As a basic structure of most polypyridinal metal complexes, [Ru(bpy)3]2+, has the advantages of simple structure, facile synthesis and high yield, which has great potential for scientific research and application. However, sonodynamic therapy (SDT) performance of [Ru(bpy)3]2+ has not been investigated so far. SDT can overcome the tissue-penetration and phototoxicity problems compared to photodynamic therapy. Here, we report that [Ru(bpy)3]2+ is a highly potent sonosensitizer and sonocatalyst for sonotherapy in vitro and in vivo. [Ru(bpy)3]2+ can produce singlet oxygen (1O2) and sono-oxidize endogenous 1,4-dihydronicotinamide adenine dinucleotide (NADH) under ultrasound (US) stimulation in cancer cells. Furthermore, [Ru(bpy)3]2+ enables effective destruction of mice tumors, and the therapeutic effect can reach deep tissues over 10 cm under US irradiation. This work paves a way for polypyridinal metal complexes to be applied to the noninvasive precise sonotherapy of cancer.

Due to conventional photodynamic therapy encountering serious problems of phototoxicity and low tissue-penetrating depth of light, other dynamic therapy-based therapeutic methods such as sonodynamic therapy (SDT) are expected to be developed. To improve the therapeutic response to SDT, more effective sonosensitizers are imperative. In this study, a novel water-soluble iridium­(III)-porphyrin sonosensitizer (IrTMPPS) was synthesized and used for SDT. IrTMPPS generated ample singlet oxygen (1O2) under US irradiation and especially showed distinguished US-activatable abilities at more than 10 cm deep-tissue depths. Interestingly, under US irradiation, IrTMPPS sonocatalytically oxidized intracellular NADH, which would enhance SDT efficiency by breaking the redox balance in the tumor. Moreover, IrTMPPS displayed great sonocytotoxicity toward various cancer cells, and in vivo experiments demonstrated efficient tumor inhibition and anti-metastasis to the lungs in the presence of IrTMPPS and US irradiation. This report gives a novel idea of metal-based sonosensitizers for sonotherapy by fully taking advantage of non-invasiveness, water solubility, and deep tumor therapy.

The rapid efflux of Pt‐based chemotherapeutics by cancer cells is one of the major causes of drug resistance in clinically available drugs. Therefore, both the high cellular uptake as well as adequate retention efficiency of an anticancer agent are important factors to overcome drug resistance. Unfortunately, rapid and efficient quantification of metallic drug concentration in individual cancer cells still remains a tricky problem. Herein, with the help of newly developed single cell inductively coupled plasma mass spectrometry (SC‐ICP‐MS), we have found that the well‐known Ru(II)‐based complex, Ru3, displayed remarkable intracellular uptake and retention efficiency in every single cancer cell with high photocatalytic therapeutic activity to overcome cisplatin resistance. Moreover, Ru3 has shown sensational photocatalytic anticancer properties with excellent in‐vitro and in‐vivo biocompatibility under light exposure.

Four photo‐catalysts of the general formula [Ir(CO6/ppy)2(L)]Cl where CO6=coumarin 6 (Ir1–Ir3), ppy=2‐phenylpyridine (Ir4), L=4′‐(3,5‐di‐tert‐butylphenyl)‐2,2′ : 6′,2′′‐terpyridine (Ir1), 4′‐(3,5‐bis(trifluoromethyl)phenyl)‐2,2′ : 6′,2′′‐terpyridine (Ir2 and Ir4), and 4‐([2,2′ : 6′,2′′‐terpyridin]‐4′‐yl)‐N,N‐dimethylaniline (Ir3) were synthesized and characterized. These photostable photo‐catalysts (Ir1–Ir3) showed strong visible light absorption between 400–550 nm. Upon light irradiation (465 and 525 nm), Ir1–Ir3 generated singlet oxygen and induced rapidly photo‐catalytic oxidation of cellular coenzymes NAD(P)H. Ir1–Ir3 showed time‐dependent cellular uptake with excellent intracellular retention efficiency. Upon green light irradiation (525 nm), Ir2 provided a much higher photo‐index (PI=793) than the clinically used photosensitizer, 5‐aminolevulinicacid (5‐ALA, PI>30) against HeLa cancer cells. The observed necro‐apoptotic anticancer activity of Ir2 was due to the Ir2 triggered photo‐induced intracellular redox imbalance (by NAD(P)H oxidation and ROS generation) and change in the mitochondrial membrane potential. Remarkably, Ir2 showed in vivo photo‐induced catalytic anticancer activity in mouse models.