E.Krisch, B. Gyarmati, D. Barczikai, V. Lapeyre, B.A. Szilágyi, V. Ravaine, A. Szilágyi
Redox and pH responsive hydrogels were synthesized, which can serve as matrices for smart drug deliveryRedox and pH responsive hydrogels were synthesized, which can serve as matrices for smart drug deliverysystems exploiting the redox and pH gradients in the human body. Water soluble thiolated poly(aspartic acid), abiocompatible synthetic polymer, enables us to cross-link in water with a non-cleavable cross-linker, poly(ethylene glycol) diglycidyl ether. The permanent cross-linker establishes stable polymer hydrogels regardless ofthe redox environment, thus the gels swell but do not dissolve upon redox stimuli. The reversible response uponredox stimulus was induced by thiol-disulphide transformation inside the hydrogel. The degree of swelling andthe stiffness of the macroscopic hydrogels were controlled by their chemical composition including thiol contentand cross-linking ratio as well as the redox state of the hydrogels. The degree of swelling of the hydrogels showedstrong pH dependence due to the polyelectrolyte nature of the polymer network. Release of a macromolecularmodel drug was considerably faster in reducing than in oxidising environment, which indicates the potential useof the synthesized hydrogels as redox responsive drug delivery systems. Nanogels were prepared in water-in-oilemulsion and displayed redox-responsive properties. The hydrodynamic diameter of the nanogels strongly increasedupon the cleavage of the disulphide linkages in reducing solution without the disruption of the gels.
L. Adam, A. Kuhn
Les molécules chirales sont d’un grand intérêt dans un certain nombre de domaines tels que la médecine, la biologie ou encore la chimie. Il est donc important de fournir de nouveaux concepts pour la détection et la synthèse énantiosélective. Dans ce but, des métaux mésoporeux contenant une information chirale ont été développés. Ils sont obtenus à partir de la réduction d’un sel de platine en présence d’une phase cristal liquide et de la molécule chirale. En fin d’électrodéposition, les moules moléculaires sont retirés et l’information chirale est conservée par le métal. Les électrodes mésoporeuses chirales ainsi élaborées sont utilisées à des fins analytiques ou encore pour la synthèse sélective d’énantiomères. Cette approche a permis récemment d’atteindre un excès énantiomérique de plus de 90 % pour la synthèse d’un composé chiral.
J.-P. Douliez, A. Perro, J.-P. Chapel, B. Goudeau and L. Béven
A template-free all-aqueous bulk preparation of robust hollow capsules having a gelatin shell from all-in-water double emulsions is reported. The hot (>40 °C) quaternary system water/polyethylene glycol (PEG)/gelatin/ alginate is shown to spontaneously form PEG-in-gelatin-in-PEG double water emulsion droplets having a multinuclear core. These droplets are stable upon cooling below the temperature at which gelatin gelled. In contrast, above the melting temperature of gelatin, multinuclear double emulsion droplets controllably evolve into stable mononuclear yolk (aqueous PEG)- shell (gelatin) capsules dispersed in the aqueous PEG continuous phase. It is demonstrated that the gelatin shell can accommodate negatively charged latex beads and be re-enforced by glutaraldehyde or silica. These capsules are also shown to encapsulate payloads, suggesting possible applications in microencapsulation, drug delivery, and synthetic biology.
L. Zhang, B. Gupta, B. Goudeau, N. Mano, A. Kuhn
Collecting electrochemical information concerning the presence of molecules in a solution is usually achieved by measuring current, potential, resistance or impedance via connection to a power supply. Here, we suggest wireless electromechanical actuation as a straight-forward readout of chemical information. This can be achieved based on the concept of bipolar electrochemistry, which allows measuring the presence of different model species in a quantitative way. We validate the concept by using a free-standing polypyrrole film. Its positively polarized extremity participates in an oxidation of the analyte and delivers electrons to the opposite extremity for the reduction of the polymer. This reduction is accompanied by the insertion of counter ions and thus leads to partial swelling of the film, inducing its bending. The resulting actuation is found to be a linear function of the analyte concentration and also a Michaelis-Menten type correlation is obtained for biochemical analytes. This electromechanical transduction allows an easy optical readout and opens up very interesting perspectives not only in the field of sensing, but also far beyond, such as for the elaboration of self-regulating biomimetic systems.
T. D. Le, L. Zhang, S. Reculusa, G.Vignoles, N. Mano, A. Kuhn, D. Lasseux
This article reports on a procedure to predict the optimal thickness of cylindrical porous electrodes operating a single redox reaction. This is obtained from a macroscopic model for the coupled diffusion-reaction process that is first validated with voltammetry experiments of H2O2/H2O reduction reaction carried out with a series of porous electrodes elaborated in this work. An analytical solution to this model is developed in the steady regime and for electrodes featuring a thickness to mean radius ratio small enough compared to unity. An analytical expression of the optimal electrode thickness is derived corresponding to the crossover value of two asymptotic regimes characterizing the dependence of the volume current density produced by the electrode upon its thickness. The predictive tool of the optimal thickness is general, regardless the porous microsctructure. The case of the electrodes used in the reported experiments illustrates that the optimal thickness is not intrinsic to the microsctructure characterized by the size of the representative volume, its specic area and effective diffusion coefficient. It also depends on the operating conditions reflected in the kinetic number, Ki, and the thickness of the diffusion layer surrounding the electrode. The dependence of the optimal thickness on these two parameters is quite signicant in a range of very small values of Ki but remains quasi constant beyond a threshold value.
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