ABSTRACT
Non-cement pastes in the form of injectable materials have gained considerable attention in non-invasive regenerative medicine. Different osteoconductive bioceramics have been used as the solid phase of these bone pastes. Mesoporous bioactive glass can be used as an alternative bioceramic for paste preparation because of its osteogenic qualities. Plant-derived osteogenic agents can also be used in paste formulation to improve osteogenesis; however, their side effects on physical and physicochemical properties should be investigated. In this study, nano-bioactive glass powder was synthesized by a sol-gel method, loaded with different amounts of quercetin (0, 100, 150, and 200 µM), an antioxidant flavonoid with osteogenesis capacity. The loaded powder was then homogenized with a mixture of hyaluronic acid and sodium alginate solution to form a paste. We subsequently evaluated the rheological behavior, injectability, washout resistance, and in vitro bioactivity of the quercetin-loaded pastes. The washout resistance was found to be more than 96% after 14 days of immersion in simulated body fluid (SBF) as well as tris-buffered and citric acid-buffered solutions at 25 °C and 37 °C. All pastes exhibited viscoelastic behavior, in which the elastic modulus exceeded the viscous modulus. The pastes displayed shear-thinning behavior, in which viscosity was more influenced by angular frequency when the quercetin content increased. Results indicated that injectability was much improved using quercetin and the injection force was in the range 20-150 N. Following 14 days of SBF soaking, the formation of a nano-structured apatite phase on the surfaces of quercetin-loaded pastes was confirmed through scanning electron microscopy, X-ray diffractometry, and Fourier-transform infrared spectroscopy. Overall, quercetin, an antioxidant flavonoid osteogenic agent, can be loaded onto the nano-bioactive glass/hyaluronic acid/sodium alginate paste system to enhance injectability, rheological properties, and bioactivity.
ABSTRACT
BACKGROUND AND AIM OF THE STUDY: Heart failure is common following aortic valve replacement, and optimal prosthesis function is crucial in this critical clinical setting. The study aim was to investigate the hemodynamic performance and leaflet kinematics of fresh and calcified biological aortic valves in a simulated low stroke volume situation. METHODS: Edwards Perimount Magna (PM) and Medtronic Mosaic Ultra (MU) valves were investigated in an artificial circulation system (130 beats/min, stroke volume 19 ml), and the results compared to normal output (70 beats/min, stroke volume 70 ml). Leaflet kinematics were visualized using a high-speed camera. All valves were exposed to a calcifying solution for six weeks. RESULTS: In the low- and normal-output situation, the PM valve initially demonstrated lower pressure gradients compared to the MU valve (low output 2.4 +/- 0.16 versus 3.4 +/- 0.19 mmHg), but showed a significantly higher closing volume (up to 19% of stroke volume) leading to an increased total energy loss. Regurgitation for the PM valve was explained by progressively longer opening and closing times. The PM valve calcified faster and more severely, leading to increasing gradients and closure volume. CONCLUSION: In the low stroke volume situation pericardial valves demonstrated superior systolic performance, but inferior diastolic performance, leading to a higher total energy loss compared to porcine valves. This finding may have clinical relevance in heart-failure patients.
