Identifying and analysing heterogeneity in soft biomaterials
In many areas, ranging from food science to pharmaceutics, the microstructure plays a major role in determining the properties of soft biomaterials. Functionalities such as controlled release of drugs and water management in foods depend to a large extent on the mass transport properties, and there is a strong correlation between the detailed structure and the diffusion properties of the material. The structure acts like a three-dimensional sieve in which the solutes are diffusing. The structure of biomaterials is often heterogeneous and coupling of the structure and diffusion properties is essential for the functionality of heterogeneous biomaterials. In the literature there are several powerful quantitative microscopy methods including fluorescence recovery after photobleaching, image correlation spectroscopy techniques, single particle tracking (SPT), and the promising recently developed method Raster Image Correlation Spectroscopy (RICS) to determine diffusion properties of soft biomaterials. In RICS, images are obtained by moving the scanning beam of a confocal laser scanning microscope across the sample according to a raster pattern, which introduces a specific time structure and provides information about the dynamics in the image. We have developed a new analysis method SPRICS, Single Particle Raster Image Correlation Spectroscopy, where we combine some aspects of single particle tracking and raster scan images to analyse dynamics of individual particles. In a comparison with RICS on both simulated and experimental data the new method gives more accurate estimates. As the new method is based on single particles, it can easily be applied to heterogeneous environments. Particles can either have different diffusion coefficients, or the dynamics and thus the diffusion may vary in space.
Joint work with E. Schuster, N. Lorén, A. Särkkä and M. Rudemo.