Colloidal InAs Tetrapods: Impact of Surfactants on the Shape Control.

We have approached the synthesis of colloidal InAs nanocrystals (NCs) using amino-As and ligands that are different from the commonly employed oleylamine (OA). We found that carboxylic and phosphonic acids led only to oxides, whereas tri-n-octylphosphine, dioctylamine, or trioctylamine (TOA), when employed as the sole ligands, yielded InAs NCs with irregular sizes and a broad size distribution. Instead, various combinations of TOA and OA delivered InAs NCs with good control over the size distribution, and the TOA:OA volume ratio of 4:1 generated InAs tetrapods with arm length of 5-6 nm. Contrary to tetrapods of II-VI materials, which have a zinc-blende core and wurtzite arms, these NCs are entirely zinc-blende, with arms growing along the ⟨111⟩ directions. They feature a narrow excitonic peak at ∼950 nm in absorption and a weak photoluminescence emission at 1050 nm. Our calculations indicated that the bandgap of the InAs tetrapods is mainly governed by the size of their core and not by their arm lengths when these are longer than ∼3 nm. Nuclear magnetic resonance analyses revealed that InAs tetrapods are mostly passivated by OA with only a minor fraction of TOA. Molecular dynamics simulations showed that OA strongly binds to the (111) facets whereas TOA weakly binds to the edges and corners of the NCs and their combined use (at high TOA:OA volume ratios) promotes growth along the ⟨111⟩ directions, eventually forming tetrapods. Our work highlights the use of mixtures of ligands as a means of improving control over InAs NCs size and size distribution.

Harnessing the reverse cholesterol transport pathway to favor differentiation of monocyte-derived APCs and antitumor responses.

Lipid and cholesterol metabolism play a crucial role in tumor cell behavior and in shaping the tumor microenvironment. In particular, enzymatic and non-enzymatic cholesterol metabolism, and derived metabolites control dendritic cell (DC) functions, ultimately impacting tumor antigen presentation within and outside the tumor mass, dampening tumor immunity and immunotherapeutic attempts. The mechanisms accounting for such events remain largely to be defined. Here we perturbed (oxy)sterol metabolism genetically and pharmacologically and analyzed the tumor lipidome landscape in relation to the tumor-infiltrating immune cells. We report that perturbing the lipidome of tumor microenvironment by the expression of sulfotransferase 2B1b crucial in cholesterol and oxysterol sulfate synthesis, favored intratumoral representation of monocyte-derived antigen-presenting cells, including monocyte-DCs. We also found that treating mice with a newly developed antagonist of the oxysterol receptors Liver X Receptors (LXRs), promoted intratumoral monocyte-DC differentiation, delayed tumor growth and synergized with anti-PD-1 immunotherapy and adoptive T cell therapy. Of note, looking at LXR/cholesterol gene signature in melanoma patients treated with anti-PD-1-based immunotherapy predicted diverse clinical outcomes. Indeed, patients whose tumors were poorly infiltrated by monocytes/macrophages expressing LXR target genes showed improved survival over the course of therapy. Thus, our data support a role for (oxy)sterol metabolism in shaping monocyte-to-DC differentiation, and in tumor antigen presentation critical for responsiveness to immunotherapy. The identification of a new LXR antagonist opens new treatment avenues for cancer patients.

Synthesis and Characterization of Curcumin-Loaded Nanoparticles of Poly(Glycerol Sebacate): A Novel Highly Stable Anticancer System.

The research for alternative administration methods for anticancer drugs, towards enhanced effectiveness and selectivity, represents a major challenge for the scientific community. In the last decade, polymeric nanostructured delivery systems represented a promising alternative to conventional drug administration since they ensure secure transport to the selected target, providing active compounds protection against elimination, while minimizing drug toxicity to non-target cells. In the present research, poly(glycerol sebacate), a biocompatible polymer, was synthesized and then nanostructured to allow curcumin encapsulation, a naturally occurring polyphenolic phytochemical isolated from the powdered rhizome of Curcuma longa L. Curcumin was selected as an anticancer agent in virtue of its strong chemotherapeutic activity against different cancer types combined with good cytocompatibility within healthy cells. Despite its strong and fascinating biological activity, its possible exploitation as a novel chemotherapeutic has been hampered by its low water solubility, which results in poor absorption and low bioavailability upon oral administration. Hence, its encapsulation within nanoparticles may overcome such issues. Nanoparticles obtained through nanoprecipitation, an easy and scalable technique, were characterized in terms of size and stability over time using dynamic light scattering and transmission electron microscopy, confirming their nanosized dimensions and spherical shape. Finally, biological investigation demonstrated an enhanced cytotoxic effect of curcumin-loaded PGS-NPs on human cervical cancer cells compared to free curcumin.

Fatty Acids/Tetraphenylethylene Conjugates: Hybrid AIEgens for the Preparation of Peptide-Based Supramolecular Gels.

Aggregation-induced emissive materials are gaining particular attention in the last decades due to their wide application in different fields, from optical devices to biomedicine. In this work, compounds having these kinds of properties, composed of tetraphenylethylene scaffold combined with fatty acids of different lengths, were synthesized and characterized. These molecules were found able to self-assemble into different supramolecular emissive structures depending on the chemical composition and water content. Furthermore, they were used as N-terminus capping agents in the development of peptide-based materials. The functionalization of a 5-mer laminin-derived peptide led to the obtainment of luminescent fibrillary materials that were not cytotoxic and were able to form supramolecular gels in aqueous environment.

Ecological Impact of End-of-Life-Tire (ELT)-Derived Rubbers: Acute and Chronic Effects at Organism and Population Levels.

Considering the large amount of tires that reach the end of life every year, the aim of this study was the evaluation of both acute and chronic effects of end-of-life-tire (ELT)-derived rubber granules (ELT-dg) and powder (ELT-dp) on a freshwater trophic chain represented by the green alga Pseudokirchneriella subcapitata, the crustacean Daphnia magna and the teleost Danio rerio (zebrafish). Adverse effects were evaluated at the organism and population levels through the classical ecotoxicological tests. Acute tests on D. magna and D. rerio revealed a 50% effect concentration (EC50) > 100.0 mg/L for both ELT-dg and ELT-dp. Chronic exposures had a lowest observed effect concentration (LOEC) of 100.0 mg/L for both ELT-dg and ELT-dp on P. subcapitata grow rate and yield. LOEC decreased in the other model organisms, with a value of 9.8 mg/L for D. magna, referring to the number of living offspring, exposed to ELT-dg suspension. Similarly, in D. rerio, the main results highlighted a LOEC of 10.0 mg/L regarding the survival and juvenile weight parameters for ELT-dg and a LOEC of 10.0 mg/L concerning the survival and abnormal behavior in specimens exposed to ELT-dp. Tested materials exhibited a threshold of toxicity of 9.8 mg/L, probably a non-environmental concentration, although further investigations are needed to clarify the potential ecological impact of these emerging contaminants.

Chiral Fibers Formation Upon Assembly of Tetraphenylalanine Peptide Conjugated to a PNA Dimer.

Self-assembly of biomolecules such as peptides, nucleic acids or their analogues affords supramolecular objects, exhibiting structures and physical properties dependent on the amino-acid or nucleobase composition. Conjugation of the peptide diphenylalanine (FF) to peptide nucleic acids triggers formation of self-assembled structures, mainly stabilized by interactions between FF. In this work we report formation of homogeneous chiral fibers upon self-assembly of the hybrid composed of the tetraphenylalanine peptide (4F) conjugated to the PNA dimer adenine-thymine (at). In this case nucleobases seem to play a key role in determining the morphology and chirality of the fibers. When the PNA "at" is replaced by guanine-cytosine dimer "gc", disordered structures are observed. Spectroscopic characterization of the self-assembled hybrids, along with AFM and SEM studies is reported. Finally, a structural model consistent with the experimental evidence has also been obtained, showing how the building blocks of 4Fat arrange to give helical fibers.

In search for novel liver X receptors modulators by extending the structure-activity relationships of cholenamide derivatives.

N,N-Dimethyl 3ß-hydroxychol-5-en-24-amide (DMHCA, 3) is the prototype of cholenamides, a class of steroidal LXR modulators characterized by the nucleus of Δ5-cholen-3ß-ol and the presence of an amide moiety at C-24. DMHCA (3) has been reported to act as a gene-selective modulator able to fully induce ABCA1 expression whilst poorly up-regulate the expression of FASN and SREBP-1α genes. With the aim to widen the limited structure-activity relationships of DMHCA (3), herein we describe the synthesis and the biological evaluation of nine novel derivatives, resulting from a) the homologation of DMHCA's side-chain to give N,N-dimethyl 3ß-hydroxy-24a-homochol-5-en-24a-amide (4); b) the distal branching of the side-chain of 3 and 4 by introducing an ethyl group at C-23 and C-24, respectively; c) the replacement of the dimethyl amide moiety of all the derivatives with a carboxylic acid function. While broadening the structure-activity relationships of the class of cholenamides, we were successful in the discovery of (24R)-N,N-dimethyl-24-ethyl-3ß-hydroxy-24a-homochol-5-en-24a-amide (6) as a novel LXR agonist with improved profile in term of selective gene modulation respect to the prototype DMHCA (3); indeed, 6 was able to up-regulate the expression of ABCA1 more than DMHCA (3), without to induce SREBP-1c, differently from DMHCA (3). Moreover, 6 induced the expression of FASN less than 3 and interestingly was a negative modulator towards SCD1 in contrast to DMHCA (3), which instead weakly induced the expression of this gene.

Exploiting Ultrashort α,ß-Peptides in the Colloidal Stabilization of Gold Nanoparticles.

Colloidal gold nanoparticles (GNPs) have found wide-ranging applications in nanomedicine due to their unique optical properties, ease of preparation, and functionalization. To avoid the formation of GNP aggregates in the physiological environment, molecules such as lipids, polysaccharides, or polymers are employed as GNP coatings. Here, we present the colloidal stabilization of GNPs using ultrashort α,ß-peptides containing the repeating unit of a diaryl ß2,3-amino acid and characterized by an extended conformation. Differently functionalized GNPs have been characterized by ultraviolet, dynamic light scattering, and transmission electron microscopy analysis, allowing us to define the best candidate that inhibits the aggregation of GNPs not only in water but also in mouse serum. In particular, a short tripeptide was found to be able to stabilize GNPs in physiological media over 3 months. This new system has been further capped with albumin, obtaining a material with even more colloidal stability and ability to prevent the formation of a thick protein corona in physiological media.

Alginate coating modifies the biological effects of cerium oxide nanoparticles to the freshwater bivalve Dreissena polymorpha.

The adsorption of biomacromolecules is a fundamental process that can alter the behaviour and adverse effects of nanoparticles (NPs) in natural systems. While the interaction of NPs with natural molecules present in the environment has been described, their biological impacts are largely unknown. Therefore, this study aims to provide a first evidence of the influence of biomolecules sorption on the toxicity of cerium oxide nanoparticles (CeO2NPs) towards the freshwater bivalve Dreissena polymorpha. To this aim, we compared naked CeO2NPs and coated with alginate and chitosan, two polysaccharides abundant in aquatic environments. Mussels were exposed to the three CeO2NPs (naked, chitosan- and alginate-coated) up to 14 days at 100 µg L-1, which is a concentration higher than the environmental one predicted for this type of NP. A suite of biomarkers related to oxidative stress and energy metabolism was applied, and metabolomics was also carried out to identify metabolic pathways potentially targeted by CeO2NPs. Results showed that the coating with chitosan reduced NP aggregation and increased the stability in water. Nonetheless, the Ce accumulation in mussels was similar in all treatments. As for biological effects, all three types of CeO2NPs reduced significantly the level of reactive oxygen species and the activity of superoxide dismutase, glutathione peroxidase and glutathione-S-transferase. The effect was more pronounced in individuals exposed to CeO2NPs coated with alginate, which also significantly induced the activity of the electron transport system. Metabolomics analysis of amino acid metabolism showed modulation only in mussels treated with CeO2NPs coated with alginate. In this group, 25 metabolites belonging to nucleotides, lipids/sterols and organic osmolytes were also modulated, suggesting that the nanoparticles affect energetic metabolism and osmoregulation of mussels. This study highlights the key role of the interaction between nanoparticles and natural molecules as a driver of nanoparticle ecotoxicity.

Coating with polysaccharides influences the surface charge of cerium oxide nanoparticles and their effects to Mytilus galloprovincialis.

This study focused on the effects of surface coating, acquired through the interaction with natural biomolecules, on the behavior and ecotoxicity of nanoparticles (NPs). To this aim, the effects of Cerium Oxide Nanoparticles (CeO2NPs) naked and coated with chitosan and alginate on the marine mussel Mytilus galloprovincialis were compared. Mussels were exposed for 7 days to 100 µg L-1 of CeO2NPs and for 28 days to 1 µg L-1 of CeO2NPs. In both experiments CeO2NPs were used naked and coated with the two polysaccharides. The lowest tested concentration allowed to understand the environmental relevance of this biological process. A set of biomarkers related to oxidative stress/damage and energy metabolism was applied to assess the ecotoxicity of CeO2NPs. The aggregation and stability in water of CeO2NPs were measured through dynamic light scattering analysis and the levels of Ce in the exposure media and in mussels soft tissues were determined by inductively coupled plasma-mass spectrometry. Results showed a different hydrodynamic behavior and stability of CeO2NPs in saltwater related to the different coatings. Despite this, no differences in the bioaccumulation of CeO2NPs were observed among the experimental groups. Different coatings affected also CeO2NPs toxicological outcomes in both 7- and 28-days exposures. Coating with chitosan enhanced antioxidant enzyme activities while coating with alginate triggered oxidative damage. Although the oxidant pathways did not differ that much among the exposures, biomarkers of energetic supplies suggested a different strategy of defense in response to CeO2NP exposure at a lower concentration and for a longer period of time. The obtained results are in line with findings of a previous study on freshwater mussels, suggesting that the coating with biomolecules, which impart negative charge to the NPs, might enhance their biological effects. This study highlighted that interactions of NPs with natural biomolecules largely present in the aquatic environment could affect NPs toxicity altering the interaction towards organisms.

Nanosized T1 MRI Contrast Agent Based on a Polyamidoamine as Multidentate Gd Ligand.

A linear polyamidoamine (PAA) named BAC-EDDS, containing metal chelating repeat units composed of two tert-amines and four carboxylic groups, has been prepared by the aza-Michael polyaddition of ethylendiaminodisuccinic (EDDS) with 2,2-bis(acrylamido)acetic acid (BAC). It was characterized by size exclusion chromatography (SEC), FTIR, UV-Vis and NMR spectroscopies. The pKa values of the ionizable groups of the repeat unit were estimated by potentiometric titration, using a purposely synthesized molecular ligand (Agly-EDDS) mimicking the structure of the BAC-EDDS repeat unit. Dynamic light scattering (DLS) and ζ-potential analyses revealed the propensity of BAC-EDDS to form stable nanoaggregates with a diameter of approximately 150 nm at pH 5 and a net negative charge at physiological pH, in line with an isoelectric point <2. BAC-EDDS stably chelated Gd (III) ions with a molar ratio of 0.5:1 Gd (III)/repeat unit. The stability constant of the molecular model Gd-Agly-EDDS (log K = 17.43) was determined as well, by simulating the potentiometric titration through the use of Hyperquad software. In order to comprehend the efficiency of Gd-BAC-EDDS in contrasting magnetic resonance images, the nuclear longitudinal (r1) and transverse (r2) relaxivities as a function of the externally applied static magnetic field were investigated and compared to the ones of commercial contrast agents. Furthermore, a model derived from the Solomon-Bloembergen-Morgan theory for the field dependence of the NMR relaxivity curves was applied and allowed us to evaluate the rotational correlation time of the complex (τ = 0.66 ns). This relatively high value is due to the dimensions of Gd-BAC-EDDS, and the associated rotational motion causes a peak in the longitudinal relaxivity at ca. 75 MHz, which is close to the frequencies used in clinics. The good performances of Gd-BAC-EDDS as a contrast agent were also confirmed through in vitro magnetic resonance imaging experiments with a 0.2 T magnetic field.

Nucleobase morpholino ß amino acids as molecular chimeras for the preparation of photoluminescent materials from ribonucleosides.

Bioinspired smart materials represent a tremendously growing research field and the obtainment of new building blocks is at the molecular basis of this technology progress. In this work, colloidal materials have been prepared in few steps starting from ribonucleosides. Nucleobase morpholino ß-amino acids are the chimera key intermediates allowing Phe-Phe dipeptides' functionalization with adenine and thymine. The obtained compounds self-aggregate showing enhanced photoluminescent features, such as deep blue fluorescence and phosphorescence emissions.

An Approach for Magnetic Halloysite Nanocomposite with Selective Loading of Superparamagnetic Magnetite Nanoparticles in the Lumen.

We present for the first time a method for the preparation of magnetic halloysite nanotubes (HNT) by loading of preformed superparamagnetic magnetite nanoparticles (SPION) of diameter size ∼6 nm with a hydrodynamic diameter of ∼10 nm into HNT. We found that the most effective route to reach this goal relies on the modification of the inner lumen of HNT by tetradecylphosphonic acid (TDP) to give HNT-TDP, followed by the loading with preformed oleic acid (OA)-stabilized SPION. Transmission electron microscopy evidenced the presence of highly crystalline magnetic nanoparticles only in the lumen, partially ordered in chainlike structures. Conversely, attempts to obtain the same result by exploiting either the positive charge of the HNT inner lumen employing SPIONs covered with negatively charged capping agents or the in situ synthesis of SPION by thermal decomposition were not effective. HNT-TDP were characterized by infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TGA), and ζ-potential, and all of the techniques confirmed the presence of TDP onto the HNT. Moreover, the inner localization of TDP was ascertained by the use of Nile Red, a molecule whose luminescence is very sensitive to the polarity of the environment. The free SPION@OA (as a colloidal suspension and as a powder) and SPION-in-HNT powder were magnetically characterized by measuring the ZFC-FC magnetization curves as well as the hysteresis cycles at 300 and 2.5 K, confirming that the super-paramagnetic behavior and the main magnetic properties of the free SPION were preserved once embedded in SPION-in-HNT.

Light-Triggered Trafficking to the Cell Nucleus of a Cationic Polyamidoamine Functionalized with Ruthenium Complexes.

Strategies for endosomal escape and access to the cell nucleus are highly sought for nanocarriers to deliver their load efficiently following endocytosis. In this work, we have studied the uptake and intracellular trafficking of a polycationic polyamidoamine (PAA) endowed with a luminescent Ru complex, Ru-PhenAN, that shows unique trafficking to the cell nucleus. Live cell imaging confirmed the capacity of this polymer to access the nucleus, excluding artifacts due to cell fixation, and clarified that the mechanism of escape is light-triggered and relies on the presence of the Ru complexes and their capacity to absorb light and act as photosensitizers for singlet oxygen production. These results open up the possibility to use PAA-ruthenium complexes for targeted light-triggered delivery of genetic material or drugs to the cytosol and nucleus.

Will temperature rise change the biochemical alterations induced in Mytilus galloprovincialis by cerium oxide nanoparticles and mercury?

It is known that, for marine coastal ecosystems, pollution and global warming are among the most threatening factors. Among emerging pollutants, nanoparticles (NPs) deserve particular attention as their possible adverse effects are significantly influenced by environmental factors such as salinity, pH and temperature, as well as by their ability to interact with other contaminants. In this framework, the present study aimed to evaluate the potential interactions between CeO2 NPs and the toxic classic metal mercury (Hg), under current and warming conditions. The marine bivalve Mytilus galloprovincialis was used as biological model and exposed to CeO2 NPs and Hg, either alone or in combination, for 28 day at 17 °C and 22 °C. A suite of biomarkers related to energetic metabolism, oxidative stress/damage, redox balance, and neurotoxicity was applied in exposed and non-exposed (control) mussels. The Hg and Ce accumulation was also assessed. Results showed that the exposure to CeO2 NPs alone did not induce toxic effects in M. galloprovincialis. On the contrary, Hg exposure determined a significant loss of energetic metabolism and a general impairment in biochemical performances. Hg accumulation in mussels was not modified by the presence of CeO2 NPs, while the biochemical alterations induced by Hg alone were partially canceled upon co-exposure with CeO2 NPs. The temperature increase induced loss of metabolic and biochemical functions and the effects of temperature prevailed on mussels exposed to pollutants acting alone or combined.

Plastics and biodegradable plastics: ecotoxicity comparison between polyvinylchloride and Mater-Bi® micro-debris in a freshwater biological model.

The improper release of plastic items and wastes is nowadays one of the main environmental and social problems, whose solution or mitigation represents a great challenge worldwide. In this context, the growing use of the so-called biodegradable plastics could represent a possible solution in the short to medium term. The few information known about the ecological impact of these materials on freshwater organisms, especially the ones relative to the micro-debris derived from their aging, prompted us to study the comparison of the sub-lethal effects eventually caused by plastic and biodegradable plastic micro-debris on the mussel Dreissena polymorpha, which represents an excellent biological model for the freshwater ecosystems. We selected two powders of polyvinylchloride (PVC) and Mater-Bi® administered at 1 mg/L to D. polymorpha specimens in semi-static conditions for 14 days. The presence of micro-debris was evaluated on mussel tissues and pseudo-faeces using advanced microscopy techniques. The sub-lethal effects were investigated on exposed mussels at 6 and 14 days using a suite of biomarkers of cellular stress, oxidative damage, and genotoxicity. Lastly, we compared the ecotoxicity of these two materials integrating each endpoint in the Biomarker Response Index. Microscopy observations highlighted the surprising absence of micro-debris in the gut lumen and tissues of exposed mussels, but the presence of both PVC and Mater-Bi® micro-debris in the pseudo-faeces, suggesting a possible efficient elimination mechanism adopted by mussels to avoid the micro-debris gulping. Consequently, we did not observe significant sub-lethal effects, except for the glutathione-S-transferase activity modulation after 6 days of exposure.

PA6 and Halloysite Nanotubes Composites with Improved Hydrothermal Ageing Resistance: Role of Filler Physicochemical Properties, Functionalization and Dispersion Technique.

Polyamide 6 (PA6) suffers from fast degradation in humid conditions due to hydrolysis of amide bonds, which limits its durability. The addition of nanotubular fillers represents a viable strategy for overcoming this issue, although the additive/polymer interface at high filler content can become privileged site for moisture accumulation. As a cost-effective and versatile material, halloysite nanotubes (HNT) were investigated to prepare PA6 nanocomposites with very low loadings (1-45% w/w). The roles of the physicochemical properties of two differently sourced HNT, of filler functionalization with (3-aminopropyl)triethoxysilane and of dispersion techniques (in situ polymerization vs. melt blending) were investigated. The aspect ratio (5 vs. 15) and surface charge (-31 vs. -59 mV) of the two HNT proved crucial in determining their distribution within the polymer matrix. In situ polymerization of functionalized HNT leads to enclosed and well-penetrated filler within the polymer matrix. PA6 nanocomposites crystal growth and nucleation type were studied according to Avrami theory, as well as the formation of different crystalline structures (α and γ forms). After 1680 h of ageing, functionalized HNT reduced the diffusion of water into polymer, lowering water uptake after 600 h up to 90%, increasing the materials durability also regarding molecular weights and rheological behavior.

Self-assembled hydrophobic Ala-Aib peptide encapsulating curcumin: a convenient system for water insoluble drugs.

The exploitation of self-assembled systems to improve the solubility of drugs is getting more and more attention. Among the different types of self-assembled biomaterials, peptides and in particular peptides containing non-coded amino acids (NCAPs) are promising because their use opens the door to more stable materials inducing increased stability to proteolysis. New classes of NCAP, Ac-Ala-X-Ala-Aib-AlaCONH2 (X = alpha-aminoisobutyric acid (Aib) or X = cyclopentane amino acid (Ac5c)) have been prepared and the correlation between the different secondary peptide structure and solvent (i.e. CD3CN, CD3OH, H2O/D2O) verified by NMR. Furthermore, the formation of a nanocolloidal system in water was deeply studied by DLS and the morphology of the obtained spherical aggregates with nanometric dimensions was assessed by TEM. Aib containing pentapeptide was selected for greater ease of synthesis. Its ability to encapsulate curcumin, as a model insoluble drug molecule, was investigated using fluorescence emission and confocal microscopy analyses. Two different approaches were used to study the interaction between curcumin and peptide aggregates. In the first approach peptide aggregates were formed in the presence of curcumin, while in the second approach curcumin was added to the already formed peptide aggregates. We succeeded in our challenge by using the second approach and 53.8% of added curcumin had been encapsulated.

Natural molecule coatings modify the fate of cerium dioxide nanoparticles in water and their ecotoxicity to Daphnia magna.

The ongoing development of nanotechnology has raised concerns regarding the potential risk of nanoparticles (NPs) to the environment, particularly aquatic ecosystems. A relevant aspect that drives NP toxicity is represented by the abiotic and biotic processes occurring in natural matrices that modify NP properties, ultimately affecting their interactions with biological targets. Therefore, the objective of this study was to perform an ecotoxicological evaluation of CeO2NPs with different surface modifications representative of NP bio-interactions with molecules naturally occurring in the water environment, to identify the role of biomolecule coatings on nanoceria toxicity to aquatic organisms. Ad hoc synthesis of CeO2NPs with different coating agents, such as Alginate and Chitosan, was performed. The ecotoxicity of the coated CeO2NPs was assessed on the marine bacteria Aliivibrio fischeri, through the Microtox® assay, and with the freshwater crustacean Daphnia magna. Daphnids at the age of 8 days were exposed for 48 h, and several toxicity endpoints were evaluated, from the molecular level to the entire organism. Specifically, we applied a suite of biomarkers of oxidative stress and neurotoxicity and assessed the effects on behaviour through the evaluation of swimming performance. The different coatings affected the hydrodynamic behaviour and colloidal stability of the CeO2NPs in exposure media. In tap water, NPs coated with Chitosan derivative were more stable, while the coating with Alginate enhanced the aggregation and sedimentation rate. The coatings also significantly influenced the toxic effects of CeO2NPs. Specifically, in D. magna the CeO2NPs coated with Alginate triggered oxidative stress, while behavioural assays showed that CeO2NPs coated with Chitosan induced hyperactivity. Our findings emphasize the role of environmental modification in determining the NP effects on aquatic organisms.

Tuning Polyamidoamine Design To Increase Uptake and Efficacy of Ruthenium Complexes for Photodynamic Therapy.

In this work, we report the synthesis of [Ru(phen)32+]-based complexes and their use as photosensitizers for photodynamic therapy (PDT), a treatment of pathological conditions based on the photoactivation of bioactive compounds, which are not harmful in the absence of light irradiation. Of these complexes, Ru-PhenISA and Ru-PhenAN are polymer conjugates containing less than 5%, (on a molar basis), photoactive units. Their performance is compared with that of a small [Ru(phen)32+] compound, [Ru(phen)2BAP](OTf)2 (BAP = 4-(4'-aminobutyl)-1,10-phenanthroline, OTf = triflate anion), used as a model of the photoactive units. The polymer ligands, PhenISA and PhenAN, are polyamidoamines with different acid-base properties. At physiological pH, the former is zwitterionic, the latter moderately cationic, and both intrinsically cytocompatible. The photophysical characterizations show that the complexation to macromolecules does not hamper the Ru(phen)32+ ability to generate toxic singlet oxygen upon irradiation, and phosphorescence lifetimes and quantum yields are similar in all cases. All three compounds are internalized by HeLa cells and can induce cell death upon visible light irradiation. However, their relative PDT efficiency is different: the zwitterionic PhenISA endowed with the Ru-complex lowers the PDT efficiency of the free complex, while conversely, the cationic PhenAN boosts it. Flow cytometry demonstrates that the uptake efficiency of the three agents reflects the observed differences in PDT efficacy. Additionally, intracellular localization studies show that while [Ru(phen)2BAP](OTf)2 remains confined in vesicular structures, Ru-PhenISA localization is hard to determine due to the very low uptake efficiency. Very interestingly, instead, the cationic Ru-PhenAN accumulates inside the nucleus in all treated cells. Overall, the results indicate that the complexation of [Ru(phen)2BAP](OTf)2 with a cationic polyamidoamine to give the Ru-PhenAN complex is an excellent strategy to increase the Ru-complex cell uptake and, additionally, to achieve accumulation at the nuclear level. These unique features together make this compound an excellent photosensitizer with very high PDT efficiency.