20 research outputs found
Electroanalysis may be used in the Vanillin Biotechnological Production
This study shows that electroanalysis may be used in vanillin biotechnological production. As a matter of fact, vanillin and some molecules implicated in the process like eugenol, ferulic acid, and vanillic acid may be oxidized on electrodes made of different materials (gold, platinum, glassy carbon). By a judicious choice of the electrochemical method and the experimental conditions the current intensity is directly proportional to the molecule concentrations in a range suitable for the biotechnological process. So, it is possible to imagine some analytical strategies to control some steps in the vanillin biotechnological production: by sampling in the batch reactor during the process, it is possible to determine out of line the concentration of vanillin, eugenol, ferulic acid, and vanillic acid with a gold rotating disk electrode, and low concentration of vanillin with addition of hydrazine at an amalgamated electrode. Two other possibilities consist in the introduction of electrodes directly in the batch during the process; the first one with a gold rotating disk electrode using linear sweep voltammetry and the second one requires three gold rotating disk electrodes held at different potentials for chronoamperometry. The last proposal is the use of ultramicroelectrodes in the case when stirring is not possible
Investigation of interactions of a resorcin[4]arene receptor with bilayer lipid membranes (BLMs) for the electrochemical biosensing of mixtures of dopamine and ephedrine
The present article investigates the interactions of a
resorcin[4]arene receptor with planar bilayer lipid membranes (BLMs)
that can be used for the electrochemical detection of dopamine and
ephedrine. BLMs were composed of egg phosphatidylcholine and 35% (w/w)
dipalmitoyl phosphatidic acid in which the receptor was incorporated.
These BLMs modified with the resorcin[4]arene receptor can be used as
one-shot sensors for the direct electrochemical sensing of these
energizing-stimulating substances. The interactions of these compounds
with the lipid membranes were found to be electrochemically transduced
in the form of a transient current signal with a duration of seconds,
which reproducibly appeared within 8 and 20 s after exposure of the
membranes to dopamine and ephedrine, respectively, The response time for
BLMs without the receptor for dopamine was about 3 min, whereas no
signals were obtained for ephedrine in the absence of the receptor. The
mechanism of signal generation was investigated by differential scanning
calorimetric studies. These studies revealed that the adsorption of the
receptor is through the hydrophobic tails of the receptor, whereas
hydrophilic groups of the receptor were directed towards the electrolyte
solution enhancing the ion transport through the lipid membranes. The
magnitude of the transient current signal was related to the
concentration of the stimulating agent in bulk solution in the
micromolar range. No interferences from ascorbic acid were noticed
because of the use of the negatively charged lipids in membranes. The
present technique can be used as one-shot sensor for the detection of
these pharmaceutical substances and future research is targeted to the
determination of these chemicals in human biofluids such as urine of
athletes. (C) 2002 Elsevier Science B.V. All rights reserved
Stabilized filter-supported bilayer lipid membranes (BLMs) for automated flow monitoring of compounds of clinical, pharmaceutical, environmental and industrial interest
This paper describes the results of analytical applications of
electrochemical biosensors based on bilayer lipid membranes (BLMs) Sor
the automated rapid and sensitive flow monitoring of substrates of
hydrolytic enzymes, antigens and triazine herbicides. BLM’s, composed of
mixtures of egg phosphatidylcholine (egg PC) and dipalmitoylphosphatidic
acid (DPPA), were supported on ultrafiltration membranes (glass
microfibre or polycarbonate) which were found to enhance their stability
fos flow experiments. The proteins (enzymes, antibodies) were
incorporated into a floating lipid matrix at an air-electrolyte
interface, and then a casting procedure was used to deliver the lipid
onto the filter supports for BLM formation. Injections of the analyte
were made into flowing streams of the carrier electrolyte solution and a
current transient signal was obtained with a magnitude related to the
analyte concentration. Substrates of hydrolytic enzyme reactions
(acetylcholine, urea and penicillin) could be determined at the
micromolar level with a maximum rate of 220 samples/h, whereas antigens
(thyroxin) and triazine herbicides (simazine, atrazine and propazine)
could be monitored at the nanomolar level in less than 2 min. The time
of appearance of the transient response obtained for herbicides was
increased to the order of simazine, atrazine and propazine which has
permitted analysis of these triazines in mixtures
1994 MCBRYDE-MEDAL-AWARD-LECTURE - INVESTIGATIONS OF ORGANIZED MONOLAYER FILMS FOR BIOSENSOR DEVELOPMENT
Our interests have focused on the investigation and development of
biosensors that use chemically selective membranes to measure the
concentration of specific species in complex media. One fundamental idea
is that protein, which can bind selectively to a specific organic or
biochemical species, can be incorporated into an ordered lipid or
surfactant membrane assembly such that selective binding events lead to
changes in the structure of the membrane (transduction) that can be
measured quantitatively. The primary advantage of this method of
detection is that it is applicable to interactions of enzymes,
antibodies, receptors, and lectins, and it may be extended to
investigations of DNA/RNA hybridization. This detection method therefore
provides a sensitive generic strategy for sensor applications. The
central problem to be solved is how the alteration of the structure of a
membrane that is caused by binding events of protein or genetic material
can give rise to an analytical signal. We have been focusing our efforts
in the areas of fluorescence spectroscopy and electrochemical methods.
The electrochemical methods rely on detection in changes of the
permeability of membranes to ions and provide systems with very low
background signal, leading to the possibility of detection of single
molecular-binding events. Fluorescent systems operate on the basis that
a chemically selective membrane containing a fluorescent indicator can
provide an analytical signal caused by the change of the structure of
the membrane due to the binding events