Semi-analytical solution for the in-vitro sedimentation, diffusion and dosimetry model: surveying the impact of the Peclet number.

Reducing size of the particles to the nanoscale range gives them new physicochemical properties. Several experiments have shown cytotoxic effects for different kinds of engineered nanoparticles (ENP). In-vitro cell culture assays are widely utilized by researchers to evaluate cytotoxic effects of the ENPs. The present paper deals with the "In vitro Sedimentation, Diffusion and Dosimetry (ISDD)" model. This mathematical model uses an advection-diffusion equation with specific assumptions and coefficients to estimate the dose of the particles delivered to the cells monolayer in the culture medium. In the present work, utilizing the generalized integral transform technique (GITT), a semi-analytical solution is developed for the ISDD model. The parameters affecting the ISDD predictions are integrated into two dimensionless numbers, Pe and τ. The Pe number shows the ratio of the convective to the diffusive mass transport rates and τ is a dimensionless time parameter. The quality of the results for an extensive range of Pe and τ numbers is surveyed through application of the developed formula to two series of test cases. A comparison of the results with those obtained from numerical methods shows deviations in the numerical results at high Pe numbers. Applying the developed formula, ISDD predictions for a wide practical range of Pe and τ numbers are calculated and plotted in two- and three-dimensional plots. The curves and formula obtained in this study facilitate the achievement of ISDD predictions with higher accuracies and capabilities for verification of the results.

A survey on the applications of implantable micropump systems in drug delivery.

Systemic drug delivery is the most prevalent form of the drug administration; but it is not possible to extend this approach to all of diseases. In the traditional approaches of drug delivery, the drug spreads through whole of body and this could cause severe side effects in the healthy parts. In addition, in some parts of our body like the eye, ear and brain, there are biological barriers against drug penetration which made drug delivery to these organs as a challenging work. Micropumps are one of the MEMS based devices with great capabilities in controlled drug administration. The most prevalent application of micropumps in drug delivery is known as continuous subcutaneous insulin infusion (CSII) for diabetic patients; but our study showed that there are some other ongoing investigations to extend application of micropumps in new treatment methods for some incurred diseases.

Verification of the mechanostat theory in mandible remodeling after tooth extraction: animal study and numerical modeling.

Bone tissue is capable of remodeling in response to environmental and physiological conditions. Mechanical loading is thought to be one of the most important environmental factors, affecting bone status. Mechanostat theory, which classifies bone behavior on the basis of the mechanical strain, has been vastly applied in cases of long bones. The present study surveyed the applicability of mechanostat theory in interpretation and anticipation of structural changes of the mandible due to tooth extraction, through experimental measurements and numerical modeling. The mandibular left first molar tooth of a 2-year-old male mongrel dog was extracted. Computed tomography (CT) images of the mandible were taken before, immediately after, and 1 year after extraction. Finite element models were constructed from the CT images and analyzed to evaluate the von Mises strain distribution within the mandible, specifically near the extraction site. Marked resorption around the extraction site and significant height reductions in the buccal and lingual ridges around the socket were observed one year after tooth removal. The deep socket made by extraction was filled and replaced by a smooth surface through bone remodeling in response to masticatory loading. Resultant strain analyses revealed a noticeable decline in strain level around the socket after tooth extraction, which activated bone remodeling according to mechanostat theory. At 1-year post-extraction, the strain magnitudes had increased significantly to near pre-extraction values. Alterations in the strain magnitudes along the mesio-distal axis were quantified for each stage and compared with the Mechanostat predefined regions. The FE results were surveyed in combination with the ridge height reductions, along the mesio-distal direction. Strain contours of the post-extraction stages were compatible with predictions by mechanostat theory. These findings validate the ability of mechanostat theory to describe mandible remodeling and predict post-extraction structural changes that occur near the extraction site. These results could be applied in dental treatment planning and implant design.