Batch Quartz Crystal Microbalance Immunosensor using a Protein-Immobilized Hydrophilic Polymer

This paper describes a novel batch-type quartz crystal microbalance immunosensor that incorporates a commercially available stainless-steel holder. The sensor was coated with a hydrophilic polymer interface containing phosphatidylcholine analogs that attract water and amino groups for the covalent attachment of receptors. The hydrophilic polymer on a gold substrate captured antibodies and reduced nonspecific adsorption. Operation of the immunosensor required only one sample injection. A clear response triggered by antigen-antibody binding was observed and allowed measurement of the IgG antibody concentration with a superior signal-to-noise ratio using only commercially available components. We thus demonstrate an inexpensive and readily available sensor.     

Water Content of Hydrated Polymer Brushes Measured by an In Situ Combination of a Quartz Crystal Microbalance with Dissipation Monitoring and Spectroscopic Ellipsometry

Poly(methacryloyloxy ethyltrimethylammonium chloride) (PMETAC), poly(sulfopropylmethacrylate potassium salt), or poly(N‐isopropyl acrylamide) (PNIPAM) brushes are synthesized by means of the atom transfer radical polymerization technique from gold surfaces coated with a monolayer of the initiator ω‐mercaptoundecyl bromo isobutyrate. The brush growth is followed in situ and in real time by the combination of quartz crystal microbalance with dissipation technique (QCM‐D) and spectroscopic ellipsometry in a single device. The combination of QCM‐D and ellipsometry allows for the simultaneous determination of both the acoustic mass, m_acous, comprising the mass of the polymer and the solvent, and the optical mass, m_opt, which corresponds to the polymer mass alone. Brush hydration is calculated from the difference between the values obtained for m_acous and m_opt for each polymer synthesized. Brush hydration is then used to quantify the percentage of water released in the brush during collapse; a 30–40% release of water for PMETAC and PSPM brushes in 1 M NaCl and 80% for PNIPAM brushes when the temperature is increased to values above the lower critical solution temperature is observed.     

A review of monolithic multichannel quartz crystal microbalance: a review

Monolithic multichannel quartz crystal microbalance (MQCM) is an emerging technology for advanced sensing and measurement applications. In this report, a comprehensive review of MQCM technology is presented. Firstly, basic MQCM's design, simulation and characterization with emphasis on acoustic interference are described. Next, various MQCM schemes to minimize interference and enhance sensitivity of conventional MQCM devices based on modification of quartz substrate structure are digested. These include mesa, convex and x-axis inversion structures. Three important MQCM sensing platforms and their application areas are then discussed. These comprise MQCM as a static multichannel detector, series MQCM as a multichannel detector for the flow injection analysis and multi-frequency QCM for multi-sensitivity/multi-dynamic range detection. Finally, potential MQCM applications including electronic noses, bio-sensor arrays, and photocatatalytic measurement are illustrated and prospective MQCM applications including electronic tongues and electrochemical measurement are suggested.     

耗散型石英晶体微天平在生物医用高分子材料中的应用

石英晶体微天平(QCM)是一种基于石英晶体压电效应的分析检测技术,可实时在线提供石英晶体表面吸附层质量、厚度、粘弹性等信息,由此获得表面分子相互作用关系。 耗散型石英晶体微天平(QCM-D)因其独特的对粘弹性的解析,使其在高分子材料中的应用迅速发展,尤其是生物医用高分子材料领域,已用来评价生物医用高分子材料的表界面相互作用,力学和生物相容性等。 本文简单介绍了耗散型石英晶体微天平的基本原理及理论模型,重点综述了近几年QCM-D在高分子链构象、蛋白质吸附、生物大分子相互作用、药物释放以及水凝胶中的应用,并且展望了QCM-D的未来发展趋势。     

Salt‐Induced Depression of Lower Critical Solution Temperature in a Surface‐Grafted Neutral Thermoresponsive Polymer

Summary: Quartz crystal microbalance with dissipation monitoring (QCM‐D) is employed to determine the effect of salt on the volume phase transition of thermoresponsive polymer brushes. Changes in mass and viscoelasticity of poly(N‐isopropylacrylamide) (PNIPAM) layers grafted from a QCM‐D crystal are measured as a function of temperature, upon contact with aqueous solutions of varying salt concentrations. The phase‐transition temperature of PNIPAM brushes, T_C,graft, quantified from the QCM‐D measurements is found to decrease as the concentration of salt is increased. This phenomenon is explained by the tendency of salt ions to affect the structure of water molecules (Hofmeister effect). However, in contrast to the linear decrease in phase‐transition temperature upon increasing salt concentration observed for free PNIPAM, the trend in T_C,graft for PNIPAM brushes is distinctively non‐linear.

Schematic representation of the effect of salt concentration on the phase transition behavior of thermoresponsive polymer brushes.     

Towards Vaporized Molecular Discrimination: A Quartz Crystal Microbalance (QCM) Sensor System Using Cobalt‐Containing Mesoporous Graphitic Carbon

A recent study on nanoporous carbon based materials (J. Am. Chem. Soc.­ 2012 , 134, 2864) showed that the presence of abundant graphitized sp² carbon species in the frameworks led to higher affinity for aromatic hydrocarbons than their aliphatic analogues. Herein, improved understanding of the sensitive and selective detection of aromatic substances by using mesoporous carbon (MPC)‐based materials, combined with a quartz crystal microbalance (QCM) sensor system, was obtained. MPCs were synthesized by direct carbonization of mesoporous polymers prepared from resol through a soft templating approach with Pluronic F127. The carbon‐based frameworks can be graphitized through the addition of a cobalt source to the precursor solution, according to the catalytic activity of the cobalt nanoparticles formed during the carbonization process. From the Raman data, the degree of the graphitization was clearly increased by increasing the cobalt content and elevating the carbonization temperature. From a QCM study, it was proved that the highly graphitized MPCs exhibited a higher affinity for aromatic hydrocarbons than their aliphatic analogues. By increasing the degree of graphitization in the carbon‐based pore walls, the MPCs showed both larger adsorption uptake and faster sensor response towards toxic benzene and toluene vapors.     

Non-Aqueous Assay System for Phenobarbital Using Biomimetic Bulk Acoustic Wave Sensor Based on a Molecularly Imprinted Polymer

ABSTRACT

A new biomimetic bulk acoustic wave (BAW) sensor based on a molecularly imprinted polymer (MIP) was fabricated and applied for the determination of phenobarbital The MIP was synthesized using phenobarbital as the template molecule and methacrylic acid as the functional monomer by the non-covalent method. In absolute ethanol, the sensor exhibited good selectivity and sensitivity. A linear relationship between 9.0×10^?8 M and 5.0×10^?5 M was revealed. The determination limit was 5.0×10^?8 M. In harsh chemical environments such as high temperature, organic solvent, bases, acids, etc., the sensor still exhibited long-time stability. Satisfactory results of real sample assay were obtained by the proposed method.     

A Novel Ion-Selective Sensor for Procaine Hydrochloride Based on a Piezoelectric Quartz Crystal Coated with a Procaine Tetraphenylborate PVC Membrane

 A novel ion-selective sensor for procaine hydrochloride has been proposed and applied successfully to analysis of pharmaceutical preparations. The sensor is based on modification of the Ag-electrode of an AT-cut piezoelectric quartz crystal with a PVC membrane containing procaine tetraphenylborate. A linear relation between the logarithm of the response frequency and the logarithm of the procaine hydrochloride concentration was found experimentally and could be explained by combination of a modified Sauerbrey equation and the Freundlich isotherm. The detection range was from 8.3 × 10⁻⁸ to 5.0 × 10⁻³ M with a detection limit of 8.3 × 10⁻⁸ M. The selectivity of the sensor and the influence of experimental parameters such as solution pH and detection time were investigated. Received February 10, 1999. Revision October 10, 1999.     

A practical guide to quartz crystal microbalance with dissipation monitoring of thin polymer films

Quartz crystal microbalance with dissipation (QCM-D) monitoring is a powerful tool used to sensitively examine the real-time responses of polymer films to external responses. For example, the technique is commonly used to monitor film growth, material adsorption, thin film swelling, and ion exchange. With its rapidly expanding use, this review is intended to introduce new users to the basic principles of QCM-D, along with practical challenges and remedies specific to polymer thin films. For both new and experienced users, specific case studies are highlighted including layer-by-layer assembly, electrochemical QCM-D, swelling, sensing, and biological application. Last, the review recommends future directions for research and areas of growth.     

易衍生化温敏高分子刷的制备及其温敏行为研究

温敏材料由于优异的性能和潜在的应用价值而具有良好的发展前景.利用超分子自组装单层(SAM)与表面引发聚合(SIP)技术将2-(2-甲氧乙氧基)甲基丙烯酸乙酯(MEO2MA)与聚乙二醇甲基丙烯酸酯(OEGMA526)的共聚物poly(MEO2MAco-OEGMA526)接枝于金表面,探索了不同引发剂溶液浓度(χIsol)、单体OEGMA526摩尔浓度(C526)与干态膜厚度(d)对该高分子刷性质的影响.应用石英晶体微天平(QCM)对其温敏行为进行研究,结果表明:在χIsol=1%与C526=5%条件下制备的高分子刷,最低临界溶解温度(LCST)为34℃;其LCST由OEGMA526的单体摩尔浓度决定,不受膜厚的影响.该高分子刷在接枝生物素后其与链霉亲和素的结合实验证明,高分子刷末端的羟基为其官能团化提供了契机.该易衍生化温敏高分子刷为发展新型温敏材料提供了研究基础.     

A Novel Method for Mutagenicity Test of Carcinogen by using a Series Piezoelectric Quartz Crystal Bactrial Growth Sensor

ABSTRACT

A new method for mutagenicity testing of carcinogens is proposed in this paper. Mutagenic activity is examined through monitoring of the growth situation of Salmonella typhimurium TA98 strain with a series piezoelectric quartz crystal (SPQC) sensor. This method needs no immobilization and preincubation of microorganism, and is simple and rapid. It can be applied to detect mutagen directly. When it was used to study the mutagenicity of dimethyl sulfate, the test time was 4 h at 37°C. There was a good linear relationship between frequency shift and the dose of mutagen in the range 2.5-20 μg/mL and the regression equation was ∠F = 53.82 + 3.81C. Some experimental conditions are also discussed in detail.     

A 21st century technique for food control: Electronic noses

This work examines the main features of modern electronic noses (e-noses) and their most important applications in food control in this new century. The three components of an electronic nose (sample handling system, detection system, and data processing system) are described. Special attention is devoted to the promising mass spectrometry based e-noses, due to their advantages over the more classical gas sensors. Applications described include process monitoring, shelf-life investigation, freshness evaluation, authenticity assessment, as well as other general aspects of the utilization of electronic noses in food control. Finally, some interesting remarks concerning the strengths and weaknesses of electronic noses in food control are also mentioned.