Search

Made available in DSpace on 2018-11-26T17:44:31Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-03-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The need to improve the sensitivity, selectivity and stability of ozone gas sensors capable of monitoring the environment to prevent hazard to humans has sparked research on binary metal oxides. Here we report on a novel ozone gas sensor made with ca. 0.5 mu m yolk-shelled ZnCo2O4 microstructures synthesized via an eco-friendly, co-precipitation method and subsequent annealing. With these ZnCo2O4 microspheres, ozone concentrations down to 80 parts per billion (ppb) could be detected with a.c. and d.c. electrical measurements. The sensor worked within a wide range of ozone concentrations, from 80 to 890 ppb, being also selective to ozone compared to CO, NH3 and NO2. The high performance could be attributed to the large surface area to volume ratio inherent in yolk-shell structures. Indeed, ozone molecules adsorbed on the ZnCo2O4 surface create a layer of holes that affect the conductivity, as in a p-type semiconductor. Since this mechanism of detection is generic, ZnCo2O4 microspheres can be further used in other environment monitoring devices. (c) 2017 Elsevier B.V. All rights reserved. Univ Sao Paulo, Sao Carlos Inst Phys, CP 369, BR-13560970 Sao Carlos, SP, Brazil Univ Calif Berkeley, Dept Mech Engn, Berkeley, CA 94720 USA Univ Fed Sao Carlos, Dept Phys, Rodovia Washington Luis Km 235, BR-13565905 Sao Carlos, SP, Brazil Myongji Univ, Dept Energy Sci & Technol, Yongin, South Korea Sao Paulo State Univ, Inst Chem, Dept Phys Chem, POB 355, BR-14800900 Araraquara, SP, Brazil Sao Paulo State Univ, Inst Chem, Dept Phys Chem, POB 355, BR-14800900 Araraquara, SP, Brazil FAPESP: 2012/15543-7 FAPESP: 2013/14262-7 FAPESP: 2013/07296-2 FAPESP: 2014/23546-1 FAPESP: 2016/23474-6

We report on a facile strategy for separating carbon spherical shells (CSS) using centrifugation, with which shells were produced with diameter varying from 400 to 500 nm according to scanning and transmission electron microscopies. The shells were made of 79% carbon and 21% oxygen, and their surface was functionalized with carbonyl and hydroxyl groups. The CSS could form a homogeneous film on a glassy carbon (GC) electrode surface and be used in a sensing platform. In electroanalytical experiments, the sensitivity of the GC/CSS electrode for paracetamol increased with decreasing size of CSS. For 400 nm CSS, the sensitivity was 0.02 μA μmol–1 L, and the limit of detection and quantification in sweat, saliva, and urine samples was 120 and 400, 286 and 470, and 584 and 530 nmol L–1, respectively, which represents the highest performance among carbon-based sensors found in the literature. The GC/CSS electrodes were stable, robust against typical interferents, and allowed detection of paracetamol in sweat, sa...

In this study, we show the synthesis of novel hybrid organic-inorganic aerogel materials with one-dimensionally aligned pores and demonstrate their use as sustained and prolonged release systems for a hydrophobic drug. The materials are synthesized by trapping mesoporous silica nanoparticles within a hyperbranched polymer network made from poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA). The synthetic method involves dispersing mesoporous silica nanoparticles in a polymer solution, then freeze-drying the solution, and finally subjecting the resulting materials to high temperature to activate a solid-state condensation reaction between PVA and PAA. Before trapping the mesoporous silica nanoparticles within the hyperbranched polymeric network, their pores are decorated with hydrophobic groups so that they can serve as good host materials for hydrophobic drugs. The potential application of the hybrid aerogels as drug carriers is demonstrated using the hydrophobic, anti-inflammatory agent dexamethasone (DEX) as a model drug. Due to their hydrophobic pores, the hybrid aerogels show excellent drug loading capacity for DEX, with an encapsulation efficiency higher than 75%. Furthermore, the release pattern of the payloads of DEX encapsulated in the aerogels is highly tailorable (i.e., it can be made faster or slower, as needed) simply by varying the PVA-to-PAA weight ratio in the precursors, and thus the 3-dimensional (3-D) structures of the cross-linked polymers in them. The materials also show sustained drug release, for over 50 days or more. In addition, the aerogels are biocompatible, as demonstrated with Vero cells, and greatly promote the cell proliferation of L929 fibroblasts. Also, the nanoparticles functionalized with quaternary groups and dispersed within the aerogels display bactericidal activity against E. coli, S. aureus, B. subtilis, and P. aeruginosa. These new hybrid aerogels can, thus, be highly appealing biomaterials for sustained and prolonged drug release, such as wound dressing systems.

In this paper we present a portable photoelectrochemical system developed with screen-printed carbon electrodes (SPCEs) and a 3 W light-emitting diode (LED). The device with 3D printed structure was applied for detecting lactate on TiO2 nanoparticles modified with [Ni(salen)] polymer film (referred to as TiO2@poly[Ni(salen)]). Electrode coating with the polymer increased the sensitivity of the photoelectrochemical sensor, resulting in a linear range from 0.1 to 20 mmol L−1 with a limit of detection (LOD) of 88 μmol L−1. The sensing system exhibited excellent stability, reproducibility, and selectivity. We also demonstrated by in situ Fourier-transform infrared spectroscopy (FTIR) measurements that carbon dioxide (CO2) is the main product from photoelectrooxidation of lactate on TiO2@poly[Ni(salen)]. The portable system can be employed with any type of modified electrodes to function as photoelectroanalytical (bio)sensors, especially for point-of-care diagnostics.

Made available in DSpace on 2018-12-11T17:33:19Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-10-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The persistence of steroid hormones disposed of in the environment may pose risks to the health of humans and wildlife, which brings the need of understanding their mode of action, believed to occur in cell membranes. In this study, we investigate the molecular-level interactions between the synthetic hormone 17 α-ethynylestradiol (EE2) and Langmuir monolayers that represent simplified cell membranes. In surface pressure isotherms, EE2 was found to expand the monolayers at low surface pressures of the positively charged dimethyldioctadecylammonium bromide (DODAB), zwitterionic 1,2-dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC), negatively charged 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol (DPPG), and partially anionized stearic acid (StAc). The largest effects were observed for the charged DODAB and DPPG. At the pressure (30 mN.m−1) corresponding to the molecular packing of a cell membrane, EE2 caused the compressibility modulus to decrease, again with the largest changes occurring for DODAB and DPPG. The effects from EE2 on the packing of the lipid molecules at this high pressure depended essentially on the size of the headgroups, with EE2 contributing to the area per lipid for StAc and DODAB, whose headgroups are small. EE2 interacted with the headgroups of all lipids and StAc, also affecting the ordering of the tails for DODAB, DPPG and DPPC, according to in situ polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS). Based on the analysis with the two characterization methods, we propose a model for the EE2 positioning and molecular groups involved in the interaction, which should be relevant to unveil the endocrine disrupting action of EE2. São Paulo State University (UNESP) School of Technology and Applied Sciences São Carlos Institute of Physics − University of São Paulo, CP 369, 13560-970 São Carlos São Paulo State University (UNESP) School of Technology and Applied Sciences

The molecular-level interaction of levofloxacin with lung surfactant was investigated using Langmuir monolayers and atomistic molecular dynamics (MD) simulations. In the simulation, the DPPC/POPC mixed monolayer was used as a lung surfactant model and the molecules of levofloxacin were placed at the air-lipid interface to mimic the adsorption process on the lung surfactant model. The simulation results indicate that amphoteric levofloxacin expands the lung surfactant, also stabilizing the film for levofloxacin fractions until 10% w/w at least. The Langmuir monolayers made with the lung surfactant Curosurf had expanded isotherms upon incorporation of levofloxacin, without changes in monolayer elasticity. In fact, levofloxacin induced film stability with increased collapse pressures in the Curosurf isotherms and delayed the phase transition, according to Brewster angle microscopy (BAM) imaging. Using polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS), we found that levofloxacin is preferentially located in the head group region, inducing an increased organization of the Curosurf film. This location of levofloxacin was confirmed with MD simulations. The stability inferred demonstrates that the lung surfactant can be used as a drug delivery system for the administration via inhalation or intratracheal instillation of levofloxacin to treat lung diseases such as pneumonia and respiratory distress syndrome.

Electronic tongues (e-tongues) are promising analytical devices for a variety of applications to address the challenges of quality control in water monitoring and industries of foods, beverages, and pharmaceuticals. A crucial drawback in the current e-tongues is the need to recalibrate the device when one or more sensing units (usually with modified surface) are replaced. Another downside is the necessity to perform subsequent surface modifications and analyses to each of the diverse sensing units, undermining the simplicity and velocity of the method. These features have prevented widespread commercial use of the e-tongues. In this paper, we introduce a microfluidic e-tongue that overcomes all such limitations. The key principle of global selectivity of the e-tongue was achieved by recording only a single response, namely, the equivalent admittance spectrum of an association of resistors in parallel. Such resistors consisted of five nonfunctionalized stainless steel microwires (sensing units), which were short-circuited and coated with gold, platinum, nickel, iron, and aluminum oxide films. The microwires were inserted in a chip composed of a single piece of polydimethylsiloxane (PDMS). Using impedance spectroscopy, the e-tongue was successfully applied in classification of basic tastes at a concentration below the threshold for the human tongue. In addition, our chip allowed the distinction of various chemicals used in oil industry. Finally, our cleanroom-free prototyping allows the mass production of chips with easily replaceable and reproducible sensing units. Hence, one can now envisage the widespread dissemination of e-tongues with fast and reproducible data.

Mixed monolayers were prepared using phospholipids in order to mimic cell membranes and fractions of capsaicinoids (extracted from Malagueta, Caps-M, and Bhut Jolokia, Caps-B, peppers). According to their surface-pressure isotherms and polarization-modulated infrared reflection absorption spectra (PM-IRRAS), weak molecular-level interactions were observed between Caps and phospholipids. Both Caps-M and Caps-B penetrated into the alkyl tail region of the monolayer, interacted with the phosphate group of the phospholipids and affected hydration of their C O groups. Since the physiological activity of Caps is not governed solely by interaction with cell membranes, it should require participation of a neuronal membrane receptor, e.g. vanilloid receptor (TRPV1).

Point-of-care (PoC) diagnostics is promising for early detection of a number of diseases, including cancer, diabetes, and cardiovascular diseases, in addition to serving for monitoring health conditions. To be efficient and cost-effective, portable PoC devices are made with microfluidic technologies, with which laboratory analysis can be made with small-volume samples. Recent years have witnessed considerable progress in this area with &ldquo, epidermal electronics&rdquo, including miniaturized wearable diagnosis devices. These wearable devices allow for continuous real-time transmission of biological data to the Internet for further processing and transformation into clinical knowledge. Other approaches include bluetooth and WiFi technology for data transmission from portable (non-wearable) diagnosis devices to cellphones or computers, and then to the Internet for communication with centralized healthcare structures. There are, however, considerable challenges to be faced before PoC devices become routine in the clinical practice. For instance, the implementation of this technology requires integration of detection components with other fluid regulatory elements at the microscale, where fluid-flow properties become increasingly controlled by viscous forces rather than inertial forces. Another challenge is to develop new materials for environmentally friendly, cheap, and portable microfluidic devices. In this review paper, we first revisit the progress made in the last few years and discuss trends and strategies for the fabrication of microfluidic devices. Then, we discuss the challenges in lab-on-a-chip biosensing devices, including colorimetric sensors coupled to smartphones, plasmonic sensors, and electronic tongues. The latter ones use statistical and big data analysis for proper classification. The increasing use of big data and artificial intelligence methods is then commented upon in the context of wearable and handled biosensing platforms for the Internet of things and futuristic healthcare systems.

International audience; The ability to disperse metallic nano-objects in a given matrix material is an important issue for the design and fabrication of functional materials. A means to monitor the spatial distribution of the nano-dopants is highly desirable but often possible only a posteriori and with destructive techniques. Here we present a spectroscopic characterization based on different plasmonic responses of silver nanoparticles, their agglomerates, and finally the percolated silver film. We demonstrate its usefulness for the specific case of their dispersion in layer-by-layer polymeric films but the method is extendable to any other host material transparent in the visible/near UV range. Individual silver nanoparticles display the well-known localized surface plasmon resonance around 400 nm, which is red-shifted upon inter-particle coupling. The transition regime between weakly coupled particles and fully percolated metal films is, however, much harder to evidence unambiguously. We show here how to monitor this transition using the so-called Ferrell plasmon, a plasmonic mode of the thin film in the mid-UV, and excitable only under oblique irradiation but without specific coupling precautions. We can thus follow the entire transition from isolated to coupled and finally to fully agglomerated nanoparticles by optical spectroscopy.

Hypothesis The interaction of chitosan, a natural biopolymer with various biomedical applications, with lipid Langmuir films has been widely investigated as a simple model for cell membranes. However, to ensure polymer solubility, up to now only acidic subphases with pH significantly below biological fluids have been used. To increase the biological significance of these investigations, here we evaluated the effects of two chitosan derivatives (low molecular weight − CH, and positively charged − CH-P40) on phospholipid films (either zwitterionic DPPC or anionic DPPG) using phosphate buffered saline solutions (PBS) as a subphase. Experiments Surface pressure − area (π−A) isotherms were used to evaluate the expansion and changes in film elasticity, while Sum-Frequency Generation (SFG) vibrational spectroscopy provided information about the chain conformation of lipids. Findings It was found that chitosans caused a small expansion of the DPPC film by its insertion within the monolayer. In contrast, they distinctly expanded DPPG monolayers by both chitosan insertion within the lipid monolayer and by interacting with the anionic head group. Therefore, PBS buffer can be used as a subphase for more biologically relevant studies of chitosan interactions with Langmuir films, shedding light on why chitosan is antibacterial but not toxic to mammals, as the interaction mechanism depends on lipid headgroup charge.

Langmuir monolayers have been used as cell membrane models, where lipid composition is normally varied to mimic distinct types of membranes. For eukaryotic membranes, for instance, rather than using only zwitterionic phospholipids there is now a trend to employ mixtures to simulate the lipid rafts known to be relevant for various cellular processes. In this study, we demonstrate that effects from chitosans on Langmuir monolayers are considerably higher if lipid raft compositions (ternary mixtures of dipalmitoyl phosphatidyl choline (DPPC), sphingomyelin (SM) and cholesterol) are used. Significantly, measurable effects on the surface pressure isotherms start at 10-6 mg mL-1 for chitosans in lipid rafts, to be compared with 10-2 mg mL-1 for neat dipalmitoyl phosphatidylcholine (DPPC). This applies to both a commercial chitosan and chitosans soluble at physiological pH. Incorporation of these chitosans in the raft monolayers was confirmed in polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) experiments, where both the tail groups and headgroups were found to interact with chitosan. Since the effects on membrane models may be observed at such small concentrations for chitosans and probably other molecules, some studies may have to be revisited where neat phospholipids should be replaced by lipid raft compositions.

Understanding protein aggregation is essential to unveil molecular mechanisms associated with neurodegenerative diseases such as Alzheimer's, Huntington's and spongiform encephalopathy, particularly to determine the role of interaction with cell membranes. In this study, we employ Langmuir monolayers as cell membrane models to mimic interaction with the peptide KTNMHKHMAGAAAAGAVVGGLG-OH, a fragment from the human prion protein including residues 106-127, believed to be involved in protein aggregation. Using in situ polarization-modulated infrared reflection adsorption spectroscopy (PM-IRRAS) for Langmuir monolayers and FTIR for solid films, we found that PrP106-127 adopts mainly β-sheets, random coils and β-turns in Langmuir monolayers and in Langmuir-Blodgett (LB) and cast films. This also applies to monolayers and solid films made with PrP106-127 and a brain total lipid extract (BTLE). In contrast, some α-helices are observed in the secondary structure of PrP106-127 in monolayers, and especially in solid films, of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). In summary, in a model representing brain cells (BTLE), the secondary structure of PrP106-127 is typical of fiber aggregates, while aggregation is unlikely if PrP106-127 interacts with a membrane model (DOPC) characteristic of mammalian cells.

Blepharismins are photodynamic hypericin-like dianthrones produced as a variable pigment blend in Blepharisma ciliates and mostly studied in the Afro-Asiatic Blepharisma japonicum. The present work describes the bioactivity of pigments from the Brazilian Blepharisma sinuosum. Comparative analyses showed that the pigments from both species can trigger photo-induced modifications in phospholipids, but different redox properties and biological activities were assigned for each pigment blend. Stronger activities were detected for B. sinuosum pigments, with the lethal concentration LC50 10 × lower than B. japonicum pigments in light-irradiated tests against Bacillus cereus and less than half for treatments on the human HeLa tumor cells. HPLC showed B. sinuosum producing a simpler pigment blend, mostly with the blepharismin-C (~ 70%) and blepharismin-E (~ 30%) types. Each blepharismin engaged a specific dose-response profile on sensitive cells. The blepharismin-B and blepharismin-C were the most toxic pigments, showing LC50 ~ 2.5-3.0 µm and ~ 100 µm on B. cereus and HeLa cells, respectively, after illumination. Similarity clustering analysis compiling the bioactivity data revealed two groups of blepharismins: the most active, B and C, and the less active, A, D and E. The B. sinuosum pigment blend includes one representative of each clade. Functional and medical implications are discussed.

Made available in DSpace on 2020-12-10T19:54:18Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-04-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) National Institute for Science and Technology on Organic Electronics(INEO) Multiple Sclerosis (MS) is a chronic inflammatory disorder in the central nervous system for which biomarkers for diagnosis still remain unknown. One potential biomarker is the myelin basic protein. Here, a nanoimmunosensor based on atomic force spectroscopy (AFS) successfully detected autoantibodies against the MBP85-99 peptide from myelin basic protein. The nanoimmunosensor consisted of an atomic force microscope tip functionalization with MBP85-99 peptide, which was made to interact with a mica surface coated either with a layer of anti-MBP85-99 (positive control) or samples of cerebrospinal fluid (CSF) from five multiple sclerosis (MS) patients at different stages of the disease and five non-MS subjects. The adhesion forces obtained from AFS pointed to a high concentration of anti-MBP85-99 for the two patients at early stages of relapsing-remitting multiple sclerosis (RRMS), which were indistinguishable from the positive control. In contrast, considerably lower adhesion forces were measured for all the other eight subjects, including three MS patients with longer history of the disease and under treatment, without episodes of acute MS activity. We have also shown that the average adhesion force between MBP85-99 and anti-MBP85-99 is compatible with the value estimated using steered molecular dynamics. Though further tests will be required with a larger cohort of patients, the present results indicate that the nanoimmunosensor may be a simple tool to detect early-stage MS patients and be useful to understand the molecular mechanisms behind MS. Univ Fed Sao Carlos, Dept Phys Chem & Math, Nanoneurobiophys Res Grp, BR-18052780 Sorocaba, SP, Brazil Univ Sao Paulo, Inst Trop Med, BR-05403000 Sao Paulo, SP, Brazil Sao Paulo State Univ, Dept Neurol Psychol & Psychiat, BR-18618687 Botucatu, SP, Brazil Univ Sao Paulo, Sao Carlos Inst Phys, BR-13560970 Sao Carlos, SP, Brazil Univ Sao Paulo, Inst Chem, Dept Biochem, BR-05508000 Sao Paulo, SP, Brazil Rheabiotech Lab Res & Dev, BR-13084791 Campinas, SP, Brazil Pontifical Catholic Univ Sao Paulo, BR-18030010 Sorocaba, SP, Brazil Sao Paulo State Univ, Dept Neurol Psychol & Psychiat, BR-18618687 Botucatu, SP, Brazil FAPESP: 2013/14262-7 FAPESP: 2014/21530-0 FAPESP: 2015/14360-4 FAPESP: 2015/06847-0 FAPESP: 2015/36143-2 FAPESP: 2015/052836 FAPESP: 2014/12082-4 FAPESP: 2012/50839-4 FAPESP: 2014/50869-6 CNPq: 465572/2014-6 CNPq: 308658/2015-9 CNPq: 459768/2014-0 CAPES: 23038.000776/201754

Calixarenes are macrocyclic compounds containing a central cavity which can be easily synthesized through various chemical procedures. The presence of the cavity means that they can reversibly form host–guest compounds with inorganic gases and organic vapors. Calixarenes can be obtained in varied sizes and be easily chemically modified with functional groups. This makes them especially suitable as selective sensing molecules due to the ability to fine-tune their structure, cavity size, and functionality. They are highly stable and amenable to processing into thin films using several techniques. Their porous structure allows for rapid diffusion within the films, serving as receptors for binding of gaseous species. In this chapter, we will highlight the use of calixarenes in sensor devices with various principles of detection, including surface plasmon resonance (SPR), surface acoustic wave (SAW), quartz crystal microbalance (QCM), and fiber-optic-based interrogation methods. The combination of stable selective receptors with sensing platforms has enabled sensitive, selective, and reliable detection and monitoring of hazardous gases and vapors.

Rapid, on-site detection of emerging pollutants is critical for monitoring health threats and the environment, especially if performed through autonomous systems. In this paper, we report on a new design of a complete electrochemical system whose working (WE), auxiliary (AE) and reference (RE) electrodes were obtained on a pen (PEN Sensor) made with graphite:polyurethane (GPUE). Working electrodes were decorated with spherical, ca. 200 nm silver nanoparticles (AgNPs) reduced on graphite using the polyol method. Differential pulse voltammetry (DPV) was used to detect bisphenol-A (BPA) in a linear range from 2.5 to 15 μmol L−1 with detection limit of 0.24 μmol L−1. The PEN Sensor could also detect bisphenol-A in tap and river water samples, with satisfactory reproducibility and repeatability, while common interferents did not affect electrooxidation of bisphenol-A. The high sensitivity and rapid detection are suitable for real-time analysis and in loco monitoring of emerging pollutants. With their robustness and versatility, PEN Sensors such as those fabricated here may be integrated into futuristic smart robotic systems.

Multidimensional electrochemical and optical sensors hold great potential for screening analysis purposes due to their ability to provide discriminatory chemical analyses without specific receptors for each analyte of interest. Upon exploiting nanomaterials and microfluidic platforms, these sensors have reached high performance in terms of pattern recognition, sensitivity, low consumption of chemicals and samples, repeatability, and analysis time. In this chapter, we discuss recent progress in the design of electrochemical and optical multidimensional arrays and propose a systematic classification of these sensors. Significant issues addressed with the use of nanomaterials (e.g., graphene, nanoparticles, and nanodots) and examples of microfluidic platforms, along with a current outlook for the field, are also discussed.

Great efforts have been focused on the rapid development of gas sensors capable of operating at room temperature since the monitoring of air quality has become a major concern for people’s health and well-being. Nanoarchitectonics is a new concept for the fabrication of functional materials by harmonizing methods at the atomic/molecular level and using mostly bottom-up techniques. In this field, carbon allotropes have been intensively explored, more specifically graphene derivatives due to their outstanding mechanical, electrical, and thermal properties. In the drive toward nanoarchitectonics, researchers have designed nanoarchitectures and nanocomposites of graphene derivatives and conductive polymers, utilizing synergistic effects to enhance the conductivity and thereby improve the performance of sensors for gas detection. Within this chapter, we review recent advances on gas sensors based on graphene/polymer composites and their applications toward the monitoring of hazardous gases.

In this paper, we introduce simple procedures not only to enhance the polarized photoluminescence (PL) of poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO) films but also to vary the relative concentrat...

There has been growing interest in using strong field enhancement and light localization in plasmonic nanostructures to control the polarization properties of light. Various experimental techniques are now used to fabricate twisted metallic nanoparticles and metasurfaces, where strongly enhanced chiral near-fields are used to intensify circular dichroism (CD) signals. In this review, state-of-the-art strategies to develop such chiral plasmonic nanoparticles and metasurfaces are summarized, with emphasis on the most recent trends for the design and development of functionalizable surfaces. The major objective is to perform enantiomer selection which is relevant in pharmaceutical applications and for biosensing. Enhanced sensing capabilities are key for the design and manufacture of lab-on-a-chip devices, commonly named point-of-care biosensing devices, which are promising for next-generation healthcare systems.

We demonstrate a giant enhancement of the transverse magneto-optical Kerr effect. In contrast to conventional magnetoplasmonic structures, we exploit surface plasmon resonances (SPRs) excited along the surface of a ferromagnetic substrate on which a uniaxial $\ensuremath{\varepsilon}$-near-zero (ENZ) metamaterial is grown. In this design, bulky prism couplers are not required and SPR sensors can be produced in integrated, miniaturized systems. We also obtained the analytical expression for the ENZ-SPR phase-matching condition, which can be used for the straightforward design of plasmonic and magnetoplasmonic devices.

DNA methylation is involved in the oncogenesis of head and neck squamous cell carcinoma and could be used for early detection of cancer to increase the chances of cure, but unfortunately diagnosis is usually made at late stages of the disease. In this work we developed genosensors to detect DNA methylation of the MGMT gene in head and neck cancer cell lines. The probe for MGMT promoter methylation was immobilized on gold electrodes modified with 11-mercaptoundecanoic acid (11-MUA) self-assembled monolayers (SAM). Detection was performed with electrochemical impedance spectroscopy, with clear distinction between methylated and non-methylated DNA from head and neck cell lines. The genosensor is sensitive with a low detection limit of 0.24 × 10−12 mol L−1. In addition, the cell lines FaDu, JHU28 and SCC25 for the MGMT gene, could be distinguished from the HN13 cell line which has a high degree of MGMT methylation (97%), thus confirming the selectivity. Samples with different percentages of MGMT DNA methylation could be separated in multidimensional projections using the visualization technique interactive document mapping (IDMAP). The genosensor matrix and the immobilization procedures are generic, and can be extended to other DNA methylation biomarkers.

A disposable electrochemical immunosensors is presented suitable to detect cancer biomarker p53 using screen-printed carbon electrodes modified with a layer-by-layer (LbL) matrix of carboxylated NiFe2O4 nanoparticles and polyethyleneimine, onto which anti-p53 antibodies were adsorbed. Under optimized conditions, the immunosensors exhibited high surface coverage and high concentration of immobilized antibodies, which allowed for detection of p53 in a wide dynamic range from 1.0 to 10 × 103 pg mL−1, with a limit of detection of 5.0 fg mL−1 at a working potential of 100 mV vs. Ag/AgCl. The immunosensors also exhibited good selectivity with negligible interference upon incubation in complex matrices containing high concentrations of proteins (i.e., fetal bovine serum and cell lysate). The immunosensor performance is among the best reported in the literature for determination of p53, with the additional advantage of being disposable and operating with low-volume solutions. Graphical abstract

This paper reports on biosensors made with a matrix of polylactic acid (PLA) fibers, which are suitable for immobilization of the anti-p53 active layer for detection of p53 biomarker. The PLA fibers were produced with solution blow spinning, a method that is advantageous for its simplicity and possibility to tune the fiber properties. For the biosensors, the optimized time to deposit the fibers was 60 s, with which detection of p53 could be achieved with the limit of detection of 11 pg/mL using electrical impedance spectroscopy. This sensitivity is also sufficient to detect the p53 biomarker in patient samples, which was confirmed by distinguishing samples from cell lines with distinct p53 concentrations in a plot where the impedance spectra were visualized with the interactive document mapping (IDMAP) technique. The high sensitivity and selectivity of the biosensors may be attributed to the specific interaction between the active layer and p53 modeled with a Langmuir-Freundlich and Freundlich isotherms and inferred from the analysis of the vibrational bands at 1550, 1650 and 1757 cm−1 using polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS). The successful immobilization of the active layer is evidence that the approach based on solution blown spun fibers may be replicated to other types of biosensors., The authors are grateful to Brazilian National Council for Scientific and Technological Development (CNPq) (Grant #150985/2017-7, #113757/2018-2, #402287/2013-4 and 303796/2014-6), São Paulo Research Foundation (FAPESP) (Grant #2013/14262-7, #2017/18725-2 and #2018/18953-8), CAPES (001), INEO, and Barretos Cancer Hospital. The authors are also thanks to Maria Helena Piazzetta and Angelo Gobbi (LMF/LNNANO/CNPEM, Brazil) for their assistance in electrode fabrication.

The molecular control in Langmuir-Blodgett (LB) films may be exploited in charge storage electrodes provided a suitable choice of molecular architecture and components is made. In this paper, we employed a naphtyl-1,3,4-oxadiazole amphiphile (NFT1) and its complex [Ru(bpy)2NFT1]PF6 (RuNFT1) (bpy = 2,2’-bipyridine) in heterostructured LB films in a proof-of-principle production of charge storage. The optimized architecture contained a one-layer RuNFT1 deposited on a 9-layer NFT1 LB film, where the efficient packing of NFT1 inferred from spectroscopic measurements and Brewster angle microscopy (BAM) images was considered as relevant for ion diffusion. This packing was achieved owing to the π-stacking warranted by the planarity of the NFT1 naphtyl 1,3,4-oxadiazole ring, as confirmed with density functional theory (DFT) calculations. The top layer of the redox-active RuNFT1 provided an additional contribution with its Faradaic charge storage to the double layer capacitance of NFT1. Taken together, these results demonstrate that synergy may be achieved in combining distinct compounds in LB films toward efficient charge storage.

Made available in DSpace on 2020-12-12T01:08:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-12-24 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The alarming increase in bacterial resistance to antibiotics has demanded new strategies for microbial inactivation, which include photodynamic therapy whose activity relies on the photoreaction damage to the microorganism membrane. Herein, the binding mechanisms of the photosensitizer toluidine blue-O (TBO) on simplified models of bacterial membrane with Langmuir monolayers of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) and 1,2-dioleoyl-sn-glycero-3-phospho-(1′-rac-glycerol) (DOPG) were correlated to the effects of the photoinduced lipid oxidation. Langmuir monolayers of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) were also used as a reference of mammalian membranes. The surface pressure isotherms combined with polarization-modulated infrared reflection absorption spectroscopy revealed that TBO expands DOPC, DOPE, and DOPG monolayers owing to electrostatic interactions with the negatively charged groups in the phospholipids, with a stronger adsorption on DOPG, which has a net surface charge. Light irradiation made the TBO-containing DOPC and DOPE monolayers less unstable as a result of the singlet oxygen (1O2) reaction with the chain unsaturation and hydroperoxide formation. In contrast, the decreased stability of the irradiated TBO-containing DOPG monolayer suggests the cleavage of carbon chains. The anionic nature of DOPG allowed a deeper penetration of TBO into the chain region, favoring contact-dependent reactions between the excited triplet state of TBO and lipid unsaturations or/and hydroperoxide groups, which is the key for the cleavage reactions and further membrane permeabilization. São Paulo State University (UNESP) School of Sciences Humanities and Languages IFSC São Carlos Institute of Physics University of São Paulo (USP) São Paulo State University (UNESP) School of Sciences Humanities and Languages

Diagnosis of prostate cancer via PCA3 biomarker detection is promising to be much more efficient than with the prostatic specific antigens currently used. In this study, we present the first electrochemical and impedance-based biosensors that are capable of detecting PCA3 down to 0.128 nmol/L. The biosensors were made with a layer of PCA3-complementary single-stranded DNA (ssDNA) probe, immobilized on a layer-by-layer (LbL) film of chitosan (CHT) and carbon nanotubes (MWCNT). They are highly selective to PCA3, which was confirmed in impedance measurements and with polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS). Using information visualization methods, we could also distinguish between cell lines expressing the endogenous PCA3 long noncoding RNA (lncRNA) from cells that did not contain detectable levels of this biomarker. Since the methods involved in fabrication the biosensors are potentially low cost, one may hope to deploy PCA3 tests in any laboratory of clinical analyses and even for point-of-care diagnostics., This work had financial support from CNPq (Grant #164356/2015-0 and #113757/2018-2), FAPESP (Grant #2013/14262-7) and Barretos Cancer Hospital (Brazil). Andrey Soares thanks to Grant #2018/18953-8, São Paulo Research Foundation (FAPESP). The authors are also thankful to Maria Helena de Oliveira Piazzetta and Angelo Luiz Gobbi for the use of the Microfabrication Laboratory (LMF/LNNano/CNPEM) to manufacture interdigitated electrodes.

Natural products such as epigallocatechin-3-gallate (EGCG) have been suggested for complementary treatments of cancer, since they lower toxic side effects of anticancer drugs, and possess anti-inflammatory and antioxidant properties that inhibit carcinogenesis. Their effects on cancer cells depend on interactions with the membrane, which is the motivation to investigate Langmuir monolayers as simplified membrane models. In this study, EGCG was incorporated in zwitterionic dipalmitoyl phosphatidyl choline (DPPC) and anionic dipalmitoyl phosphatidyl serine (DPPS) Langmuir monolayers to simulate healthy and cancer cells membranes, respectively. EGCG induces condensation in surface pressure isotherms for both DPPC and DPPS monolayers, interacting mainly via electrostatic forces and hydrogen bonding with the choline and phosphate groups of the phospholipids, according to data from polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS). Both monolayers become more compressible upon interaction with EGCG, which may be correlated to the synergy between EGCG and anticancer drugs reported in the literature. The interaction with EGCG is stronger for DPPC, leading to stronger morphological changes in Brewster angle microscopy (BAM) images and higher degree of condensation in the surface pressure isotherms. The changes induced by blue irradiation on DPPC and DPPS monolayers were largely precluded when EGCG was incorporated, thus confirming its antioxidant capacity for both types of membrane.

Made available in DSpace on 2019-10-06T17:13:01Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-09-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Cell membrane models are useful to obtain molecular-level information on the interaction of biologically-relevant molecules such as pesticides whose activity is believed to depend on its effects on the membrane. In this study, we investigated the interaction between the widely used pesticide picloram with Langmuir monolayers of binary and ternary mixtures comprising 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), sphingomyelin (SM) and cholesterol (Chol), which could be taken as representative of ocular membranes in humans. Picloram expanded the molecular area of DOPC/SM and DOPC/SM/Chol monolayers as the pesticide penetrated the hydrophobic region of the mixtures. A clear correlation was also found between the compressibility modulus (Cs−1) and the presence of cholesterol in the ternary monolayer. Data from polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) confirmed that picloram interacts with both the acyl chains and headgroups. Spectral shifts and band broadening were induced by picloram, particularly for the phosphate and choline groups, probably owing to its H-bonding ability. The effects reported here on the lipid monolayers may be evidence of the possible activity of picloram on mammalian cell membranes, which highlights the importance of strict control of the level of exposure of humans dealing with pesticides. Faculdade de Ciências e Tecnologia (FCT)-Universidade Estadual Paulista (UNESP)-Presidente Prudente São Carlos Institute of Physics University of Sao Paulo, CP 369 Faculdade de Ciências e Tecnologia (FCT)-Universidade Estadual Paulista (UNESP)-Presidente Prudente FAPESP: 2013/14262-7 FAPESP: 2016/06424-5

Catechins are molecules with potential use in different pathologies such as diabetes and cancer, but their pharmaceutical applications are often hindered by their instability in the bloodstream. This issue can be circumvented using liposomes as their nanocarriers for in vivo delivery. In this work, we studied the molecular details of (-)-epigallocatechin-3-gallate (EGCG) interacting with 1,2-dimyristoyl- sn-glycero-3-phosphocholine (DMPC) monolayer/bilayer systems to understand the catechin loading ability and liposome stability, using experimental and computational techniques. The molecular dynamics simulations show the EGCG molecules deep inside the lipid bilayer, positioned below the lipid ester groups, generating a concentration-dependent lipid condensation. This effect was also inferred from the surface pressure isotherms of DMPC monolayers. In the polarization-modulated infrared reflection absorption spectra assays, the predominant effect at higher concentrations of EGCG (e.g., 20 mol %) was an increase in lipid tail disorder. The steady-state fluorescence data confirmed this disordered state, indicating that the catechin-induced liposome aggregation outweighs the condensation effects. Therefore, by adding more than 10 mol % EGCG to the liposomes, a destabilization of the vesicles occurs with the ensuing release of entrapped catechins. The loading capacity for DMPC seems to be limited by its disordered lipid arrangements, typical of a fluid phase. To further increase the clinical usefulness of liposomes, lipid bilayers with more stable and organized assemblies should be employed to avoid aggregation at large concentrations of catechin.

Introduction: The living standards of the human race in the past few decades have grown at a remarkable pace. One of the most critical environmental issues is the monitoring of air quality [1]. Nitrogen dioxide (NO2) is a hazardous gas and has multiple sources like vehicular emission, combustion process, and unvented heaters present in our day-to-day life. Overexposure to this gas becomes a reason for respiratory problems in humans as well as animals. Hence, it is very crucial to detect this toxic analyte selectively at low temperatures. Various metal oxides have been explored to detect NO2 gas; however, selectivity and operation temperature are still challenging [2]. Microsensors using nanostructured oxides/binary oxides are the most suitable to minimize the current problems of gas sensors (lack of sensitivity, selectivity, and stability) since the reduction in dimensions implies a greater contribution of the surface (greater sensitivity) as well as modification of the transport mechanisms (faster processes) [3-4]. This work demonstrates the low temperature, highly sensitive NO2 detection with fast recovery speed based on hierarchical Cobalt Stannate (Co2SnO4) microspheres synthesized by a facile co-precipitation route. Methodology: Hierarchical Cobalt Stannate (Co2SnO4) microspheres were synthesized with the co-precipitation method with a different annealing process. The sensor film was deposited on microsensors features an interdigitated electrode which encircled platinum heater to regulate the operating temperature and ensure its uniformity. The samples' structural and surface properties were characterized using X-ray diffraction (XRD), scanning electron microscopy (FESEM), and BET Surface area, especially to verify the nanomorphology and high surface area. Chemiresistive sensing behavior was recorded. The sensor response was calculated using the equation: Sensor Response (%) = (Ra-Rg)/Ra *100, where Ra and Rg are resistance in air and with the sensing gas, respectively. Results and Conclusions: Compared with the traditional metal oxide-based gas sensors, which operates at high temperature (>300 °C), specific accomplishments include (1) synthesis of Co2SnO4 microspheres with the larger surface area for higher sensing response towards NO2 gas; (2) chemiresistive gas responses of the Co2SnO4 sensor down to 1 ppm for NO2 at a low temperature of 90 °C with high sensitivity and long-term stability; (3) the morphology of microspheres for fast adsorption-desorption processes; and (4) the sensor shows the excellent reproducibility and reversibility with less power consumption (5) Co2SnO4 film exhibits a maximum sensor response of ~81 at 90°C towards NO2 with fast response (~ 24 s) and recovery time (~756 s) at one ppm. (6) the resulting sensor exhibits selectivity toward nitrogen dioxide compared to other gases such as CO2, CO, and H2. References: [1] Kevin W. Bowman, Toward the next generation of air quality monitoring: Ozone, Atmospheric Environment 80 (2013) 571-583. doi: 10.1016/j.atmosenv.2013.07.007 [2] Yichuan Wu, Nirav Joshi, Shilong Zhao, Hu Long, Liujiang Zhou, Ge Ma, Bei Peng, Osvaldo N Oliveira Jr., Alex Zettl, and Liwei Lin, NO2 gas sensors based on CVD tungsten diselenide monolayer, Applied Surface Science 529 (2020) 147110. doi: 10.1016/j.apsusc.2020.147110 [3] Sabu Thomas, Nirav Joshi, Vijay K. Tomer, Functional Nanomaterials: Advances in Gas Sensing Technologies. 2020: Springer Nature Singapore Pte Ltd. doi: 10.1007/978-981-15-4810-9 [4] Nirav Joshi, Luís F. da Silva, Harsharaj S. Jadhav, Flavio M. Shimizu, Pedro H. Suman, Jean-Claude M'Peko, Marcelo Ornaghi Orlandi, Valmor R. Mastelaro, Osvaldo N. Oliveira Jr, Yolk-shelled ZnCo2O4 microspheres: Surface properties and gas sensing application, Sensors and Actuators B 257 (2018) 906–915. doi: 10.1016/j.snb.2017.11.041.

Peptides with an active redox molecule are incorporated into nanostructured films for electrochemical biosensors with stable and controllable physicochemical properties. In this study, we synthesized three ferrocene (Fc)-containing peptides with the sequence Fc-Glu-(Ala)n-Cys-NH2, which could form self-assembled monolayers on gold and be attached to antibodies. The peptide with two alanines (n = 2) yielded the immunosensor with the highest performance in detecting C-reactive protein (CRP), a biomarker of inflammation. Using electrochemical impedance-derived capacitive spectroscopy, the limit of detection was 240 pM with a dynamic range that included clinically relevant CRP concentrations. With a combination of electrochemical methods and polarization-modulated infrared reflection–absorption spectroscopy, we identified the chemical groups involved in the antibody-CRP interaction, and were able to relate the highest performance for the peptide with n = 2 to chain length and efficient packing in the organized films. These strategies to design peptides and methods to fabricate the immunosensors are generic, and can be applied to other types of biosensors, including in low cost platforms for point-of-care diagnostics., CNPq, CAPES and FAPESP (2018/22214-6, 2017/24839-0, 2013/07600-3, 2018/18953-8 and 2018/18231-2) supported the work. EMC is a senior researcher of the CNPq (grant 301975/2018-3).

The capacitive electrolyte–insulator–semiconductor (EIS) structure is a typical device based on a field-effect sensor platform. With a simple silicon-based structure, EIS have been useful for several sensing applications, especially with incorporation of nanostructured films to modulate the ionic transport and the flat-band potential. In this paper, we report on ion transport and changes in flat-band potential in EIS sensors made with layer-by-layer films containing poly(amidoamine) (PAMAM) dendrimer and single-walled carbon nanotubes (SWNTs) adsorbed on p-Si/SiO2/Ta2O5 chips with an Al ohmic contact. The impedance spectra were fitted using an equivalent circuit model, from which we could determine parameters such as the double-layer capacitance. This capacitance decreased with the number of bilayers owing to space charge accumulated at the electrolyte–insulator interface, up to three PAMAM/SWNTs bilayers, after which it stabilized. The charge-transfer resistance was also minimum for three bilayers, thus indicating that this is the ideal architecture for an optimized EIS performance. The understanding of the influence of nanostructures and the fine control of operation parameters pave the way for optimizing the design and performance of new EIS sensors.

Polyethylene glycol (PEG) fatty acid esters are used in various industries for their interfacial properties, especially because their emulsifying characteristics can be varied considerably by altering the size of the PEG or fatty acid chains. In this study, we combine experimental surface-specific methods and molecular dynamics (MD) simulations to probe the effects from changing both the hydrophilic and hydrophobic chain sizes. PEG fatty acids containing either stearic or palmitic acid ethoxylated PEG chains of average molecular weight 200 or 400 g mol −1 (referred to as PEG200 and PEG400, respectively) had critical aggregation concentrations between 30 and 50 μM, and formed Langmuir films at the air/water interface with compressibility modulus typical of liquid-expanded phases. The area per molecule was consistently smaller for the PEG200 series owing to an increased ordering of the hydrophilic chains inferred from the polarization-modulated infrared reflection absorption (PM-IRRAS) spectra, which was corroborated by MD simulations. With PM-IRRAS and MD simulations, we also noted that the hydrophobic chain had increased order when its size increased from palmitic to stearic acid, which was attributed to a higher melting temperature for longer saturated hydrocarbon chains.

FAPESP (Brazil) CNPq (Brazil) CAPES (Brazil) nBioNet (Brazil) We report on the interaction between mer-[RuCl3(dppb)(VPy)] (dppb = 1,4-bis(diphenylphosphine)-butane and VPy=4-vinylpyridine) (RuVPy) and dipalmitoyl phosphatidyl serine (DPPS), in Langmuir and Langmuir-Blodgett (LB) films. Interaction of RuVPy with DPPS, which predominates in cancer cell membranes, should be weaker than for other phospholipids since RuVPy is less toxic to cancer cells than to healthy cells. Incorporation of RuVPy induced smaller changes in electrochemical properties of LB films of DPPS than for other phospholipids, but the same did not apply to surface pressure isotherms. This calls for caution in establishing correlations between effects from a single property and phenomena on cell membranes. (C) 2014 Elsevier B.V. All rights reserved. Univ Estadual Ponta Grossa, Appl Chem Program, BR-84035900 Ponta Grossa, PR, Brazil Univ Sao Paulo, Sao Carlos Inst Phys, BR-13560970 Sao Carlos, SP, Brazil Univ Fed Sao Paulo, Dept Exact Sci, BR-09972270 Diadema, SP, Brazil Univ Fed Sao Paulo, Dept Exact Sci, BR-09972270 Diadema, SP, Brazil Web of Science

On-site monitoring of pesticides in food, water and in the environment is crucial for human health, and this requires low cost, portable devices for widespread deployment of the technology. In this paper, we report on selective, sensitive detection and discrimination of four classes of pesticides, namely carbendazim (carbamate), diuron (phenylamide), paraquat (bipyridinium) and fenitrothion (organophosphate), using a set of three glove-embedded sensors printed on three fingers of a rubber glove. The sensors consisted of a pre-treated screen-printed carbon electrode and two other such electrodes coated with either carbon spherical shells (CSS) or Printex carbon nanoballs (PCNB). Detection of carbendazim and diuron was performed using differential pulse voltammetry (DPV) and the electrodes coated with CSS and PCNB, respectively, with limits of detection of 4.7 × 10–8 and 9.2 × 10–7 mol L–1. Square wave voltammetry (SWV) was applied to detect paraquat and fenitrothion with limits of detection 2.4 × 10–8 and 6.4 × 10–7 mol L–1 using the pretreated electrode in sulfuric acid solution. The high performance and discrimination of the pesticides at distinct concentrations in real samples of apple and cabbage by simply touching with the glove, and in orange juice by immersing the fingers was demonstrated with multidimensional projections. The sensors were robust against flexion in multiple times, stable and had reproducible response with no interference from other pesticides. With their high selectivity, sensitivity, easy operation and rapid pesticide detection, these glove-embedded sensors may also be employed in on-site analysis of other chemical threats and be extended to environmental and water samples.

Failure to control the levels of emerging pollutants in water supply can affect the quality of human life, and this may be mitigated with a low-cost, real-time monitoring system. Herein, we describe a paper-based fully printed electrochemical sensor with reduced graphene nanoribbons (rGNR) capable of detecting sulfamethoxazole (SMX) and trimethoprim (TMP) antibiotics simultaneously in real water samples. The electrodes were printed on parchment paper, which is environmentally friendly and has an efficient printing capacity. Deposition of rGNRs in the matrix was confirmed with Raman spectroscopy, transmission electron microscopy (TEM), and X-ray photoemission spectroscopy (XPS). Optimized sensing performance was obtained using an electrochemical treatment of the electrodes at neutral pH. The paper-based sensor displayed a linear response from 1 μmol l−1 to 10 μmol l−1 for both antibiotics, with detection limits of 0.09 μmol l−1 and 0.04 μmol l−1 for SMX and TMP, respectively. The sensor was reproducible, with an RSD below 5%, and selective for the antibiotics including in real samples, in a demonstration of its potential for real-time monitoring of water supply systems.

The fight against drug resistance in chemotherapy requires a molecular-level understanding of the drug interaction with cell membranes, which today is feasible with membrane models. In this study, we report on the interaction of gemcitabine (GEM), a pyrimidine nucleoside antimetabolite used to treat pancreatic cancer, with Langmuir films that mimic healthy and cancerous cell membranes. The cell membrane models were made with eight compositions of a quaternary mixture containing 1,2-dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC), 1,2-dipalmitoyl-sn-glycero-3-phosphoserine (DPPS), sphingomyelin (SM), and cholesterol (CHOL). The relative concentration of SM was increased so that four of these compositions represented cancerous cells. GEM was found to increase the mean molecular area, also increasing their surface elasticity, with stronger interactions being observed for membranes corresponding to cancerous cells. More specifically, GEM penetrated deepest in the membrane with the highest SM concentration (40 mol%), as inferred from polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS). This finding was confirmed with molecular dynamics simulations that also indicated how GEM approaches the membrane, which could be useful for guiding the design of drug delivery systems. The experimental and simulation results are consistent with the preferential attachment of GEM onto cancerous cells and highlight the role of SM on drug-cell interactions.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) are promising for gas sensors owing to their large surface-to-volume ratios, but the long recovery times stemming from the slow molecular desorption have been an important limitation. In this work, we report on a sensor for nitrogen dioxide (NO2) made with a diselenide (WSe2) monolayer synthesized via chemical vapor deposition, which functions within a range of concentrations from 100 ppb to 5 ppm and at various temperatures, including room temperature. When operated at an optimized temperature of 250 °C, the WSe2 sensor exhibited the fast recovery, with the response (τres) and recovery (τrec) times of 18 s and 38 s, respectively, when exposed to 100 ppb NO2. The sensor also features high selectivity toward NO2 in the presence of other target gases, in addition to reversibility and long-term stability within 60 days. The overall characteristics of the WSe2 sensor make it suitable to monitor indoor/outdoor environments, mainly if further optimization is made with sensor design based on a model for the sensing mechanism we present in this paper.

The design of optoelectronic devices made with ZnO superlattices requires the knowledge of the refractive index, which currently can be done only for films thicker than 30 nm. In this work, we present an effective medium approach to determine the refractive index of ZnO layers as thin as 2 nm. The approach was implemented by determining the refractive index of ZnO layers ranging from 2 nm to 20 nm using spectroscopic ellipsometry measurements in multilayers. For a precise control of morphology and thickness, the superlattices were fabricated with atomic layer deposition (ALD) with alternating layers of 2 nm thick Al2O3 and ZnO, labeled as N ZnO-Al2O3, where N = 10, 20, 30, 50, 75 and 100. The total thickness of all superlattices was kept at 100 nm. The approach was validated by applying it to similar superlattices reported in the literature and fitting the transmittance spectra of the superlattices.

Made available in DSpace on 2020-12-12T02:43:22Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-09-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) In this work, we employed impedance spectroscopy measurements to investigate the electrical properties of hybrid films obtained with the sol-gel process using 3-glycidoxypropyltrimethoxysilane (GPTMS) and tetraethylorthosilicate (TEOS) at different GPTMS/TEOS molar ratios and temperatures of thermal treatment. For the GPTMS/TEOS-derived samples with 1:1 composition, the DC conductivity (σdc) and charge carrier mobility (μdc) increased linearly with heat treatment temperature from 25 to 80 °C, while σdc increased from 3.2 to 22.4 nS/cm with a 7-fold increase in the GPTMS concentration. These results could be rationalized with the Miller-Abraham model using a charge carrier activation energy of 0.54 ± 0.03 eV. Using FTIR spectroscopy we demonstrated that the structural arrangement of the hybrid matrix involves epoxy ring opening, thus favoring proton conduction, which occurs as in the Grotthuss mechanism via hopping between nearest oxygen atoms of polymerized glycidoxypropyl groups. It is significant that electrical properties of organic/silica matrices can be predicted and tuned for tailored applications using the modeling presented here. Department of Physics Sao Paulo State University (UNESP) Institute of Geosciences and Exact Sciences Sao Carlos Institute of Physics University of Sao Paulo (USP), CP 369 Department of Physics Sao Paulo State University (UNESP) Institute of Geosciences and Exact Sciences FAPESP: 2011/18149-5 FAPESP: 2013/14262-7 CNPq: 427220/2018-1 CNPq: 444810/2014-5

The development of simple detection methods aimed at widespread screening and testing is crucial for many infections and diseases, including prostate cancer where early diagnosis increases the chances of cure considerably. In this paper, we report on genosensors with different detection principles for a prostate cancer specific DNA sequence (PCA3). The genosensors were made with carbon printed electrodes or quartz coated with layer-by-layer (LbL) films containing gold nanoparticles and chondroitin sulfate and a layer of a complementary DNA sequence (PCA3 probe). The highest sensitivity was reached with electrochemical impedance spectroscopy with the detection limit of 83 pM in solutions of PCA3, while the limits of detection were 2000 pM and 900 pM for cyclic voltammetry and UV–vis spectroscopy, respectively. That detection could be performed with an optical method is encouraging, as one may envisage extending it to colorimetric tests. Since the morphology of sensing units is known to be affected in detection experiments, we applied machine learning algorithms to classify scanning electron microscopy images of the genosensors and managed to distinguish those exposed to PCA3-containing solutions from control measurements with an accuracy of 99.9%. The performance in distinguishing each individual PCA3 concentration in a multiclass task was lower, with an accuracy of 88.3%, which means that further developments in image analysis are required for this innovative approach., Graphical abstract Image 1, Highlights • Low-cost biosensors fabricated with gold nanoparticles and chondroitin sulfate used for detecting PCA3 biomarker. • PCA3 detection from machine learning with accuracy of 99.9%. • The highest sensitivity was reached with electrochemical impedance spectroscopy with the detection limit of 83 pM.

Two kinds of flexible ozone (O3) sensors were obtained by placing pristine ZnO nanorods and gold-modified ZnO nanorods (NRs) on a bi-axially oriented poly(ethylene terephthalate) substrate. The chemiresistive sensor is operated at typically 1 V at room temperature under the UV-light illumination. The ZnO nanorods were prepared via a hydrothermal route and have a highly crystalline wurtzite structure, with diameters ranging between 70 and 300 nm and a length varying from 1 to 3 μm. The ZnO NRs were then coated with a ca. 10 nm gold layer whose presence was confirmed with microscopy analysis. This sensor is found to be superior to detect ozone at a room temperature. Typical figures of merit include (a) a sensor response of 108 at 30 ppb ozone for gold-modified ZnO NRs, and (b) a linear range that extends from 30 to 570 ppb. The sensor is stable, reproducible and selective for O3 compared to other oxidizing and reducing gases. The enhanced performance induced by the modification of ZnO nanorods with thin layer of gold is attributed to the increased reaction kinetics compared to pristine ZnO NRs. The sensing mechanism is assumed to be based on the formation of a nano-Schottky type barrier junction at the interface between gold and ZnO.

Graphene-based microfluidic devices can be useful for biosensors and for studying biological systems owing to their comparable length scales and flow characteristics. In sensing and biosensing, the goal in microfluidics research is to develop integrated miniaturized devices capable of achieving high sensitivity and selectivity, rapid response, multiplexing, automation and allow for tests with a small sample volume. In this chapter, a description is presented of fabrication techniques of graphene and derivatives, particularly focused on their possible application in microfluidic devices. A major emphasis is placed on the challenges to reach point-of-care diagnostics, which requires considerably more extensive research as only a few graphene-related studies involving microfluidic devices are available in the literature.

Hemoglobin-containing electrochemical biosensors are useful for detecting hydrogen peroxide through oxidation of the iron ion, but high efficiency can only be reached with appropriate immobilization strategies for hemoglobin. In this work, we combined zein from corn seed with carbon black to immobilize hemoglobin, as proof of concept, and form an electroactive film that could determine hydrogen peroxide within the concentration range from 4.9 × 10−6 to 3.9 × 10−4 mo L−1, and limit of detection of 4.0 × 10−6 mol L−1, using differential pulse voltammetry. The biosensor could also detect hydrogen peroxide in commercial samples of oxygenated water, synthetic serum (physiological and glycoside) and milk. The high performance is ascribed to the large surface area and conductive nature of the porous film that had carbon black and hemoglobin anchored on zein microspheres, according to scanning and transmission electron microscopies. It is significant that a protein from renewable sources (zein) combined with a low-cost carbon material (carbon black) serves as matrix for immobilization of biomolecules.