Radiation-induced graft polymerization of elastin onto polyvinylpyrrolidone as a possible wound dressing.

The purpose of our study was to obtain new wound dressings in the form of hydrogels that promote wound healing taking advantage of the broad activities of elastin (ELT) in physiological processes. The hydrogel of ELT and polyvinylpyrrolidone (PVP; ELT-PVP) was obtained by cross-linking induced by gamma irradiation at a dose of 25 kGy. The physicochemical changes attributed to cross-linking were analyzed through scanning electron microscopy (SEM), infrared spectroscopy analysis with Fourier transform (FTIR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Furthermore, we performed a rheological study to determine the possible changes in the fluidic macroscopic properties produced by the cross-linking method. Finally, we accomplished viability and proliferation analyses of human dermal fibroblasts in the presence of the hydrogel to evaluate its biological characteristics. The hydrogel exhibited a porous morphology, showing interconnected porous with an average pore size of 16 ± 8.42 µm. The analysis of FTIR, DSC, and TGA revealed changes in the chemical structure of the ELT-PVP hydrogel after the irradiation process. Also, the hydrogel exhibited a rheological behavior of a pseudoplastic and thixotropic fluid. The hydrogel was biocompatible, demonstrating high cell viability, whereas ELT presented low biocompatibility at high concentrations. In summary, the hydrogel obtained by gamma irradiation revealed the appropriate morphology to be applied as a wound dressing. Interestingly, the hydrogel exhibited a higher percentage of cell viability compared with ELT, suggesting that the cross-linking of ELT with PVP is a suitable strategy for biological applications of ELT without generating cellular damage.

Rapid isolation and purification of functional platelet mitochondria using a discontinuous Percoll gradient.

The isolation of mitochondria is gaining importance in experimental and clinical laboratory settings. The mitochondrion is known as the powerhouse of the cell as it produces the energy to power most cellular functions but is also involved in many cellular processes. Of interest, mitochondria and mitochondrial components (i.e. circular DNA, N-formylated peptides, cardiolipin) have been involved in several human inflammatory pathologies, such as cancer, Alzheimer's disease, Parkinson's disease, and rheumatoid arthritis. Therefore, stringent methods of isolation and purification of mitochondria are of the utmost importance in assessing mitochondrial-related diseases. While several mitochondrial isolation methods have been previously published, these techniques are aimed at yielding mitochondria from cells types other than platelets. In addition, little information is known on the number of platelet-derived microparticles that can contaminate the mitochondrial preparation or even the overall quality and integrity of the mitochondria. In this project, we provide an alternate purification method yielding mitochondria of high purity and integrity from human platelets. Using human platelets, flow cytometry and transmission electron microscopy experiments were performed to demonstrate that the Percoll gradient method yielded significantly purified mitochondria by removing platelet membrane debris. Mitochondrial respiration following the substrate-uncoupler-inhibitor-titration (SUIT) protocol was similar in both the purified and crude mitochondrial extraction methods. Finally, the cytochrome c effect and JC-1 staining did not exhibit a significant difference between the two methods, suggesting that the mitochondrial integrity was not affected. Our study suggests that the Percoll discontinuous gradient purifies viable platelet-derived mitochondria by removing platelet-derived debris, including microparticles, therefore confirming that this isolation method is ideal for studying the downstream effects of intact mitochondria in mitochondrial-related diseases.

Biodistribution and organ oxidative damage following 28 days oral administration of nanosilver with/without coating in mice.

This study evaluated the biodistribution and organ oxidative effects of silver nanoparticles (AgNPs) coated with/without polyvinylpyrrolidone (PVP) (AgNP-20 and AgNP-PVP) in mice; these were administered by gavage at a dose of 10-250 mg/kg body weight per day for 28 days. The results showed that both the AgNPs could induce subacute toxicity and oxidative damage to mice and were mainly accumulated in the liver and spleen and excreted by feces. AgNPs could be absorbed into blood and might cross the blood-brain barrier, and be distributed extensively in mice. The malondialdehyde content in the liver, lungs and kidneys increased in both AgNP groups, while the content of glutathione decreased, and the activity of superoxide dismutase increased at first and then decreased along with the increased doses. Inflammatory pathological changes in the lung and liver at high dose of both AgNPs were consistent with increases in glutamate pyruvic transaminase, glutamate oxaloacetic transaminase and the total protein in serum detection. The Ag content was detected in organs, with the highest content in the liver, followed by spleen, while the Ag content in feces was about 500 times higher than that in urine. AgNP-PVP could induce higher oxidative stress and subacute toxicity than AgNP-20 at the same dose, which might be related to the higher concentrations and more Ag+ ions released in mice after AgNP-PVP exposure. The data from this research provided information on toxicity and biodistribution of AgNPs following gavage administration in mice, and might shed light for future application of AgNPs in daily life.

A Combined Utilization of Plasdone-S630 and HPMCAS-HF in Ziprasidone Hydrochloride Solid Dispersion by Hot-Melt Extrusion to Enhance the Oral Bioavailability and No Food Effect.

The purpose of this study was to research a novel combination of Plasdone-S630 and HPMCAS-HF as hot-melt carrier used in ziprasidone hydrochloride for enhanced oral bioavailability and dismissed food effect. Ziprasidone hydrochloride solid dispersion (ZH-SD) was prepared by hot-melt extrusion technique, and its optimized formulation was selected by the central composite design (CCD), which was characterized for powder X-ray diffraction (PXRD), fourier transform infrared spectroscopy (FTIR), in vitro dissolution study, and stability study. Finally, the in vivo study in fasted/fed state was carried out in beagle dogs. Based on PXRD analysis, HME technique successfully dispersed ziprasidone with a low crystallinity hydrochloride form in the polymers. According to the analysis of FTIR, hydrogen bonds were formed between drug and polymers during the process of HME. Without any noticeable bulk, crystalline could be found from the micrograph of ZH-SD when analyzed the result of scanning electron microscope (SEM). Pharmacokinetics studies indicated that the bioavailability of ZH-SD formulation had no significant difference in fasted and fed state, and the Cmax and AUC of ZH-SD were two fold higher than Zeldox® in fasted state. This result indicated that ziprasidone has achieved a desired oral bioavailability in fasted state and no food effect.

A novel application of electrospinning technique in sublingual membrane: characterization, permeation and in vivo study.

Isosorbide dinitrate-polyvinylpyrrolidone (ISDN-PVP) electrospinning fibers were formulated and explored as potentially sublingual membrane. The addition of polyethylene glycol (PEG) to the formulation improved flexibility and reduced fluffiness of the fiber mat. The scanning electron microscopy (SEM) demonstrated that the fibers tended to be cross-linking, and the crosslinking degree increased with the increase of PEG amount. The differential scanning calorimetry (DSC) indicated that ISDN existed in non-crystalline state in the fibers (except at the highest drug content). The infrared spectroscopy suggested that ISDN had better compatibility with the ingredients owing to the hydrogen bonding (or hydrophobic interactions). The fibers were highly favorable for the fabrication of sublingual membrane due to neutral pH, large folding endurance and rapid drug release (complete dissolution within 120 s). The permeation study of ISDN through both dialysis membrane (DM) and porcine sublingual mucosa (SM) were carried out. A significant relationship of drug permeation rate through DM and SM was built up, which indicated that DM could be used to partly simulate SM and assess formulation. The pharmacokinetic study in rats demonstrated that the electrospinning fiber membrane had a higher Cmax and lower Tmax compared to the reference preparation, and the relative bioavailability of the fiber membrane was 151.6%.

In Vitro Release and Bioavailability of Silybin from Micelle-Templated Porous Calcium Phosphate Microparticles.

Developing a promising carrier for the delivery of poorly water-soluble drugs, such as silybin, to improve oral absorption has become a very worthy of consideration. The goal of this study was to prepare a novel porous calcium phosphate microparticle using povidone-mixed micelles as template while evaluating its in vitro and in vivo properties with silybin as a model drug. The particle characterization, in vitro drug release behavior, and pharmacokinetic parameters of the prepared silybin-loaded calcium phosphate microparticle were investigated. The mean particle size was found to be 3.54 ± 0.32 µm with a rough surface porous structure. Additionally, the silybin-loaded calcium phosphate microparticle compared with the free silybin showed a prolonged 72-h release in vitro and a higher C max (418.5 ± 23.7 ng mL(-1)) with 167.5% oral relative bioavailability. A level A in vitro-in vivo correlation (IVIVC), established for the first time, demonstrated an excellent IVIVC of the formulated silybin in oral administration. In conclusion, this povidone-mixed micelle-based microparticle was successfully prepared to enhance the oral bioavailability of silybin. Therefore, application of this novel porous calcium phosphate microparticle holds a significant potential for the development of poorly water-soluble drugs.

Accumulation dynamics and acute toxicity of silver nanoparticles to Daphnia magna and Lumbriculus variegatus: implications for metal modeling approaches.

Frameworks commonly used in trace metal ecotoxicology (e.g., biotic ligand model (BLM) and tissue residue approach (TRA)) are based on the established link between uptake, accumulation and toxicity, but similar relationships remain unverified for metal-containing nanoparticles (NPs). The present study aimed to (i) characterize the bioaccumulation dynamics of PVP-, PEG-, and citrate-AgNPs, in comparison to dissolved Ag, in Daphnia magna and Lumbriculus variegatus; and (ii) investigate whether parameters of bioavailability and accumulation predict acute toxicity. In both species, uptake rate constants for AgNPs were ∼ 2-10 times less than for dissolved Ag and showed significant rank order concordance with acute toxicity. Ag elimination by L. variegatus fitted a 1-compartment loss model, whereas elimination in D. magna was biphasic. The latter showed consistency with studies that reported daphnids ingesting NPs, whereas L. variegatus biodynamic parameters indicated that uptake and efflux were primarily determined by the bioavailability of dissolved Ag released by the AgNPs. Thus, principles of BLM and TRA frameworks are confounded by the feeding behavior of D. magna where the ingestion of AgNPs perturbs the relationship between tissue concentrations and acute toxicity, but such approaches are applicable when accumulation and acute toxicity are linked to dissolved concentrations. The uptake rate constant, as a parameter of bioavailability inclusive of all available pathways, could be a successful predictor of acute toxicity.

Magnetic isolation of Plasmodium falciparum schizonts iRBCs to generate a high parasitaemia and synchronized in vitro culture.

BACKGROUND: The establishment of methods for an in vitro continuous culture of Plasmodium falciparum is essential for gaining knowledge into its biology and for the development of new treatments. Previously, several techniques have been used to synchronize, enrich and concentrate P. falciparum, although obtaining cultures with high parasitaemia continues being a challenging process. Current methods produce high parasitaemia levels of synchronized P. falciparum cultures by frequent changes of culture medium or reducing the haematocrit. However, these methods are time consuming and sometimes lead to the loss of synchrony. METHODS: A procedure that combines Percoll and sorbitol treatments, the use of magnetic columns, and the optimization of the in vitro culture conditions to reach high parasitaemia levels for synchronized Plasmodium falciparum cultures is described. RESULTS: A new procedure has been established using P. falciparum 3D7, combining previous reported methodologies to achieve in vitro parasite cultures that reach parasitaemia up to 40% at any intra-erythrocytic stage. High parasitaemia levels are obtained only one day after magnetic column purification without compromising the parasite viability and synchrony. CONCLUSIONS: The described procedure allows obtaining a large scale synchronized parasite culture at a high parasitaemia with less manipulations than other methods previously described.

Bioaccumulation, biodistribution, and transformation of polyvinylpyrrolidone-coated silver nanoparticles in edible seaweeds.

Seaweeds are recognised as a potential eco-friendly food source. However, some species have shown the capacity to bioaccumulate many substances of diverse nature, such as inorganic nanoparticles (NPs), which may have potentially harmful effects on them. Among these NPs, silver nanoparticles (AgNPs) have been used to enhance the antifungal and antibacterial properties of the final consumer products, such as textiles and food packages. Their potential release into the aquatic environment raises significant concern, increasing the probability of interaction with aquatic biota, such as macroalgae. In this work, we investigated the differences in bioaccumulation, biodistribution, and transformation of NPs as a function of seaweed species. We selected polyvinylpyrrolidone-coated silver nanoparticles (PVP-AgNPs) as model NP since they remain colloidally stable in seawater, focusing the study only on single particles and not on aggregates. The study was conducted on two different seaweed species with high commercial interest and value as human food: the red seaweed Palmaria palmata and the green seaweed Ulva fenestrata. Single-particle inductively coupled plasma mass spectroscopy (spICP-MS) analysis showed high and similar bioaccumulation of PVP-AgNPs in both seaweeds, in the range of 109 NPs/g of seaweed. However, electron microscopy with energy-dispersive X-ray analysis demonstrated that their time-dependent distribution and transformation in the algal tissue, mainly dissolution and formation of sulfur-rich corona and/or sulfidation, highly depended on the seaweed type. These results indicate that special attention should be given to the presence and transformation of AgNPs in seaweeds intended for human consumption. Not only the dissolution degree but also the speciation of these NPs could heavily impact their bioaccessibility, bioavailability, biodistribution, and toxicity to humans after ingestion.

Biotic and abiotic interactions in aquatic microcosms determine fate and toxicity of Ag nanoparticles. Part 1. Aggregation and dissolution.

To better understand their fate and toxicity in aquatic environments, we compared the aggregation and dissolution behavior of gum arabic (GA) and polyvinylpyrrolidone (PVP) coated Ag nanoparticles (NPs) in aquatic microcosms. There were four microcosm types: surface water; water and sediment; water and aquatic plants; or water, sediment, and aquatic plants. Dissolution and aggregation behavior of AgNPs were examined using ultracentrifugation, ultrafiltration, and asymmetrical flow field flow fractionation coupled to ultraviolet-visible spectroscopy, dynamic and static laser light scattering, and inductively coupled plasma mass spectrometry. Plants released dissolved organic matter (DOM) into the water column either through active or passive processes in response to Ag exposure. This organic matter fraction readily bound Ag ions. The plant-derived DOM had the effect of stabilizing PVP-AgNPs as primary particles, but caused GA-AgNPs to be removed from the water column, likely by dissolution and binding of released Ag ions on sediment and plant surfaces. The destabilization of the GA-AgNPs also corresponded with X-ray absorption near edge spectroscopy results which suggest that 22-28% of the particulate Ag was associated with thiols and 5-14% was present as oxides. The results highlight the potential complexities of nanomaterial behavior in response to biotic and abiotic modifications in ecosystems, and may help to explain differences in toxicity of Ag observed in realistic exposure media compared to simplified laboratory exposures.

Long-term transformation and fate of manufactured ag nanoparticles in a simulated large scale freshwater emergent wetland.

Transformations and long-term fate of engineered nanomaterials must be measured in realistic complex natural systems to accurately assess the risks that they may pose. Here, we determine the long-term behavior of poly(vinylpyrrolidone)-coated silver nanoparticles (AgNPs) in freshwater mesocosms simulating an emergent wetland environment. AgNPs were either applied to the water column or to the terrestrial soils. The distribution of silver among water, solids, and biota, and Ag speciation in soils and sediment was determined 18 months after dosing. Most (70 wt %) of the added Ag resided in the soils and sediments, and largely remained in the compartment in which they were dosed. However, some movement between soil and sediment was observed. Movement of AgNPs from terrestrial soils to sediments was more facile than from sediments to soils, suggesting that erosion and runoff is a potential pathway for AgNPs to enter waterways. The AgNPs in terrestrial soils were transformed to Ag(2)S (~52%), whereas AgNPs in the subaquatic sediment were present as Ag(2)S (55%) and Ag-sulfhydryl compounds (27%). Despite significant sulfidation of the AgNPs, a fraction of the added Ag resided in the terrestrial plant biomass (~3 wt % for the terrestrially dosed mesocosm), and relatively high body burdens of Ag (0.5-3.3 µg Ag/g wet weight) were found in mosquito fish and chironomids in both mesocosms. Thus, Ag from the NPs remained bioavailable even after partial sulfidation and when water column total Ag concentrations are low (<0.002 mg/L).

[Effect of different water-soluble forms of the fullerene C60 on the metabolic activity and ultra-structure of cells in culture].

In view of contradictory data on the toxicity of fullerenes for live organisms we studied the effect of water-soluble complexes of C60 with N-polyvivyl-pirrolidone (C60/PVP) and gamma-cyclodextrine (C60/gamma-CD) on MA-104 cells in culture. Both complexes proved to be non-toxic for cultured cells in the dark in wide range of concentrations. Both complexes provoke changes of cellular ultra-structure which reflect the enhancement of metabolic activity. At the same time only the exposition with the complex C60/PVP leads to the essential growth of number and size of mitochondria. However, the effect of two studied water-soluble forms of C60 under intensive UV-irradiation of cells proved to be opposite: C60/PVP had a cyto-protective action while C60/gamma-CD caused a significant growth of photo-toxicity. Possible reasons of the differences in the action of different forms of C60 on living organisms are discussed.

A comparison of spray drying and milling in the production of amorphous dispersions of sulfathiazole/polyvinylpyrrolidone and sulfadimidine/polyvinylpyrrolidone.

Formulations containing amorphous active pharmaceutical ingredients (APIs) present great potential to overcome problems of limited bioavailability of poorly soluble APIs. In this paper, we directly compare for the first time spray drying and milling as methods to produce amorphous dispersions for two binary systems (poorly soluble API)/excipient: sulfathiazole (STZ)/polyvinylpyrrolidone (PVP) and sulfadimidine (SDM)/PVP. The coprocessed mixtures were characterized by powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and intrinsic dissolution tests. PXRD and DSC confirmed that homogeneous glassy solutions (mixture with a single glass transition) of STZ/PVP were obtained for 0.05 ≤ X(PVP) (PVP weight fraction) < 1 by spray drying and for 0.6 ≤ X(PVP) < 1 by milling (at 400 rpm), and homogeneous glassy solutions of SDM/PVP were obtained for 0 < X(PVP) < 1 by spray drying and for 0.7 ≤ X(PVP) < 1 by milling. For these amorphous composites, the value of T(g) for a particular API/PVP ratio did not depend on the processing technique used. Variation of T(g) versus concentration of PVP was monotonic for all the systems and matched values predicted by the Gordon-Taylor equation indicating that there are no strong interactions between the drugs and PVP. The fact that amorphous SDM can be obtained on spray drying but not amorphous STZ could not be anticipated from the thermodynamic driving force of crystallization, but may be due to the lower molecular mobility of amorphous SDM compared to amorphous STZ. The solubility of the crystalline APIs in PVP was determined and the activities of the two APIs were fitted to the Flory-Huggins model. Comparable values of the Flory-Huggins interaction parameter (χ) were determined for the two systems (χ = -1.8 for SDM, χ = -1.5 for STZ) indicating that the two APIs have similar miscibility with PVP. Zones of stability and instability of the amorphous dispersions as a function of composition and temperature were obtained from the Flory-Huggins theory and the Gordon-Taylor equation and were found to be comparable for the two APIs. Intrinsic dissolution studies in aqueous media revealed that dissolution rates increased in the following order: physical mix of unprocessed materials < physical mix of processed material < coprocessed materials. This last result showed that production of amorphous dispersions by co-milling can significantly enhance the dissolution of poorly soluble drugs to a similar magnitude as co-spray dried systems.

Synthesis of polymer-protected graphene by solvent-assisted thermal reduction process.

Polyvinylpyrrolidone-protected (PVP-protected) graphene was synthesized by refluxing graphene oxide (GO) in dimethylformamide (DMF), using PVP as the dispersant. The structure and stability of this composite (DMF-rGO) were characterized using UV-vis spectroscopy, atomic force microscopy (AFM), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD) and thermogravimetric analysis (TGA). The results confirm the presence of a single sheet of DMF-rGO with PVP of 42%. This kind of chemically reduced GO has a greater solubility in water and also is more biocompatible than rGO reduced by hydrazine hydrate. This method is simple, environmentally friendly and the composite has potential applications in biology and polymer nanocomposites.

Fullerene-polyvinylpyrrolidone clathrate localizes in the cytoplasm to prevent Ultraviolet-A ray-induced DNA-fragmentation and activation of the transcriptional factor NF-kappaB.

By Western blot and immunostaining we proved that polyvinylpyrrolidone (PVP)-wrapped fullerene molecules (PVP-fullerene) could combine the 8- and 53-kb proteins which localize in the membrane of human skin keratinocytes HaCaT. Only fullerene molecules are able to cross the lipid membrane and conjugate 53-kb proteins in the cytosol. There are no fullerene molecules detectable in the nucleus or cytoskeleton. Ultraviolet-A (UVA)-irradiation on HaCaT or normal human epidermal melanocytes (NHEM) caused nuclear fragmentations, lowering of intracellular DNA-contents below diploidy, concurrently with the repressed DNA synthesis and the increased DNA-3'OH cleavage terminals, all of which were repressed by PVP-fullerene, as shown by flow cytometry and PI- or TUNEL-stain fluorography. Translocation of the transcriptional factor NF-kappaB in the cytoplasm to the nucleus of the keratinocytes was caused with UVA and repressed by PVP-fullerene with cytoprotective effects. Thus, the PVP-fullerene may be developed as a UV-protective agent with DNA-preservative effects owing to its combinative ability to molecules in the cytoplasm and cytomembrane, and then represses cellular oxidative stress and blocks abnormal signal pathways.

Reversal of experimental diabetes in mice by transplantation of neo-islets generated from human amnion-derived mesenchymal stromal cells using immuno-isolatory macrocapsules.

BACKGROUND AIMS: The ethical and biologic limitations with current sources of stem cells have resulted in a quest to look for alternative sources of multipotent stem cells of human origin. Amniotic membrane is of interest as a source of cells for regenerative medicine because of its ease of availability, plasticity and inexhaustible source that does not violate the sanctity of independent life. Although researchers have shown the stem cell-like potential of human amniotic epithelial cells, the mesenchymal part of amnion has remained less explored. METHODS: We established a long-term culture of mesenchymal-like stem cells derived from full-term human amniotic membrane and their differentiation into functional pancreatic lineage. RESULTS: The amnion-derived mesenchymal-like stem cells expressed various mesenchymal markers and demonstrated multilineage differentiation capacity. We also observed that these cells could form islet-like clusters (ILC) on exposure to serum-free defined media containing specific growth factor and differentiating agents. Differentiated ILC showed expression of human insulin, glucagon and somatostatin by immunocytochemistry, while quantitative reverse transcription/real-time-polymerase chain reaction (qRT-PCR) data demonstrated the expression of insulin, glucagon, somatostatin, Ngn3 and Isl1. Moreover, encapsulation of the ILC in polyurethane-polyvinyl pyrrolidone macrocapsules and their subsequent transplantation in experimental diabetic mice resulted in restoration of normoglycemia, indicating their ability to respond to high glucose without immunorejection. CONCLUSIONS: Our results demonstrate that amnion-derived mesenchymal stromal cells can undergo islet neogenesis, indicating amnion as an alternative source of islets for cell replacement therapy in diabetes.

Degradation and degradation-induced re-assembly of PVP-PCL micelles.

The nonenzymatic and enzymatic degradation behaviors of the poly(vinyl pyrrolidone)-poly(epsilon-caprolactone) (PVP-PCL) diblock copolymers micelles in aqueous solution were investigated by dynamic light scattering (DLS), size exclusion chromatography (SEC), and high performance liquid chromatography (HPLC), and the morphology variation of these micelles in the degradation procedure were inspected by transmission electronic microscopy (TEM). It is found that the enzymatic degradation of PVP-PCL micelles is much faster and the degradation rate of PVP-PCL micelles is proportional to the enzyme concentration for a given micelles' concentration. However, in the nonenzymatic case, the degradation of PVP-PCL micelles is quite slow under neutral condition and fast in acidic or basic medium. Interestingly, morphology transformation from spheres to a necklace and rod-like nanostructure was observed during the degradation procedure under basic condition. This shape reconstruction of PVP-PCL nanoparticles in the degradation process opens a new window to fabricate hierarchical supramolecular structures.

The interaction of PVP complexes of gossypol and its derivatives with an artificial membrane lipid matrix.

In this paper, we present the results of a study on the membrane-active properties of gossypol, its derivatives and their polyvinylpyrrolidone complexes as assessed by differential scanning calorimetry and by the fluorescent probe method. The latter revealed the change in polarization of the incident radiation caused by the action of the polyphenol on the artificial membrane lipid matrix.

Highly Sensitive Bacteria-Responsive Membranes Consisting of Core-Shell Polyurethane Polyvinylpyrrolidone Electrospun Nanofibers for In Situ Detection of Bacterial Infections.

Bacteria responsive color-changing wound dressings offer a valuable platform for continuous monitoring of the wound bed facilitating early detection of bacterial infections. In this study, we present a highly sensitive electrospun nanofibrous polyurethane wound dressing incorporating a hemicyanine-based chromogenic probe with a labile ester linkage that can be enzymatically cleaved by bacterial lipase released from clinically relevant strains, such as Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus (MRSA). A rapid chromogenic response was achieved by localizing the dye at the surface of core-shell fibers, resulting in a 5x faster response relative to conventional nanofibers. By incorporating polyvinylpyrrolidone (PVP) dopant in the shell, the sensitivity was boosted to enable detection of bacteria at clinically relevant concentrations after 2 h exposure: 2.5 × 105 CFU/cm2 P. aeruginosa and 1.0 × 106 CFU/cm2 MRSA. Introduction of PVP in the shell also boosted the degree of hydrolysis of the chromogenic probe by a factor of 1.2× after a 3 h exposure to a low concentration of P. aeruginosa (105 CFU/cm2). PVP was also found to improve the discernibility of the color change at high bacterial concentrations. The co-operativity between the chromogenic probe, fiber structure, and polymer composition is well-suited for timely in situ detection of wound infection.

Determination of total antioxidant capacity of Cynara Scolymus L. (globe artichoke) by using novel nanoparticle-based ferricyanide/Prussian blue assay.

A novel ferricyanide/Prussian blue (PB) assay for total antioxidant capacity (TAC) determination was developed exploiting the formation of PB nanoparticles in the presence of polyvinylpyrrolidone (PVP) as stabilizer. This improved method, named as "nanoparticle-based ferricyanide/Prussian blue assay (PBNP)", was applied to the TAC measurement of Cynara Scolymus L. (globe artichoke). The calibration results of the novel (PBNP) method were compared with those of a similar nanoparticle PB method performed in the absence of PVP, and of a sodium dodecyl sulfate-modified and acid-optimized ferricyanide reference assay. Compared to similar common Fe(III)-based TAC assays, much higher molar absorptivities, pointing out higher response to different kinds of antioxidants, were obtained with PBNP for all tested antioxidants, and lower LOD and LOQ values were achieved for thiols. As an additional advantage, methionine, not responding to other electron-transfer based TAC reagents, could be measured. PBNP could detect various antioxidants with one-two orders-of-magnitude lower LOD values than those of widely used TAC assays like CUPRAC and Folin-Ciocalteau well correlating with the proposed assay.