical cross-linking, and Maillard reaction), and diverse protein–polysaccharide complexes are generally grouped into non-covalent and covalent complexes. Delivery systems constructed through assembly of protein–polysaccharide complexes (DSAPC) consist of emulsion-based delivery systems, capsule-based delivery systems, molecular complexes, nanogels, core–shell particles, composite nanoparticles, and micelles. DSAPC are effective delivery vehicles in enhancing the overall efficacy of bioactive ingredients, and DSAPC may possess multiple advantages over other delivery vehicles in bioactive ingredient delivery. However, designing and applying DSAPC are still faced with some challenges, such as low loading of bioactive ingredients. Efforts are required to reconsider and improve efficiency of DSAPC in many aspects, such as controlled release and targeted delivery. On the basis of more comprehensive and deeper understandings, DSAPC can be designed more rationally for delivery of bioactive ingredients.

A dual-emitting dye@MOF composite has been synthesized by incorporating a fluorescent dye eosin Y (EY) within a UiO-type zirconium-based metal−organic framework (Zr-MOF) through a synthetic encapsulation method. The Zr-MOF prevents the aggregation of EY molecules and keeps EY molecules stably included after synthesis. As expected, an energy transfer from Zr-MOF to EY molecules occurred because of the good overlap between the emission of Zr-MOF and the absorption of EY. As a result, the obtained EY@Zr-MOF composite features a weak blue emission at 446 nm and a strong yellow emission at 553 nm. By using the relative height of the two emission peaks replacing absolute peak height as detecting signals, EY@Zr-MOF composite acts as a self-calibrating luminescent sensor for selectively detecting Fe 3+ , Cr 2 O 7 2− , and 2-nitrophenol. Furthermore, the observed fluorescence responses of the composite toward analyte are highly stable and reversible after recycling experiments. To the best of our knowledge, this is the first example of a dye@MOF-implicated self-calibrating sensor for Fe 3+ , Cr 2 O 7 2− , and 2-nitrophenol detection.

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A series of eosin Y (EY)-embedded zirconium-based metal−organic frameworks (Zr-MOFs) were prepared by utilizing the synthetic encapsulating method. By virtue of effective resonant energy transfer between Zr-MOF and EY, not only does EY@Zr-MOF exhibit dual-emissive characteristics, but also the relative intensity of their double emission is greatly tuned with increasing EY loading quantity. As a consequence, the double emission of EY@Zr-MOF presented large distinctions in location and intensity. By using the relative fluorescence intensity instead of the absolute fluorescence intensity of emission peaks as detection signals, two EY@Zr-MOFs served as built-in self-calibrated fluorescence sensors to detect pesticides, where EY@Zr-MOF realized the selective detection of nitenpyram, a kind of nicotine pesticide. These results indicate that the integration of robust Zr-MOF and fluorescence molecules provides a new research platform for pesticide sensing and recognition.