Publications

Hydrogels with cell adhesive moieties stand out as promising materials to enhance tissue healing and regeneration. Nonetheless, bacterial infections of the implants represent an unmet major concern. In the present work, we developed an alginate hydrogel modified with a multifunctional peptide containing the RGD cell adhesive motif in combination with an antibacterial peptide derived from the 1-11 region of lactoferrin (LF). The RGD-LF branched peptide was successfully anchored to the alginate backbone by carbodiimide chemistry, as demonstrated by 1H NMR and fluorescence measurements. The functionalized hydrogel presented desirable physicochemical properties (porosity, swelling and rheological behavior) to develop biomaterials for tissue engineering. The viability of mesenchymal stem cells (MSCs) on the peptide-functionalized hydrogels was excellent, with values higher than 85 % at day 1, and higher than 95 % after 14 days in culture. Moreover, the biological characterization demonstrated the ability of the hydrogels to significantly enhance ALP activity of MSCs as well as to decrease bacterial colonization of both Gram-positive and Gram-negative models. Such results prove the potential of the functionalized hydrogels as novel biomaterials for tissue engineering, simultaneously displaying cell adhesive activity and the capacity to prevent bacterial contamination, a dual bioactivity commonly not found for these types of hydrogels. In this work we report on the functionalization of an alginate hydrogel with a tailor-made multifunctional peptide containing the cell adhesive RGD motif and the LF1-11 antibacterial peptide. Such novel multifunctional biomaterial ensures the viability of human mesenchymal stem cells, enhances ALP activity and decreases bacterial infections of both Gram-positive and Gram-negative models. image

JTD Keywords: Alginate hydrogel, Alginates, Anti-bacterial agents, Antimicrobial peptid, Antimicrobial peptide, Antimicrobial peptides, Arginyl-glycyl-aspartic acid, Biocompatible materials, Biofunctionalization, Bone, Cell adhesion, Cell survival, Composite hydrogels, Cross-linking, Hlf1-11 peptide, Human lactoferrin, Humans, Hydrogels, Immobilization, Mesenchymal stem cells, Multifunctional peptide, Oligopeptides, Peptides, Physical-properties, Scaffolds, Surfac, Tissue engineering

There is a growing interest in developing natural hydrogel-based scaffolds to culture cells in a three-dimensional (3D) millieu that better mimics the in vivo cells' microenvironment. A promising approach is to use hydrogels from animal tissues, such as decellularized extracellular matrices; however, they usually exhibit suboptimal mechanical properties compared to native tissue and their composition with hundreds of different protein complicates to elucidate which stimulus triggers cell's responses. As simpler scaffolds, type I collagen hydrogels are used to study cell behavior in mechanobiology even though they are also softer than native tissues. In this work, type I collagen is mixed with bacterial nanocellulose fibers (BCf) to develop reinforced scaffolds with mechanical properties suitable for 3D cell culture. BCf were produced from blended pellicles biosynthesized from Komagataeibacter xylinus. Then, BCf were mixed with concentrated collagen from rat-tail tendons to form composite hydrogels. Confocal laser scanning microscopy and scanning electron microscopy images confirmed the homogeneous macro- and microdistribution of both natural polymers. Porosity analysis confirmed that BCf do not disrupt the scaffold structure. Tensile strength and rheology measurements demonstrated the reinforcement action of BCf (43% increased stiffness) compared to the collagen hydrogel while maintaining the same viscoelastic response. Additionally, this reinforcement of collagen hydrogels with BCf offers the possibility to mix cells before gelation and then proceed to the culture of the 3D cell scaffolds. We obtained scaffolds with human bone marrow-derived mesenchymal stromal cells or human fibroblasts within the composite hydrogels, allowing a homogeneous 3D viable culture for at least 7 days. A smaller surface shrinkage in the reinforced hydrogels compared to type I collagen hydrogels confirmed the strengthening of the composite hydrogels. These collagen hydrogels reinforced with BCf might emerge as a promising platform for 3D in vitro organ modeling, tissue-engineering applications, and suitable to conduct fundamental mechanobiology studies.

JTD Keywords: 3d cell culture, bacterial cellulose, collagen, composite hydrogels, 3d cell culture, Bacterial cellulose, Cellulose/collagen composite, Collagen, Composite hydrogels, Contraction, Cross-linking, Cytocompatibility, Fibroblasts, Matrix, Mechanical-properties, Reinforcement, Stiffness, Tissue engineering

With the currently available materials and technologies it is difficult to mimic the mechanical properties of soft living tissues. Additionally, another significant problem is the lack of information about the mechanical properties of these tissues. Alternatively, the use of phantoms offers a promising solution to simulate biological bodies. For this reason, to advance in the state-of-the-art a wide range of organs (e.g., liver, heart, kidney as well as brain) and hydrogels (e.g., agarose, polyvinyl alcohol –PVA–, Phytagel –PHY– and methacrylate gelatine –GelMA–) were tested regarding their mechanical properties. For that, viscoelastic behavior, hardness, as well as a non-linear elastic mechanical response were measured. It was seen that there was a significant difference among the results for the different mentioned soft tissues. Some of them appear to be more elastic than viscous as well as being softer or harder. With all this information in mind, a correlation between the mechanical properties of the organs and the different materials was performed. The next conclusions were drawn: (1) to mimic the liver, the best material is 1% wt agarose; (2) to mimic the heart, the best material is 2% wt agarose; (3) to mimic the kidney, the best material is 4% wt GelMA; and (4) to mimic the brain, the best materials are 4% wt GelMA and 1% wt agarose. Neither PVA nor PHY was selected to mimic any of the studied tissues. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

JTD Keywords: brain, composite hydrogel, dynamic mechanical analysis, elastography, hardness, hydrogels, in-vitro, liver, materials, mechanical-properties, mimicking, soft tissues, tissue scaffolding, viscoelasticity, warner-braztler shear test, warner–braztler shear test, Dynamic mechanical analysis, Hardness, Hydrogels, Materials, Mimicking, Soft tissues, Tissue scaffolding, Viscoelastic characterization, Viscoelasticity, Warner–braztler shear test