The effect of prior compression tests on the plantar soft tissue compressive and shear properties

An exploratory in-situ dynamic mechanical analysis on the shearing stress-strain mechanism of human plantar soft tissue

A DMA (dynamic mechanical analysis)-like device based on the principle of classical viscoelasticity testing is invented to investigate the in-situ/in-vivo shear-bearing mechanism of plantar soft tissue. Forty-three volunteers were recruited for the shear-strain test in the longitudinal and transverse directions at five anatomical spots on the plantar surface. Several encouraging observations indicated significant variances among different spots and individuals, implying that the outer forefoot surrounding the second, fifth metatarsal head is a more intensive shear-bearing region on the plantar surface compared to the inner forefoot under the first metatarsal head, and drawing the hypothesis of a significant effect of BMI on the shear-bearing property. The speculations agree with our expectations and other previous research. The feasibility and practical value of this novel approach are substantiated, and these intriguing discoveries provide foundational underpinnings for further in-depth investigations.

Modeling, Fabrication and Integration of Wearable Smart Sensors in a Monitoring Platform for Diabetic Patients

The monitoring of some parameters, such as pressure loads, temperature, and glucose level in sweat on the plantar surface, is one of the most promising approaches for evaluating the health state of the diabetic foot and for preventing the onset of inflammatory events later degenerating in ulcerative lesions. This work presents the results of sensors microfabrication, experimental characterization and FEA-based thermal analysis of a 3D foot-insole model, aimed to advance in the development of a fully custom smart multisensory hardware-software monitoring platform for the diabetic foot. In this system, the simultaneous detection of temperature-, pressure- and sweat-based glucose level by means of full custom microfabricated sensors distributed on eight reading points of a smart insole will be possible, and the unit for data acquisition and wireless transmission will be fully integrated into the platform. Finite element analysis simulations, based on an accurate bioheat transfer model of the metabolic response of the foot tissue, demonstrated that subcutaneous inflamed lesions located up to the muscle layer, and ischemic damage located not below the reticular/fat layer, can be successfully detected. The microfabrication processes and preliminary results of functional characterization of flexible piezoelectric pressure sensors and glucose sensors are presented. Full custom pressure sensors generate an electric charge in the range 0-20 pC, proportional to the applied load in the range 0-4 N, with a figure of merit of 4.7 ± 1 GPa. The disposable glucose sensors exhibit a 0-6 mM (0-108 mg/dL) glucose concentration optimized linear response (for sweat-sensing), with a LOD of 3.27 µM (0.058 mg/dL) and a sensitivity of 21 µA/mM cm2 in the PBS solution. The technical prerequisites and experimental sensing performances were assessed, as preliminary step before future integration into a second prototype, based on a full custom smart insole with enhanced sensing functionalities.

Bioengineered stromal cell-derived factor-1α analogue delivered as an angiogenic therapy significantly restores viscoelastic material properties of infarcted cardiac muscle

Ischemic heart disease is a major health problem worldwide, and current therapies fail to address microrevascularization. Previously, our group demonstrated that the sustained release of novel engineered stromal cell-derived factor 1-a analogue (ESA) limits infarct spreading, collagen deposition, improves cardiac function by promoting angiogenesis in the region surrounding the infarct, and restores the tensile properties of infarcted myocardium. In this study, using a well-established rat model of ischemic cardiomyopathy, we describe a novel and innovative method for analyzing the viscoelastic properties of infarcted myocardium. Our results demonstrate that, compared with a saline control group, animals treated with ESA have significantly improved myocardial relaxation rates, while reducing the transition strain, leading to restoration of left ventricular mechanics.