Time-accurate, fully 3D numerical simulations and particle image velocity laboratory experiments are carried out for flow through a fully open bileaflet mechanical heart valve under steady (nonpulsatile) inflow conditions. Flows at two different Reynolds numbers, one in the laminar regime and the other turbulent (near-peak systole flow rate), are investigated. A direct numerical simulation is carried out for the laminar flow case while the turbulent flow is investigated with two different unsteady statistical turbulence modeling approaches, unsteady Reynolds-averaged Navier-Stokes (URANS) and detached-eddy simulation (DES) approach. For both the laminar and turbulent cases the computed mean velocity profiles are in good overall agreement with the measurements. For the turbulent simulations, however, the comparisons with the measurements demonstrate clearly the superiority of the DES approach and underscore its potential as a powerful modeling tool of cardiovascular flows at physiological conditions. The study reveals numerous previously unknown features of the flow.

Advances in material science and innovative medical technologies have allowed the development of less invasive interventional procedures for deploying implant devices, including scaffolds for cardiac tissue engineering. Biodegradable materials (e.g., resorbable polymers) are employed in devices that are only needed for a transient period. In the case of coronary stents, the device is only required for 6–8 months before positive remodelling takes place. Hence, biodegradable polymeric stents have been considered to promote this positive remodelling and eliminate the issue of permanent caging of the vessel. In tissue engineering, the role of the scaffold is to support favourable cell-scaffold interaction to stimulate formation of functional tissue. The ideal outcome is for the cells to produce their own extracellular matrix over time and eventually replace the implanted scaffold or tissue engineered construct. Synthetic biodegradable polymers are the favoured candidates as scaffolds, because their degradation rates can be manipulated over a broad time scale, and they may be functionalised easily. This review presents an overview of coronary heart disease, the limitations of current interventions and how biomaterials can be used to potentially circumvent these shortcomings in bioresorbable stents, vascular grafts and cardiac patches. The material specifications, type of polymers used, current progress and future challenges for each application will be discussed in this manuscript.

Small interfering RNAs (siRNAs) silence the expression of specific target genes by mediating RNA interference (RNAi) in mammalian cells. siRNAs have not only been widely used as a valuable tool for functional genomics research, but they also have demonstrated great potential in biomedical therapeutic applications for diseases caused by abnormal gene overexpression or mutation. One of the most important issues to overcome before full clinical application is the development of effective administration methods for siRNAs to the target tissue or cells in vivo, which is highly dependent on the delivery system. Currently, there are two major kinds of in vivo delivery systems: viral or nonviral. As one of the nonviral carrier systems, nanoparticles, combinations of liposomes and cationic polymer complexes, have exhibited improved in vivo stability, target specificity, and cell/tissue uptake and internalization of the encapsulated RNAi oligos, which result in more effective silencing with less cellular toxicity and immune stimulation. This review will discuss the latest advancements in nanoparticle-mediated RNAi delivery systems, including nano-materials, preparation, and characteristics. In conjunction, the clinical trial cases related to the nanoparticle-siRNA complexes will be highlighted. The safety issues of nanoparticles used in vivo will also be mentioned. Finally, this review will summarize the perspectives for future applications of nanoparticle-mediated RNAi delivery systems.