Third-Generation Anticancer Photodynamic Therapy Systems Based on Star-like Anionic Polyacrylamide Polymer, Gold Nanoparticles, and Temoporfin Photosensitizer.

Photodynamic therapy (PDT) is a non-invasive anticancer treatment that uses special photosensitizer molecules (PS) to generate singlet oxygen and other reactive oxygen species (ROS) in a tissue under excitation with red or infrared light. Though the method has been known for decades, it has become more popular recently with the development of new efficient organic dyes and LED light sources. Here we introduce a ternary nanocomposite: water-soluble star-like polymer/gold nanoparticles (AuNP)/temoporfin PS, which can be considered as a third-generation PDT system. AuNPs were synthesized in situ inside the polymer molecules, and the latter were then loaded with PS molecules in an aqueous solution. The applied method of synthesis allows precise control of the size and architecture of polymer nanoparticles as well as the concentration of the components. Dynamic light scattering confirmed the formation of isolated particles (120 nm diameter) with AuNPs and PS molecules incorporated inside the polymer shell. Absorption and photoluminescence spectroscopies revealed optimal concentrations of the components that can simultaneously reduce the side effects of dark toxicity and enhance singlet oxygen generation to increase cancer cell mortality. Here, we report on the optical properties of the system and detailed mechanisms of the observed enhancement of the phototherapeutic effect. Combinations of organic dyes with gold nanoparticles allow significant enhancement of the effect of ROS generation due to surface plasmonic resonance in the latter, while the application of a biocompatible star-like polymer vehicle with a dextran core and anionic polyacrylamide arms allows better local integration of the components and targeted delivery of the PS molecules to cancer cells. In this study, we demonstrate, as proof of concept, a successful application of the developed PDT system for in vitro treatment of triple-negative breast cancer cells under irradiation with a low-power LED lamp (660 nm). We consider the developed nanocomposite to be a promising PDT system for application to other types of cancer.

Poly(vinylidene fluoride)/poly(3-methylthiophene) core-shell nanocomposites with improved structural and electronic properties of the conducting polymer component.

We report significant improvements in the structure and electronic properties of a poly(3-alkylthiophene) representative, namely poly(3-methylthiophene) (P3MT), when it is synthesized in the presence of submicron electroactive poly(vinylidene fluoride) (PVDF) particles. The applied template oxidative synthesis leads to the formation of the PVDF/P3MT composite consisting of core-shell particles. The shells are constituted with a monolayer of 20-40 nm nanoparticles of the doped P3MT (P3MT-Cl) precipitated at the surface of the spherical PVDF cores. This morphology differs strongly from the hierarchical one of the neat P3MT synthesized without PVDF particles. In the latter case, 20-60 nm P3MT nanoparticles form ∼200 nm aggregates, which, in turn, are arranged in a few micrometer agglomerates. Furthermore, we demonstrate that compared to the neat polymer, doped P3MT in the shells of the composite is characterized with higher effective conjugation length, regioregularity of the molecular structure, improved intrachain packing order and lower bipolaron/polaron ratio. These features of the PVDF/P3MT composite strongly suggest applicability of this material in various electronic devices. As a proof of concept, we report on an improved sensing performance of the PVDF/P3MT-Cl composite compared with the neat P3MT-Cl in detection of several volatile organic compounds known as markers for some diseases and toxic substances. We have discovered that the maximal improvement in the sensor response magnitude corresponds to the case when the values of the analyte electronegativity and polythiophene work function are close. We associate this behavior with a higher surface dipole component of the work function of the PVDF/P3MT-Cl composite compared to that of the neat conducting polymer.

Electrical conductivity of insulating polymer nanoscale layers: environmental effects.

As electronic devices are scaled down to submicron sizes, it has become critical to obtain uniform and robust insulating nanoscale polymer films. For that reason, we address the electrical properties of grafted polymer layers made of poly(glycidyl methacrylate), polyacrylic acid, poly(2-vinylpyridine), and polystyrene with thicknesses of 10-20 nm. It was found that layers insulating under normal ambient conditions can display a significant increase in conductivity as the environment changes. Namely, we demonstrated that the in-plane electrical conductivity of the polymer grafted layers can be changed by at least two orders of magnitude upon exposure to water or organic solvent vapors. Conductive properties of all polymer grafted films under study could also be significantly enhanced with an increase in temperature. The observed phenomenon makes possible the chemical design of polymer nanoscale layers with reduced or enhanced sensitivity to the anticipated change in environmental conditions. Finally, we demonstrated that the observed effects could be used in a micron-sized conductometric transducing scheme for the detection of volatile organic solvents.

Formation of surface relief grating in polymers with pendant azobenzene chromophores as studied by AFM/UFM.

We studied peculiarities of the structural reconstruction within holographically recorded gratings on the surface of several different amorphous azobenzene-containing polymers. Under illumination with a light interference pattern, two processes take place in this type of polymer. The first process is the light-induced orientation of azobenzene units perpendicular to the polarization plane of the incident light. The second one is a transfer of macromolecules along the grating vector (i.e. perpendicular to the grating lines). These two processes result in the creation of a volume orientation grating (alternating regions of different direction or degree of molecular orientation) and a surface relief grating (SRG)-i.e. modulation of film thickness. One can assume that both orientation of molecules and their movement might change the local mechanical properties of the material. Therefore, formation of the SRG is expected to result also in modulation of the local stiffness of the polymer film. To reveal and investigate these stiffness changes within the grating, spin-coated polymer films were prepared and the gratings were recorded on them in two different ways: with an orthogonal circular or orthogonal linear polarization of two recording light beams. A combination of atomic force microscopy (AFM) and ultrasonic force microscopy (UFM) techniques was applied for SRG development monitoring. We demonstrate that formation of the phase gratings depends on the chemical structure of polymers being used, polymer film thickness, and recording parameters, with the height of grating structures (depth of modulation) increasing with both the exposure time and the film thickness. UFM images suggest that the slopes of the topographic peaks in the phase gratings exhibit an increased stiffness with respect to the grating depressions.

Efficient Retention and Alpha Spectroscopy of Actinides from Aqueous Solutions Using a Combination of Water-Soluble Star-like Polymers and Ultrafiltration Membranes.

We explored two approaches to recover uranium and plutonium from aqueous solutions at pH 4 and pH 7 using water-soluble star-like polyacrylamide polymers with a dextran core. In the first approach, a solution comprising a neutral or ionomer polymer was mixed with a radionuclide solution to form polymer-metal complexes that were then retained by ultrafiltration (UF) membranes under applied pressure. The same polymers were first deposited on the membrane in the second approach using pressure-driven flow. The applied polymers had an overall diameter of gyration of 120 nm, which exceeded the nominal diameter of the UF membrane pores. The polymers showed a high affinity to uranyl but could also be used to extract Pu from neutral or near-neutral pH solutions. Direct-flow single-step filtration and alpha spectrometry demonstrated that the UF membranes containing star-like copolymers could recover 99% of U and up to 60% of Pu from deionized water after filtering 15 mL solutions containing 25 ppm and 33 ppb of the actinides, correspondingly. The sorption capacity of the polymers for uranium could be measured as 1mg U per mg of the polymer after six subsequent filtration steps. Alpha spectroscopy of the deposited actinides revealed peculiarities of the structural organization of polymers and their complexes with U or Pu, depending on the approach. Though both approaches were efficient, the second approach (deposition of the polymer on the membrane followed by filtration) has an additional advantage of protecting the membrane pores from capillary collapse by filling them with the polymer chains. Therefore, these polymer-modified membranes could be used either in continuous or multi-step filtration process with drying after each step without deterioration of their sorption characteristics.

Application of new covalently-bound diglycolamide sorbent in sequential injection analysis flow system for sample pretreatment in ICP-MS determination of 239Pu at ppt level.

Diglycolamide ligands are widely applied in the analysis of radionuclides, especially lanthanides and actinides. They are used in liquid-liquid extraction procedures or in solid-phase extraction sorbents where they are adsorbed on the surface of hydrophobic polymers. The main objective of this study was to synthesize the N,N,N'N'-tetrahexyl diglycolamide with one vinyl terminating group (vTHDGA) for further covalent immobilization on the polystyrene-divinylbenzene polymeric support. The obtained complexing resin (THDGA) was employed for the mechanized sample pretreatment in the Sequential Injection Analysis - Lab-on-Valve (SIA-LOV) flow system for the determination of 239Pu using ICP-MS detection. The analytical procedure was optimized in terms of selectivity towards several other radionuclides and elements forming potentially isobaric interferences in mass spectrometry. For 100 mL volume of sample to be analyzed, the method detection limit (MDL) was 96 mBq L-1 (42 pg L-1). The developed method was employed for the determination of 239Pu in real samples of a nuclear reactor coolant and spent fuel pool water from a nuclear reactor.

High effectiveness of pure polydopamine in extraction of uranium and plutonium from groundwater and seawater.

Sorption properties of polydopamine (PDA) for uranium and plutonium from an aqueous environment are reported at three different pH values (2, 4 and 6.5-7). In addition to deionized (DI) water, artificial groundwater (GW) and seawater (SW) were used with U uptake close to 100% in each case. PDA polymer has been identified as a material with extremely high sorption capacity Q max ∼500 mg g-1 of the polymer at pH 6.5 and high selectivity for uranium. Similar high sorption properties are revealed for plutonium uptake. PDA-uranyl and PDA-plutonium interactions responsible for the observed adsorption processes have been addressed with a set of experimental techniques including FTIR spectroscopy, electron microscopy and cyclic voltammetry.

Evaluation of Shiryaev-Roberts procedure for on-line environmental radiation monitoring.

Water can become contaminated as a result of a leak from a nuclear facility, such as a waste facility, or from clandestine nuclear activity. Low-level on-line radiation monitoring is needed to detect these events in real time. A Bayesian control chart method, Shiryaev-Roberts (SR) procedure, was compared with classical methods, 3-σ and cumulative sum (CUSUM), for quantifying an accumulating signal from an extractive scintillating resin flow-cell detection system. Solutions containing 0.10-5.0 Bq/L of 99Tc, as T99cO4- were pumped through a flow cell packed with extractive scintillating resin used in conjunction with a Beta-RAM Model 5 HPLC detector. While T99cO4- accumulated on the resin, time series data were collected. Control chart methods were applied to the data using statistical algorithms developed in MATLAB. SR charts were constructed using Poisson (Poisson SR) and Gaussian (Gaussian SR) probability distributions of count data to estimate the likelihood ratio. Poisson and Gaussian SR charts required less volume of radioactive solution at a fixed concentration to exceed the control limit in most cases than 3-σ and CUSUM control charts, particularly solutions with lower activity. SR is thus the ideal control chart for low-level on-line radiation monitoring. Once the control limit was exceeded, activity concentrations were estimated from the SR control chart using the control chart slope on a semi-logarithmic plot. A linear regression fit was applied to averaged slope data for five activity concentration groupings for Poisson and Gaussian SR control charts. A correlation coefficient (R2) of 0.77 for Poisson SR and 0.90 for Gaussian SR suggest this method will adequately estimate activity concentration for an unknown solution.

Photocatalytic activity and NIR laser response of polyaniline conjugated graphene nanocomposite prepared by a novel acid-less method.

Herein, we present a novel acid-less synthetic approach for in-situ polymerization of aniline synchronized with reduction of graphene oxide to graphene. This method provides uniform deposition of ordered polyaniline nanotubes over the surface of graphene nanosheets. The synthesized graphene-polyaniline nanocomposite has the ability of complete removal of harmful dyes commonly used in industry: such as methyl orange, methylene blue, and rhoadmine B from the waste water under the exposure to natural sunlight. The system can be used as an efficient solar energy operated photocatalyst due to effective suppression of recombination of the charge carriers. The unique spatial structure of the graphene-polyaniline nanocomposite has high chemical stability, can be recycled after photolysis, and allows using in multiple cycles without reduction in its photocatalytic activity. In addition, the graphene-polyaniline nanocomposite exhibits strong near-infrared (NIR) absorption, good photothermal stability, as well as shows substantial thermal energy generation under exposure to 808 or 980 nm NIR lasers. The electrical conductivity of polyaniline nanotubes is improved as a result of their conjugation with graphene nanosheets in the nanocomposite. Owing to its outstanding photocatalytic activity and chemical stability, the reported graphene-polyaniline nanocomposite has a great potential in purification of industrially generated waste water.

New Efficient Organic Scintillators Derived from Pyrazoline.

We report on the synthesis, spectroscopic and scintillation properties of three new pyrazoline core based fluorophores. Fluorescence properties of the fluorophores have been studied both in a solution state and in a solid polyvinyltoluene (PVT) resin matrix of different porosity. The synthesized fluorophores were found to be promising candidates for application in plastic scintillators for detection of ionizing radiation (alpha, beta particles, γ rays and neutrons) and demonstrated superior efficiency in comparison to the existing commercially used fluorophores (2-(1-naphthyl)-5-phenyloxazole (αNPO), 9,10-diphenylanthracene, etc.). Moreover, the suggested synthetic route allows functionalization of the fluorophores with a vinyl group for further covalent bound to the PVT or other vinyl polymer matrices, which dramatically improves chemical stability of the system simultaneously improving the photoluminescence quantum yield. Possible mechanisms of the enhanced scintillation properties are discussed based on preliminary quantum mechanical calculations and spectroscopic characteristics of the fluorophores under study.

Dispersion and phase separation of carbon nanotubes in ultrathin polymer films.

The inner structure and nanoscale distribution of the stiffness was studied for polymer-single-wall carbon nanotube composites. Dispersion of nanotubes in a polystyrene and polyurethane polymer matrix was achieved by a proper choice of the organic solvent (NMP) and sonification of polymer/SWNT solutions. Ultrathin nanocomposite films were prepared through a dip-coating procedure and possessed a noticeable degree of nanotube orientation in the direction of the applied shear force. Peculiarities of the phase separation in the films were studied by atomic force microscopy (with application of force modulation mode to map the nanotube distribution within the polymer matrix) and Raman spectroscopy.

How surface topography relates to materials' properties.

The topography of a surface is known to substantially affect the bulk properties of a material. Despite the often nanoscale nature of the surface undulations, the influence they have may be observed by macroscopic measurements. This review explores many of the areas in which the effect of topography is macroscopically relevant, as well as introducing some recent developments in topographic analysis and control.