The shielding effect of phospholipidic bilayers on zinc oxide nanocrystals for biomedical applications

Zinc oxide nanocrystals (ZnO NCs), thanks to their unique properties, are receiving much attention for their use in nanomedicine, in particular for therapy against cancer [1]. To be efficiently employed as diagnostic and therapeutic (yet theranostic) tools [2], highly dispersed, stable and non-toxic nanoparticles are required. In the case of ZnO NCs, there is still a lack of knowledge about cytotoxicity mechanisms and stability in the biological context, as well as immunological response and haemocompatible features. Most of these above-mentioned behaviours strongly depends on physico-chemical and surface properties of the nanoparticles. We thus propose a novel approach to stabilize the ZnO NCs in various biological media, focusing on NC aggregation and biodegradation as a function of the surface functionalization. We synthesized bare ZnO NCs, amino-propyl functionalized ones, and lipid bilayer-shielded NCs, and we characterized their morphological, chemical and physical properties. The stability behavior of the three different samples was evaluated, comparing their biodegradation profiles in different media, i.e. organic solvents, water, and different simulated and biological fluids. The studies aim to investigate how the particle surface functionalizations, and thus chemistry and charge, could influence their hydrodynamic size, zeta potential and consequent aggregation and degradation in the different solvents. We demonstrated that bare and amino-functionalized ZnO NCs strongly and rapidly aggregate when suspended in both simulated and biological media. Long-term biodegradation analysis showed small dissolution into potentially cytotoxic Zn-cations, also slightly affecting their crystalline structure. In contrast, high colloidal stability and integrity was retained for lipid-shielded ZnO NCs in all media, rendering them the ideal candidates for further theranostic applications [3]. [1] P. Zhu, Z. Weng, X. Li, X. Liu, S. Wu Adv. Mater. Interfaces 3 (2016) 1500494. [2] E. Lim, T. Kim, S. Paik, S. Haam, Y. Huh, and K. Lee, Chem. Rev. 115 (2015) 327−394. [3] B. Dumontel, M. Canta, H. Engelke, A. Chiodoni, L. Racca, A. Ancona, T. Limongi, G. Canavese and V. Cauda, J. Mater. Chem. B, under review The support from ERC Starting Grant – Project N. 678151 “Trojananohorse” and Compagnia di Sanpaolo are gratefully acknowledged

Fabrication of MEMS Devices by Powder-Filling into DXRL-Formed Molds

We have developed a variety of processes for fabricating components for micro devices based on deep x-ray lithography (DXRL). Although the techniques are applicable to many materials, we have demonstrated them using hard (Nd{sub 2}Fe{sub 14}B) and soft (Ni-Zn ferrite) magnetic materials because of the importance of these materials in magnetic micro-actuators and other devices and because of the difficulty fabricating them by other means. The simplest technique involves pressing a mixture of magnetic powder and a binder into a DXRL-formed mold. In the second technique, powder is pressed into the mold and then sintered to densify. The other two processes involve pressing at high temperature either powder or a dense bulk material into a ceramic mold that was previously made using a DXRL mold. These techniques allow arbitrary 2-dimensional shapes to be made 10 to 1000 micrometers thick with in-plane dimensions as small as 50 micrometers and dimensional tolerances in the micron range. Bonded isotropic Nd{sub 2}Fe{sub 14}B micromagnets made by these processes had an energy product of 7 MGOe

SIMULATION OF SINTERING OF LAYERED STRUCTURES

Abstract -An integrated approach, combining the continuum theory of sintering and Potts model based mesostructure evolution analysis, is used to solve the problem of hi-layered structure sintering. Two types of hi-layered structures are considered: layers of the same material with different initial porosity, and layers of two different materials. The effective sintering stress for the hi-layer powder sintering is derived, both at the meso-and the macroscopic levels. Macroscopic shape distortions and spatial distributions of porosity are determined as functions of the dimensionless specific time of sintering. The effect of the thickness of the layers on shrinkage, warpage, and pore-grain structure is studied. Ceramic ZnO powders are employed as a model experimental system to assess the model predictions.

Biomimetic Non-Immunogenic Nanoassembly for the Antitumor Therapy

Nanoassembly (1) for inducing apoptosis in cancer cells comprising: a core (2) comprising at least a nanoparticle of a nano structured and semiconductor metal oxide, said nanoparticle being monocrystalline or polycrystalline; a shell (3) formed by a double phospholipid layer and proteins derived from an extracellular biovesicole chosen between an exosome, an ectosome, a connectosome, an oncosome and an apoptotic body, and an oncosome, said core (2) being enclosed inside said shell (3); and a plurality of targeting molecules (4, 4', 4") of said cancer cells, preferably monoclonal antibodies (4, 4', 4"), said molecules (4, 4', 4") being anchored to the external surface of said biovesicole

Fabrication and Characterization of PZT Thin-Film on Bulk Micromachined Si Motion Detectors

Motion detectors consisting of Pb(Zr{sub x}Ti{sub (1{minus}x)})O{sub 3} (PZT) thin films, between platinum electrodes, on micromachined silicon compound clamped-clamped or cantilever beam structures were fabricated using either hot KOH or High Aspect Ratio Silicon Etching (HARSE) to micromachine the silicon. The beams were designed such that a thicker region served as a test mass that produced stress at the top of the membrane springs that supported it when the object to which the detector was mounted moved. The PZT film devices were placed on these membranes to generate a charge or a voltage in response to the stress through the piezoelectric effect. Issues of integration of the PZT device fabrication process with the two etching processes are discussed. The effects of PZT composition and device geometry on the response of the detectors to motion is reported and discussed

Electrorheological fluids

An Electrorheological fluid is normally a low-viscosity colloidal suspension, but when an electric field is applied, the fluid undergoes a reversible transition to a solid, being able to support considerable stress without yield. Commercial possibilities for such fluids are enormous, including clutches, brakes, valves,shock absorbers, and stepper motors. However, performance of current fluids is inadequate for many proposed applications. Our goal was to engineer improved fluids by investigating the key technical issues underlying the solid-phase yield stress and the liquid to solid switching time. Our studies focused on field-induced interactions between colloidal particles that lead to solidification, the relation between fluid structure and performance (viscosity, yield stress), and the time evolution of structure in the fluid as the field is switched on or off