Luminescence Lifetime Imaging of Oxygen, pH, and Carbon Dioxide Distribution Using Optical Sensors

Abstract

We present a modular system for time-resolved two-dimensional luminescence lifetime imaging of planar optical chemical sensors. It is based on a fast, gateable charge-coupled device (CCD) camera without image intensifier and a pulsable light-emitting diode (LED) array as a light source. Software was developed for data acquisition with a maximum of parameter variability and for background suppression. This approach allows the operation of the system even under daylight. Optical sensors showing analyte-specific changes of their luminescence decay time were tested and used for sensing pO2, pCO2, pH, and temperature. The luminophores employed are either platinum(II)-porphyrins or ruthenium(II)-polypyridyl complexes, contained in polymer films, and can be efficiently excited by blue LEDs. The decay times of the sensor films vary from 70 μs for the Pt(II)-porphyrins to several 100 ns for the Ru(II) complexes. In a typical application, 7 mm-diameter spots of the respective optical sensor films were placed at the bottom of the wells of microtiterplates. Thus, every well represents a separate calibration chamber with an integrated sensor element. Both luminescence intensity-based and time-resolved images of the sensor spots were evaluated and compared. The combination of optical sensor technology with time-resolved imaging allows a determination of the distribution of chemical or physical parameters in heterogeneous systems and is therefore a powerful tool for screening and mapping applications.

Effects of light fractionation and different fluence rates on photodynamic therapy with 5-aminolaevulinic acid in vivo

“…The technique of measuring the tissue pO 2 by luminescence lifetime imaging using planar oxygen sensors allows a spatially highly resolved and time-resolved mapping of two-dimensional pO 2 -distribution within the entire chamber tissue in a noninvasive way (Liebsch et al, 2000(Liebsch et al, , 2001. Thus, two independent parameters to assess PDT efficacy were determined: the tissue pO 2 can be considered as a short-term parameter (up to 24 h after PDT), whereas the tumour growth curves represent the long-term parameter (up to 28 days after PDT).…”

“…The pO 2 -measurement was performed using luminescence lifetime imaging of a luminescent oxygen indicator, which is immobilised in an oxygen permeable sensor foil (for details see, Liebsch et al, 2000Liebsch et al, , 2001. The indicator is capable of translating the respective oxygen partial pressure into a light signal.…”

“…The sensor luminescence was optically filtered with a long-pass filter (RG630, Fa. Schott, Mainz, Germany) and detected via rapid lifetime determination (RLD) (for details see, Liebsch et al, 2000Liebsch et al, , 2001.…”

“…The technique of measuring the tissue pO 2 by planar optical sensors and luminescence lifetime imaging (Liebsch et al, 2000(Liebsch et al, , 2001) allows a spatially highly resolved mapping of two-dimensional pO 2 -distribution within the chamber tissue in a noninvasive way. In addition, the pO 2 -measurements were then correlated with tumour growth after PDT with the respective dosimetric protocol.…”

Oxygen and temperature sensitivity of blue to green to yellow light-emitting Pt(ii) complexes

“…The whole imaging process has been described in previous works. 40 The luminescence lifetime (τ) can be estimated according to eqn (1). 41…”