Simultaneous Determination of Oxygen and pH Inside Microfluidic Devices Using Core-Shell Nanosensors.
A powerful online analysis setup for the simultaneous detection of oxygen and pH is presented. It features core-shell nanosensors, which enable contactless and inexpensive read-out using adapted oxygen meters via modified dual lifetime referencing in the frequency domain (phase shift measurements). Lipophilic indicator dyes were incorporated into core-shell structured poly(styrene-block-vinylpyrrolidone) nanoparticles (average diameter = 180 nm) yielding oxygen nanosensors and pH nanosensors by applying different preparation protocols. The oxygen indicator platinum(II) meso-tetra(4-fluorophenyl) tetrabenzoporphyrin (PtTPTBPF) was entrapped into the polystyrene core (oxygen nanosensors) and a pH sensitive BF2-chelated tetraarylazadipyrromethene dye (aza-BODIPY) was incorporated into the polyvinylpyrrolidone shell (pH nanosensors). The brightness of the pH nanoparticles was increased by more than 3 times using a light harvesting system. The nanosensors have several advantages such as being excitable with red light, emitting in the near-infrared spectral region, showing a high stability in aqueous media even at high particle concentrations, high ionic strength, or high protein concentrations and are spectrally compatible with the used read-out device. The resolution for oxygen of the setup is 0.5-2.0 hPa (approximately 0.02-0.08 mg/L of dissolved oxygen) at low oxygen concentrations (<50 hPa) and 4-8 hPa (approximately 0.16-0.32 mg/L of dissolved oxygen) at ambient air oxygen concentrations (approximately 200 hPa at 980 mbar air pressure) at room temperature. The pH resolution is 0.03-0.1 pH units within the dynamic range (apparent pKa7.23 ± 1.0) of the nanosensors. The sensors were used for online monitoring of pH changes during the enzymatic transformation of Penicillin G to 6-aminopenicillanic acid catalyzed by Penicillin G acylase in miniaturized stirred batch reactors or continuous flow microreactors.
Institute of Analytical Chemistry and Food Chemistry, Graz University of Technology, NAWI Graz , Stremayrgasse 9/3, 8010 Graz, Austria.
Josef
J
Ehgartner
Institute of Analytical Chemistry and Food Chemistry, Graz University of Technology, NAWI Graz , Stremayrgasse 9/3, 8010 Graz, Austria.
Martin
M
Strobl
Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, NAWI Graz , Petersgasse 12/1, 8010 Graz, Austria.
Juan M
JM
Bolivar
Institute of Analytical Chemistry and Food Chemistry, Graz University of Technology, NAWI Graz , Stremayrgasse 9/3, 8010 Graz, Austria.
Dominik
D
Rabl
Institute of Applied Synthetic Chemistry, Vienna University of Technology , Getreidemarkt 9/163, 1060 Wien, Austria.
Mario
M
Rothbauer
Institute of Applied Synthetic Chemistry, Vienna University of Technology , Getreidemarkt 9/163, 1060 Wien, Austria.
Peter
P
Ertl
Institute of Analytical Chemistry and Food Chemistry, Graz University of Technology, NAWI Graz , Stremayrgasse 9/3, 8010 Graz, Austria.
Sergey M
SM
Borisov
Institute of Analytical Chemistry and Food Chemistry, Graz University of Technology, NAWI Graz , Stremayrgasse 9/3, 8010 Graz, Austria.
Torsten
T
Mayr