Stability and in vivo safety of gold, titanium nitride and parylene C coatings on NdFeB magnets implanted in muscles towards a new generation of myokinetic prosthetic limbs.

Rare earth magnets are the elective choice when high magnetic field density is required and they are particularly intriguing for inclusion in implantable devices. A safe implantation of NdFeB magnets in muscles would enable the control of limb prostheses using a myokinetic interface i.e., direct control of artificial limb movements by means of magnetic tracking of residual muscle contractions. However, myokinetic prosthesis control is prevented by NdFeB magnets poor biocompatibility, at present. Here we investigated three biocompatible materials as NdFeB magnet coating candidates, namely gold, titanium nitride and parylene C, which have not been analyzed in a systematic way for this purpose, so far. In vitro testing in a tissue-mimicking environment and upon contact with C2C12 myoblasts enabled assessment of the superiority of parylene C coated magnets in terms of corrosion prevention and lack of cytotoxicity. In addition, parylene C coated magnets implanted in rabbit muscles for 28 days confirmed, both locally and systemically, their biocompatibility, with a lack of irritation and toxicity associated with the implant. These findings pave the way towards the development of implantable devices based on permanent magnets and of a new generation of limb prostheses.

Small-caliber vascular grafts based on a piezoelectric nanocomposite elastomer: Mechanical properties and biocompatibility.

The development of small-caliber grafts still represents a challenge in the field of vascular prostheses. Among other factors, the mechanical properties mismatch between natural vessels and artificial devices limits the efficacy of state-of-the-art materials. In this paper, a novel nanocomposite graft with an internal diameter of 6 mm is proposed. The device is obtained through spray deposition using a semi-interpenetrating polymeric network combining poly(ether)urethane and polydimethilsyloxane. The inclusion of BaTiO3 nanoparticles endows the scaffold with piezoelectric properties, which may be exploited in the future to trigger beneficial biological effects. Graft characterization demonstrated a good nanoparticle dispersion and an overall porosity that was not influenced by the presence of nanoparticles. Graft mechanical properties resembled (or even ameliorated) the ones of natural vessels: both doped and non-doped samples showed a Young's modulus of ∼700 kPa in the radial direction and ∼900 kPa in the longitudinal direction, an ultimate tensile strength of ∼1 MPa, a strain to failure of ∼700%, a suture retention force of ∼1.7 N and a flexural rigidity of ∼2.5 × 10-5 N m2. The two grafts differed in terms of burst strength that resulted ∼800 kPa for the control non-doped samples and ∼1100 kPa for the doped ones. The graft doped with BaTiO3 nanoparticles showed a d33 coefficient of 1.91 pm/V, almost double than the non-doped control. The device resulted highly stable, with a mass loss smaller than 2% over 3 months and an excellent biocompatibility.

Soft Hydrogel Zwitterionic Coatings Minimize Fibroblast and Macrophage Adhesion on Polyimide Substrates.

Minimizing the foreign body reaction to polyimide-based implanted devices plays a pivotal role in several biomedical applications. In this work, we propose materials exhibiting nonbiofouling properties and a Young's modulus reflecting that of soft human tissues. We describe the synthesis, characterization, and in vitro validation of poly(carboxybetaine) hydrogel coatings covalently attached to polyimide substrates via a photolabile 4-azidophenyl group, incorporated in poly(carboxybetaine) chains at two concentrations of 1.6 and 3.1 mol %. The presence of coatings was confirmed by attenuated total reflectance Fourier transform infrared spectroscopy. White light interferometry was used to evaluate the coating continuity and thickness (between 3 and 6 µm under dry conditions). Confocal laser scanning microscopy allowed us to quantify the thickness of the swollen hydrogel coatings that ranged between 13 and 32 µm. The different hydrogel formulations resulted in stiffness values ranging from 2 to 19 kPa and led to different fibroblast and macrophage responses in vitro. Both cell types showed a minimum adhesion on the softest hydrogel type. In addition, both the overall macrophage activation and cytotoxicity were observed to be negligible for all of the tested material formulations. These results are a promising starting point toward future advanced implantable systems. In particular, such technology paves the way for novel neural interfaces able to minimize the fibrotic reaction, once implanted in vivo, and to maximize their long-term stability and functionality.

Modulation of gene expression in rat muscle cells following treatment with nanoceria in different gravity regimes.

AIM: Oxidative stress (OS) is strictly associated with senescence/pathogenesis of biological systems. As putative countermeasure to environmental OS, cerium oxide nanoparticles (nanoceria [NC]) were administered to muscle cells on ground and aboard the International Space Station. MATERIALS & METHODS: Transcriptional analyses were conducted through microarray technology and hierarchical clustering. Venn diagram and gene ontology analyses were also performed on selected gene lists. RESULTS: Adaptive responses to both NC administration and to permanence in real microgravity conditions occurred. Enrichment in the biological processes related to aging, body fat development and mesodermal tissue proliferation for NC-treated samples were found. CONCLUSION: Nanotechnology antioxidants promise applications to pathological conditions governed by OS on Earth and in life-hostile environments (low Earth orbit and deep space).

Investigation of drug release modulation from poly(2-oxazoline) micelles through ultrasound.

Among external stimuli used to trigger release of a drug from a polymeric carrier, ultrasound has gained increasing attention due to its non-invasive nature, safety and low cost. Despite this attention, there is only limited knowledge about how materials available for the preparation of drug carriers respond to ultrasound. This study investigates the effect of ultrasound on the release of a hydrophobic drug, dexamethasone, from poly(2-oxazoline)-based micelles. Spontaneous and ultrasound-mediated release of dexamethasone from five types of micelles made of poly(2-oxazoline) block copolymers, composed of hydrophilic poly(2-methyl-2-oxazoline) and hydrophobic poly(2-n-propyl-2-oxazoline) or poly(2-butyl-2-oxazoline-co-2-(3-butenyl)-2-oxazoline), was studied. The release profiles were fitted by zero-order and Ritger-Peppas models. The ultrasound increased the amount of released dexamethasone by 6% to 105% depending on the type of copolymer, the amount of loaded dexamethasone, and the stimulation time point. This study investigates for the first time the interaction between different poly(2-oxazoline)-based micelle formulations and ultrasound waves, quantifying the efficacy of such stimulation in modulating dexamethasone release from these nanocarriers.

Optimal Ultrasound Exposure Conditions for Maximizing C2C12 Muscle Cell Proliferation and Differentiation.

Described here is an in vitro systematic investigation of the effects on C2C12 myoblasts of exposure to finely controlled and repeatable low-intensity pulsed ultrasound of different frequencies (500 kHz, 1 MHz, 3 MHz and 5 MHz) and different intensities (250, 500 and 1000 mW/cm2). An in-house stimulation system and an ultrasound-transparent cell culture well minimized reflections and attenuations, allowing precise control of ultrasound delivery. Results indicated that a 3 MHz stimulation at 1 W/cm2 intensity maximized cell proliferation in comparison with the other exposure conditions and untreated controls. In contrast, cell differentiation and the consequent formation of multinucleated myotubes were maximized by 1 MHz stimulation at 500 mW/cm2 intensity. The highly controlled exposure conditions employed allowed precise correlation of the ultrasound delivery to the bio-effects produced, thus overcoming the inconsistency of some results available in the literature and contributing to the potential of ultrasound treatment for muscle therapy and regeneration.