Introduction
Droplet generation is a powerful technique for biomedical researchers to obtain high-throughput and low-cost analyses, [1]. Using microfluidic approaches, scientists have improved cell and protein encapsulation methods. Advances in these techniques bring promising results in the treatment of various diseases. This article will talk about droplet generation applied to cell and protein encapsulation. We'll also show you everything you need to get the most out of your experiments.
Droplet-based microfluidics
Droplet-based microfluidics is a method by which tiny droplets are created by introducing two immiscible fluids into a microfluidic channel. Usually, researchers control droplet size by manipulating the channel´s geometry and adjusting the continuous/dispersed phase flow rate, [2].
Microscale droplets have faster mixing and heat transfer, speeding up reaction times. These isolated chambers act like microreactors. Besides, they offer a physically and chemically isolated environment to avoid cross-contamination among cells, allowing single-cell encapsulation, culture, and analysis, [2].
The technique provides multiple advantages such as:
Enable whole-cell screening workflow design
Low reagent consumption
Biological compatibility
High sensitivity
Droplet encapsulation includes numerous techniques. The method differs depending on the type and number of samples and desired time and order of chemical reactions. Mainly, it involves diluting the sample into the droplet´s dispersed phase.
Protein encapsulation
Protein encapsulation in microspheres is a promising therapeutic strategy in various diseases treatment, [1]. Protein therapeutics are extremely sensitive to enzymatic degradation. Thus, encapsulating them in a carrier can provide protection while they are delivered to the target site in the body, [3].
Two common strategies to obtain protein nanoparticles are nanoprecipitation and emulsification. Another way is emulsification, followed by solvent depletion and solvent diffusion. Microfluidic platforms can make the process more efficient and provide more controlled drug release rates, [3].
The technique allows researchers to customize encapsulated protein release rates according to diffusion through the hydrogel network or microgel hydrolytic/enzymatic degradation, [1].
Single-Cell Encapsulation in Droplets
Cell microencapsulation typically uses alginate. However, this material provides limited control of the cellular microenvironment. A microfluidic approach for generating size-controlled synthetic microgels could help solve this issue. This technique provides precise droplet size control and can be used to make microgels with membranes as thin as 6 µm, [1].
Scientists can encapsulate cells from human patients and cultured cell lines in droplets at high-throughput rates using microfluidics. Particularly, droplet-based single-cell techniques can be beneficial since they allow researchers to manipulate single cells within isolated microenvironments, [2].
Typically, droplets contain a solution of water and cells. However, researchers use biocompatible hydrogel or other polymers to keep long-term cell culture. Notably, cells encapsulated in hydrogel droplets can survive for a week. Moreover, droplet-microfluidic platforms can couple with various analytical approaches, including fluorescence, mass spectrometry, and electrochemistry, [2].
Examples of applications
Therapeutic proteins delivery
Locally-implanted microgels may represent a minimally invasive manner of delivering therapeutic proteins such as growth factors and cytokines. It could also allow mosaic injections containing several microgels to provide complex release profiles or multi-protein delivery, [1].
Transplants
Cell encapsulation in microgels can be helpful in transplants. Researchers can control microgels size to mitigate the immune infiltration of transplanted cells while keeping oxygen and waste products transported. This could help reduce immunosuppression after transplantation, [1].
Microgels can also immobilize cells at the desired transplant size, essential since many cell therapies rely on systemic cell administration, [1].
Synthetic microgels also allow manipulation of encapsulated stem cells’ microenvironment, influencing differentiation and secretory function, [1].
High-throughput screening
Screening is helpful in drug discovery, toxicity, and antibody affinity analyses. It aims to evaluate several compounds in a short time frame. Droplet encapsulation can improve high-throughput screening outcomes since the highly monodisperse droplets provide homogeneous reaction conditions.
What do you need to get started?
Droplet microfluidics techniques provide cost-effective and high-throughput analysis. The minimum setup to start your experiments with droplet generation is :
2-3 x Microfluidic pumps (or 2-3 channels on one pump such as the 4U pump) – to control the flow of the continuous (oil) phase and dispersed (water) phase. Depending on the application, we recommend the 4U pressure pump or 2x ExiGo microfluidic syringe pumps. 4U pressure pump has a stable and accurate flow rate and enables independent control of 4 different channels, controlling both pressure and flow. You can program your flow profile and efficiently manage all the pump features using your smartphone.
2 x Flow sensors to provide feedback of the flow control of both oil and water phases.
Microfluidic Chip with appropriate geometry creates droplets to ensure droplet size is optimal.
Stable Channel Surface Chemistry to ensure droplet stability.
Surfactant stabilizes the interface between the oil and water phase, giving stability to the droplets.
Oil for continuous phase to improve droplet stability. Tubing to connect from your pumps to the microfluidic chip
Cellix can supply the complete kit or just the components you wish. To learn more about our products, contact Cellix or simply request a quote now.
References
1. Headen, D., García, J. & García, A. Parallel droplet microfluidics for high throughput cell encapsulation and synthetic microgel generation. Microsyst Nanoeng 4, 17076 (2018). https://doi.org/10.1038/micronano.2017.76
3. Meng, Hu, et al. "The role of microfluidics in protein formulations with pre-programmed functional characteristics." Biologics: targets & therapy 12 (2018): 191.