Effect of operating conditions on size of catechin/β-cyclodextrin nanoparticles prepared by nanoprecipitation and characterization of their physicochemical properties

Nanoscale catechin/beta-cyclodextrin inclusion complex (CA/beta-CD IC) particles were prepared by nanoprecipitation method (absolute ethanol as precipitant). The effects of beta-CD concentration, ethanol amount used for precipitating and ethanol dropping rate during precipitation on size of CA/beta-CD IC particles were studied. Dynamic light scattering results indicated the above operating conditions have a significant effect on size of CA/beta-CD IC nanoparticles. Nanoparticles can be further reduced to about 90 nm by adjusting operating parameters, such as reducing beta-CD concentration, increasing amount of ethanol and decreasing ethanol drop rate. Inclusion ratio of CA/beta-CD IC nanoparticles was about 71%. Fourier transform infrared spectroscopy results indicated that intermolecular hydrogen bond interactions maintain CA in cavity of beta-CD. X-ray diffraction results showed the crystalline structure in nanoscale CA/beta-CD IC was different from that in micro-size CA/beta-CD IC. Differential scanning calorimetry and scanning electron microscopy results confirmed the formation of CA/beta-CD IC nanoparticles. CA/beta-CD IC nanoparticles displayed great storage stability and ionic strength stability, and exhibited excellent stability at pH 4-9. Release behavior of CA from CA/beta-CD IC nanoparticles was controlled. The CA/beta-CD IC nanoparticles have potential applications in nano-functional foods.