Enhancing radiation-resistance and peroxidase-like activity of single-atom copper nanozyme via local coordination manipulation.

The inactivation of natural enzymes by radiation poses a great challenge to their applications for radiotherapy. Single-atom nanozymes (SAzymes) with high structural stability under such extreme conditions become a promising candidate for replacing natural enzymes to shrink tumors. Here, we report a CuN3-centered SAzyme (CuN3-SAzyme) that exhibits higher peroxidase-like catalytic activity than a CuN4-centered counterpart, by locally regulating the coordination environment of single copper sites. Density functional theory calculations reveal that the CuN3 active moiety confers optimal H2O2 adsorption and dissociation properties, thus contributing to high enzymatic activity of CuN3-SAzyme. The introduction of X-ray can improve the kinetics of the decomposition of H2O2 by CuN3-SAzyme. Moreover, CuN3-SAzyme is very stable after a total radiation dose of 500 Gy, without significant changes in its geometrical structure or coordination environment, and simultaneously still retains comparable peroxidase-like activity relative to natural enzymes. Finally, this developed CuN3-SAzyme with remarkable radioresistance can be used as an external field-improved therapeutics for enhancing radio-enzymatic therapy in vitro and in vivo. Overall, this study provides a paradigm for developing SAzymes with improved enzymatic activity through local coordination manipulation and high radioresistance over natural enzymes, for example, as sensitizers for cancer therapy.

Zeolitic Imidazolate Framework-8 (ZIF-8) as a Drug Delivery Vehicle for the Transport and Release of Telomerase Inhibitor BIBR 1532.

Telomerase is constitutively overexpressed in the majority of human cancers and telomerase inhibition provides a promising broad-spectrum anticancer therapeutic strategy. BIBR 1532 is a well-known synthetic telomerase inhibitor that blocks the enzymatic activity of hTERT, the catalytic subunit of telomerase. However, water insolubility of BIBR 1532 leads to low cellular uptake and inadequate delivery and thus, limits its anti-tumor effects. Zeolitic imidazolate framework-8 (ZIF-8) is considered as an attractive drug delivery vehicle for improved transport, release and anti-tumor effects of BIBR 1532. Herein, ZIF-8 and BIBR 1532@ZIF-8 were synthesized, respectively, and the physicochemical characterizations confirmed the successful encapsulation of BIBR 1532 in ZIF-8 coupled with an improved stability of BIBR 1532. ZIF-8 could alter the permeability of lysosomal membrane probably by the imidazole ring-dependent protonation. Moreover, ZIF-8 encapsulation facilitated the cellular uptake and release of BIBR 1532 with more accumulation in the nucleus. BIBR 1532 encapsulation with ZIF-8 triggered a more obvious growth inhibition of cancer cells as compared with free BIBR 1532. A more potent inhibition on hTERT mRNA expression, aggravated G0/G1 arrest accompanied with an increased cellular senescence were detected in BIBR 1532@ZIF-8-treated cancer cells. Our work has provided preliminary information on improving the transport, release and efficacy of water-insoluble small molecule drugs by using ZIF-8 as a delivery vehicle.

Engineering Single-Atom Iron Nanozymes with Radiation-Enhanced Self-Cascade Catalysis and Self-Supplied H2O2 for Radio-enzymatic Therapy.

Single-atom nanozymes (SAzymes), with individually isolated metal atom as active sites, have shown tremendous potential as enzyme-based drugs for enzymatic therapy. However, using SAzymes in tumor theranostics remains challenging because of deficient enzymatic activity and insufficient endogenous H2O2. We develop an external-field-enhanced catalysis by an atom-level engineered FeN4-centered nanozyme (FeN4-SAzyme) for radio-enzymatic therapy. This FeN4-SAzyme exhibits peroxidase-like activity capable of catalyzing H2O2 into hydroxyl radicals and converting single-site FeII species to FeIII for subsequent glutathione oxidase-like activity. Density functional theory calculations are used to rationalize the origin of the single-site self-cascade enzymatic activity. Importantly, using X-rays can improve the overall single-site cascade enzymatic reaction process via promoting the conversion frequency of FeII/FeIII. As a H2O2 producer, natural glucose oxidase is further decorated onto the surface of FeN4-SAzyme to yield the final construct GOD@FeN4-SAzyme. The resulting GOD@FeN4-SAzyme not only supplies in situ H2O2 to continuously produce highly toxic hydroxyl radicals but also induces the localized deposition of radiation dose, subsequently inducing intensive apoptosis and ferroptosis in vitro. Such a synergistic effect of radiotherapy and self-cascade enzymatic therapy allows for improved tumor growth inhibition with minimal side effects in vivo. Collectively, this work demonstrates the introduction of external fields to enhance enzyme-like performance of nanozymes without changing their properties and highlights a robust therapeutic capable of self-supplying H2O2 and amplifying self-cascade reactions to address the limitations of enzymatic treatment.