Radiopaque hydrogel microbeads for diagnostic imaging

Project 1: We are using droplet microfluidics to control and fabricate biocompatible alginate microgels containing uniformly distributed BaSO4 nanoparticles as an inherent imaging agent for embolization and diagnostic imaging applications. Na-alginate droplets made in the microfluidics device were dripped into a BaCl2 bath. The droplets were subsequently cross-linked by Ba2+ to form alginate microgel droplets. Simultaneously, BaSO4 nanoparticles were synthesized by the reaction of SO42- premixed in the Na-alginate solution and Ba2+ present in the collection bath. Ba-alginate microgels show a sharp X-ray image, confirming they can be used as X-ray visible embolic materials.

Project 2: Atom-economical in situ synthesis of BaSO4 as imaging contrast agents within poly(N-isopropylacrylamide) microgels using one-step droplet microfluidics: A novel in situ synthesis of BaSO4 as an X-ray imaging contrast agent within poly(N-isopropylacrylamide) (PNIPAM) microgels is accomplished by one-step droplet microfluidics with interlinking reactions. The one-step droplet microfluidics device with wavy channels is employed to produce monodispersed PNIPAM microgels (~40 μm) via free radical polymerization by the initiation of ammonium persulfate (APS) and N,N,N′,N′-tetramethylethylenediamine (TEMED) complex. The resultant PNIPAM microgels are subsequently dripped into a collecting bath containing aqueous BaCl2 solution. For the in situ synthesis of BaSO4, Ba2+ ions diffuse into the PNIPAM microgels and further react with SO42- ions released from the decomposed by-product of APS/TEMED complex during the initiation, yielding almost 100% atom efficiency of persulfate ions. This microfluidics based method provides a green and atom-economical reaction approach to synthesize functionalized microgels with uniform distribution of BaSO4 nano-crystallites. Moreover, the radiopaque BaSO4–PNIPAM microgels also possess great potentials in the fields of endovascular embolization, diagnostic imaging and visible implantation materials.

Relevant publications:

  • Q. Wang, D. Zhang, X. Yang, H. Xu, A. Q. Shen, Y. Yang, Atom-economical in situ synthesis of BaSO4  as imaging contrast agents within poly(N-isopropylacrylamide) microgels using one-step droplet  microfluidics,  Green Chemistry,  2013, 115, 222. DOI: 10.1039/c3gc40728d.
  • Q. Wang,  D. Zhang,  H. Xu,  X. Yang,  A.Q. Shen,  Y. Yang,  Microfluidic one-step fabrication  of radiopaque alginate microgels containing in-situ formed BaSO4 nanoparticles for endovascular embolization,  Lab on a Chip, 12, 4781, 2012.