Fluorescent Labeling Can Alter Polymer Solution Dynamics

Abstract

There is a widespread assumption that modest chemical modification of a large polymer molecule, by adding a fluorescent label or the like, has no significant effect on polymer solution dynamics. We here report that light tagging of hydroxypropylcellulose (HPC) with fluorescein dye has a significant effect on the dynamic behavior of the chains, as measured using fluorescence photobleaching recovery (FPR) and dynamic light scattering (DLS). We compared unprocessed HPC, HPC processed in preparation for chemical modification, and HPC chemically modified by tagging with a fluorescein moiety. Addition of covalently bound fluorescein to the polymer eliminates the ultraslow (D ≈ 10 −10 cm 2 /s) relaxational mode found with DLS in the unlabeled HPC samples. Our findings explain the perceived discrepancies between DLS and FPR studies of HPC solutions. The discrepancies arise from differences in sample preparation. Comparison of FPR spectra (which measure the single particle diffusion process) and DLS spectra (which measure the relative motions of pairs of particles), each with its own intrinsic time and distance scales, provides insight into the nature of diffusion and the state of dissolution in dilute and nondilute HPC solutions.

Probing the Growth Kinetics for the Formation of Uniform 1D Block Copolymer Nanoparticles by Living Crystallization-Driven Self-Assembly

“…This effect of dye structure on the growth rate had been ascribed to the required modification of the corona-forming block altering amphiphilicity of the BCP. 101 Finally, for the SRFM experiments the sample preparation methods prevented the addition of any remaining unimer present in the sample to the micelle termini, and therefore effectively quenched the self-assembly reaction. This was convenient as image acquisition times are typically between 2-10 minutes, depending on the SRFM technique, and it is therefore important that growth is halted prior to analysis.…”

“…The STAR635 dye-labeled BCP has a faster growth rate than the CAGE500-labeled BCP for the SMLM experiments. This effect of dye structure on the growth rate had been ascribed to the required modification of the corona-forming block altering amphiphilicity of the BCP . Finally, for the SRFM experiments the sample preparation methods prevented the addition of any remaining unimer present in the sample to the micelle termini and therefore effectively quenched the self-assembly reaction.…”

Ionization of short weak polyelectrolytes: when size matters

“…On a larger length scale (10-100 µm), the self-diffusion of the polyelectrolytes can be investigated using the Pulsed Field Gradient NMR (PFG-NMR) method. In contrast to fluorescence correlation spectroscopy (FCS), that measures the diffusion coefficients thanks to fluorescent moieties in the diffusing species [6,21], NMR does not need the grafting of additional external species that might alter the dynamics [22]. Furthermore, diffusion NMR is not affected by the limitations of the dynamic light scattering (DLS), from which diffusion coefficients can also be determined.…”

Effect of Synthesis Temperature on Size, Structure, and Volume Phase Transition of Polysaccharide Microgels

“…As an alternative to synthetic microgels, Lu et al developed microgels from a natural polysaccharide, hydroxypropyl cellulose (HPC). HPC is an amphiphilic, water-soluble, and neutral polymer with LCST ∼ 41 °C. , The polymer is already used as an FDA-approved food emulsifier , and drug encapsulator, , so it presents an advantage over synthetic polymers for therapeutic use. The HPC microgels themselves were shown to be potentially suitable nanoparticle candidates for tissue augmentation, while providing a good platform for various mechanisms of controlled release of biomolecules …”