Polycyclic aromatic hydrocarbons (PAHs) in dry tea leaves and tea infusions in Vietnam: contamination levels and dietary risk assessment

The total mean ∑[Formula: see text] in samples were from 75.3 to 387.0 ng/g dry weight (d.w) and showed high value in black dry tea, followed by herbal, oolong, and green tea. The mean ∑[Formula: see text] (a combination of benz[a]anthracene, chrysene, benzo[b]fluoranthene, and benzo[a]pyrene) values were 54.3 ng/g, 16.4 ng/g, 14.2 ng/g, and 6.6 ng/g for black, herbal, green, and oolong teas, respectively. Concentration for benzo[a]pyrene (BaP) was from 0.4 to 35.8 ng/g, and the BaP equivalent concentration values ranged from 0.3 to 48.1 ng/g. There was only 1 black tea sample that BaP concentration exceeded the maximum level according to European Union (EU) standards. Tea samples marketed in Vietnam showed insignificant difference with the samples from other origins by same analytical method. Black teas showed high PAHs contents in dry tea samples but the released percentage of sum of PAHs from tea-to-tea infusion was lower than that in other tea type samples. The released percentages of PAH4 from tea-to-tea infusion were 40.7, 15.4, and 1.9 for green, herbal, and black tea. High temperature in black tea manufacturing processes might reduce essential oil content in tea that might effect on the PAHs partially release into the infusion. Indeed, based on EU regulations, we may conclude that tea consumers are safe in risk of exposure to PAHs obtained from teas.

Future Trends for In Situ Monitoring of Polycyclic Aromatic Hydrocarbons in Water Sources: The Role of Immunosensing Techniques

Polycyclic aromatic hydrocarbons (PAHs) are hazardous environmental pollutants found in water, soil, and air. Exposure to this family of chemicals presents a danger to human health, and as a result, it is imperative to design methods that are able to detect PAHs in the environment, thus improving the quality of drinking water and agricultural soils. This review presents emerging immunoassay techniques used for in situ detection of PAH in water samples and how they compare to common-place techniques. It will discuss their advantages and disadvantages and why it is required to find new solutions to analyze water samples. These techniques are effective in reducing detection times and complexity of measurements. Immunoassay methods presented here are able to provide in situ analysis of PAH concentrations in a water sample, which can be a great complement to existing laboratory techniques due to their real-time screening and portability for immunoassay techniques. The discussion shows in detail the most relevant state-of-the-art surface functionalization techniques used in the field of immunosensors, with the aim to improve PAH detection capabilities. Specifically, three surface functionalization techniques are key approaches to improve the detection of PAHs, namely, substrate surface reaction, layer-by-layer technique, and redox-active probes. These techniques have shown promising improvements in the detection of PAHs in water samples, since they show a wider linear range and high level of sensitivity compared to traditional PAH detection techniques. This review explores the various methods used in the detection of PAH in water environments. It provides extra knowledge to scientists on the possible solutions that can be used to save time and resources. The combination of the solutions presented here shows great promise in the development of portable solutions that will be able to analyze a sample in a matter of minutes on the field.

A sensor array for the discrimination of polycyclic aromatic hydrocarbons using conjugated polymers and the inner filter effect

The inner filter effect and multivariate array sensing using conjugated polymers are combined for the detection and challenging discrimination of closely related polycyclic aromatic hydrocarbons.

Natural and anthropogenic activities result in the production of polycyclic aromatic hydrocarbons (PAHs), persistent pollutants that negatively impact the environment and human health. Rapid and reliable methods for the detection and discrimination of these compounds remains a technological challenge owing to their relatively featureless properties, structural similarities, and existence as complex mixtures. Here, we demonstrate that the inner filter effect (IFE), in combination with conjugated polymer (CP) array-based sensing, offers a straightforward approach for the quantitative and qualitative profiling of PAHs. The sensor array was constructed from six fluorescent fluorene-based copolymers, which incorporate side chains with peripheral 2-phenylbenzimidazole substituents that provide spectral overlap with PAHs and give rise to a pronounced IFE. Subtle structural differences in copolymer structure result in distinct spectral signatures, which provide a unique “chemical fingerprint” for each PAH. The discriminatory power of the array was evaluated using linear discriminant analysis (LDA) and principal component analysis (PCA) in order to discriminate between 16 PAH compounds identified as priority pollutants by the US Environmental Protection Agency (EPA). This array is the first multivariate system reliant on the modulation of the spectral signatures of CPs through the IFE for the detection and discrimination of closely related polynuclear aromatic species.

Metabolomics reveals defensive mechanisms adapted by maize on exposure to high molecular weight polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons are an important group of persistent organic pollutants. Using plants to remediate PAHs has been recognized as a cost-effective and environmentally friendly technique. However, the overall impact of PAHs on the regulation of plant metabolism has not yet been explored. In this study, we analyzed the alteration in the maize (Zea mays L.) metabolome on exposure to high molecular weight PAHs such as benzo[a]pyrene (BaP) and pyrene (PYR) in a hydroponic medium, individually and as a mixture (BaP + PYR) using GC-MS. The differences in the metabolites were analyzed using XCMS (an acronym for various forms (X) of chromatography-mass spectrometry), an online-based data analysis tool. A significant variation in metabolites was observed between treatment groups and the unspiked control group. The univariate, multivariate and pathway impact analysis showed there were more significant alterations in metabolic profiles between individual PAHs and the mixture of BaP and PYR. The marked changes in the metabolites of galactose metabolism and aminoacyl tRNA biosynthesis in PAHs treated maize leaves exhibit the adaptive defensive mechanisms for individual and PAHs mixture. Therefore, the metabolomics approach is essential for an understanding of the complex biochemical responses of plants to PAHs contaminants. This knowledge will shed new light in the field of phytoremediation, bio-monitoring, and environmental risk assessment.

Review of PAH contamination in food products and their health hazards

Public concern over the deleterious effects of polycyclic aromatic hydrocarbons (PAHs) has grown rapidly due to recognition of their toxicity, carcinogenicity, and teratogenicity. The aim of this review is to describe the status of PAH pollution among different food types, the route of dietary intake, measures for its reduction, and legislative approaches to control PAH. To this end, a comprehensive review is outlined to evaluate the status of PAH contamination in many important food categories along with dietary recommendations. Our discussion is also extended to describe preventive measures to reduce PAH in food products to help reduce the risks associated with human intake.

Investigating the quantitative structure-activity relationships for antibody recognition of two immunoassays for polycyclic aromatic hydrocarbons by multiple regression methods

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous contaminants found in the environment. Immunoassays represent useful analytical methods to complement traditional analytical procedures for PAHs. Cross-reactivity (CR) is a very useful character to evaluate the extent of cross-reaction of a cross-reactant in immunoreactions and immunoassays. The quantitative relationships between the molecular properties and the CR of PAHs were established by stepwise multiple linear regression, principal component regression and partial least square regression, using the data of two commercial enzyme-linked immunosorbent assay (ELISA) kits. The objective is to find the most important molecular properties that affect the CR, and predict the CR by multiple regression methods. The results show that the physicochemical, electronic and topological properties of the PAH molecules have an integrated effect on the CR properties for the two ELISAs, among which molar solubility (S_m) and valence molecular connectivity index (³χ^v) are the most important factors. The obtained regression equations for Ris^C kit are all statistically significant (p < 0.005) and show satisfactory ability for predicting CR values, while equations for RaPID kit are all not significant (p > 0.05) and not suitable for predicting. It is probably because that the Ris^C immunoassay employs a monoclonal antibody, while the RaPID kit is based on polyclonal antibody. Considering the important effect of solubility on the CR values, cross-reaction potential (CRP) is calculated and used as a complement of CR for evaluation of cross-reactions in immunoassays. Only the compounds with both high CR and high CRP can cause intense cross-reactions in immunoassays.

Near real-time, on-site, quantitative analysis of PAHs in the aqueous environment using an antibody-based biosensor

Rapid, on-site, quantitative assessments of dissolved polycyclic aromatic hydrocarbons (PAHs) were demonstrated for two field applications. The platform, a KinExA Inline Sensor (Sapidyne Instruments), employed the monoclonal anti-PAH antibody, 7B2.3, which has specificity for 3- to 5-ring PAHs. A spatial study was conducted near a dredging site where contaminated sediments were being removed, and a temporal study was performed during a rainfall event. Most importantly, the generation of near real-time data guided management decisions in the field and determined proper sampling protocols for conventional analyses. The method was able to determine PAH concentrations as low as 0.3 µg/L, within 10 min of sample acquisition, and to assess 80+ samples (not including standards and blanks) in less than 3 d. These results were compared with a laboratory-based gas chromatography-mass spectrometry method in which a wide array of PAHs, including alkylated homologs, were examined. This system shows great promise as a field instrument for the rapid monitoring of PAH pollution.

Screening and characterization of new monoclonal anti-benzo[a]pyrene antibodies using automated flow-through microarray technology

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants, which can cause cancer in humans. The maximum tolerable limit of benzo[a]pyrene (B[a]P) in drinking water was set to 10 ng/L by the European Commission (Council Directive 98/83/EC), because of its highly carcinogenic and mutagenic effect on humans. In the present investigation, mice were immunized with B[a]P-bovine serum albumin conjugates and 110 generated hybridoma cell lines screened by different techniques to identify clones that produce anti-B[a]P antibodies. Subsequently, a new automated flow-through biochip noncompetitive direct chemiluminescence immunoassay (CLEIA) was compared with conventional indirect and direct enzyme-linked immunosorbent assays (ELISAs). It was demonstrated that the microchip-based screening method compared to ELISA was fast and very sensitive with use of only nanoliter volumes of supernatant. Forty clones could be evaluated in less than 5 min. Six high affinity monoclonal antibodies with different cross-reactivities (CR) for individual PAHs were identified by the chip-based assay and indirect microtiter plate ELISA. In comparison, the direct ELISA in the microtiter plate failed to identify three of these clones. The four antibodies with the highest affinity had half maximum inhibitory concentrations (IC(50) values) between 0.31 and 0.92 μg/L for B[a]P. Affinity constants of these four antibodies were determined by surface plasmon resonance using a water soluble B[a]P-peptide. The observed CR pattern of the four monoclonal antibodies for 16 tested PAHs was quite different. Only one specific antibody for B[a]P was observed, while others were more suitable for class-specific PAH determination.

Electrochemical biosensors

Electrochemical biosensors combine the sensitivity of electroanalytical methods with the inherent bioselectivity of the biological component. The biological component in the sensor recognizes its analyte resulting in a catalytic or binding event that ultimately produces an electrical signal monitored by a transducer that is proportional to analyte concentration. Some of these sensor devices have reached the commercial stage and are routinely used in clinical, environmental, industrial, and agricultural applications. The two classes of electrochemical biosensors, biocatalytic devices and affinity sensors, will be discussed in this critical review to provide an accessible introduction to electrochemical biosensors for any scientist (110 references).

A review on the practical application of human biomonitoring in integrated environmental health impact assessment

Environmental health sciences focus on the link between the presence of contaminants in the environment and their relation with possible adverse health effects. Within this context, human biomonitoring (HBM) data have proven to be a valuable addition to, or have even surpassed, estimates of exposure based on environmental measures. Probably the main achievement of HBM data is that it provides an integrated overview of the pollutant dose any constituent is exposed to and incorporates bioaccumulation, excretion, half-life, and other potentially critical toxicokinetic parameters. In an integrated environmental health impact assessment framework, HBM serves as a pivotal point between environment and health, on the one hand leaning on environmental data to provide information on sources and pathways of exposure, and on the other hand clarifying hypotheses on the relationship between internal dose and prevalence of disease clusters. This study reflects the work performed in the INTARESE project (Integrated Assessment of Health Risk of Environmental Stressors in Europe). Because it was perceived that there was an overall lack of knowledge on the general methodology and potential application of HBM data in integrated environmental health impact assessment, an extensive review of literature was performed on past and current developments, potential, and applicability of HBM within the context of integrated environmental health impact assessment. This study covers three main topics that provide guidance for improved interpretation and application of HBM data: (1) sample collection and storage, (2) sample measurement, and (3) data interpretation. These main issues were discussed for 15 of the most common or relevant (classes of) chemicals. For more detailed information, the reader is pointed to the unabridged review (INTARESE, 2007), and consultation is available through the INTARESE web site (www.intarese.org).

Improved electronic interfaces for AT-cut quartz crystal microbalance sensors under variable damping and parallel capacitance conditions

A new configuration of automatic capacitance compensation (ACC) technique based on an oscillatorlike working interface, which permits the tracking of the series resonant frequency and the monitoring of the motional resistance and the parallel capacitance of a thickness-shear mode quartz crystal microbalance sensor, is introduced. The new configuration permits an easier calibration of the system which, in principle, improves the accuracy. Experimental results are reported with 9 and 10 MHz crystals in liquids with different parallel capacitances which demonstrate the effectiveness of the capacitance compensation. Some frequency deviations from the exact series resonant frequency, measured by an impedance analyzer, are explained by the specific nonideal behavior of the circuit components. A tentative approach is proposed to solve this problem that is also common to previous ACC systems.

A Review of Interface Electronic Systems for AT-cut Quartz Crystal Microbalance Applications in Liquids

From the first applications of AT-cut quartz crystals as sensors in solutions more than 20 years ago, the so-called quartz crystal microbalance (QCM) sensor is becoming into a good alternative analytical method in a great deal of applications such as biosensors, analysis of biomolecular interactions, study of bacterial adhesion at specific interfaces, pathogen and microorganism detection, study of polymer film-biomolecule or cell-substrate interactions, immunosensors and an extensive use in fluids and polymer characterization and electrochemical applications among others. The appropriate evaluation of this analytical method requires recognizing the different steps involved and to be conscious of their importance and limitations. The first step involved in a QCM system is the accurate and appropriate characterization of the sensor in relation to the specific application. The use of the piezoelectric sensor in contact with solutions strongly affects its behavior and appropriate electronic interfaces must be used for an adequate sensor characterization. Systems based on different principles and techniques have been implemented during the last 25 years. The interface selection for the specific application is important and its limitations must be known to be conscious of its suitability, and for avoiding the possible error propagation in the interpretation of results. This article presents a comprehensive overview of the different techniques used for AT-cut quartz crystal microbalance in in-solution applications, which are based on the following principles: network or impedance analyzers, decay methods, oscillators and lock-in techniques. The electronic interfaces based on oscillators and phase-locked techniques are treated in detail, with the description of different configurations, since these techniques are the most used in applications for detection of analytes in solutions, and in those where a fast sensor response is necessary.

Gel-based immunoassay for non-instrumental detection of pyrene in water samples

A new qualitative immunologically based tube test for non-instrumental detection of pyrene (PYR) in water samples was developed. The method combines the pre-concentration of analyte by immunoextraction and its detection by immunoassay using Sepharose 4B-immobilized IgG-fraction of a polyclonal anti-PYR antiserum (immunoaffinity gel) and 1-pyrenebutyric acid-horseradish peroxidase conjugate (PYR-BA-HRP). The immunoaffinity gel was placed in a standard 1-ml SPE column through which a 10-ml aliquot of water sample spiked with 10% acetonitrile was passed. Following, free antibody binding sites were detected by application of PYR-BA-HRP. Four minutes after addition of the chromogenic substrate the results were visually evaluated by occurring or stayed away blue colour development for negative and positive samples, respectively. Total time for assay was about 15 min for six samples. Under optimized conditions a cut-off level for pyrene of 0.04 ng ml(-1) was found. At this defined concentration, a set of spiked samples (n=175) was analyzed and very low rates of false negatives (1.2%) and false positives (4.6%) determined which fulfils the requirement set by Commission Decision 2002/657/EC for a screening method. No interference by other PAH compounds like naphthalene, fluoranthene, phenanthrene, anthracene, and benzo[a]pyrene at a concentration of 20 ng ml(-1), i.e., 500-fold excess compared to the defined cut-off level was observed. Different water types like surface water, tap water, bottled water, and melted snow were analyzed for PYR contamination by the proposed method and results confirmed by HPLC-FLD.

Polycyclic aromatic hydrocarbons in sediments from Rodrigo de Freitas Lagoon in the urban area of Rio de Janeiro, Brasil

Regular (non-alkylated) polycyclic aromatic hydrocarbons (PAHs) and their alkylated homologues were determined in sediments from Rodrigo de Freitas Lagoon using gas chromatography with mass selective detector (GC-MSD). Concentrations varying from 405 to 11734 ng x g(-1) were found for total PAHs (regular and alkylated homologues). The study showed a pyrogenic and petrogenic contribution, probably due to the incomplete burning of fossil fuels as a result of the intense traffic of boats and motor vehicles added to the anthropogenic activity of several gas stations present in the region of Rodrigo de Freitas Lagoon. According to the National Oceanic and Atmospheric Administration (NOAA) Sediment Quality Guide, PAHs concentration should not exceed 4000 ng x g(-1) (Long et al., 1995) The obtained data present values above the NOAA limit for some sampling points indicating chronic contamination of those sites probably due to anthropogenic activities related to petroleum and its derivatives.

A survey of the 2001 to 2005 quartz crystal microbalance biosensor literature: applications of acoustic physics to the analysis of biomolecular interactions

The widespread exploitation of biosensors in the analysis of molecular recognition has its origins in the mid-1990s following the release of commercial systems based on surface plasmon resonance (SPR). More recently, platforms based on piezoelectric acoustic sensors (principally 'bulk acoustic wave' (BAW), 'thickness shear mode' (TSM) sensors or 'quartz crystal microbalances' (QCM)), have been released that are driving the publication of a large number of papers analysing binding specificities, affinities, kinetics and conformational changes associated with a molecular recognition event. This article highlights salient theoretical and practical aspects of the technologies that underpin acoustic analysis, then reviews exemplary papers in key application areas involving small molecular weight ligands, carbohydrates, proteins, nucleic acids, viruses, bacteria, cells and lipidic and polymeric interfaces. Key differentiators between optical and acoustic sensing modalities are also reviewed.

Sensor technology and its application in environmental analysis

Environmental analysis is one of the fundamental applications of chemical sensors. In this review we describe different sensor systems for the gas and liquid phases that have been tested either with real-life samples or in the field during the last five years. Most field sensors rely either on electrochemical or optical transducers. In the gas phase, systems have been proposed for analysis of oxides of nitrogen, carbon, and sulfur in air, and volatile organic compounds. In the liquid phase, most detection systems used for real-life samples detect heavy-metal ions or organic contamination, for example pesticides, organic solvents and polycyclic aromatic hydrocarbons.

An immunosensor for ferritin based on agarose hydrogel

A novel electrochemical immunosensor for determination of ferritin in serum has been proposed. The immunosensor was prepared by immobilizing ferritin antibody (FeAb) on a glassy carbon electrode (GCE) based on agarose hydrogel. The modification procedure of the immunosensor was characterized by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The effects of amount of FeAb, incubation time and temperature on the immunosensor were explored to provide optimum analytical performance. The determination of ferritin was based on the change in DPV response before and after the antibody (Ab)-antigen (Ag) reaction. Tests result indicated that FeAb in the device microenvironment had biological activity. The detection limit for ferritin was 1.5 x 10(-5) g l(-1) and the linear range was 5-50 x 10(-5) g l(-1) with a correlation coefficient of 0.996. The storage stability was acceptable in pH 7.0 phosphate buffer saline (PBS) solution at 4 degrees C for 10 days. The proposed immunosensor provides a new promising method for the clinical immunoassay of ferritin.

Preconcentration and fluorimetric determination of polycyclic aromatic hydrocarbons based on the acid-induced cloud-point extraction with sodium dodecylsulfate

The acid-induced cloud-point extraction (CPE) technique based on sodium dodecylsulfate (SDS) micelles has been used for preconcentration of ten representatives of polycyclic aromatic hydrocarbons (PAHs) for the following fluorescence determination. The effect of the acidity of solution, SDS and electrolyte concentrations, centrifugation time and rate on the two-phase separation process and extraction percentages of PAHs have systematically been examined. Extraction percentages have been obtained for all PAHs after CPE ranged from 67 to 93%. Pyrene was used as a fluorescent probe to monitor the micropolarity of the surfactant-rich phase compared with SDS micelles and this allows one to conclude that water content in micellar phase after CPE is reduced. The spectral, metrological and analytical characteristics of PAH fluorimetric determination after acid-based CPE with sodium dodecylsulfate are presented. Advantages provided by using CPE in combination with fluorimetric determination of PAHs are discussed. The determination of benz[a]pyrene in tap water is presented as an example.

Electrochemical and chemiluminescent immunosensors for tumor markers

The determination of serum tumor markers plays an important role in clinical diagnoses for the patients with certain tumor-associated disease. Although many commercial kits have been applied in clinical immunoassays, conventional methods always have some disadvantages, resulting in the need of other new, efficient, and easily automated methods. Immunosensors, considered as a major development in immunochemical field, have attracted considerable attention. With the aim of rapid screening, many immunosensors that are small, semi-automated and portable are being developed. This brief review focuses on the current research of immunosensors for tumor markers based on the electrochemical and chemiluminescent detection with emphasis on recent advances, challenges, and trends. The works on series of novel immunosensors developed for the determination of tumor markers in our group in the last few years are also introduced.

Development of a highly sensitive monoclonal antibody based ELISA for detection of benzo[a]pyrene in potable water

In Europe, a limit value of 10 ng L(-1) was set by the European Commission for benzo[a]pyrene (B[a]P) in water intended for human consumption (Council Directive 98/83/EC) and, therefore, sensitive and reliable methods are needed to evaluate its presence. We report here on the development of a highly sensitive indirect competitive ELISA for the detection of B[a]P in potable water. Fourteen monoclonal antibodies were generated in mice using novel B[a]P derivatives. The immunoassay with the least interference and the best sensitivity was optimized and characterized. As co-solvent, ten percent methanol (v/v) was determined as the optimum concentration for B[a]P solubilization for use with the developed ELISA. With the purified antibody (clone 22F12) the average IC50 for B[a]P and corresponding detection limit at a signal:noise (S/N) ratio of 3 was 65 ng L(-1) and 24 ng L(-1), respectively. From the 16 EPA-designated PAHs, only chrysene, indeno[1,2,3-cd]pyrene, and benzo[b]fluoranthene showed a cross-reactivity (CR) higher than 20%. No CR was observed for two- and three-ringed aromatics as well as dibenz[ah]anthracene and benzo[ghi]perylene. The effect of pH value (range 6.5-9.5), ionic strength (specific electric conductivity 1 microS cm(-1)-2.5 mS cm(-1)), and inorganic ions (sodium, copper, iron, aluminium, manganese, chloride, sulfate, nitrate, and nitrite at maximum permissible levels according to the Council Directive) on both signal and sensitivity of the ELISA was studied. No significant influence of these parameters on the ELISA competition curve was found. We suggest that the optimized ELISA can be used to monitor potable water samples without previous extraction from the samples. The assay should facilitate the cleanup of B[a]P contaminated sites where B[a]P levels fall close to the limit value of the new drinking water directive.

Immunological assay for carbohydrate antigen 19-9 using an electrochemical immunosensor and antigen immobilization in titania sol–gel matrix

We describe a novel electrochemical immunosensor for carbohydrate antigen 19-9 (CA19-9) based on the immobilization of CA19-9 with titania sol-gel on a graphite electrode (GE) by vapor deposition. The CA19-9 membrane was characterized using scanning electron microscopy and proved to be chemically clean, porous and homogeneous. The incubation of the immunosensor in a solution containing horseradish peroxidase (HRP)-labeled CA19-9 antibody led to the binding of HRP-labeled antibody with the immobilized antigen. The immobilized HRP catalyzed the oxidation of catechol by H(2)O(2) and this provided a competitive method for the measurement of serum CA19-9. The response current decreased with increasing CA19-9 concentration in the incubation solution. The effects of pH, amount of HRP-labeled antibody, incubation time and temperature were explored to provide optimum analytical performance. Under optimal conditions, the current decrease of the immunosensor was proportional to CA19-9 concentrations in the range of 3-20 U/ml with a detection limit of 2.68 U/ml at a current decrease of 10%. The detection of CA19-9 in two serum samples obtained from clinically diagnosed patients with pancreatic carcinoma showed acceptable accuracy. The proposed immunosensor provides a new promising tool for the clinical immunoassay of CA19-9.

Reagentless Amperometric Immunosensors Based on Direct Electrochemistry of Horseradish Peroxidase for Determination of Carcinoma Antigen-125

A novel strategy for immunoassay and the preparation of reagentless immunosensors was proposed. This strategy was based on the immobilization of antigen and the direct electrochemistry of horseradish peroxidase (HRP) that was labeled to an antibody. A reagentless immunosensor for carcinoma antigen-125 (CA 125) determination was developed. The immunosensor was prepared by immobilizing CA 125 with titania sol-gel on a glassy carbon electrode by the vapor deposition method. The incubation of the immunosensor in phosphate buffer solution (PBS) including HRP-labeled CA 125 antibody led to the formation of a HRP-modified surface. The immobilized HRP displayed its direct electrochemistry with a rate constant of 3.04 +/- 1.21 s(-1). With a competition mechanism, a differential pulse voltammetric determination method for CA 125 was established by the peak current decrease of the immobilized HRP. The current decrease resulted from the competitive binding of the CA 125 in sample solution and the immobilized CA 125 to the limited amount of HRP-labeled CA 125 antibody. Under optimal conditions, the current decrease was proportional to CA 125 concentration ranging from 2 to 14 units mL(-1) with a detection limit of 1.29 units mL(-1) at a current decrease by 10%. The CA 125 immunosensor showed good accuracy and acceptable precision and fabrication reproducibility with intraassay CVs of 8.7 and 5.5% at 8 and 14 units mL(-1) CA 125 concentrations, respectively, and interassay CV of 19.8% at 8 units mL(-1). The storage stability was acceptable in a pH 7.0 PBS at 4 degrees C for 15 days. The proposed method provided a new promising platform for clinical immunoassay.