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Abstracts Poster – Part III: Probes, Labels and Sensors
PRLS-44
Optochemical oxygen sensing using Pt(II)-porphyrin dye immobilised on
S-layer matrices
Sylvia Scheicher 1 , Stefan Köstler 1,3 , Birgit Kainz 2 , Christian Konrad 3 , Michael Suppan 3 ,
Alessandro Bizzari 3 , Dietmar Pum 2 and Volker Ribitsch 1,3
1) Karl Franzens University Graz, Institute of Physical Chemistry, A-8010 (Austria).
2) University of Natural Resources and Applied Life Sciences, Centre of Nanobiotechnology,
A-1180 Wien (Austria)
3) Joanneum Research, Institute of Chemical Process Development and Control, A-8010 Graz (Austria)
Crystalline bacterial surface layers (S-layers) appeared to be perfect matrices for immobilizing functional
molecules in a highly ordered structure. S-layers are monomolecular arrays of a single type of protein and
exhibit different types of lattice symmetry depending on the protein structure. The capability of S-layer
proteins to reassemble in suspension, on solid surfaces and liquid films makes them an ideal substrate for
immobilising (macro) molecules. [1-2] The protein SbpA, used in this study, forms an S-layer lattice of
square symmetry with a center-to-center spacing of 13.1 nm. Each morphological unit is composed of four
identical subunits.
Pt(II) complexes of porphyrins show strong phosphorescence at room temperature with decay times in the
range of several tens of µs. The excited triplet states of these dyes can be quenched by molecular oxygen.
This leads to a marked decrease of luminescence lifetime and intensity and can be exploited for optical
oxygen sensing. [3-4]
S-layer protein SbpA was recrystallised onto glass substrates. The free carboxylic groups of the protein
were used to covalently bind the sensitive dye via the formation of active ester intermediates. 5,10,15,20-
Tetrakis-(4-aminophenyl)-porphyrin-Pt-(II) was subsequently immobilized to the protein layer.
The sensor slides were mounted in a flowthrough-cell,
and used for dissolved oxygen
sensing in water. A LED with an emission
maximum at 405 nm was used as excitation light
source. Signal detection was accomplished using
a photomultiplier tube and LockIn Amplifier.
Modulation of the excitation light and analysis of
the resulting phase shift allowed for lifetime
based oxygen sensing. Analysis of luminescence
intensity and phase signals showed clear and
reversible dependence on oxygen concentration.
References: [1] U.B. Sleytr, et al., Ang Chem Int Ed 38 (1999) 103. [2] T.J. Beveridge, Curr Op Struct Bio 4 (1994)
204. [3] D.B. Papkovsky, T.C. O´Riordan, Journal of Fluorescence, 15 (2005) 569. [4] D.B. Papkovsky et al., Anal.
Chem. 67 (1995) 4112.
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