Single-atom nanozymes (SAzymes) with 100% steel atom utilization have emerged as novel high-efficient anticancer therapeutic reagents, [1], [2], [3], [4], [5], [6], [7], [8], [9], [10] and have been utilized within the fields of photothermal remedy (PTT), [11], [12] chemodynamic remedy (CDT), [13], [14], [15], [16], [17], [18] photodynamic remedy (PDT), [19] sonodynamic remedy (SDT) [20] and so forth. Though organelles or proteins are broken throughout these remedies, [21], [22], [23], [24] sensible tumor cells have a sound protecting mechanism to withstand exterior harm. Amongst them, autophagy, a mobile self-devouring course of, can survive most cancers cells by the lysosome degrading impaired organelles and biomacromolecules, thereby offering vitamins for regenerating newer, more healthy cells. [25], [26], [27] The precise autophagy flux (macroautophagy) refers back to the engulfment of broken cytoplasmic materials within the double-membranes vesicles known as autophagosomes. [28], [29], [30] The autophagosome self-protective autophagy severely compromises SAzymes based mostly therapeutic outcomes. [31] To resolve this drawback, some autophagy inhibitors, similar to chloroquine, [32], [33], [34] hydroxychloroquine, [35] 3-Methyladenine, [36], [37], [38] have been established to intervene with autophagy by both inhibiting autophagosome formation or rising lysosomal pH. [39], [40], [41] Nevertheless, most of those small molecule inhibitors lack tumor specificity, to not point out the issue in utterly blocking autophagy by these pathways. Innovatively, combining the destruction of lysosomes (the ultimate website of autophagic flux) and provider supplies appears to be a wise thought to dam autophagy.
Melittin is a 26 amino acid residue polypeptide (sequence: GIGAVLKVLTTGLPALISWIKRKRQQ) remoted type honey bee venom. [42] It may combine itself into cell membranes, and induce lipid membrane lysis by transmembrane pores formation, thus inflicting fast cell loss of life. [43] Though melittin has achieved some success in antitumor remedy and activation of immune responses, its non-specific toxicity limits its additional medical translation. Thus, pro-peptides (protein precursor) consisting of mum or dad peptides and cleavable stimuli-responsive linkers are enticing therapeutic compounds. Below regular physiological situations, they continue to be inactive, while the unique types of lively peptides might be restored by linker cleavage or degradation in response to particular biochemical indicators similar to hypoxia, weak acidity, or overexpressed enzymes, and so on., within the tumor microenvironment (TME). It has been reported that legumain is a extremely up-regulated lysosomal protease in stable tumors, which may chew off amino acids of protein chains to carry out its protein-cutting perform. [44], [45] Accordingly, melittin pro-peptide (P-ML) was ready by attaching an endoprotease legumain particular substrate, alanine-alanine-asparagine (AAN) residues, into its host spine (sequence: GIGAVLK(AAN)VLTTGLPALISWIK(AAN)RK(AAN)RQQ). On this design, the lipid membrane lysis exercise of melittin might be restored by selective recognition and cleavage of masked AAN residues by legumain. Nevertheless, it’s almost not possible to load such a big macromolecular melittin pro-protein into conventional mesoporous and microporous SAzymes supply programs.
Herein, a novel nanobee (carrying P-ML derived from bees) has been constructed for synergistic most cancers remedy. Detailly, totally different from beforehand reported SAzymes with tiny mesopore and micropore dimension, we synthesized large-pore mesoporous iron single-atom nanozyme (Fe SAzyme) with Fe-N5 coordination construction as P-ML autos, named as FePM nanobee (Scheme 1a). The remoted Fe atoms coordinated to the nitrogen in N-doped carbon framework demonstrates outstanding glutathione oxidase (GSHOx), and peroxidase (POD) and oxidase (OXD) mimicking actions. The outstanding catalytic exercise of Fe SAzyme is because of its Fe-N5 lively websites, that are analogous to the axial ligand coordination heme of pure oxidoreductases. Moreover, the amorphous carbon assist of Fe SAzyme endows it with important light-to-heat conversion efficiency. Consequently, Fe SAzyme can harm cytoplasmic parts to induce most cancers cells apoptosis and ferroptosis by synergistic lipid peroxide (LPO) accumulation, CDT and PTT. Nevertheless, the above therapeutic course of can be constantly accompanied by cell self-protective autophagy, thereby inhibiting the therapeutic impact (Scheme 1b). Happily, Fe SAzyme@melittin pro-peptide (FePM) enter cells by endocytosis and are entrapped in endo/lysosomes, the place the P-ML might be acknowledged and cleaved by over-expressed legumain in lysosomes. Then, the activated melittin can fuse with the lysosomal membrane, disrupting the lysosomes and thus inhibiting autophagy. On this case, bolstered therapeutic impact might be achieved by restraining self-protective autophagy. Our experimental outcomes reveal that Fe SAzyme-based ferroptosis, PTT and CDT along side TME-activated melittin-based autophagy inhibition exhibits considerably enhanced antitumor therapeutic impact. The FePM nanobee achieves the maximal toxicity to tumor cells and the minimal negative effects to regular tissues. General, the design of FePM nanobee takes SAzymes based mostly therapeutic impact to a brand new stage, which additionally affords an progressive SAzymes-based platform for the loading of macromolecular protein medicine.