Developing a biodegradable scaffold remains a major challenge in bone tissue engineering. This study was aimed at developing novel alginate-chitosan-collagen (SA-CS-Col)-based composite scaffolds consisting of graphene oxide (GO) to enrich porous structures, elicited by the freeze-drying technique. To characterize porosity, water absorption, and compressive modulus, GO scaffolds (SA-CS-Col-GO) were prepared with and without Ca2+-mediated crosslinking (chemical crosslinking) and analyzed using Raman, Fourier transform infrared (FTIR), X-ray diffraction (XRD), and scanning electron microscopy techniques. The incorporation of GO into the SA-CS-Col matrix increased both crosslinking density as indicated by the reduction of crystalline peaks in the XRD patterns and polyelectrolyte ion complex as confirmed by FTIR. GO scaffolds showed increased mechanical properties which were further increased for chemically crosslinked scaffolds. All scaffolds exhibited interconnected pores of 10-250 μm range. By increasing the crosslinking density with Ca2+, a decrease in the porosity/swelling ratio was observed. Moreover, the SA-CS-Col-GO scaffold with or without chemical crosslinking was more stable as compared to SA-CS or SA-CS-Col scaffolds when placed in aqueous solution. To perform in vitro biochemical studies, mouse osteoblast cells were grown on various scaffolds and evaluated for cell proliferation by using MTT assay and mineralization and differentiation by alizarin red S staining. These measurements showed a significant increase for cells attached to the SA-CS-Col-GO scaffold compared to SA-CS or SA-CS-Col composites. However, chemical crosslinking of SA-CS-Col-GO showed no effect on the osteogenic ability of osteoblasts. These studies indicate the potential use of GO to prepare free SA-CS-Col scaffolds with preserved porous structure with elongated Col fibrils and that these composites, which are biocompatible and stable in a biological medium, could be used for application in engineering bone tissues.

Graphene Oxide—A Tool for the Preparation of Chemically Crosslinking Free Alginate–Chitosan–Collagen Scaffolds for Bone Tissue Engineering

The role of transparent exopolymer particles (TEP) in membrane fouling: A critical review

Biofouling and me: My Stockholm syndrome with biofilms

Contemporary antibiofouling modifications of reverse osmosis desalination membrane: A review

https://biblio.ugent.be/publication/8686178/file/8686180.pdf

Cost of fouling in full-scale reverse osmosis and nanofiltration installations in the Netherlands

Enhanced biofilm solubilization by urea in reverse osmosis membrane systems.

Structural extracellular polymeric substances (structural EPS) can form stable hydrogels and are considered to be responsible for the stability of biofilms and aerobic granular sludge. Structural EPS were extracted from aerobic granular sludge and characterized for their gel-forming capacity with different alkaline earth and transition metal ions. The structural EPS hydrogels were compared to alginate hydrogels. Alginate is a well characterized polymer which is able to form stiff hydrogels with multivalent ions. The stiffness of the obtained hydrogels was measured with dynamic mechanical analysis and quantified by the Young's modulus. Furthermore the stability of structural EPS hydrogels towards disintegration in the presence of ethylenediaminetetraacetic acid (EDTA) was evaluated at pH 4.5–10.5 and compared to that of alginate, polygalacturonic acid and κ-carrageenan. The stiffness of alginate hydrogels was multiple times higher than that of structural EPS. Alkaline earth metals resulted in stiffer alginate hydrogels than transition metals. For structural EPS this trend was opposite to alginate. Independent of the pH, polysaccharide hydrogels were quickly disintegrated when being exposed to EDTA. Structural EPS hydrogels demonstrated greater stability towards EDTA and were still intact after one month at pH 4.5–8.5. It is suggested that the gelling mechanism of structural EPS is not only related to metal ion complexation of the polymers, but to a combination of interactions of multiple functional groups present in structural EPS. This study helps to further understand and characterize structural EPS from aerobic granular sludge, and therewith understand its stability and that of biofilms in general.

/pdf/impact-of-metal-ions-on-structural-eps-hydrogels-from-1yli6efa2z.pdf

Impact of metal ions on structural EPS hydrogels from aerobic granular sludge.

A highly ordered alginate/montmorillonite bionanocomposite structure is presented. The alignment of the bionanocomposites has been determined by environmental scanning electron microscopy (ESEM) and wide-angle X-ray scattering (WAXS). The ESEM micrographs show a high in-plane orientation of the bionanocomposite, while 2D X-ray scattering images show a clear angle dependency that confirms preferential orientation of montmorillonite (MMT) platelets. The order parameter (⟨P2⟩) was calculated from azimuthal intensity profiles derived from WAXS measured over the MMT 001 reflection, using the Maier–Saupe and the affine deformation model. We observe that the ⟨P2⟩ values depend on the MMT concentration, which is explained by the MMT–alginate interaction. We propose an affine deformation model based on gel formation achieved by alginate adsorption on the edges of MMT, which develops yield stress and deforms the MMT platelets during drying resulting in high range ⟨P2⟩ values.

Origin of Highly Ordered Sodium Alginate/Montmorillonite Bionanocomposites

https://biblio.ugent.be/publication/8663715/file/8663716.pdf

A comparison between chemical cleaning efficiency in lab-scale and full-scale reverse osmosis membranes: Role of extracellular polymeric substances (EPS)

Jure Zlopasa

Papers

Enhanced biofilm solubilization by urea in reverse osmosis membrane systems.

Impact of metal ions on structural EPS hydrogels from aerobic granular sludge.

Origin of Highly Ordered Sodium Alginate/Montmorillonite Bionanocomposites

A comparison between chemical cleaning efficiency in lab-scale and full-scale reverse osmosis membranes: Role of extracellular polymeric substances (EPS)

Water Sorption and Diffusion in (Reduced) Graphene Oxide-Alginate Biopolymer Nanocomposites