Voltammetric study of the behaviour of N-acetyl-p-aminophenol in aqueous solutions at a platinum electrode

The electrochemical oxidation of N-acetyl-p-aminophenol (PAR) was investigated at a Pt electrode with the application of cyclic (CV) and differential pulse (DPV) voltammetry methods. An effect of scan rate, substrate concentration and pH on electrode reactions was determined. The parameters of substrate electro-oxidation, i.e. heterogeneous rate constant, charge transfer coefficient, and diffusion coefficient, were calculated. Our investigation's results prove the exchange of two electrons and one proton in the first step, followed by a chemical reaction. PAR electro-oxidation occurs according to an EC mechanism.     

Assessment of the beneficial combination of electrochemical and ultrasonic activation of compounds originating from biomass

The electro-oxidation of organic molecules at the anode with simultaneous generation of hydrogen at the cathode in electrosynthesis reactors is considered as a promising and efficient process for the co-production of hydrogen and bio-sourced value-added chemicals. In this study and for the first time, we investigated the electro-oxidation of glucose and methylglucoside in 0.1 mol L⁻¹ NaOH on polycrystalline Pt (real surface area = 14.5 ± 0.5 cm², roughness ≈ 5) in the potential range [0; +1.20 V vs. rhe] under silent and ultrasonic (bath, 45 kHz, P_acous = 11.20 W) conditions. A series of linear sweep voltammograms, chronoamperograms and high-performance liquid chronoamperograms were generated. It was found that higher current densities were obtained under ultrasonic conditions over the potential range of +0.25 V to +1.10 V vs. rhe, indicating that higher oxidation rates were provided under ultrasonication. It was observed that the desorption of species from the Pt surface in the medium potential region was favoured, allowing free catalytic Pt sites for further adsorption and oxidation of reactants; and in the high potential region, high peak current densities in the presence of ultrasound was due to enhanced mass transport of the electroactive species from the bulk electrolyte to the Pt-polycrystalline electrode surface. HPLC studies confirmed that higher electrochemical activity was obtained in the presence of ultrasound than in the absence. In our conditions, it was also found that low frequency ultrasound did not change the selectivity of the glucose and methylglucoside electro-oxidation reactions but instead, a significant increase in the rate of conversion was observed.     

Overcoming Cancer Resistance to Platinum Drugs by Inhibiting Cholesterol Metabolism

Drug resistance is a serious challenge for platinum anticancer drugs. Platinum complexes may get over the drug resistance via a distinct mechanism of action. Cholesterol is a key factor contributing to the drug resistance. Inhibiting cellular cholesterol synthesis and uptake provides an alternative strategy for cancer treatment. Platinum(IV) complexes FP and DFP with fenofibric acid as axial ligand(s) were designed to combat the drug resistance through regulating cholesterol metabolism besides damaging DNA. In addition to producing reactive oxygen species and active platinum(II) species to damage DNA, FP and DFP inhibited cellular cholesterol accumulation, promoted cholesterol efflux, upregulated peroxisome proliferator-activated receptor alpha (PPARα), induced caspase-1 activation and gasdermin D (GSDMD) cleavage, thus leading to both apoptosis and pyroptosis in cancer cells. The reduction of cholesterol significantly relieved the drug resistance of cancer cells. The double-acting mechanism gave the complexes strong anticancer activity in vitro and in vivo, particularly against cisplatin-resistant cancer cells.     

Bulk-like Pt(100)-oriented Ultrathin Surface: Combining the Merits of Single Crystals and Nanoparticles to Boost Oxygen Reduction Reaction

Single crystal surfaces with highly coordinated sites very often hold high specific activities toward oxygen reduction reaction (ORR) and others. Transposing their high specific activity to practical high-surface-area electrocatalysts remains challenging. Here, ultrathin Pt(100) alloy surface is constructed via epitaxial growth. The surface shows 3.1–6.9 % compressive strain and bulk-like characteristics as demonstrated by site-probe reactions and different spectroscopies. Its ORR activity exceeds that of bulk Pt₃Ni(100) and Pt(111) and presents a 19-fold increase in specific activity and a 13-fold increase in mass activity relative to commercial Pt/C. Moreover, the electrochemically active surface area (ECSA) is increased by 4-fold compared to traditional thin films (e.g. NSTF), which makes the catalyst more tolerant to voltage loss at high current densities under fuel cell operation. This work broadens the family of extended surface catalysts and highlights the knowledge-driven approach in the development of advanced electrocatalysts.     

Reduction of Platinum(IV) Prodrug Hemoglobin Nanoparticles with Deeply Penetrating Ultrasound Radiation for Tumor-Targeted Therapeutically Enhanced Anticancer Therapy

The development of Pt^IV prodrugs that are reduced into the therapeutically active Pt^II species within the tumor microenvironment has received much research interest. In order to provide spatial and temporal control over the treatment, there is a high demand for the development of compounds that could be selectively activated upon irradiation. Despite recent progress, the majority of Pt^IV complexes are excited with ultraviolet or blue light, limiting the use of such compounds to superficial application. To overcome this limitation, herein, the first example of Pt^IV prodrug nanoparticles that could be reduced with deeply penetrating ultrasound radiation is reported, enabling the treatment of deep-seated or large tumors. The nanoparticles were found to selectively accumulate inside a mouse colon carcinoma tumor upon intravenous injection and were able to eradicate the tumor upon exposure to ultrasound radiation.     

Front Cover: Synthesis,Characterization, and Cytotoxicity of a Reactive Platinum(IV) Monotrifluoromethyl Complex (Eur. J. Inorg. Chem. 3/2023)

Platinum-based complexes are among the most widely utilized cancer therapeutics. Current Pt(II) drugs face some challenges including toxicity and drug resistance. To solve these issues, great efforts have been devoted to developing nonclassical platinum complexes, such as Pt(IV) prodrugs, that act via mechanisms distinct from those of the approved drugs. Compared with active Pt(II) counterparts, Pt(IV) complexes are relatively inert. Although direct interactions between Pt(IV) complexes and nucleotides have been reported, the reaction is slow due to the kinetic inertness of Pt(IV) complexes. Herein, we design and synthesize a Pt(IV) monotrifluoromethyl complex, in which the chloride ligand that is trans to trifluoromethyl ligand is reactive. The Pt(IV) monotrifluoromethyl complex is very stable in water but displays high reactivity towards various substrates including buffer components and 5’-dGMP. The study of reaction mechanism reveals that this Pt(IV) complex reacts with phosphate via S_N2 nucleophilic substitution pathway, which is different from Pt(II) drugs. The Pt(IV) monotrifluoromethyl complex is cytotoxic in human ovarian cancer cells. Our work reports an example of a reactive organometallic Pt(IV) complex that can directly interact with nucleophiles and implies its potential as an anticancer agent.     

Influence of the Solvent on the “Casting” Methodology for MWCNT‐Modified Glassy Carbon and Platinum Electrodes

The choice of electrode material and surface preparation method are usually dictated by the suitability of the electrode to observe an electrochemical parameter, such as heterogeneous electron transfer rate, surface coverage, or redox potential. Thus, the glassy carbon (GC) and platinum (Pt) electrodes were modified with multiwalled carbon nanotubes (MWCNT) by direct “casting” modification using nine different aliquots of solvents. After drying at room temperature, the modified electrode showed distinct redox peaks corresponding to ferrocyanide oxidation/reduction. Using chemometrics, the cyclic voltammograms with higher current intensity were obtained for those in which ethanol, water and acetone as dispersing agents were used for GCE and dimethylformamide, water and acetone for Pt electrode modification.     

Improved hydrogen evolution on glassy carbon electrode modified with novel Pt/cetyltrimethylammonium bromide nanoscale aggregates

A novel, cost‐effective, and simple electrocatalyst based on a Pt‐modified glassy carbon electrode (GCE), using cetyltrimethylammonium bromide (CTAB) as a cationic surfactant, is reported. Am‐phiphilic...     

Acetate platinum(II) compound with 5,7-ditertbutyl-1,2,4-triazolo[1,5-a]pyrimidine that overcomes cisplatin resistance: structural characterization,in vitro cytotoxicity,and kinetic studies

The reaction of silver acetate with cis-[PtI₂(dbtp)₂], where dbtp = 5,7-ditertbutyl-1,2,4-triazolo-[1,5-a]pyrimidine, yielded cis-[Pt(OOCCH₃)₂(dbtp)₂]·dmf (1). The complex has been analyzed by multinuclear magnetic resonance (¹H, ¹³C, ¹⁵N), IR, and Raman. The compound formed two rotamers in CDCl₃ and its spatial structures have been optimized using computational calculation. It was found that head-to-tail rotamer (1a) is more stable than its head-to-head counterpart (1b). In vitro antiproliferative activity against four tumor cell lines (A549, T47D, FaDu, and A2780cis) revealed in all cases significant cytotoxicity (IC₅₀ = 0.26–1.80 μM), possessing IC₅₀ values at least fivefold lower than cisplatin, carboplatin, and oxaliplatin (except A2780cis). The remarkable in vitro activity against T47D and A2780cis suggested the ability to overcome cisplatin resistance in these types of tumor cells. In addition, in vitro toxicity was evaluated against BALB/3T3 and has shown that the lipophilic platinum(II) complex (1) inhibits cell proliferation weaker than cisplatin and oxaliplatin. Additionally, cis-[Pt(OOCCH₃)₂(dbtp)₂]·dmf exhibited selective activity, in contrast to cisplatin or oxaliplatin.