Specific Surface Functionalization Research Articles

Investigation on an industrial-feasible approach for measurement and assessment of large-sized micro-structured surfaces based on grayscale matching

Multi-scale micro-structured functional surfaces can enhance the interfacial effect on a component by the microtopological structure, likely through realizing or enhancing its lubrication, drag reduction, noise reducing, sealing, and other specific surface functions. However, the realization of these functions requires high-precision machining quality and the occurrence of any defects on the structured surfaces will possibly influence actual performances of the component. The distribution density, morphology, geometry, configuration feature, and position of those microstructures play a decisive role in affecting the functional performance of the component. It imposes a challenge for rapid and accurate measurement of micro-structured surface particularly at a reasonable large size in industrial-scale production. This article presents an innovative industrial-feasible measurement method for micro-structured surfaces using normalized grayscale matching combined with pyramid search strategy, discriminating-step matching strategy, and sensitive area analysis. The method renders the high matching accuracy and rapid processing capability, which also provides the technical solution for industrial-scale micromanufacturing of large-sized micro-structured surfaces. Well-designed experimental trials are carried out to further evaluate and validate the measurement accuracy and efficiency.

In Situ Characterization of Protein Adsorption onto Nanoparticles by Fluorescence Correlation Spectroscopy.

Nanotechnology holds great promise for applications in many fields including biology and medicine. Unfortunately, the processes occurring at the interface between nanomaterials and living systems are exceedingly complex and not yet well understood, which has significantly hampered the realization of many nanobiotechnology applications. Whenever nanoparticles (NPs) are incorporated by a living organism, a protein adsorption layer, also known as the "protein corona", forms on the NP surface. Accordingly, living organisms interact with protein-coated rather than bare NPs, and their biological responses depend on the nature of the protein corona. In recent years, a wide variety of biophysical techniques have been employed to elucidate mechanistic aspects of NP-protein interactions. In most studies, NPs are immersed in protein or biofluid (e.g., blood serum) solutions and then separated from the liquid for analysis. Because this approach may modify the composition and structure of the protein corona, our group has pioneered the use of fluorescence correlation spectroscopy (FCS) as an in situ technique, capable of examining NP-protein interactions while the NPs are suspended in biological fluids. FCS allows us to measure, with subnanometer precision and as a function of protein concentration, the increase in hydrodynamic radius of the NPs due to protein adsorption. This Account aims at reviewing recent progress in the exploration of NP-protein interactions by using FCS. In vitro FCS studies of the adsorption of important serum proteins onto water-solubilized luminescent NPs always showed a stepwise increase of the NP radius upon protein binding in the form of a binding isotherm, regardless of the type of NP and its specific surface functionalization. This observation indicates formation of a protein monolayer on the NP. Structure-based calculations of protein surface potentials revealed that positively charged patches on the proteins interact electrostatically with negatively charged NP surfaces, and the observed protein layer thickness always matched the known molecular dimensions of the proteins binding in certain orientations. Temperature and NP surface functionalization have also been identified as important parameters controlling protein corona formation. Notably, while the corona formed from a single type of serum protein was reversible, protein adsorption from complex biological media such as blood serum was entirely irreversible. These quantitative in vitro studies are of great relevance to the bio-nano community and especially to researchers developing engineered nanomaterials for biological and biomedical applications. Future efforts will be directed toward elucidating kinetic aspects of protein corona formation and the detailed structure of the adsorbed proteins at the molecular level. To better appreciate the biological responses triggered by NP exposure, more efforts will be devoted to the exploration of the biomolecular corona as it forms on NPs in contact with living cells, tissues, and even entire model organisms. These studies are challenging when performed in a well-controlled and quantitative fashion and rely on the availability of sophisticated analytical tools, particularly, quantitative optical imaging techniques including FCS and related fluctuation methods.

Investigation on an industrial-feasible approach for measurement and assessment of large-sized micro-structured surfaces based on grayscale matching

Multi-scale micro-structured functional surfaces can enhance the interfacial effect on a component by the micro-topological structure, likely through realizing or enhancing its lubrication, drag reduction, noise reducing, sealing, and other specific surface functions. However, the realization of these functions requires high-precision machining quality and the occurrence of any defects on the structured surfaces will possibly influence actual performances of the component. The distribution density, morphology, geometry, configuration feature, and position of those microstructures play a decisive role in affecting the functional performance of the component. It imposes a challenge for rapid and accurate measurement of micro-structured surface particularly at a reasonable large size in industrial-scale production. This article presents an innovative industrial-feasible measurement method for micro-structured surfaces using normalized grayscale matching combined with pyramid search strategy, discriminating-step matching strategy, and sensitive area analysis. The method renders the high matching accuracy and rapid processing capability, which also provides the technical solution for industrial-scale micro-manufacturing of large-sized micro-structured surfaces. Well-designed experimental trials are carried out to further evaluate and validate the measurement accuracy and efficiency.

Modeling the performance limits of novel microcantilever heaters for volatile organic compound detection

We present a theoretical model estimating the performance limits of novel AlGaN/GaN heterostructure based microcantilever heater sensors to perform advanced volatile organic compound (VOC) detection and mixture analysis. Operating without any specific surface functionalization or treatment; these devices utilize the strong surface polarization of AlGaN as well as the unique device geometries, to perform selective detection of analytes based on their latent heat of evaporation and molecular dipole moment over a wide concentration range. The presented model incorporates heat transfer, Joule heating, thermal expansion and evaporative heat loss mechanisms, to predict device behaviors such as temperature profiles and sensing performance limits under various steady-state and transient test conditions. In addition, the versatility of the proposed model enables us to successfully predict the capability of the device to perform mixture analysis, and provides guidelines to further optimize the device properties to achieve a limit of detection in sub-ppm concentration.

Abstract 3238: Imbalance of circulating monocyte subsets in patients with squamous cell carcinoma of the head and neck

Abstract Introduction: Human circulating monocyte is classified as three populations according to CD14 and CD16 expression: CD14+CD16- classical monocytes, CD14+CD16+ intermediate monocytes and CD14dimCD16+ nonclassical monocytes. Recent studies have unveiled the specific surface molecules and functions of each subset; however their dynamics in patients with cancer still remains unclear. In this study, we evaluated the proportions and the expressions of immunological/angiogenic molecules of the monocyte subsets in peripheral circulation in patients with squamous cell carcinoma of the head and neck (SCCHN). Materials and Methods: Peripheral blood mononuclear cells were isolated from 9 patients with SCCHN and age-matched 4 healthy donors. The 3 monocyte subsets were identified according to CD14/CD16 expressions using multi-color flow cytometry. Mean fluorescence intensities of various HLA molecules and angiogenic markers were analyzed. Results: Percentage of CD14+CD16+ intermediate monocyte among total monocyte tended to decrease in SCCHN patients than that in normal donors (p = 0.079). Higher surface expression of immunosuppressive HLA-G molecule on circulating classical (p = 0.045) and intermediate (p = 0.052) monocyte was observed in patients with SCCHN. An immunosuppressive receptor ILT4 showed tendency to increase on nonclassical monocyte (p = 0.061). Moreover, intracytoplasmic level of milk fat globule-EGF factor 8 (MFG-E8) in association with phagocytosis and angiogenesis tended to increase in intermediate (p = 0.064) and nonclassical (p = 0.052) monocytes of SCCHN patients. Discussion and Conclusion: CD16+ intermediate and nonclassical monocytes have been reported as mature, proinflammatory and angiogenic population in periphery. In the present study, we showed possible alternations of these subsets in patients with SCCHN. Furthermore, increasing surface expressions of immunosuppressive molecules HLA-G and ILT4 on circulating monocytes implied immunological deterioration in cancer patients. However the sample size is still small, our preliminary data strongly suggests proportional and functional changes of peripheral monocyte subsets in SCCHN patients. Further analyses in more patients are currently underway. Citation Format: Koichi Sakakura, Hideyuki Takahashi, Sei-ichiro Motegi, Kazuaki Chikamatsu. Imbalance of circulating monocyte subsets in patients with squamous cell carcinoma of the head and neck. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3238.

Smart Biodegradable Nanoparticulate Materials: Poly-lactide-co-glycolide Functionalization with Selected Peptides

Background: Smart nanoparticulate materials, namely tailored nanoparticles (NPs) with specific surface functionality, have recently attracted attention as useful tool for time- and site-specific drug delivery. Specifically, polymeric nanoparticles (NPs) can be chemically functionalized with different chemical entities, i.e. peptides, that selectively recognize biological substrates in vivo and target drug release. Divergent and very complex strategies can be pursued in order to obtain peptidedecorated NPs. Methods: A simple method was suggested for direct functionalization of poly-lactide-co-glicolide (PLGA) with small peptides. A solid-phase peptide synthesis was used to obtain a dodecapeptide (GE11) and a smaller tetrapeptide (FQPV). FQPV- and GE11-PLGA conjugates were obtained by optimized carbodiimide chemistry. Nanoprecipitation and solvent extraction/evaporation methods were purpose-built in order to prepare FQPV-PLGA NPs. NPs were characterized in terms of size, surface charge and adsorbed peptide amount; ex-vivo cytotoxicity studies were performed on FQPV-PLA NPs using adult fibroblasts. Results: Custom GE11, recently known as efficient Epidermal Growth Factor Receptor targeting agent, and FQPV, used as model peptide, were synthesized by solid-phase peptide synthesis achieving good purity (95%) and satisfactory process yields (70-85%). Then, FQPV- and GE11-PLGA conjugates were obtained by optimized carbodiimide chemistry achieving an high degree of functionalization (> 85%). Aware of different physico-chemical properties of peptide-PLGA conjugates with respect to plain PLGA, two different NPs preparation techniques, nanoprecipitation and solvent extraction/ evaporation methods, were purpose-built in order to prepare FQPV-PLGA NPs. Both methods revealed suitable to obtain NPs with proper dimensions for the parenteral administration (< 250nm), narrow size distribution (P.I. about 0.1), good morphological features and negative charge (about –20mV). A peptide adsorption protocol onto NPs was considered as additional strategy to increase peptide expression on NPs surface aimed at improving the targeting effectiveness. A Design of Experiment approach (DoE) has been successfully applied to the more versatile solvent extraction/ evaporation method in order to systematically highlight the influence of process parameters (organic solvent mixture, PVA concentration and polymeric solution volume) on NPs sizes. Conclusion: PLGA was successfully functionalized with two different peptides, FQPV and GE11, following the a versatile and simple carbodiimmide chemistry without further modifying polymer and/or peptide structure. Both nanoprecipitation and solvent extraction/evaporation NPs preparation methods were properly optimized in order to obtain peptide-PLGA based NPs and they can be alternatively selected according to solubility properties of both peptide-polymer conjugate and drug intended for encapsulation. Peptide adsorption on preformed PLGA NPs could be efficiently used to increase peptide expression on NPs surface thus improving cellular recognition in case of active targeting. Preliminary cytocompatibility evaluation of the selected peptide-PLGA based nanoparticulate materials shows a potential feasibility of the set-up synthetic procedures and NPs preparation methods for pharmaceutical purposes. Keywords: FQPV-PLGA nanoparticles, GE11-PLGA nanoparticles, peptide synthesis, peptide-PLGA conjugates, peptidepolymer conjugate synthesis, PLGA nanoparticles, smart PLGA nanomaterials.

Free-Radical-Induced Grafting from Plasma Polymer Surfaces.

With the advances in science and engineering in the second part of the 20th century, emerging plasma-based technologies continuously find increasing applications in the domain of polymer chemistry, among others. Plasma technologies are predominantly used in two different ways: for the treatment of polymer substrates by a reactive or inert gas aiming at a specific surface functionalization or for the synthesis of a plasma polymer with a unique set of properties from an organic or mixed organic-inorganic precursor. Plasma polymer films (PPFs), often deposited by plasma-enhanced chemical vapor deposition (PECVD), currently attract a great deal of attention. Such films are widely used in various fields for the coating of solid substrates, including membranes, semiconductors, metals, textiles, and polymers, because of a combination of interesting properties such as excellent adhesion, highly cross-linked structures, and the possibility of tuning properties by simply varying the precursor and/or the synthesis parameters. Among the many appealing features of plasma-synthesized and -treated polymers, a highly reactive surface, rich in free radicals arising from deposition/treatment specifics, offers a particular advantage. When handled carefully, these reactive free radicals open doors to the controllable surface functionalization of materials without affecting their bulk properties. The goal of this review is to illustrate the increasing application of plasma-based technologies for tuning the surface properties of polymers, principally through free-radical chemistry.

Magnetogenetic Manipulation of Intracellular Signaling using Ferritin Nanoparticles

Controlling the spatio-temporal organization of biomolecules inside living cells is a major prerequisite for deciphering mechanisms governing cell signaling regulation.We have implemented a new method to induce a highly specific and local perturbation of signaling pathways inside living cells: Magnetogenetics. It is based on the use of biofunctionalized magnetic nanoparticles (f-MNPs) in order to induce and maintain protein gradients inside living cells.In a previous work, we have shown that 500nm MNPs functionalized in situ with active proteins are able to create a precise point-like perturbations at the cell periphery.Yet, the limitation of this approach was the need to use MNPs with large diameter. First, they were difficult to deliver into the cytoplasm and second, their motion was strongly constrained by intracellular obstacles. Moreover, subcellular gradients of active protein, as required for many spatially regulated processes, could not be recapitulated with 500nm MNPs, which usually clustered at the cell periphery.In the present work we aimed at advancing magnetogenetic tools by using much smaller functionalized MNPs in order to enable rapid and facilitated control of intracellular protein gradient. We developed a new technology based on the synthesis and purification of superparamagnetic GFP-ferritin-based monodisperse nanoparticles, which surface properties where tailored to ensure unhindered mobility in the cytosol and specific in situ capturing of target proteins.By nanobody anti-GFP targeting system virtually any construct encoding anti-GFP nanobody can be targeted. These MNPs with a diameter of 12 nm could be rapidly relocalized in living cells by exploiting biased diffusion at weak magnetic forces in the femto-Newton range.By combining rapid and highly specific surface functionalization with efficient delivery into the cytosplasm, we here present a comprehensive technology for controlling intracellular protein signaling with a temporal resolution of a few tens of seconds.

Highly selective colorimetric sensing of Hg2+ ions by label free AuNPs in aqueous medium across wide pH range

Highly selective colorimetric sensing of Hg2+ ions have been demonstrated in aqueous medium across wide pH range (2.0–10.0) using AuNPs without any specific surface functionality or size and morphological control. AuNPs stabilized with different capping agents such as PEG, PSS, T-80, PVA, SDS, PVP were synthesized using ascorbic acid reducing agent and characterized by absorption spectroscopy and high-resolution transmission electron microscope (HR-TEM). Interestingly, Hg2+ addition into AuNPs exhibited highly selective colour and absorption change. The controlled studies indicate that ascorbic acid might play a significant role by converting Hg2+ to metallic Hg that promotes amalgamation with AuNPs. The concentration dependent studies indicate that the synthesized AuNPs can detect Hg2+ ions up to ppb (10−9M) level. Importantly, T-80- and PSS-AuNPs showed selective sensing of Hg2+ across wide pH range (2.0–10.0). The recovery and interference studies demonstrate the good selectivity of AuNPs for Hg2+ ions in presence of other metal cations.

Oxygen reduction on chemically heterogeneous iron-containing nanoporous carbon: The effects of specific surface functionalities

Synthetic activated carbon containing iron and sulfur heteroatoms, obtained from polystyrene sulfonic acid-based organic salt, and commercial wood-based carbon containing phosphorous were tested as catalysts for oxygen reduction reactions. The carbons were characterized using adsorption of nitrogen, TA-MS, FTIR, XRD, XPS, potentiometric titration, SEM/EDX, and HR-TEM microscopy. The introduction of iron to the carbon resulted a marked electrocatalytic activity for oxygen reduction reaction (ORR) in alkaline medium. A current density was higher than that on commonly used platinum modified carbon and number of electron transfer (∼4e−) indicated a high ORR efficiency. This was accompanied by a high tolerance to methanol oxidation and a good long-term stability after 1500 potential cycles. The extensive surface characterization indicated the fast O2 adsorption and charge transfer was owed to the surface hydrophobicity, small pores and conductivity. The synergistic effect of porosity and specific iron species containing sulfur lead to high ORR activity and high kinetic current densities.

Functionalisation and immobilisation of an Au(110) surface via uracil and 2-thiouracil anchored layer.

We study surface functionalisation by uracil and 2-thiouracil, and immobilisation of several DNA moieties on functionalised gold surfaces. The combination of X-ray photoelectron and near-edge X-ray absorption spectroscopy allowed us to obtain a complete understanding of complex interfacial processes, starting from adsorption of biomolecules onto the metallic surface and progressing towards a specific surface functionality for interactions with other biologically related adsorbates. Au(110) surfaces were functionalised by deposition of uracil and 2-thiouracil molecules under vacuum conditions, and then tested for their selectivity by immobilisation of different DNA moieties deposited from aqueous solutions. We observed that adenine, adenosine, and RNA polymer (polyadenylic acid) from saturated solutions were immobilized successfully on the 2-thiouracil, but those from dilute (1%) solutions were not. However, cytosine failed to adsorb even from saturated solution. The chemical states of the biologically related adsorbates were investigated and the geometrical orientation of uracil and 2-thiouracil on the Au(110) surface was determined using both spectroscopic techniques.

Electrospun poly(vinylidene fluoride) copolymer/octahydroxy-polyhedral oligomeric silsesquioxane nanofibrous mats as ionic liquid host: enhanced salt dissociation and its function in electrochromic device

Electrospun polymer nanofibrous mats loaded with ionic liquids (ILs) and lithium salts are promising non-volatile electrolytes owing to their high ionic conductivities. However, the large cations of ILs are difficult to diffuse into solid electrodes, whereas the lithium ions in ILs tend to form anionic complexes with the IL anions, reducing the number of free lithium ions. To address these issues, octa(3-hydroxy-3-methylbutyldimethylsiloxy) polyhedral oligomeric silsesquioxane (POSS-OH), which has large specific surface area and functionality number, is incorporated into electrospun poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) nanofibrous mats, and the mats are used to host LiClO4/1-butyl-3-methylimidazolium tetrafluoroborate (BMIM+BF4−). It is found that POSS-OH can significantly increase both ionic conductivity and lithium transference number of the electrolytes owing to the Lewis acid-base interactions of POSS-OH with ClO4− and BF4−. The electrochromic device using the hybrid mat (with 5 wt% POSS-OH) loaded with LiClO4/BMIM+BF4− as the electrolyte shows significantly improved transmittance contrast and switching time, as a result of increased number of free lithium ions.

Free radical generation and concentration in a plasma polymer: the effect of aromaticity.

Plasma polymer films (PPF) have increasing applications in many fields due to the unique combination of properties of this class of materials. Among notable features arising from the specifics of plasma polymerization synthesis, a high surface reactivity can be advantageously used when exploited carefully. It is related to the presence of free radicals generated during the deposition process through manifold molecular bond scissions in the energetic plasma environment. In ambient atmosphere, these radicals undergo autoxidation reactions resulting in undesired polymer aging. However, when the reactivity of surface radicals is preserved and they are put in direct contact with a chemical group of interest, a specific surface functionalization or grafting of polymeric chains can be achieved. Therefore, the control of the surface free radical density of a plasma polymer is crucially important for a successful grafting. The present investigation focuses on the influence of the hydrocarbon precursor type, aromatic vs aliphatic, on the generation and concentration of free radicals on the surface of the PPF. Benzene and cyclohexane were chosen as model precursors. First, in situ FTIR analysis of the plasma phase supplemented by density functional theory calculations allowed the main fragmentation routes of precursor molecules in the discharge to be identified as a function of energy input. Using nitric oxide (NO) chemical labeling in combination with X-ray photoelectron spectroscopy analysis, a quantitative evaluation of concentration of surface free radicals as a function of input power has been assessed for both precursors. Different evolutions of the surface free radical density for the benzene- and cyclohexane-based PPF, namely, a continuous increase versus stabilization to a plateau, are attributed to different plasma polymerization mechanisms and resulting structures as illustrated by PPF characterization findings. The control of surface free radical density can be achieved through the stabilization of radicals due to the proximity of incorporated aromatic rings. Aging tests highlighted the inevitable random oxidation of plasma polymers upon exposure to air and the necessity of free radical preservation for a controlled surface functionalization.

Adhesion and differentiation of human mesenchymal stem cells on plasma-functionalized graphenes with different feeding gases

Surface functionalisation of graphene layer has been investigated to improve the efficiencies in bio-applications such as stem cell differentiation or protein sensing. Plasma treatment can induce various functionalities on graphene surface simply by changing feeding gas. In this study, the surface chemistry of graphene is modified by plasma treatment using three different feeding gases of H2, N2, and O2. The effects of differential functionalisation are examined by the adsorption of fibronectin and the adhesion, proliferation, and differentiation of human mesenchymal stem cells. Fibronection adsorption is enhanced on the N2 plasma-treated graphene, but it is not clear on the others. hMSCs adhesion is broadened on all of the plasma-treated graphene substrates, especially on the N2 plasma-treated one. H2 plasma treatment enhances cell proliferation and osteogenic differentiation, and N2 and O2 plasma treatments show a tendency of heterogeneous differentiation to osteoblasts and myoblasts. Different responses of stem cell adhesion, proliferation, and differentiation depending on the plasma-treated graphene surface indicate the importance of highly specific surface functionality in stem cell engineering.

Synthesis and supercapacitor application of nanoporous carbon by the direct carbonization of aluminium salicylate coordination polymer

Flake-like nanoporous carbon has been synthesized by the direct carbonization of aluminium salicylate coordination polymer that serves as hard templates and carbon sources. It reveals that the carbonization temperature plays a crucial role in the formation of nanoporous carbon. The correlation between specific surface areas, pore structures, surface functionalities and capacitive performances are investigated. The nanoporous carbon synthesized at 900°C, named as carbon-900, exhibits high surface area of 1162m2g−1 and large total pore volume of 0.80cm3g−1. The electrochemical behaviors are measured in a three-electrode system. In details, high specific capacitance of 220.0Fg−1 is achieved at a current density of 0.5Ag−1, whereas it also delivers high energy density of 30.5Whkg−1, and long cycle stability (∼88.57% retention after 3000cycles).

Anatase–silica composite aerogels: a nanoparticle-based approach

Herein we present the synthesis of anatase–silica aerogels based on the controlled gelation of preformed nanoparticle mixtures. The monolithic aerogels with macroscopic dimensions show large specific surface areas, and high and uniform porosities. The major advantage of such a particle-based approach is the great flexibility in pre-defining the compositional and structural features of the final aerogels before the gelation process by fine-tuning the properties of the titania and silica building blocks (e.g., size, composition and crystallinity) and their relative ratio in the dispersion. Specific surface functionalization enables control over the interaction between the nanoparticles and thus over their distribution in the aerogel. Positively charged titania nanoparticles are co-assembled with negatively charged Stoeber particles, resulting in a binary aerogel with a crystalline anatase and amorphous silica framework directly after supercritical drying without any calcination step. Titania–silica aerogels combine the photocatalytic activity of the anatase nanoparticles with the extensive silica chemistry available for silica surface functionalization.

Reduction Mechanisms of Ethylene Carbonate on Si Anodes of Lithium-Ion Batteries: Effects of Degree of Lithiation and Nature of Exposed Surface

Ab initio molecular dynamics simulations are used to identify mechanisms of reduction of ethylene carbonate on Si surfaces at various degrees of lithiation, where the low-coordinated surface Si atoms are saturated with O, OH, or H functional groups. The lowest Si content surfaces are represented by quasi-amorphous LiSi4 and LiSi2; intermediate lithiation is given by LiSi crystalline facets, and the highest Li content is studied through Li13Si4 surfaces. It is found that ethylene carbonate (EC) reduction mechanisms depend significantly on the degree of lithiation of the surface. On LiSi surfaces EC is reduced according to two different two-electron mechanisms (one simultaneous and one sequential), which are independent of specific surface functionalization or nature of exposed facets. On the less lithiated surfaces, the simultaneous two-electron reduction is found more frequently. In that mechanism, the EC reduction is initiated by the formation of a C-Si bond that allows adsorption of the intact molecule to the surface and is followed by electron transfer and ring-opening. Strongly lithiated Li13Si4 surfaces are found to be highly reactive. Reduction of adsorbed EC molecules occurs via a four-electron mechanism yielding as reduction products CO(2-) and O(C2H4)O(2-). Direct transfer of two electrons to EC molecules in liquid phase is also possible, resulting in the presence of O(C2H4)OCO(2-) anions in the liquid phase.

Preparation and electrochemical performance of heteroatom-enriched electrospun carbon nanofibers from melamine formaldehyde resin

Melamine formaldehyde resin was used to prepare heteroatom-enriched carbon nanofibers by electrospinning for the first time. The melamine formaldehyde resin-based carbon fibers without any activation treatment showed a moderate specific surface area ranging from 130 to 479m2/g and rich surface functionalities (2.56–5.34wt.% nitrogen and 10.39–11.29wt.% oxygen). Both the specific surface area and surface functionality greatly depended on the carbonization temperature. The capacitive performance was evaluated in 6M KOH aqueous solution. The electrochemically active surface functionalities played an important role in improving the surface capacitance of the electrodes. The sample carbonized at 600°C showed the highest specific surface capacitance of 1.4F/m2, which was attributed to the most active functionalities (10.69wt.% of N and O). In addition, the sample carbonized at 750°C exhibited the highest specific capacitance of 206F/g.

Volume labeling with Alexa Fluor dyes and surface functionalization of highly sensitive fluorescent silica (SiO2) nanoparticles

A new synthesis approach is described that allows the direct incorporation of fluorescent labels into the volume or body of SiO2 nanoparticles. In this process, fluorescent Alexa Fluor dyes with different emission wavelengths were covalently incorporated into the SiO2 nanoparticles during their formation by the hydrolysis of tetraethoxysilane. The dye molecules were homogeneously distributed throughout the SiO2 nanoparticles. The quantum yields of the Alexa Fluor volume-labeled SiO2 nanoparticles were much higher than nanoparticles labeled using conventional organic dyes. The size of the resulting nanoparticles was controlled using microemulsion reaction media with sizes in the range of 20-100 nm and a polydispersity of <15%. In comparison with conventional surface tagged particles created by post-synthesis modification, this process maintains the physical and surface chemical properties that have the most pronounced effect on colloidal stability and interactions with their surroundings. These volume-labeled nanoparticles have proven to be extremely robust, showing excellent signal strength, negligible photobleaching, and minimal loss of functional organic components. The native or "free" surface of the volume-labeled particles can be altered to achieve a specific surface functionality without altering fluorescence. Their utility was demonstrated for visualizing the association of surface-modified fluorescent particles with cultured macrophages. Differences in particle agglomeration and cell association were clearly associated with differences in observed nanoparticle toxicity. The capacity to maintain particle fluorescence while making significant changes to surface chemistry makes these particles extremely versatile and useful for studies of particle agglomeration, uptake, and transport in environmental and biological systems.

Validation processes of protein biomarkers in serum--a cross platform comparison.

Due to insufficient biomarker validation and poor performances in diagnostic assays, the candidate biomarker verification process has to be improved. Multi-analyte immunoassays are the tool of choice for the identification and detailed validation of protein biomarkers in serum. The process of identification and validation of serum biomarkers, as well as their implementation in diagnostic routine requires an application of independent immunoassay platforms with the possibility of high-throughput. This review will focus on three main multi-analyte immunoassay platforms: planar microarrays, multiplex bead systems and, array-based surface plasmon resonance (SPR) chips. Recent developments of each platform will be discussed for application in clinical proteomics, principles, detection methods, and performance strength. The requirements for specific surface functionalization of assay platforms are continuously increasing. The reasons for this increase is the demand for highly sensitive assays, as well as the reduction of non-specific adsorption from complex samples, and with it high signal-to-noise-ratios. To achieve this, different support materials were adapted to the immobilized biomarker/ligand, allowing a high binding capacity and immobilization efficiency. In the case of immunoassays, the immobilized ligands are proteins, antibodies or peptides, which exhibit a diversity of chemical properties (acidic/alkaline; hydrophobic/hydrophilic; secondary or tertiary structure/linear). Consequently it is more challenging to develop immobilization strategies necessary to ensure a homogenous covered surface and reliable assay in comparison to DNA immobilization. New developments concerning material support for each platform are discussed especially with regard to increase the immobilization efficiency and reducing the non-specific adsorption from complex samples like serum and cell lysates.