Microfluidic synthesis of monodisperse pectin hydrogel microspheres based on in situ gelation and settling collection

BACKGROUND: Generation of monodisperse hydrogel microspheres is needed to make exquisite microenvironments, provide effective delivery system, and obtain reliable results. In this work, we present a simple microfluidic approach for the preparation of monodisperse pectin hydrogel microspheres because of efficient collection and shape of hydrogel. RESULTS: Based on the mechanism of in situ gelation and efficient collection, aqueous droplets of pectin polysaccharides are continuously generated in an immiscible continuous phase dissolving divalent metal ions, such as calcium. Under in situ gelation conditions, calcium ions are diffused into the interface between the continuous phase and the aqueous droplets, which triggers gelation of the pectin polysaccharides. The settling collection method, which involves dropping consecutive hydrogels from the outlet hole, is able to maintain the shape of the soft pectin hydrogels. Thus, pectin microspheres produced show high monodispersity (a coefficient of variation of 3.5%). In addition, the stiffness of the pectin hydrogels produced can be manipulated by a simple change of the concentration of pectin in the aqueous phase. The control of the mechanical properties can also be confirmed by measurement of the deformation of the pectin hydrogels using the micropipette aspiration method. Furthermore, the versatility of this approach enables the preparation of monodisperse pectin hydrogels with the capability to encapsulate or release nanoparticles on demand under mild conditions. The pectin microspheres are freely manipulated by the control of magnetic fields. CONCLUSION: We believe that the in situ microfluidic synthesis method combined with settling collection provides an efficient approach for the preparation of soft, monodisperse hydrogel microspheres. (C) 2016 Society of Chemical Industry