Monday, October 22, 2018

Heterogeneity of Network Structures and Water Dynamics in κ-Carrageenan Gels Probed by Nanoparticle Diffusometry #DNPNMR

Kort, Daan W. de, Erich Schuster, Freek J.M. Hoeben, Ryan Barnes, Meike Emondts, Henk M. Janssen, Niklas Lorén, Songi Han, Henk Van As, and John P.M. van Duynhoven. “Heterogeneity of Network Structures and Water Dynamics in κ-Carrageenan Gels Probed by Nanoparticle Diffusometry.” Langmuir 34, no. 37 (September 18, 2018): 11110–20. 


A set of functionalized nanoparticles (PEGylated dendrimers, d = 2.8 - 9 nm) was used to probe the structural heterogeneity in Na+/K+ induced κ-carrageenan gels. The self-diffusion behavior of these nanoparticles as observed by 1H PFG NMR, FRAP and RICS revealed a fast and a slow component, pointing towards microstructural heterogeneity in the gel network. The self-diffusion behavior of the faster nanoparticles could be modelled with obstruction by a coarse network (average mesh size <100 nm), while the slower-diffusing nanoparticles are trapped in a dense network (lower mesh size limit of 4.6 nm). Overhauser DNP-enhanced NMR relaxometry revealed a reduced local solvent water diffusivity near TEMPO-labelled nanoparticles trapped in the dense network, showing that heterogeneity in the physical network is also reflected in heterogeneous self-diffusivity of water. The observed heterogeneity in mesh sizes and in water self-diffusivity is of interest for understanding and modelling of transport through and release of solutes from heterogeneous biopolymer gels.