TIME-RESOLVED PHOTOLUMINESCENCE SUPPRESSED RAMAN SPECTROSCOPY OF DRUGS

Transcription

1 TIME-RESOLVED PHOTOLUMINESCENCE SUPPRESSED RAMAN SPECTROSCOPY OF DRUGS Tatu Rojalin Division of Pharmaceutical Biosciences, Center for Drug Research (CDR)

2 OUTLINE Background Aims Methods Results Conclusions Acknowledgements

3 BACKGROUND In Raman spectroscopy, laser excitation energy is used to change the vibrational states of sample molecules Accurate and detailed structural information on the sample molecule The utilization of Raman spectroscopy is increasing in pharmaceutical research and development

4 BENEFITS OF RAMAN SPECTROSCOPY Label-free & minimal sample preparation Measurements through container walls Qualitative & quantitative analysis Relatively insensitive to water Suitable for solutions and biological samples

5 Weak phenomenon; every ~ photon is Raman scattered Low concentrations can cause detection problems Solution; signal enhancement techniques e.g. SERS Photoluminescence(PL) -related problems? DRAWBACKS OF RAMAN SPECTROSCOPY

6 PHOTOLUMINESCENCE REJECTION The exploitation of the time difference between the Raman scattering and the photoluminescence phenomena Our solution Pulsed picosecond laser + a new detection system The new detection system involves a time-gated complementary metal oxide semiconductor (CMOS) single photon avalanche detector (SPAD)

7 AIMS Study the time-resolved technique to obtain photoluminescence suppressed Raman spectra for the model drugs Utilize raw data without data manipulation (i.e. suitability to in situ real-time observations, e.g. PAT)

8 METHODS Studied molecules Caffeine; also as a reference molecule, no PL Ranitidine hydrochloride; PL background Indomethacin (crystalline); PL background Indomethacin (amorphous); huge PL background Setups of Conventional and ps Raman spectrometers 785 nm CW laser & CCD detector 532 nm pulsed picosecond laser & CMOS-SPAD detector (the setup built at VTT, Oulu and at Tampere University of Technology, Finland)

9 THE TIME-RESOLVED SETUP Time-resolved Raman setup has programmable delaytimes Four time windows (gates)

10 THE STUDIED COMPOUNDS

11 RESULTS

12 NON-TIME RESOLVED RAMAN SPECTRA A B C D A: Caffeine B: Ranitidine hydrochloride C: Indomethacin (crystalline) D: Indomethacin (amorphous)

13 CAFFEINE

14 RANITIDINE HCL

15 INDOMETHACIN (CRYSTALLINE)

16 INDOMETHACIN (AMORPHOUS)

17 TIME-DOMAIN ASSAYS Perspectives on the capabilities of the time- domain assays Discussion on the variation of apparent photoluminescence decay times Investigation of amorphous and crystalline compounds utilizing the time-domain

18 PHOTOLUMINESCENCE DECAY Indomethacin (amorphous) - Single exponential fittings on the tail parts of the response functions - Average PL decay time calculated

19 PHOTOLUMINESCENCE DECAY Caffeine Indomethacin (crystalline) COMPOUND DECAY TIME (ns) Caffeine ~ 1.4 Indomethacin (crystalline) ~ 2.1 Indomethacin (amorphous) ~ 2.3

20 FUTURE OUTLOOK Photoluminescence decay studies on several different molecules; non-photoluminescent and photoluminescent, crystalline and amorphous Investigation of crystalline and amorphous compounds utilizing the time-domain; an established method that seems to be able to isolate the pure Raman peaks from spectra Measurements with biological (e.g. in vitro cells) samples

21 CONCLUSIONS The CMOS-SPAD-setup is a convenient tool to overcome current photoluminescence-related limitations of Raman spectroscopy for laboratory and off-laboratory use in the pharmaceutical setting Estimates on the samples overall photoluminescence decay times can be made A method to find pure Raman peaks and investigate fast Raman phenomena MAY have been established Potential to biopharmaceutical and biological applications

22 Supervisors: Prof. Marjo Yliperttula Dr. Tapani Viitala Dr. Timo Laaksonen Dr. Clare Strachan ACKNOWLEDGEMENTS Collaborators: TimeGate Instruments, Oulu, Finland: Mari Tenhunen Lauri Kurki VTT, Oulu, Finland: Jussi Tenhunen University of Oulu, Finland: Juha Kostamovaara SJT Consulting Ky, Espoo, Finland: Sauli Törmälä Technical University of Tampere, Finland: Prof. Mircea Guina Funding: Tekes -The Finnish Funding Agency for Technology and Innovation SJT Consulting Ky, Espoo, Finland THANK YOU FOR YOUR ATTENTION!