Diblock copolymer membranes investigated by single-particle tracking

Abstract

We report a study on particle diffusion in membranes formed from polystyrene-block-poly(2-(dimethylamino)ethyl methacrylate) (PS-b-PDMAEMA) diblock copolymers. The membranes were investigated by scanning electron microscopy and by single-particle tracking employing carboxy-functionalized polystyrene beads loaded with a fluorophore as spectroscopic probes. From the diffusion trajectories we extracted the domain size distribution of the membranes and the local diffusion coefficient of the beads as a function of the size of the beads. The single-particle tracking data revealed that the effective domain sizes of the membranes are reduced with respect to the domain sizes obtained from scanning electron microscopy, reflecting the confined diffusion of the probe particles due to interactions with the domain walls. This is corroborated by a clear correlation between the diffusion coefficient of an individual polystyrene bead and the size of the actual domain to which it is confined.

Setup for single-particle orbit tracking: artifacts and corrections

“…In the life sciences, reaction kinetics may depend crucially on the diffusion of the reactants [10][11][12], or in material engineering the flow of material through an interface is of great importance for filtering and catalysis [6,13]. Many methods for studying such processes rely on fluorescence microscopy.…”

Measuring a diffusion coefficient by single-particle tracking: statistical analysis of experimental mean squared displacement curves

“…[1][2][3][4][14][15][16][17][18][19][20][21] The developed methodology covers techniques where the movement of an individual particle can be followed by recording its diffractionlimited image on a sequence of CCD frames, 1 sophisticated approaches that compensate the Brownian motion using electrokinetic forces, 14 techniques that use structured illumination by actively designing the point-spread function of the microscope, 21,22 as well as methods that rely on a spatial modulation of the light that travels to or comes from the particle. 19 Fascinating results have been obtained, for example in biophysics the movement of molecules, viruses, or motor proteins could be made visible, [4][5][6] and in the materials science transport processes through nanoporous structures 7,8 or the manifestation of diffusion anomalies in liquid crystals and mesoporous structures could be followed. 9,23,24 Typically the fluorescence of a particle is monitored as a function of time and the position of the particle is extracted from the data with sub-diffraction limited accuracy.…”

Classification and Segmentation of Nanoparticle Diffusion Trajectories in Cellular Micro Environments

“…Unfortunately, there is no established positive control for constrained diffusion like CD and AD at the moment [40]. However, a candidate model with particles trapped in circular containments was developed by Haramagatti et al [13] and is discussed by Saxton [40]. We applied our procedure to footage provided by Haramagatti et al and got plausible results.…”

“…Each movie is a sequence of 1000-2000 images. A detailed description of the method is available elsewhere [13]. …”

“…Furthermore we will give advice on parameter selection and investigate the working range by a sensitivity analysis. The refined method was applied to videos of diffusing particles captured by nanoparticle tracking analysis (NTA), to videos of particles in micron-sized confinements [13], and to videos of particles inside and outside of live cultured lung fibroblasts (V79). To view particles in cells, darkfield microscopy (DFM) and confocal laser scanning microscopy (CLSM) operated in the reflection mode were chosen.…”