In the present work, porous gelatin scaffolds were prepared by cryogenic treatment of a chemicall... more In the present work, porous gelatin scaffolds were prepared by cryogenic treatment of a chemically cross-linked gelatin hydrogel, followed by removal of the ice crystals formed through lyophilization. This technique often leads to porous gels with a less porous skin. A simple method has been developed to solve this problem. The present study demonstrates that the hydrogel pore size decreased with an increasing gelatin concentration and with an increasing cooling rate of the gelatin hydrogel. Variation of the cryogenic parameters applied also enabled us to develop scaffolds with different pore morphologies (spherical versus transversal channel-like pores). In our opinion, this is the first paper in which temperature gradients during controlled cryogenic treatment were applied to induce a pore size gradient in gelatin hydrogels. With a newly designed cryo-unit, temperature gradients of 10 and 30°C were implemented during the freezing step, resulting in scaffolds with average pore diameters of, respectively, (116 and (330 µm. In both cases, the porosity and pore size decreased gradually through the scaffolds. Pore size and structure analysis of the matrices was accomplished through a combination of microcomputed tomography using different software packages (µCTanalySIS and Octopus), scanning electron microscopy analysis, and helium pycnometry.
To progress the fields of tissue engineering (TE) and regenerative medicine, development of quant... more To progress the fields of tissue engineering (TE) and regenerative medicine, development of quantitative methods for non-invasive three dimensional characterization of engineered constructs (i.e. cells/tissue combined with scaffolds) becomes essential. In this study, we have defined the most optimal staining conditions for contrast-enhanced nanofocus computed tomography for three dimensional visualization and quantitative analysis of in vitro engineered neo-tissue (i.e. extracellular matrix containing cells) in perfusion bioreactordeveloped Ti6Al4V constructs. A fractional factorial 'design of experiments' approach was used to elucidate the influence of the staining time and concentration of two contrast agents (Hexabrix and phosphotungstic acid) and the neo-tissue volume on the image contrast and dataset quality. Additionally, the neo-tissue shrinkage that was induced by phosphotungstic acid staining was quantified to determine the operating window within which this contrast agent can be accurately applied. For Hexabrix the staining concentration was the main parameter influencing image contrast and dataset quality. Using phosphotungstic acid the staining concentration had a significant influence on the image contrast while both staining concentration and neo-tissue volume had an influence on the dataset quality. The use of high concentrations of phosphotungstic acid did however introduce significant shrinkage of the neo-tissue indicating that, despite sub-optimal image contrast, low concentrations of this staining agent should be used to enable quantitative analysis. To conclude, design of experiments allowed us to define the most optimal staining conditions for PLOS ONE |
Journal of tissue engineering and regenerative medicine, Jan 15, 2015
Porous biodegradable scaffolds represent promising candidates for tissue-engineering applications... more Porous biodegradable scaffolds represent promising candidates for tissue-engineering applications because of their capability to be preseeded with cells. We report an uncrosslinked chitosan scaffold designed with the aim of inducing and supporting enzyme-mediated formation of apatite minerals in the absence of osteogenic growth factors. To realize this, natural enzyme alkaline phosphatase (ALP) was incorporated into uncrosslinked chitosan scaffolds. The uncrosslinked chitosan makes available amine and alcohol functionalities to enhance the biomineralization process. The physicochemical findings revealed homogeneous mineralization, with the phase structure of the formed minerals resembling that of apatite at low mineral concentrations, and similar to dicalcium phosphate dihydrate (DCPD) with increasing ALP content. The MC3T3 cell activity clearly showed that the mineralization of the chitosan scaffolds was effective in improving cellular adhesion, proliferation and colonization. Copy...
ABSTRACT Superabsorbent polymers (SAPs) have already found their way in many applications. These ... more ABSTRACT Superabsorbent polymers (SAPs) have already found their way in many applications. These ‘smart’ polymers undergo major characteristic changes by small environmental variations. In the present work, copolymer networks composed of acrylic acid, acrylamide and N,N′-methylenebisacrylamide have been synthesized using free radical precipitation polymerization. The polymers obtained have been characterized for their chemical structure, moisture (de)sorption and swelling behaviour using, respectively, attenuated total reflectance-infrared spectroscopy, high-resolution magic-angle spinning NMR spectroscopy, dynamic vapour sorption and swelling studies. The results indicated a remarkable moisture uptake capacity at high relative humidities of more than 90 % the original polymer weight with a negligible hysteresis. The latter implies that the SAPs developed are very promising water reservoir candidates, which become useful in concrete-related applications. Furthermore, the swelling data revealed that polymers with a low cross-linking density result in materials with superabsorbent properties. In addition, these SAPs show a pH-dependent swelling behaviour up to 450 times their original weight at pH 12.
In recent years a number of experimental and simulation studies of adsorption of water in pores h... more In recent years a number of experimental and simulation studies of adsorption of water in pores have appeared in the literature [1]. In this regard, the understanding and modeling of water vapour isotherms of activated carbons has been extensively researched, although the mechanism of water adsorption is not yet fully understood and is still object of discussion. The objective of this investigation is to elucidate if some of the previously proposed models for water adsorption in carbon materials have a wider range of application, enabling their use with other kind of materials, such as for example concrete. Evaporable water content evolution in concrete with time may have an internal origin (the so-called self desiccation) due to cement hydration or/and an external origin (exchanges with the environment, according to weathering conditions). It generates, respectively, early-age shrinkage and delayed deformations, along with associated cracking. This shows that water solely is likely...
The biggest problem in concrete are cracks occurring due to the relatively low tensile strength. ... more The biggest problem in concrete are cracks occurring due to the relatively low tensile strength. These cracks can generate an entrance for harmful compounds which are dissolved in fluids and gases and endanger the durability of concrete. The cost for crack repair is very high. Instead, inserting a polymer during concrete mixing can create a crack-sealing material. Using a hydrogel will help to heal cracks as soon as they occur, without any external interference. Fresh cement pore solution has a pH value of 12.8, but when a crack occurs, the pH lowers to 9 - 10 or even lower according to the environment of the application. At this lower pH value, the swelling degree of the inserted hydrogel must be high enough to fill up the crack. A swelling capacity curve was made over the entire pH-range (pH 1-13). The hydrogel gave a high swelling degree (over 450 times its own weight) at these pH values and may therefore be useful to use in concrete. The added amount of hydrogel was chosen at 0....
A good understanding of the nano-pore structure gives insight in several concrete properties like... more A good understanding of the nano-pore structure gives insight in several concrete properties like compressive strength, permeability and durability aspects. Dynamic water vapour sorption tests may be used to study this porosity, but the technique is difficult to interpret as the microstructure is very sensitive to stress, drying and rehydration due to humidity exposure. The removal of interlayer water held by gel pores in C-S-H or chemically bound water can also cause considerable microstructural shrinkage. As all drying techniques more or less dehydrate C-S-H and ettringite, they cause a restructuration of the C-S-H, changing the C-S-H in denser ones. Several drying techniques were studied. These include: no-drying, freeze-drying, oven-drying at 40°C and 105°C, air-drying in the presence of silica gel (20±2°C), vacuum-drying (20±2°C), and the solvent-exchange-method in methanol and isopropanol followed by vacuum-drying (20±2°C). The effect of these various drying techniques on the ...
International journal of immunopathology and pharmacology
Bone tissue engineering typically uses biomaterial scaffolds, osteoblasts or cells that can becom... more Bone tissue engineering typically uses biomaterial scaffolds, osteoblasts or cells that can become osteoblasts, and biophysical stimulations to promote cell attachment and differentiation. In this study, we investigated the effects of an electromagnetic wave on mesenchymal stromal cells isolated from the bone marrow and seeded upon gelatin cryogel disks. In comparison with control conditions without electromagnetic stimulus, the electromagnetic treatment (magnetic field, 2 mT; frequency, 75 Hz) increased the cell proliferation and differentiation and enhanced the biomaterial surface coating with bone extracellular matrix proteins. Using this tissue-engineering approach, the gelatin biomaterial, coated with differentiated cells and their extracellular matrix proteins, may be used in clinical applications as an implant for bone defect repair.
Experimental biology and medicine (Maywood, N.J.), Jan 10, 2014
Continuous glucose monitoring (CGM) is crucial in diabetic care. Long-term CGM systems however re... more Continuous glucose monitoring (CGM) is crucial in diabetic care. Long-term CGM systems however require an accurate sensor as well as a suitable measuring environment. Since large intravenous sensors are not feasible, measuring inside the interstitial fluid is considered the best alternative. This option, unfortunately, has the drawback of a lag time with blood glucose values. A good strategy to circumvent this is to enhance tissue integration and enrich the peri-implant vasculature. Implants of different optically transparent biomaterials (poly(methyl-methacrylate) [PMMA] and poly(dimethylsiloxane) [PDMS]) - enabling glucose monitoring in the near-infrared (NIR) spectrum - were surface-treated and subsequently implanted in goats at various implantation sites for up to 3 months. The overall in vivo biocompatibility, tissue integration, and vascularization at close proximity of the surfaces of these materials were assessed. Histological screening showed similar tissue reactions indepe...
European journal of pharmaceutical sciences : official journal of the European Federation for Pharmaceutical Sciences, 2003
We report here the physicochemical and biological evaluation of a series of polymethacrylates wit... more We report here the physicochemical and biological evaluation of a series of polymethacrylates with side groups of different pK(a) values, such as tertiary amines, pyridine groups, acid functions and imidazole groups as synthetic vectors for gene delivery. The ability of the different polymers to condense DNA was studied by ethidium bromide exclusion tests and agarose gel electrophoresis. The results show that all polymers are able to condense DNA. Both the molecular weight and the chemical composition of the polymers have an influence on the DNA condensation process. Furthermore, the biological properties of the polymer-DNA complexes were investigated, including their haemolytic activity, cytotoxicity and in vitro transfection efficiency. Complexes based on polymers containing only tertiary amines, have a transfection efficiency similar to that of poly(ethyleneimine) (PEI). Polymers containing pyridine groups have a reduced transfection efficiency compared to polymers containing ter...
Biomedical Foams for Tissue Engineering Applications, 2014
ABSTRACT In the present review, the state-of-the-art of porous hydrogel foams will be described a... more ABSTRACT In the present review, the state-of-the-art of porous hydrogel foams will be described and emphasis will be made on their relevance for biomedical applications and more specifically, tissue repair. The description aims at emphasizing both some novel aspects as well as the versatility of hydrogel foams. In addition, an overview of some general hydrogel aspects will be given. Next, a section will deal with natural polymers commonly used and suitable for hydrogel foam development and their respective tissue regeneration applications, followed by a description on advanced technologies applied to design and characterize novel hydrogel foams.
Polymers are commonly used in industry for packaging applications and as protective coatings but ... more Polymers are commonly used in industry for packaging applications and as protective coatings but are sometimes unsuitable to use due to their low surface energies. For these latter applications, surface modification is usually necessary to improve wettability, printability and adhesive properties. In the past decades, plasma surface treatment of polymers has been extensively studied and different treatment conditions have been
In the present work, we report on the biofunctionalisation of silanised Ti-surfaces with gelatin.... more In the present work, we report on the biofunctionalisation of silanised Ti-surfaces with gelatin. In recent years, a large number of papers have been published about the silanisation of different substrates including Ti-surfaces for biomedical applications. However, a comparative study evaluating the effects of different pre-treatment methods (cleaning and/or oxidation) and the efficiency of different silanisation reactions has to our information not yet been published. Since a clean and reproducible surface is required for studying structure-property relations, all Ti-surfaces were subjected to a three step procedure including a cleaning step, an oxidation step and a silanisation step. XPS analysis and contact angle measurements revealed that the pre-treatment of the Ti samples (cleaning + oxidation) had a drastic effect both on the surface composition and its wettability. A detailed study on the effect of different silanisation parameters indicated that the siloxane concentration, the siloxane type, the solvent and a catalyst affect the coupling efficiency of siloxanes to Ti-surfaces. Stability studies revealed a dependency between the siloxane type and the stability of the siloxane coating against hydrolytic cleavage from a Ti-surface. Since Ti-surfaces modified with a methacrylate containing silane possessed the highest hydrolytic stability, these surfaces were selected for the subsequent immobilisation of methacrylamide-modified gelatin via high energy irradiation induced cross-linking. The present work clearly demonstrates the need of a proper reaction strategy for immobilising ligands on Ti-surfaces.
Hydrogels of biocompatible calcium-crosslinkable polysaccharide gellan gum (GG) were enriched wit... more Hydrogels of biocompatible calcium-crosslinkable polysaccharide gellan gum (GG) were enriched with bioglass particles to enhance (i) mineralization with calcium phosphate (CaP); (ii) antibacterial properties and (iii) growth of bone-forming cells for future bone regeneration applications.
Photonics Packaging, Integration, and Interconnects Ix, 2009
We present a concept for an artificial optical skin, a flexible foil in which a novel type of opt... more We present a concept for an artificial optical skin, a flexible foil in which a novel type of optical force sensing elements is integrated. The principle relies on the change in coupling between two arrays of crossing polymer waveguides separated by a thin layer of soft silicone. ...
Biomaterials have been widely used in reconstructive bone surgery to heal critical-size long bone... more Biomaterials have been widely used in reconstructive bone surgery to heal critical-size long bone defects due to trauma, tumor resection, and tissue degeneration. In particular, gelatin cryogel scaffolds are promising new biomaterials owing to their biocompatibility; in addition, the in vitro modification of biomaterials with osteogenic signals enhances the tissue regeneration in vivo, suggesting that the biomaterial modification could play an important role in tissue engineering. In this study we have followed a biomimetic strategy where differentiated human bone marrow stromal cells built their extracellular matrix onto gelatin cryogel scaffolds. In comparison with control conditions without differentiation medium, the use of a differentiation medium increased, in vitro, the coating of gelatin cryogel with bone proteins (decorin, osteocalcin, osteopontin, type-I collagen, and type-III collagen). The differentiation medium aimed at obtaining a better in vitro modification of gelatin cryogel in terms of cell colonization and coating with osteogenic signals, like bone matrix proteins. The modified biomaterial could be used, in clinical applications, as an implant for bone repair.
In the present work, porous gelatin scaffolds were prepared by cryogenic treatment of a chemicall... more In the present work, porous gelatin scaffolds were prepared by cryogenic treatment of a chemically cross-linked gelatin hydrogel, followed by removal of the ice crystals formed through lyophilization. This technique often leads to porous gels with a less porous skin. A simple method has been developed to solve this problem. The present study demonstrates that the hydrogel pore size decreased with an increasing gelatin concentration and with an increasing cooling rate of the gelatin hydrogel. Variation of the cryogenic parameters applied also enabled us to develop scaffolds with different pore morphologies (spherical versus transversal channel-like pores). In our opinion, this is the first paper in which temperature gradients during controlled cryogenic treatment were applied to induce a pore size gradient in gelatin hydrogels. With a newly designed cryo-unit, temperature gradients of 10 and 30°C were implemented during the freezing step, resulting in scaffolds with average pore diameters of, respectively, (116 and (330 µm. In both cases, the porosity and pore size decreased gradually through the scaffolds. Pore size and structure analysis of the matrices was accomplished through a combination of microcomputed tomography using different software packages (µCTanalySIS and Octopus), scanning electron microscopy analysis, and helium pycnometry.
To progress the fields of tissue engineering (TE) and regenerative medicine, development of quant... more To progress the fields of tissue engineering (TE) and regenerative medicine, development of quantitative methods for non-invasive three dimensional characterization of engineered constructs (i.e. cells/tissue combined with scaffolds) becomes essential. In this study, we have defined the most optimal staining conditions for contrast-enhanced nanofocus computed tomography for three dimensional visualization and quantitative analysis of in vitro engineered neo-tissue (i.e. extracellular matrix containing cells) in perfusion bioreactordeveloped Ti6Al4V constructs. A fractional factorial 'design of experiments' approach was used to elucidate the influence of the staining time and concentration of two contrast agents (Hexabrix and phosphotungstic acid) and the neo-tissue volume on the image contrast and dataset quality. Additionally, the neo-tissue shrinkage that was induced by phosphotungstic acid staining was quantified to determine the operating window within which this contrast agent can be accurately applied. For Hexabrix the staining concentration was the main parameter influencing image contrast and dataset quality. Using phosphotungstic acid the staining concentration had a significant influence on the image contrast while both staining concentration and neo-tissue volume had an influence on the dataset quality. The use of high concentrations of phosphotungstic acid did however introduce significant shrinkage of the neo-tissue indicating that, despite sub-optimal image contrast, low concentrations of this staining agent should be used to enable quantitative analysis. To conclude, design of experiments allowed us to define the most optimal staining conditions for PLOS ONE |
Journal of tissue engineering and regenerative medicine, Jan 15, 2015
Porous biodegradable scaffolds represent promising candidates for tissue-engineering applications... more Porous biodegradable scaffolds represent promising candidates for tissue-engineering applications because of their capability to be preseeded with cells. We report an uncrosslinked chitosan scaffold designed with the aim of inducing and supporting enzyme-mediated formation of apatite minerals in the absence of osteogenic growth factors. To realize this, natural enzyme alkaline phosphatase (ALP) was incorporated into uncrosslinked chitosan scaffolds. The uncrosslinked chitosan makes available amine and alcohol functionalities to enhance the biomineralization process. The physicochemical findings revealed homogeneous mineralization, with the phase structure of the formed minerals resembling that of apatite at low mineral concentrations, and similar to dicalcium phosphate dihydrate (DCPD) with increasing ALP content. The MC3T3 cell activity clearly showed that the mineralization of the chitosan scaffolds was effective in improving cellular adhesion, proliferation and colonization. Copy...
ABSTRACT Superabsorbent polymers (SAPs) have already found their way in many applications. These ... more ABSTRACT Superabsorbent polymers (SAPs) have already found their way in many applications. These ‘smart’ polymers undergo major characteristic changes by small environmental variations. In the present work, copolymer networks composed of acrylic acid, acrylamide and N,N′-methylenebisacrylamide have been synthesized using free radical precipitation polymerization. The polymers obtained have been characterized for their chemical structure, moisture (de)sorption and swelling behaviour using, respectively, attenuated total reflectance-infrared spectroscopy, high-resolution magic-angle spinning NMR spectroscopy, dynamic vapour sorption and swelling studies. The results indicated a remarkable moisture uptake capacity at high relative humidities of more than 90 % the original polymer weight with a negligible hysteresis. The latter implies that the SAPs developed are very promising water reservoir candidates, which become useful in concrete-related applications. Furthermore, the swelling data revealed that polymers with a low cross-linking density result in materials with superabsorbent properties. In addition, these SAPs show a pH-dependent swelling behaviour up to 450 times their original weight at pH 12.
In recent years a number of experimental and simulation studies of adsorption of water in pores h... more In recent years a number of experimental and simulation studies of adsorption of water in pores have appeared in the literature [1]. In this regard, the understanding and modeling of water vapour isotherms of activated carbons has been extensively researched, although the mechanism of water adsorption is not yet fully understood and is still object of discussion. The objective of this investigation is to elucidate if some of the previously proposed models for water adsorption in carbon materials have a wider range of application, enabling their use with other kind of materials, such as for example concrete. Evaporable water content evolution in concrete with time may have an internal origin (the so-called self desiccation) due to cement hydration or/and an external origin (exchanges with the environment, according to weathering conditions). It generates, respectively, early-age shrinkage and delayed deformations, along with associated cracking. This shows that water solely is likely...
The biggest problem in concrete are cracks occurring due to the relatively low tensile strength. ... more The biggest problem in concrete are cracks occurring due to the relatively low tensile strength. These cracks can generate an entrance for harmful compounds which are dissolved in fluids and gases and endanger the durability of concrete. The cost for crack repair is very high. Instead, inserting a polymer during concrete mixing can create a crack-sealing material. Using a hydrogel will help to heal cracks as soon as they occur, without any external interference. Fresh cement pore solution has a pH value of 12.8, but when a crack occurs, the pH lowers to 9 - 10 or even lower according to the environment of the application. At this lower pH value, the swelling degree of the inserted hydrogel must be high enough to fill up the crack. A swelling capacity curve was made over the entire pH-range (pH 1-13). The hydrogel gave a high swelling degree (over 450 times its own weight) at these pH values and may therefore be useful to use in concrete. The added amount of hydrogel was chosen at 0....
A good understanding of the nano-pore structure gives insight in several concrete properties like... more A good understanding of the nano-pore structure gives insight in several concrete properties like compressive strength, permeability and durability aspects. Dynamic water vapour sorption tests may be used to study this porosity, but the technique is difficult to interpret as the microstructure is very sensitive to stress, drying and rehydration due to humidity exposure. The removal of interlayer water held by gel pores in C-S-H or chemically bound water can also cause considerable microstructural shrinkage. As all drying techniques more or less dehydrate C-S-H and ettringite, they cause a restructuration of the C-S-H, changing the C-S-H in denser ones. Several drying techniques were studied. These include: no-drying, freeze-drying, oven-drying at 40°C and 105°C, air-drying in the presence of silica gel (20±2°C), vacuum-drying (20±2°C), and the solvent-exchange-method in methanol and isopropanol followed by vacuum-drying (20±2°C). The effect of these various drying techniques on the ...
International journal of immunopathology and pharmacology
Bone tissue engineering typically uses biomaterial scaffolds, osteoblasts or cells that can becom... more Bone tissue engineering typically uses biomaterial scaffolds, osteoblasts or cells that can become osteoblasts, and biophysical stimulations to promote cell attachment and differentiation. In this study, we investigated the effects of an electromagnetic wave on mesenchymal stromal cells isolated from the bone marrow and seeded upon gelatin cryogel disks. In comparison with control conditions without electromagnetic stimulus, the electromagnetic treatment (magnetic field, 2 mT; frequency, 75 Hz) increased the cell proliferation and differentiation and enhanced the biomaterial surface coating with bone extracellular matrix proteins. Using this tissue-engineering approach, the gelatin biomaterial, coated with differentiated cells and their extracellular matrix proteins, may be used in clinical applications as an implant for bone defect repair.
Experimental biology and medicine (Maywood, N.J.), Jan 10, 2014
Continuous glucose monitoring (CGM) is crucial in diabetic care. Long-term CGM systems however re... more Continuous glucose monitoring (CGM) is crucial in diabetic care. Long-term CGM systems however require an accurate sensor as well as a suitable measuring environment. Since large intravenous sensors are not feasible, measuring inside the interstitial fluid is considered the best alternative. This option, unfortunately, has the drawback of a lag time with blood glucose values. A good strategy to circumvent this is to enhance tissue integration and enrich the peri-implant vasculature. Implants of different optically transparent biomaterials (poly(methyl-methacrylate) [PMMA] and poly(dimethylsiloxane) [PDMS]) - enabling glucose monitoring in the near-infrared (NIR) spectrum - were surface-treated and subsequently implanted in goats at various implantation sites for up to 3 months. The overall in vivo biocompatibility, tissue integration, and vascularization at close proximity of the surfaces of these materials were assessed. Histological screening showed similar tissue reactions indepe...
European journal of pharmaceutical sciences : official journal of the European Federation for Pharmaceutical Sciences, 2003
We report here the physicochemical and biological evaluation of a series of polymethacrylates wit... more We report here the physicochemical and biological evaluation of a series of polymethacrylates with side groups of different pK(a) values, such as tertiary amines, pyridine groups, acid functions and imidazole groups as synthetic vectors for gene delivery. The ability of the different polymers to condense DNA was studied by ethidium bromide exclusion tests and agarose gel electrophoresis. The results show that all polymers are able to condense DNA. Both the molecular weight and the chemical composition of the polymers have an influence on the DNA condensation process. Furthermore, the biological properties of the polymer-DNA complexes were investigated, including their haemolytic activity, cytotoxicity and in vitro transfection efficiency. Complexes based on polymers containing only tertiary amines, have a transfection efficiency similar to that of poly(ethyleneimine) (PEI). Polymers containing pyridine groups have a reduced transfection efficiency compared to polymers containing ter...
Biomedical Foams for Tissue Engineering Applications, 2014
ABSTRACT In the present review, the state-of-the-art of porous hydrogel foams will be described a... more ABSTRACT In the present review, the state-of-the-art of porous hydrogel foams will be described and emphasis will be made on their relevance for biomedical applications and more specifically, tissue repair. The description aims at emphasizing both some novel aspects as well as the versatility of hydrogel foams. In addition, an overview of some general hydrogel aspects will be given. Next, a section will deal with natural polymers commonly used and suitable for hydrogel foam development and their respective tissue regeneration applications, followed by a description on advanced technologies applied to design and characterize novel hydrogel foams.
Polymers are commonly used in industry for packaging applications and as protective coatings but ... more Polymers are commonly used in industry for packaging applications and as protective coatings but are sometimes unsuitable to use due to their low surface energies. For these latter applications, surface modification is usually necessary to improve wettability, printability and adhesive properties. In the past decades, plasma surface treatment of polymers has been extensively studied and different treatment conditions have been
In the present work, we report on the biofunctionalisation of silanised Ti-surfaces with gelatin.... more In the present work, we report on the biofunctionalisation of silanised Ti-surfaces with gelatin. In recent years, a large number of papers have been published about the silanisation of different substrates including Ti-surfaces for biomedical applications. However, a comparative study evaluating the effects of different pre-treatment methods (cleaning and/or oxidation) and the efficiency of different silanisation reactions has to our information not yet been published. Since a clean and reproducible surface is required for studying structure-property relations, all Ti-surfaces were subjected to a three step procedure including a cleaning step, an oxidation step and a silanisation step. XPS analysis and contact angle measurements revealed that the pre-treatment of the Ti samples (cleaning + oxidation) had a drastic effect both on the surface composition and its wettability. A detailed study on the effect of different silanisation parameters indicated that the siloxane concentration, the siloxane type, the solvent and a catalyst affect the coupling efficiency of siloxanes to Ti-surfaces. Stability studies revealed a dependency between the siloxane type and the stability of the siloxane coating against hydrolytic cleavage from a Ti-surface. Since Ti-surfaces modified with a methacrylate containing silane possessed the highest hydrolytic stability, these surfaces were selected for the subsequent immobilisation of methacrylamide-modified gelatin via high energy irradiation induced cross-linking. The present work clearly demonstrates the need of a proper reaction strategy for immobilising ligands on Ti-surfaces.
Hydrogels of biocompatible calcium-crosslinkable polysaccharide gellan gum (GG) were enriched wit... more Hydrogels of biocompatible calcium-crosslinkable polysaccharide gellan gum (GG) were enriched with bioglass particles to enhance (i) mineralization with calcium phosphate (CaP); (ii) antibacterial properties and (iii) growth of bone-forming cells for future bone regeneration applications.
Photonics Packaging, Integration, and Interconnects Ix, 2009
We present a concept for an artificial optical skin, a flexible foil in which a novel type of opt... more We present a concept for an artificial optical skin, a flexible foil in which a novel type of optical force sensing elements is integrated. The principle relies on the change in coupling between two arrays of crossing polymer waveguides separated by a thin layer of soft silicone. ...
Biomaterials have been widely used in reconstructive bone surgery to heal critical-size long bone... more Biomaterials have been widely used in reconstructive bone surgery to heal critical-size long bone defects due to trauma, tumor resection, and tissue degeneration. In particular, gelatin cryogel scaffolds are promising new biomaterials owing to their biocompatibility; in addition, the in vitro modification of biomaterials with osteogenic signals enhances the tissue regeneration in vivo, suggesting that the biomaterial modification could play an important role in tissue engineering. In this study we have followed a biomimetic strategy where differentiated human bone marrow stromal cells built their extracellular matrix onto gelatin cryogel scaffolds. In comparison with control conditions without differentiation medium, the use of a differentiation medium increased, in vitro, the coating of gelatin cryogel with bone proteins (decorin, osteocalcin, osteopontin, type-I collagen, and type-III collagen). The differentiation medium aimed at obtaining a better in vitro modification of gelatin cryogel in terms of cell colonization and coating with osteogenic signals, like bone matrix proteins. The modified biomaterial could be used, in clinical applications, as an implant for bone repair.
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Papers by Peter Dubruel