title: Optical Projection Tomography Technique for Image Texture and Mass Transport Studies in Hydrogels Based on Gellan Gum.
abstract: The microstructure and permeability are crucial factors for the development of hydrogels for tissue engineering, since they influence cell nutrition, penetration, and proliferation. The currently available imaging methods able to characterize hydrogels have many limitations. They often require sample drying and other destructive processing, which can change hydrogel structure, or they have limited imaging penetration depth. In this work, we show for the first time an alternative nondestructive method, based on optical projection tomography (OPT) imaging, to characterize hydrated hydrogels without the need of sample processing. As proof of concept, we used gellan gum (GG) hydrogels obtained by several cross-linking methods. Transmission mode OPT was used to analyze image microtextures, and emission mode OPT to study mass transport. Differences in hydrogel structure related to different types of cross-linking and between modified and native GG were found through the acquired Haralick's image texture features followed by multiple discriminant analysis (MDA). In mass transport studies, the mobility of FITC-dextran (MW 20, 150, 2000 kDa) was analyzed through the macroscopic hydrogel. The FITC-dextran velocities were found to be inversely proportional to the size of the dextran as expected. Furthermore, the threshold size in which the transport is affected by the hydrogel mesh was found to be 150 kDa (Stokes' radii between 69 and 95 Å). On the other hand, the mass transport study allowed us to define an index of homogeneity to assess the cross-linking distribution, structure inside the hydrogel, and repeatability of hydrogel production. As a conclusion, we showed that the set of OPT imaging based material characterization methods presented here are useful for screening many characteristics of hydrogel compositions in relatively short time in an inexpensive manner, providing tools for improving the process of designing hydrogels for tissue engineering and drugs/cells delivery applications.
authors.affiliation: Computational Biophysics and Imaging Group, ELT Department, Tampere University of Technology , 33720 Tampere, Finland.|BioMediTech - Institute of Biosciences and Medical Technology,33720 Tampere, Finland.
authors.forename: Ana M
authors.initials: AM
authors.lastname: Soto
authors.affiliation: BioMediTech - Institute of Biosciences and Medical Technology,33720 Tampere, Finland.|Biomaterials and Tissue Engineering Group, ELT Department, Tampere University of Technology , 33720 Tampere, Finland.|Heart Group, BioMediTech, University of Tampere , 33720 Tampere, Finland.
authors.forename: Janne T
authors.initials: JT
authors.lastname: Koivisto
authors.affiliation: BioMediTech - Institute of Biosciences and Medical Technology,33720 Tampere, Finland.|Biomaterials and Tissue Engineering Group, ELT Department, Tampere University of Technology , 33720 Tampere, Finland.
authors.forename: Jenny E
authors.initials: JE
authors.lastname: Parraga
authors.affiliation: 3B's Research Group, Biomaterials, Biodegradables and Biomimetics, University of Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine Barco GMR, 4704-553 Braga, Portugal.|ICVS/3B's - PT Government Associate Laboratory, 4710-057 Braga/Guimarães, Portugal.
authors.forename: Joana
authors.initials: J
authors.lastname: Silva-Correia
authors.affiliation: 3B's Research Group, Biomaterials, Biodegradables and Biomimetics, University of Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine Barco GMR, 4704-553 Braga, Portugal.|ICVS/3B's - PT Government Associate Laboratory, 4710-057 Braga/Guimarães, Portugal.
authors.forename: Joaquim M
authors.initials: JM
authors.lastname: Oliveira
authors.affiliation: 3B's Research Group, Biomaterials, Biodegradables and Biomimetics, University of Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine Barco GMR, 4704-553 Braga, Portugal.|ICVS/3B's - PT Government Associate Laboratory, 4710-057 Braga/Guimarães, Portugal.
authors.forename: Rui L
authors.initials: RL
authors.lastname: Reis
authors.affiliation: BioMediTech - Institute of Biosciences and Medical Technology,33720 Tampere, Finland.|Biomaterials and Tissue Engineering Group, ELT Department, Tampere University of Technology , 33720 Tampere, Finland.
authors.forename: Minna
authors.initials: M
authors.lastname: Kellomäki
authors.affiliation: Computational Biophysics and Imaging Group, ELT Department, Tampere University of Technology , 33720 Tampere, Finland.|BioMediTech - Institute of Biosciences and Medical Technology,33720 Tampere, Finland.
authors.forename: Jari
authors.initials: J
authors.lastname: Hyttinen
authors.affiliation: Computational Biophysics and Imaging Group, ELT Department, Tampere University of Technology , 33720 Tampere, Finland.|BioMediTech - Institute of Biosciences and Medical Technology,33720 Tampere, Finland.
authors.forename: Edite
authors.initials: E
authors.lastname: Figueiras