Abstract: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.

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The present work describes the plasma polymerisation of acrylic acid at atmospheric pressure. The influence of two operating parameters (monomer concentration and discharge power) on the properties of the deposited films is investigated. Results show that at a monomer concentration of 2.5 ppm and a discharge power of 9.5 W, the monomer is only slightly fragmented leading to a high amount of carboxylic acid groups on the deposited films. In contrast, when monomer concentration is decreased or discharge power increased, the incidence of monomer fragmentation processes is higher, leading to a lower amount of carboxylic acid groups on the films. This behaviour can be explained by a higher energy amount available per monomer molecule at low monomer concentrations and high discharge powers and a higher flux of positive ions attacking the surface at high discharge powers. Taking into account these results, it can be concluded that the deposition parameters should be carefully selected in order to preserve the stability of the monomer and thus obtain coatings with high carboxylic acid densities

A joint action of ssDNA aptamers and electrochemistry is a key element in developing successful biosensing platforms, since aptamers are capable of binding various targets with high specificity, and electrochemistry is one of the most sensitive techniques for on-site detections. A continuous search for improved immobilization and sensing strategies of aptamers on transducer surfaces resulted in the strategy presented in this article. The strategy is based on the covalent attachment of gold nanoparticles on the surface of glassy carbon electrodes through sulfhydryl-terminated monolayer, acting as a glue to connect AuNPs on the electrode. The covalently attached gold nanoparticles modified glassy carbon electrodes have been applied for the efficient immobilization of thiolated ssDNA probes, with a surface coverage of about 8.54×10 13 molecules cm −2 which was 7-fold higher than that on the electrochemically deposited gold nanoparticles. Consequently, improved sensitivity, good reproducibility and stability are achieved for electrochemical aptasensor. Combined with the high affinity and specificity of an aptamer, a simple, novel, rapid, sensitive and label-free electrochemical aptasensor was successfully fabricated for ofloxacin (OFL) detection. The linear dynamic range of the sensor varies between 5×10 -8 to 2×10 -5 M OFL with a detection limit of 1×10 -9 M OFL. A potential application in environmental monitoring was demonstrated by using this sensing strategy for the determination of OFL in (experimentally spiked) real samples such as tap water and effluent of sewage treatment plant. The proposed nanoaptasensor combines the advantages of the covalent attachment of neatly arranged AuNPs (enlarged active surface area and strengthened electrochemical signal) and the elimination of labels for the amplified detection of OFL, with the covalent attachment of highly specific aptamers to the surface of the modified electrode.

SummaryIn the present work, the affinity of gelatin type A and B for fibronectin (Fn) was evaluated using surface plasmon resonance, quartz crystal microbalance and radiolabelling experiments.The affinity study was performed on both hydrogel films and 3D scaffolds. The results indicate that type A gelatin films possess a higher affinity for Fn compared to type B gelatin films. This can be explained by a combination of hydrophobic and electrostatic interactions occurring between gelatin type A and Fn. In a second part of the work, the affinity of Fn for a series of porous gelatin scaffolds was also evaluated. The scaffolds were prepared by a cryogenic treatment and subsequent freeze-drying (Van Vlierberghe et al, 2007, Biomacromolecules, 8, 331-337). Type I hydrogels were composed of cone-like pores with decreasing diameter from top (330 µm) to bottom (20-30 µm). Type II scaffolds contained spherical pores with an average diameter of 135 µm. The results of the various scaffolds indicate that the Fn density on the gelatin scaffolds can be easily finetuned by varying the Fn concentration, the gelatin type (A versus B) and various scaffold properties including the pore size and the pore geometry (type I versus type II scaffolds).3