Andrea Ravalli

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

BackgroundThe 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.ResultsHere, 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.ConclusionsAlthough 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.

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.

Polyaniline Modified Thin-film Array for Sensor Applications

In this work, a pH sensor based on polyaniline-modified thin-film interdigitated array (IDA) microelectrodes was presented. Aniline was electropolymerized on the surface of IDA working electrodes by means of cyclic voltammetry. Scanning electron microscope and electrochemical measurements were used to characterize the polyaniline-modified sensor surface. Electrochemical impedance spectroscopy (EIS) was finally used to determinate the variation of pH in [Fe(CN)6]3−/4− solutions.

Fish Robot Based on Chemical Sensors for Water Monitoring

In this work, we present a bio-inspired fish robot capable of swimming according to the directives sent in form of chemical messengers. An electrochemical platform measured the hydrogen concentration in the water. The acquired signal was then transformed into electronic signal to be used in robot control electronics. The fish robot’s tail movement was thus controlled from pH electrochemical sensors.

Electrochemical and Photoelectrochemical Biosensors for Biomarker Detection

A rapid and accurate medical diagnosis is essential in order to determine the health status of a patient. Nowadays, most of the clinical analyses are performed in specialized laboratory, which required specific instrumentation and trained personal, resulting in an increase of analysis costs and time. In this context, biosensors represent ideal tools capable to provide a specific and fast response together with low cost, easy use and portable size features. This work attempts to provide a review of the research progresses of electrochemical and photoelectrochemical biosensor platforms in clinical applications that have been published in recent years. Special emphasis will be devoted to discuss examples for breast cancer biomarker detection, because breast cancer, is considered the leading cause of cancer-related deaths worldwide in women, representing 15% of all cancer related amongst women, with a 6% mortality rate (based on overall cancer deaths). The manuscript is focused on aptamer-based biosensors, because, due to their stability and their relatively low cost, they have been successfully applied in many biosensor formats for breast cancer biomarker detection.

Electrochemical Immunoassay for Mucin 1 Detection as a Diagnostic Tool in Ovarian Cancer

The immunoassay developed for Mucin 1 (MUC1) detection is based on a sandwich format in which a primary antibody immobilized on the surface of magnetic beads specifically binds the MUC1 protein. The sandwich immunoassay is performed by adding secondary anti-MUC1 and an alkaline-phosphatase-labeled third antibody. After, the modified magnetic beads are captured by a magnet on the surface of a graphite working electrode, and the electrochemical detection is thus achieved through the addition of 1-naphthyl phosphate. 1-naphthol, produced during the enzymatic reaction, is detected using differential pulse voltammetry (DPV). The performance of the assay in terms of sensitivity, reproducibility, and selectivity has been studied. MUC1 detection is performed in buffered solutions and serum sample.

Electrochemical Antibody-Aptamer Assay for VEGF Cancer Biomarker Detection

In this work, a simple and sensitive approach for VEGF detection using antibody-aptamer assay and gold screen-printed electrodes as transducers is presented. The assay was performed in a sandwich format. Anti-VEGF antibody was first chemically immobilized on the gold working electrode surface of screen-printed cell. After the incubation with the antigen, the sandwich assay was realized by incubation step with biotinylated anti-VEGF aptamer. The sensor was then incubated with streptavidin-alkaline phosphatase and with 1-naphthyl phosphate. Differential pulse voltammetry (DPV) measurements were performed to detect VEGF biomarker.