Method of determining lipoprotein concentration in solution using light scattering
The invention relates the use of single particle light scattering, preferably interferometric scattering microscopy (also referred to herein as iSCAT), to measure the concentration of a particle in a solution. The invention furthermore relates to the use of light scattering to detect lipoprotein particles in a sample, and to related diagnostic and treatment methods.
1. A method of measuring the concentration of a particle in a sample, comprising directly contacting the sample with a surface and detecting the non-specific binding of said particle to the surface using single particle interferometric light scattering, wherein the binding rate of the particle to the surface is determined from detecting the binding of the particle.
2. A method as claimed in claim 1 , wherein said surface is passivated, activated, coated, treated or derivatized.
3. A method as claimed in claim 1 , wherein the detection of binding of the particle to the surface is repeated after one or more time intervals.
4. A method as claimed in claim 3 , wherein the repeated detection of binding of said particles to the surface permits calculation of the initial rate of binding of the particle to the surface.
5. A method as claimed in claim 4 , wherein the initial binding rate of the particle is compared to the initial binding rate of a known concentration of the particle.
6. A method as claimed in claim 1 wherein the detection of binding of said particles to the surface permits calculation of the constant binding rate of the particle.
7. A method as claimed in claim 6 wherein the constant binding rate of the particle is compared to the constant binding rate for a known concentration of the particle.
8. A method as claimed in claim 1 , for measuring the concentration of particle a sample, said method comprising:
i) contacting the sample with a surface;
ii) detecting the non-specific particle binding to the surface as visualized by single particle interferometric light scattering;
iii) repeating the detection step and calculating the changes in initial binding rate over time of the particle to the surface;
iv) providing a calibration curve of initial binding rate against concentration based on data from solutions of known particle concentration;
v) using the calibration curve in step (iv) to convert the initial binding rate recorded for the solution in step (iii) to the concentration of the particle in solution.
9. The method as claimed in claim 1 , wherein the concentration is absolute concentration.
10. The method as claimed in claim 1 , wherein said particle is also contacted with a measuring solution.
11. The method as claimed in claim 1 , wherein said sample is contacted with said surface in the presence of a calibrant and the binding of said calibrant to said surface is detected using single particle interferometric light scattering.
12. The method as claimed in claim 11 wherein the binding rate of the calibrant is compared to the binding rate of said particle.
13. The method as claimed in claim 11 wherein the concentration of the calibrant is known.
14. The method of claim 1 , wherein said sample is a biological sample.
15. The method as claimed in claim 14 wherein said sample or biological sample is obtained from a human individual.
16. The method as claimed in claim 14 wherein said biological sample is blood, plasma, or serum.
17. A method as claimed in claim 1 wherein the binding rate is determined by a single detection of binding of particles to the surface.
18. The method as claimed in claim 1 , wherein said particle is not labelled.
19. The method of claim 1 wherein the mass of the particle is determined by single particle interferometric light scattering, and said mass permits identification of the particle.
20. The method of claim 1 wherein said method comprises the use of an interferometric scattering microscope comprising:
a sample holder for holding a sample in a sample location;
an illumination source arranged to provide illuminating light;
a detector;
an optical system being arranged to direct illuminating light onto the sample location and being arranged to collect output light in reflection, the output light comprising both light scattered from the sample location and illuminating light reflected from the sample location, and direct the output light to the detector; and a spatial filter positioned to filter the output light, the spatial filter being arranged to pass output light but with a reduction in intensity that is greater within a predetermined numerical aperture than at larger numerical apertures.
21. The method of claim 1 wherein said surface is glass, sapphire or made from transparent polymer.