Tunable and Contamination-Free Injection with Microfluidics by Stepinjection
- 21 September 2021
- journal article
- research article
- Published by American Chemical Society (ACS) in Analytical Chemistry
- Vol. 93 (39), 13112-13117
- https://doi.org/10.1021/acs.analchem.1c02721
Abstract
Droplet microfluidics with picoinjection provides significant advantages to multistep reactions and screenings. The T-junction design for picoinjection is convenient in adding picoliter reagents into passing droplets to initiate reactions. However, conventional picoinjectors face difficulties in eliminating cross-contamination between droplets, preventing them from widespread use in sensitive biological and molecular assays. Here, we introduce stepinjection, which uses a T-junction with a stepped channel design to elevate the diffusional buffer zone into the main channel and consequently increases the pressure difference between droplets and the inlet of the injection channel. To demonstrate the stepinjector’s ability to perform contamination-sensitive enzymatic assays, we inject casein fluorescein isothiocyanate (FITC-casein) into a mixture of savinase and savinase-free (labeled with a red fluorescent dye) droplets. We observe no cross-contamination using stepinjection but find a severe cross-talk using an optimal picoinjection design. We envision that the simple, tunable, and reliable stepinjector can be easily integrated in various droplet processing devices, and facilitate various biomedical and biochemical applications including multiplex digital PCR, single-cell sequencing, and enzymatic screening.Keywords
Funding Information
- Ministry of Science and Technology of the People's Republic of China (2016YFE0205800, 2018YFC0310703)
- National Natural Science Foundation of China (11832017, 12072350, 21822408, 31470221)
- Chinese Academy of Sciences (QYZDB-SSW-JSC036, QYZDB-SSW-SMC008, XDB22040403)
- International Ocean Resource Survey and Exploration (DY135-B-02)
- Center for Ocean Mega-Science, Chinese Academy of Sciences (KEXUE2019GZ05)
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