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Many physical and chemical properties of solids, such as strength, plasticity, dispersibility, solubility and dissolution are determined by defects in the crystal structure. The aim of this work is to study in situ dynamic, dispersion, chemical, biological and surface properties of lacosamide powder after a complete cycle of mechanical loading by laser scattering, electron microscopy, FR-IR and biopharmaceutical approaches. The SLS method demonstrated the spontaneous tendency toward surface-energy reduction due to aggregation during micronisation. DLS analysis showed conformational changes of colloidal particles as supramolecular complexes depending on the loading time on the solid. SEM analysis demonstrated the conglomeration of needle-like lacosamide particles after 60 min of milling time and the transition to a glassy state with isotropy of properties by the end of the tribochemistry cycle. The following dynamic properties of lacosamide were established: elastic and plastic deformation boundaries, region of inhomogeneous deformation and fracture point. The ratio of dissolution-rate constants in water of samples before and after a full cycle of loading was 2.4. The lacosamide sample, which underwent a full cycle of mechanical loading, showed improved kinetics of API release via analysis of dissolution profiles in 0.1 M HCl medium. The observed activation-energy values of the cell-death biosensor process in aqueous solutions of the lacosamide samples before and after the complete tribochemical cycle were 207 kJmol−1 and 145 kJmol−1, respectively. The equilibrium time of dissolution and activation of cell-biosensor death corresponding to 20 min of mechanical loading on a solid was determined. The current study may have important practical significance for the transformation and management of the properties of drug substances in solid form and in solutions and for increasing the strength of drug matrices by pre-strain hardening via structural rearrangements during mechanical loading. [ABSTRACT FROM AUTHOR]

In solar cells, hybrid halide perovskites operate under constant bias, thus their stability towards electric field-induced degradation is of key importance. Here we report on evidence of previously unidentified electric field-induced transitions and degradation path of CH3NH3PbI3 (MAPbI3) using elemental and phase mapping. Thin films of MAPbI3 were deposited onto 1–2 µm-pitch interdigitated electrodes and subjected to direct current (DC)-polarization. The MAPbI3 layer polarized with < 0.8 V/µm DC electric field undergoes pronounced ion redistribution to methylammonium-rich MAPbI3−y (y < 0.6) and iodine-rich MA1−xPbI3 (x < 0.3) regions. Polarization-induced loss of both methylammonium and iodine provokes degradation of MAPbI3. Using nanofocus grazing-incidence wide-angle X-ray scattering (GIWAXS), we unambiguously showed that the bias voltage induces the transformation of β-MAPbI3 to metastable δ-MAPbI3 polymorph via alignment of polar organic cation with the electric field. This transformation is partially reversible upon field removal. However, once formed, δ-MAPbI3 disrupts the morphology of pristine film and undergoes decomposition to β-MAPbI3 (β-MAPI) and PbI2. With the aforementioned compositional and phase changes, only MA-rich part serves as the charge separation layer, while the I-rich excitation is blocked with the PbI2 barrier serving as holes trapping layer. These observations reveal the intermediate steps in electric-field-driven degradation of halide perovskites and show the role of polar cations in the process, which is instructive for further material design with higher stability metrics. [ABSTRACT FROM AUTHOR]

We report on fully electrochemical flow-through synthesis of Prussian Blue based nanozymes defeating peroxidase in terms of more than 200 times higher catalytic rate constant (kcatapp = 6 x 104 s-1). Being reagentless, reproducible, simple and scalable, the proposed approach blazes new trails for the electrosynthesis of functional conductive and electroactive nanomaterials. [ABSTRACT FROM AUTHOR]

This letter introduces the pre-steady-state kinetic approach, which is traditional for evaluation of elementary constants in molecular (enzyme) catalysis, for nanozymes. Apparently, the most active peroxidase-mimicking nanozyme based on catalytically synthesized Prussian Blue nanoparticles has been chosen. The elementary constants ( k 1 ) linearly decays with an increase of the substrate redox potential (cotangent value ≈125 mV). On the contrary, for the largest nanozymes with a diameter above 150 nm, k 1 ) linearly decays with an increase of the substrate redox potential (cotangent value ≈125 mV). On the contrary, for the largest nanozymes with a diameter above 150 nm, k 1 is almost independent of it. Moreover, for the substrate with the lowest redox potential (K 4 [Fe(CN) 6 ]), the rate constant under discussion ( k 1 ) is almost independent of the nanozymes' size. Perhaps, the rate of the intrananozyme electron transfer causing bleaching becomes comparative or even lower than that of the nanoparticle interaction with the fastest substrate. Anyway, the elementary constant of nanozyme reduction with potassium ferrocyanide ( k 1 ) reaches the value of 1 × 10 10 M -1 s -1 , which is 3-4 orders of magnitude faster than for enzymes peroxidases. The obtained results obviously demonstrate that the pre-steady-state kinetic approach is able to discover novel advantages of nanozymes from both fundamental and practical points of view.

Catalytic current of pyrroloquinoline quinone (PQQ)-glucose dehydrogenase (PQQ-GDH) immobilized over electropolymerized methylene green (MG) is increased only five times after the addition of the freely diffusing mediator. This value, being an efficiency criterion for bioelectrocatalysis, is several (three to six) times lower than that for the best reagentless glucose electrodes reported for this enzyme. Thermodynamics of the polyMG|PQQ-GDH electrode is determined by the enzyme-catalyzed reaction pointing to the direct bioelectrocatalysis. PQQ-GDH immobilized over polyMG displays the current plateau region from 0.0 to 0.2 V in the presence of glucose; at 0.00 V, being the optimal potential for biosensing applications, the catalytic current of the polyMG|PQQ-GDH electrode is 700-fold higher than that for the enzyme on a blank electrode. Successful glucose detection in human sweat by means of the corresponding enzyme electrode confirms that the reported bioelectrocatalytic system is attractive for advanced biosensors, as well as for biofuel cells.