Validation of the small-punch test as a technique for characterizing the mechanical properties of acrylic bone cement

The Effect of Surface Modification of Ti13Zr13Nb Alloy on Adhesion of Antibiotic and Nanosilver-Loaded Bone Cement Coatings Dedicated for Application as Spacers

Spacers, in terms of instruments used in revision surgery for the local treatment of postoperative infection, are usually made of metal rod covered by antibiotic-loaded bone cement. One of the main limitations of this temporary implant is the debonding effect of metal–bone cement interface, leading to aseptic loosening. Material selection, as well as surface treatment, should be evaluated in order to minimize the risk of fraction and improve the implant-cement fixation the appropriate manufacturing. In this study, Ti13Zr13Nb alloys that were prepared by Selective Laser Melting and surface treated were coated with bone cement loaded with either gentamicin or nanosilver, and the effects of such alloy modifications were investigated. The SLM-made specimens of Ti13Zr13Nb were surface treated by sandblasting, etching, or grounding. For each treatment, Scanning Electron Microscope (SEM), contact profilometer, optical tensiometer, and nano-test technique carried out microstructure characterization and surface analysis. The three types of bone cement i.e., pure, containing gentamicin and doped with nanosilver were applied to alloy surfaces and assessed for cement cohesion and its adhesion to the surface by nanoscratch test and pull-off. Next, the inhibition of bacterial growth and cytocompatibility of specimens were investigated by the Bauer-Kirby test and MTS assay respectively. The results of each test were compared to the two control groups, consisting of commercially available Ti13Zr13Nb and untreated SLM-made specimens. The highest adhesion bone cement to the titanium alloy was obtained for specimens with high nanohardness and roughness. However, no explicit relation of adhesion strength with wettability and surface energy of alloy was observed. Sandblasting or etching were the best alloys treatments in terms of the adhesion of either pure or modified bone cements. Antibacterial additives for bone cement affected its properties. Gentamicin and nanosilver allowed for adequate anti-bacterial protection while maintaining the overall biocompatibility of obtained spacers. However, they had different effects on the cement’s adhesive capacity or its own cohesion. Furthermore, the addition of silver nanoparticles improved the nanomechanical properties of bone cements. Surface treatment and method of fabrication of titanium affected surface parameters that had a significant impact on cement-titanium fixation.

Preliminary focus on the mechanical and antibacterial activity of a PMMA-based bone cement loaded with gold nanoparticles

In total knee arthroplasty (TKA) and total hip replacement (THR) the restoration of the normal joint function represents a fundamental feature. A prosthetic joint must be able to provide motions and to transmit functional loads.

As reported in the literature, the stress distribution may be altered in bones after the implantation of a total joint prosthesis. Some scientific works have also correlated uncemented TKA to a progressive decrease of bone density below the tibial component. Antibiotic-loaded bone cements are commonly employed in conjunction with systemic antibiotics to treat infections. Furthermore, nanoparticles with antimicrobial activity have been widely analysed. Accordingly, the current research was focused on a preliminary analysis of the mechanical and antibacterial activity of a PMMA-based bone cement loaded with gold nanoparticles. The obtained results demonstrated that nanocomposite cements with a specific concentration of gold nanoparticles improved the punching performance and antibacterial activity. However, critical aspects were found in the optimization of the nanocomposite bone cement.

•

Evaluation of the in vitro effects of bacterial adhesion and proliferation on modified bone cement samples.

•

Assessment of anti-bacterial and anti-biofilm activities of the nanocomposite bone cement.

•

Analysis of the effect of the inclusion of gold nanoparticles on mechanical performances of a PMMA-based bone cement.

Magnetic poly(ε-caprolactone)/iron-doped hydroxyapatite nanocomposite substrates for advanced bone tissue engineering

In biomedicine, magnetic nanoparticles provide some attractive possibilities because they possess peculiar physical properties that permit their use in a wide range of applications. The concept of magnetic guidance basically spans from drug delivery and hyperthermia treatment of tumours, to tissue engineering, such as magneto-mechanical stimulation/activation of cell constructs and mechanosensitive ion channels, magnetic cell-seeding procedures, and controlled cell proliferation and differentiation. Accordingly, the aim of this study was to develop fully biodegradable and magnetic nanocomposite substrates for bone tissue engineering by embedding iron-doped hydroxyapatite (FeHA) nanoparticles in a poly(ε-caprolactone) (PCL) matrix. X-ray diffraction analyses enabled the demonstration that the phase composition and crystallinity of the magnetic FeHA were not affected by the process used to develop the nanocomposite substrates. The mechanical characterization performed through small punch tests has evidenced that inclusion of 10 per cent by weight of FeHA would represent an effective reinforcement. The inclusion of nanoparticles also improves the hydrophilicity of the substrates as evidenced by the lower values of water contact angle in comparison with those of neat PCL. The results from magnetic measurements confirmed the superparamagnetic character of the nanocomposite substrates, indicated by a very low coercive field, a saturation magnetization strictly proportional to the FeHA content and a strong history dependence in temperature sweeps. Regarding the biological performances, confocal laser scanning microscopy and AlamarBlue assay have provided qualitative and quantitative information on human mesenchymal stem cell adhesion and viability/proliferation, respectively, whereas the obtained ALP/DNA values have shown the ability of the nanocomposite substrates to support osteogenic differentiation.

In vitro testing of chitosan in gentamicin-loaded bone cement: no antimicrobial effect and reduced mechanical performance

BACKGROUND AND PURPOSE

Efforts to prevent infection of arthroplasties, including the use of antibiotic-loaded bone cement, are not always successful. We investigated whether the incorporation of chitosan in gentamicin-loaded bone cement increases antibiotic release, and prevents bacterial adherence and biofilm formation by clinical isolates of Staphylococcus spp. In addition, we performed mechanical and degradation tests.

METHODS

Different amounts of chitosan were added to the powder of the gentamicin-loaded bone cement. Gentamicin release was determined using high-per-formance liquid chromatography mass spectrometry. Bacterial adherence and bacterial biofilm formation were determined using clinical isolates cultured from implants retrieved at revision hip surgery. The mechanical properties were determined as a function of degradation in accordance with ISO and ASTM standards for PMMA bone cement.

RESULTS

The addition of chitosan to bone cement loaded with gentamicin reduced gentamicin release and did not increase the efficacy of the bone cement in preventing bacterial colonization and biofilm formation. Moreover, the mechanical performance of cement containing chitosan was reduced after 28 days of degradation. The compressive and bending strengths were not in compliance with the minimum ISO and ASTM requirements.

INTERPRETATION

Clinically, incorporation of chitosan into gentamicin-loaded bone cement for use in joint replacement surgery has no antimicrobial benefit and the detrimental effect on mechanical properties may have an adverse effect on the longevity of the prosthetic joint.

In vitro study investigating the mechanical properties of acrylic bone cement containing calcium carbonate nanoparticles

A successful total hip replacement has an expected service life of 10-20 years with over 75% of failures due to aseptic loosening which is directly related to cement mantle failure. The aim of the present study was to investigate the addition of nanoparticles of calcium carbonate to acrylic bone cement. It was anticipated that an improvement in mechanical performance of the resultant nanocomposite bone cement would be achieved. A design of experiment approach was adopted to maximise the mechanical properties of the bone cement containing nanoparticles of calcium carbonate and to determine the constituents and preparation methods for which these occur. The selected conditions provided improvements of 21% in energy to maximum load, 10% in elastic modulus, 7% in bending strength and 8% in bending modulus when compared with bone cement without nanoparticles. Although cement containing nanoCaCO(3) coated in sodium citrate also enhanced the energy to maximum load by 28% and the elastic modulus by 14% when compared with control cement, it is not recommended as a factor in the production of nanocomposite bone cement due to reduction in the bending properties of the final bone cement.