Parametric design, fabrication and validation of one-way polymeric valves for artificial sphincters

Abstract The design of artificial sphincters requires an accurate dimensioning of dedicated valves, normally made of polymeric materials. This effort is also interesting for developing fluid and pressure regulating solutions related to other biomedical and non-biomedical fields. In this article we focused on the parametric design of polymeric valves, by taking inspiration from commercially exploited solutions used in the food industry and performing appropriate scaling in order to make them suitable for artificial organs and components. In addition, different materials with diverse mechanical properties were considered, focusing on a low-cost fabrication approach. Finite element model analyses were conducted to simulate the behavior of different valve profiles and to predict the valve opening pressure. Simulation results were validated by comparing them with experimental results, obtained by fabricating and testing different valve types. This polymeric valve parametric analysis may be exploited for the design of artificial sphincters, having the potential to tackle urinary incontinence, a disease that affects about 350 million people worldwide

Magnetic Field-Based Technologies for Lab-on-a-Chip Applications

In the last decades, LOC technologies have represented a real breakthrough in the field of in vitro biochemical and biological analyses. However, the integration of really complex functions in a limited space results extremely challenging and proper working principles should be identified. In this sense, magnetic fields revealed to be extremely promising. Thanks to the exploitation of external magnetic sources and to the integration of magnetic materials, mainly high aspect ratio micro-/nanoparticles, non-contact manipulation of biological and chemical samples can be enabled. In this chapter, magnetic field-based technologies, their basic theory, and main applications in LOC scenario will be described by foreseeing also a deeper interaction/integration with the typical technologies of microrobotics. Attention will be focused on magnetic separation and manipulation, by taking examples coming from traditional LOC devices and from microrobotics

Nanoscaffolds for guided cardiac repair: the new therapeutic challenge of regenerative medicine

Cardiovascular diseases represent the leading cause of death and disability in the world. At the end-stage of heart failure, heart transplantation remains the ultimate option. Therefore, due to the numerous drawbacks associated with this procedure, new alternative strategies to repair the wounded heart are required. Cell therapy is a potential option to regenerate functional myocardial tissue. The characteristics of the ideal cardiac cell therapy include the use of the proper cell type and delivery methods as well as the choice of a suitable biomaterial acting as a cellular vehicle. Since traditional delivery methods are characterized by several counter backs, among which low cell survival, new engineered micro- and nanostructured materials are today extensively studied to provide a good cardiac therapy. In this review, we report the most recent achievements in the field of cell therapy for myocardial infarction treatment and heart regeneration, focusing on the most commonly used cell sources, the traditional approaches used to deliver cells at the damaged site, and a series of novel technologies based on recent advancements of bioengineering, highlighting the tremendous potential that nanoscaffolds have in this framework

PDMS and DLC-coated unidirectional valves for artificial urinary sphincters: Opening performance after 126 days of immersion in urine

In this work, unidirectional valves made of bare polydimethylsiloxane (PDMS) and PDMS provided with a micrometric diamond-like carbon (DLC) coating were fabricated and characterized, in terms of surface properties and opening pressure. The valve performance was also tested over 1250 repeated cycles of opening/closure in water, finding a slight decrease in the opening pressure after such cycles (10%) for the PDMS valves, while almost no variation for the PDMS + DLC ones. The valves were then immersed in urine for 126 days, evaluating the formation of encrustations and the trend of the opening pressure over time. Results showed that PDMS valves were featured by a thin layer of encrustations after 126 days, but the overall encrustation level was much smaller than the one shown by PDMS in static conditions. Furthermore, the opening pressure was almost not affected by such a thin layer of crystals. DLC-coated valves showed even less encrustations at the same time-point, with no significant loss of performance over time, although they were featured by a higher variability. These results suggest that most encrustations can be removed by the mechanical action of the valve during daily openings/closures. Such a self-cleaning behavior with respect to a static condition opens exciting scenarios for the long-term functionality of mobile devices operating in the urinary environment

Tunable mechanical properties of gellan gum/poly (ethylene glycol) diacrylate hydrogels for articular cartilage engineering

Articular cartilage (AC) is a complex multi-layered structure organized into four zones, namely superficial, middle, deep and calcified layers [1]. Its mechanical properties are varying with depth, and the compression modulus of the superficial and middle zone can achieve the value of 0.28 ± 0.16 MPa and 0.73 ± 0.26 MPa, respectively [2]. This paper reports the preliminary results concerning mechanically tunable gellan gum/poly (ethylene glycol) diacrylate hydrogels for mimicking the compression mechanical properties of the first two layers of the AC tissue

Skeletal muscle differentiation of human iPSCs meets bioengineering strategies: perspectives and challenges

Although skeletal muscle repairs itself following small injuries, genetic diseases or severe damages may hamper its ability to do so. Induced pluripotent stem cells (iPSCs) can generate myogenic progenitors, but their use in combination with bioengineering strategies to modulate their phenotype has not been sufficiently investigated. This review highlights the potential of this combination aimed at pushing the boundaries of skeletal muscle tissue engineering. First, the overall organization and the key steps in the myogenic process occurring in vivo are described. Second, transgenic and non-transgenic approaches for the myogenic induction of human iPSCs are compared. Third, technologies to provide cells with biophysical stimuli, biomaterial cues, and biofabrication strategies are discussed in terms of recreating a biomimetic environment and thus helping to engineer a myogenic phenotype. The embryonic development process and the pro-myogenic role of the muscle-resident cell populations in co-cultures are also described, highlighting the possible clinical applications of iPSCs in the skeletal muscle tissue engineering field