Erkki Soini, Professor Emeritus
Department of Medical Biophysics
Laboratory of Biophysics
Institute of Biomedicine
University of Turku
PO Box 123, FI-20521 Turku
Phone: +358-2-333-7375
Fax: +358-2-333-7060
Graduate students:

TPX-technology offers many advantages if compared with the conventional methods:
- single step assay, separation free
- high sensitivity, positive signal response
- high dynamic range
- sensitivity is independent on the volume, small sample and reagent volumes
- allows on-line monitoring of the reaction kinetics
- simultaneous monitoring of multiple parameters in same reaction volume
- compact and inexpensive instrumentation
- improves the laboratory cost-efficiency considerably

The fully automated TPX-system will be much simpler, smaller and less expensive than the conventional automatic systems today, because no separation step or such functions are needed. The multiparametricity means, that there is no need to load in reagents for several different assays separately and there is no need for dedicated dispensing means. Conventional test kits with coated tubes are not needed either. The waste of material and especially packaging material waste is reduced. The compact size and lower unit price support the idea of purchasing a separate unit for each assay panel.

We expect that with further development of laser and dye technology we are able to detect with TPX-technology even single molecule complexes such as e.g. complexes of antibody and antigen as well as their formation and reaction kinetics directly in the solution without any solid phase. This so called "molecule counting" technology is based on fluorescence correlation spectroscopy and it has many research and routine applications. Similar techniques are currently being developed also for HTS (high throughput screening) in the field of drug discovery. In addition we expect remarkable progress in rare event detection by using two-photon fluorescence excitation, e.g. in separation of foetal cells from maternal blood circulation for prenatal diagnostics.

Metalloporphyrins in time-resolved fluorometry for bioaffinity assays. We have developed new fluorescent labelling reagents and related instrument technology for use in bioaffinity assays. These labelling reagents are based on monofunctional metalloporphyrins. These labelling reagents have a long fluorescence decay time and they provide very high detection sensitivity with time-resolved fluorometry. Metalloporphyrins can be used as labelling reagents in separation assays as well as in homogenous assays.

Two monofunctional metalloporphyrins have been developed: monofunctional Pt-porphyrin and monofunctional Pd-porphyrin. The fluorescence (phosphorescence) decay times of these labelling reagents are 100 microseconds and 1000 microseconds, respectively. These labelling reagents have been produced with several different functional linker that allow easy conjugation with biomolecules. The work for developing homogenous variant for HTS-applications continues.