A Microelectrode Array with Reproducible Performance Shows Loss of Consistency Following Functionalization with a Self-Assembled 6-Mercapto-1-hexanol Layer

For analytical applications involving label free biosensors and multiple measurements, i.e. across an electrode array, it is essential to develop complete sensor systems capable of functionalisation and of producing highly consistent responses. To achieve this, a multi-microelectrode device bearing twenty-four equivalent 50 µm diameter Pt disc microelectrodes was designed in an integrated 3-electrode system configuration and then fabricated. Cyclic voltammetry and electrochemical impedance spectroscopy were used for initial electrochemical characterisation of the individual working electrodes. These confirmed the expected consistency of performance with a high degree of measurement reproducibility for each microelectrode across the array. With the aim of assessing the potential for production of an enhanced multi-electrode sensor for biomedical use, the working electrodes were then functionalised with 6-mercapto-1-hexanol (MCH). This is a well-known and commonly employed surface modification process, which involves the same principles of thiol attachment chemistry and self-assembled monolayer (SAM) formation commonly employed in the functionalisation of electrodes and the formation of biosensors. Following this SAM formation, the reproducibility of the observed electrochemical signal between electrodes was seen to decrease markedly, compromising the ability to achieve consistent analytical measurements from the sensor array following this relatively simple and well-established surface modification. To successfully and consistently functionalise the sensors it was necessary to dilute the constituent molecules by a factor of ten thousand to support adequate SAM formation on microelectrodes. The use of this multi-electrode device therefore demonstrates in a high throughput manner irreproducibility in the SAM formation process at the higher concentration, even though these electrodes are apparently functionalised simultaneously in the same film formation environment, confirming that the often seen significant electrode-to-electrode variation in label-free SAM biosensing films formed under such conditions is not likely to be due to variation in film deposition conditions, but rather kinetically controlled variation in the SAM layer formation process at these microelectrodes

A systematic study of the influence of nanoelectrode dimensions on electrode performance and the implications for electroanalysis and sensing

Micron resolution photolithography has been employed to make microsquare nanoband edge electrode (MNEE) arrays with reproducible and systematic control of the crucial dimensional parameters, including array element size and spacing and nanoelectrode thickness. The response of these arrays, which can be reproducibly fabricated on a commercial scale, is first established. The resulting characteristics (including high signal and signal-to-noise, low limit of detection, insensitivity to external convection and fast, steady-state, reproducible and quantitative response) make such nanoband electrode arrays of real interest as enhanced electroanalytical devices. In particular, the nanoelectrode response is presented and analysed as a function of nanometre scale electrode dimension, to assess the impact and relative contributions of previously postulated nanodimensional effects on the resulting response. This work suggests a significant contribution of migration at the band edges to mass transfer, which affects the resulting electroanalytical response even at ionic strengths as large as 0.7 mol dm-3 and for electrodes as wide as 50 nm. For 5 nm nanobands, additional nanoeffects, which are thought to arise from the fact that the size of the redox species is comparable to the band width, are also observed to attenuate the observed current. The fundamental insight this gives into electrode performance is discussed along with the consequent impact on using such electrodes of nanometre dimension

An electrochemical comparison of thiolated self‐assembled monolayer (SAM) formation and stability in solution on macro‐ and nanoelectrodes

Thiolated self-assembled monolayers (SAMs) formed on metal electrodes have been a topic of interest for many decades. One of the most common applications is in the field of biosensors, where this is a growing need for functionalising nanoelectrodes to realise more sensitive and implantable sensors. For all these applications the SAM functionalised nanoelectrodes will need to make reliable and interpretable electrochemical measurements. In this work, Electrochemical Impedance Spectroscopy (EIS) is used to monitor both the formation and subsequent stability of 6-mercaptohexan-1-ol SAMs on macro and nanoelectrodes and compares the two. To develop effective devices, it is crucial to understand both SAM formation and the resulting signal stability on nanoscale surfaces and this is done by comparing to behaviours observed at the well understood macroscale. We report an initial stochastic binding event and subsequent re-arrangement of the SAMs for both electrode types. However, this re-arrangement takes hours on the macro scale electrodes but only seconds on the nanoelectrodes. This is proposed to be due to the different structure of the SAMs on the electrodes predominantly driven by their bulk to edge ratios. After formation, the SAMs formed on both macro and nanoelectrodes exhibit significant instability over time. The reported results have practical implications for the construction of SAM based biosensors on macro and nanoscale electrodes

Functionalised Microscale Nanoband Edge Electrode (MNEE) Arrays; the systematic quantitative study of hydrogels grown on nanoelectrode biosensor arrays for enhanced sensing in biological media

We demonstrate a hydrogel-coated nanoelectrode array biosensor that is resistant to biofouling.</p

Method and Compositions for Biofouling Deterrence

A method of deterring biofouling of a surface comprising attaching an adduct having formula (I) or noradrenalin to the surface. Formula (I) being defined as compounds that have the formula A-L-R wherein A is i) a C6 or C10 substituted aryl ring, or ii) a C1-C9 substituted or unsubstituted heteroaryl ring: L is a linking group, and R is a primary amino moiety comprising unit

1972 Research Progress Reports, Fruit and Vegetable Processing and Food Technology

Evaluation of tomato cultivars / W. A. Gould, James Black, Louise Howiler, Shirley Perryman, and Stanley Z. Berry -- Effects of food additives on the quality of canned tomatoes / Wilbur A. Gould, John Mount, Jacquelyn Gould, Louise Howiler, and James Black -- Effect of storage temperature on shelf life of ascorbic acid fortified tomato juice / Gerald A. Pope and Wilbur A. Gould -- Survey of waste disposal practices of Ohio tomato processors / J. R. Geisman -- Evaluation of snap bean varieties for processing / Wilbur A. Gould, Jacquelyn Gould and Roberta Topits -- The effect of variety, size, and fermentation temperature on the quality attributes of cucumber pickles / Gary Flinn and Wilbur A. Gould -- Progress report on frozen corn-on-the-cob / James W. Swinehart and Wilbur A. Gould -- Progress report on cabbage lipids / Andrew C. Peng -- Effect of soybean flour on quality and protein content in the manufacture of doughnuts / Mohamed I. Mahmoud and Wilbur A. Goul

Method and Compositions for Biofouling Deterrence

A method of deterring biofouling of a surface comprising attaching an adduct having formula (I) or noradrenalin to the surface. Formula (I) being defined as compounds that have the formula A-L-R wherein A is i) a C6 or C10 substituted aryl ring, or ii) a C1-C9 substituted or unsubstituted heteroaryl ring: L is a linking group, and R is a primary amino moiety comprising unit