Cyclic Naphthalene Diimide with a Ferrocene Moiety as a Redox-Active Tetraplex-DNA Ligand

Synthesis, DNA binding of bis-naphthyl ferrocene derivatives and the application as new electroactive indicators for DNA biosensor

A series of bis-naphthyl ferrocene derivatives were synthesized and characterized. Based on the results obtained from UV-visible absorption titration and ethidium bromide (EB) displacement experiments, it was observed that the synthesized compounds exhibited a strong binding ability to dsDNA. In comparison to the viscosity curve of EB, the tested compounds demonstrated a bisintercalation binding mode when interacting with CT-DNA. Differential pulse voltammetry (DPV) was employed to assess the binding specificity of these indicators towards ssDNA and dsDNA. All tested indicators displayed more pronounced signal differences before and after hybridization between probe nucleic acids and target nucleic acids compared to Methylene Blue (MB). Among the evaluated compounds, compound 3j containing an ether chain showed superior performance as an indicator, making it suitable for constructing DNA-based biosensors. Under optimized conditions including probe ssDNA concentration and indicator concentration, this biosensor exhibited good sensitivity, reproducibility, stability, and selectivity. The limit of detection was calculated as 4.53 × 10-11 mol/L. Furthermore, when utilizing 3j as the indicator in serum samples, the biosensor achieved satisfactory recovery rates for detecting the BRCA1 gene.

Paclitaxel Overload Supramolecular Oxidative Stress Nanoamplifier with a CDK12 Inhibitor for Enhanced Cancer Therapy

Combination therapy has emerged as a promising approach for treating tumors, although there is room for improvement. This study introduced a novel strategy that combined the enhancement of apoptosis, ferroptosis, and DNA damage to improve therapeutic outcomes for prostate cancer. Specifically, we have developed a supramolecular oxidative stress nanoamplifier, which was comprised of β-cyclodextrin, paclitaxel, and ferrocene-poly(ethylene glycol). Paclitaxel within the system disrupted microtubule dynamics, inducing G2/M phase arrest and apoptosis. Concurrently, ferrocene utilized hydrogen peroxide to generate toxic hydroxyl radicals in cells through the Fenton reaction, triggering a cascade of reactive oxygen species expansion, reduction of glutathione levels, lipid peroxidation, and ferroptosis. The increased number of hydroxyl radicals and the inhibitory effect of THZ531 on DNA repair mechanisms exacerbated DNA damage within tumor cells. As expected, the supramolecular nanoparticles demonstrated excellent drug delivery ability to tumor cells or tissues, exhibited favorable biological safety in vivo, and enhanced the killing effect on prostate cancer.

Contemporary Developments in Ferrocene Chemistry: Physical, Chemical, Biological and Industrial Aspects

Ferrocenyl-based compounds have many applications in diverse scientific disciplines, including in polymer chemistry as redox dynamic polymers and dendrimers, in materials science as bioreceptors, and in pharmacology, biochemistry, electrochemistry, and nonlinear optics. Considering the horizon of ferrocene chemistry, we attempted to condense the neoteric advancements in the synthesis and applications of ferrocene derivatives reported in the literature from 2016 to date. This paper presents data on the progression of the synthesis of diverse classes of organic compounds having ferrocene scaffolds and recent developments in applications of ferrocene-based organometallic compounds, with a special focus on their biological, medicinal, bio-sensing, chemosensing, asymmetric catalysis, material, and industrial applications.

A direct approach toward investigating DNA-ligand interactions via surface-enhanced Raman spectroscopy combined with molecular dynamics simulations

Small molecules that interfere with DNA replication can trigger genomic instability, which makes these molecules valuable in the search for anticancer drugs. Thus, interactions between DNA and its ligands at the molecular level are of great significance. In the present study, a new method based on surface-enhanced Raman spectroscopy (SERS) combined with molecular dynamics simulations has been proposed for analyzing the interactions between DNA and its ligands. The SERS signals of DNA hairpins (ST: d(CGACCAACGTGTCGCCTGGTCG), AP1: d(CGCACAACGTGTCGCCTGTGCG)), pure argininamide, and their complexes, were obtained, and the characteristic peak sites of the DNA secondary structure and argininamide ligand-binding region were analyzed. Molecular dynamics calculations predicted that argininamide binds to the 8C and 9G bases of AP1 via hydrogen bonding. Our method successfully detected the changes of SERS fingerprint peaks of hydrogen bonds and bases between argininamide and DNA hairpin bases, and their binding sites and action modes were consistent with the predicted results of the molecular dynamics simulations. This SERS technology combined with the molecular dynamics simulation detection platform provides a general analysis tool, with the advantage of effective, rapid, and sensitive detection. This platform can obtain sufficient molecular level conformational information to provide avenues for rapid drug screening and promote progress in several fields, including targeted drug design.

Ferroptosis-Enhanced Cancer Immunity by a Ferrocene-Appended Iridium(III) Diphosphine Complex

Ferroptosis is a programmed cell death pathway discovered in recent years, and ferroptosis-inducing agents have great potential as new antitumor candidates. Here, we report a Ir(III) complex (Ir1) containing a ferrocene-modified diphosphine ligand that localizes in lysosomes. Under the acidic environments of lysosomes, Ir1 can effectively catalyze Fenton reaction, produce hydroxyl radicals, induce lipid peroxidation, down-regulate glutathione peroxidase 4, and induce ferroptosis. RNA sequencing analysis shows that Ir1 can significantly affect pathways related to ferroptosis and cancer immunity. Accordingly, Ir1 can induce immunogenic cells death and suppress tumor growth in vitro, regulate T cell activity and immune microenvironments in vivo. In conclusion, we show the potential of small molecules with ferroptosis-inducing capabilities for effective cancer immunotherapy.

Disentangling the Structure-Activity Relationships of Naphthalene Diimides as Anticancer G-Quadruplex-Targeting Drugs

In the context of developing efficient anticancer therapies aimed at eradicating any sort of tumors, G-quadruplexes represent excellent targets. Small molecules able to interact with G-quadruplexes can interfere with cell pathways specific of tumors and common to all cancers. Naphthalene diimides (NDIs) are among the most promising, putative anticancer G-quadruplex-targeting drugs, due to their ability to simultaneously target multiple G-quadruplexes and their strong, selective in vitro and in vivo anticancer activity. Here, all the available biophysical, biological, and structural data concerning NDIs targeting G-quadruplexes were systematically analyzed. Structure–activity correlations were obtained by analyzing biophysical data of their interactions with G-quadruplex targets and control duplex structures, in parallel to biological data concerning the antiproliferative activity of NDIs on cancer and normal cells. In addition, NDI binding modes to G-quadruplexes were discussed in consideration of the structures and properties of NDIs by in-depth analysis of the available structural models of G-quadruplex/NDI complexes.

Detection of Tetraplex DNA and Detection by Tetraplex DNA

G-quardruplex (G4) DNA forms through the gathering together of G-quartet planes formed with four guanine (G) bases. G4 DNA stabilizes with potassium ions (K⁺) by coordination with the G-quartet center. Fluorometric G4 DNA carrying the fluorescence resonance energy transfer (FRET) chromophore pair at both termini has been applied for the fluorometric sensing or imaging of K⁺ under a homogeneous aqueous medium. This system has realized non-conventional K⁺ selectivity over the sodium ion (Na⁺). The selectivity of the fluorescence G4 was converted to Na⁺ from K⁺ with a modification of its sequence. On the other hand, G4 DNA detection has been achieved in terms of cancer diagnosis because of a strong relationship of G4 DNA and cancer development. Ligands interacting with G4 are expected to have anti-cancer potential. In addition, fluorometric G4 ligands have been developed and tested as tools for the dynamic monitoring of G4 in living cells. Moreover, fluorometric G4 DNA has been utilized to evaluate the G4 ligand performance.

Naphthalene diimide–amino acid conjugates as novel fluorimetric and CD probes for differentiation between ds-DNA and ds-RNA

Two novel unnatural amino acids, prepared by linking a dicationic purple-coloured and fluorescent naphthalene diimide (NDI) at core position to amino acid side chains of variable length, strongly interacted with ds-DNA/RNA by threading intercalation. Different from a reference NDI dye with identical visible range absorbance (520–540 nm) and Stokes shifts in emission (+60 nm, quantum yield > 0.2), only these amino acid–NDI conjugates showed selective fluorimetric response for GC-DNA in respect to AT(U)-polynucleotides. The DNA/RNA binding-induced circular dichroism (ICD) response of NDI at 450–550 nm strongly depended on the length and rigidity of the linker to the amino acid unit, which controls the orientation of the NDI unit inside within the intercalative binding site. The ICD selectivity also depends on the type of polynucleotide, thus the studied NDI dyes act as dual fluorimetric/ICD probes for sensing the difference between here used GC-DNA, AT-DNA and AU-RNA.

Microwave-Assisted Neat Synthesis of a Ferrocene Appended Phenolphthalein Diyne: A Designed Synthetic Scaffold for Hg2+ Ion

A C₂-symmetric internally conjugated 1,3-dialkyne system 5, containing phenolphthalein as a fluorophore and ferrocene as a redox moiety, has been synthesized via a microwave-assisted synthetic procedure. Compound 5 was synthesized by Cu-catalyzed Glaser-Hay coupling using a microwave reactor in neat condition for the first time. Compound 5 was found to be highly selective toward Fe³⁺, Cu²⁺, and Hg²⁺ ions via multichannels. Interestingly, Fe³⁺ and Cu²⁺ ions simply promote the oxidation of ferrocene unit to ferrocenium ion without binding to the receptor, whereas Hg²⁺ binds with the receptor 5 (ΔE_1/2 = 71 mV). The oxidation and binding phenomena were investigated by optical and electrochemical analyses. Furthermore, the binding site of Hg²⁺ ion with our designed probe was confirmed by ¹H, ¹³C NMR and IR titrations, which indicated that conjugated dialkyne unit interacts with Hg²⁺ ion by a favorable soft-soft interaction. Both receptor 5 and its metal complex, [5·2Hg²⁺], are stable in the physiological pH range (pH = 6-7) and thermally stable up to 78 °C. The experimental results of metal binding have been further supported by quantum chemical calculations (DFT), which explore the favorable geometry of the free ligand as well as its Hg²⁺ complex.