Electroanalysis of myoglobin based on electropolymerized molecularly imprinted polymer poly-o-phenylenediamine and carbon nanotubes/screen printed electrode.

Electroanalysis of myoglobin as a marker of acute myocardial infarction by means of screenprinted electrodes modified with multiwalled carbon nanotubes and polymeric artificial antibodies is developed. Plastic antibodies to myoglobin (molecularly imprinted polymers, MIPs) based on o-phenylenediamine were produced by electropolymerization. Molecular imprinting technology in biosensor analysis was used as alternative to natural receptors (namely, antibodies) and demonstrated high sensitivity (1.5 × 10(-2) A/nmol of myoglobin) and selectivity.

Electrosynthesis and binding properties of molecularly imprinted poly-o-phenylenediamine as artificial antibodies for electroanalysis of myoglobin.

Molecularly imprinted poly-o-phenylenediamine with template myoglobin molecules (i.e., polymeric antibodies to myoglobin, molecularly imprinted polymer, MIP) was synthesized via electropolymerization. Electropolymerization, washing, and the interaction of the polymeric antibodies with myoglobin was examined by square wave voltammetry and microgravimetry. The analysis of myoglobin was carried out through direct electrochemical detection of the reduction peak of Fe(3+) of the hemeprotein on screen-printed graphite electrodes modified by the MIP. According to the electrochemical analysis, MIP surfaces demonstrated remarkably higher ability to bind the protein compared to that of surfaces prepared by the same route under the same conditions but in the absence of myoglobin (surfaces of the non-imprinted polymer, NIP). The imprinting factor I max(MIP)/I max(NIP) was found to be 2-4. The equilibrium dissociation constant K d of the interaction of myoglobin with MIP electrodes was evaluated as (2.4 ± 0.5) × 10(-8) M. The lower detection limit of myoglobin by a MIP sensor was determined as 0.5 × 10(-9) M, the range of detectable concentrations being 10(-9)-10(-5) M.

Improved electrochemical analysis of neuropathy target esterase activity by a tyrosinase carbon paste electrode modified by 1-methoxyphenazine methosulfate.

A graphite-paste tyrosinase biosensor was improved by adding 1-methoxyphenazine methosulfate as a mediator. Mediator modification enhanced sensitivity to phenol 4-fold and long-term stability 3-fold. Phenol could be detected at 25 nM (S/N = 2) using an Ag/AgCl reference electrode. The biosensor was used to measure the activity of a toxicologically significant enzyme, neuropathy target esterase (NTE), which yields phenol by hydrolysis of the substrate, phenyl valerate. Using the new biosensor, blood and brain NTE inhibition by organophosphorus (OP) compounds with different neuropathic potencies were well correlated (r = 0.990, n = 7), supporting the use of blood NTE as a biochemical marker of exposure to neuropathic OP compounds.

Bioelectrochemical analysis of neuropathy target esterase activity in blood.

Bioelectrochemical analysis of neuropathy target esterase (NTE) and its inhibitors is based on the combination of the NTE-catalyzed hydrolysis of phenyl valerate and phenol detection by a tyrosinase carbon-paste electrode. The use of the tyrosinase electrode improves 10-fold the sensitivity of NTE detection in comparison with a spectrophotometric method. The tyrosinase electrode was found to be suitable for measurements in whole human blood where spectrophotometric detection is considerably restricted. The specificity of NTE in blood for mipafox and di-2-propyl phosphorofluoridate was close to that for neuronal NTE. The NTE-like activity in blood was determined to be 0.19 +/- 0.02 nmol/min/mg of protein.

A new approach for determination of neuropathy target esterase activity.

Neuropathy target esterase (NTE) was shown to be an excellent biochemical marker for screening of organophosphates (OPs) with respect to their ability to result in organophosphate induced delayed neurotoxicity (OPIDN). This paper describes a new biosensor approach to the analysis of NTE and its inhibitors. The method is based on the combination of NTE enzymatic hydrolysis of phenyl valerate (PV) with phenol detection by the Clark-type oxygen electrode modified by immobilized tyrosinase. The validity of this biosensor method is confirmed by the facts that the calibration curves for NTE obtained by colorimetric and flow-through electrochemical methods were nearly identical and the titration of NTE by test inhibitor mipafox was shown to yield the same pI50 values. The developed electrochemical methods can be considered as a promising approach both for serial express NTE analysis and for kinetic characteristics of NTE.

[Anomalous temperature dependence of the activity of immobilized alpha-chymotrypsin preparations]. / Anomal'naia temperaturnaia zavisimost' aktivnosti preparatov immobilizovannogo alpha-khimotripsina.

Catalytic activity of alpha-chymotrypsin preparations covalently included in the matrix of the poly-N-isopropylacrylamide gel does not follow Arrhenius equation above the low critical temperature of the polymer dissolution. Starting from this temperature, at which the changes of polymer structure takes place (hydrophobization), the temperature increase results in a rate lowering for the chemical reaction catalyzed by the enzyme. This phenomenon is reversible. A correlation between temperature dependence of the immobilized alpha-chymotrypsin activity and the dehydration degree of the carrier is observed. The decrease of the water content in the matrix causes a change of the substrate specificity of the immobilized alpha-chymotrypsin.