Marcin Kaczmarek

EIS Study of SiO2 Oxide Film on 316L Stainless Steel for Cardiac Implants

The correct relationship between implant and tissue environment provides a properly prepared surface of a medical device. The combination of advantages of metal implants with the required biocompatibility is achieved through various methods of surface treatment such as: electrochemical polishing, chemical passivation, preparation of oxide coatings obtained with the sol-gel method. The relatively short history of use of silica layers in biomedical applications transfers into a small amount of literature relating to the electrochemical properties of these layers. Therefore, the authors proposed in the work forming a silica layer of the established technological parameters on surface of the 316L stainless steel. In order to determine the usefulness of this technology electrochemical impedance spectroscopy studies were performed. Furthermore, corrosion resistance tests by means of the potentiodynamic method were also carried out. The obtained results were the basis for optimization of technological conditions for deposition of silica layers on the 316L steel surface.

Novel bioactive polyester scaffolds prepared from unsaturated resins based on isosorbide and succinic acid.

In this study new biodegradable materials obtained by crosslinking poly(3-allyloxy-1,2-propylene succinate) (PSAGE) with oligo(isosorbide maleate) (OMIS) and small amount of methyl methacrylate were investigated. The porous scaffolds were obtained in the presence of a foaming system consisted of calcium carbonate/carboxylic acid mixture, creating in situ porous structure during crosslinking of liquid formulations. The maximum crosslinking temperature and setting time, the cured porous materials morphology as well as the effect of their porosity on mechanical properties and hydrolytic degradation process were evaluated. It was found that the kind of carboxylic acid used in the foaming system influenced compressive strength and compressive modulus of porous scaffolds. The MTS cytotoxicity assay was carried out for OMIS using hFOB1.19 cell line. OMIS resin was found to be non-toxic in wide range of concentrations. On the ground of scanning electron microscopy (SEM) observations and energy X-ray dispersive analysis (EDX) it was found that hydroxyapatite (HA) formation at the scaffolds surfaces within short period of soaking in phosphate buffer solution occurs. After 3h immersion a compact layer of HA was observed at the surface of the samples. The obtained results suggest potential applicability of resulted new porous crosslinked polymeric materials as temporary bone void fillers.

Biomechanical Behaviour of Double Threaded Screw in Tibia Fixation

The aim of the work was assessment of stability of tibia fixation realized with the use of double threaded screw. Biomechanical analysis of the tibia – double threaded screw system was carried our for the implant made of two biomaterials used in bone surgery – Cr-Ni-Mo stainless steel and Ti-6Al-4V alloy. Finite element method was applied to calculate displacements, strains and stresses. The obtained results allowed to work out biomechanical characteristics of the analyzed system. These characteristics can be a basis for selection of degree of strain hardening of the applied metallic biomaterial and optimization of the screw’s geometry.

Characterization of new biodegradable bone cement compositions based on functional polysuccinates and methacrylic anhydride

New biodegradable poly(3-allyloxy-1,2-propylene)succinate-based materials were obtained by cross-linking poly(3-allyloxy-1,2-propylene)succinate (PSAGE) with methyl methacrylate (MMA) and methacrylic anhydride (MAAH). The aim of this study was to examine the influence of MAAH/MMA ratio and incorporation of biphasic calcium phosphate (BCP) filler on the maximum curing temperature, setting time, compressive strength and modulus of the cured materials, as well as on their hydrolytic degradation. The latter was characterized by determination of the weight loss and observation of changes in samples morphology by SEM. The maximum temperature during cross-linking was found to decrease with increasing MAAH content. The setting time was affected strongly by the concentration of double bonds and was rapidly shortened with its increase. The compressive strength and compressive modulus values increased with increasing MAAH/MMA ratio. Moreover, addition of bioactive mineral filler (BCP) improves significantly mechanical properties of these materials. On the other hand, it slows down their hydrolytic degradation.

Evaluation of physicochemical properties of surface modified Ti6Al4V and Ti6Al7Nb alloys used for orthopedic implants.

The paper presents the results of selected functional properties of TiO2 layers deposited by ALD method on the surface of Ti6Al4V and Ti6Al7Nb alloys intended for implants in bone surgery. TiO2 layer was applied at the constant temperature of the ALD process at T=200°C at a variable number of cycles, which resulted in a different layer thickness. Different process cycles of 500, 1250, and 2500 were analyzed. The application of experimental methods (AFM, SEM, wettability, potentiodynamic test, EIS, scratch test, nanohardness and layer thickness) enabled to select the optimal number of cycles, and thus the thickness of the TiO2 layer of the most favorable functional properties. The obtained results clearly showed that regardless of the type of titanium substrate, the TiO2 layer applied in a 2500cycle ALD process has the best physicochemical and electrochemical properties. These properties have major impact on biocompatibility, and therefore the quality of the final product. The information obtained can be useful for manufacturers of medical devices involved in the production of implants used in reconstructive surgery of skeletal system.

Corrosion Resistance of Ti6Al7Nb Alloy after Various Surface Modifications

The influence of surface pretreatment prior to the anode oxidation of Ti6Al7Nb alloy samples on corrosion resistance was presented in the work. The preliminary surface treatments were: grinding, vibration machining, sandblasting and electrochemical polishing. Anodic oxidation process was carried out at different voltages. The final procedure of the surface modification was steam sterilization. The scope of the work included: corrosion resistance study (pitting and crevice) of both non-sterilized and sterilized samples, and samples after 28 days exposure to the Ringer’s solution, concentration evaluation of metal ions releasing from the sterilized surface as well as observations of surface topography. The research revealed a significant influence of surface pretreatment of Ti6Al7Nb alloy, prior to the anode oxidation and steam sterilization, on corrosion resistance.

FEM Analisys of the Expandable Intramedullar Nail

The paper presents results of numerical analysis of new form of expandable intramedullary nail (patent no. P382247) used in stabilization of proximal femur in adults. The obtained results can be used to optimize geometry of implants as well as mechanical properties of metallic biomaterial they are to be made of.

Biomechanical Analysis of Plate for Corrective Osteotomy of Tibia

The aim of the work was assessment of system for corrective osteotomy of tibia (patent no. P382316). The system consisted of the plate of shape adapted to anatomical curvature of bone and the distance block, assembled together with the plate by means of connective screws. Biomechanical analysis of the tibia – plate system was carried our for the implant made of two biomaterials used in bone surgery – stainless steel and Ti-6Al-4V alloy. Finite element method was applied to calculate displacements, strains and stresses. The obtained results allowed to work out biomechanical characteristics of the analyzed system. These characteristics can be a basis for selection of degree of strain hardening of the applied metallic biomaterial and optimization of the plate’s geometry.

Influence of Ultrasound Bone Union Stimulation on Corrosion Resistance of Titanium Alloys

The influence of bone union activation realized with the use of the low-intensity pulsed ultrasound (LIPUS) on degradation of titanium alloys was presented in the work. Ti6Al4V ELI and Ti6Al7Nb alloy samples of modified surface layer were used in the study. The preliminary surface treatments were: grinding, vibration machining, mechanical polishing, sandblasting and electrochemical polishing. The final procedures of the surface modification were anodization and steam sterilization. The scope of the work included the study of pitting corrosion resistance and concentration of metal ions released to the Ringer’s solution. The study was performed for the undeformed and deformed samples subjected to the influence of ultrasound. The reference samples were the samples kept in the solution and not having the impact of ultrasound. On the basis of the study it was found that the conditions for bone union stimulation by low intensity pulsed ultrasound do not initiate pitting corrosion of the titanium alloy samples, although they increase the mass of ions released from the surface to the solution.

Preliminary Studies on the Properties of Novel Polymeric Composite Materials Based on Polysuccinates

This study aimed to prepare novel biodegradable polymeric composites based on poly(3-allyloxy-1,2-propylene) succinate (PSAGE). These composite materials are composed of poly(ester-anhydride) (PEA) microspheres embedded in polyester matrix prepared by crosslinking PSAGE with oligo(1,2-propylene maleate) and methacrylic monomers. Methyl methacrylate and one of hydrophilic oligo(ethylene glycol) dimethacrytes with different length of oligooxyethylene chains were used as polymerizable solvents. Incorporation of microspheres that degrade faster than crosslinked polyester matrices enables formation of porous structure. The obtained materials are liquid before curing and harden in several minutes with moderate exothermic effect. The effect of the composition of polyester matrices and kind of PEA microspheres used on selected properties, such as water sorption, mechanical strength, porosity, and hydrolytic degradation behavior, was investigated. The morphology of the cured composite materials subjected to hydrolytic degradation was evaluated by SEM.