Intracellular Activation of Bioorthogonal Nanozymes through Endosomal Proteolysis of the Protein Corona

Abstract

Bioorthogonal activation of prodrugs provides a strategy for on-demand on-site production of therapeutics. Intracellular activation provides a strategy to localize therapeutics, potentially minimizing off-target effects. To this end, nanoparticles embedded with transition metal catalysts (nanozymes) were engineered to generate either “hard” irreversible or “soft” reversible coronas in serum. The hard corona induced nanozyme aggregation, effectively inhibiting nanozyme activity, whereas only modest loss of activity was observed with the nonaggregating soft corona nanozymes. In both cases complete activity was restored by treatment with proteases. Intracellular activity mirrored this reactivation: endogenous proteases in the endosome provided intracellular activation of both nanozymes. The role of intracellular proteases in nanozyme reactivation was verified through treatment of the cells with protease inhibitors, which prevented reactivation. This study demonstrates the use of intracellular proteolysis as a strategy for localization of therapeutic generation to within cells.

Transition Metal‐Promoted Reactions in Aqueous Media and Biological Settings

“…Adapted with permission of refs. [105] and [106]. Copyright (2019 and 2020) American Chemical Society.…”

“…For instance, nanozymes having the hydrophobic segment but lacking the PEG‐fraction lead to protein denaturation and irreversible protein adsorption (hard corona, Figure 37 B). Nonetheless, the catalytic activity in these passivated particles can be restored upon proteolysis of the protein corona with endogenous proteases such as trypsin [106, 107] …”

“…In subsequent years, the same group developed related nanoenzymes with different properties. [104][105][106][107] For instance, surface engineering was used to dictate either extra-or intracellular localization of the nanozymes. Thus, surfacef unctionalization with zwitterionic sulfobetaine moieties (Ru-Nz-2)l imits the Ru-promotedu ncagingo fp rorhodamine and pro-resorufin to the extracellulars pace (Figure 37 A).…”

“…Nonetheless,t he catalytic activity in these passivated particles can be restoredu pon proteolysis of the protein corona withe ndogenous proteases such as trypsin. [106,107] Allyloxycarbonyl groups can also be cleaved using the Pd microspheres developed by Bradleya nd Unciti-Broceta (Pd-2, see Figure 15). In particular, this group showed the deprotection of N-alloc caged rhodamine 110( 30 mm)i nH eLa cells (incubation time 24 h).…”

Intracellular Activation of Anticancer Therapeutics Using Polymeric Bioorthogonal Nanocatalysts

“…[ 9–12 ] Recently, transition metal catalyst (TMCs) mediated bond‐cleavage bioorthogonal catalysis has shown potential for biomedical applications, combining efficient catalysis with a broad range of possible transformations. [ 13–18 ] “Naked” TMCs have challenges arising from stability, concerns that have been addressed by loading TMCs onto/in inorganic nanomaterials, [ 19–23 ] including gold nanoparticles, [ 24–30 ] metal–organic frameworks, [ 31 ] and mesoporous silica nanoparticles, [ 32,33 ] providing “nanozymes” for imaging and therapeutic applications. [ 34 ] Engineering the surface functionalization of these nano‐scaffolds can impart stimuli responsiveness, [ 16,23 ] biostability, [ 21 ] and localize the nanozyme at desired target sites such as biofilms, [ 17 ] cells, [ 35 ] inflamed areas, [ 36 ] and the extracellular matrix.…”