Latex piezoelectric immunoassay: Effect of interfacial properties

Latex piezoelectric immunoassay is a technique for detecting agglutination of antibody- or antigen-bearing latex by an immunoreaction using a piezoelectric quartz crystal; the agglutination decreases the oscillation frequency of the crystal. This is advantageous in that immobilization of antibody or antigen on the crystal surface is unnecessary. In this report, different kinds of chemical functional groups were immobilized on the electrode surface, allowing us to consider the effect of interfacial structure on the frequency change. Electrode modifications such as self-assembly of alkanethiol and aminoalkoxysilane monolayers, and polyethylenimine-glutaraldehyde coating as well as plasma treatment were examined. The sensitivity of the system was found to imitate the interfacial properties so that modification of the electrode surface could improve the response. Among the methods examined for this electrode surface modification, the polyethylenimine-glutaraldehyde modification had the advantages of high reproducibility, fast operation and simplicity. It was also suggested that the frequency change originated primarily from the immunoreaction at the interface.     

Detection of bacterial contaminated milk by means of a quartz crystal microbalance based electronic nose

Headspace analysis by means of sensor arrays has been successfully applied to a wide range of qualitative applications. In this study, a six element array of coated Quartz Crystal Microbalance (QCM) sensors was used for the headspace analysis of milk volatiles. The sensors were exposed to uncontaminated samples of milk and samples contaminated with Pseudomonas fragi (Ps. fragi) or Escherichia coli (E. coli). Principal component analysis (PCA) was used to analyse the sensor array responses. No discrimination between uncontaminated milk samples and those contaminated with Ps. fragi was observed. This can be explained by Ps. fragi being a poor fermenter of milk. However, encouraging results were found for the discrimination between the milk samples and those contaminated with E. coli.This revised version was published online in November 2005 with corrections to the Cover Date.     

Carbon dioxide, ethylene and water vapor sorption in poly(lactic acid)

The objective of this work is to study the gas/vapor sorption in poly(lactic acid) (PLA) with a 98:2 (l:d) ratio using a quartz crystal microbalance (QCM). For that purpose, the sorption of carbon dioxide, ethylene and water vapor in poly(lactic acid) (PLA) with a 98:2 (l:d) ratio, in temperature range from 283 to 313 K and up to atmospheric pressure was measured. The measured isotherms indicate that the sorption mechanism is sorbate dependent, since carbon dioxide and ethylene seem to have predominantly a Langmuir type of mechanism while water is predominantly Henry controlled. Two temperature protocols were used and only ethylene sorption is affected by them. Comparisons with previously measured gas sorption data in PLA 80:20 using the same temperature protocol indicate that the l:d ratio plays a dominant role in gas/vapor sorption in PLA.     

Simultaneous gas chromatographic determination of aliphatic C2−C20 n-carboxylic acids and their methyl esters using SE-30 and OV-351 quartz capillary columns

Summary Simultaneous determination of aliphatic C₂–C₂₀ carboxylic acids and their methyl esters was carried out using SE-30 and OV-351 quartz capillary columns with temperature programming. Complete resolution of all 36 components was achieved. On SE-30 the methyl ester and the corresponding free acid are eluted in turn, whereas on OV-351 acetic acid eluted after methyl octanoate, after which the C_n methyl ester and C_n-6 carboxylic acid (n>9) are eluted one after the other. A non-polar SE-30 column is better for long-chain acids giving sharp peaks without tailing, the analysis time of the mixture being less than 16 minutes. The weight response correction factors for compounds under optimum operating conditions are given.     

萘磺酸盐与β-环糊精衍生物的包结行为

以自组装方式在石英晶体谐振器的金电极表面修饰末端含巯基的β 环糊精衍生物（β CDd）,用石英晶体微天平（QCM）在线监测α 、β 萘磺酸盐与之发生包结反应的过程,探讨了温度、浓度、取代基位置对包结反应稳定常数Kin和速率常数ka的影响.从理论上推导并通过实验验证了Kin和ka所遵从的关系式.结果表明：所形成的包结配合物中β CDd与萘磺酸盐的化学计量均为1:1;包结配位反应过程符合Langmuir吸附模型;取代基在萘环上的位置对Kin和ka有很大影响,说明不同取代位置的萘磺酸盐与β CDd的包结行为存在明显差异.     

Label-free screening of bio-molecular interactions

The majority of techniques currently employed to interrogate a biomolecular interaction require some type of radio- or enzymatic- or fluorescent-labelling to report the binding event. However, there is an increasing awareness of novel techniques that do not require labelling of the ligand or the receptor, and that allow virtually any complex to be screened with minimal assay development. This review focuses on three major label-free screening platforms: surface plasmon resonance biosensors, acoustic biosensors, and calorimetric biosensors. Scientists in both academia and industry are using biosensors in areas that encompass almost all areas drug discovery, diagnostics, and the life sciences. The capabilities and advantages of each technique are compared and key applications involving small molecules, proteins, oligonucleotides, bacteriophage, viruses, bacteria, and cells are reviewed. The role of the interface between the biosensor surface (in the case of SPR and acoustic biosensors) and the chemical or biological systems to be studied is also covered with attention to the covalent and non-covalent coupling chemistries commonly employed.     

Dissolution behavior of tetrafluoroethylene-based fluoropolymers for 157-nm resist materials

We have synthesized various main-chain fluorinated polymers and studied base-resin properties, such as transparency at 157 nm, solubility in a standard alkaline developer, and lithographic performance. Main-chain-fluorinated polymers were synthesized by copolymerization of tetrafluoroethylene (TFE) with cyclic monomers, especially newly synthesized norbornene derivatives. We studied the correlation between pK_a(OH) and the solubility of the copolymers of TFE and functional (fluoroalkyl alcohol group) norbornenes. Their solubility depends on the pK_a value of the fluoroalkyl alcohol groups.We studied the impact of the polymerization initiators on base-resin properties. High transparency was obtained by using the fluorocarbon initiator. It was also confirmed that the monocyclic component improves dry-etch resistance and that fluorination at the terminal groups improves alkaline solubility.In addition, we found that the development characteristics of TFE/norbornene copolymers were significantly improved by the stereoselective (endo versus exo) partial protection of the hydroxyl groups in the fluoroalkyl alcohol moiety attached to norbornene unit. The polymer protected only in the exo position of the norbornene unit in the copolymer had a higher R_max and a higher contrast. Positive-working resists based on these fluoropolymers were developed and 55 nm dense lines could be delineated by exposure at 157 nm wavelength with an alternating phase shift mask on a 0.9 NA 157 nm exposure tool.     

Quartz crystal biosensor for detection of sugars and glycated hemoglobin

3-Aminophenylboronic acid (APBA) was used for construction of affinity mass sensors for determination of saccharides and glycated hemoglobin using complexation reaction with diol groups. Two approaches were tested for the bioligand layer fabrication—incorporation of APBA inside a thicker matrix and immobilization as a self-assembled monolayer, respectively. The direct affinity sensor with APBA embeded in the structure of glutaraldehyde-crosslinked bovine serum albumine provided linear response to mono- and dissacharides in the range from 0.1 to 15.0 mg/ml. This biosensor was also used for kinetic analysis of the interaction of boronic acid with diols; the values of association and dissociation constants were determined. The sensors with a monolayer of boronic groups were better suited for binding of glycated hemoglobin, probably due to improved steric access to the ligand.     

Determination of the Boron/Lead Ratio in Ceramic Materials Based on Electrochemical Quartz Crystal Microbalance

A method for quantitatively determining the relationship boron/lead in ceramic materials is presented. It is based on the attachment of microsamples of ceramic frits to an electrochemical quartz crystal microbalance (EQCM). After a reductive deposition step in the ?0.25 to ?0.85 V (vs. AgCl/Ag) potential range, well‐defined stripping peaks are recorded in 0.10 M NaCl plus 0.10 M mannitol. The deposition of boron and lead from suspensions of solid materials, and its subsequent oxidative dissolution can be monitorized at the EQCM. The quotient between the maximum mass gain and the corresponding charge passed enables for a direct quantitation of the boron/lead molar ratio in ceramic materials. Addition methods based on the EQCM examination of i) sample plus lead white (2PbCO₃.Pb(OH)₂) and ii) sample plus Li₂B₄O₇ mixtures are also presented. Results for boron‐containing ceramic frits are in excellent agreement with those obtained by reference methods.     

Investigation of adsorption of nanogram quantities of iron(II) tris-(1,10-phenanthrolinate) on glasses and silica by thermal lens spectrometry

Thermal lens spectrometry is used for studying adsorption equilibria in aqueous solutions at the level of nanogram quantities of iron(II) tris-(1,10-phenanthrolinate) as a model system. The kinetics of the sorption of the chelate on silica is studied and adsorption isotherms are built. Thermal lensing is used as a method for direct determination of the chelate concentration adsorbed on a quartz surface. The detected amount is 4.1×10⁻¹⁵ mol at the area irradiated by the excitation beam. The adsorption of iron(II) tris-(1,10-phenanthrolinate) on laboratory glassware at the nanogram level is characterised by measuring the residual concentration of the sorbate in solution. A procedure for handling and cleaning the laboratory glassware for determining nanogram amounts of iron in aqueous solutions is proposed. The sensitivity of thermal lensing both in measuring adsorption on silica and glass and quartz surfaces is 100-fold higher than diffuse-reflectance measurements under the same conditions.