Sepiolite promotes photodegradation of pyrene under visible light.

Mechanochemistry and photocatalysis are emergent technologies for the remediation of polycyclic aromatic hydrocarbons (PAHs) in soils. In this work, mechanochemistry and photocatalysis are combined for pyrene degradation. The photodegradation of pyrene, when in contact with sepiolite under pressure application, is studied. The mechanical treatment leads to a pyrene crystal phase transformation. In this new phase, pyrene undergoes a fast photodegradation in the 320-420 nm range. We show that sepiolite is superior as a photocatalyst in pyrene degradation to TiO2, the most exploited photocatalyst. A broad physicochemical characterization is carried out to propose a mechanism in which the photoexcitation of mechanically altered pyrene leads to an electron transfer to sepiolite matrix, which triggers the PAH degradation. Finally, we want to highlight that the pyrene/sepiolite combination is a simplified system to shed light on how PAH photodegradation may occur in soils.

Reversible Light-Induced Dimerization of Secondary Face Azobenzene-Functionalized ß-Cyclodextrin Derivatives.

ß-cyclodextrin (ßCyD) derivatives equipped with aromatic appendages at the secondary face exhibit tailorable self-assembling capabilities. The aromatic modules can participate in inclusion phenomena and/or aromatic-aromatic interactions. Supramolecular species can thus form that, at their turn, can engage in further co-assembling with third components in a highly regulated manner; the design of nonviral gene delivery systems is an illustrative example. Endowing such systems with stimuli responsiveness while keeping diastereomeric purity and a low synthetic effort is a highly wanted advancement. Here, we show that an azobenzene moiety can be "clicked" to a single secondary O-2 position of ßCyD affording 1,2,3-triazole-linked ßCyD-azobenzene derivatives that undergo reversible light-controlled self-organization into dimers where the monomer components face their secondary rims. Their photoswitching and supramolecular properties have been thoroughly characterized by UV-vis absorption, induced circular dichroism, nuclear magnetic resonance, and computational techniques. As model processes, the formation of inclusion complexes between a water-soluble triazolylazobenzene derivative and ßCyD as well as the assembly of native ßCyD/ßCyD-azobenzene derivative heterodimers have been investigated in parallel. The stability of the host-guest supramolecules has been challenged against the competitor guest adamantylamine and the decrease of the medium polarity using methanol-water mixtures. The collective data support that the E-configured ßCyD-azobenzene derivatives, in aqueous solution, form dimers stabilized by the interplay of aromatic-aromatic and aromatic-ßCyD cavity interactions after partial reciprocal inclusion. Photoswitching to the Z-isomer disrupts the dimers into monomeric species, offering opportunity for the spatiotemporal control of the organizational status by light.

Enhanced Gene Delivery Triggered by Dual pH/Redox Responsive Host-Guest Dimerization of Cyclooligosaccharide Star Polycations.

A robust strategy is reported to build perfectly monodisperse star polycations combining a trehalose-based cyclooligosaccharide (cyclotrehalan, CT) central core onto which oligoethyleneimine radial arms are installed. The architectural perfection of the compounds is demonstrated by a variety of physicochemical techniques, including NMR, MS, DLS, TEM, and GPC. Key to the strategy is the possibility of customizing the cavity size of the macrocyclic platform to enable/prevent the inclusion of adamantane motifs. These properties can be taken into advantage to implement sequential levels of stimuli responsiveness by combining computational design, precision chemistry and programmed host-guest interactions. Specifically, it is shown that supramolecular dimers implying a trimeric CT-tetraethyleneimine star polycation and purposely designed bis-adamantane guests are preorganized to efficiently complex plasmid DNA (pDNA) into transfection-competent nanocomplexes. The stability of the dimer species is responsive to the protonation state of the cationic clusters, resulting in dissociation at acidic pH. This process facilitates endosomal escape, but reassembling can take place in the cytosol then handicapping pDNA nuclear import. By equipping the ditopic guest with a redox-sensitive disulfide group, recapturing phenomena are prevented, resulting in drastically improved transfection efficiencies both in vivo and in vitro.

Colored Surfaces Made of Synthetic Eumelanin.

The polymerization of 3,4-dihydroxy-L-phenylalanine leads to a carboxylic acid-rich synthetic melanin-like material (poly-L-DOPA). Synthetic melanin most resembles natural eumelanin in chemical structure. However, its deposition on surfaces leading to colored surfaces by interference is not as easy to accomplish as in the case of the preparation of colored surfaces by dopamine hydrochloride polymerization. This study deals with the preparation of new colored surfaces made from poly-L-DOPA displaying vivid colors by interference. These surfaces were obtained by depositing thin films of poly-L-DOPA on a reflective silicon nitride substrate. A high ionic strength in the polymerization medium was essential to accomplish the coating. The effect of ionic strength on the resulting surfaces was studied via reflectance, Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). The refractive index was determined by ellipsometry, and was nearly constant to 1.8 when λ > 650 nm. In the visible spectral region, the imaginary part of the refractive index becomes relevant. The refractive index in the visible wavelength range (400-600 nm) was in the range 1.7-1.80.

Antineoplastic behavior of polydopamine nanoparticles prepared in different water/alcohol media.

Polydopamine nanoparticles (PD NPs) have been synthesized in the present work through the oxidative polymerization of dopamine in aqueous media containing five different types of alcohol in a constant solvent volume ratio. We have shown that the type of alcohol, along with the ammonium hydroxide concentration used in the synthesis process, conditions particle size. Additionally, it has been found that the type of alcohol employed influences the well-known capacity of polydopamine nanoparticles to adsorb iron. As a consequence, since a ferroptosis-like mechanism may account for the cytotoxicity of these nanoparticles, the type of alcohol could also have a determining role in their antineoplastic activity. Here, the existence of a correlation between the ability of polydopamine nanoparticles to load Fe3+ and their toxic effect on breast cancer cells has been proven. For instance, nanoparticles synthesized using 2-propanol adsorbed more Fe3+ and had the greatest capacity to reduce breast tumor cell viability. Moreover, none of the nanoparticle synthesized with the different alcohols significantly decreased normal cell survival. Cancer cells present greater iron-dependence than healthy cells and this fact may explain why polydopamine nanoparticles toxicity, in which Fenton chemistry could be implicated, seems tumor-specific.

Click Synthesis of Size- and Shape-Tunable Star Polymers with Functional Macrocyclic Cores for Synergistic DNA Complexation and Delivery.

The architectural perfection and multivalency of dendrimers have made them useful for biodelivery via peripheral functionalization and the adjustment of dendrimer generations. Modulation of the core-forming and internal matrix-forming structures offers virtually unlimited opportunities for further optimization, but only in a few cases this has been made compatible with strict diastereomeric purity over molecularly diverse series, low toxicity, and limited synthetic effort. Fully regular star polymers built on biocompatible macrocyclic platforms, such as hyperbranched cyclodextrins, offer advantages in terms of facile synthesis and flexible compositions, but core elaboration in terms of shape and function becomes problematic. Here we report the synthesis and characterization of star polymers consisting of functional trehalose-based macrocyclic cores (cyclotrehalans, CTs) and aminothiourea dendron arms, which can be efficiently synthesized from sequential click reactions of orthogonal monomers, display no cytotoxicity, and efficiently complex and deliver plasmid DNA in vitro and in vivo. When compared with some commercial cationic dendrimers or polymers, the new CT-scaffolded star polymers show better transfection efficiencies in several cell lines and structure-dependent cell selectivity patterns. Notably, the CT core could be predefined to exert Zn(II) complexing or molecular inclusion capabilities, which has been exploited to synergistically boost cell transfection by orders of magnitude and modulate the organ tropism in vivo.

Tuning the Topological Landscape of DNA-Cyclodextrin Nanocomplexes by Molecular Design.

Original molecular vectors that ensure broad flexibility to tune the shape and surface properties of plasmid DNA (pDNA) condensates are reported herein. The prototypic design involves a cyclodextrin (CD) platform bearing a polycationic cluster at the primary face and a doubly linked aromatic module bridging two consecutive monosaccharide units at the secondary face that behaves as a topology-encoding element. Subtle differences at the molecular level then translate into disparate morphologies at the nanoscale, including rods, worms, toroids, globules, ellipsoids, and spheroids. In vitro evaluation of the transfection capabilities revealed marked selectivity differences as a function of nanocomplex morphology. Remarkably high transfection efficiencies were associated with ellipsoidal or spherical shapes with a lamellar internal arrangement of pDNA chains and CD bilayers. Computational studies support that the stability of such supramolecular edifices is directly related to the tendency of the molecular vector to form noncovalent dimers upon DNA templating. Because the stability of the dimers depends on the protonation state of the polycationic clusters, the coaggregates display pH responsiveness, which facilitates endosomal escape and timely DNA release, a key step in successful transfection. The results provide a versatile strategy for the construction of fully synthetic and perfectly monodisperse nonviral gene delivery systems uniquely suited for optimization schemes.

A comprehensive study on levan nanoparticles formation: Kinetics and self-assembly modeling.

Levan nanoparticles formation is a complicated phenomenon involving simultaneously polymeric reaction kinetics and nanoparticles self-assembly theory. These phenomena are studied in this work with experimental and computational methodologies. Specifically, the effect of different parameters on levan kinetics and nanoparticles production in a cell-free system environment have been studied. Results point out that 37 °C is the best temperature for synthesizing levan as well as the existence of a substrate inhibition effect for polymeric reaction. This work also highlights that raffinose can be used for producing and that an increase on the ratio enzyme-substrate increases the velocity of conversion. However, the previous experimental conditions did not produce an important effect on self-assembly formed levan nanoparticles (always 110 nm) as long as the required levan concentration (CAC) for nanoparticles reorganization is achieved. To have a better understanding of these results, a model was developed to explain numerically levan kinetics and nanoparticle self-assembly. This model was built by taking into account enzyme poisoning effect (also demonstrated experimentally) and a diffusion limited cluster model for the aggregation phenomenon. Simulation results fit properly experimental data and catalytic parameters as well as predicting accurately the value of CAC for producing its reorganization into nanoparticles by self-assembly.

Size Matters in the Cytotoxicity of Polydopamine Nanoparticles in Different Types of Tumors.

Polydopamine has acquired great relevance in the field of nanomedicine due to its physicochemical properties. Previously, it has been reported that nanoparticles synthetized from this polymer are able to decrease the viability of breast and colon tumor cells. In addition, it is well known that the size of therapeutic particles plays an essential role in their effect. As a consequence, the influence of this parameter on the cytotoxicity of polydopamine nanoparticles was studied in this work. For this purpose, polydopamine nanoparticles with three different diameters (115, 200 and 420 nm) were synthetized and characterized. Their effect on the viability of distinct sorts of human carcinomas (breast, colon, liver and lung) and stromal cells was investigated, as well as the possible mechanisms that could be responsible for such cytotoxicity. Moreover, polydopamine nanoparticles were also loaded with doxorubicin and the therapeutic action of the resulting nanosystem was analyzed. As a result, it was demonstrated that a smaller nanoparticle size is related to a more enhanced antiproliferative activity, which may be a consequence of polydopamine's affinity for iron ions. Smaller nanoparticles would be able to adsorb more lysosomal Fe3+ and, when they are loaded with doxorubicin, a synergistic effect can be achieved.

Differences in levan nanoparticles depending on their synthesis route: Microbial vs cell-free systems.

Differences between the levan obtained from bacteria and from cell-free systems were studied in this work. Results showed that both polymers are non-porous solids (type II isotherm with 20 m2/g) with a main thermal decomposition at 200 °C and a negligible value of protein adsorption. Microbial levan produced nanoparticles of 90 nm in diameter whereas nanoparticles of 110 nm were obtained with the polymer obtained from a cell-free system. Both polymers behave as aggregates depending on the critical aggregation concentration. At the same time, that concentration depends on the technique used for the polymer synthesis. Cell-free system aggregation concentration is 0.24 mg/mL whereas a concentration of 0.05 mg/mL was found for the microbial system. In both cases, the average molecular weight of the aggregate is higher than 2000 kDa. These results highlight the existence of aggregation equilibrium for both polymers that has to be taken into account for future applications.

Color Engineering of Silicon Nitride Surfaces to Characterize the Polydopamine Refractive Index.

A simple methodology to generate polydopamine (PDA) surfaces featured with color due to thin-film interference phenomena is presented. It is based on depositing ultra-thin films of polydopamine on a Si/Si3 N4 wafer that exhibits an interferential reflectance maximum right at the visible/UV boundary (∼400 nm). Therefore, a small deposit of PDA modifies the optical path, in such manner that the wavelength of the maximum of reflectance red shifts. Because the human eye is very sensitive to any change of the light spectral distribution at the visible region, very small film thickness changes (∼30 nm) are enough to notably modify the perceived color. Consequently, a controlled deposit of PDA, tune the color along the whole visible spectrum. Additionally, good quality of PDA deposits allowed us to determine the refractive index of polydopamine by ellipsometry spectroscopy. This data can be crucial in confocal skin microscopic techniques, presently used in diagnosis of skin tumors.

Cytotoxicity of paramagnetic cations-Loaded polydopamine nanoparticles.

Polydopamine (PD) is a synthetic melanin pigment of great importance in biomedicine, where its affinity for metallic cations, especially paramagnetic ions, has sparked interest in its use in the development of magnetic resonance imaging (MRI) contrast agents. In this work, we report the cytotoxicity of metal-enriched PD nanoparticles on NIH3T3, a healthy cell line and BT474, a breast cancer cell line. Remarkably, it was found that the metal- enriched PD particles (Mn+ = Fe3+, Fe2+ and Cu2+) were highly cytotoxic to the breast cancer cells, even after 24 h of treatment. Although, this effect was not selective systems, since an acute cytotoxic effect was also observed on the healthy cell line, this system can be considered as starting point for designing advanced antineoplastic agents.

Polydopamine nanoparticles kill cancer cells.

Polydopamine (PD) is a synthetic melanin analogue of growing importance in the field of biomedicine, especially with respect to cancer research, due, in part, to its biocompatibility. But little is known about the cytotoxic effects of PD on cancer cell lines. PD is a UV-vis absorbing material whose absorbance overlaps with that of formazan salts, which are used to assess cell viability in MTT assays. In this study, a protocol has been established to eliminate the contributing absorbance of PD at 550 nm, and has been applied to characterize the cytotoxicity of PD nanoparticles in both healthy and breast cancer cell lines. Once the protocol is applied, it was found that PD is per se an antineoplastic system, meaning it selectively kills cancer cells, especially those of breast cancer, but it has no toxic effect on healthy cells. The mechanism of action could be related to the production of ROS and the alteration of iron homeostasis in lysosomes. To the best of our knowledge there are only a few examples of nanoparticle systems devoid of drugs that selectively kill cancer cells.

Versatile Tetrablock Copolymer Scaffold for Hierarchical Colloidal Nanoparticle Assemblies: Synthesis, Characterization, and Molecular Dynamics Simulation.

A unique combination of molecular dynamics (MD) simulation and detailed size exclusion chromatography-multiangle light scattering (SEC-MALS) analysis is used to provide important a priori insights into the solution self-assembly of a well-defined and symmetric tetrablock copolymer with two acrylic acid (AA) outer blocks, two polystyrene (PS) inner blocks, and a trithiocarbonate (TTC) central group, prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization. SEC-MALS experiments show that the copolymer forms aggregates in both tetrahydrofuran and N,N-dimethylformamide (DMF), even in the presence of different salts, but not in 1,4-dioxane (dioxane). Combined with MD simulations, these results indicate that the AA units are the main cause of aggregation through intermolecular hydrogen bonding, with additional stabilization by the central TTC. The block copolymer chains self-assemble in dioxane by adding cadmium acetate, originating flowerlike inverse micelles with a cadmium acrylate core and the TTC groups in the outer surface of the PS corona. The micelles were used as nanoreactors in the templated synthesis of a single cadmium selenide (CdSe) quantum dot (QD) in the core of each micelle, whereas the shell TTC groups can be converted into thiol functions for further use of these units in hierarchical nanostructures. Only in dioxane where simulations and SEC-MALS suggest an absence of copolymer aggregates prior to cadmium acetate addition do well-dispersed and highly luminescent CdSe QDs form by templated synthesis. These results provide valuable insights into the self-assembly of RAFT copolymers in different solvent systems as it relates to the preparation of emissive QDs with polymer-spaced thiol functionality for binding to gold nanostructures.

Host-Guest-Mediated DNA Templation of Polycationic Supramolecules for Hierarchical Nanocondensation and the Delivery of Gene Material.

Only a few examples of monodisperse molecular entities that can compact exogenous nucleic acids into nanocomplexes, protect the cargo from the biological environment, facilitate cell internalization, and promote safe transfection have been reported up to date. Although these species open new venues for fundamental studies on the structural requirements that govern the intervening processes and their application in nonviral gene-vector design, the synthesis of these moieties generally requires a relatively sophisticated chemistry, which hampers further development in gene therapy. Herein, we report an original strategy for the reversible complexation and delivery of DNA based on the supramolecular preorganization of a ß-cyclodextrin-scaffolded polycationic cluster facilitated by bisadamantane guests. The resulting gemini-type, dual-cluster supramolecules can then undergo DNA-templated self-assembly at neutral pH value by bridging parallel DNA oligonucleotide fragments. This hierarchical DNA condensation mechanism affords transfectious nanoparticles with buffering capabilities, thus facilitating endosomal escape following cell internalization. Protonation also destabilizes the supramolecular dimers and consequently the whole supramolecular edifice, thus assisting DNA release. Our advanced hypotheses are supported by isothermal titration calorimetry, NMR and circular dichroism spectroscopic analysis, gel electrophoresis, dynamic light scattering, TEM, molecular mechanics, molecular dynamics, and transfection studies conducted in vitro and in vivo.

Interaction of gold nanoparticles with Doxorubicin mediated by supramolecular chemistry.

A copolymer containing ß-cyclodextrin, catechol and polyethylene glycol groups in its side chain was designed for the in situ synthesis and coating of gold nanoparticles (Au@PEG-CD NPs). These platforms were designed as a smart carrier and traceable delivery probe of the chemotherapeutic Doxorubicin drug (Dox). The coated polymer forms stable complexes with Dox in water with a high binding constant (K=2.3×10(4) M(-1) at 25°C), which is one hundred times greater than those reported for its complexation with native ßCD. Therefore, Au@PEG-CD NPs were able to load 0.01 mg of the drug per mg of NP and to release up to 60% of it in 48 h at 37°C. In addition, Au@PEG-CD NPs had the capacity to act as a quencher of Dox fluorescence when it was complexed with ßCD in the NP organic shell. This feature allows the Dox release to be tracked by monitoring the recovery of its fluorescence in real time. Therefore, the Dox release kinetics and the influence of temperature on the thermal stability of Dox/CD complexes on Au@PEG-CD NP were investigated. The increase in temperature favors the dissociation of the complexes and subsequent Dox release from the NP. The first order rate constant for drug releasing was 1.1×10(-2) min(-1) with a half-life time of 63 min at 37°C. Finally, the great potential of the carrier/probe double nature of Au@PEG-CD NPs was demonstrated in real time inside HeLa cells.

Nonlinear emission of quinolizinium-based dyes with application in fluorescence lifetime imaging.

Charged molecules based on the quinolizinum cation have potential applications as labels in fluorescence imaging in biological media under nonlinear excitation. A systematic study of the linear and nonlinear photophysics of derivatives of the quinolizinum cation substituted by either dimethylaniline or methoxyphenyl electron donors is performed. The effects of donor strength, conjugation length, and symmetry in the two-photon emission efficiency are analyzed in detail. The best performing nonlinear fluorophore, with two-photon absorption cross sections of 1140 GM and an emission quantum yield of 0.22, is characterized by a symmetric D-π-A(+)-π-D architecture based on the methoxyphenyl substituent. Application of this molecule as a fluorescent marker in optical microscopy of living cells revealed that, under favorable conditions, the fluorophore can be localized in the cytoplasmatic compartment of the cell, staining vesicular shape organelles. At higher dye concentrations and longer staining times, the fluorophore can also penetrate into the nucleus. The nonlinearly excited fluorescence lifetime imaging shows that the fluorophore lifetime is sensitive to its location in the different cell compartments. Using fluorescence lifetime microscopy, a multicolor map of the cell is drafted with a single dye.

Polymer-coated nanoparticles by adsorption of hydrophobically modified poly(N,N-dimethylacrylamide).

We prepared a reactive random copolymer of N-acryloxysuccinimide and N,N-dimethylacrylamide (DMA) by reversible addition-fragmentation chain transfer polymerization, with Mn ≈ 50k and 23 mol % reactive NAS groups. This copolymer was subsequently modified with hydrophobic (dodecyl) and fluorescent (pyrene, PY; phenanthrene, PHE; or anthracene, AN) side groups, to obtain fluorescent amphiphilic polymers with the same backbone and different substituents. These polymers were adsorbed onto model (ca. 130 nm diameter) poly(butyl methacrylate) nanoparticles, and the size and structure of the adsorbed layer were evaluated using a combination of fluorescence techniques and light scattering. The total diameter increases very fast with polymer concentration up to ca. 140 nm, and then more slowly to 154 nm, stabilizing at this value which corresponds to a polymer shell thickness of ca. 12 nm. In order to evaluate the distribution of hydrophobic groups on the adsorbed polymer layer, we used Förster resonance energy transfer between PHE- and AN-labeled poly(DMA) chains. The obtained concentration profile of the adsorbed polymer corresponds to a coated particle radius which is only slightly smaller than the hydrodynamic radius measured in the same conditions, indicating that the dyes are not located at the particle interface but mostly distributed across the adsorbed layer. Finally, we observed that hydrophobically modified PHE-labeled poly(DMA) chains adsorbed to the nanoparticles were very efficiently displaced by identical hydrophobically modified chains with five times their molecular weight (Mn ≈ 250k) but labeled with PY.

Hybrid materials: Magnetite-Polyethylenimine-Montmorillonite, as magnetic adsorbents for Cr(VI) water treatment.

Hybrid materials formed by the combination of a sodium rich Montmorillonite (MMT), with magnetite nanoparticles (40 nm, Fe(3)O(4) NPs) coated with Polyethylenimine polymer (PEI 800 g/mol or PEI 25000 g/mol) were prepared. The intercalation of the magnetite nanoparticles coated with PEI among MMT platelets was achieved by cationic exchange. The resulting materials presented a high degree of exfoliation of the MMT sheets and a good dispersion of Fe(3)O(4) NPs on both the surface and among the layers of MMT. The presence of amine groups in the PEI structure not only aids the exfoliation of the MMT layers, but also gives to the hybrid material the necessary functionality to interact with heavy metals. These hybrid materials were used as magnetic sorbent for the removal of hexavalent chromium from water. The effect that pH, Cr(VI) concentration, and adsorbent material composition have on the Cr(VI) removal efficiency was studied. A complete characterization of the materials was performed. The hybrid materials showed a slight dependence of the removal efficiency with the pH in a wide range (1-9). A maximum amount of adsorption capacity of 8.8 mg/g was determined by the Langmuir isotherm. Results show that these hybrid materials can be considered as potential magnetic adsorbent for the Cr(VI) removal from water in a wide range of pH.

A V-shaped cationic dye for nonlinear optical bioimaging.

A symmetric cationic molecule with D-π-A(+)-π-D architecture was synthesized with high two-photon absorption cross-section (σ(2) ≈ 1140 GM). Application as a marker in fluorescence microscopy of living cells revealed its presence inside the cell staining vesicular shape organelles in the cytoplasm. Fluorescence lifetime imaging microscopy shows that it is also able to penetrate within the nucleus.