One-step preparation of multifunctional alginate microspheres loaded with in situ-formed gold nanostars as a photothermal agent
This work is to develop a kind of multifunctional embolic material, which will possess a synergized tumor ablation effect combining transcatheter arterial chemoembolization and hyperthermia therapy. Herein, monodispersed calcium alginate (CA) microspheres containing gold nanostars (Au NSs) have been prepared in one step by using a droplet-based microfluidic technique. The droplets containing sodium alginate (SA) and HAuCl4 formed in the microfluidic device are solidified by Ca2+ to obtain CA microspheres while HAuCl4 is successively reduced to Au(0) by SA and vitamin C in the collecting solution to produce Au NSs in situ-encapsulated in CA microspheres. Herein, alginate acts as a co-reducing agent and stabilizer for in situ-formed Au NSs, and also as a drug carrier and embolic agent. Studies of scanning electronic microscopy combined with energy-dispersive X-ray spectroscopy, transmission electronic microscopy and X-ray diffraction verified the existence and morphology of the in situ-formed Au NSs. The as-prepared microspheres can absorb near-infrared (NIR) light and the temperature increment of the microsphere suspension can be more than 60 °C under NIR irradiation due to the presence of Au NSs. The drug release rate can be accelerated by NIR irradiation. The study of in vitro cytotoxicity indicates that tumor cells can be efficiently killed by the combination of chemotherapy and NIR-induced hyperthermia. As potential embolic materials, the hybrid microspheres provide new insights into synergistic therapy of cancer.