title: Gelling kinetics and in situ mineralization of alginate hydrogels: A correlative spatiotemporal characterization toolbox.
abstract: Due to their large water content and structural similarities to the extracellular matrix, hydrogels are an attractive class of material in the tissue engineering field. Polymers capable of ionotropic gelation are of special interest due to their ability to form gels at mild conditions. In this study we have developed an experimental toolbox to measure the gelling kinetics of alginate upon crosslinking with calcium ions. A reaction-diffusion model for gelation has been used to describe the diffusion of calcium within the hydrogel and was shown to match experimental observations well. In particular, a single set of parameters was able to predict gelation kinetics over a wide range of gelling ion concentrations. The developed model was used to predict the gelling time for a number of geometries, including microspheres typically used for cell encapsulation. We also demonstrate that this toolbox can be used to spatiotemporally investigate the formation and evolution of mineral within the hydrogel network via correlative Raman microspectroscopy, confocal laser scanning microscopy and electron microscopy.
  
  
  
  Hydrogels show great promise in cell-based tissue engineering, however new fabrication and modification methods are needed to realize the full potential of hydrogel based materials. The inclusion of an inorganic phase is one such approach and is known to affect both cell-material interactions and mechanical properties. This article describes the development of a correlative experimental approach where gel formation and mineralization has been investigated with spatial and temporal resolution by applying Raman microspectroscopy, optical and electron microscopy and a reaction-diffusion modeling scheme. Modeling allows us to predict gelling kinetics for other geometries and sizes than those investigated experimentally. Our experimental system enables non-destructive study of composite hydrogel systems relevant for, but not limited to, applications within bone tissue engineering.
authors: Department of Physics, NTNU, Norwegian University of Science and Technology, 7491 Trondheim, Norway. Electronic address: sindre.bjornoy@ntnu.no.
authors: Sindre H
authors: SH
authors: Bjørnøy
authors: Department of Physics, NTNU, Norwegian University of Science and Technology, 7491 Trondheim, Norway.
authors: Stefan
authors: S
authors: Mandaric
authors: Department of Physics, NTNU, Norwegian University of Science and Technology, 7491 Trondheim, Norway. Electronic address: david.bassett@ntnu.no.
authors: David C
authors: DC
authors: Bassett
authors: Department of Physics, NTNU, Norwegian University of Science and Technology, 7491 Trondheim, Norway. Electronic address: andreas.aslund@ntnu.no.
authors: Andreas K O
authors: AK
authors: Slund
authors: Department of Chemical Engineering, NTNU, Norwegian University of Science and Technology, 7491 Trondheim, Norway. Electronic address: seniz.ucar@ntnu.no.
authors: Seniz
authors: S
authors: Ucar
authors: Department of Chemical Engineering, NTNU, Norwegian University of Science and Technology, 7491 Trondheim, Norway. Electronic address: jens-petter.andreassen@ntnu.no.
authors: Jens-Petter
authors: JP
authors: Andreassen
authors: Department of Biotechnology, NTNU, Norwegian University of Science and Technology, 7491 Trondheim, Norway. Electronic address: berit.l.strand@ntnu.no.
authors: Berit L
authors: BL
authors: Strand
authors: Department of Physics, NTNU, Norwegian University of Science and Technology, 7491 Trondheim, Norway. Electronic address: pawel.sikorski@ntnu.no.
authors: Pawel
authors: P
authors: Sikorski
mesh_terms: D000464:Alginates / Q000737:chemistry*; D020723:Glucuronic Acid / Q000737:chemistry; D006603:Hexuronic Acids / Q000737:chemistry; D020100:Hydrogels / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008853:Microscopy; D008903:Minerals / Q000737:chemistry; D008962:Models, Theoretical; D062211:Spatio-Temporal Analysis; D013059:Spectrum Analysis, Raman; D013997:Time Factors
chemical_list: D000464:Alginates; D006603:Hexuronic Acids; D020100:Hydrogels; D008903:Minerals; D020723:Glucuronic Acid
keywords: Alginate; Hydrogel; Modeling; Raman spectroscopy