Transition‐Metal‐Mediated versus Tetrazine‐Triggered Bioorthogonal Release Reactions: Direct Comparison and Combinations Thereof

Abstract

Bioorthogonal cleavage reactions are gaining popularity in chemically inducible prodrug activation and in the control of biomolecular functions. Despite similar applications, these reactions were developed and optimized on different substrates and under different experimental conditions. Reported herein is a side‐by‐side comparison of palladium‐, ruthenium‐ and tetrazine‐triggered release reactions, which aims at comparing the reaction kinetics, efficiency and overall advantages and limitations of the methods. In addition, we disclose the possibility of mutual combination of the cleavage reactions. Finally, we compare the efficiency of the bioorthogonal deprotections in cellular experiments, which revealed that among the three methods investigated, the palladium‐ and the tetrazine‐promoted reaction can be used for efficient prodrug activation, but only the tetrazine‐triggered reactions proceed efficiently inside cells.

Structurally Redesigned Bioorthogonal Reagents for Mitochondria-Specific Prodrug Activation

“…Toward this goal, we employed our recently developed TCO-caged resorufin dye conjugate (TCO-Reso). 53 Our initial experiments performed in a well plate format revealed that tetrazines bearing a single methyl substituent release almost 50% of the resorufin dye from TCO-Reso within the first hour. In contrast, tetrazines having an aryl substituent at this position displayed a rather slow gradual release of the dye over 12 h (Figure S21B).…”

“…Because our cationic tetrazines comprise a structurally unprecedented motif, we first evaluated their releasing efficacy. Toward this goal, we employed our recently developed TCO-caged resorufin dye conjugate (TCO-Reso) . Our initial experiments performed in a well plate format revealed that tetrazines bearing a single methyl substituent release almost 50% of the resorufin dye from TCO-Reso within the first hour.…”

Metal substrate catalysis in the confined space for platinum drug delivery

“…9,11,13,14 Despite proving the potential of catalysis-based approaches in medicine, the great majority of the schemes proposed so far display rather modest catalytic efficiencies, even in buffer solutions, as evidenced by low turnover numbers (TONs) and slow reaction kinetics. 15 The latter aspect is especially overlooked by the scientic community working in this eld, yet of key importance in the development of drug activation strategies. Apart from few exceptions, 2,12,16,17 catalysts currently reported in the literature typically achieve substrate conversion rates in solution that are in the order of 0.1-10 h À1 (10 À3 to 10 À1 min À1 ).…”

“…prodrug) to induce the desired therapeutic effects. In such a scenario, the catalyst intrinsic toxicity is critical 15 and the choice of drugs with high-potency (sub-μM) becomes often mandatory, overall limiting the therapeutic scope of several catalysis-based strategies for prodrug activation.…”

Bioorthogonal Chemistry in Cellular Organelles

“…Intriguingly, pretreatment of cells with Pd reagents followed by the addition of the pro-fluorophore failed to generate any fluorescent signal, presumably because of the conversion of Pd complexes to inactive species. In another study, it was observed that even in simple systems such as phosphate-buffered saline, transition metal catalysts underwent partial deactivation [ 118 ].

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