Abstract
Soft adaptive networks like polymer gels are almost ideal candidates as surrogates for the extracellular matrix, more so when their rheo-mechanical properties can be carefully tuned by temperature. Using both dynamic light scattering and photon correlation imaging, we have investigated the phase behavior and the microscopic dynamics of a thermoresponsive network, Mebiol Gel, extensively and effectively used as a three-dimensional scaffold for cell growth. In the dilute limit, Mebiol displays a temperature-driven association process characterized by a significant increase of the molecular weight, which is not accompanied, however, by a concurrent increase of the aggregate size. This peculiar behavior is consistent with numerical simulations of a simpler but structurally homologous block-copolymer system. By increasing concentration and approaching gelation, the polymer solution progressively attains the structure of a percolating network, as witnessed by the logarithmic decay of the intensity correlation functions extending over many time decades, a relaxation behavior that is found well within the gel phase too. No evidence of a discontinuous transition to a fully arrested gel phase is, however, detectable in the microscopic dynamics.
Highlights
Biotechnologies are in strong demand for surrogates of the extracellular matrix (ECM) to be exploited as suitable threedimensional cell growth scaffolds
We first provided a semiquantitative (c, T) phase diagram of the system focusing on the boundary of the gel phase that, for the purpose of this work, will be defined as the region where the polymer solution mechanically behaves as a solid
We proceeded as follows: A tiny magnetic bar was placed at the bottom of a vial filled with the Mebiol solution and placed within a thermostat whose temperature was progressively raised until the yield strength σ of the system became sufficiently large to prevent the bar from settling when the vial was turned upside downc
Summary
Biotechnologies are in strong demand for surrogates of the extracellular matrix (ECM) to be exploited as suitable threedimensional cell growth scaffolds. To achieve this aim, candidate media must satisfy some crucial requisites. The ECM, a mosaic network made of several fibrous proteins intertwined with other complex biopolymers, is an efficient scaffold that hosts cells and facilitates their adhesion and is a complex active system that nurtures and protects cells allowing them to grow, proliferate, and migrate.[1] On the one hand, suitable substitutional media must behave as solid frames, resilient to tension and compression notwithstanding their tenuous structure. They must be prone to restructuring, either spontaneously or under a weak external stimulus, to allow cells for relocating and migrating. Thermoreversible polymer gels seem to be ideal candidates that can, in principle, satisfy all the former requisites.[3]
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