New methods for the preparation of (bio)sensor surfaces : Molecular gradients and mixed monolayers containing oligo(ethylene glycols)

Alkanethiols form very close-packed and well ordered self-assembled monolayers on gold surfaces. The simple preparation of the organo-metal interface and the possibility to tailor the ƒç-functional group of the thiol individually for each target makes it attractive for a variety of applications. In the recent years many biosensors, for example affinity sensors, DNA chips and array systems, have been developed, which include a thiol sublayer for the covalent binding of receptor molecules. One important problem that must be avoided in biosensor design is non-specific adsorption of (bio)molecules on the sensing surface. Therefore, creating an optimal surface or basis layer is a major goal in biosensor applications. Two main directions for the preparation of thiol basis layers are described in this paper: 1) mixed monolayers and 2) molecular gradients. Oligo(ethylene glycol) terminated thiols (Eg4, Eg6 = HS-(CH2)15-CONH-(CH2)2-O)4,6-H), mercaptooctadecane (MOD), 16-mercaptohexadecan-1-ol (MHD), 16-mercaptohexadecanoic acid (MHA) and 16-mercaptohexadecan-1-amine (MDA) were chosen as model thiols for the investigations. All gold surfaces were cleaned using the TL1 procedure (NH3:H2O2:H2O 1:1:5 at 80¢XC). FT-IR spectroscopy, ellipsometry, impedance and contact angle measurements were used to characterize the monolayers. The combination of optical and electrochemical methods allows detailed statements about quality, structure and stability of the organic layer. The infrared reflection-absorption spectra were recorded at room temperature on a Bruker IFS 66, system equipped with a grazing angle (85o) infrared reflection accessory and a liquid-nitrogen-cooled MCT detector. The measurement chamber was continuously purged with nitrogen gas during the measurements. The acquisition time was around 10 min at 2 cm-1 resolution. A spectrum of a deuterated hexadecanthiolate (HS-(CD2)15-CD3) was used as reference

An Investigation on the Role of Spike Latency in an Artificial Olfactory System

Experimental studies have shown that the reactions to external stimuli may appear only few hundreds of milliseconds after the physical interaction of the stimulus with the proper receptor. This behavior suggests that neurons transmit the largest meaningful part of their signal in the first spikes, and than that the spike latency is a good descriptor of the information content in biological neural networks. In this paper this property has been investigated in an artificial sensorial system where a single layer of spiking neurons is trained with the data generated by an artificial olfactory platform based on a large array of chemical sensors. The capability to discriminate between distinct chemicals and mixtures of them was studied with spiking neural networks endowed with and without lateral inhibitions and considering as output feature of the network both the spikes latency and the average firing rate. Results show that the average firing rate of the output spikes sequences shows the best separation among the experienced vapors, however the latency code is able in a shorter time to correctly discriminate all the tested volatile compounds. This behavior is qualitatively similar to those recently found in natural olfaction, and noteworthy it provides practical suggestions to tail the measurement conditions of artificial olfactory systems defining for each specific case a proper measurement time

An Experimental Biomimetic Platform for Artificial Olfaction

Artificial olfactory systems have been studied for the last two decades mainly from the point of view of the features of olfactory neuron receptor fields. Other fundamental olfaction properties have only been episodically considered in artificial systems. As a result, current artificial olfactory systems are mostly intended as instruments and are of poor benefit for biologists who may need tools to model and test olfactory models. Herewith, we show how a simple experimental approach can be used to account for several phenomena observed in olfaction

EBB 332-4 - TEMBIKAR & KACA NOV 05.

5,10,15,20-Tetraferrocenyl porphyrin, H(2)TFcP, a simple example of a donor-acceptor system, was tested as ligand for the development of a novel multi-transduction chemical sensors aimed at the determination of transition metal ions. The fluorescence energy transfer between ferrocene donor and porphyrin acceptor sub-units was considered. The simultaneously measured optical and potentiometric responses of solvent polymeric membranes based on H(2)TFcP permitted the detection of lead ions in sample solutions, in the concentration range from 2.7 x 10(-7) to 3.0 x 10(-3) M. The detection limit of lead determination was 0.27 mu M, low enough to perform the direct analysis of Pb2+ in natural waters

From a Laboratory Exercise for Students to a Pioneering Biosensing Technology

Surface plasmon resonance (SPR) for biosensing was demonstrated 30 years ago. In the present contribution, its general background is described together with the necessary developments both in instrumentation and surface chemistry, leading to the final so-called BIAcore technology. The description is naturally colored by my personal opinion of the developments. SPR for the elucidation of organic mono- and multilayers introduced at the end of the 1970s formed the basis for the first biosensing demonstration of SPR in the beginning of the 1980s. It is pointed out how the need of an up-to-date laboratory exercise for the undergraduate students and the multidisciplinary environment at the Laboratory of Applied Physics at Linkoping University led to this demonstration. The initial experiments are touched upon and the further developments at Pharmacia, which led to the BIAcore technology, are described in some details. Some of the present activities in Linkoping related to optical biosensing with ubiquitous instrumentation are also described, including SPR detection with a computer screen and a web camera and most recently with a cellular phone

Jorden : En planet bland många

We have eight planets, quite a few dwarf planets and a lot of asteroids and comets orbiting the Sun. In the planetarium we can learn about the Earth and the Moon, the seasons and the stars. We explore the planets of the solar system, learn about the constellations and discover that just because it is called "a shooting star" does not mean that stars can fall from the skies

Månens Mysterier

Space is huge and we have yet to discover how to travel among the stars. The furthest any human has ever been is to the Moon. The stars may look close enough to touch at night, but they lie far beyond the planets of our Solar system. They belong to our galaxy; The Milky Way, one of hundreds of billions of galaxies in our Unverse. In this planetariumshow we take a closer look at our Moon and look beyond to try to understand these cosmic distances