Colorimetric multienzymatic smart sensors for hydrogen peroxide, glucose and catechol screening analysis.

In this work, we present a smartphone-based multiplexed enzymatic biosensor utilizing the unique colorimetric properties of the poly(aniline-co-anthranilic acid) (ANI-co-AA) composite film coupled with horseradish peroxidase (HRP), glucose oxidase (GOx), horseradish peroxidase-glucose oxidase (GOx-HRP) and tyrosinase (Tyr) enzymes. The enzymes are immobilized on the composite polymer film by adsorption and they catalyze a reversible redox color change of the host polymer from green to blue in the presence of their substrate. A smartphone was applied as color detector, for image acquisition and data handling. A ColorLab® android application, free of charge software application, was used to enable easy and clear display of the sensors' response indicating remarkable changes in the optical features. The results were confirmed by the spectrophotometric measurements. The developed colorimetric enzymatic biosensors were studied and optimized in relation to different experimental parameters. Moreover, the colorimetric enzymatic biosensors were applied to food and pharmaceutical analysis. It has been shown by these studies that the colorimetric biosensors are promising as quick and simple tests for handheld analysis in various fields.

Smartphone-based immunosensor for CA125 detection.

In this work, we report the design, the development and the characterization of the analytical performances of a colorimetric smartphone-based immunosensor for the detection of cancer antigen 125 (CA125). The immunosensor was based on a sandwich strategy in which the primary antibody was immobilized by spotting onto the 3D nitrocellulose membrane. The immunospots were subsequently incubated with CA125 solutions, followed by the affinity reaction with a secondary antibody labeled with gold nanoparticles (AuNPs). The antibody-AuNPs captured onto immunospots induced the silver deposition from a silver enhancer solution leading to the formation of gold-silver nanoparticles of different grey color spots depending on CA125 concentration. The 8 megapixels smartphone camera was integrated in a home-made dark box and used as transducer of color image acquisition and data handling. The pixel intensity of the captured images was determined by an image processing algorithm. The experimental parameters involved in each step of the immunosensor design were studied and optimized, obtaining a limit of detection of 30U/mL CA125. The selectivity of the immunoassay was proven against different concentration solutions of Vascular Endothelial Growth Factor (VEGF) antigen as an unspecific protein when a blank signal was obtained for all tested solutions. Finally, preliminary experiments in human serum samples spiked with CA125 protein were also performed. Therefore, the proposed system could represent a powerful point-of-care tool for the next generation technology for detecting and monitoring cancer biomarkers at early stages by taking advantage of nowadays gadgets with enhanced features such as smartphones.

Electrochemical, Electrochemiluminescence, and Photoelectrochemical Aptamer-Based Nanostructured Sensors for Biomarker Analysis.

Aptamer-based sensors have been intensively investigated as potential analytical tools in clinical analysis providing the desired portability, fast response, sensitivity, and specificity, in addition to lower cost and simplicity versus conventional methods. The aim of this review, without pretending to be exhaustive, is to give the readers an overview of recent important achievements about electrochemical, electrochemiluminescence, and photoelectrochemical aptasensors for the protein biomarker determination, mainly cancer related biomarkers, by selected recent publications. Special emphasis is placed on nanostructured-based aptasensors, which show a substantial improvement of the analytical performances.

Micro-flow Immunosensor Based on Thin-film Interdigitated Gold Array Microelectrodes for Cancer Biomarker Detection.

In this paper, we reported the development of a micro-flow label-free impedimetric biosensor based on the use of thin-film interdigitated gold array microelectrodes (IDA) for the detection of carbohydrate antigen 125 (CA125). The immunosensor is developed through the electropolymerization of anthranilic acid (AA) on the surface of IDA electrodes followed by the covalent attachment of anti-CA125 monoclonal antibody. CA125 protein affinity reaction was then evaluated by means of electrochemical impedance spectroscopy (EIS). The sensor was characterized by electrochemical techniques and scanning electron microscopy (SEM). Using the optimized experimental conditions, the developed immunosensor showed a good analytical performance for CA125 detection from 0 to 100 U/mL with estimated limit of detection (LOD = 3Sblank/Slope) of 7 U/mL.

Gold and Magnetic Nanoparticles-Based Electrochemical Biosensors for Cancer Biomarker Determination.

Detecting cancer at early stage is one of the most important factors associated with the increase of the survival rate of the patients. Cancer biomarkers are able to detect a specific disease early and help to provide treatments before it becomes incurable in later stages. Biomarkers can also be used to determine the recurrence of the disease and to evaluate the follow-up of the patients after a chemio- or radio-therapy and surgery treatments. Electrochemical biosensors are successfully applied for the detection of cancer biomarkers due to their high sensibility, rapid response and low cost. In recent years, the advance in nanotechnology has led to the discovery and the employment of a great number of new materials in nanoscale dimensions. Due to their particular properties, the development of nanostructured biosensors (in particular using gold and magnetic nanoparticles) with high analytical performances increases constantly. In this review recent different strategies for the development of gold and magnetic nanoparticles-based electrochemical biosensors for cancer biomarkers detection were presented.

A label-free electrochemical affisensor for cancer marker detection: The case of HER2.

In this paper, we report the development of a sensitive label-free impedimetric biosensor based on the use of affibody as bioreceptor and gold nanostructured screen-printed graphite as a sensor platform for the detection of human epidermal growth factor receptor 2 (HER2). The affisensor is realized by immobilizing a terminal cysteine-modified affibody on gold nanoparticles. The sensor was characterized by electrochemical techniques and scanning electron microscopy (SEM). Furthermore, surface plasmon resonance (SPR) technology was also applied to explore the potential of affibodies as small-molecule discriminating tools. Using optimized experimental conditions, a single-use affisensor showed a good analytical performance for HER2 detection from 0 to 40 µg/L. The estimated limit of detection was 6.0 µg/L. Finally, the realized affisensor was applied to human serum samples.

In vitro assessment of antibody-conjugated gold nanorods for systemic injections.

BACKGROUND: The interest for gold nanorods in biomedical optics is driven by their intense absorbance of near infrared light, their biocompatibility and their potential to reach tumors after systemic administration. Examples of applications include the photoacoustic imaging and the photothermal ablation of cancer. In spite of great current efforts, the selective delivery of gold nanorods to tumors through the bloodstream remains a formidable challenge. Their bio-conjugation with targeting units, and in particular with antibodies, is perceived as a hopeful solution, but the complexity of living organisms complicates the identification of possible obstacles along the way to tumors. RESULTS: Here, we present a new model of gold nanorods conjugated with anti-cancer antigen 125 (CA125) antibodies, which exhibit high specificity for ovarian cancer cells. We implement a battery of tests in vitro, in order to simulate major nuisances and predict the feasibility of these particles for intravenous injections. We show that parameters like the competition of free CA125 in the bloodstream, which could saturate the probe before arriving at the tumors, the matrix effect and the interference with erythrocytes and phagocytes are uncritical. CONCLUSIONS: Although some deterioration is detectable, anti-CA125-conjugated gold nanorods retain their functional features after interaction with blood tissue and so represent a powerful candidate to hit ovarian cancer cells.