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Intervertebral disc degeneration is a cell-mediated process that results in the disruption of its function. These changes are difficult to overturn; consequently, early diagnosis is key for the success of any treatment. Clinically, disc degeneration is diagnosed by analyzing morphological changes characteristic of moderate to advanced stages of degeneration. Therefore, there is a need of a reliable biomarker to characterize the compositional and structural integrity of the disc in early stages of degeneration. In this study, shear modulus is proposed as a new biomarker for disc degeneration and a non-invasive method to measure this mechanical property is presented.

While it is firmly established that the mechanical behavior of most biological tissues, including bioengineered tissues, is governed by an underlying network of protein fibers, it is still not clear how best to obtain and utilize structural information to predict mechanical response. In this paper, methods are presented to (1) quantify the fiber arrangement in a tissue from different imaging tools, (2) incorporate that structure into a multiscale model, and (3) solve the model equations to predict both the microscopic and the macroscopic tissue response. In principle these concepts could be applied to any tissue (incorporating the specific tissue components as needed), but for demonstration purposes, the focus of the current work is on cell-compacted collagen gel, a model engineered tissue.

The measurement and control of the flowrate of fluids containing charged macromolecular species and particles is required for a number of applications, such as controlled-drug-delivery and microscale bioreactors. The flowrates that need to be measured for such systems can be as small as microliters per day. We are developing a novel flowmeter, called the separator-analyzer flowmeter (SAF meter), to measure the flow rate of suspensions of charged macromolecules or particles. The SAF meter consists of a channel that splits into two parts and then recombines. A pair of electrodes is positioned before the channel bifurcation. When a DC potential is applied across this pair of electrodes, the charged species are dragged toward one electrode, and the solutions flowing into the two arms downstream differ in the concentration (separator). This difference is inversely proportional to the flowrate of the original mixture. The concentration difference can be measured optically or electrochemically (analyzer). Based on the input to the separator (strength of the applied electric field), and the output from the analyzer (concentrations in the two arms), we can obtain the flowrate of the solution. A milliscale prototype has been fabricated and has been used to measure flowrates from 25-75 /spl mu/l/min.