Surface Regeneration Research Articles

A gold nanoparticle-assisted sensitive SAW (surface acoustic wave) immunosensor with a regeneratable surface for monitoring of dust mite allergens

Signal amplification in a surface acoustic wave (SAW) immunosensor is demonstrated by increasing mass and/or viscoelasticity on a delay line sensing surface with gold nanoparticles (AuNPs) for monitoring of airborne house dust mite (HDM) allergens. Streptavidin conjugated AuNPs with size of 20nm are affinity-bound to biotinylated detection antibodies (dAb) that are already on the sensor surface together with capture antibody (cAb) and group 1 HDM allergens of Dermatophagoides farinae (Der f 1) as a result of a sandwich assay. This immunocomplex except for immobilized cAb on the sensor surface is then removed by pH change for regeneration of the surface. Surface modification of the SAW immunosensor with a self-assembled monolayer of pH resistant protein (ORLA85 protein) allows to repeat a process including immunoassay and surface regeneration for a repetitive measurement of Der f 1. It is revealed that capping a surface of AuNP with a monolayer of (11-mercaptoundecyl)tri(ethylene glycol) (3PEG-thiol) reduces non-specific binding to the sensor surface, and aggregation among AuNPs. The sensor output is amplified by a factor of 3 with respect to that obtained without AuNP when a molar concentration of AuNPs is about 3-fold higher than that of dAb. A limit of detection for Der f 1 is 2.5ng/mL (equivalent to 100 pM), which is about 2.5-fold improvement from the sandwich assay without AuNPs. Also highly reproducible sensor outputs along with efficient regeneration through successive measurement demonstrates the capability of repetitive measurement of Der f 1. These results suggest that use of AuNPs under an optimum condition in the SAW immunosensor is expected to realize a sensitive and repetitive measurement of HDM allergens, which is useful for airborne HDM monitoring system.

Sulfamide chemistry applied to the functionalization of self-assembled monolayers on gold surfaces.

Aniline-terminated self-assembled monolayers (SAMs) on gold surfaces have successfully reacted with ArSO2NHOSO2Ar (Ar = 4-MeC6H4 or 4-FC6H4) resulting in monolayers with sulfamide moieties and different end groups. Moreover, the sulfamide groups on the SAMs can be hydrolyzed showing the partial regeneration of the aniline surface. SAMs were characterized by water contact angle (WCA) measurements, Fourier-transform infrared reflection absorption spectroscopy (IRRAS) and X-ray photoelectron spectroscopy (XPS).

Lithography-Free Fabrication of Silica Nanocylinders with Suspended Gold Nanorings for LSPR-Based Sensing.

Tunable plasmonic platforms are important for a variety of applications such as photovoltaics, LED's, optoelectronics, medical research, and biosensors. In particular, development of label-free plasmonic biosensors is one of the key research areas that utilizes plasmonic nanostructures for detection of biologically relevant molecules at low concentrations. The authors have developed a cost-effective, fast, and lithography-free method to fabricate transparent fused silica nanocylinders. The technique allows tuning of nanocylinder height, diameter, and density and can be scaled to large surface areas, such as 8 in. wafers. The authors demonstrate that gold coated nanocylinders support localized surface plasmon resonances (LSPR) from visible to near infrared wavelengths. The plasmonic platform can be characterized as suspended gold nanorings and exhibits a sensitivity of 658 nm RIU–1 with a figure-of-merit of 10, comparable to other state-of-the-art LSPR sensing platforms that utilize more complex nanofabrication pathways. It was observed that the LSPR peak positions can be controlled by varying the geometry of the nanocylinders. The authors illustrate surface functionalization, biosensing, and surface regeneration properties of the platform using thiols and detection of bovine serum albumin (BSA). The observed LSPR shifts for 11-mercaptoundecanoic acid and BSA was 12 and 26 nm, respectively.

Biofunctional polyelectrolytes assembling on biosensors – A versatile surface coating method for protein detections

This paper reports a surface functionalization strategy for protein detections based on biotin-derivatized poly(l-lysine)-grafted oligo-ethylene glycol (PLL-g-OEGx-Biotin) copolymers. Such strategy can be used to attach the biomolecule receptors in a reproducible way simply by incubation of the transducer element in a solution containing such copolymers which largely facilitated the sensor functionalization at an industrial scale. As the synthesized copolymers are cationic in physiology pH, surface biotinylation can be easily achieved via electrostatic adsorption on negatively charged sensor surface. Biotinylated receptors can be subsequently attached through well-defined biotin-streptavidin interaction. In this work, the bioactive sensor surfaces were applied for mouse IgG and prostate specific antigen (PSA) detections using quartz crystal microbalance (QCM), optical sensor (BioLayer Interferometry) and conventional ELISA test (colorimetry). A limit of detection (LOD) of 0.5 nM was achieved for PSA detections both in HEPES buffer and serum dilutions in ELISA tests. The synthesized PLL-g-OEGx-Biotin copolymers with different OEG chain length were also compared for their biosensing performance. Moreover, the surface regeneration was achieved by pH stimulation to remove the copolymers and the bonded analytes, while maintaining the sensor reusability as well. Thus, the developed PLL-g-OEGx-Biotin surface assembling strategy is believed to be a versatile surface coating method for protein detections with multi-sensor compatibility.

Photoinduced Cross-Linking of Short Furan-Modified DNA on Surfaces.

We report for the first time the formation of site-specific interstrand cross-linked (ICL) surface-immobilized furan-modified DNA duplexes via singlet oxygen. 1O2, necessary for effecting furan-mediated ICL formation, was produced in situ using methylene blue or a zinc phthalocyanine derivative (TT1) as a photosensitizer. Via surface plasmon resonance spectroscopy, we show that surface ICL was achieved, and a robust link formed that enhances the stability of the 12-mer duplex even after surface regeneration. The described method represents a novel platform technology based on surfaces with addressable and stable DNA duplexes requiring only short oligonucleotides.

Surface regeneration and signal increase in surface-enhanced Raman scattering substrates.

Regenerated surface-enhanced Raman scattering (SERS) substrates allow users the ability to not only reuse sensing surfaces, but also tailor them to the sensing application needs (wavelength of the available laser, plasmon band matching). In this review, we discuss the development of SERS substrates for response to emerging threats and some of our collaborative efforts to improve on the use of commercially available substrate surfaces. Thus, we are able to extend the use of these substrates to broader Army needs (like emerging threat response).

A Reliable and Sensitive Voltammetric Determination of Mo(VI) at the In Situ Renovated Bismuth Bulk Annular Band Electrode

A study of a new type of the fast renovated, imperishable voltammetric sensor - the bismuth bulk annular band working electrode (BiABE) - applied for molybdenum(VI) determination via differential pulse adsorptive stripping voltammetry (DP AdSV), preceded by complexation of chloranilic acid (CAA) in an acetate buffer (pH 4.0), is reported. The proposed procedure is based on simple and fast regeneration of the BiABE's surface in the presence of testing solution, by application of the activation potential. Optimization of the experimental conditions included potential and time of activation, kind of the supporting electrolyte, pH, potential and time of accumulation, DP mode parameters. Influence of nonionic surfactant on the Mo(VI) signal response in the presence of XAD-7 resin was also tested. The peak current was proportional to the concentration of Mo(VI) over the range from 0.1 to 7 μg L−1 (1.0 × 10−9 to 7.3 × 10−8 mol L−1) with R = 0.9994, for accumulation time of 20 s. For 20 s of accumulation time, the detection limit was 0.02 μg L−1 (2.1 × 10−10 mol L−1) (at S/N = 3), and sensitivity was 0.049 μA/μg L−1. The relative standard deviation for 1 μg L−1 of Mo(VI) was 2.3% (n = 5). Finally, the proposed method was successfully applied to determine Mo(VI) in the certified reference waters (SPS-SW1 and SPS-SW2), Humber river sediment (HR-1), as well as the spiked tap and river water samples.

Reversible DNA micro-patterning using the fluorous effect.

We describe a new method for the immobilisation of DNA into defined patterns with sub-micron resolution, using the fluorous effect. The method is fully reversible via a simple solvent wash, allowing the patterning, regeneration and re-patterning of surfaces with no degradation in binding efficiency following multiple removal/attachment cycles of different DNA sequences.

Influence of membrane surface regeneration frequency using back pulse method on the average permeate flux

Influence of membrane surface regeneration frequency using back pulse method on the average permeate flux

Stem cells treatment in the ocular surface regeneration

The article presents the modern treatment with stem cells in the reconstruction of ocular surface. The turnover of the stem cells, the location in the limbus areas, the importance of limbal stem cells presence, the clinical appearance of stem cell deficiency, investigations method for this illness and the management of stem cell deficiency (artificial lacrimal tear drops, mini scleral contact lenses and the surgical treatment with allografts and autografts of stem cells) were taken into account.

Bionanomaterial Scaffolds for Effective Removal of Fluoride, Chromium, and Dye

Here we demonstrate, chitosan–sodium alginate based bionanomaterial scaffolds (BMS) with in situ functionalized alumina hydroxide forming scaffold like structure and its application in removal of fluoride (F–), chromium (Cr(VI)), and dye from water. Further, the bionanomaterial scaffold surface was modified with silver nanoparticles (Ag NPs) to enhance the shelf life of the bionanomaterial scaffold (BMS). This Ag NP-coated BMS exhibited as high as ∼168 and ∼60 mg g–1 fluoride uptake efficiency at pH 4 and 7, respectively. Experiments were also carried out to check the chromium removal efficiency, and results showed ∼8.5 mg g–1 of Cr(VI) uptake capacity was achieved from contaminated water at room temperature. Further, over 99% Reactive Black 5 (RB-5) removal was achieved with remarkable surface regeneration properties. To test the end user affordability, the bionanomaterial was packed both in a columnlike filter cake and tea-baglike pouches in a series of experiments. This study demonstrates a viable and ...

A novel l-leucine modified Sol-Gel-Carbon electrode for simultaneous electrochemical detection of homovanillic acid, dopamine and uric acid in neuroblastoma diagnosis

Neuroblastoma is a pediatric neuroblastic tumor arising in the sympathetic nervous crest cells. A high grade of Neuroblastoma is characterized by a high urinary excretion of homovanillic acid and dopamine. In this work l-leucine modified Sol-Gel-Carbon electrode was used for a sensitive voltammetric determination of homovanillic acid and dopamine in urine. The electrochemical response characteristics were investigated by cyclic and differential pulse voltammetry; the modified electrode has shown an increase in the effective area of up to 40%, a well-separated oxidation peaks and an excellent electrocatalytic activity. High sensitivity and selectivity in the linear range of 0,4–100μML−1 of homovanillic acid and 10–120μML−1 of dopamine were also obtained. Moreover, a sub-micromolar limit of detection of 0.1μM for homovanillic acid and 1.0μM for the dopamine was achieved. Indeed, high reproducibility with simple preparation and regeneration of the electrode surface made this electrode very suitable for the determination of homovanillic acid and dopamine in pharmaceutical and clinical preparations. The mechanism of homovanillic acid and the electrochemical oxidation at l-leucine modified Sol-Gel-Carbon electrode is described out the B3P86/6-31+G(d,p) level of theory as implemented in Gaussian software.

Photocatalytic removal of hexavalent chromium by newly designed and highly reductive TiO2 nanocrystals

Hexavalent chromium Cr(VI), a highly toxic oxyanion, widely occurs in drinking water supplies. This study designed and synthesized a new type of highly reductive TiO2 nanocrystals for photochemical Cr(VI) removal, via the thermal hydrolysis of TiCl4 in the presence of diethylene glycol (DEG). Surface analyses and hydroxyl radical measurements suggested that DEG was chemically bonded on TiO2 surface that resulted in an internal hole-scavenging effect and a high electron-releasing capacity, making it advantageous to conventional TiO2 materials. Upon UV irradiation, the synthesized TiO2 photocatalyst exhibited fast Cr(VI) reduction kinetics in diverse water chemical conditions. Fast elimination of Cr(VI) was achieved on a time scale of seconds in drinking water matrices. The removal of Cr(VI) by reductive TiO2 exhibited a three-stage kinetic behavior: an initial fast-reaction phase, a lag phase resulting from surface precipitation of Cr(OH)3(s), and a final reaction phase due to surface regeneration from oxidation-reduction induced ripening process. The lag phase disappeared in acidic conditions that prevented the formation of Cr(OH)3(s). The catalyst exhibited extremely high electron-releasing capacity that can be reused for multiple cycles of Cr(VI) removal in drinking water treatment.

Lithography-Free Fabrication of Silica Nanocylinders with Suspended Gold Nanorings for LSPR-Based Sensing.

Tunable plasmonic platforms are important for a variety of applications such as photovoltaics, LED's, optoelectronics, medical research, and biosensors. In particular, development of label-free plasmonic biosensors is one of the key research areas that utilizes plasmonic nanostructures for detection of biologically relevant molecules at low concentrations. The authors have developed a cost-effective, fast, and lithography-free method to fabricate transparent fused silica nanocylinders. The technique allows tuning of nanocylinder height, diameter, and density and can be scaled to large surface areas, such as 8 in. wafers. The authors demonstrate that gold coated nanocylinders support localized surface plasmon resonances (LSPR) from visible to near infrared wavelengths. The plasmonic platform can be characterized as suspended gold nanorings and exhibits a sensitivity of 658 nm RIU-1 with a figure-of-merit of 10, comparable to other state-of-the-art LSPR sensing platforms that utilize more complex nanofabrication pathways. It was observed that the LSPR peak positions can be controlled by varying the geometry of the nanocylinders. The authors illustrate surface functionalization, biosensing, and surface regeneration properties of the platform using thiols and detection of bovine serum albumin (BSA). The observed LSPR shifts for 11-mercaptoundecanoic acid and BSA was 12 and 26 nm, respectively.

Electrically conducting nanofiltration membranes based on networked cellulose and carbon nanostructures

Electrically enhanced fouling control is increasingly applied to membrane-based separation and requires conducting membranes with controlled properties. In this work, electrically conductive membranes based on networked cellulose (NC) and carbon nanostructures (CNS) were fabricated via vacuum filtration, followed by drying at 40°C. The morphology, structure, mechanical and electrochemical properties of these NC-CNS membranes were characterized and compared with CNS membranes. The effect of incorporating NC on the electrocatalytic activity has been analyzed. It is found that networked cellulose helps to decrease the contact angle of water from 105° to 73°. It is also found that the improved surface hydrophilicity of CNS-NC membrane assists the regeneration of electrode surface during electrolysis process. Networked cellulose yields a more dense structure with the tensile strength exceeding ten times that of CNS alone. The compaction of pore structure via incorporation of NC translates into promising results with respect to nanofiltration of divalent ions, with a rejection efficiency of 60% for MgSO4 and 47% for CaCl2, while maintaining a high flux ≥100Lm−2h−1, making them suitable for pretreatment of RO feeds.

Direct amination of dodecanol with NH3 over heterogeneous catalysts. Catalyst screening and kinetic modelling

The direct amination of dodecanol with ammonia to dodecylamine was investigated over carbon supported ruthenium, palladium, platinum, iridium and osmium catalysts. The influence of ammonia and hydrogen pressures was investigated. It was found that ammonia pressure did not influence the reaction, while extra hydrogen in the reaction mixture was beneficial for dodecanol conversion and dodecylamine selectivity. A dodecylamine yield of 83.8% was achieved with Ru/C catalyst at 150°C, 4bar ammonia and 2bar hydrogen after 24h reaction.Zero reaction order in ammonia typically implies that the rate limiting step is not related to amination, but rather to a preceding dehydrogenation step. Experimentally observed unusual positive order in hydrogen in dehydrogenation was related to deactivation by surface coking. Partial surface regeneration requires presence of hydrogen, thus explaining a positive reaction order towards this reactant. A detailed analysis of kinetic regularities, which due to specificity of the reaction mechanism could be done separately for activity and selectivity, allowed advancing a mathematical model adequately describing experimental observations.

Semi-continuous, real-time monitoring of protein biomarker using a recyclable surface plasmon resonance sensor

Although label-free immunosensors based on, for example, surface plasmon resonance (SPR) provide advantages of real-time monitoring of the analyte concentration, its application to routine clinical analysis in a semi-continuous manner is problematic because of the high cost of the sensor chip. The sensor chip is in most cases regenerated by employing an acidic pH. However, this causes gradual deterioration of the activity of the capture antibody immobilized on the sensor surface. To use sensor chips repeatedly, we investigated a novel surface modification method that enables regeneration of the sensor surface under mild conditions. We introduced a monoclonal antibody (anti-CBP Ab) that detects the conformational change in calcium binding protein (CBP) upon Ca2+ binding (>1mM). To construct a regenerable SPR-based immunosensor, anti-CBP Ab was first immobilized on the sensor surface, and CBP conjugated to the capture antibody (specific for creatine kinase-MB isoform (CK-MB); CBP-CAb) then bound in the presence of Ca2+. A serum sample was mixed with the detection antibody to CK-MB, which generated an SPR signal proportional to the analyte concentration. After each analysis, the sensor surface was regenerated using medium (pH 7) without Ca2+, and then adding fresh CBP-CAb in the presence of Ca2+ for the subsequent analysis. Analysis of multiple samples using the same sensor was reproducible at a rate >98.7%. The dose-response curve was linear for 1.75–500.75ng/mL CK-MB, with an acceptable coefficient of variation of <8.8%. The performance of the immunosensor showed a strong correlation with that of the Pathfast reference system (R2>96%), and exhibited analytical stability for 1 month. To our knowledge, this is the first report of a renewal of a sensor surface with fresh antibody after each analysis, providing high consistency in the assay during a long-term use (e.g., a month at least).

АТМОСФЕРНЫЕ ИСПАРИТЕЛИ С ПРИНУДИТЕЛЬНЫМИ КОНВЕКЦИЕЙ И ОТОГРЕВОМ

Specialists of the company NPO Monitoring Ltd. are continually working on the improvement of the produced heat exchange equipment for gasification of liquid cryogenic products. The advantages of created by the company new generation of evaporators with forced convection and regeneration (warming) of the outer surface of the devices in the autumn-winter period and their operation are considered in the work.

Aerobic selective oxidation of alcohols using La1−xCexCoO3 perovskite catalysts

The synthesis of porous perovskites with high and stable activity for alcohols oxidation using molecular oxygen as oxidant is reported. La1−xCexCoO3 catalysts are prepared by a sol–gel method using methanol and ethylene glycol as complexing agents. Calcination at 600°C allows the formation of macro- and mesopores, in contrast to similar materials that often show a bulk structure. Catalytic tests show that La0.9Ce0.1CoO3 is highly active for benzyl alcohol oxidation with molecular oxygen, with both conversion and selectivity above 95% (60min, 88°C, 1atm). Further tests show that 94% of the original activity can be obtained after surface regeneration of the used catalyst. The good catalytic performance is explained by the presence of cerium, which is able to attract and release adsorbed oxygen on the oxygen vacancies. The electrons donated by alcohols improve the ability of oxygen vacancies to activate molecular oxygen into oxygen anions, which react with the alcohol and increase the reaction rate. A mechanism is proposed.

Sphere-forming cells from peripheral cornea demonstrate the ability to repopulate the ocular surface.

BackgroundThe limbus forms the outer rim of the cornea at the corneoscleral junction and harbours a population of stem cells for corneal maintenance. Injuries to the limbus, through disease or accidents such as chemical injuries or burns, may lead to significant visual impairment due to depletion of the native stem cells of the tissue.MethodsSphere-forming cells were isolated from peripheral cornea for potential use as transplantable elements for limbal stem cell repopulation and limbal reconstruction. Immunocytochemistry, live cell imaging and quantitative PCR were used to characterize spheres and elucidate activity post implantation into human cadaveric corneal tissue.ResultsSpheres stained positively for stem cell markers ∆NP63α, ABCG2 and ABCB5 as well as the basal limbal marker and putative niche marker, notch 1. In addition, spheres also stained positively for markers of corneal cells, vimentin, keratin 3, keratocan and laminin, indicating a heterogeneous mix of stromal and epithelial-origin cells. Upon implantation into decellularized corneoscleral tissue, 3D, polarized and radially orientated cell migration with cell proliferation was observed. Cells migrated out from the spheres and repopulated the entire corneal surface over 14 days. Post-implantation analysis revealed qualitative evidence of stem, stromal and epithelial cell markers while quantitative PCR showed a quantitative reduction in keratocan and laminin expression indicative of an enhanced progenitor cell response. Proliferation, quantified by PCNA expression, significantly increased at 4 days subsequently followed by a decrease at day 7 post implantation.ConclusionThese observations suggest great promise for the potential of peripheral corneal spheres as transplantable units for corneal repair, targeting ocular surface regeneration and stem cell repopulation.