Identification of Ppy-lineage cells as a novel origin of pancreatic ductal adenocarcinoma.

The Ppy gene encodes pancreatic polypeptide (PP) secreted by PP- or γ-cells, which are a subtype of endocrine cells localised mainly in the islet periphery. For a detailed characterisation of PP cells, we aimed to establish PP cell lines. To this end, we generated a mouse model harbouring the SV40 large T antigen (TAg) in the Rosa26 locus, which is expressed upon Ppy-promoter-mediated Cre-loxP recombination. Whereas Insulin1-CreERT-mediated TAg expression in beta cells resulted in insulinoma, surprisingly, Ppy-Cre-mediated TAg expression resulted in the malignant transformation of Ppy-lineage cells. These mice showed distorted islet structural integrity at 5 days of age compared with normal islets. CK19+ duct-like lesions contiguous with the islets were observed at 2 weeks of age, and mice developed aggressive pancreatic ductal adenocarcinoma (PDAC) at 4 weeks of age, suggesting that PDAC can originate from the islet/endocrine pancreas. This was unexpected as PDAC is believed to originate from the exocrine pancreas. RNA-sequencing analysis of Ppy-lineage islet cells from 7-day-old TAg+ mice showed a downregulation and an upregulation of endocrine and exocrine genes, respectively, in addition to the upregulation of genes and pathways associated with PDAC. These results suggest that the expression of an oncogene in Ppy-lineage cells induces a switch from endocrine cell fate to PDAC. Our findings demonstrate that Ppy-lineage cells may be an origin of PDAC and may provide novel insights into the pathogenesis of pancreatic cancer, as well as possible therapeutic strategies. © 2024 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

One-Step Cooperative Growth of High Reaction Kinetics Composite Homogeneous Core-Shell Heterostructure.

Reaction kinetics can be improved by the enhanced electrical contact between different components growing symbiotically. But so far, due to the necessity for material synthesis conditions match, the component structures of cooperative growth are similar, and the materials are of the same type. The collaborative growth of high-reaction kinetics composite homogeneous core-shell heterostructure between various materials is innovatively proposed with different structures in one step. The NiCo-LDH and PPy successfully symbiotically grow on activated carbon fiber fabric in one step. The open channel structure of the NiCo-LDH nanosheets is preserved while PPy effectively wrapped around the NiCo-LDH. The well-defined nanostructure with abundant active sites and convenient ion diffusion paths is favorable for electrolyte entry into the entire nanoarrays. In addition, owing to the enhanced electronic interaction between different components through XPS analysis, the NiCo-LDH@PPy electrode shows outstanding reaction kinetics and structural stability. The as-synthesized NiCo-LDH@PPy exhibited excellent super-capacitive storage capabilities, robust capacitive activity, and good rate survival. Furthermore, an asymmetric supercapacitor (ASC) device made of NiCo-LDH@PPy and activated carbon (AC) is able to maintain a long cycle life while achieving high power and energy densities.

The role of Gel-Ppy-modified nerve conduit on the repair of sciatic nerve defect in rat model.

The serious clinical challenge of peripheral nerve injury (PNI) is nerve regeneration. Nerve conduit represents a promising strategy to contribute to nerve regeneration by bridging injured nerve gaps. However, due to a unique microenvironment of nerve tissue, autologous nerves have not been substituted by nerve conduit. Nerve regeneration after nerve conduit implantation depends on many factors, such as conductivity and biocompatibility. Therefore, Gelatin (Gel) with biocompatibility and polypyrrole (Ppy) with conductivity is highly concerned. In this paper, Gel-Ppy modified nerve conduit was fabricated with great biocompatibility and conductivity to evaluate its properties of enhancing nerve regeneration in vivo and in vitro. The proliferation of Schwann cells on Gel-Ppy modified nerve conduit was remarkably increased. Consistent with in vitro results, the Gel-Ppy nerve conduit could contribute to the regeneration of Schwann cell in vivo. The axon diameters and myelin sheath thickness were also enhanced, resulting in the amelioration of muscle atrophy, nerve conduction, and motor function recovery. To explain this interesting phenomenon, western blot results indicated that the Gel-Ppy conduit facilitated nerve regeneration via upregulating the Rap1 pathway to induce neurite outgrowth. Therefore, the above results demonstrated that Gel-Ppy modified nerve conduit could provide an acceptable microenvironment for nerve regeneration and be popularized as a novel therapeutic strategy of PNI.

A Solar Evaporator Based on Polypyrrole Coated 3D Carbon Nanotube Materials for Efficient Solar-Driven Vapor Generation.

Highly porous light absorbers are fabricated based on polypyrrole (PPy)-coated carbon nanotube (CNT). Carbon nanotube sponge (CNTS) or carbon nanotube array (CNTA) with three-dimensional (3D) network structure is the framework of porous light absorbers. Both PPy@CNTS and PPy@CNTA composites exhibit excellent light absorption of the full solar spectrum. The CNTS and CNTA with porous structures have extremely large effective surface area for light absorption and for water evaporation that has great practical benefit to the solar-driven vapor generation. The PPy layer on CNT sidewalls significantly improves the hydrophilicity of porous CNTS and CNTA. The good wettability of water on CNT sidewalls makes water transport in porous CNT materials highly efficient. The PPy@CNTS and PPy@CNTA light absorbers achieve high water evaporation rates of 3.35 and 3.41 kg m-2 h-1, respectively, under 1-sun radiation. The orientation of nano channels in CNTA-based light absorbers also plays an important role in the solar-driven vapor generation. The water transport and vapor escape are more efficient in CNTA-based light absorbers as compared to the CNTS-based light absorbers due to the relatively short path for the water transport and the vapor escape in CNTA-based light absorbers.

Antimicrobial and antibiofilm activity of highly soluble polypyrrole against methicillin-resistant Staphylococcus aureus.

AIMS: The purpose was to evaluate the antimicrobial activity of highly soluble polypyrrole (Hs-PPy), alone or combined with oxacillin, as well as its antibiofilm potential against methicillin-resistant Staphylococcus aureus strains. Furthermore, the in silico inhibitory mechanism in efflux pumps was also investigated. METHODS AND RESULTS: Ten clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) and two reference strains were used. Antimicrobial activity was determined by broth microdilution, and the combination effect with oxacillin was evaluated by the checkerboard assay. The biofilm formation capacity of MRSA and the interference of Hs-PPy were evaluated. The inhibitory action of Hs-PPy on the efflux pump was evaluated in silico through molecular docking. Hs-PPy showed activity against the isolates, with inhibitory action between 62.5 and 125 µg ml-1 and bactericidal action at 62.5 µg ml-1, as well as synergism in association with oxacillin. The isolates ranged from moderate to strong biofilm producers, and Hs-PPy interfered with the formation of this structure, but not with mature biofilm. There was no in silico interaction with the efflux protein EmrD, the closest homolog to NorA. CONCLUSIONS: Hs-PPy interferes with biofilm formation by MRSA, has synergistic potential, and is an efflux pump inhibitor.

Microarray evidence that 8-cell human embryos express some hormone family members including oxytocin.

OBJECTIVE: This study is to discover hormone pathways active in early cleaving human embryos. METHODS: A list of 152 hormones and receptors were compiled to query the microarray database of mRNAs in 8-cell human embryos, two lines of human embryonic stem cells plus human fibroblasts before and after induced pluripotency. RESULTS: Over half of the 152 hormones and receptors were silent on the arrays of all cell types, and more were detected at high or moderate levels on the 8-cell arrays than on the pluripotent cell or fibroblast arrays. Eight hormone family genes were uniquely detected at least 22-fold higher on the 8-cell arrays than the stem cell arrays: AVPI1, CCK, CORT, FSTL4, GIP, GPHA2, OXT, and PPY suggesting novel roles for these proteins in early development. Oxytocin was detected by pilot immunoassay in culture media collected from Day 3 embryos. Robust detection of CRHR1 and EPOR suggests the 8-cell embryo may be responsive to maternal CRH and EPO. The over-expression of POMC and GHITM suggests POMP peptide products may have undiscovered roles in early development and GHITM may contribute to mitochondrial remodeling. Under-detected on the 8-cell arrays at least tenfold were two key enzymes in steroid biosynthesis, DHCR24 and FDPS. CONCLUSIONS: The 8-cell human embryo may be secreting oxytocin, which could stimulate its own progress down the fallopian tube as well as play a role in early neural precursor development. The 8-cell embryo does not synthesize reproductive steroid hormones. As previously reported for growth factor families, the early embryo over-expresses more hormones than hormone receptors.

Ultra-sensitive electrochemical sensor based on in situ grown ultrafine HKUST-1 nanoparticles @ graphite nanosheets and core-shell structured MoO3-polypyrrole nanowires for the detection of rutin in orange juice.

Rutin extracted from natural plants has important medical value, so developing accurate and sensitive quantitative detection methods is one of the most important tasks. In this work, HKUST-1@GN/MoO3-Ppy NWs were utilized to develop a high-performance rutin electrochemical sensor in virtue of its high conductivity and electrocatalytic activity. The morphology, crystal structure, and chemical element composition of the fabricated sensor composites were characterized by SEM, TEM, XPS, and XRD. Electrochemical techniques including EIS, CV, and DPV were used to investigate the electrocatalytic properties of the prepared materials. The electrochemical test conditions were optimized to achieve efficient detection of rutin. The 2-electron 2-proton mechanism, consisting of several rapid and sequential phases, is postulated to occur during rutin oxidation. The results show that HKUST-1@GN/MoO3-Ppy NWs have the characteristics of large specific surface area, excellent conductivity, and outstanding electrocatalytic ability. There is a significant linear relationship between rutin concentration and the oxidation peak current of DPV. The linear range is 0.50-2000 nM, and the limit of detection is 0.27 nM (S/N = 3). In addition, the prepared electrode has been confirmed to be useful for rutin analysis in orange juice.

Dopamine Measurement Using Engineered CNT-CQD-Polymer Coatings on Pt Microelectrodes.

This study aims to develop a microelectrode array-based neural probe that can record dopamine activity with high stability and sensitivity. To mimic the high stability of the gold standard method (carbon fiber electrodes), the microfabricated platinum microelectrode is coated with carbon-based nanomaterials. Carboxyl-functionalized multi-walled carbon nanotubes (COOH-MWCNTs) and carbon quantum dots (CQDs) were selected for this purpose, while a conductive polymer like poly (3-4-ethylene dioxythiophene) (PEDOT) or polypyrrole (PPy) serves as a stable interface between the platinum of the electrode and the carbon-based nanomaterials through a co-electrodeposition process. Based on our comparison between different conducting polymers and the addition of CQD, the CNT-CQD-PPy modified microelectrode outperforms its counterparts: CNT-CQD-PEDOT, CNT-PPy, CNT-PEDOT, and bare Pt microelectrode. The CNT-CQD-PPy modified microelectrode has a higher conductivity, stability, and sensitivity while achieving a remarkable limit of detection (LOD) of 35.20 ± 0.77 nM. Using fast-scan cyclic voltammetry (FSCV), these modified electrodes successfully measured dopamine's redox peaks while exhibiting consistent and reliable responses over extensive use. This electrode modification not only paves the way for real-time, precise dopamine sensing using microfabricated electrodes but also offers a novel electrochemical sensor for in vivo studies of neural network dynamics and neurological disorders.

High energy density flexible Zn-ion hybrid supercapacitors with conductive cotton fabric constructed by rGO/CNT/PPy nanocomposite.

Fiber-shaped energy-storage devices for high energy and power density are crucial to power wearable electronics. In this work, reduced graphene oxide/carbon nanotubes/polypyrrole (GCP-op) cotton fabric with the optimal performance is prepared via a facile and cost-effective dipping-drying together with chemical polymerization approach. The structural characterizations confirm that the GCP-op cotton fabric has been successfully attached with numerous nanoparticles and carbon nanotubes, which can serve as a channel for electronical transfer. And GCP-op cotton fabric electrode displays admirable areal specific capacitance with 8397 mF cm-2at 1 mA cm-2. By combining GCP-op cathode with zinc anode, a GCP-op//PAM/ZnCl2//Zn flexible Zn-ion hybrid supercapacitor (FZHSC) is produced with 2 M polyacrylamide/ZnCl2(PAM/ZnCl2) hydrogel as the gel electrolyte. The FZHSC has superior cycle stability of 88.2%, outstanding energy density of up to 158µWh cm-2and power density at 0.5 mW cm-2. The remarkable performance proves that PPy-based material can provide more options for design and fabricate high energy flexible Zn-ion hybrid supercapacitors.

Bacteria-imprinted impedimetric sensor based on doping-induced nanostructured polypyrrole for determination of Escherichia coli.

A simple and label-free bacteria-imprinted impedimetric (BIP) sensor for the sensitive measurement of Escherichia coli has been developed. The BIP sensor is fabricated by one-step electropolymerization of pyrrole (functional monomer), copper phthalocyanine-3, 4', 4'', 4'''-tetrasulfonic acid tetrasodium salt (CuPcTs, dopant), and target bacteria (E. coli O157:H7) on a glassy carbon electrode. After the removal of the bacterial template, the established imprinted sites on the CuPcTs-doped polypyrrole film (PPy/CuPcTs) enable the highly selective rebinding of target bacteria and the resulting impedance change of the sensing interface is used to detect the target bacteria. We found that during the electropolymerization process, CuPcTs induced pyrrole to form granular-like nanostructured PPy/CuPcTs with excellent conductivity compared with the PPy film, substantially improving the sensitivity of the proposed sensor. The sensor presented a wide detection range (102 ~ 107 CFU⋅mL-1, RSD 1.1% ~ 3.5%) with a limit of detection of 21 CFU⋅mL-1. Furthermore, the proposed sensor effectively distinguished E. coli O157:H7 from other non-target bacteria and exhibited good practicality with recoveries from 91 to 103% in spiked real samples, indicating the potential utility of the sensor in food safety and environmental monitoring.

PPy coated nanoflower like CuCo2O4based onin situgrowth of nanoporous copper for high-performance supercapacitor electrodes.

General CuCo2O4electrodes suffer a very low reversible capacity and poor cycling stability because of easily fading phenomena and volume change during cycling. To optimize the electrode, a facile method is conducted to fabricate a novel electrode of Cu@CuCo2O4@polypyrrole nanoflowers. Due to larger specific surface area and more electrochemical reactive areas of CuCo2O4@polypyrrole nanoflowers, the pseudocapacitance of thein situgrown CuCo2O4@polypyrrole (912 F g-1at 2 A g-1) is much higher than the pristine CuCo2O4(618 F g-1at 2 A g-1). Remarkably, the CuCo2O4@polypyrrole (cathode) and active carbon (anode) are used to assemble an asymmetric supercapacitor, which exhibits a relatively high energy density of 90 Wh kg-1at a power density of 2519 W kg-1and 35 Wh kg-1at a high-power density of 9109 W kg-1, and excellent cycling stability (about 90.4% capacitance retention over 10 000 cycles). The prominent performance of CuCo2O4@polypyrrole makes it as a potential electrode for supercapacitor.

Molecularly imprinted polypyrrole based sensor for the detection of SARS-CoV-2 spike glycoprotein.

This study describes the application of a polypyrrole-based sensor for the determination of SARS-CoV-2-S spike glycoprotein. The SARS-CoV-2-S spike glycoprotein is a spike protein of the coronavirus SARS-CoV-2 that recently caused the worldwide spread of COVID-19 disease. This study is dedicated to the development of an electrochemical determination method based on the application of molecularly imprinted polymer technology. The electrochemical sensor was designed by molecular imprinting of polypyrrole (Ppy) with SARS-CoV-2-S spike glycoprotein (MIP-Ppy). The electrochemical sensors with MIP-Ppy and with polypyrrole without imprints (NIP-Ppy) layers were electrochemically deposited on a platinum electrode surface by a sequence of potential pulses. The performance of polymer layers was evaluated by pulsed amperometric detection. According to the obtained results, a sensor based on MIP-Ppy is more sensitive to the SARS-CoV-2-S spike glycoprotein than a sensor based on NIP-Ppy. Also, the results demonstrate that the MIP-Ppy layer is more selectively interacting with SARS-CoV-2-S glycoprotein than with bovine serum albumin. This proves that molecularly imprinted MIP-Ppy-based sensors can be applied for the detection of SARS-CoV-2 virus proteins.

Facile Synthesis of Fe3O4@Au/PPy-DOX Nanoplatform with Enhanced Glutathione Depletion and Controllable Drug Delivery for Enhanced Cancer Therapeutic Efficacy.

The complex physiological environment and inherent self-healing function of tumors make it difficult to eliminate malignant tumors by single therapy. In order to enhance the efficacy of antitumor therapy, it is significant and challenging to realize multi-mode combination therapy by utilizing/improving the adverse factors of the tumor microenvironment (TME). In this study, a novel Fe3O4@Au/PPy nanoplatform loaded with a chemotherapy drug (DOX) and responsive to TME, near-infrared (NIR) laser and magnetic field was designed for the combination enhancement of eliminating the tumor. The Fe2+ released at the low pH in TME can react with endogenous H2O2 to induce toxic hydroxyl radicals (·OH) for chemodynamic therapy (CDT). At the same time, the generated Fe3+ could deplete overexpressed glutathione (GSH) at the tumor site to prevent reactive oxygen species (ROS) from being restored while producing Fe2+ for CDT. The designed Fe3O4@Au/PPy nanoplatform had high photothermal (PT) conversion efficiency and photodynamic therapy (PDT) performance under NIR light excitation, which can promote CDT efficiency and produce more toxic ROS. To maximize the cancer-killing efficiency, the nanoplatform can be successfully loaded with the chemotherapeutic drug DOX, which can be efficiently released under NIR excitation and induction of slight acidity at the tumor site. In addition, the nanoplatform also possessed high saturation magnetization (20 emu/g), indicating a potential magnetic targeting function. In vivo and in vitro results identified that the Fe3O4@Au/PPy-DOX nanoplatform had good biocompatibility and magnetic-targeted synergetic CDT/PDT/PTT/chemotherapy antitumor effects, which were much better than those of the corresponding mono/bi/tri-therapies. This work provides a new approach for designing intelligent TME-mediated nanoplatforms for synergistically enhancing tumor therapy.

Characterisation of Ppy-lineage cells clarifies the functional heterogeneity of pancreatic beta cells in mice.

AIMS/HYPOTHESIS: Pancreatic polypeptide (PP) cells, which secrete PP (encoded by the Ppy gene), are a minor population of pancreatic endocrine cells. Although it has been reported that the loss of beta cell identity might be associated with beta-to-PP cell-fate conversion, at present, little is known regarding the characteristics of Ppy-lineage cells. METHODS: We used Ppy-Cre driver mice and a PP-specific monoclonal antibody to investigate the association between Ppy-lineage cells and beta cells. The molecular profiles of endocrine cells were investigated by single-cell transcriptome analysis and the glucose responsiveness of beta cells was assessed by Ca2+ imaging. Diabetic conditions were experimentally induced in mice by either streptozotocin or diphtheria toxin. RESULTS: Ppy-lineage cells were found to contribute to the four major types of endocrine cells, including beta cells. Ppy-lineage beta cells are a minor subpopulation, accounting for 12-15% of total beta cells, and are mostly (81.2%) localised at the islet periphery. Unbiased single-cell analysis with a Ppy-lineage tracer demonstrated that beta cells are composed of seven clusters, which are categorised into two groups (i.e. Ppy-lineage and non-Ppy-lineage beta cells). These subpopulations of beta cells demonstrated distinct characteristics regarding their functionality and gene expression profiles. Ppy-lineage beta cells had a reduced glucose-stimulated Ca2+ signalling response and were increased in number in experimental diabetes models. CONCLUSIONS/INTERPRETATION: Our results indicate that an unexpected degree of beta cell heterogeneity is defined by Ppy gene activation, providing valuable insight into the homeostatic regulation of pancreatic islets and future therapeutic strategies against diabetes. DATA AVAILABILITY: The single-cell RNA sequence (scRNA-seq) analysis datasets generated in this study have been deposited in the Gene Expression Omnibus (GEO) under the accession number GSE166164 ( www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE166164 ).

Flexible all-solid-state supercapacitors based on PPy/rGO nanocomposite on cotton fabric.

Polypyrrole (PPy) has high electrochemical activity and low cost, so it has great application prospects in wearable supercapacitors. Herein, we have successfully prepared polypyrrole/reduced graphene oxide (PPy/rGO) nanocomposite cotton fabric (NCF) by chemical polymerization, which exhibits splendid electrochemical performance compared with the individual. The addition of rGO can block the deformation of PPy caused by the expansion and contraction. The as-prepared PPy-0.5/rGO NCF electrode exhibits the brilliant specific capacitance (9300 mF cm-2at 1 mA cm-2) and the capacitance retention with 94.47% after 10 000 cycles. At the same time, the superior capacitance stability under different bending conditions and reuse capability have been achieved. All-solid-state supercapacitor has high energy density of 167µWh cm-2with a power density of 1.20 mW cm-2. Therefore, the PPy-0.5/rGO NCF electrode has a broad application prospect in high-performance flexible supercapacitor fabric electrode.

Flexible core/shelled PPy@PANI nanotube porous films for hybrid supercapacitors.

Flexibility of the films and the limited ion transport in the vertical direction of film highly restrict the development of flexible supercapacitors. Herein, we have developed hybrid porous films consisting of N-doped holey graphene nanosheets (NHGR) with abundant in-plane nanopores and the vertically aligned polyaniline nanowires arrays on polypyrrole nanotubes (PPy@PANI) via a two-step oxidative polymerization strategy and vacuum filtration. The rational design can efficiently shorten the diffusion path of electrons/ions, alleviate volume variation of electrodes during cycling, enhance electric conductivity of the hybrids, and while offer abundant active interfacial sites for electrochemical reaction. Benefiting from the distinctive structural and compositional merits, the obtained PPy@PANI/NHGR film electrode manifests an excellent electrochemical properties in terms of specific capacity (1348 mF cm-2at a current density of 1 mA cm-2), rate capability (81.2% capacitance retention from 1 to 30 mA cm-2), and cycling stability (capacitance retention of 73.7% at 20 mA cm-2after 7000 cycles). Matched with NHGR negative electrode, the assembled flexible all-solid-state asymmetric supercapacitor displays a remarkable areal capacitance of 359 mF cm-2at 5 mA cm-2, maximum areal energy density of 112.2µWh cm-2at 3.747 mW cm-2, and good flexibility at various bending angles while preserving stable cycling performance. The result shows the PPy@PANI/NHGR film with high flexibility and 3D ions transport channels is highly attractive for flexible energy storage devices.

Simultaneous Recognition of Dopamine and Uric Acid in the Presence of Ascorbic Acid via an Intercalated MXene/PPy Nanocomposite.

Two-dimensional (2D) MXenes have shown a great potential for chemical sensing due to their electric properties. In this work, a Ti3C2Tx/polypyrrole (MXene/PPy) nanocomposite has been synthesized and immobilized into a glassy carbon electrode to enable the simultaneous recognition of dopamine (DA) and uric acid (UA) under the interference of ascorbic acid (AA). The multilayer Ti3C2Tx MXene was prepared via the aqueous acid etching method and delaminated to a single layer nanosheet, benefiting the in-situ growth of PPy nanowires. The controllable preparation strategy and the compounding of PPy material remain great challenges for further practical application. A facile chemical oxidation method was proposed to regulate magnitude and density during the forming process of PPy nanowire, which promotes the conductivity and the electrochemical active site of this as-prepared nanomaterial. The MXene/PPy nanocomposite-modified electrode exhibited the selective determination of DA and UA in the presence of a high concentration of AA, as well as a wide linear range (DA: 12.5-125 µM, UA: 50-500 µM) and a low detection limit (DA: 0.37 µM, UA: 0.15 µM). More importantly, the simultaneous sensing for the co-existence of DA and UA was successfully achieved via the as-prepared sensor.

Evaluation of Electrochromic Properties of Polypyrrole/Poly(Methylene Blue) Layer Doped by Polysaccharides.

Polypyrrole (Ppy) and poly(methylene blue) (PMB) heterostructure (Ppy-PMB) was electrochemically formed on the indium tin oxide (ITO) coated glass slides, which served as working electrodes. For electropolymerization, a solution containing pyrrole, methylene blue, and a saccharide (lactose, sucrose, or heparin) that served as dopant was used. The aim of this study was to compare the effect of the saccharides (lactose, sucrose, and heparin) on the electrochromic properties of the Ppy-PMB layer. AFM and SEM have been used for the analysis of the surface dominant features of the Ppy-PMB layers. From these images, it was concluded that the saccharides used in this study have a moderate effect on the surface morphology. Electrochromic properties were analyzed with respect to the changes of absorbance of the layer at two wavelengths (668 nm and 750 nm) by changing the pH of the surrounding solution and the potential between +0.8 V and -0.8 V. It was demonstrated that the highest absorbance changes are characteristic for all layers in the acidic media. Meanwhile, the absorbance changes of the layers were decreased in the more alkaline media. It was determined that the Ppy-PMB layers with heparin as a dopant were more mechanically stable in comparison to the layers doped with lactose and sucrose. Therefore, the Ppy-PMB layer doped with heparin was selected for the further experiment and it was applied in the design of electrochromic sensors for the determination of three xanthine derivatives: caffeine, theobromine, and theophylline. A linear relationship of ΔA (∆A = A+0.8V - A-0.8V) vs. concentration was determined for all three xanthine derivatives studied. The largest change in optical absorption was observed in the case of theophylline determination.

In situ synthesis of polypyrrole on graphite felt as bio-anode to enhance the start-up performance of microbial fuel cells.

This study introduces an effective method to deposit polypyrrole (PPy) on graphite felt (GF) as anode to improve the start-up performance of microbial fuel cells (MFCs). The results of scanning electron microscope (SEM) and electrochemical testing reveal that polypyrrole is able to improve the electrical conductivity and surface roughness, which is beneficial to the microorganism attachment and growth. It shows that microorganisms grow faster on polypyrrole-modified anode than on unmodified anode. It takes ca. 5 days for polypyrrole-modified anode to reach a reproducible voltage platform, while it takes 11 days for unmodified anode. Moreover, the maximum power density of microbial fuel cells with polypyrrole-modified anode was 919 mW m-2, which were 2.3 times of that with unmodified anode. This research revealed that polypyrrole modification can improve the start-up performance of microbial fuel cells. It is considered as a feasible, economical and sustainable anode.

Demand for larger Y-STR reference databases in ethnic melting-pot countries: Argentina as a test case.

The Y chromosome behaves as a single locus. Its genetic information is useful in forensic casework, deficiency kinship testing, and population genetics studies. Continuous increases of loci number within commercial kits forced modification of worldwide reference databases. In Pan American countries, like Argentina, diverse parental ethnic groups contributed to the extant admixed urban populations. We report 509 additional haplotypes of 23 Y-STRs from donors inhabiting urban areas of six Argentinean provinces: Buenos Aires, Santiago del Estero, Santa Cruz, Rio Negro, Santa Fe, and Formosa. To better understand the demographic landscape of the admixed urban paternal lineages, structural analysis was performed using published data from other Argentinean provinces. AMOVA by Rst distance and inferred haplogroups by two predictive online software methods based on haplotypes yielded complementary results with respect to detected population structure, probably due to the different proportions of the Native American Q3-M3 haplogroup in the studied samples. This situation, which is common to most North, Meso, and South American countries, underscores the need for the additional step of typing specific SNPs for haplogroup diagnosis. We propose organizing Y-STR haplotype reference databases according to the most frequent haplogroups detected in a given admixed population.