Anti-toxoplasma activity and DNA-binding of copper(II) and zinc(II) coordination compounds with 5-nitroimidazole-based ligands.

Tetrahedral copper(II) and zinc(II) coordination compounds from 5-nitroimidazole derivatives, viz. 1-(2-chloroethyl)-2-methyl-5-nitroimidazole (cenz) and ornidazole 1-(3-chloro-2-hydroxypropyl)-2-methyl-5-nitroimidazole (onz), were synthesized and spectroscopically characterized. Their molecular structures were determined by X-ray diffraction studies. The complexes [Cu(onz)2X2], [Zn(onz)2X2], [Cu(cenz)2X2] and [Zn(cenz)2X2] (X- = Cl, Br), are stable in solution and exhibit positive LogD7.4 values that are in the range for molecules capable of crossing the cell membrane via passive difussion. Their biological activity against Toxoplasma gondi was investigated, and IC50 and lethal dose (LD50) values were determined. The ornidazole copper(II) compounds showed very good antiparasitic activity in its tachyzoite morphology. The interaction of the coordination compounds with DNA was examined by circular dichroism, fluorescence (using intercalating ethidium bromide and minor groove binding Hoechst 33258) and UV-Vis spectroscopy. The copper(II) compounds interact with the minor groove of the biomolecule, whereas weaker electrostatic interactions take place with the zinc(II) compounds. The spectroscopic data achieved for the two series of complexes (namely with copper(II) and zinc(II) as metal center) agree with the respective DNA-damage features observed by gel electrophoresis.

Steric hindrance, ligand ejection and associated photocytotoxic properties of ruthenium(II) polypyridyl complexes.

Two ruthenium(II) polypyridyl complexes were prepared with the {Ru(phen)2}2+ moiety and a third sterically non-hindering bidentate ligand, namely 2,2'-dipyridylamine (dpa) and N-benzyl-2,2'-dipyridylamine (Bndpa). Hence, complexes [Ru(phen)2(dpa)](PF6)2 (1) and [Ru(phen)2(Bndpa)](PF6)2 (2) were characterized and their photochemical behaviour in solution (acetonitrile and water) was subsequently investigated. Compounds 1 and 2, which do not exhibit notably distorted octahedral coordination environments, contrarily to the homoleptic "parent" compound [Ru(phen)3](PF6)2, experience two-step photoejection of the dpa and Bndpa ligand upon irradiation (1050-430 nm) for several hours. DNA-binding studies revealed that compounds 1 and 2 affect the biomolecule differently upon irradiation; while 2 solely modifies its electrophoretic mobility, complex 1 is also capable of cleaving it. In vitro cytotoxicity studies with two cancer-cell lines, namely A549 (lung adenocarcinoma) and A375 (melanoma), showed that both 1 and 2 are not toxic in the dark, while only 1 is significantly cytotoxic if irradiated, 2 remaining non-toxic under these conditions. Light irradiation of the complex cation [Ru(phen)2(dpa)]2+ leads to the generation of transient Ru species that is present in the solution medium for several hours, and that is significantly cytotoxic, ultimately producing non-toxic free dpa and [Ru(phen)(OH2)2]2+.

DNA-interacting properties of two analogous square-planar cis-chlorido complexes: copper versus palladium.

Two square-planar coordination compounds, namely [Cu(CPYA)Cl2] (1) and [Pd(CPYA)Cl2] (2), were prepared from the ligand 4-chloro-N-(pyridin-2-ylmethyl)aniline (CPYA) and two chloride salts, and were fully characterized, including by X-ray diffraction. Spectroscopic, electrophoretic and AFM studies revealed that the two isostructural compounds were interacting differently with DNA. In both cases, the initial interaction involves electrostatic contacts of the CPYA ligand in the minor groove (as suggested by molecular docking), but subsequent strong binding occurs with the palladium(II) complex 2, whereas the binding with the copper complex 1 is weaker and concentration dependent. The strong binding of 2 eventually leads to the cleavage of the double strand and the redox activity of 1 allows to oxidatively cleave the biomolecule.

Dual Effect of Prussian Blue Nanoparticles on Aß40 Aggregation: ß-Sheet Fibril Reduction and Copper Dyshomeostasis Regulation.

Alzheimer's disease (AD), affecting almost 50 million individuals worldwide, is currently the first cause of dementia. Despite the tremendous research efforts in the last decade, only four supportive or palliative drugs, namely, acetylcholinesterase (AChE) inhibitors donepezil, galantamine, and rivastigmine and the glutamate NMDA receptor antagonist memantine, are currently available. New therapeutic strategies are becoming prominent, such as the direct inhibition of amyloid formation or the regulation of metal homeostasis. In the present report, the potential use of Prussian blue (PB), a drug that is in the World Health Organization Model List of Essential Medicines, in AD treatment is demonstrated. Both in vitro and in cellulo studies indeed suggest that PB nanoparticles (PBNPs) are capable of reducing the formation of typical amyloid-ß fibers (detected by thioflavin T fluorescence) and restoring the usual amyloid fibrillation pathway via chelation/sequestration of copper, which is found in high concentrations in senile plaques.

Nanochaperone-Based Strategies to Control Protein Aggregation Linked to Conformational Diseases.

The generation of highly organized amyloid fibrils is associated with a wide range of conformational pathologies, including primarily neurodegenerative diseases. Such disorders are characterized by misfolded proteins that lose their normal physiological roles and acquire toxicity. Recent findings suggest that proteostasis network impairment may be one of the causes leading to the accumulation and spread of amyloids. These observations are certainly contributing to a new focus in anti-amyloid drug design, whose efforts are so far being centered on single-target approaches aimed at inhibiting amyloid aggregation. Chaperones, known to maintain proteostasis, hence represent interesting targets for the development of novel therapeutics owing to their potential protective role against protein misfolding diseases. In this minireview, research on nanoparticles that can either emulate or help molecular chaperones in recognizing and/or correcting protein misfolding is discussed. The nascent concept of "nanochaperone" may indeed set future directions towards the development of cost-effective, disease-modifying drugs to treat several currently fatal disorders.

Peptidic Scaffolds To Reduce the Interaction of Cu(II) Ions with ß-Amyloid Protein.

Competitive Cu(II)-binding studies have been carried out between five decapeptides (both acyclic and cyclic), namely C-Asp, C-Asn, O-Asp, ODPro-Asp, and O-Asn, and the Aß(1-16) and Aß(1-40) fragments. Conformational constraints in such peptidic scaffolds affect their copper-binding affinity, which can be tuned. In the present study, the ability of these peptides to compete with Aß has been assessed in vitro, with the objective to examine whether such soft chelating agents may be used to lessen the deleterious interaction of Cu(II) with Aß. Fluorescence spectroscopy, electron paramagnetic resonance, and mass spectrometry data show that the more constrained peptide, i.e., cyclic C-Asp, which displays a Cu(II)-binding affinity comparable to that of Aß, is the only potential metal-protein attenuating compound (MPAC) candidate. In vitro aggregation studies with Aß(1-40) reveal that C-Asp can hamper the formation of copper-stabilized oligomeric Aß species, through capturing the metal ion prior to its interaction with monomeric Aß. The present study shows that (cyclic) peptides, preorganized for Cu(II) binding, may be applied for the development of potential copper-Aß attenuating compounds.

Thiosemicarbazone Derivatives as Inhibitors of Amyloid-ß Aggregation: Effect of Metal Coordination.

Three thiosemicarbazone derivatives, namely 4-(dimethylamino)benzaldehyde 4,4-dimethylthiosemicarbazone (HL1), 4-(dimethylamino)benzaldehyde thiosemicarbazone (HL2), and 4-(dimethylamino)benzaldehyde 4-methylthiosemicarbazone (HL3), have been synthesized and characterized. The three palladium(II) complexes 1-3 were prepared respectively from HL1, HL2, and HL3. The crystal structures of two coordination compounds, namely Pd(L2)2 (2) and Pd(L3)2 (3), were obtained, which showed the expected square-planar environment for the metal centers. The ligand HL3 and the Pd(II) complexes 1-3, which are stable in buffered solutions containing up to 5% DMSO, exhibit remarkable inhibitory properties against the aggregation of amyloid-ß, reducing the formation of fibrils. HL1, HL3, 2, and 3 display IC50 values (i.e., the concentrations required to reduce Aß fibrillation by 50%) below 1 µM, lower that of the reference compound catechin (IC50 = 2.8 µM). Finally, in cellulo studies with E. coli cells revealed that the palladium(II) compounds are significantly more efficient than the free ligands in inhibiting Aß aggregation inside bacterial inclusion bodies, thus illustrating a beneficial effect of metal coordination.

Copper, dityrosine cross-links and amyloid-ß aggregation.

Copper is involved in Alzheimer's disease (AD) where it appears to affect the aggregation of amyloid-ß (Aß) and to catalyze the production of reactive oxygen species (ROS). Oxidative stress apparently produces Aß dimers that are covalently linked through two tyrosine residues. Such dityrosine cross-links are considered as potential markers of the disease and seem to be implicated in the pathological disorder. In the present study, pure o,o'-dityrosine (diY) was prepared enzymatically (with horseradish peroxidase; HRP), which was subsequently used to construct calibration lines aimed at quantifying nanomolar amounts of diY in reaction mixtures by fluorescence spectroscopy. Hence, diY concentrations down to 67 nM could be determined, which allowed to find that ca. 3% of dityrosine-bridged dimers of Aß(1-40) were produced after 3 days at 37 °C in the presence of copper and dihydrogen peroxide. These cross-linked dimers in the presence of copper(II) ions completely inhibit the typical aggregation of Aß, since ß sheets could not be detected applying the usual Thioflavin T (ThT) method. Furthermore, the use of a potent Cu(II) chelator, such as the ATCUN tripeptide, L-histidyl-L-alanyl-L-histidine (HAH), efficiently prevented the copper-mediated generation of ROS and the associated dityrosine-bridged Aß dimers, suggesting that such metal chelators may find future applications in the field of anti-AD drug design.

Efficient copper-based DNA cleavers from carboxylate benzimidazole ligands.

Four copper(II) coordination compounds from 2-benzimidazole propionic acid (Hbzpr) and 4-(benzimidazol-2-yl)-3-thiobutanoic acid (Hbztb) were synthesized and fully characterized by elemental analyses, electronic spectroscopy, FT-IR and mass spectrometry. The molecular structure for the four complexes was confirmed by single-crystal X-ray crystallography. The DNA-interacting properties of the two trinuclear and two mononuclear compounds were investigated using different spectroscopic techniques including absorption titration experiments, fluorescence spectroscopy and circular dichroism spectroscopy. Trinuclear [Cu3(bzpr)4(H2O)2](NO3)2·3H2O·CH3OH (2) and [Cu3(bzpr)4Cl2]·3H2O (3) bind to DNA through non-intercalative interactions, while for mononuclear [Cu(bzpr)2(H2O)]·2H2O (1) and [Cu(bztb)2]·2H2O (4), at minor concentrations in relation to the DNA, a groove binding interaction is favored, while at higher concentrations an intercalative mode is preferred. The nuclease properties of all complexes were studied by gel electrophoresis, which showed that they were able to cleave supercoiled plasmid DNA (form I) to the nicked form (form II). Compound 4 is even capable of generating linear form III (resulting from double-strand cleavage). The proposed mechanism of action involves an oxidative pathway (Fenton-type reaction), which produces harmful reactive species, like hydroxyl radicals.

Drastic Effect of the Peptide Sequence on the Copper-Binding Properties of Tripeptides and the Electrochemical Behaviour of Their Copper(II) Complexes.

The binding and electrochemical properties of the complexes CuII -HAH, CuII -HWH, CuII -Ac-HWH, CuII -HHW, and CuII -WHH have been studied by using NMR and UV/Vis spectroscopies, CV, and density functional calculations. The results obtained highlight the importance of the peptidic sequence on the coordination properties and, consequently, on the redox properties of their CuII complexes. For CuII -HAH and CuII -HWH, no cathodic processes are observed up to -1.2 V; that is, the complexes exhibit very high stability towards copper reduction. This behaviour is associated with the formation of very stable square-planar (5,5,6)-membered chelate rings (ATCUN motif), which enclose two deprotonated amides. In contrast, for non-ATCUN CuII -Ac-HWH, CuII -HHW complexes, simulations seem to indicate that only one deprotonated amide is enclosed in the coordination sphere. In these cases, the main electrochemical feature is a reductive irreversible one electron-transfer process from CuII to CuI , accompanied with structural changes of the metal coordination sphere and reprotonation of the amide. Finally, for CuII -WHH, two major species have been detected: one at low pH (<5), with no deprotonated amides, and another one at high pH (>10) with an ATCUN motif, both species coexisting at intermediate pH. The present study shows that the use of CV, using glassy carbon as a working electrode, is an ideal and rapid tool for the determination of the redox properties of CuII metallopeptides.

Highly Cytotoxic Ruthenium(II)-Arene Complexes from Bulky 1-Pyrenylphosphane Ligands.

In the present study, the potential anti-neoplastic properties of a series of ruthenium half-sandwich complexes of formula [Ru(η6-arene)Cl2(PR1R2(1-pyrenyl))] (η6-arene = p-cymene and R1 = R2 = methyl for 1; η6-arene = methylbenzoate and R1 = R2 = methyl for 2; η6-arene = p-cymene and R1 = R2 = phenyl for 3; η6-arene = methylbenzoate and R1 = R2 = phenyl for 4; η6-arene = p-cymene, R1 = methyl and R2 = phenyl for 5; η6-arene = methylbenzoate, R1 = methyl and R2 = phenyl for 6) have been investigated. The six structurally related organoruthenium(II) compounds have been prepared in good yields and fully characterized; the X-ray structures of three of them, i.e., 1, 2, and 4, were determined. Although the piano-stool compounds contain a large polycyclic aromatic moiety, viz. a 1-pyrenyl group, they do not appear to interact with DNA. However, all the piano-stool complexes show significant cytotoxic properties against five human cell lines, namely, lung adenocarcinoma (A549), melanoma (A375), colorectal adenocarcinoma (SW620), breast adenocarcinoma (MCF7), and nontumorigenic epithelial breast (MCF10A), with IC50 values in the micromolar range for most of them. In addition, the most active compound, i.e., 2, induces a remarkable decrease of cell viability, that is in the nanomolar range, against two human neuroblastoma cell lines, namely, SK-N-BE(2) and CHLA-90. Complexes 1-6 are all capable of inducing apoptosis, but with various degrees of magnitude. Whereas 1, 3, 5, and 6 have no effect on the cell cycle of A375 cells, 2 and 4 can arrest it at the G2/M phase; furthermore, 2 (which is the most efficient compound of the series) also stops the cycle at the S phase, behaving as the well-known anticancer agent cisplatin. Finally, 2 is able to inhibit/reduce the cell migration of neuroblastoma SK-N-BE(2) cells.

Histidine-Rich Oligopeptides To Lessen Copper-Mediated Amyloid-ß Toxicity.

Brain copper imbalance plays an important role in amyloid-ß aggregation, tau hyperphosphorylation, and neurotoxicity observed in Alzheimer's disease (AD). Therefore, the administration of biocompatible metal-binding agents may offer a potential therapeutic solution to target mislocalized copper ions and restore metallostasis. Histidine-containing peptides and proteins are excellent metal binders and are found in many natural systems. The design of short peptides showing optimal binding properties represents a promising approach to capture and redistribute mislocalized metal ions, mainly due to their biocompatibility, ease of synthesis, and the possibility of fine-tuning their metal-binding affinities in order to suppress unwanted competitive binding with copper-containing proteins. In the present study, three peptides, namely HWH, HK(C) H, and HAH, have been designed with the objective of reducing copper toxicity in AD. These tripeptides form highly stable albumin-like complexes, showing higher affinity for Cu(II) than that of Aß(1-40). Furthermore, HWH, HK(C) H, and HAH act as very efficient inhibitors of copper-mediated reactive oxygen species (ROS) generation and prevent the copper-induced overproduction of toxic oligomers in the initial steps of amyloid aggregation in the presence of Cu(II) ions. These tripeptides, and more generally small peptides including the sequence His-Xaa-His at the N-terminus, may therefore be considered as promising motifs for the future development of new and efficient anti-Alzheimer drugs.

Cobalt(III)-py2en systems as potential carriers of ß-ketoester-based ligands.

Two cobalt(III) complexes containing different ß-ketoesters, namely [CoIII(L1)(py2en)](ClO4)2·H2O (1) and [CoIII(L2)(py2en)](ClO4)2 (2) (py2en = N,N'-bis(pyridin-2-ylmethyl)ethylenediamine; L1- = methylacetoacetate; L2- = ethyl 4-chloroacetoacetate) have been prepared and investigated as prototypes of bioreductive prodrugs. The presence of ß-ketoester and py2en ligands in 1 and 2, as well as the perchlorate counterions, was supported by IR spectroscopy and CHN elemental analysis. The composition molecular structure of both complexes was confirmed by NMR spectroscopy and ESI mass spectrometry. Structural information was also obtained for 2via X-ray diffraction analysis. The redox properties indicate that 1 and 2 are suitable for reduction under biological conditions. Investigation of DNA-interacting suggest that 1 and 2 bind DNA via electrostatic forces. Both complexes may be employed as possible platforms for the delivery of biologically active compounds, since their reaction with ascorbic acid in PBS at pH 6.2 and 7.4 at 37°C results in the release of the ß-ketoester ligands upon Co(III)/Co(II) reduction.

Anti-Amyloid Drug Screening Methods Using Bacterial Inclusion Bodies.

Amyloid aggregation is linked to a number of human disorders that range from non-neurological illnesses such as type 2 diabetes to neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. The formation of insoluble protein aggregates with amyloid conformation inside bacteria, namely, in bacterial inclusion bodies, offers the possibility to use bacteria as simple models to study amyloid aggregation processes and potential effects of both anti-amyloid drugs and/or pro-aggregative compounds. This chapter describes fast, simple, inexpensive, highly reproducible, and tunable in vitro and in cellulo methods that use bacterial inclusion bodies as preliminary screening tools for anti-amyloid drugs.

Bis(cyanato-κN)bis-(5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine-κN)zinc.

In the title complex, [Zn(NCO)(2)(C(7)H(8)N(4))(2)], the Zn(II) ion exhibits a distorted tetra-hedral coordination geometry. The coordination environment is formed by two 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine (dmtp) ligands, coordinated through the N atom in position 3, and two cyanate anions inter-acting by their N atoms. Supra-molecular dimers are generated by stacking inter-actions between the pyrimidine rings of two ligands related by an inversion center [centroid-centroid distance = 3.5444 (18) Å].

Bis(7-amino-1,2,4-triazolo[1,5-a]pyrimidin-4-ium) bis-(oxalato-κO,O)cuprate(II) dihydrate.

The structure of the title ionic compound, (C(5)H(6)N(5))(2)[Cu(C(2)O(4))(2)]·2H(2)O, consists of a centrosymmetric copper(II) oxalate dianion, two monoprotonated mol-ecules of the adenine analog 7-amino-1,2,4-triazolo[1,5-a]pyrimidine (7atp) and two water mol-ecules of crystallization. The Cu(II) ion, located on an inversion center, exhibits a sligthly distorted square-planar coordination geometry, in which two oxalate anions bind in a bidentate fashion. The triazolopyrimidine ligand is protonated at the N atom in position 4, instead of its most basic N atom in position 3. This fact may be explained by the network stability, which is provided through the formation of a two-dimensional wave-like network parallel to (50[Formula: see text]) by N-H⋯O, O-H⋯N and O-H⋯O hydrogen bonds. These nets are further connected via C-H⋯O inter-actions.

4,7-Phenanthrolinium perchlorate-5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one-water (1/1/2).

The asymmetric unit of the title compound, C(12)H(9)N(2) (+)·ClO(4) (-)·C(6)H(6)N(4)O·2H(2)O, contains a monoprotonated 4,7-phenanthrolinium (47phen) cation, a perchlorate anion balancing its charge, a neutral mol-ecule of 5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one (HmtpO) and two inter-stitial water mol-ecules. In the crystal structure, the acidic H atoms of 47phenH(+) and HmtpO form strong hydrogen bonds with the water mol-ecules, which in turn act as hydrogen-bond donors, forming links between them and towards the carbonyl O atom of HmtpO, the non-protonated N atom of 47phen(+) and one of the O atoms of the anion.

Evaluation of cobalt(III) complexes as potential hypoxia-responsive carriers of esculetin.

Differentiation between hypoxic and normoxic tissues have been exploited for the development of selective chemotherapeutic agents. In this context, cobalt(III)-based coordination compounds have been designed and investigated as prospective hypoxia-responsive drug delivery systems. Three cobalt(III) complexes, namely [CoIII(esc)(py2en)]ClO4·(CH3OH)2 (1) [CoIII(esc)(TPA)]ClO4·3H2O (2) and [CoIII(bipy)2(esc)]ClO4·2.5H2O (3) (py2en = N,N'-bis(pyridin-2-ylmethyl)ethylenediamine, TPA = tris(2-pyridylmethyl)amine, bipy = 2,2'-bipyridine and esc = 6,7-dihydroxycoumarin or esculetin), were prepared and investigated as potential carriers of esculetin. The spectroscopic and electrochemical properties of 1-3 were investigated and compared. Reactions of the complexes with biologically relevant reducing agents, viz. ascorbic acid, cysteine and glutathione, were monitored spectroscopically for 24 h, in pH 6.2 and 7.4 PBS phosphate buffer saline (PBS) solutions at 37 °C, under air, argon and dioxygen atmospheres. Dissociation of esculetin was observed upon Co3+/Co2+ reduction preferably under hypoxic conditions, with more effective conversion rates for 3 > 2 > 1. These results illustrate the importance to modulate the Co3+/Co2+ redox potential through the donor-acceptor properties of the ancillary ligands. Complex 3 is cytotoxic against HCT-116 but not against HT-29 and HEK-293 cells. In addition, DNA-binding studies indicate that interactions of 1 and 3 with the biomolecule are electrostatic.

Bacterial Inclusion Bodies for Anti-Amyloid Drug Discovery: Current and Future Screening Methods.

Amyloid aggregation is linked to an increasing number of human disorders from nonneurological pathologies such as type-2 diabetes to neurodegenerative ones such as Alzheimer or Parkinson's diseases. Thirty-six human proteins have shown the capacity to aggregate into pathological amyloid structures. To date, it is widely accepted that amyloid folding/aggregation is a universal process present in eukaryotic and prokaryotic cells. In the last decade, several studies have unequivocally demonstrated that bacterial inclusion bodies - insoluble protein aggregates usually formed during heterologous protein overexpression in bacteria - are mainly composed of overexpressed proteins in amyloid conformation. This fact shows that amyloid-prone proteins display a similar aggregation propensity in humans and bacteria, opening the possibility to use bacteria as simple models to study amyloid aggregation process and the potential effect of both anti-amyloid drugs and pro-aggregative compounds. Under these considerations, several in vitro and in cellulo methods, which exploit the amyloid properties of bacterial inclusion bodies, have been proposed in the last few years. Since these new methods are fast, simple, inexpensive, highly reproducible, and tunable, they have aroused great interest as preliminary screening tools in the search for anti-amyloid (beta-blocker) drugs for conformational diseases. The aim of this mini-review is to compile recently developed methods aimed at tracking amyloid aggregation in bacteria, discussing their advantages and limitations, and the future potential applications of inclusion bodies in anti-amyloid drug discovery.

Assisted delivery of anti-tumour platinum drugs using DNA-coiling gold nanoparticles bearing lumophores and intercalators: towards a new generation of multimodal nanocarriers with enhanced action.

New gold and lipoic based nanocarriers for the delivery of platinum(ii) and platinum(iv) drugs are developed, which allow enhanced loading of the drug on the surface of the nanocarriers and release in a pH-dependent fashion, with superior release at lower pHs which are associated with many tumours. The conjugate nanoparticles and their conjugates enter cells rapidly (within 3 hours). They tend to cluster in vesicles and are also observed by light and electron microscopies in the cytoplasm, endoplasmic reticulum and nucleus. We further incorporate aminoanthraquinone units that are both fluorophores and DNA intercalators. This results in nanocarriers that after drug release will remain surface decorated with DNA-binders challenging the conventional design of the nanocarrier as an inert component. The outcome is nanocarriers that themselves have distinctive, remarkable and unusual DNA binding properties being able to bind and wrap DNA (despite their anionic charge) and provide enhanced cytotoxic activity beyond that conferred by the platinum agents they release. DNA coiling is usually associated with polycations which can disrupt cell membranes; anionic nanoparticles that can cause novel and dramatic effects on DNA may have fascinating potential for new approaches to in-cell nucleic acid recognition. Our findings have implications for the understanding and interpretation of the biological activities of nanoparticles used to deliver other DNA-binding drugs including clinical drug doxorubicin and its formulations.