Atom-economical in situ synthesis of BaSO4 as imaging contrast agents within poly(N-isopropylacrylamide) microgels using one-step droplet microfluidics

作者：Wang Qin^*; Zhang Di; Yang Xiangliang; Xu Huibi; Shen Amy Q; Yang Yajiang

来源：Green Chemistry, 2013, 15(8): 2222-2229.

DOI：10.1039/c3gc40728d

A novel in situ synthesis of BaSO4 as an X-ray imaging contrast agent within poly(N-isopropylacrylamide) (PNIPAM) microgels has been accomplished by one-step droplet microfluidics with interlinking reactions. A one-step droplet microfluidics device with wavy channels is employed to produce monodispersed PNIPAM microgels (similar to 40 mu m) via free radical polymerization by the initiation of the ammonium persulfate (APS) and N,N,N',N'-tetramethylethylenediamine (TEMED) complex. The resulting PNIPAM microgels are subsequently dripped into a collecting bath containing an aqueous BaCl2 solution. For the in situ synthesis of BaSO4, Ba2+ ions would diffuse into the PNIPAM microgels and further react with SO42- ions originated from the decomposed by-product of the APS-TEMED complex during the initiation, yielding almost 100% atom efficiency of persulfate ions. The morphologies and the composition of the PNIPAM microgels containing in situ synthesized BaSO4 (BaSO4-PNIPAM microgels) are characterized by scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM-EDX) and X-ray diffraction (XRD). These results show that 14 nm BaSO4 crystallites have been in situ synthesized in the PNIPAM microgels. The resulting BaSO4-PNIPAM microgels are also visible under X-ray radiation by an in vitro fluoroscopic evaluation. This droplet microfluidics based method provides a green and atom-economical reaction approach to synthesize functionalized microgels with a uniform distribution of BaSO4 nano-crystallites. Moreover, the radiopaque BaSO4-PNIPAM microgels also possess great potential in the fields of endovascular embolization, diagnostic imaging, and visible implantation materials.

• 出版日期2013
• 单位华中科技大学