THESIS
2021
1 online resource (xv, 136 pages) : illustrations (some color)
Abstract
The oxygen partial pressure and pH are essential parameters in microenvironment that
influence the cell metabolism. Oxygen consumption due to cellular respiration is the most
common approach for energy production. In addition, dysregulated extracellular pH of cancer
cells is investigated to a large extent for clinical diagnosis or targeted therapy. In this work, we
demonstrate the feasibility of integration of optical oxygen and pH sensors into digital
microfluidic devices to perform multiple biological assays including on-chip antimicrobial
susceptibility testing and anti-cancer drug screening assays.
We fabricated and applied a digital microfluidic chip integrated with optical oxygen sensor
film to perform automated miniaturized antimicrobial susceptibility test by recording the
extra...[
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The oxygen partial pressure and pH are essential parameters in microenvironment that
influence the cell metabolism. Oxygen consumption due to cellular respiration is the most
common approach for energy production. In addition, dysregulated extracellular pH of cancer
cells is investigated to a large extent for clinical diagnosis or targeted therapy. In this work, we
demonstrate the feasibility of integration of optical oxygen and pH sensors into digital
microfluidic devices to perform multiple biological assays including on-chip antimicrobial
susceptibility testing and anti-cancer drug screening assays.
We fabricated and applied a digital microfluidic chip integrated with optical oxygen sensor
film to perform automated miniaturized antimicrobial susceptibility test by recording the
extracellular dissolved oxygen change caused by cellular respiration.
Here, the oxygen sensitive probe PtTFPP was embedded in a Hyflon AD60 polymer and
spin coated as a 100 nm thick layer onto an ITO glass serving as the DMF ground electrode. A
rapid and reliable two-fold dilution procedure was developed and performed and AST with E.
coli ATCC 25922 in the presence of ampicillin, chloramphenicol and tetracycline at different
concentrations from 0.5 to 8 μg mL
-1 were investigated. The minimum inhibitory concentration values measured from DMF chip were consistent with that from the standard broth
microdilution method but requiring only minimal sample handling and working with much
smaller sample volumes.
Lastly, extracellular pH monitoring of adherent cancer cell cultures on the DMF chip is
demonstrated. FITC was covalently linked to pHEMA and localized immobilized on a circular
exposed hydrophilic site on DMF top plate via passive dispending. The working range of the
pH sensor spot was pH 4.8 to pH 7.8 which was suitable for pH measurement in cell culture
medium.
Polydopamine was added as a cell adhesion promotor on the pH sensor surface. The
sensitivity of the pH sensor was not affected by this modification. Luminescence-based pH
sensor films can measure the acidification process of cancer cell metabolism due to the
abnormal excess glycolysis. The results showed that the extracellular pH change of cancer
cells (breast cancer MCF-7 and lung cancer A549) was significantly larger than normal cells
(HUVEC). Based on this, we further investigated the effect of glucose concentration and the
anti-cancer drug dexamethasone on cancer cell acidification. PL intensity decreasing rate
illustrated the cancer cell acidification rate increased at high glucose level. However, the rate
decreased under 0.1 μg mL
-1 dexamethasone stimulation. Here, we present the first digital
microfluidic platform integrated with optical pH sensors for probing the extracellular pH
change of cancer cells and anti-cancer drug screening.
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