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. Author manuscript; available in PMC: 2015 May 21.
Published in final edited form as: Adv Mater. 2014 Mar 11;26(19):3003–3008. doi: 10.1002/adma.201304880

Figure 1.

Figure 1

PEG-4MAL for microencapsulation of cells and proteins in a flow-focusing microfluidic chip using a cytocompatible crosslinking reaction. (a) PEG-4MAL macromer consists of a 4-arm branched PEG backbone modified with a maleimide group terminating each arm. At physiological pH, free thiol-containing molecules undergo a Michael-type addition reaction with maleimides, forming a covalent bond to macromer. This reaction is facilitated by nucleophilic buffers such as triethanolamine (TEA), and can be used to either functionalize the macromer or crosslink macromer into a hydrogel network. (b) A microfluidic device with flow focusing geometry is utilized to produce microgels. A co-flowing oil phase shields an aqueous macromer solution, containing cells and/or proteins, from the crosslinker-containing oil phase as the macromer solution approaches the flow focusing nozzle. After droplet formation, the DTT emulsion rapidly crosslinks macromer solution into cell- or protein-laden microgels.