The coagulation cascade of blood may be initiated by flow induced platelet activation, which prompts clot formation in prosthetic cardiovascular devices and arterial disease processes. While platelet activation may be induced by biochemical agonists, shear stresses arising from pathological flow patterns enhance the propensity of platelets to activate and initiate the intrinsic pathway of coagulation, leading to thrombosis. Upon activation platelets undergo complex biochemical and morphological changes: organelles are centralized, membrane glycoproteins undergo conformational changes, and adhesive pseudopods are extended. Activated platelets polymerize fibrinogen into a fibrin network that enmeshes red blood cells. Activated platelets also cross-talk and aggregate to form thrombi. Current numerical simulations to model this complex process mostly treat blood as a continuum and solve the Navier-Stokes equations governing blood flow, coupled with diffusion-convection-reaction equations. It requires various complex constitutive relations or simplifying assumptions, and is limited to μm level scales. However, molecular mechanisms governing platelet shape change upon activation and their effect on rheological properties can be in the nm level scales. To address this challenge, a multiscale approach which departs from continuum approaches, may offer an effective means to bridge the gap between macroscopic flow and cellular scales. Molecular dynamics (MD) and dissipative particle dynamics (DPD) methods have been employed in recent years to simulate complex processes at the molecular scales, and various viscous fluids at low-to-high Reynolds numbers at mesoscopic scales. Such particle methods possess important properties at the mesoscopic scale: complex fluids with heterogeneous particles can be modeled, allowing the simulation of processes which are otherwise very difficult to solve by continuum approaches. It is becoming a powerful tool for simulating complex blood flow, red blood cells interactions, and platelet-mediated thrombosis involving platelet activation, aggregation, and adhesion.

Gold nanoparticles, especially nanorods, are emerging as a promising future material to achieve targeted thermal treatment for cancer. The treatment involves nanoparticle-radiation interaction phenomenon to generate the heat confined to a specific region. Obtaining effective treatments requires a more detailed theoretical understanding of this phenomenon. This study evaluates the temperature field in a tumor tissue embedded with gold nanorods, considering a two dimensional domain representing a skin tumor, irradiated with near infrared radiation. The results indicate that it is possible to localize the heat damage to the tumor region while surrounding healthy tissues are spared. The developed numerical model predicts the temperature through various input of the involved process parameters like size, concentration and irradiation intensity.

Magnetic microcapsules are often used as vesicles in targeted drug delivery systems, where focused magnetic field propels the capsules to highly specific locations in tissue. To fully realize this potential it is important to understand the dynamics of magnetically-responsive micrometer sized particles in viscous fluids and the effect of boundaries on particle motion. Furthermore, for practical biomedical applications, it could be useful to create synthetic micrometer-sized vesicles able to perform controlled self-propelled motion. Herein, using computer simulations, we examine the motion of magnetically-responsive synthetic microcapsules that able to crawl along walls in microchannels filled with a viscous fluid. The compliant fluid-filled capsules considered in this study encompass superparamagnetic nanoparticles in their solid shells and, therefore, can be manipulated by alternating magnetic forces.

The activity of proteins and their complexes often involves the conversion of chemical energy (stored or supplied) into mechanical work through conformational changes. Mechanical forces are also crucial for the regulation of the structure and function of cells and tissues. Thus, the shape of eukaryotic cells is the result of cycles of mechano-sensing, mechano-transduction, and mechano-response. Recently developed single-molecule atomic force microscopy (AFM) techniques can be used to manipulate single molecules, both in real time and under physiological conditions, and are ideally suited to directly quantify the forces involved in both intra- and intermolecular protein interactions. In combination with molecular biology and computer simulations, these techniques have been applied to characterize the unfolding and refolding reactions in a variety of proteins, such as titin (an elastic mechano-sensing protein found in muscle) and polycystin-1 (PC1, a mechanosensor found in the kidney).

Passive delivery of arbitrarily shaped particles is one of the main concern for several biomedical applications. Properly designed particles, once administrated at the systemic level and transported by the blood flow along the circulatory system, are expected to improve the efficiency of molecule-based therapy and imaging by increasing the mass fraction of therapeutic molecules and tracers that are able to reach their targets. To this purpose different kinds of particle have been presented in the literature, with different composition and chemico-physical properties. The prediction of the transport dynamics of one or more particles (bolus) in a blood vessel becomes of primary importance, the main parameters involved in the phenomenon being: (a) dimension and shape of the particle; (b) Reynolds number based on the flow rate and diameter of the vessel; (c) density of the particle; (d) number of particles in the bolus. The development of suitable computational techniques able to predict such a complex dynamics could help and speed-up the design process, shedding some light onto the basic mechanism of the phenomena of interest.

Knowledge of mechanical properties of bones is important for the designing of bone replacements and implants as well as the research of bone diseases such as osteoporosis. However, bone, especially trabecular bone, is a highly anisotropic and heterogeneous living tissue. Micro-computed-tomography (micro-CT) and three-dimensional ultrasound imaging techniques are valuable tools for nondestructive investigation of three-dimensional trabecular bone architecture. From a reconstruction of trabecular bone, a numerical model such as finite element (FE) model can be generated. Using this FE model to simulate compression test, and comparing the simulation results to the results from real mechanical test of the same specimen, the relationship between the observed mechanical behaviors and the microstructure can be established.

We present a numerical model to mechanically characterise real and Monte-Carlo microstructures of human cortical bone. Femoral mid-shaft human bone microstructures are specific to each individual and exhibit unique morphological and mechanical properties. Real microstructures of female bone samples are explicitly reconstructed using a finite element model. Patient-dependent statistically equivalent models are built from natural morphological parameters measured under reflected light microscopy (RLM) and back-scattered electron microscopy (BSEM). The micro mechanical properties are provided by nanoindentations and microextensometry. The morphological and mechanical characteristics are incorporated into the model to mimic bone micro-scale heterogeneity. The overall stiffness of the microstructure is calculated for a distribution of samples. The effects of the variations of local parameters on the global stiffness are studied. The evolution of these parameters indicates various aging signs of bone. These results are validated through comparison to experiments to assess fracture risk.