A facile preparation of rutin nanoparticles and its effects on controlled growth and morphology of calcium oxalate crystals

Switching of the growth-mode of calcium-containing crystals are of great research interest in materials science for the inhibition of pathological biomineralization. Rutin, a flavonol glycoside, was reported to have many pharmacological activities. However, the efficiency of rutin for practical therapeutic applications is still a challenge due to its low aqueous solubility and limited bioavailability. Herein, we report a facile method for preparation and characterization of rutin nanoparticles of similar to 200 nm in size and zeta potential of -22.70 +/- 2.51 mV, based on anti-solvent co-precipitation using the synergistic effect of surfactants. Morphological and structural characterization of the nanoparticles was carried out with scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and powder X-ray diffraction (XRD) patterns. These results showed that rutin nanoparticles had a smaller particle size than raw rutin, and changed into an amorphous structure from the crystal structure of raw rutin. In vitro release profiles showed a sustained release rate of hydrophilic rutin nanoparticles corresponding to 83.5 +/- 8.4% for a time period of 8 days. Furthermore, the influence of the rutin nanoparticles on the tuning of the growth and morphology of calcium oxalate (CaC2O4) crystals have been assessed using SEM, XRD patterns, TGA analysis and adsorption isotherms. The experimental results showed that the rutin nanoparticles could induce the formation of oval and octahedral calcium oxalate dihydrate (COD) crystals in a concentration-dependent manner. It is believed that the hydrogen bonding between the phenolic groups in rutin with carboxylate ions in crystals contributes to their increased adsorption and directing calcium oxalate monohydrate to dihydrate forms. These results indicated the potential application of rutin nanoparticles for in vivo lithiatic studies as well as for other pharmacological properties.