Physical, structural, thermal and morphological characteristics of zeinquercetagetin composite colloidal nanoparticles

• Physical, structural, thermal and morphological characteristics of zein–quercetagetin composite colloidal nanoparticles (Z–QCCN) were investigated.
• Fluorescence quenching of zein was caused and CD intensities were changed by the binding of quercetagetin to zein.
• Z–QCCN with zein to quercetagetin mass ratio of 20:1 showed more stably thermal behaviors.
• Z–QCCN exhibited more compact structure than single zein nanoparticles.

The anti-solvent precipitation method was applied for the preparation of zein–quercetagetin composite colloidal nanoparticles with zein to quercetagetin mass ratios of 30:1, 25:1, 20:1, 15:1 and 10:1. Nephelometry analysis indicated that the turbidity of zein–quercetagetin composite colloidal nanoparticles was decreased from 68.4 to 35.6 NTU at zein to quercetagetin mass ratio of 25:1 (Z–Q25:1). The result of fourier transform infrared spectroscopy revealed that the primary interactions between zein and quercetagetin were hydrogen bonds and hydrophobic effects. Fluorescence quenching of zein was ascribed to the binding of quercetagetin to zein and the presence of quercetagetin in zein alcoholic solution resulted in changes in the circular dichroism intensities. Furthermore, differential scanning calorimetry thermograms showed that the endothermic peaks of the zein–quercetagetin composite colloidal nanoparticles were higher than that of native zein nanoparticles (ZNP, 208.15 °C), especially for Z–Q20:1 (266.82 °C). Scanning electron microscopy images exhibited that native ZNP were of nanospheres with the diameter around 100 nm and smooth surfaces and zein–quercetagetin composite colloidal nanoparticles showed more compact structure with rough edges and agglomeration was observed resulting from the close packing of nanoparticles.

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