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

Abstract

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.

Microfluidic on-chip production of microgels using combined geometries

“…This increased force could reduce the time that the aqueous phase spent in droplet formation loci and resulted in the formation of smaller droplets. This observation contrasts with those researches in which just a dispersed phase flows before droplet generation locus 26 – 28 .…”

Lipid Membrane Effect on the Elasticity of Gelatin Microgel Prepared inside Lipid Microdroplets

“…In the case of the convex side, the linear relationship was satisfied for a small deformation region (Fig. 2a, ΔL < 7 µm), similar to spherical microgels in previous reports 8,10,12,13) . However, the negative curvature of the concave surface probably derived a deviation from the linear relationship.…”

“…With a decrease in the temperature, the gelatin/PEG solution inside the PC droplet proceeds with phase separation, and the partially wet gelatin-rich phase on the PC membrane turns into a concave microgel. By using micropipette aspiration 8,10,12,13) , we measured the local elasticities for the convex and concave sides, where the surfaces were in contact and not in contact with the membrane, respectively. Experimental results show that the elasticities of both surfaces are much higher than that of the bulk gels, which strongly suggests that micrometric confinement of gelatin is more dominant than microgels contact with the lipid membrane.…”

Microfluidic preparation of monodisperse polymeric microspheres coated with silica nanoparticles

“…Ca is controlled by manipulating Q c , the flow rate of the continuous phase, leading to a variation in U based on the relationship U = Q c /A, where A is the area of cross-section of the microfluidic channel. In general, a phase diagram indicating different flow patterns observed as a function of the experimental factors is an important information for understanding droplet formation 46 , 47 . As shown in Fig.…”