Modification of monomolecular self-assembled films by nitrogen-oxygen plasma.

The modification of octadecanethiolate self-assembled monolayers on Au and Ag by nitrogen-oxygen downstream microwave plasma with variable oxygen content (up to 1%) has been studied by synchrotron-based high-resolution X-ray photoelectron spectroscopy. The primary processes were dehydrogenation, desorption of hydrocarbon and sulfur-containing species, and the oxidation of the alkyl matrix and headgroup-substrate interface. The exact character and the rates of the plasma-induced changes were found to be dependent on the substrate and plasma composition, with the processes in the aliphatic matrix and headgroup-substrate interface being mostly decoupled. In particular, the rates of all major plasma-induced processes were found to be directly proportional to the oxygen content in the plasma, which can be, thus, considered as a measure of the plasma reactivity. Along with the character of the observed changes, exhibiting a clear dominance of the oxidative processes, this suggests that the major effect of the oxygen-nitrogen downstream microwave plasma is provided by reactive oxygen-derived species in the downstream region, viz. long-living oxygen radicals and metastable species.

Proteomic profiling of erythrocyte proteins by proteolytic digestion chip and identification using two-dimensional electrospray ionization tandem mass spectrometry.

Self-assembled monolayers (SAMs) on coinage metal provide versatile modeling systems for studies of interfacial electron transfer, biological interactions, molecular recognition, and other interfacial phenomena. The bonding of enzyme to SAMs of alkanethiols onto gold surfaces is exploited to produce an enzyme chip. In this work, the attachment of trypsin to a SAMs surface of 11-mercaptoundecanoic acid was achieved using water soluble N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide as coupling agent. A two-dimensional liquid-phase separation scheme coupled with mass spectrometry is presented for proteomic analysis of erythrocyte proteins. The application of proteomics, particularly with reference to analysis of proteins, will be described. Surface analyses have revealed that the X-ray Photoelectron Spectroscopy (XPS) C1s and N1s core levels illustrate the immobilization of trypsin. These data are also in good agreement with Fourier Transformed Infrared Reflection-Attenuated Total Reflection (FTIR-ATR) spectra for the peaks at Amide I and Amide II. Using two-dimensional nano-high performance liquid chromatography electrospray ionization tandem mass spectrometry (2D nano-HPLC-ESI-MS/MS) system observations, analytical results have demonstrated the erythrocyte proteins digestion of the immobilized trypsin on the functionalized SAMs surface. For such surfaces, it also shows the enzyme digestion ability of the immobilized trypsin. The experiment results revealed the identification of 272 proteins from erythrocyte protein sample. The terminal groups of the SAMs structure can be further functionalized with biomolecules or antibodies to develop surface-base diagnostics, biosensors, or biomaterials.

Characterization of trypsin immobilized on the functionable alkylthiolate self-assembled monolayers: a preliminary application for trypsin digestion chip on protein identification using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Self-assembled monolayers (SAMs) on coinage metal provide versatile modeling systems for studies of interfacial electron transfer, biological interactions, molecular recognition and other interfacial phenomena. Recently the bonding of enzyme to SAMs of alkanethiols onto Au electrode surfaces was exploited to produce a bio-sensing system. In this work, the attachment of trypsin to a SAMs surface of 11-mercaptoundecanoic acid was achieved using water soluble N-ethyl-N '-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide as coupling agent. The thickness of SAMs was determined by optical ellipsometer; contact angles of the modified Au surfaces were measured in air using a goniometer. The Second Harmony Generation data displays the last few percents of the alkylthiol molecules adsorbed and produced the complete monolayer by inducing the transition from a high number of gauche defects to an all-trans conformation. Using X-ray Photoelectron Spectroscopy (XPS) and Fourier-Transformed Infrared Reflection-Absorption and Attenuated Total Reflection Spectroscopes (FTIR-RAS and ATR), we examined the chemical structures of samples with different treatments. By matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), we demonstrated the digestion of bovine serum albumin (BSA) on the trypsin-immobilized SAMs surface. Experimental results have revealed that the XPS C1s core levels at 286.3 and 286.5 eV (Amine bond), 288.1 eV (Amide bond) and 289.3 eV (Carboxylic acid) illustrate the immobilization of trypsin. These data were also in good agreement with FTIR-ATR spectra for the peaks valued at 1659.4 cm(-1) (Amide I) and 1546.6 cm(-1) (Amide II). Using MALDI-TOF MS observations, analytical results have demonstrated the BSA digestion of the immobilized trypsin on the functionalized SAMs surface. For such surfaces, BSA was digested on the trypsin-immobilized SAMs surface, which shows the enzyme digestion ability of the immobilized trypsin. The terminal groups of the SAMs structure can be further functionalized with biomolecules or antibodies to develop surface-base diagnostics, biosensors, or biomaterials.

Modification of aliphatic self-assembled monolayers by free-radical-dominant plasma: the role of the plasma composition.

Modification of octadecanethiolate self-assembled monolayers on Au by nitrogen-oxygen or argon-oxygen downstream microwave plasma with a low oxygen content (estimated below several percent) has been studied by synchrotron-based high-resolution X-ray photoelectron spectroscopy and water contact angle measurements. For both types of plasma, the primary processes were found to be the loss of conformational and orientational order and the oxidation of the alkyl matrix and headgroup-substrate interface. At the same time, the film modification occurred much faster and with different intermediates for the nitrogen plasma than for the argon plasma. The reasons for these differences are considered in terms of the different reactivities and different efficiencies of the energy transfer between the plasma constituents in these two types of plasma.

Proteomic profiling of platelet proteins by trypsin immobilized self-assembled monolayers digestion chip and protein identification using electrospray ionization tandem mass spectrometry.

Self-assembled monolayers (SAMs) on coinage metal provide versatile modeling systems for studies of interfacial electron transfer, biological interactions, molecular recognition, and other interfacial phenomena. Recently, the bonding of enzyme to SAMs of alkanethiols onto Au electrode surfaces was exploited to produce a bio-sensing system. In this work, the attachment of trypsin to a SAMs surface of 11-mercaptoundecanoic acid was achieved using water soluble 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysulfosuccinimide as coupling agent. Experimental results have revealed that the X-ray Photoelectron Spectroscopy (XPS) C1s core levels at 286.3 and 286.5 eV (C with N), 288.1 eV (amide bond), and 289.3 eV (carboxyl) illustrate the immobilization of trypsin. These data were also in good agreement with Fourier-Transformed Infrared Reflection-Attenuated Total Reflection (FTIR-ATR) spectra for the peaks valued at 1659.4 cm(-1) (amide I) and 1546.6 cm(-1) (amide II). Using electrospray ionization tandem mass spectrometry (ESI-MS/MS) observations, analytical results have demonstrated the platelet proteins digestion of the immobilized trypsin on the functionalized SAMs surface. For such surfaces, platelet proteins were digested on the trypsin-immobilized SAMs surface, which shows the enzyme digestion ability of the immobilized trypsin. The terminal groups of the SAMs structure can be further functionalized with biomolecules or antibodies to develop surface-base diagnostics, biosensors, or biomaterials.

Chemisorption and reaction characteristics of methyl radicals on Cu(110).

Methyl radicals are generated by pyrolysis of azomethane, and the condition for achieving neat adsorption on Cu(110) is described for studying their chemisorption and reaction characteristics. The radical-surface system is examined by X-ray photoemission spectroscopy, ultraviolet photoemission spectroscopy, temperature-programmed desorption, low-energy electron diffraction (LEED), and high-resolution electron energy loss spectroscopy under ultrahigh vacuum conditions. It is observed that a small fraction of impinging CH3 radicals decompose into methylene possibly on surface defect sites. This type of CH2 radical has no apparent effect on CH3(ads) surface chemistry initiated by dehydrogenation to form active CH2(ads) followed by chain reactions to yield high-mass alkyl products. All thermal desorption products, such as H2, CH4, C2H4, C2H6, and C3H6, are detected with a single desorption peak near 475 K. The product yields increase with surface coverage until saturation corresponding to 0.50 monolayer of CH3(ads). The mass distribution is, however, invariant with initial CH3(ads) coverage, and all desorbed species exhibit first-order reaction kinetics. LEED measurement reveals a c(2 x 2) adsorbate structure independent of the amount of gaseous exposure. This strongly suggests that the radicals aggregate into close-packed two-dimensional islands at any exposure. The islanding behavior can be correlated with the reaction kinetics and is deemed to be essential for the chain propagation reactions. Some relevant aspects of the CH3/Cu(111) system are also presented. The new results are compared with those of prior studies employing methyl halides as radical sources. Major differences are found in the product distribution and desorption kinetics, and these are attributed to the influence of surface halogen atoms present in those earlier investigations.

Assessment and characterization of degradation effect for the varied degrees of ultra-violet radiation onto the collagen-bonded polypropylene non-woven fabric surfaces.

Exposure to ultra-violet (UV)-C radiation is a frequently used method to prevent bacteria from invasion of blood-contact biomedical products. Potential damage induced by UV radiation to collagen is of concern due to the decay of bioactivity, considerably correlated with structural alterations. Our current investigation studies the collagen-bonded non-woven polypropylene (PP) fabric surface. In this experiment, antenna-coupling microwave plasma is utilized to activate PP fabric and then the sample is grafted with acrylic acid (AAc). Type III collagen is immobilized by using water soluble 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide as coupling agent. The collagen-bonded samples with sample temperature ca. 4 degrees C are then exposed to UV-254nm radiation for different time intervals. By using fourier-transformed infrared with attenuated total reflection (FTIR-ATR) and XPS (X-ray photoelectron spectroscopy), we examine the chemical structures of samples with different treatments. Coomassie brilliant blue G250 method is utilized to quantify the immobilized collagen on the PP fabric surfaces. Blood-clotting effects are evaluated by activated partial thromboplastin time, thrombin time, and fibrinogen concentration tests. By means of cell counter and scanning electron microscopy we count red blood cells and platelets adhesion in the modified porous matrix. Our experimental results have demonstrated that with pAAc-grafting of ca. 173 microg cm(-2) and immobilized collagen of 80.5+/-4.7 microg cm(-2), for human plasma incubated samples of various intervals of UV-254 nm radiation, fibrinogen concentration decreases in human plasma, while platelets and red blood cells adhesions increase before UV radiation. However, the required time for thrombination shows significant change for UV radiation exposure of less than 20 h (alpha = 0.05). The decay of bioactivity for the UV-irradiated, collagen-bonded surfaces is thus evaluated. Surface analyses indicate that the decrease of R-COOH (derivated from grafted-pAAc or de-carboxylation of collagen), amides degradation (broken-NH), and phenylalanine scission (terminated by -OH, tyrosine formation) may gradually damage collagen by increasing the intervals of UV radiation. These effects considerably influence the bioactivity of the collagen-bonded fabric. The XPS measurements of C 1s core levels at 288.4 eV (O = C-NH) and at 289.1 eV (O = C-O) illustrate significant decreases of intensity after radiation time ca. 44 h. It is clear that UV-254 nm radiation exposure for ca. 20 h has the potential impact to moderate the bioactivities of collagen and therefore act as a vital factor to accelerate biodegradation.

Anticoagulant activity of immobilized heparin on the polypropylene nonwoven fabric surface depending upon the pH of processing environment.

Antenna coupling microwave plasma enables a highly oxidative treatment of the outmost surface of polypropylene (PP) nonwoven fabric within a short time period. Subsequently, grafting copolymerization with acrylic acid (AAc) makes the plasma-treated fabric durably hydrophilic and excellent in water absorbency. With high grafting density and strong water affinity, the pAAc-grafted support greatly becomes feasible as an intensive absorbent and as a support to promote heparin immobilization through amide bonds. For heparin immobilized in acidic condition, the carbonate groups of the molecule tend to dissolve and passive encapsulation of the molecule prevents its functional groups from bonding with the carboxylic acid of pAAc. This effect leads to inhibit the immobilization process and consequently reduces the quantity as well as the bioactivity of the immobilized heparin. In alkaline processing environment, the oxidized uronic acid residues in heparin-related glycans are presumably cleaved and the removal of some oxidized residuals before immobilization process is likely to reduce the chain length of heparin. In the latter case, anticoagulant Factors X and XII, but not thrombin, are unaffected. Anticoagulant activity test using activated partial thromboplastin time (aPTT) is more sensitive in assessing heparin-immobilized surfaces, since it corresponds to Factor X and initiates the inhibition of Factor XII and thrombin. Likewise, platelets adhesion on the surfaces decreases as the process shifted from acidic to alkaline condition, whereas the hydrophilic character of the grafted pAAc markedly contributes to extend physical insertion of platelets. The immobilized heparin has a great part of original bioactivity, depending on the pH of the processing environment and the immobilized quantity. Relative bioactivity based upon aPTT tests is partially held longer than 90 days for the sample prepared in the alkaline or neutral environment.