Bone marrow and adipose tissue human mesenchymal stem cells were seeded in highly performing 3D gelatin–chitosan hybrid hydrogels of varying chitosan content in the presence of human platelet lysate and evaluated for their proliferation and osteogenic differentiation. Both bone marrow and adipose tissue human mesenchymal stem cells in gelatin–chitosan hybrid hydrogel 1 (chitosan content 8.1%) or gelatin–chitosan hybrid hydrogel 2 (chitosan 14.9%) showed high levels of viability (80%–90%), and their proliferation and osteogenic differentiation was significantly higher with human platelet lysate compared to fetal bovine serum, particularly in gelatin–chitosan hybrid hydrogel 1. Mineralization was detected early, after 21 days of culture, when human platelet lysate was used in the presence of osteogenic stimuli. Proteomic characterization of human platelet lysate highlighted 59 proteins mainly involved in functions related to cell adhesion, cellular repairing mechanisms, and regulation of cell differentiation. In conclusion, the combination of our gelatin–chitosan hybrid hydrogels with hPL represents a promising strategy for bone regenerative medicine using human mesenchymal stem cells.

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This paper describes the design, development, and characterization of two wireless instrumented crutches for gait monitoring in order to provide clinicians quantitative parameters of upper limbs’ contributions during walking. These parameters could be used to teach orthopedic patients to correctly use these supports and minimize problems connected to their usage. These instrumented crutches allow monitoring axial forces and shear forces, tilt angles, and time of impact on the ground in real time. Each crutch is composed of three strain-gauge bridges for measuring axial and shear forces, a conditioning circuit with transmission module, a triaxial accelerometer, a power management circuit, two batteries, and a biofeedback. The data are wirelessly transmitted via Bluetooth without needing any further readout unit, from the crutches to a personal computer, where the data are processed and displayed by a program created in LabVIEW. Each instrumented crutch was tested to assess the response of the accelerometer and the three strain-gauge bridges using a setup designed ad hoc. The mean experimental standard deviation was about 42 mV for axial forces corresponding to about 8 N and about 35 mV for shear forces corresponding to about 4 N. Hysteresis, linearity, and drift were calculated, and the obtained accuracy was about 8–9 N for axial forces and 4–5 N for shear forces. Furthermore, the crutches were tested during a walking activity of ten healthy subjects along a straight path for several trials. These crutches were used for a common analysis usually reported in the literature for weight bearing evaluation. The subjects were monitored performing a nonweight bearing (NWB) and a partial weight bearing (PWB) during a three-point gait. The results showed a mean of 102%±16% for NWB tests and a mean of 19%±14% for 10% PWB tests; these values are in agreement with similar studies in the literature. The simplicity that includes only constitutive strain gauges and a separable circuit board allows the achievement of the objectives of simplicity, ease of use, and noninvasiveness. Therefore, these crutches could be used as a support tool for controlling the use of crutches during walking not only in hospitals but also at home

Implantable medical devices usually require a battery to operate and this can represent a severe restriction. In most cases, the implantable medical devices must be surgically replaced because of the dead batteries; therefore, the longevity of the whole implantable medical device is determined by the battery lifespan. For this reason, researchers have been studying energy harvesting techniques from the human body in order to obtain batteryless implantable medical devices. The human body is a rich source of energy and this energy can be harvested from body heat, breathing, arm motion, leg motion or the motion of other body parts produced during walking or any other activity. In particular, the main human-body energy sources are kinetic energy and thermal energy. This paper reviews the state-of-art in kinetic and thermoelectric energy harvesters for powering implantable medical devices. Kinetic energy harvesters are based on electromagnetic, electrostatic and piezoelectric conversion. The different energy harvesters are analyzed highlighting their sizes, energy or power they produce and their relative applications. As they must be implanted, energy harvesting devices must be limited in size, typically about 1 cm3. The available energy depends on human-body positions; therefore, some positions are more advantageous than others. For example, favorable positions for piezoelectric harvesters are hip, knee and ankle where forces are significant. The energy harvesters here reported produce a power between 6 nW and 7.2 mW; these values are comparable with the supply requirements of the most common implantable medical devices; this demonstrates that energy harvesting techniques is a valid solution to design batteryless implantable medical devices.

a b s t r a c tRecently, inkjet printing technology has received growing attention as a method to produce low-cost large-area electronics, sensors, and antennas on polymer substrates. This technology relies on printing techniques to deposit electrically functional materials onto polymer substrates to fabricate electronic components or sensing elements. In this paper, we applied an inkjet printed technology for the development and characterization of films on a polymer substrate aiming at giving design considerations for the optimization of strain sensors or printed electronics obtained by inkjet printing. Two inks were tested over a polyimide substrate, a water-based conductive polymer, PEDOT:PSS, and a silver nanoparticles ink. Their sensing capabilities were investigated under tensile conditions and various strain histories (strain ramp; cyclic loading-unloading tests; application of constant strain over prolonged time) aiming at highlighting the correlation between electrical response, applied strain, time and mechanical histories. Furthermore, the mechanical viscoelastic response of the substrate was investigated under similar strain histories interpreting the results at the light of the substrate deformational characteristics and evaluating its influence.

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During the last years, scientific research in biotechnology has been reporting a considerable boost forward due to many advances marked in different technological areas. Researchers working in the field of regenerative medicine, mechanobiology and pharmacology have been constantly looking for non-invasive methods able to track tissue development, monitor biological processes and check effectiveness in treatments. The possibility to control cell cultures and quantify their products represents indeed one of the most promising and exciting hurdles. In this perspective, the use of conductive materials able to map cell activity in a three-dimensional environment represents the most interesting approach. The greatest potential of this strategy relies on the possibility to correlate measurable changes in electrical parameters with specific cell cycle events, without affecting their maturation process and considering a physiological-like setting. Up to now, several conductive materials has been identified and validated as possible solutions in scaffold development, but still few works have stressed the possibility to use conductive scaffolds for non-invasive electrical cell monitoring. In this picture, the main objective of this review was to define the state-of-the-art concerning conductive biomaterials to provide researchers with practical guidelines for developing specific applications addressing cell growth and differentiation monitoring. Therefore, a comprehensive review of all the available conductive biomaterials (polymers, carbon-based, and metals) was given in terms of their main electric characteristics and range of applications.