Proteasome Inhibitor Anticancer Drug Bortezomib Redox Behaviour at a Glassy Carbon Electrode

Electrochemistry as a Powerful Tool for Investigations of Antineoplastic Agents: A Comprehensive Review

Cancer is most frequently treated with antineoplastic agents (ANAs) that are hazardous to patients undergoing chemotherapy and the healthcare workers who handle ANAs in the course of their duties. All aspects related to hazardous oncological drugs illustrate that the monitoring of ANAs is essential to minimize the risks associated with these drugs. Among all analytical techniques used to test ANAs, electrochemistry holds an important position. This review, for the first time, comprehensively describes the progress done in electrochemistry of ANAs by means of a variety of bare or modified (bio)sensors over the last four decades (in the period of 1982-2021). Attention is paid not only to the development of electrochemical sensing protocols of ANAs in various biological, environmental, and pharmaceutical matrices but also to achievements of electrochemical techniques in the examination of the interactions of ANAs with deoxyribonucleic acid (DNA), carcinogenic cells, biomimetic membranes, peptides, and enzymes. Other aspects, including the enantiopurity studies, differentiation between single-stranded and double-stranded DNA without using any label or tag, studies on ANAs degradation, and their pharmacokinetics, by means of electrochemical techniques are also commented. Finally, concluding remarks that underline the existence of a significant niche for the basic electrochemical research that should be filled in the future are presented.

In situ Electrochemical Evaluation of the Interaction of dsDNA with the Proteasome Inhibitor Anticancer Drug Bortezomib

Bortezomib is an inhibitor of proteasomes and an anti-cancer drug. Although bortezomib is considered a safe drug, as confirmed by cytotoxicity assays, recent reports highlighted the possibility of interaction between bortezomib and cellular components, with detrimental long-term effects. The evaluation of the interaction between bortezomib and dsDNA was investigated in bulk solution and using a dsDNA electrochemical biosensor. The binding of bortezomib to dsDNA involved its electroactive centers and led to small morphological modifications in the dsDNA double helix, which were electrochemically identified through changes in the guanine and adenine residue oxidation peaks and confirmed by electrophoretic and spectrophotometric measurements. The redox product of bortezomib amino group oxidation was electrochemically generated in situ on the surface of the dsDNA electrochemical biosensor. The redox product of bortezomib was shown to interact primarily with guanine residues, preventing their oxidation and leading to the formation of bortezomib–guanine adducts, which was confirmed by control experiments with polyhomonucleotides electrochemical biosensors and mass spectrometry. An interaction mechanism between dsDNA and bortezomib is proposed, and the formation of the bortezomib redox product–guanine adduct explained.

An antibody-based amperometric biosensor for 20S proteasome activity and inhibitor screening

The 20S proteasome enzyme complex is involved in the proteolytic degradation of misfolded and oxidatively damaged proteins and is a focus of medical research for the development of compounds with pharmaceutical properties, which are active in cancer cells and/or neurodegenerative diseases. The present study aims to develop a biosensor for investigating the 20S proteasome activity and inhibition by means of electrochemical methods. The 20S proteasome is best immobilized at the electrode surface through bio-affinity interactions with antibodies that target different subunits on the 20S proteasome, enabling the investigation of the effect of an enzyme's orientation on biosensor response. The enzymatic activity is analyzed by fixed potential amperometry with the highest sensitivity of 24 μA cm^-2 mM^-1 and a LOD of 0.4 μM. The detection principle involves the oxidation of an electroactive probe that is released from the enzyme's substrates upon proteolysis. The most sensitive biosensor is then used to study the multicatalytic activity of the 20S proteasome, i.e. the caspase-, trypsin- and chymotrypsin-like activity, by analyzing the biosensor's sensitivity towards different substrates. The behavior of the immobilized 20S proteasome is investigated as a function of substrate concentration. The kinetic parameters are derived and compared with those obtained when the enzyme was free in solution, with K_0.5 values being one to two orders of magnitude lower in the present case. Two 20S inhibitors, epoxomicin and bortezomib, are investigated by analyzing their influence on the 20S biosensor response. The proposed analytical method for proteasome activity and inhibitor screening has the main advantage of being cost-effective compared to the ones typically employed.

Charge transfer reaction mechanisms of epoxyketone and boronated peptides at glassy carbon and boron doped diamond electrodes

The ubiquitin-proteasome system regulates the level of proteins within cells through controlled proteolysis. In some diseases, the system function is dysregulated turning the ubiquitin-proteasome complex into a target for drug development. The redox behavior of proteasome inhibitors, epoxyketone and boronated peptides carfilzomib, oprozomib and delanzomib was investigated by voltammetric methods using glassy carbon and boron doped diamond electrodes. It was showed that the oxidation of epoxyketone peptides carfilzomib and oprozomib occurred in one step at glassy carbon electrode surface while at boron doped diamond two consecutive charge transfer reactions due to different adsorption orientation at the electrode surface were observed. The moieties of these peptides, involved in the oxidation process, were morpholine for carfilzomib and thiazole for oprozomib. For the boronated peptide delanzomib, two irreversible and independent redox processes, oxidation at +0.80 V and reduction at −1.40 V were identified in neutral media at both electrodes. The oxidation reaction occurred at the amino group close to the pyridine moiety of delanzomib with the transfer of one electron and one proton whereas the reduction process takes place at pyridine ring in a two-electrons two-protons mechanism. Redox mechanisms were proposed and the implications on the proteasome inhibition discussed.

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Electranalysis of proteasome inhibitor peptides and anticancer drugs.

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Carfilzomib and oprozomib epoxiketones, and boronated delanzomib peptides.

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Redox behavior at glassy carbon and boron doped diamond electrodes..

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Redox mechanisms proposed and implications discussed.