Key Engineering Materials Vol. 583

Abstract: In order to impart both osseointegration and osteoconduction characteristics onto extruded pure polyetheretherketone (PEEK) for use as an artificial bone material, the surface of the PEEK was sputter-coated with a thin bilayer-film consisting of a commercially pure titanium (Ti) layer with a thickness of 90 nm and a hydroxyapatite layer with a thickness of 200 nm derived from simulated body fluid (SBF-HA). A specimen of PEEK coated only with Ti was used in peeling tests to determine the adhesive strength of the interface between the two materials, which was found to be 2.55 ± 0.45 MPa. Tensile tests were also carried out, and it was found that no exfoliation of the Ti film occurred until an ultimate strain of 129% was reached. In a cell culture test using mouse osteoblast on the bilayer-coated PEEK, cell proliferation following 168 h of culturing was 1.3 times higher on the SBF-HA than on synthetic hydroxyapatite, and 2.4 times higher than that on the Ti-coated PEEK. In addition, the proliferation on the Ti-coated PEEK was 2.1 times higher than that on uncoated PEEK.

Abstract: The ability to control the architecture and strength of a bone tissue engineering scaffold is critical to achieve a harmony between the scaffold and the host tissue. The scaffold attempts to mimic the function of the natural extracellular matrix, providing a temporary template for the growth of target tissues. The study of nanocrystalline calcium phosphate physical-chemical characteristics and, thereafter, the possibility to imitate bone mineral for the development of new advanced biomaterials is constantly growing. Scaffolds should have suitable architecture and strength to serve their intended function. Rapid prototyping (RP) technique is applied to tissue engineering to satisfy this need and to create a scaffold directly from the scanned and digitized image of the defect site. Design and construction of complex structures with different shapes and sizes, at micro and macro scale, with fully interconnected pore structure and appropriate mechanical properties are possible by using RP techniques. In this study we present a new biocompatible hybrid scaffold obtained through two different experimental methods and formed by synthetic biomimetic Hydroxyapatite (HA) nanocrystals with high surface reactivity which synergistically interacts with Poly(e-caprolactone) (PCL) and polylactic acid (PLLA). The aim of this pilot study is to test the adhesion and the proliferation of human mesenchymal stem cells (MSC) on both the scaffolds. MSC growth and distribution was evaluated 24 h and 7 days after in-vitro seeding. The results allowed the conclusion that these scaffolds are biocompatible and allow the colonization and proliferation of MSC, therefore, due to their mechanical properties, they are adequate for bone tissue engineering.

Abstract: Different polyurethane sealants were prepared by reacting methylene dyísocyanate and polyadipate of 1,4 butane diol (Mw : 2500 daltons) by using the prepolymer method and different mixtures of rosin and 1,4 butane diol were used as chain extenders. The polyurethanes were characterized by plate-plate rheology, molecular weight distribution, Differential Scanning Calorimetry (DSC), and Laser Confocal Microscopy. The tack of the polyurethanes sealants was obtained by using a modified probe tack method, and their adhesion was obtained by T-peel test of leather/polyurethane sealant/leather joints and by single lap-shear tests of aluminium/polyurethane sealant/aluminium joints. Depending on the rosin content in the chain extender the structure of the polyurethanes was different, i.e. more urethane and urethane-amide hard segments were created up to 50 eq% rosin in the chain extender, and separation of domains was prevailing in the polyurethanes with higher rosin content. Furthermore, the addition of rosin caused an increase in the length of the polymer chains and in the storage modulus (particularly in the polyurethane containing 50 eq% rosin), and decrease in the melting enthalpy. Moreover, the crystallinity of the polyurethanes containing up to 50 eq% rosin showed lower number and smaller spherulites, Finally, the tack at 37 °C and the peel strength increased in the joints made with the polyurethane sealants containing rosin whereas the adhesive shear strength decreased when the polyurethane sealant contained 50 eq% rosin or less.

Abstract: UV light as a tool for surface modification of polymeric biomaterials was considered. In the present work the modification of the surface properties of collagen films, chitosan films and silk fibroin films by UV-irradiation is presented. It was found that the contact angle and the surface free energy were altered by UV-irradiation of biopolymeric films. Moreover, the surface roughness of biopolymeric films was altered by UV-irradiation. UV-irradiation caused the decrease of surface roughness of collagen films, chitosan films and silk fibroin films. KrF laser treatment caused a significant damage of the surface of biopolymeric films and due to the ablation process the micro-foam was formed. As a conclusion one can say that UV light can be used for modification of surface polarity, surface roughness and for 3D formation structure on the biopolymeric films. The modification by UV light can be save method of biomaterials treatment without any chemicals used for alterations of the surface properties.

Abstract: The functionalization of remaining solvent in polymeric membrane pores is presented in this paper leading to new polymeric membrane materials for biomedical applications. Polysulfone membranes were synthesized from aniline by phase inversion and the remaining traces of aniline in membrane pores were transformed by diazotization reaction and coupled with three different organic dyes - Alizarin S, Rhodamine B, and Methyl Orange. The membranes were structurally and morphological characterized and used for different biomedical applications like specific separation of proteins or glucose from synthetic blood solutions.

Abstract: In order to improve the capabilities of zeolites for biomedical applications, new composite materials based on polyaniline in-situ generated inside zeolite pores were developed. As precursors for polyaniline several monomers (like aniline and p-phnylenediamine) were used and different oxidant systems (like ammonium peroxodisulphate/HCl, sodium vanadate/ethylic alcohol) were studied and were used for the separation of different biological interest ions and release of antibiotics.

Abstract: Blends of two polymer, namely chitosan with silk fibroin or partially hydrolysed polyacrylamide (HPAM) were prepared. The surface properties of chitosan/silk fibroin and chitosan/HPAM blended films were investigated using the technique of Atomic Force Microscopy (AFM) and by means of contact angle measurements allowing the calculation of surface free energy. Measurements of the contact angle for diiodomethane (D), and glycerol (G) on the surface of chitosan films and chitosan/silk fibroin films were made and surface free energy was calculated. It was found that chitosan/silk fibroin blend surface is enriched in high surface energy component i.e. silk fibroin. The surface roughness of chitosan, silk fibroin, HPAM, chitosan/silk fibroin and chitosan/HPAM blended films differs with the composition of the blend. Film-forming polymeric blends can be potentially used as biomaterials and cosmetic materials.

Abstract: This study presents some aspects regarding the evaluation of bone-implant interactions using two animal models (rabbit and rat). The proposed implants are new alumina/zirconia bioceramics designed for hard tissue replacement (oral implantology or arthroplasty). The animal selection was made based on the number and size or design of implants to be tested as these factors influence directly the species of animal chosen for this study. The correct placement and stability of the implants were evaluated by radiographic images. SEM micrographs were recorded on the bone/implant area along with the elemental composition of the sheared implant surfaces at different time intervals after the surgery. Calcium/phosphate ratio was considered as an indicative of the surface implant coverage for a successful osseointegration. Histological examination of the bone and bone marrow in direct contact with the implants was performed to detect any immunological or inflammatory responses. Each of the animal species (rat or rabbit) demonstrated unique advantages and disadvantages as a model for demonstrating the response of bone tissue to an implant material. The size and design of the implants also influenced the bone turnover as demonstrated histologically.

Abstract: As one of our main topics of interest within the Department of Anatomy, the usage of biomaterials involved two directions: preparation of anatomical casts by injection and corrosion and preservation of anatomical samples through plastination. For injection we used several substances, such as polyvinyl chloride, with the solvent cyclohexanone, a polyester oil used in furnishing and glass fiber industry and mostly TECHNOVIT 7143, of German production. Another preservation method that includes the usage of biopolymers is plastination, a perfect method for the preservation of perishable biological specimens, especially for soft, putrifiable ones with high water content. The method we applied is the silicone plastination (S10) that addresses to macroscopical samples, such as internal organs (hearts, kidneys) or slices of nervous tissue (brain slices) greater than 10 mm, samples resulted from the dissection process in the Anatomy Department.

Abstract: Throughout history, fractures have been treated by immobilization, traction, and internal fixation. Construction of a stabilization system composed of bone plate and screws combination depends on factors such as type of fracture, biomechanical behavior of stabilization system, and surgical preference. In this study, the influence of plate design, material properties, and screw placement was investigated through the use of Experimental Design and Finite Element simulation. A three dimensional model of the ulna bone was reconstructed from computer tomography images and a simple oblique fracture was simulated. The fracture was stabilized in different modes, using combinations of three different design plates with the material properties of stainless steel and titanium alloy fixed with three, four, and six screws. The biomechanical behavior was compared in terms of equivalent stress and total deformation. Results showed that the fixation mode and plate design have the largest influence on the biomechanical behavior of the bone-plate assembly.