Continuous generation of hydrogel beads and encapsulation of biological materials using a microfluidic droplet-merging channel

Abstract

In this paper, we describe a method for encapsulation of biomaterials in hydrogel beads using a microfluidic droplet-merging channel. We devised a double T-junction in a microfluidic channel for alternate injection of aqueous fluids inside a droplet unit carried within immiscible oil. With this device, hydrogel beads with diameter\100 lm are produced, and various solutions containing cells, proteins and reagents for gelation could merge with the gel droplets with high efficiency in the broad range of flow rates. Mixing of reagents and reactions inside the hydrogel beads are continuously observed in a microchannel through a microscope. By enabling serial injection of each liquid with the dispersed gel droplets after they are produced from the oil-focusing channel, the device simplifies the sample preparation process, and gelbead fabrication can be coupled with further assay continuously in a single channel. Instantaneous reactions of enzyme inside hydrogel and in-situ formation of cell-containing beads with high viability are demonstrated in this report.

Basic Technologies for Droplet Microfluidics

“…Other advantages of droplet-based [76] microfluidic system include precisely controllable reaction time inside a droplet by adjusting the length of channel and the flow rates of fluids. The availability of a wide range of technologies for flexible generation and manipulation of droplets has enabled the applications of droplet microfluidics in a wide variety of fields, from chemical reactions [9,79] and protein crystallization [10,11] to material synthesis [12,13,[80][81][82][83], single cell analysis [84][85][86][87][88][89][90][91], DNA amplification [16], protein engineering [62,92], and high-throughput screening technologies [17,93]. It is not possible to cover all application areas in this review.…”

“…The size of the particles could be tuned by simply controlling the flow rates of the disperse phase and continuous phase. This approach has been adopted to fabricate microparticles of gels [80,81], polymers [13,82,83], and inorganic materials with designed physical and chemical properties.…”

Microfluidic formulation of pectin microbeads for encapsulation and controlled release of nanoparticles

“…The ability to form monodisperse segments of liquids can be successfully utilized to formulate monodisperse polymeric particles 7 of various-and easy to control-morphologies 8,9 and capsules. 10 Extensions of these techniques are used to encapsulate biomaterials, 11 prepare microbubble contrast agents for ultrasound radiography, 12 carriers of active substances for targeted drug delivery, 13 and for control of the temporal profile of their release. 14 Microfluidics offers extensive and unique control over the distribution of volumes of particles and over the process of their gelation.…”

“…The separation of cells from the host tissue enhances the efficacy and viability of transplanted cells. 18 Likewise, they are used to encapsulate microorganisms ͑e.g., yeast 19 for the fermentation processes͒ or active substances like drugs, 14,20 enzymes, 11 or even blood proteins. 21 As opposed to traditional, physicochemical methods of encapsulation, also here microfluidics comes in with a unique advantage of the possibility to encapsulate virtually any material in any matrix via the hydrodynamic control of the process of formation of particles.…”

Microbridge structures for uniform interval control of flowing droplets in microfluidic networks

“…2 In addition, microdroplets have great potential applications for high-throughput biochemical synthesis 3 and screening 4 based on the accurate droplet fusion and mixing controls. Possible cross-contamination between droplets can be eliminated by precise control in time and space, 5 resulting in perfect compartmentalized vessels to reduce experimental errors.…”