The effect of hydrostatic pressure on proteoglycan production in articular cartilage in vitro: a meta-analysis.

OBJECTIVE: In previous research the use of hydrostatic pressure (HP) has been applied to enhance the formation of engineered cartilage, through the up-regulation of proteoglycan synthesis by mechanotransduction. However, the HP stimulation approach has been shown to vary between studies with a wide disparity in results, including anabolic, catabolic and non-responsive outcomes. To this end, a meta-analysis of HP publications using 3D cultured chondrocytes was performed to elucidate the key experiment factors involved in achieving a mechanotransducive response. DESIGN: The effects of different HP regimes on proteoglycan production were investigated based on the following factors: static vs dynamic application, pressure magnitude, and experiment duration. Meta-analysis was performed on raw data taken from 11 publications which employed either aggrecan gene expression analysis or dimethyl methylene blue colorimetric assay. The measure of effect was calculated based on mean difference using a random effects model. RESULTS: Analysis revealed that a significant anabolic response was most likely achieved when the following factors were employed; a static HP application, a magnitude within the mid-high physiological range of cartilage (≤5-10 MPa) and a study duration of ≥2 weeks. CONCLUSIONS: Thus, we propose that the selection of HP experiment factors can have a significant influence on engineered cartilage development, and that the results of this meta-analysis can be used as a basis for the planning of future HP experiments.

Three-Dimensional-Printed Electrochemical Sensor for Simultaneous Dual Monitoring of Serotonin Overflow and Circular Muscle Contraction.

Serotonin (5-HT) is a key signaling molecule within the mucosal epithelium of the intestinal wall and has been shown to be an important modulator of motility. At present, no single approach has been established for simultaneous dual measurement of 5-HT overflow and circular muscle contraction. We developed a 3D-printed carbon black/polylactic acid (PLA) electrochemical sensor, which had a geometry suitable for ex vivo measurement in the anorectum. The device was characterized for sensitivity and stability for 5-HT measurements as well as suitability for accurate tracking of anorectal contractions. The 3D-printed electrochemical sensor had a linear range in physiological concentrations of 5-HT (1-10 µM) present within the intestinal tract and a limit of detection of 540 nM. The sensor was stable for 5-HT measurement following ex vivo tissue measurements. There was a signficant correlation in the amplitude and duration of individual contractions when comparing the measurements using an isometric force transducer and 3D-printed electrochemical sensor. Finally, in the presence of 1 µM fluoxetine, the sensor was able to monitor a reduction in contractility as well as an increase in 5-HT overflow as predicted. Overall, the 3D-printed sensor has the ability to conduct dual simultaneous measurements of 5-HT overflow and contractility. This single device will have significant potential for clinical measurements of anorectum function and signaling that can direct therapeutic management of patients with bowel disorders.

Development of thermal models of footwear using finite element analysis.

Thermal comfort is increasingly becoming a crucial factor to be considered in footwear design. The climate inside a shoe is controlled by thermal and moisture conditions and is crucial to attain comfort. Research undertaken has shown that thermal conditions play a dominant role in shoe climate. Development of thermal models that are capable of predicting in-shoe temperature distributions is an effective way forward to undertake extensive parametric studies to assist optimized design. In this paper, two-dimensional and three-dimensional thermal models of in-shoe climate were developed using finite element analysis through commercial code Abaqus. The thermal material properties of the upper shoe, sole, and air were considered. Dry heat flux from the foot was calculated on the basis of typical blood flow in the arteries on the foot. Using the thermal models developed, in-shoe temperatures were predicted to cover various locations for controlled ambient temperatures of 15, 25, and 35 degrees C respectively. The predicted temperatures were compared with multipoint measured temperatures through microsensor technology. Reasonably good correlation was obtained, with averaged errors of 6, 2, and 1.5 per cent, based on the averaged in-shoe temperature for the above three ambient temperatures. The models can be further used to help design shoes with optimized thermal comfort.