Gelatin functionalization of biomaterial surfaces : strategies for immobilization and visualization

In the present work, the immobilization of gelatin as biopolymer on two types of implantable biomaterials, polyimide and titanium, was compared. Both materials are known for their biocompatibility while lacking cell-interactive behavior. For both materials, a pre-functionalization step was required to enable gelatin immobilization. For the polyimide foils, a reactive succinimidyl ester was introduced first on the surface, followed by covalent grafting of gelatin. For the titanium material, methacrylate groups were first introduced on the Ti surface through a silanization reaction. The applied functionalities enabled the subsequent immobilization of methacrylamide modified gelatin. Both surface modified materials were characterized in depth using atomic force microscopy, static contact angle measurements, confocal fluorescence microscopy, attenuated total reflection infrared spectroscopy and X-ray photo-electron spectroscopy. The results indicated that the strategies elaborated for both material classes are suitable to apply stable gelatin coatings. Interestingly, depending on the material class studied, not all surface analysis techniques are applicable

Multifactorial Optimization of Contrast-Enhanced Nanofocus Computed Tomography for Quantitative Analysis of Neo-Tissue Formation in Tissue Engineering Constructs.

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 bioreactor-developed 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 contrast-enhanced nanofocus computed tomography to be used as a routine screening tool of neo-tissue formation in Ti6Al4V constructs, transforming it into a robust three dimensional quality control methodology

Antiangiogenic versus cytotoxic therapeutic approaches in a mouse model of pancreatic cancer: an experimental study with a multitarget tyrosine kinase inhibitor (sunitinib), gemcitabine and radiotherapy.

This work evaluated SU11248 (sunitinib) as a potential therapeutic agent, alone or in combination with the cytotoxic agent gemcitabine or radiotherapy in a murine model of pancreatic cancer. Panc02 cells were injected subcutaneously into HsdOla/MF1 mice (n=222). Treatment was administered during 1 week: sunitinib (SUN), gemcitabine (GEM), radiotherapy (RT), RT+SUN and GEM+SUN. Mice were sacrificed 14 days after treatment. The effect on microvessel density (MVD) was measured by CD31 staining. Apoptosis (sFAS, cleaved caspase-3) and proangiogenic proteins (VEGF, PlGF, EGF) were measured with ELISA and immunohistochemistry. At day 14, tumors in all groups increased significantly despite treatment. Only after RT/SUN treatment tumor growth slowed down, although the accretion was still significant (P=0.033). Highest levels of apoptosis were seen in GEM/SUN, RT/SUN and RT treated mice (respectively P<0.001, P<0.01 and P<0.05 compared to placebo). MVD was lowest in RT/SUN treated mice [compared to placebo (P<0.05), GEM (P<0.05) and GEM/SUN (P<0.01)]. Highest VEGF levels were seen after RT and RT/SUN treatment [vs. placebo (P<0.001) and vs. other treatments (P<0.01 for all comparisons)]. GEM and SUN in monotherapy lead to an up-regulation of PlGF and EGF, respectively. In conclusion, the combination treatments RT/SUN and GEM/SUN result in a more potent anti-angiogenic and antitumor effect when compared to either treatment alone. Multitargeted angiogenesis inhibitor therapy with sunitinib combined with either radiotherapy or gemcitabine may be a novel approach for human pancreatic cancer.Comparative StudyJournal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

Surface modification of polyimide sheets for regenerative medicine applications

In the present work, two strategies were elaborated to surface-functionalize implantable polyimide sheets. In the first methodology, cross-linkable vinyl groups were introduced on the polyimide surface using aminopropylmethacrylamide. In the second approach, arc:active succinimidyl ester was introduced on the surface of PI. Using the former approach, the aim is to apply a vinyl functionalized biopolymer coating. In the latter approach, any amine containing biopolymer can be immobilized. The foils developed were characterized in depth using a variety of characterization techniques. including atomic force rnicroscopy, static contact angle measurements, and X-ray photoelectron spectroscopy. The results indicated that both modification strategies were successful. The subcutaneous implantation in mice indicated that both modification strategies resulted in biocompatible materials, inducing only limited cellular infiltration to the surrounding tissue