The importance of anchoring ligands of binuclear sensitizers on electron transfer processes and photovoltaic action in dye-sensitized solar cells.

The relatively low photon-to-current conversion efficiency of dye-sensitized solar cells is their major drawback limiting widespread application. Light harvesting, followed by a series of electron transfer processes, is the critical step in photocurrent generation. An in-depth understanding and fine optimization of those processes are crucial to enhance cell performance. In this work, we synthesize two new bi-ruthenium sensitizers with extended anchoring ligands to gain insight into underlying processes determining photovoltaic action mechanisms. The structure of the compounds has been confirmed, and their properties have been thoroughly examined by various techniques such as NMR, IR, elemental analysis UV-Vis, cyclic voltammetry, and electroabsorption. The experimental characterization has been supported and developed via extensive quantum-chemical calculations, giving a broad view of the presented molecules' properties. Finally, the DSSC devices have been assembled utilizing obtained dyes. The photovoltaic and EIS measurements, combined with performed calculations and fundamental dyes characterization, unraveled an intramolecular electron transfer as an initial step of the electron injection process at the dye/semiconductor interface. The overall photovoltaic action mechanism has been discussed. Our study demonstrates the significance of the anchoring group architecture in the molecular design of new sensitizers for DSSC applications.

Interfacial Behavior of Cubosomes: Combined Langmuir-Blodgett/Langmuir-Schaefer and AFM Investigations.

The Langmuir technique was applied for the first time to compare the layers obtained by spreading lipid liquid-crystalline nanoparticles monoolein 1-oleoyl-rac-glycerol (GMO)/Pluronic F108 cubosomes with the monolayers obtained by mixing the same components in chloroform at the air-water interface. The differences in the monolayer behavior and in the acting intermolecular forces were examined. The similarity of the isotherms obtained for the mixed components system and the cubosome-derived layer proved the disintegration of cubosomes into a single monolayer upon contact with the air-water interface. Despite the low Pluronic F108 content in both types of layers, a strong structural role of this stabilizer was also demonstrated. Cubosome-derived systems supported on hydrophilic mica substrates were prepared either using the combined Langmuir-Blodgett and Langmuir-Schaefer technique or via direct adsorption from the solution. The topographies of the obtained layers were studied by atomic force microscopy (AFM). Images obtained in the air mode revealed the disintegration of cubosomes and the formation of large crystallized structures of the polymer, while AFM imaging performed in water confirmed the presence of intact cubosomes on the surface of mica. We proved that the original structure of cubosomes remains on one condition: the films must not dry out; therefore, the aqueous environment must be preserved. This new approach provides an explanation in the ongoing discussion of what happens to lipid nanoparticles with or without cargo when they come into contact with an interface.

Gelatin methacrylate hydrogel with drug-loaded polymer microspheres as a new bioink for 3D bioprinting.

3D bioprinted hydrogel constructs are advanced systems of a great drug delivery application potential. One of the bioinks that has recently gained a lot of attention is gelatin methacrylate (GelMA) hydrogel exhibiting specific properties, including UV cross-linking possibility. The present study aimed to develop a new bioink composed of GelMA and gelatin modified by addition of polymer (polycaprolactone or polyethersulfone) microspheres serving as bioactive substance carriers. The prepared microspheres suspension in GelMA/gelatin bioink was successfully bioprinted and subjected to various tests, which showed that the addition of microspheres and their type affects the physicochemical properties of the printouts. The hydrogel stability and structure was examined using scanning electron and optical microscopy, its thermal properties with differential scanning calorimetry and thermogravimetric analysis and its biocompatibility on HaCaT cells using viability assay and electron microscopy. Analyses also included tests of hydrogel equilibrium swelling ratio and release of marker substance. Subsequently, the matrices were loaded with ampicillin and the antibiotic release was validated by monitoring the antibacterial activity on Staphylococcus aureus and Escherichia coli. It was concluded that GelMA/gelatin bioink is a good and satisfying material for potential medical use. Depending on the polymer used, the addition of microspheres improves its structure, thermal and drug delivery properties.

Electrospun UV-cross-linked polyvinylpyrrolidone fibers modified with polycaprolactone/polyethersulfone microspheres for drug delivery.

Electrospun fibers, often used as drug delivery systems, have two drawbacks - in the first stage of their action a sudden active substance burst release occurs and they have a relatively small capacity for a drug. In this work the fibers are modified by the addition of drug-loaded microspheres acting as micro-containers for the drug and increasing the total drug capacity of the system. Its release from such a structure is slowed down by placing the microspheres inside the fibers so they are covered with an outer layer of fiber-forming polymer. The work presents a new method (microsphere suspension electrospinning) of obtaining polyvinylpyrrolidone fibers cross-linked with UV light modified with polycaprolactone/polyethersulphone microspheres loaded with active substance - rhodamine 640 as a marker or ampicillin as a drug example. The influence of UV-cross-linking time and the microspheres addition on the degradation, mechanical strength and transport properties of fibrous mats was investigated. The mats were insoluble in water, in some cases mechanically stronger, their drug capacity was increased and the burst effect was eliminated. The antibacterial properties of ampicillin-loaded mats were confirmed. The product of proposed suspension electrospinning process has application potential as a drug delivery system.

Simvastatin Coadministration Modulates the Electrostatically Driven Incorporation of Doxorubicin into Model Lipid and Cell Membranes.

Understanding the interactions between drugs and lipid membranes is a prerequisite for finding the optimal way to deliver drugs into cells. Coadministration of statins and anticancer agents has been reported to have a positive effect on anticancer therapy. In this study, we elucidate the mechanism by which simvastatin (SIM) improves the efficiency of biological membrane penetration by the chemotherapeutic agent doxorubicin (DOX) in neutral and slightly acidic solutions. The incorporation of DOX, SIM, or a combination of them (DOX:SIM) into selected single-component lipid membranes, zwitterionic unsaturated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), neutral cholesterol, and negatively charged 1,2-dimyristoyl-sn-glycero-3-phospho-l-serine (DMPS) was assessed using the Langmuir method. The penetration of neutral lipid monolayers by the codelivery of SIM and DOX was clearly facilitated at pH 5.5, which resembles the pH conditions of the environment of cancer cells. This effect was ascribed to partial neutralization of the DOX positive charge as the result of intermolecular interactions between DOX and SIM. On the other hand, the penetration of the negatively charged DMPS monolayer was most efficient in the case of the positively charged DOX. The efficiency of the drug delivery to the cell membranes was evaluated under in vitro conditions using a panel of cancer-derived cell lines (A172, T98G, and HeLa). MTS and trypan blue exclusion assays were performed, followed by confocal microscopy and spheroid culture tests. Cells were exposed to either free drugs or drugs encapsulated in lipid carriers termed cubosomes. We demonstrated that the viability of cancer cells exposed to DOX was significantly impaired in the presence of SIM, and this phenomenon was greatly magnified when DOX and SIM were coencapsulated in cubosomes. Overall, our results confirmed the utility of the DOX:SIM combination delivery, which enhances the interactions between neutral components of cell membranes and positively charged chemotherapeutic agents.

The TiO2-ZnO Systems with Multifunctional Applications in Photoactive Processes-Efficient Photocatalyst under UV-LED Light and Electrode Materials in DSSCs.

The main goal of the study was the hydrothermal-assisted synthesis of TiO2-ZnO systems and their subsequent use in photoactive processes. Additionally, an important objective was to propose a method for synthesizing TiO2-ZnO systems enabling the control of crystallinity and morphology through epitaxial growth of ZnO nanowires. Based on the results of X-ray diffraction analysis, in the case of materials containing a small addition of ZnO (≥5 wt.%), no crystalline phase of wurtzite was observed, proving that a high amount of modified titanium dioxide can inhibit the crystallization of ZnO. The transmission electron microscopy (TEM) results confirmed the formation of ZnO nanowires for systems containing ≥ 5% ZnO. Moreover, for the synthesized systems, there were no significant changes in the band gap energy. One of the primary purposes of this study was to test the TiO2-ZnO system in the photodegradation process of 4-chlorophenol using low-power UV-LED lamps. The results of photo-oxidation studies showed that the obtained binary systems exhibit good photodegradation and mineralization efficiency. Additionally, it was also pointed out that the dye-sensitized solar cells can be a second application for the synthesized TiO2-ZnO binary systems.

How Can the Introduction of Zr4+ Ions into TiO2 Nanomaterial Impact the DSSC Photoconversion Efficiency? A Comprehensive Theoretical and Experimental Consideration.

A series of pure and doped TiO2 nanomaterials with different Zr4+ ions content have been synthesized by the simple sol-gel method. Both types of materials (nanopowders and nanofilms scratched off of the working electrode's surface) have been characterized in detail by XRD, TEM, and Raman techniques. Inserting dopant ions into the TiO2 structure has resulted in inhibition of crystal growth and prevention of phase transformation. The role of Zr4+ ions in this process was explained by performing computer simulations. The three structures such as pure anatase, Zr-doped TiO2, and tetragonal ZrO2 have been investigated using density functional theory extended by Hubbard correction. The computational calculations correlate well with experimental results. Formation of defects and broadening of energy bandgap in defected Zr-doped materials have been confirmed. It turned out that the oxygen vacancies with substituting Zr4+ ions in TiO2 structure have a positive influence on the performance of dye-sensitized solar cells. The overall photoconversion efficiency enhancement up to 8.63% by introducing 3.7% Zr4+ ions into the TiO2 has been confirmed by I-V curves, EIS, and IPCE measurements. Such efficiency of DSSC utilizing the working electrode made by Zr4+ ions substituted into TiO2 material lattice has been for the first time reported.

Incorporation of simvastatin into lipid membranes: Why deliver a statin in form of inclusion complex with hydrophilic cyclodextrin.

In this work, the effects of simvastatin (SIM), (2-hydroxypropyl)-ß-cyclodextrin (HPßCD) and their complex (SIM:HPßCD) on the structure and properties of lipid membranes were investigated for the first time by Langmuir technique combined with PM-IRRAS spectroscopy. An improved understanding of the differences of the interactions between free SIM, and SIM in the form of an inclusion complex with HPßCD with the lipid membrane will improve the development of preparation methods for in vivo applications. Monolayers of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), cholesterol (Chol) and their mixture DMPC:Chol (7:3) served as simple models of one leaflet of the cell membrane. The penetration of well-organized lipid layers by simvastatin lead to their fluidization but the extent of this unwanted effect was smaller when the drug was delivered in the form of the SIM:HPßCD complex. Surface pressure vs. time dependencies showed that the drug encapsulated with cyclodextrin dissociated from the complex upon contact with the lipid layer and the weak interactions between the exterior polar part of the HPßCD and the polar headgroups of the lipid layer facilitated smooth incorporation of the released lipophilic drug into the membrane. At a longer time-scale, the HPßCD ligand released from the complex removed some cholesterol, but not DMPC, from the lipid layer, hence, similarly to the enzyme inhibiting action of statins - it lead to the decrease of the amount of cholesterol in the membrane. Delivery of simvastatin in the form of an inclusion complex with HPßCD is proposed as an approach improving its bioavailability in the cholesterol-lowering therapies.

2-Thiohydantoin Moiety as a Novel Acceptor/Anchoring Group of Photosensitizers for Dye-Sensitized Solar Cells.

Very recently, we have reported the synthesis and evaluation of biological properties of new merocyanine dyes composed of triphenylamine moiety, π-aromatic spacer, and rhodanine/2-thiohydantoin-based moiety. Interestingly, 2-thiohydantoin has never been studied before as an electron-accepting/anchoring group for the dye-sensitized solar cells (DSSCs). In the presented study, we examined the applicability of 2-thiohydantoin, an analog of rhodanine, in DSSC technology. The research included theoretical calculations, electrochemical measurements, optical characterization, and tests of the solar cells. As a result, we proved that 2-thiohydantoin might be considered as an acceptor/anchoring group since all the compounds examined in this study were active. The most efficient device showed power conversion efficiency of 2.59%, which is a promising value for molecules of such a simple structure. It was found that the cells' performances were mainly attributed to the dye loading and the ICT molecular absorption coefficients, both affected by the differences in the chemical structure of the dyes. Moreover, the effect of the aromatic spacer size and the introduction of carboxymethyl co-anchoring group on photovoltaic properties was observed and discussed.

[Experimental assessment of exposure to the tobacco smoke and its effect on superoxide dismutase and glutathione peroxidase activities]. / Wplyw stezenia dymu tytoniowego i czasu narazenia na aktywnosc wybranych enzymów antyoksydacyjnych--badania eksperymentalne.

Activities of two antioxidant enzymes, superoxide dismutase (SOD) and glutathione peroxidase (GPx) were determined in plasma of rats exposed to tobacco smoke (500, 1000 and 1500 mg CO/m3 air in 5 days) and to 1000 mg CO/m3 in 1, 2 and 3 weeks. When compared to controls, the SOD activity was decreased in the exposed animals, the lowest smoke dose gave the most pronounced effect and the highest dose revealed the least diminution. GPx activity was statistically higher in the rats inhaled with the highest smoke dose. Time of exposure did not effect GPx but SOD raised in correlation to week number, although it did not reach control values over the experiment period. The observed alterations in plasma probably mirror the organ adaptation to oxidative stress in animals exposed to tobacco smoke.