Simulation and Experiments on Magnetic MicroForces for Magnetic MicroRobots Applications

Abstract—Magnetic microrobots have a wide variety of applications in micro/nano-manipulation, micro/nano sensing and biomedical fields. Untethered magnetic microrobots are usually driven by a group of electromagnetic coils. To control the magnetic microrobots trajectory, it is of utmost importance to know the magnitude of the magnetic force applied on them. In this paper finite element simulations are proposed to derive the magnetic field produced by an iron core coil. A three dimensional static magnetic analysis is also performed to simulate the magnetic force applied on a magnetic microrobot. The simulation results are validated by experimental measurements. A teslameter is used to measure the magnetic field on the central axis of the coil. A magnetic microrobot (less than 400 x 400 µm 2) is fabricated and glued to a force sensor to measure the magnetic force applied on it. The measurement results are in good agreement with the simulation and show the effectiveness of the magnetic simulation. Keywords—magnetic microrobot; magnetic field measurement; magnetic microforce I

A general strategy to optimize immunogenicity of HLA-B*0702 restricted cryptic peptides from tumor associated antigens: Design of universal neo-antigen like tumor vaccines for HLA-B*0702 positive patients

International audienceTumor Associated Antigens (TAAs) are the privileged targets of almost all the cancer vaccines tested to date. Unfortunately all these vaccines failed to show a clinical efficacy. The main reason for this failure is the immune tolerance to TAAs that are self-proteins expressed by normal and cancer cells. Self-tolerance to TAAs is directed against their dominant rather than against their cryptic epitopes. The best way to overcome self-tolerance to TAAs would therefore be to target their cryptic epitopes. However, because of their low HLA-I affinity, cryptic peptides are non-immunogenic and cannot be used to stimulate an antitumor immune response unless their immunogenicity has been previously enhanced. In this paper we describe a general approach to enhance immunogenicity of almost all the HLA-B*0702 restricted cryptic peptides derived from TAAs. It consists in substituting residues at position 1 or 9 of low HLA-B*0702 affinity cryptic peptides by an Alanine or a Leucine respectively. These substitutions increase affinity of peptides for HLA-B*0702. These optimized cryptic peptides are strongly immunogenic and very importantly CTL they stimulate recognize their native counterparts. TAAs derived optimized cryptic peptides can be considered as universal antitumor vaccine since they escape self-tolerance, are immunogenic and are not patient specific

pH-Responsive PEG/PAA Multilayer Assemblies for Reversible Adhesion of Micro-Objects

International audienceManipulating micro-objects plays a crucial role in a wide range of fundamental and applied research works. Here, we propose an original strategy based on the chemical modification of a substrate by hydrogen-bonded films elaborated by layer-by-layer (LbL) assemblies of poly(ethylene glycol) (PEG) and poly(acrylic acid) (PAA). First, the influence of the polymer molecular weight on the growth of the PEG/PAA multilayer was evaluated. Optical reflectometry analysis used to follow in situ the film buildup revealed a strong dependence of the deposited amount of polymer on the ratio of monomer units of each polymer (nPAA/nPEG). Then, colloidal probe atomic force microscopy (AFM) microscopy was carried out in an aqueous medium to monitor the adhesion forces of multilayer surfaces composed of N polymer layers. Pull-off forces were converted using the Johnson–Kendall–Roberts (JKR) model to access the thermodynamic work of adhesion. Results indicated that PEG/PAA multilayer films exhibit weak adhesion forces that are sensitive to the number of deposited polymer layers at pH 2. In addition, a progressive increase of the solution pH reduced the adhesion due to the destruction of the hydrogen-bonded multilayer film. To simulate the capture and the release of a micro-object, borosilicate particles acting as spherical micro-objects were adsorbed onto a PEG/PAA film. Once again, an increase of the solution pH led to desorption of particles, as shown by optical microscopy. Finally, an AFM tip functionalized by a PEG/PAA multilayer was used to achieve successful micromanipulation operations (capture and release) of a 10 μm diameter borosilicate sphere in an aqueous solution