Engineering a Titanium and Polycaprolactone Construct for a Biocompatible Interface Between the Body and Artificial Limb

Mimicking the Tendon Microenvironment to Enhance Skeletal Muscle Adhesion and Longevity in a Functional Microcantilever Platform

Microcantilever platforms are functional models for studying skeletal muscle force dynamics in vitro. However, the contractile force generated by the myotubes can cause them to detach from the cantilevers, especially during long-term experiments, thus impeding the chronic investigations of skeletal muscles for drug efficacy and toxicity. To improve the integration of myotubes with microcantilevers, we drew inspiration from the elastomeric proteins, elastin and resilin, that are present in the animal and insect worlds, respectively. The spring action of these proteins plays a critical role in force dampening in vivo. In animals, elastin is present in the collagenous matrix of the tendon which is the attachment point of muscles to bones. The tendon microenvironment consists of elastin, collagen, and an aqueous jelly-like mass of proteoglycans. In an attempt to mimic this tendon microenvironment, elastin, collagen, heparan sulfate proteoglycan, and hyaluronic acid were deposited on a positively charged silane substrate. This enabled the long-term survival of mechanically active myotubes on glass and silicon microcantilevers for over 28 days. The skeletal muscle cultures were derived from both primary and induced pluripotent stem cell (iPSC)-derived human skeletal muscles. Both types of myoblasts formed myotubes which survived for five weeks. Primary skeletal muscles and iPSC-derived skeletal muscles also showed a similar trend in fatigue index values. Upon integration with the microcantilever system, the primary muscle and iPSC-derived myotubes were tested successively over a one month period, thus paving the way for long-term chronic experiments on these systems for both drug efficacy and toxicity studies.

Progress in organ 3D bioprinting

Three dimensional (3D) printing is a hot topic in today's scientific, technological and commercial areas. It is recognized as the main field which promotes "the Third Industrial Revolution". Recently, human organ 3D bioprinting has been put forward into equity market as a concept stock and attracted a lot of attention. A large number of outstanding scientists have flung themselves into this field and made some remarkable headways. Nevertheless, organ 3D bioprinting is a sophisticated manufacture procedure which needs profound scientific/technological backgrounds/knowledges to accomplish. Especially, large organ 3D bioprinting encounters enormous difficulties and challenges. One of them is to build implantable branched vascular networks in a predefined 3D construct. At present, organ 3D bioprinting still in its infancy and a great deal of work needs to be done. Here we briefly overview some of the achievements of 3D bioprinting technologies in large organ, such as the bone, liver, heart, cartilage and skin, manufacturing.

Anodically Grown Titania Nanotube Induced Cytotoxicity has Genotoxic Origins

Nanoarchitectures of titania (TiO₂) have been widely investigated for a number of medical applications including implants and drug delivery. Although titania is extensively used in the food, drug and cosmetic industries, biocompatibility of nanoscale titania is still under careful scrutiny due to the conflicting reports on its interaction with cellular matter. For an accurate insight, we performed in vitro studies on the response of human dermal fibroblast cells toward pristine titania nanotubes fabricated by anodic oxidation. The nanotubes at low concentrations were seen to induce toxicity to the cells, whereas at higher concentrations the cell vitality remained on par with controls. Further investigations revealed an increase in the G₀ phase cell population depicting that majority of cells were in the resting rather than active phase. Though the mitochondrial set-up did not exhibit any signs of stress, significantly enhanced reactive oxygen species production in the nuclear compartment was noted. The TiO₂ nanotubes were believed to have gained access to the nuclear machinery and caused increased stress leading to genotoxicity. This interesting property of the nanotubes could be utilized to kill cancer cells, especially if the nanotubes are functionalized for a specific target, thus eliminating the need for any chemotherapeutic agents.

Hemodynamics and flow characteristics of a new dialysis port

Renal replacement therapy by hemodialysis requires a permanent vascular access. Implantable ports offer a potential alternative to standard vascular access strategies although their development is limited both in number and extent. We explored the fluid dynamics within two new percutaneous bone-anchored dialysis port prototypes, both by in vitro experiments and computer simulation. The new port is to be fixed to bone and allows the connection of a dialysis machine to a central venous catheter via a built-in valve. We found that the pressure drop induced by the two ports was between 20 and 50 mmHg at 500 ml/min, which is comparable with commercial catheter connectors (15-80 mmHg). We observed the formation of vortices in both geometries, and a shear rate in the physiological range (<10,000s-1), which is lower than maximal shear rates reported in commercial catheters (up to 13,000s-1). A difference in surface shear rate of 15% between the two ports was obtained.

Complications of transcutaneous metal devices

A high incidence of associated infection with the use of transcutaneous metal devices has been widely reported. The aims of this study were: (1) to record the incidence of pin site infection in a Plastic Surgery department, (2) to compare the infection rate in our department with published literature and (3) to identify factors that contribute to infection. A prospective cohort study was performed including all patients presenting to the plastic surgery unit with any type of transcutaneous metal in situ over a 3-month period. Patients and staff were questioned on wound hygiene and whether they had been provided with specific protocols. Our study revealed an infection rate of 24%. Patients and staff were not aware of preventive protocols. From this study, the following conclusions are made: (1) pin site infection is a major problem, and no consensus has been reached on the best way to manage pin sites, (2) there is variable knowledge of pin-site care, (3) there is a need for a clearer definition of pin-site infection and a standardised system of assessment, classification and treatment and (4) there is a need for more innovative technology in pin-site manufacture as studies reveal that the type of material used in the pins does affect infection rates.

Dermal fibroblast and epidermal keratinocyte functionality on titania nanotube arrays

Transcutaneous implants that penetrate through the depth of the skin are used in numerous clinical applications, including prosthetics and dental implants. Favorable interactions between the implant surface and the respective skin layers are critical for the long-term success of transcutaneous implantable devices, hence, it is essential to understand the physiologic response elicited by skin-biomaterial interactions. Recent studies have shown that material surfaces that provide topographic cues at the nanoscale level may provide one possible solution to enhanced biomaterial integration, thus preventing biomaterial rejection. In this study titania nanotube arrays were fabricated using a simple anodization technique as potential interfaces for transcutaneous implantable devices. The in vitro functionality of human dermal fibroblasts and epidermal keratinocytes were evaluated on these nanotube arrays (diameter 70-90 nm, length 1-1.5 μm). Cellular functionality in terms of adhesion, proliferation, orientation, viability, cytoskeletal organization, differentiation and morphology were investigated for up to 4 days in culture using fluorescence microscope imaging, a cell viability assay, indirect immunofluorescence and scanning electron microscopy. The results reported in this study indicate increased dermal fibroblast and decreased epidermal keratinocyte adhesion, proliferation and differentiation on titania nanotube arrays.