Total bacterial disinfection and elimination from the human root canal system are crucial in clinical endodontic procedures [Card et al., 2002; Kakoli et al., 2009]. The current approaches relying on mechanical instrumentation and root canal irrigation and medicaments have demonstrated that eradication of bacteria occurs when the bacteria are in direct contact with the medicaments. However, persistent infection following routine treatments has suggested that bacteria may harbor in the root canal anatomical irregularities and/or deep dentinal tubules, therefore, surface irrigation of medicaments may not be able to reach those regions. Heat treatment has been used for obturation of the root canal in endodontic practice. In this study we hypothesize that as an alternative, surface heating using a System B heating catheter through the root canal surface would be effective for bacterial elimination in the deep dentin. The heat-induced cytotoxic response kills bacteria in the root dentin via heat conduction from the thermal energy incident on the root canal wall. In principle, a high power setting and/or a long heating duration can always achieve sufficient temperature elevations in deep dentin. Yet, the detailed temperature distribution inside the dentin and possible thermal damage to the supporting periodontium are unknown. Therefore, it is of clinical importance to perform and investigate temperature elevations in dentin to provide clinicians with an optimized and effective treatment protocol to minimize unnecessary thermal damage to the surrounding structure.

Convection-enhanced delivery is a means to deliver therapeutic agents directly into brain tissue. Biphasic models have been used to study the concomitant fluid and mass transport that occurs during infusion, however previous studies have been limited by the assumption of linear elasticity of the solid phase [1]. In contrast, nonlinear stress-strain curves have been documented for brain tissue under finite deformation in tension and compression [2, 3].

With recent advances in cell-based medical technologies such as tissue engineering and regenerative medicine, living cells are becoming more and more important as a therapeutic tool in modern medicine. Due to the limited availability of cell sources, effective long-term preservation of living cells is of great importance to the eventual success of these emerging technologies. Cell preservation can be achieved by cooling/freezing the cells to a cryogenic temperature (cryopreservation) and/or drying the cells to preserve at ambient temperature (lyopreservation). Due to the high cost of maintaining and inconvenience of transporting cryopreserved cells, there is an increasing demand for cell lyopreservation.

The liver has a specialized circulation. It is supplied by two main vessels: the hepatic portal vein, carrying nutrient-rich deoxygenated blood, and the hepatic artery, carrying oxygenated blood. The hepatic portal vein supplies up to 80% of the blood. Within the liver, both the portal vein and the hepatic artery undergo a series of successive bifurcations, which end at the portal tracts. Each portal tract contains three vessels: a portal vein, an artery and a bile duct. Blood drains out from the portal tracts into the sinusoidal space and from there into the central veins. The central veins, after a series of converging bifurcations, end at the hepatic veins, which carry blood out of the liver. The sinusoidal space consists of a network of tortuous, interconnected channels called sinusoids. One of the most common and widely accepted descriptions of the primitive units of the liver is the “classic lobule”. A diagram of an idealized arrangement of liver lobules is shown in Figure 1. Each lobule has the shape of a hexagonal prism with a portal tract running along each of the parallel edges and a central vein on the central axis. The remainder of the space is made up of sinusoids.

Maintaining tissue functionality is crucial for successful cryopreservation. However, current understanding of the effects of cryopreservation including those of cryoprotective agents (CPAs) on post-thaw tissue functionality is still very limited. In numerous cryopreservation protocols, CPAs such as dimethyl sulfoxide (DMSO) are commonly used. Different concentrations and combinations of CPAs have been reported to be advantageous in maintaining post-thaw tissue functionality, but the determination of their optimum composition often requires extensive experimental studies due to the lack of understanding of their effects on the biophysics of the tissues during freezing.

Although desiccation preservation offers promise as an alternative method for the preservation of mammalian cells, there has been limited success in achieving survival at very low water content [1]. Osmotic injury is one of the major damage factors during cellular dehydration. During the drying process, cells experience increased extracellular hypertonic environment as a result of evaporation of water. This factor coupled with the limited permeability of cell membranes leads to irreversible cellular damage. In the current study, we have studied the effect of hypertonic osmolality and exposure time on bovine sperm motility. The goal was to develop a theoretical osmotic damage model to predict motility loss during dehydration. Modeling was performed by using a first order rate equation. Motility data from the hypertonic exposure experiments were used to determine the first order reaction parameters and the cumulative osmotic damage (COD), which provided a measure of the extent of osmotic damage. The parameters were then used to predict motility of natural convection desiccation process. Experimental drying data was compared to the predicted data to determine the extent of osmotic damage.

Tissue bioreactors are flow systems able to support cultured cells over time. Consequently the functionality of these in vivo systems require the cells to be provided with the required substrate, nutrient, and O 2 . When a bioreactor is used for liver support, the latter requirement is particularly critical since hepatocyte functionalities are highly dependent on O 2 [1]. So for bioreactor designers, computational models would serve as a powerful tool for predicting O 2 transport dynamics. In the current study, such a model is developed to predict the level of O 2 available to hepatocytes dispersed within a porous collagen substrate, for varying flow conditions. This is carried out by intially verifying the model’s accuracy through experiments conducted using a customized flow device and then extending the model to clarify the sensitivity of O 2 transport through the cellular space with respect to the flow conditions, the cells’ O 2 consumption rates and dissolved O 2 levels in the media.

Knowledge of solute transport in biological tissues is fundamental in order to understand cell nutrition and biosynthetic activity, and to design and fabricate tissue engineered constructs.

Prediction of the threshold of skin burns from radio frequency (RF) current is clinically relevant. The classical studies on skin burns in the 1940s and 1950s [1–3] continue to be the most often cited and utilized framework. In the early 1980s an experimental study of radio frequency (RF) current [4] utilized circular disk electrodes applied to pig skin to create skin burns. A preliminary model of one of the more severe burn experiments has been described [5]. The objective of this study was to inspect the threshold skin damage experiment [3] and apply a recent model for micro-vascular disruption [6].

Systemic lupus erythematosus (SLE) is a chronic inflammatory autoimmune disorder that can affect nearly every organ in the body. A link has been established between abnormal biotransport of apoptotic cell debris and pathogenesis of SLE [1]. Lupus mice are hyper-responsive to immune stimulation and overproduce inflammatory mediators including IL-6, IL-12, and nitric oxide (NO) [2]. Extracellular expression and transport of inflammatory cytokines are thought to be involved with the inhibited clearance of cellular debris [1]. Hsp90 has a prominent role in folding and conformational regulation of several client proteins, including proteins involved with production of inflammatory mediators [3]. Hsp90 readily binds ATP at the amino (N-) terminal domain. This binding event causes a conformational change in Hsp90 making it “clamp down” on its client protein [3]. Geldanamycin (Geld) is a known inhibitor of Hsp90 that out competes ATP binding at the N-terminal. This prevents chaperone capability and ultimately leads to client protein deactivation, destabilization, and degradation [3]. Hsp90 inhibitors have been shown to suppress immune stimulated release of interleukin 6 (IL-6), IL-12, tumor necrosis factor alpha (TNF-α), and nitric oxide (NO) [4].

When a blood vessel is damaged, platelets aggregate together to form a thrombus that seals vascular leakage and promotes healing. The process of thrombosis involves activation of platelets by soluble ligands, adhesion to the wound site, change in shape from a discoidal to a stellate structure, and the attachment of additional platelets onto the nascent clot through adhesive ligand bridges. Once formed, a clot will undergo a retraction in volume that packs platelets together and allows blood flow to recommence. Much attention has been paid to the early phases of thrombosis — adhesion and aggregation — but the process of clot retraction is vital to stabilizing the clot.

Autologous vessels are the gold standard for small-diameter (<6 mm) vascular bypass; however, many patients lack suitable autologous tissues due to diseases or prior vein harvest. As an alternative, synthetic vascular grafts made from bioinert synthetic materials such as polytetrafluoroethylene (PTFE) are currently used in the medical field. The high long-term failure rate of these materials in the replacement of small vessels is known to be associated with the lack of proper signalling events by PTFE to vascular cells causing adverse hemodynamic, inflammatory or coagulatory conditions. Therefore, constant and pressing is the demand for a more biocompatible conduit with structure and function similar to native vessels. For this reason, bioresorbable scaffold constructs which can provide not only proper mechanical support, but also precise molecular cues, are desired (1). In particular, proper degradation kinetics and molecule release profiles are needed to facilitate remodeling and integration process in vivo over the time for long-term patency (2).