Substrate Surface Chemistry Research Articles

Manipulating Interface Magnetism in Manganite Thin Film Membranes by Substrate Surface Chemistry

Manipulating Interface Magnetism in Manganite Thin Film Membranes by Substrate Surface Chemistry

Characterization of a Food‐Safe Colorimetric Indicator Based on Black Rice Anthocyanin/PET Films for Visual Analysis of Fish Spoilage

ABSTRACTThe safety of food products is of prime importance for consumers and manufacturers. Many means can be used to validate a food product's safety before it is consumed. This study is about the preparation, characterization and evaluation of a generally recognized as safe (GRAS) sensitive colorimetric sensor that detects volatile gases (TVB‐N) resulting from fish spoilage, thus indicating the pH variation of packaged fish products. This is performed by coating a thin layer of ink sensors on the surface of the supporting matrix (corona‐treated PET). Various visual pH indicators were prepared based on black rice anthocyanin as an FDA‐approved dye. Black rice, which contains more than 80% cyanidin‐3‐glucoside, is the most prevalent anthocyanin component. Because of its low toxicity and high concentration, it can be utilized as a natural food colourant. pH indicators based on black rice can show distinct colours in various pH: from red (low pH) to violet (4–6) and deep purple/blue (6–7), blue (7–9) to yellowish/light brown (9–13) throughout the acid–base reaction by the analyte. The ink formulation was prepared by incorporating a binder system (PVOH‐PEG) for higher surface wettability, a crosslinking agent (citric acid) for higher adhesion, an antifoaming agent (natural vanillin) and acetic acid as a pH fixing agent. Corona treatments affected substrate surface chemistry in this study. The samples with thermal treatment passed the ASTM D3330 tape test, the 8000 passages for dry sponge and the 25 passages for wet sponge through the abrasion method. Anthocyanin concentration in formulated ink based on calculation by UV–vis spectra is 0.240 mg/100 g. Sensitivity tests towards TVB‐N gases were carried out at a temperature of 4°C to evaluate the performance of colorimetric films with formulated ink along with thermal treatment (temperature: 165°C, time: 5 min) using the volatile gases emitted by the fish sample inside the package.

Effect of inorganic material surface chemistry on structures and fracture behaviours of epoxy resin

The mechanisms underlying the influence of the surface chemistry of inorganic materials on polymer structures and fracture behaviours near adhesive interfaces are not fully understood. This study demonstrates the first clear and direct evidence that molecular surface segregation and cross-linking of epoxy resin are driven by intermolecular forces at the inorganic surfaces alone, which can be linked directly to adhesive failure mechanisms. We prepare adhesive interfaces between epoxy resin and silicon substrates with varying surface chemistries (OH and H terminations) with a smoothness below 1 nm, which have different adhesive strengths by ~13 %. The epoxy resins within sub-nanometre distance from the surfaces with different chemistries exhibit distinct amine-to-epoxy ratios, cross-linked network structures, and adhesion energies. The OH- and H-terminated interfaces exhibit cohesive failure and interfacial delamination, respectively. The substrate surface chemistry impacts the cross-linked structures of the epoxy resins within several nanometres of the interfaces and the adsorption structures of molecules at the interfaces, which result in different fracture behaviours and adhesive strengths.

Exploring the potential of electrospun polymer-coated Ag nanofibers for synergistic SERS performance and real-world applications

Electrospinning is a prominent technique for fabricating polymer-stabilized composite nanofibers for surface-enhanced Raman scattering (SERS). However, further exploration of the surface chemistry of these electrospun composite substrates is crucial to manipulate the charge transfer (CT) effect and achieve synergistic effects between CT and localized surface plasmon resonance (LSPR) for enhanced bio-labeling and pesticide detection. Here, we present the development of a flexible and self-supporting SERS substrate using electrospinning, consisting of polymer-coated silver nanowires (AgNWs). By employing different polymer shells and probe molecules, we strategically adjusted the energy levels of the frontier orbitals, enabling effective control over the CT effect. The resulting nanofibers exhibited optimized selectivity and sensitivity through multiple CT routes, enabling the detection of thiram in apple skin using a convenient wiping sampling method with a low limit of detection (LOD) of 5 ng/cm². We also investigated other pesticides without viable CT routes to demonstrate the versatility of the composite substrates, although they exhibited relatively lower selectivity and sensitivity due to the absence of synergistic effects. This study highlights the potential of CT manipulation in harnessing synergistic effects in electrospun 2D composite nanofibers, thereby advancing the practical applications of SERS technology.

Bubble Printing of Ti3C2TX MXene for Patterning Conductive and Plasmonic Nanostructures.

MXenes represent a novel class of 2D materials with unique properties and have great potential for diverse applications in sensing and electronics; however, their directed assembly at interfaces has not yet been achieved. Herein, the plasmonic heating of MXenes was exploited to achieve the controlled deposition of MXene assemblies via a laser-directed microbubble. The influence of various factors such as solvent composition, substrate surface chemistry, MXene concentration, and laser fluence was investigated, establishing the optimal conditions for rapid patterning with good fidelity. Printed MXene assemblies showed good electrical conductivity and plasmonic sensing capabilities and were able to meet or exceed the state of the art without additional postprocessing steps. This represents the first study of a directed approach for microfabrication using MXenes and lays the foundation for future work in optically directed assembly of MXenes and MXene-based nanocomposites at interfaces toward sensors and devices.

Role of machining and exposure conditions on the surface chemistry modification of femtosecond laser-machined copper surfaces

We systematically investigate (i) how the surface chemistry of Cu substrates is altered by femtosecond laser machining LIPSS in different atmospheres and (ii) the impact of subsequent exposure conditions on the surface chemistry of Cu substrates laser-machined in an inert Ar atmosphere. All experiments were conducted by carefully avoiding exposure to uncontrolled conditions until the completion of the XPS analysis. We confirmed that hydroxyl groups present on the oxide surface significantly contribute to the chemisorption of carbonaceous species. Samples maintained in humid atmospheres presented a superior surface carbon content. In carrying out these experiments, we found that laser machining in Ar humidified with a lauric acid-ethanol solution provided the highest C/Cu ratio, while the lowest C/Cu ratio was observed for the sample machined in the inert Ar environment. We confirmed that the decomposition of CO2 into carbon stands less favored for our given exposure conditions (20 °C & 150 °C), and that CO2 effectively acts inert like Ar. Our experiments with acetylene demonstrate the significance of identifying a more reactive carbonaceous gas that contributes non-polar carbon to a laser-machined surface. Furthermore, immersing a laser-machined sample in a carbon-rich solution (lauric acid-ethanol solution) maximizes surface carbon content.

A Universal Cl‐PEDOT Coating Strategy Based on Oxidative Chemical Vapor Deposition toward Solar‐Driven Multifunctional Energy Management

AbstractConverting renewable solar energy into manageable thermal energy is significant for diverse applications. Nevertheless, integrating multifunctional solar‐to‐heat coating on various substrates and achieving large‐scale manufacture remains a challenge. Herein, Cl− doped poly(3,4‐ethylenedioxythiophene) (Cl‐PEDOT) coating on multiple substrates is successfully created using oxidative chemical vapor deposition (oCVD) without to be restricted to the changeable substrate surface chemistry (e.g., wettability), sizes as well as dimensions (2D–3D). Partial Cl− doping and spontaneously formed microstructures can remarkably enhance near‐infrared absorption and hydrophilicity of coating. The Cl‐PEDOT coating manifests many advantages: universality, scalability, low‐cost, high efficiency, and stability. When used for solar steam generation, all Cl‐PEDOT coated substrates represent reinforced evaporation performance. The universality makes it possible to optimize the evaporator performance by structural design. Structural design as optimized energy flow enables the pyramid array wood‐based evaporator to set an evaporation record (≈1.19 kg m−2 h−1, ≈91%) under the weak‐light (0.5 sun). Moreover, a greenhouse and a crude‐oil cleaner are designed to achieve eco‐friendly, energy‐saving solar‐driven heating/dehumidification, and crude‐oil recovery without additional energy input. This study reveals that well‐designed oCVD is a simple and straightforward way to engineer lightweight and thermally insulating polymers into multifunctional solar‐to‐thermal composites toward diverse solar‐driven applications.

Role of surface chemistry in determining the heteroepitaxial growth of Ir films on a-plane α-Al2O3 single crystals

Heteroepitaxy has increased in importance as the development of the semiconductor industry has advanced and a number of heteroepitaxial devices have been developed. In this study, Ir films of (001) or (111) preferred orientation were deposited onto a-plane α-Al2O3 surfaces pretreated via annealing in air and/or Ar+ ion etching. Ir (001) films were epitaxially grown on α-Al2O3 substrates with an in-plane orientation relationship of Ir (001)[110]//α-Al2O3 (112¯0)[0001]. In contrast, (111) films were non-epitaxial with the out-of-plane orientation relationship of Ir (111)// α-Al2O3 (112¯0). The effects of annealing in air and Ar+ ion etching on Ir film growth were then analyzed. Annealing in air can lead to a terrace morphology and a lower Al/O atomic ratio of 1/2 than 2/3 for α-Al2O3 surfaces, and a better Ir film crystallinity due to the step-flow mechanism; however, this was not the key factor for Ir heteroepitaxy. Ar+ ion etching was regarded as an irreplaceable pretreatment procedure. The surface chemistry of α-Al2O3 substrates was characterized via X-ray photoelectron spectroscopy. Carbon adsorbate (C = O, CC, CO, etc.) on substrate surfaces was drastically reduced after etching. Interfacial structures were observed by transmission electron spectroscopy. Two different stacking sequences were observed along the out-of-plane direction of α-Al2O3 (112¯0) surface, representing the 〈111〉 and 〈001〉 crystal directions, respectively; C element enrichment was observed at the interface without etching. Finally, the interaction between Ir films and α-Al2O3 substrates, which is probably influenced by the surface chemistry, is considered to be the growth mechanism of Ir films. This study provides significant insights into the role of the surface chemistry in the epitaxial growth of films.

Comparison between polycrystalline Au and single-crystalline Au(1 1 1) electrodes as the substrate of a cationic organic monolayer based on their anion dependent redox activities

The structures of organic monolayers immobilized on a metal electrode and their functions depend on the substrate surface chemistry and morphology. A better defined crystalline flat electrode usually provides a structurally more ordered organic monolayer, although the use of a single-crystalline electrode costs more for mass production. Because the monolayer structures at both molecular and mesoscopic levels are critical to the functions of the modified electrode, in-depth experimental studies to clarify the relationship between the functions and the surface morphology of the electrode are crucial. In this work, we compared polycrystalline Au (poly-Au) and single-crystalline Au(111) electrodes as the substrates for a redox-active, self-assembled monolayer (SAM) of an alkyl-viologen thiol, 1-(10-mercaptodecyl)-1′-methyl-4,4′-bipyridinium dibromide (MeVC10-SH 2Br−). The voltammetric and electroreflectance measurements were performed at a mirror-polished poly-Au electrode and a flame-annealed single-crystalline Au(111) electrode after their surface modification with a MeVC10-SH monolayer. We found significant differences in the anion effects on the voltammetric behavior between the two substrates, especially in the dependence on anion hydrophobicity. The electroreflectance spectra revealed a tendency that a greater abundance of the viologen radical cation dimers at a Au(111) than that at a poly-Au. A considerable Br− adsorption at the SAM-modified Au(111) electrode was observed because of the loose packing of immobilized MeVC10-SH molecules. We discussed the origins of the contrasting behavior resulting from the difference of the surface.

Structural, Dynamic, and Chemical Complexities in Zinc Anode of an Operating Aqueous Zn‐Ion Battery (Adv. Energy Mater. 21/2022)

Zn-ion Batteries In article number 2200255, Linsen Li, Yijin Liu and co-workers visualize the nucleation and growth of Zn dendrites in a functioning Zn-ion battery. Their study reveals that the Zn plating behavior is collectively modulated by cell/electrode architecture, substrate local morphology, electrochemical protocols, and surface chemistry. These insights are expected to critically inform the development of next-generation dendrite-free and long-span aqueous Zn-ion batteries.

Recent advances in non-plasmonic surface-enhanced Raman spectroscopy nanostructures for biomedical applications.

Surface-enhanced Raman spectroscopy (SERS) is an emerging powerful vibrational technique offering unprecedented opportunities in biomedical science for the sensitive detection of biomarkers and the imaging and tracking of biological samples. Conventional SERS detection is based on the use of plasmonic substrates (e.g., Au and Ag nanostructures), which exhibit very high enhancement factors (EF=1010 -1011 ) but suffers from serious limitations, including light-induced local heating effect due to ohmic loss and expensive price. These drawbacks may limit detection accuracy and large-scaled practical applications. In this review, we focus on alternative approaches based on plasmon-free SERS detection on low-cost nanostructures, such as carbons, oxides, chalcogenides, polymers, silicons, and so forth. The mechanism of non-plasmonic SERS detection has been attributed to interfacial charge transfer between the substrate and the adsorbed molecules, with no photothermal side-effects but usually less EF compared with plasmonic nanostructures. The strategies to improve Raman signal detection, through the tailoring of substrate composition, structure, and surface chemistry, is reviewed and discussed. The biomedical applications, for example, SERS cell characterization, biosensing, and bioimaging are also presented, highlighting the importance of substrate surface functionalization to achieve sensitive, accurate analysis, and excellent biocompatibility. This article is categorized under: Diagnostic Tools > Diagnostic Nanodevices Diagnostic Tools > Biosensing Diagnostic Tools > In Vivo Nanodiagnostics and Imaging.

Improvement of Mesenchymal Stromal Cell Proliferation and Differentiation via Decellularized Extracellular Matrix on Substrates With a Range of Surface Chemistries.

Decellularized extracellular matrix (dECM) deposited by mesenchymal stromal cells (MSCs) has emerged as a promising substrate for improved expansion of MSCs. To date, essentially all studies that have produced dECM for MSC expansion have done so on tissue culture plastic or glass. However, substrate surface chemistry has a profound impact on the adsorption of proteins that mediate cell-material interactions, and different surface chemistries can cause changes in cell behavior, ECM deposition, and the in vivo response to a material. This study tested the hypothesis that substrate surface chemistry impacts the deposition of ECM and its subsequent bioactivity. This hypothesis was tested by producing glass surfaces with various surface chemistries (amine, carboxylic acid, propyl, and octyl groups) using silane chemistry. ECM was deposited by an immortalized MSC line, decellularized, and characterized through SDS-PAGE and immunofluorescence microscopy. No significant difference was observed in dECM composition or microarchitecture on the different surfaces. The decellularized surfaces were seeded with primary MSCs and their proliferation and differentiation were assessed. The presence of dECM improved the proliferation of primary MSCs by ~100% in comparison to surface chemistry controls. Additionally, the adipogenesis increased by 50–90% on all dECM surfaces in comparison to surface chemistry controls, and the osteogenesis increased by ~50% on the octyl-modified surfaces when dECM was present. However, no statistically significant differences were observed within the set of dECM surfaces or control surfaces. These results support the null hypothesis, meaning surface chemistry (over the range tested in this work) is not a key regulator of the composition or bioactivity of MSC-derived dECM. These results are significant because they provide an important insight into regenerative engineering technologies. Specifically, the utilization of dECM in stem cell manufacturing and tissue engineering applications would require the dECM to be produced on a wide variety of substrates. This work indicates that it can be produced on materials with a range of surface chemistries without undesired changes in the bioactivity of the dECM.

Electrodeposition of Crystalline Germanium on Glass

The research objective of this work is to test the hypothesis that crystalline germanium can be deposited on insulating substrates through electrochemical-liquid phase epitaxy (ec-LPE). In doing so, this work establishes a new method of semiconductor-on-insulator fabrication. Semiconductor-on-insulator device constructs are at the heart of all modern electronics. Methods that simplify fabrication by lowering the thermal budget and eliminating hazardous precursors are highly desirable. Recently, a new method for the direct preparation of covalent semiconductor crystals at ambient conditions, ec-LPE, was demonstrated by our group. This method utilizes thin liquid metal films simultaneously to perform electrochemical reduction of precursors and to direct heterogeneous nucleation at an underlying substrate of interest. In this work, the fabrication of germanium-on-glass using ec-LPE is demonstrated for the first time. Amperometry, microscopy, and Raman spectroscopy will be presented to demonstrate the proof of principle, i.e. the growth of Ge crystals electrochemically on insulating glass. The surface chemistry of glass substrates will be discussed, including glass functionalized with (3-Aminopropyl)triethoxysilane (APTES), and N-(Trimethoxysilylpropyl)ethylene-diamine triacetic acid (EDTA–TMS). Surfaces with a higher chelating group density improved the efficacy of Ge ec-LPE. These results set the groundwork for semiconductor-on-insulator process development based on ec-LPE.

Are Contact Angle Measurements Useful for Oxide-Coated Liquid Metals?

This work establishes that static contact angles for gallium-based liquid metals have no utility despite the continued and common use of such angles in the literature. In the presence of oxygen, these metals rapidly form a thin (∼1-3 nm) surface oxide "skin" that adheres to many surfaces and mechanically impedes its flow. This property is problematic for contact angle measurements, which presume the ability of liquids to flow freely to adopt shapes that minimize the interfacial energy. We show here that advancing angles for a metal are always high (>140°)-even on substrates to which it adheres-because the solid native oxide must rupture in tension to advance the contact line. The advancing angle for the metal depends subtly on the substrate surface chemistry but does not vary strongly with hydrophobicity of the substrate. During receding measurements, the metal droplet initially sags as the liquid withdraws from the "sac" formed by the skin and thus the contact area with the substrate initially increases despite its volumetric recession. The oxide pins at the perimeter of the deflated "sac" on all the surfaces are tested, except for certain rough surfaces. With additional withdrawal of the liquid metal, the pinned angle gets smaller until eventually the oxide "sac" collapses. Thus, static contact angles can be manipulated mechanically from 0° to >140° due to hysteresis and are therefore uninformative. We also provide recommendations and best practices for wetting experiments, which may find use in applications that use these alloys such as soft electronics, composites, and microfluidics.

Tuning Strain Sensor Performance via Programmed Thin-Film Crack Evolution.

Stretchable strain sensors with well-controlled sensitivity and stretchability are crucial for applications ranging from large deformation monitoring to subtle vibration detection. Here, based on single-metal material on the elastomer and one-pot evaporation fabrication method, we realize controlled strain sensor performance via a novel programable cracking technology. Specifically, through elastomeric substrate surface chemistry modification, the microcrack generation and morphology evolution of the strain sensing layer is controlled. This process allows for fine tunability of the cracked film morphology, resulting in strain sensing devices with a sensitivity gauge factor of over 10 000 and stretchability up to 100%. Devices with a frequency response up to 5.2 Hz and stability higher than 1000 cycles are reported. The reported strain sensors, tracking both subtle and drastic mechanical deformations, are demonstrated in healthcare devices, human-machine interaction, and smart-home applications.

Polymer-Based Honeycomb Films on Bioactive Glass: Toward a Biphasic Material for Bone Tissue Engineering Applications.

The development of innovative materials for bone tissue engineering to promote bone regeneration while avoiding fibrous tissue infiltration is of paramount importance. Here, we combined the known osteopromotive properties of bioactive glasses (BaGs) with the biodegradability, biocompatibility, and ease to shape/handle of poly-l-co-d,l-lactic acid (PLDLA) into a single biphasic material. The aim of this work was to unravel the role of the surface chemistry and topography of BaG surfaces on the stability of a PLDLA honeycomb membrane, in dry and wet conditions. The PLDLA honeycomb membrane was deposited using the breath figure method (BFM) on the surface of untreated BaG discs (S53P4 and 13-93B20), silanized with 3-aminopropyltriethoxysilane (APTES) or conditioned (immersed for 24 h in TRIS buffer solution). The PLDLA membranes deposited onto the BaG discs, regardless of their composition or surface treatments, exhibited a honeycomb-like structure with pore diameter ranging from 1 to 5 μm. The presence of positively charged amine groups (APTES grafting) or the precipitation of a CaP layer (conditioned) significantly improved the membrane resistance to shear as well as its stability upon immersion in the TRIS buffer solution. The obtained results demonstrated that the careful control of the substrate surface chemistry enabled the deposition of a stable honeycomb membrane at their surface. This constitutes a first step toward the development of new biphasic materials enabling osteostimulation (BaG) while preventing migration of fibrous tissue inside the bone defect (honeycomb polymer membrane).

Rapid exposure monitoring of six bisphenols and diethylstilbestrol in human urine using fabric phase sorptive extraction followed by high performance liquid chromatography – photodiode array analysis

A novel fabric phase sorptive extraction protocol is developed for rapid exposure monitoring of six bisphenol analogues, including bisphenol A, bisphenol S, bisphenol F, bisphenol E, bisphenol B, bisphenol C, and diethylstilbestrol (DES) from human urine prior to high-performance liquid chromatography-photodiode array analysis.FPSE sample pretreatment protocol ensures the harmonization of the proposed method with the principles of Green Analytical Chemistry (GAC). Among eighteen evaluated FPSE membranes, sol-gel poly (ethylene glycol) (PEG) coated cellulose FPSE membrane resulted in the most efficient extraction. This polar FPSE membrane effectively exploits a number of advantageous features inherent to FPSE including sponge-like porous architecture of the sol-gel sorbent coating, favorable surface chemistry, flexibility and built-in permeability of cellulose fabric substrate, high primary contact surface area for rapid sorbent-analyte interaction, expanded pH, solvent and thermal stability as well as reusability of the FPSE membrane.Optimization was centered on the evaluation of critical parameters, namely the size of the FPSE membrane, the elution solvent mixture, the volume of the sample, the extraction time, the elution time, the kind of the external agitation mechanical stimulus, the ionic strength and the pH of the sample. The chromatographic separation was achieved on a Spherisorb C18 column and a gradient elution program with mobile phase consisted of 0.05 ammonium acetate solution and acetonitrile. The total analysis time was 17.4 min. The developed method was validated in terms of linearity, sensitivity, selectivity, precision, accuracy, stability, and ruggedness. The limits of detection and quantification varied from 0.26–0.62 ng/mL and 0.8–1.9 ng/mL, respectively. The relative recoveries were calculated between 90.6 and 108.8%, while the RSD values were <10% in all cases. The effectiveness of the proposed method was confirmed by its successful implementation in the bioanalysis of real urine samples.

Fabric Phase Sorptive Extraction: A Paradigm Shift Approach in Analytical and Bioanalytical Sample Preparation.

Fabric phase sorptive extraction (FPSE) is an evolutionary sample preparation approach which was introduced in 2014, meeting all green analytical chemistry (GAC) requirements by implementing a natural or synthetic permeable and flexible fabric substrate to host a chemically coated sol–gel organic–inorganic hybrid sorbent in the form of an ultra-thin coating. This construction results in a versatile, fast, and sensitive micro-extraction device. The user-friendly FPSE membrane allows direct extraction of analytes with no sample modification, thus eliminating/minimizing the sample pre-treatment steps, which are not only time consuming, but are also considered the primary source of major analyte loss. Sol–gel sorbent-coated FPSE membranes possess high chemical, solvent, and thermal stability due to the strong covalent bonding between the fabric substrate and the sol–gel sorbent coating. Subsequent to the extraction on FPSE membrane, a wide range of organic solvents can be used in a small volume to exhaustively back-extract the analytes after FPSE process, leading to a high preconcentration factor. In most cases, no solvent evaporation and sample reconstitution are necessary. In addition to the extensive simplification of the sample preparation workflow, FPSE has also innovatively combined the extraction principle of two major, yet competing sample preparation techniques: solid phase extraction (SPE) with its characteristic exhaustive extraction, and solid phase microextraction (SPME) with its characteristic equilibrium driven extraction mechanism. Furthermore, FPSE has offered the most comprehensive cache of sorbent chemistry by successfully combining almost all of the sorbents traditionally used exclusively in either SPE or in SPME. FPSE is the first sample preparation technique to exploit the substrate surface chemistry that complements the overall selectivity and the extraction efficiency of the device. As such, FPSE indeed represents a paradigm shift approach in analytical/bioanalytical sample preparation. Furthermore, an FPSE membrane can be used as an SPME fiber or as an SPE disk for sample preparation, owing to its special geometric advantage. So far, FPSE has overwhelmingly attracted the interest of the separation scientist community, and many analytical scientists have been developing new methodologies by implementing this cutting-edge technique for the extraction and determination of many analytes at their trace and ultra-trace level concentrations in environmental samples as well as in food, pharmaceutical, and biological samples. FPSE offers a total sample preparation solution by providing neutral, cation exchanger, anion exchanger, mixed mode cation exchanger, mixed mode anion exchanger, zwitterionic, and mixed mode zwitterionic sorbents to deal with any analyte regardless of its polarity, ionic state, or the sample matrix where it resides. Herein we present the theoretical background, synthesis, mechanisms of extraction and desorption, the types of sorbents, and the main applications of FPSE so far according to different sample categories, and to briefly show the progress, advantages, and the main principles of the proposed technique.

Modulating the Stress Response of E. coli at GaN Interfaces Using Surface Charge, Surface Chemistry, and Genetic Mutations.

The surface properties of inorganic materials can be used to modulate the response of microorganisms at the interface. We used the persistent photoconductivity properties of chemically treated gallium nitride substrates to evaluate the stress response of wild-type, ΔfliC, and ΔcsgG mutant E. coli exposed to charged surfaces. Substrate surface characterization and biological assays were used to correlate the physiological response to substrate surface charge. The physiological response was evaluated by measuring the intracellular levels of reactive oxygen species (ROS) and Ca2+ cations using fluorescent probes. We evaluated the response 1, 2, and 3 h after a short exposure to the surfaces to determine generational effects of the initial exposure on the physiology of the bacteria. In general, the ROS levels 1 h after exposure were not different. However, there were differences in Ca2+ levels in E. coli 1 h after the initial exposure to charged GaN surfaces, primarily in the wild-type E. coli. The differences in Ca2+ levels depended on the substrate surface chemistry and genetic mutation that suggests the involvement of multiple factors for modulating the interactions of bacteria at interfaces.

Fabric phase sorptive extraction combined with high-performance-liquid chromatography-photodiode array analysis for the determination of seven parabens in human breast tissues: Application to cancerous and non-cancerous samples

An improved pretreatment approach of human breast tissue is demonstrated for subsequent analysis of seven parabens including methyl paraben (MPB), ethyl paraben (EPB), propyl paraben (PPB), butyl paraben (BPB), isopropyl paraben (iPPB), isobutyl paraben (iBPB), and benzyl paraben (BzPB). Specifically, a well-designed homogenization procedure, conjugated with an optimized fabric phase sorptive extraction (FPSE) protocol, resulted in a carefully outlined sample preparation process as part of a green, simple, sensitive, economical and fast HPLC-PDA analytical method in agreement with Green Analytical Chemistry (GAC) demands. Among all tested FPSE membranes, the highest extraction efficiency was achieved by employing sol-gel poly(tetrahydrofuran) (sol-gel PTHF) coating on 100% cotton cellulose fabric that represents a medium polarity microextraction device, which combined the advanced material characteristics of sol-gel sorbent and the rich surface chemistry of an inherent porous cellulose fabric substrate. The chromatographic separation was accomplished with a Spherisorb C18 column and an isocratic mobile phase consisted of ammonium acetate and acetonitrile at a flow rate of 1.4 mL/min. The total analysis time was 13.6 min. The analytical adequacy of the composite sample preparation and chromatographic separation method was strongly evidenced by its successful application in the bioanalysis of real cancerous and non-cancerous tissue samples originated from different sub regions of human breast including axila, the upper left and the right quadrant. In all samples, at least one paraben was detected, while 35% of the samples were tested positive for all seven target parabens. Moreover, concentration levels of parabens in cancerous tissues were unambiguously higher than in healthy tissues. The obtained results underlined bioaccumulation potential of parabens in human breast tissue as a consequence of constant low-dose exposure of humans, despite the statutory concentration limits. The developed methodology has demonstrated to be suitable and efficient for future epidemiological and toxicological studies.