In Vitro and In Vivo Biological Activities of Dipicolinate Oxovanadium(IV) Complexes

The work is focused on anticancer properties of dipicolinate (dipic)-based vanadium(IV) complexes [VO(dipic)(N^∩N)] bearing different diimines (2-(1H-imidazol-2-yl)pyridine, 2-(2-pyridyl)benzimidazole, 1,10-phenanthroline-5,6-dione, 1,10-phenanthroline, and 2,2'-bipyridine), as well as differently 4,7-substituted 1,10-phenanthrolines. The antiproliferative effect of V(IV) systems was analyzed in different tumors (A2780, HCT116, and HCT116-DoxR) and normal (primary human dermal fibroblasts) cell lines, revealing a high cytotoxic effect of [VO(dipic)(N^∩N)] with 4,7-dimethoxy-phen (5), 4,7-diphenyl-phen (6), and 1,10-phenanthroline (8) against HCT116-DoxR cells. The cytotoxicity differences between these complexes can be correlated with their different internalization by HCT116-DoxR cells. Worthy of note, these three complexes were found to (i) induce cell death through apoptosis and autophagy pathways, namely, through ROS production; (ii) not to be cytostatic; (iii) to interact with the BSA protein; (iv) do not promote tumor cell migration or a pro-angiogenic capability; (v) show a slight in vivo anti-angiogenic capability, and (vi) do not show in vivo toxicity in a chicken embryo.

A polydopamine-gated biodegradable cascade nanoreactor for pH-triggered and photothermal-enhanced tumor-specific nanocatalytic therapy

Despite the great potential of cascade catalytic reactions in tumor treatment, uncontrolled catalytic activities in vivo lead to inevitable off-target toxicity to normal tissues, which greatly hampers their clinical conversion. Herein, an intelligent cascade nanoreactor (hMnO₂-Au@PDA, hMAP) was constructed by depositing glucose oxidase (GOx)-mimicking ultrasmall gold nanoparticles (Au NPs) into honeycomb-shaped manganese oxide (hMnO₂) nanostructures and then coating them with polydopamine (PDA) to achieve pH-responsive and photothermal-enhanced nanocatalytic therapy. Upon exposure to the mild acidic tumor microenvironment (TME), the PDA gatekeeper would collapse, and the inner hMnO₂ could simultaneously deplete glutathione (GSH) and generate Mn²⁺, while a considerable amount of H₂O₂ produced from the oxidation of glucose by GOx-mimicking Au NPs could accelerate the Mn²⁺-mediated Fenton-like reaction, yielding sufficient highly toxic ˙OH. More importantly, the pH-responsive cascade reaction between Au NPs and hMnO₂ could be further enhanced by localized hyperthermia induced from PDA under near-infrared (NIR) laser irradiation, thereby inducing significant cell apoptosis in vitro and tumor inhibition in vivo. This work provided a promising paradigm by innovatively designing a TME-responsive and photothermal-enhanced cascade catalytic nanoreactor for safe and efficient cancer therapy.

Spontaneous conversions of glutamine, histidine and arginine into α-hydroxycarboxylates with NH4VO3 or V2O5

Glutamine gets transformed to 2-hydroxy-5-oxoproline with NH₄VO₃ in a neutral solution as a product of 2,2'-bipyridine oxidovanadium(v) 2-hydroxy-5-oxoproline [V^V₂O₃(hop)₂(bpy)₂]·7H₂O [1, H₂hop = 2-hydroxy-5-oxoproline] with yields of 65.6%. Similarly, histidine and arginine are converted into the corresponding α-hydroxycarboxylates as 2,2'-bipyridine oxidovanadium(iv) 3-(1H-imidazolyl-5-yl)-2-hydroxyacrylate [V^IV₂O₂(imha)₂(bpy)₂]·bpy [2, H₂imha = 3-(1H-imidazolyl-5-yl)-2-hydroxyacrylic acid] and guanidinium oxidovanadium(v) 1-(aminoiminomethyl)-2-hydroxyproline (CN₃H₆)[V^VO₂(Haimhp)₂]·2H₂O [3, H₂aimhp = 1-(aminoiminomethyl)-2-hydroxyproline] with V₂O₅ in low yields respectively, where an aggregate of oxidovanadium(v) arginine (H₂arg)_n(V^VO₃)_n·½nH₂O (4, Harg = arginine) has been isolated preferentially in an initial experiment for 3. α-Hydroxycarboxylates chelate bidentately with vanadium viaα-alkoxy and α-carboxy groups in 1-3, as observed from structural analyses. Their racemizations have been observed after the conversions. There is no coordination in 4 based on solid-state ¹³C NMR spectra, and only strong hydrogen bonds exist in the anion chains (V^VO₃)^- and protonated arginines. 1 and 4 were fully characterized by elemental analysis, UV-vis, IR and solid-state ¹³C NMR spectroscopies, TG and X-ray structural analyses, and theoretical bond valence calculations (BVS). The conversions of glutamine, histidine and arginine occur spontaneously in a solution under ambient conditions.