Crumple zone effect of nasal cavity and paranasal sinuses on posterior cranial fossa.

OBJECTIVES/HYPOTHESIS: Examine a protective crumple zone effect of paranasal sinuses and nasal cavity on skull base fractures. STUDY DESIGN: Randomized-control, cadaveric study. METHODS: In the experimental group (n = 4), the nasal cavity and bilateral sinuses of cadavers were obliterated with bone cement, whereas the control group (n = 4) had native sinus architecture. Increasing frontal, glabellar impacts were introduced. Each impact event was examined with a high-speed video camera and sphenoid sinus pressure sensor. After each impact, computed tomography scans were performed and fracture sites were analyzed. RESULTS: The control group with intact sinuses showed statistically longer time duration, during which kinetic energy transfer occurred, and longer sphenoid wall pressure equilibrium time after an impact (P < 0.05). In the experimental group, there were statistically higher fracture incidences of clivus, petrous portion of internal carotid, occipital bone, and foramen magnum (P < 0.05). The type A pattern (n = 6) had anterior skull base failure occurring before posterior skull base failure. Type B pattern (n = 2), seen only in two experimental specimens, is marked by premature posterior skull base collapse occurring before anterior skull base failure with grossly disrupted posterior cranial fossa structures. CONCLUSION: The presence of nasal cavity and paranasal sinuses behaves as a crumple zone to protect the cranial structures, preferentially posterior cranial fossa. Obliteration of the nasal cavity and paranasal sinuses with bone cement significantly increased structural tolerance of the anterior cranial vault to frontal, glabellar impacts at the cost of premature, posterior cranial fossa failure.

Assessing neural stem cell motility using an agarose gel-based microfluidic device.

While microfluidic technology is reaching a new level of maturity for macromolecular assays, cell-based assays are still at an infant stage. This is largely due to the difficulty with which one can create a cell-compatible and steady microenvironment using conventional microfabrication techniques and materials. We address this problem via the introduction of a novel microfabrication material, agarose gel, as the base material for the microfluidic device. Agarose gel is highly malleable, and permeable to gas and nutrients necessary for cell survival, and thus an ideal material for cell-based assays. We have shown previously that agarose gel based devices have been successful in studying bacterial and neutrophil cell migration. In this report, three parallel microfluidic channels are patterned in an agarose gel membrane of about 1mm thickness. Constant flows with media/buffer are maintained in the two side channels using a peristaltic pump. Cells are maintained in the center channel for observation. Since the nutrients and chemicals in the side channels are constantly diffusing from the side to center channel, the chemical environment of the center channel is easily controlled via the flow along the side channels. Using this device, we demonstrate that the movement of neural stem cells can be monitored optically with ease under various chemical conditions, and the experimental results show that the over expression of epidermal growth factor receptors (EGFR) enhances the motility of neural stem cells. Motility of neural stem cells is an important biomarker for assessing cells aggressiveness, thus tumorigenic factor. Deciphering the mechanism underlying NSC motility will yield insight into both disorders of neural development and into brain cancer stem cell invasion.

Computer-aided tissue engineering: application to biomimetic modelling and design of tissue scaffolds.

Computer-aided tissue engineering (CATE) enables many novel approaches in modelling, design and fabrication of complex tissue substitutes with enhanced functionality and improved cell-matrix interactions. Central to CATE is its bio-tissue informatics model that represents tissue biological, biomechanical and biochemical information that serves as a central repository to interface design, simulation and tissue fabrication. The present paper discusses the application of a CATE approach to the biomimetic design of bone tissue scaffold. A general CATE-based process for biomimetic modelling, anatomic reconstruction, computer-assisted-design of tissue scaffold, quantitative-computed-tomography characterization, finite element analysis and freeform extruding deposition for fabrication of scaffold is presented.

Computer-aided tissue engineering: overview, scope and challenges.

Advances in computer-aided technology and its application with biology, engineering and information science to tissue engineering have evolved a new field of computer-aided tissue engineering (CATE). This emerging field encompasses computer-aided design (CAD), image processing, manufacturing and solid free-form fabrication (SFF) for modelling, designing, simulation and manufacturing of biological tissue and organ substitutes. The present Review describes some salient advances in this field, particularly in computer-aided tissue modeling, computer-aided tissue informatics and computer-aided tissue scaffold design and fabrication. Methodologies of development of CATE modelling from high-resolution non-invasive imaging and image-based three-dimensional reconstruction, and various reconstructive techniques for CAD-based tissue modelling generation will be described. The latest development in SFF to tissue engineering and a framework of bio-blueprint modelling for three-dimensional cell and organ printing will also be introduced.