System and method for confocal raman-spectroscopic measurements of biological samples

1. System ( 1 ) for confocal Raman-spectroscopic measurements, comprising at least the following components:

a sample chamber ( 10 ), wherein said sample chamber ( 10 ) is configured to house a sample ( 2 ) in a closed chamber volume ( 12 ) of the sample chamber ( 10 ), wherein the sample chamber ( 10 ) comprises a ceiling portion ( 11 ), wherein the ceiling portion ( 11 ) is comprised in a lid ( 13 ) of the sample chamber ( 10 ), wherein said lid ( 13 ) can be opened and closed such that the chamber volume ( 12 ) comprised by the sample chamber ( 10 ) can be opened or closed, wherein the sample chamber ( 10 ) is further configured to keep a gas volume inside the chamber volume ( 12 ) separated from the atmosphere outside of the sample chamber ( 10 ), when the lid ( 13 ) is closed,

an excitation light source ( 3 ),

an objective lens ( 4 ), configured to focus excitation light ( 32 ) of the excitation light source ( 3 ) through the ceiling portion ( 11 ) of the sample chamber ( 10 ) in a focal volume ( 31 ) in the chamber volume ( 12 ) and to collect inelastically scattered light ( 33 ) stemming from the focal volume ( 31 ), wherein the objective lens comprises a numerical aperture of at least 0.55,

a confocal detection arrangement ( 20 ), comprising a confocal pinhole ( 23 ) or an optical fibre configured and arranged as a confocal pinhole ( 23 ) for confocal detection ( 22 , 23 ) of a Raman signal comprised in the inelastically scattered light ( 33 ) from the focal volume ( 31 ), and a detector ( 21 ) that is configured to detect and to record said Raman signal,

wherein the objective lens focuses the excitation light through the ceiling portion and the distance ( 5 ) between the ceiling portion ( 11 ) of the sample chamber ( 10 ) and the focal volume ( 31 ) is greater than three millimeters during operation of the system ( 1 ).

2. System according to claim 1 , characterized in that the distance ( 5 ) between the ceiling portion ( 11 ) of the sample chamber ( 10 ) and the focal volume ( 31 ) is greater than 9 mm during operation of the system ( 1 ).

3. System according to claim 1 , wherein the system ( 1 ) is configured to measure Raman signals of biological specimens ( 2 ).

4. System according to claim 1 , characterized in that the sample chamber ( 10 ) comprises air or other gas between the ceiling portion ( 11 ) of the sample chamber ( 10 ) and the focal volume ( 31 ) during operation.

5. System according to claim 1 , wherein the ceiling portion ( 11 ) of the sample chamber ( 10 ) has a thickness of more than 0.5 mm.

6. System according to claim 1 , wherein the ceiling portion ( 11 ) of the sample chamber ( 10 ) comprises portions of different optical path lengths and/or wherein the ceiling portion ( 11 ) of the sample chamber ( 10 ) comprises portions of different optical transparency, wherein the optical path lengths and/or the optical transparency of the said portions varies within 10% of a mean optical path lengths value and/or mean transparency value.

7. System according to claim 1 , wherein at least the ceiling portion ( 11 ) of the sample chamber ( 10 ) comprises a transparent material.

8. System according to claim 1 , characterized in that the system ( 1 ) comprises a scanning unit ( 6 ) that is configured to scan the focal volume ( 31 ) to different positions, over an area or through a volume within the sample chamber ( 10 ).

9. System according to claim 1 , wherein the sample chamber ( 10 ) is a Petri dish or a contact plate with a lid ( 13 ) comprising the ceiling portion ( 11 ).

10. System according to claim 1 , wherein the system ( 1 ) is configured as an epi-illumination system.

11. System according to claim 1 , wherein the system comprises a computer ( 7 ) that is configured to process and to compare a recorded Raman spectrum to a plurality of Raman spectra or associated data that are stored in a database.

12. System according to claim 1 , wherein said optical fibre ( 22 ) is a multi-mode optical fibre, wherein the diameter of the optical fibre ( 22 ) is greater than or equal to 25 μm.

13. Method for measuring a Raman signal from a sample ( 2 ), particularly with a system ( 1 ) according to claim 1 , comprising the steps of

arranging a sample ( 2 ) housed in a closed sample chamber ( 10 ) at a distance ( 5 ) of at least 3 mm, 5 mm or 9 mm away from an objective lens ( 4 ), wherein a ceiling portion ( 11 ) of the sample chamber ( 10 ) is comprised in a lid ( 13 ) and wherein the ceiling portion ( 11 ) is arranged between the sample ( 2 ) and the objective lens ( 4 ), wherein said lid ( 13 ) can be opened and closed such that the chamber volume ( 12 ) comprised by the sample chamber ( 10 ) can be opened or closed, wherein the sample chamber ( 10 ) is further configured to keep a gas volume inside the chamber volume ( 12 ) separated from the atmosphere outside of the sample chamber ( 10 ), when the lid ( 13 ) is closed;

illuminating the sample ( 2 ) through the objective lens ( 4 ) and the ceiling portion ( 11 ) of the sample chamber ( 10 ) with excitation light ( 32 ), wherein the excitation light ( 32 ) is focused into a focal volume ( 31 ) onto or into the sample ( 2 ),

confocally detecting inelastically scattered light ( 33 ) from the illuminated focal volume ( 31 ) of the sample ( 2 ),

determining a Raman spectrum of the confocally detected inelastically scattered light ( 33 ).

14. Method according to claim 13 , wherein the method further comprises at least the steps of

comparing the determined Raman spectrum with a plurality of Raman spectra stored in a database and/or,

comparing the associated data from the determined Raman spectrum with data associated to a plurality of Raman spectra stored in a database.