| 1. |
- Amin Yavari, S., et al.
(författare)
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Layer by layer coating for bio-functionalization of additively manufactured meta-biomaterials
- 2020
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Ingår i: Additive Manufacturing. - : Elsevier BV. - 2214-8604 .- 2214-7810. ; 32
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Tidskriftsartikel (refereegranskat)abstract
- Additive manufacturing has facilitated fabrication of complex and patient-specific metallic meta-biomaterials that offer an unprecedented collection of mechanical, mass transport, and biological properties as well as a fully interconnected porous structure. However, applying meta-biomaterials for addressing unmet clinical needs in orthopedic surgery requires additional surface functionalities that should be induced through tailor-made coatings. Here, we developed multi-functional layer-by-layer coatings to simultaneously prevent implant-associated infections and stimulate bone tissue regeneration. We applied multiple layers of gelatin- and chitosan-based coatings containing either bone morphogenetic protein (BMP)-2 or vancomycin on the surface of selective laser melted porous structures made from commercial pure Titanium (CP Ti) and designed using a triply periodic minimal surface (i.e., sheet gyroid). The additive manufacturing process resulted in a porous structure and met the the design values comparatively. X-ray photoelectron spectroscopy spectra confirmed the presence and composition of the coating layers. The release profiles showed a continued release of both vancomycin and BMP-2 for 2–3 weeks. Furthermore, the developed meta-biomaterials exhibited a very strong antibacterial behavior with up to 8 orders of magnitude reduction in both planktonic and implant-adherent bacteria and no signs of biofilm formation. The osteogenic differentiation of mesenchymal stem cells was enhanced, as shown by two-fold increase in the alkaline phosphatase activity and up to four-fold increase in the mineralization of all experimental groups containing BMP-2. Eight-week subcutaneous implantation in vivo showed no signs of a foreign body response, while connective tissue ingrowth was promoted by the layer-by-layer coating. These results unequivocally confirm the superior multi-functional performance of the developed biomaterials.
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| 2. |
- Schuurmans, C. C. L., et al.
(författare)
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Complex coacervation-based loading and tunable release of a cationic protein from monodisperse glycosaminoglycan microgels
- 2018
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Ingår i: Soft Matter. - : Royal Society of Chemistry. - 1744-683X .- 1744-6848. ; 14:30, s. 6327-6341
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Tidskriftsartikel (refereegranskat)abstract
- Glycosaminoglycans (GAGs) are of interest for biomedical applications because of their ability to retain proteins (e.g. growth factors) involved in cell-to-cell signaling processes. In this study, the potential of GAG-based microgels for protein delivery and their protein release kinetics upon encapsulation in hydrogel scaffolds were investigated. Monodisperse hyaluronic acid methacrylate (HAMA) and chondroitin sulfate methacrylate (CSMA) micro-hydrogel spheres (diameters 500-700 μm), were used to study the absorption of a cationic model protein (lysozyme), microgel (de)swelling, intra-gel lysozyme distribution and its diffusion coefficient in the microgels dispersed in buffers (pH 7.4) of varying ionic strengths. Upon incubation in 20 mM buffer, lysozyme was absorbed up to 3 and 4 mg mg−1 dry microspheres for HAMA and CSMA microgels respectively, with loading efficiencies up to 100%. Binding stoichiometries of disaccharide : lysozyme (10.2 : 1 and 7.5 : 1 for HAMA and CSMA, respectively) were similar to those for GAG-lysozyme complex coacervates based on soluble GAGs found in literature. Complex coacervates inside GAG microgels were also formed in buffers of higher ionic strengths as opposed to GAG-lysozyme systems based on soluble GAGs, likely due to increased local anionic charge density in the GAG networks. Binding of cationic lysozyme to the negatively charged microgel networks resulted in deswelling up to a factor 2 in diameter. Lysozyme release from the microgels was dependent on the ionic strength of the buffer and on the number of anionic groups per disaccharide, (1 for HAMA versus 2 for CSMA). Lysozyme diffusion coefficients of 0.027 in HAMA and <0.006 μm2 s−1 in CSMA microgels were found in 170 mM buffer (duration of release 14 and 28 days respectively). Fluorescence Recovery After Photobleaching (FRAP) measurements yielded similar trends, although lysozyme diffusion was likely altered due to the negative charges introduced to the protein through the FITC-labeling resulting in weaker protein-matrix interactions. Finally, lysozyme-loaded CSMA microgels were embedded into a thermosensitive hydrogel scaffold. These composite systems showed complete lysozyme release in ∼58 days as opposed to only 3 days for GAG-free scaffolds. In conclusion, covalently crosslinked methacrylated GAG hydrogels have potential as controlled release depots for cationic proteins in tissue engineering applications.
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