New platinum(II) and palladium(II) complexes with substituted terpyridine ligands: synthesis and characterization, cytotoxicity and reactivity towards biomolecules.

A series of palladium(II) (1-3) and platinum(II) chloride complexes (4 and 5) with 2,2':6',2″-terpyridine (terpy) derivatives substituted at the 4' position, was synthesized and fully characterized. Single crystal X-ray diffraction analysis of complexes 2, 3 and 5 showed tridentate coordination of the 4'-substituted terpyridine (terpy) ligands to the metal center. Moreover, in vitro cytotoxic activity of these complexes toward a panel of human cancer cell lines (lung cancer A549, colorectal cancer HCT116, ovarian cancer IGROV-1) and toward normal cell line HDF (dermal fibroblast) was determined by Trypan Blue exclusion assay. Overall, the tested compounds manifested a relevant cytotoxicity for the selected cancer cell lines with complex 4 also showing a modest cytotoxicity on the normal cell lines. To better understand the mode of action of these metal complexes, their reactivity with three model proteins, i.e. hen egg white lysozyme (HEWL), cytochrome c (cyt c) and ribonuclease A (RNase A) were comparatively investigated through ESI-MS analysis. The results highlighted a different behavior between the two series of complexes being platinum compounds more reactive toward RNase and cyt c than palladium compounds. Based on the obtained results, it is proposed that in presence of RNase A and cyt c, the platinum complexes undergo activation through release of labile ligands followed by binding to the protein. In contrast, palladium complexes revealed a far lower reactivity implying the likely occurrence of a different mechanism of action.

Protein delivery into cells using inorganic nanoparticle-protein supramolecular assemblies.

The delivery of proteins into cells is a potential game changer for a wide array of therapeutic purposes, including cancer therapy, immunomodulation and treatment of inherited diseases. In this review, we present recently developed nanoassemblies for protein delivery that utilize strategies that range from direct assembly, encapsulation and composite formation. We will discuss factors that affect the efficacy of nanoassemblies for delivery from the perspective of both nanoparticles and proteins. Challenges in the field, particularly achieving effective cytosolar protein delivery through endosomal escape or evasion are discussed.

In Vivo Delivery of CRISPR/Cas9 for Therapeutic Gene Editing: Progress and Challenges.

The successful use of clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9-based gene editing for therapeutics requires efficient in vivo delivery of the CRISPR components. There are, however, major challenges on the delivery front. In this Topical Review, we will highlight recent developments in CRISPR delivery, and we will present hurdles that still need to be overcome to achieve effective in vivo editing.

Interactions of the organogold(III) compound Aubipyc with the copper chaperone Atox1: a joint mass spectrometry and circular dichroism investigation.

The so called "copper trafficking system" in mammalian cells is primarily devoted to the regulation of copper transport and homeostasis. This system, now well characterized, consists of a few strictly interconnected proteins that assist copper entrance inside cells and then promote metal transfer and delivery to essential copper-dependent cellular proteins (Boal and Rosenzweig 2009a; Banci et al., Mol Life Sci 67:2563-2589, 2010). Yet, the "copper trafficking system" may also facilitate the entrance inside cells of non-physiological metal species such as clinically established platinum drugs. ESI and MALDI MS methods are exploited here to characterize the interactions occurring between the experimental anticancer organogold(III) drug, Aubipyc, and the copper chaperone Atox1, a key protein of the copper trafficking system. The nature of the adducts that are formed when reacting Aubipyc with Atox1 is elucidated in detail. Characterization of the Aubipyc/Atox1 system is further supported by circular dichroism experiments. Binding competitions with mercury and bismuth ions were also explored. The relevance and the biological implications of the present results are discussed.

Chemistry and biology of two novel gold(I) carbene complexes as prospective anticancer agents.

Two novel gold carbene compounds, namely, chlorido (1-butyl-3-methyl-imidazole-2-ylidene) gold(I) (1) and bis(1-butyl-3-methyl-imidazole-2-ylidene) gold(I) (2), were prepared and characterized as prospective anticancer drug candidates. These compounds consist of a gold(I) center linearly coordinated either to one N-heterocyclic carbene (NHC) and one chloride ligand (1) or to two identical NHC ligands (2). Crystal structures were solved for both compounds, the resulting structural data being in good agreement with expectations. We wondered whether the presence of two tight carbene ligands in 2 might lead to biological properties distinct from those of the monocarbene complex 1. Notably, in spite of their appreciable structural differences, these two compounds manifested similarly potent cytotoxic actions in vitro when challenged against A2780 human ovarian carcinoma cells. In addition, both were able to overcome resistance to cisplatin in the A2780R line. Solution studies revealed that these gold carbene complexes are highly stable in aqueous buffers at physiological pH. Their reactivity with proteins was explored: no adduct formation was detected even upon a long incubation with the model proteins cytochrome c and lysozyme; in contrast, both compounds were able to metalate, to a large extent, the copper chaperone Atox-1, bearing a characteristic CXXC motif. The precise nature of the resulting gold-Atox-1 adducts was elucidated through ESI-MS analysis. On the basis of these findings, it is proposed that the investigated gold(I) carbene compounds are promising antiproliferative agents warranting a wider pharmacological evaluation. Most likely these gold compounds produce their potent biological effects through selective metalation and impairment of a few crucial cellular proteins.

Treatment of Three Ferrets Diagnosed with Ferret Systemic Coronaviral Disease Using the Nucleoside Analogue GS-441524.

Ferret Systemic Coronaviral Disease (FSCD) is a systemic disease caused by ferret systemic coronavirus, which is considered lethal in most of the ferrets that are affected by it. To our knowledge, no treatment has been shown to be effective against FSCD in vivo, and most of the ferrets are euthanized or die after the development of clinical disease. GS-441524 has been shown to be effective in successfully treating cats with Feline Infectious Peritonitis (FIP), a disease that shares similarities with FSCD. However, to our knowledge, treatment with GS-441524 has not been reported for the treatment of FSCD in ferrets. Here, we describe three cases of ferrets diagnosed with FSCD successfully cured utilizing oral GS-441524. FSCD may be effectively treated following similar protocols utilized for feline infectious peritonitis in cats.

Engineered Polymer-siRNA Polyplexes Provide Effective Treatment of Lung Inflammation.

Uncontrolled inflammation is responsible for acute and chronic diseases in the lung. Regulating expression of pro-inflammatory genes in pulmonary tissue using small interfering RNA (siRNA) is a promising approach to combatting respiratory diseases. However, siRNA therapeutics are generally hindered at the cellular level by endosomal entrapment of delivered cargo and at the organismal level by inefficient localization in pulmonary tissue. Here we report efficient anti-inflammatory activity in vitro and in vivo using polyplexes of siRNA and an engineered cationic polymer (PONI-Guan). PONI-Guan/siRNA polyplexes efficiently deliver siRNA cargo to the cytosol for highly efficient gene knockdown. Significantly, these polyplexes exhibit inherent targeting to inflamed lung tissue following intravenous administration in vivo. This strategy achieved effective (>70%) knockdown of gene expression in vitro and efficient (>80%) silencing of TNF-α expression in lipopolysaccharide (LPS)-challenged mice using a low (0.28 mg/kg) siRNA dosage.

Protein metalation by metal-based drugs: reactions of cytotoxic gold compounds with cytochrome c and lysozyme.

Protein metalation processes are crucial for the mechanism of action of several anticancer metallodrugs and warrant deeper characterisation. We have explored the reactions of three cytotoxic gold(III) compounds-namely [(bipy(2Me))(2)Au(2)(µ-O)(2)][PF(6)](2) (where bipy(2Me) is 6,6'-dimethyl-2,2'-bipyridine) (Auoxo6), [(phen(2Me))(2)Au(2)(µ-O)(2)][PF(6)](2) (where phen(2Me) is 2,9-dimethyl-1,10-phenanthroline) (Au(2)phen) and [(bipy(dmb)-H)Au(OH)][PF(6)] [where bipy(dmb)-H is deprotonated 6-(1,1-dimethylbenzyl)-2,2'-bipyridine] (Aubipyc)-with two representative model proteins, i.e. horse heart cytochrome c and hen egg white lysozyme, through UV-visible absorption spectroscopy and electrospray ionisation mass spectrometry (ESI MS) to characterise the inherent protein metalation processes. Notably, Auoxo6 and Au(2)phen produced stable protein adducts where one or more "naked" gold(I) ions are protein-coordinated; very characteristic is the case of cytochrome c, which upon reaction with Auoxo6 or Au(2)phen preferentially forms "tetragold" adducts with four protein-bound gold(I) ions. In turn, Aubipyc afforded monometalated protein adducts where the structural core of the gold(III) centre and its +3 oxidation state are conserved. Auranofin yielded protein derivatives containing the intact auranofin molecule. Additional studies were performed to assess the role played by a reducing environment in protein metalation. Overall, the approach adopted provides detailed insight into the formation of metallodrug-protein derivatives and permits trends, peculiarities and mechanistic details of the underlying processes to be highlighted. In this respect, electrospray ionisation mass spectrometry is a very straightforward and informative research tool. The protein metalation processes investigated critically depend on the nature of both the metal compound and the interacting protein and also on the solution conditions used; thus, predicting with accuracy the nature and the amounts of the adducts formed for a given metallodrug-protein pair is currently extremely difficult.

Gel-phase microdomains and lipid rafts in monolayers affect the redox properties of ubiquinone-10.

The redox properties of ubiquinone-10 (UQ) were examined in monolayers of mixtures of dioleoylphosphatidylcholine, palmitoylsphingomyelin, and cholesterol of different compositions, self-assembled on a mercury electrode, over the pH range from 7.5 to 9.5. A detailed analysis of the cyclic voltammograms of UQ in the above lipid environments points to a mechanism consisting of an elementary electron transfer step followed by two protonation (or deprotonation) steps in quasiequilibrium and by a further electron transfer step. In a lipid environment of solid-ordered (s(o)) microdomains in a liquid-disordered (l(d)) matrix, electron transport across the lipid monolayer takes place in the l(d) phase. In a pure s(o) phase, UQ tends to segregate into UQ-rich pools, exhibiting reversible electron transfer steps. In a lipid environment consisting of liquid-ordered (l(o)) microdomains (lipid rafts) in an l(d) matrix, UQ molecules tend to localize along the edge of the lipid rafts. However, in a lipid environment consisting exclusively of l(o) and s(o) microdomains, UQ molecules tend to segregate into UQ-rich pools. In all lipid environments, electron transport by UQ occurs with the quinone moiety localized on the solution side with respect to the ester linkages of the dioleoylphosphatidylcholine molecules.

Polymer Amphiphiles for Photoregulated Anticancer Drug Delivery.

We report the synthesis of amphiphilic polymers featuring lipophilic stearyl chains and hydrophilic poly(ethylene glycol) polymers that are connected through singlet oxygen-cleavable alkoxyanthracene linkers. These amphiphilic polymers assembled in water to form micelles with diameters of ∼20 nm. Reaction of the alkoxyanthracene linkers with light and O2 cleaved the ether C-O bonds, resulting in formation of the corresponding 9,10-anthraquinone derivatives and concomitant disruption of the micelles. These micelles were loaded with the chemotherapeutic agent doxorubicin, which was efficiently released upon photo-oxidation. The drug-loaded reactive micelles were effective at killing cancer cells in vitro upon irradiation at 365 nm, functioning through both doxorubicin release and photodynamic mechanisms.

Indocyanine Green J Aggregates in Polymersomes for Near-Infrared Photoacoustic Imaging.

Clinical translation of photoacoustic imaging (PAI) has been limited by the lack of near-infrared (NIR) contrast agents with low toxicity required for regulatory approval. Herein, J aggregates of indocyanine green (ICG) with strong NIR absorbance were encapsulated at high loadings within small 77 nm polymersomes (nanocapsules) composed of poly(lactide-co-glycolide-b-poly(ethylene glycol)) (PLGA-b-PEG) bilayers, thus enabling PAI of of breast and ovarian cancer cells with high specificity and a sensitivity at the level of ∼100 total cells. All of the major components of the polymersomes are FDA approved and used in the clinic. During formation of polymersomes with a water-in-oil-in-water double emulsion process, loss of ICG from the ICG J aggregates was minimized by coating them with a layer of branched polyethylenimine and by providing excess "sacrificial" ICG to adsorb at the oil-water interfaces. The encapsulated J aggregates were protected against dissociation by the polymersome shell for 24 h in 100% fetal bovine serum, after which the polymersomes biodegraded and the J aggregates dissociated to ICG monomers.

Intracellular delivery of proteins by nanocarriers.

Intracellular delivery of proteins is potentially a game-changing approach for therapeutics. However, for most applications, the protein needs to access the cytosol to be effective. A wide variety of strategies have been developed for protein delivery, however access of delivered protein to the cytosol without acute cytotoxicity remains a critical issue. In this review we discuss recent trends in protein delivery using nanocarriers, focusing on the ability of these strategies to deliver protein into the cytosol.

The fate of differently functionalized gold nanorods in human serum: A response from capillary electrophoresis-inductively coupled plasma mass spectrometry.

A highly selective and sensitive method was developed to characterize intrinsic intramolecular interactions between potential theranostic agents, gold nanorods (AuNRs), and plasma proteins. The method is based on a hyphenation of capillary electrophoresis (CE) with inductively coupled plasma mass spectrometry (ICP-MS), which enables monitoring the speciation changes of AuNRs under physiologically compatible conditions. To improve the separation resolution between the intact nanorods and different gold-protein conjugates, the CE system was optimized by varying the type and concentration of background electrolyte, applied voltage, and sample loading. Optimization allowed also for acquiring the acceptable figures of merit such as migration time and peak area precision of 4.7-8.2% and 5.1-6.3%, respectively, detection limits in the range of 5.5-5.7µgL-1 Au, and recoveries on the order of 91-99%. With the developed method the metal-specific profiles were recorded for differently functionalized AuNPs in combinations with individual serum proteins and in human serum. In case of carboxy-modified AuNPs, proteinization in real-serum environment occurs without albumin participation, apo-transferrin dominating the protein corona under equilibrium conditions. On the contrary, the AuNRs with surface amino-groups first form the albumin conjugate but albumin in this "soft" corona becomes slowly replaced by other, less abundant proteins, exhibiting a higher affinity toward the aminated surface.

{Ru(CO)x}-Core complexes with benzimidazole ligands: synthesis, X-ray structure and evaluation of anticancer activity in vivo.

The reaction of [Ru(CO)6Cl2], 1, with N[combining low line]3-methylbenzimidazole (MBI) and 5,6-dimethylbenzimidazole (DMBI) afforded two new complexes with the general formula fac-[RuII(CO)3Cl2L], L = MBI (2) or DMBI (4). Crystals of cis,trans-[RuII(CO)2Cl2(N[combining low line]3-MBI)2], 3, were also obtained from the mother liquor that produced 2. In the presence of water, the dissociation of Ru-N, Ru-Cl and Ru-CO bonds occurred as a function of time, water content and pH. Density functional theory structure simulations/optimizations were carried out at the Becke3LYP level of theory for evaluating the relative stability of possible conformers. ESI-MS studies revealed the ability of the complexes to link model proteins, such as lysozyme, bovine pancreatic ribonuclease and cytochrome c, with the partial release of the heteroaromatic base, chlorido and carbonyl ligands. X-ray diffraction studies on crystals grown from a solution of HEWL and 2 showed the partial removal of chloride and CO. Cytotoxicity tests yielded two-digit micromolar IC50 values in CH1/PA-1 and SW480 cancer cells. In contrast to CORM-3 and 2, a significantly reduced tumor growth was observed with 4 in the murine colon cancer CT-26 model in vivo.

Speciation of metal-based nanomaterials in human serum characterized by capillary electrophoresis coupled to ICP-MS: a case study of gold nanoparticles.

The development and optimization of a versatile analytical system for the speciation analysis of metal-containing nanoscale materials in blood serum is reported herein. Based on capillary electrophoresis (CE) interfaced with inductively coupled plasma mass spectrometry (ICP-MS), the method was shown to be feasible to investigate the interactions between serum proteins and gold nanoparticles of potential medicinal use, which are their first and foremost occurrence upon their entry into the circulatory system. To improve the separation resolution between the intact nanoparticles and different protein conjugates, the CE system was optimized with an emphasis on compatibility with physiological conditions, avoiding aggregation effects, and analyte recovery. Optimization allowed also for acquiring the acceptable figures of merit such as migration time and peak area precision of 1.0-6.4% and 2.4-6.9%, respectively, detection limits in the range of 0.8-1.0 µg L(-1) Au, and capillary recoveries on the order of 86-97%, depending on the nanoparticle size and conjugate type. We sytematically investigated the role of size in mediating protein adsorption to gold nanoparticles in a real-serum environment. At the initial stage of surface coating, the speciation of smaller particles (5 and 10 nm) was found to be dominated by albumin, transferrin (both in apo- and holo-form) playing the secondary role in developing the protein corona. For 20 and 50 nm nanoparticles, the contribution of transferrin is initially comparable; however, with time it becomes replaced by albumin. The time of attaining equilibrium adsorption is also a function of particle size but for the whole size range investigated, albumin is the only equilibrium binding partner. These principal findings prove that for metal-based nanomaterials in general, serum protein conjugates could be variable in composition depending on the protein abundance and binding affinity, as well as the residence time in the bloodstream.

Tuning the interactions of PEG-coated gold nanorods with BSA and model proteins through insertion of amino or carboxylate groups.

Gold nanorods (GNRs) are important platforms for biosensing and drug delivery. As for most nanomaterials, appropriate coatings such as polyethylene glycol (PEG) are needed to stabilize GNRs within biological fluids. We show here that the interactions of GNRs with proteins can be finely modulated through surface modification using PEG-containing chains bearing charged headgroups. Interestingly, introduction of amino or carboxylate groups produces relevant and differential changes in GNR interactions with three representative proteins: lysozyme, cytochrome c, and bovine serum albumin. These effects were explored through the direct monitoring of plasmonic bands of the GNRs and are supported by independent dynamic light scattering (DLS) and circular dichroism (CD) determinations. Notably, GNR-protein interactions observed for these charged GNRs can be almost completely reversed by salt addition. These observations demonstrate the importance of electrostatic effects in governing GNR-protein interactions, and provide a basis for new sensing and delivery platforms.

Reactions of model proteins with aurothiomalate, a clinically established gold(I) drug: The comparison with auranofin.

Aurothiomalate (AuTm) is an old, clinically established, antiarthritic gold drug that is currently being reconsidered as a candidate drug for cancer treatment and for other therapeutic indications within a more general drug repositioning program. As the biological effects of gold drugs seem to be mediated, mainly, by their interactions with protein targets we have analyzed here, in detail, the metalation patterns produced by aurothiomalate in a few model proteins. In particular, the reactions of aurothiomalate with the small proteins ribonuclease A, cytochrome c and lysozyme were explored through ESI MS (electrospray ionization mass spectrometry) analysis. Notably, characteristic and rather constant features emerged in the protein metalation patterns induced by AuTm that are markedly distinct from those caused by auranofin; a non-covalent interaction mode is invoked for AuTm binding to the mentioned proteins. The affinity constants of AuTm toward the three mentioned proteins were also initially assessed. The implications of the present findings are discussed.

Rapid purification of gold nanorods for biomedical applications.

Small gold nanorods (GNRs) with longitudinal plasmon absorption in the near-infrared window (700-900 nm), are of great interest for in vivo optical applications (e.g., photothermal therapy) and for their high-payload-to-carrier ratio for drug delivery. Common synthetic strategies for GNR production afford spherical and cubical nanoparticles in addition to the desired GNRS. Thus, several methods have been proposed for the selective separation of GNRs from the reaction byproducts. For example, centrifugation has been used to separate the high aspect ratio (AR) GNRs (AR>4). However, it is difficult to separate small sized GNRs with low AR (AR≤4) that are particularly promising for biomedical applications. Here, we describe a simple and fast procedure for the separation of small GNRs with AR of 4, and length of 28 nm from reaction by-products. The shape separation is achieved through centrifugation according to the following steps: - Isolation of all gold products of the reaction from the excess of cetyl trimethylammonium bromide through a first cycle of centrifugation. - Optimization of the speed and the time of centrifugation for the separation of GNRs from the reaction by-products. The effectiveness of this procedure is documented.

Interactions of gold-based drugs with proteins: crystal structure of the adduct formed between ribonuclease A and a cytotoxic gold(III) compound.

The reaction of Auoxo6, a dinuclear gold(III) complex, with the model protein bovine pancreatic ribonuclease is explored here by X-ray diffraction and ESI mass spectrometry. Data provide clues on the processes of adduct formation and of enzyme inhibition and, inductively, on the likely mode of action of this metallodrug.

Synthesis, spectroscopic and DFT structural characterization of two novel ruthenium(III) oxicam complexes. In vivo evaluation of anti-inflammatory and gastric damaging activities.

The reactions of ruthenium(III) chloride trihydrate with piroxicam (H2PIR) and tenoxicam (H2TEN), two widely used non-steroidal anti-inflammatory drugs, afforded [Ru(III)Cl2(H2PIR)(HPIR)],·1, and [Ru(III)Cl2(H2TEN)(HTEN)],·2. Both compounds were obtained as pure green solids through purification via flash column chromatography. Characterizations were accomplished through UV-vis and IR spectroscopy, potentiometry and HPLC. Quantum mechanics and density functional computational methods were applied to investigate their respective molecular structures. The experimental and computational results are in agreement with a pseudo-octahedral coordination where the two chlorido ligands are in trans positions (apical) and the two trans-N,O chelating oxicam ligands occupy the equatorial sites. Both compounds revealed an acceptable solubility and stability profile upon dissolution in a standard buffer at physiological pH. Nonetheless, the addition of biologically occurring reducing agents caused spectral changes. The two complexes manifested a poor reactivity with the model proteins cytochrome c and lysozyme: no evidence for adduct formation was indeed obtained based on a standard ESI MS analysis; in contrast, some significant reactivity with serum albumin was proved spectrophotometrically. Remarkably, both study compounds revealed pronounced anti-edema effects in vivo suggesting that the pharmacological actions of the ligands are mostly retained; in addition, they were less irritating than piroxicam on the gastric mucosa when the coordination compounds and free oxicam were administered at the same overall molar concentration of the ligand. Overall, the present results point out that ruthenium coordination may represent an effective strategy to improve the pharmacological properties of oxicam drugs reducing their undesired side effects.