V. Dediu

A novel route in bone tissue engineering: Magnetic biomimetic scaffolds

In recent years, interest in tissue engineering and its solutions has increased considerably. In particular, scaffolds have become fundamental tools in bone graft substitution and are used in combination with a variety of bio-agents. However, a long-standing problem in the use of these conventional scaffolds lies in the impossibility of re-loading the scaffold with the bio-agents after implantation. This work introduces the magnetic scaffold as a conceptually new solution. The magnetic scaffold is able, via magnetic driving, to attract and take up in vivo growth factors, stem cells or other bio-agents bound to magnetic particles. The authors succeeded in developing a simple and inexpensive technique able to transform standard commercial scaffolds made of hydroxyapatite and collagen in magnetic scaffolds. This innovative process involves dip-coating of the scaffolds in aqueous ferrofluids containing iron oxide nanoparticles coated with various biopolymers. After dip-coating, the nanoparticles are integrated into the structure of the scaffolds, providing the latter with magnetization values as high as 15 emu g(-)(1) at 10 kOe. These values are suitable for generating magnetic gradients, enabling magnetic guiding in the vicinity and inside the scaffold. The magnetic scaffolds do not suffer from any structural damage during the process, maintaining their specific porosity and shape. Moreover, they do not release magnetic particles under a constant flow of simulated body fluids over a period of 8 days. Finally, preliminary studies indicate the ability of the magnetic scaffolds to support adhesion and proliferation of human bone marrow stem cells in vitro. Hence, this new type of scaffold is a valuable candidate for tissue engineering applications, featuring a novel magnetic guiding option.

Poly(caprolactone) based magnetic scaffolds for bone tissue engineering

Synthetic scaffolds for tissue engineering coupled to stem cells represent a promising approach aiming to promote the regeneration of large defects of damaged tissues or organs. Magnetic nanocomposites formed by a biodegradable poly(caprolactone) (PCL) matrix and superparamagnetic iron doped hydroxyapatite (FeHA) nanoparticles at different PCL/FeHA compositions have been successfully prototyped, layer on layer, through 3D bioplotting. Magnetic measurements, mechanical testing, and imaging were carried out to calibrate both model and technological processing in the magnetized scaffold prototyping. An amount of 10% w/w of magnetic FeHA nanoparticles represents a reinforcement for PCL matrix, however, a reduction of strain at failure is also observed. Energy loss (absorption) measurements under a radio-frequency applied magnetic field were performed in the resulting magnetic scaffolds and very promising heating properties were observed, making them very useful for potential biomedical applications.

Electrically Programmable Magnetoresistance in Multifunctional Organic-Based Spin Valve Devices

5] In this paper we show that an electrically controlled magne-toresistance can be easily achieved in organic devices by com-bining magnetic bistability (spin valve) and electrical memory effects into an interacting multifunctional implementation. Electrical resistive switching effects in organic-based devices have recently received widespread attention

The role of aluminum oxide buffer layer in organic spin-valves performance

The electronic structures of the 8-hydroxyquinoline-aluminum (Alq(3))/Al2O3/Co interfaces were studied by photoelectron spectroscopy. A strong interface dipole was observed, which leads to a reduct ...

A Single-Device Universal Logic Gate Based on a Magnetically Enhanced Memristor

Memristors are one of the most promising candidates for future information and communications technology (ICT) architectures. Two experimental proofs of concept are presented based on the intermixing of spintronic and memristive effects into a single device, a magnetically enhanced memristor (MEM). By exploiting the interaction between the memristance and the giant magnetoresistance (GMR), a universal implication (IMP) logic gate based on a single MEM device is realized.

Understanding the role of tunneling barriers in organic spin valves by hard x-ray photoelectron spectroscopy

We present an ex situ, nondestructive chemical characterization of deeply buried organic-inorganic interfaces using hard x-ray photoelectron spectroscopy. Co/Alq3 and Co/AlOx/Alq3 interfaces were studied in order to determine the role of a thin (1–2 nm) AlOx interdiffusion barrier in organic spin valves. Interfacial Alq3, 15 nm below the surface, exhibits strong sensitivity to the electronic structure of the interfacial region and to the presence of the AlOx. In addition to reducing Co–Alq3 interdiffusion, we find that the barrier prevents charge donation from the Co to the interfacial Alq3, thus preventing the formation of Alq3 anions within the interface region.

Hybrid Interface States and Spin Polarization at Ferromagnetic Metal–Organic Heterojunctions: Interface Engineering for Efficient Spin Injection in Organic Spintronics

Ferromagnetic metal-organic semiconductor (FM-OSC) hybrid interfaces have been shown to play an important role for spin injection in organic spintronics. Here, 11,11,12,12-tetracyanonaptho-2,6-quin ...

A new approach to scaffold fixation by magnetic forces: Application to large osteochondral defects

Scaffold fixation represents one of the most serious challenges in osteochondral defect surgery. Indeed, the fixation should firmly hold the scaffold in the implanted position as well as it should guaranty stable bone/scaffold interface for efficient tissue regeneration. Nonetheless successful results have been achieved for small defect repair, the fixation remains really problematic for large defects, i.e. defects with areas exceeding 2cm(2). This paper advances an innovative magnetic fixation approach based on application of magnetic scaffolds. Finite element modeling was exploited to investigate the fixation efficiency. We considered three magnetic configurations: (1) external permanent magnet ring placed around the leg near the joint; (2) four small permanent magnet pins implanted in the bone underlying the scaffold; (3) four similarly implanted stainless steel pins which magnetization was induced by the external magnet. It was found that for most appropriate magnetic materials and optimized magnet-scaffold positioning all the considered configurations provide a sufficient scaffold fixation. In addition to fixation, we analyzed the pressure induced by magnetic forces at the bone/scaffold interface. Such pressure is known to influence significantly the bone regeneration and could be used for magneto-mechanical stimulation.

Electroluminescence and magnetoresistance of the organic light-emitting diode with a La0.7Sr0.3MnO3 anode

Electroluminescence (EL) with brightness up to 300 cd m2 is observed from organic light-emitting diodes fabricated on oxygen-treated La0.7 Sr0.3 Mn O 3 anodes. An external magnetic field of 150 mT ...

Electrochemical preparation of cobalt tips for scanning tunneling microscopy

Here we describe a straightforward electrochemical method for fabricating sharp cobalt tips. Such tips are particularly useful for those scanning tunneling microscopy (STM) experiments where the focus is on magnetic properties of the surface and the spin polarized (SP) tunneling current is the relevant property, such as in SPSTM and SP scanning tunneling spectroscopy.