REAL-TIME DETERMINATION OF OXYGEN AND pH IN DROPLET MICROFLUIDIC CULTURING SYSTEMS USING OPTICAL NANOSENSOR PARTICLES

Shiwen Sun, Michał Horka, Miguel Tovar, Lisa Mahler, Artur Ruszczak, Josef Ehgartner, Martin Roth, Piotr Garstecki, Torsten Mayr

Research output: Contribution to conferencePoster

Abstract

This work shows a detection tactic to achieve accurate and real-time information of oxygen concentration and pH in droplets during bacterial culturing by using biocompatible luminescent sensor nanoparticles and a lifetime-based miniaturized readout device. We adapt a simple droplet microfluidic cell culturing system from microdroplet chemostats [1] and monitor the concentration of oxygen and optical density (OD) simultaneously (Figure 2) in each droplet during incubation of Escherichia coli (Figure 4) and Mycobacterium smegmatis at time interval of 5 minutes. Different from showing relative oxygen concentration change by luminescence intensity measurement from Cao et al. [2], we are able to provide absolute concentration of oxygen in each moving droplet by accurate luminescence lifetime-based measurements. Additionally, and for the first time, we demonstrate the feasibility of monitoring pH during dynamic incubation of microfluidic droplets. While culturing Pichia pastoris in picoliter droplets collected in a microfluidic incubator [3], we measure the pH decrease in media caused by cell growth and metabolism inside the droplets. The optical oxygen and pH sensor nanoparticles provide a non-invasive powerful tool for study of cell culturing and screening in droplet microfluidic systems.
We use poly(styrene-block-vinylpyrrolidone) nanoparticles (PSPVP NPs) as a versatile platform [4], and entrap different “sensing chemistries” to obtain oxygen sensitive or pH sensitive nanoparticles (Figure 1). We develop and synthesis the near-infrared emitting dyes platinum (II) benzoporphyrins [5] and aza-BODIPY [6] for oxygen and pH sensing, respectively. The miniaturized fluorometer, in the footprint of a memory stick, is able to measure through tubing or chip material. It is further adapted for droplet measurement by equipping a lens to focus on an area about 80 μm in diameter [7]. We use signal intensity, which indicates the position of measuring, to select the signal for calculation of oxygen concentration or pH in each droplet (Figure 3).
The microdroplet cell culturing system is fabricated by customized Teflon connector and Teflon Fluorinated Ethylene Propylene (FEP) tubing (ID = 0.8 mm). For pL-droplets, incubation and pH measurements are performed in a microfluidic incubator, which is 3D printed with transparent resin.
We demonstrate that oxygen and pH sensor nanoparticles in combination with a miniaturized read-out system enable the on-line monitoring of microfluidic droplets during cell culturing. The real-time information of oxygen concentration and pH in droplets can be used by microfluidic screening systems for cell analysis or sorting. It also provides better understanding of system and mass transfer by monitoring oxygen or pH in microfluidic systems.
Original languageEnglish
Publication statusPublished - Oct 2016
EventThe 20th International Conference on Miniaturized Systems for Chemistry and Life Sciences - Dublin, Ireland
Duration: 9 Oct 201613 Oct 2016
http://www.microtas2016.org/

Conference

ConferenceThe 20th International Conference on Miniaturized Systems for Chemistry and Life Sciences
Abbreviated titleMicroTAS
Country/TerritoryIreland
CityDublin
Period9/10/1613/10/16
Internet address

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