Procedia Technology最新文献

We present a signal amplification method for biosensing applications using magnetic particles. In this method, mobile devices and simple spherical glass beads are used as a low-cost microscope to detect magnetic particles. Magnetic particles have two main functions; 1) conventionally capture, separate and transport target molecules 2) form magnetic dipoles under an applied external magnetic field to attract other magnetized particles. When magnetic particles accumulate and form a cluster, the corresponding pixel area in the image taken by the simple microscope is increased resulting in signal amplification.

Current focus of new generation biosensor research is to increase the sensitivity levels of the devices to compete with current lab analysis tools while inherently having other advantages such as being low-cost, portable and simple. Biosensors based on micro/nano magnetic particles use various measurement techniques and amplification methods. In order to fully benefit from the advantages of micro/nano technology based systems, measurement set up must be also portable and have high sensitivity. Mobile devices and applications are taking place in medical fields and have high potential for future. In this work mobile devices are employed as measurement setups for the magnetic particle based sensing and signal amplification. The amplification method is not based on bimolecular binding thus cost efficient. After the images of the magnetic particles are taken, these images are sent to cloud computing for analysis by the mobile device. Matlab codes run on cloud servers for processing the images. Finally results are received and displayed on the mobile device.

The mobile device based imaging system is able to detect 7 μm size particles within a 1500 μm x1500 μm area and magnetic bead accumulation resulted in at least 5-fold signal amplification. The applied magnetic field is approximately 15 mT and the cost of the system excluding mobile device is under 20 cents. The method is promising for immunomagnetic bead assisted biosensors.

An easy to implement immunoassay for rapid dengue virus (DENV) serotype diagnosis in the early infection stage is reported. The four-layer assay is immobilized onto a thin gold film and relies on a polymer biochip for optical surface plasmon resonance sensing and detection. The protocol comprises Neutravidin-Biotin mediated DENV monoclonal antibody (MAB_D) attachment as the functionalized sensing element. The MAB_D-DENV complex formation results in a pronounced thickness change that is optically detected in real time. The protocol is applicable in presence of strong non-specific binding interference. False positive indications for negative serum and blood control samples were not observed. The method can be modified towards detection of other viruses infections.

The innovative photoelectrochemical properties of multifunctional nanomaterials are here investigated for the development of biosensing platforms for rapid and sensitive detection of a class of cancer biomarker candidates, known as microRNAs. Many different transducers have been proposed, so far, for microRNA detection. Recently, with the emergence of novel photoelectrochemically active species and new detection schemes, photoelectrochemistry has received increasing attention. Gold nanostructures have been, here, used to modify TiO₂ electrodes. The surface of the nanostructured platform has been modified by nucleic acid capture probes (CPs). Biotinylated target miRNAs have been recognized by the specific CPs. The biosensing platform has been incubated with streptavidin alkaline phosphatase and exposed to a proper substrate. The product of the enzymatic reaction has been photoelectrochemically monitored. A compact and hand-held analytical device has been developed in order to have a final prototype in line with the concept of point of care testing.

This paper presents a homemade miniature surface plasmon resonance (SPR) system with automatic sample injection device which is able to work 24 hours unattended. The system with a volume of 48cm×25cm×28 cm was constructed with a red laser light source, a P-polarizer, a triangle glass prism, a linear CCD detector, gold sensor chips modified with BSA or colloidal gold, an automatic sample injection device with 20 sample locations. The system sensitivity and noise were tested through detecting different concentration of glycerol solutions with a group of refractive indices (RIs). Cortisol-BSA was fixed on the gold sensor chips modified with BSA or colloidal gold. A series concentration of cortisol (1, 10, 100, 1000 ng/ml) mixed with cortisol-specific monoclonal antibodies were detected by miniature SPR system. The performance of BSA and colloidal gold modified sensor chips were compared by calculating the standard curves and the kinetic curves of the cortisol detection. The results showed that the BSA sensor chip could get a better detection limit of cortisol sample while the colloidal gold sensor chip owed a higher stability and repeatability by regenerating the antibody surface. The research studied the performance of the homemade SPR system and the sensor chips which could be widely used in the protein measurement areas.

Innovations in ultra low-light CMOS bio-optical sensor design, combined with microfluidics technology can enable a new generation of low cost, portable molecular diagnostics platforms. This combination of technologies have been applied successfully in a miniaturized qPCR system, and a chemiluminescence microfluidic immunoassay platform to detect a variety of infectious pathogens. Cost reduction and miniaturization of molecular test enabled by this technology will have positive impact on global battle against infectious diseases.

Electrochemical protein digestion prior to mass spectrometric analysis is a purely instrumental approach to protein identification, offering reduced consumption of chemicals and shorter analysis times compared to the use of enzymes and chemical cleavage agents. Here we demonstrate the possibilities of site-specific peptide bond cleavage and disulphide bond reduction in a microfluidic electrochemical cell. The use of microfluidics in this context is beneficial for increased electrochemical cleavage yields, small sample volumes and the possibility of rapid on-line analysis, thereby providing a versatile tool for routine proteomics studies.

The present work illustrates the construction and application of bismuth-silver bimetallic nanoparticles (Bi-AgNPs) in biosensor construction for the detection of peroxide (H₂O₂). The biosensor was constructed by drop-casting of horseradish peroxidase onto the Bi-AgNPs/GCE sensor. Impedance analysis revealed that the R_ct value for the bare GCE obtained was 2.548 × 10³ Ω and increased to 5.768 × 10³ Ω for the HRP/Bi-AgNPs/GCE biosensor. This increased value of R_ct indicated hindrance to the electron transfer, providing evidence for the immobilization of insulating HRP on the Bi-AgNPs/GCE surface. The HRP/Bi-AgNPs/GCE biosensor was successfully applied for sensitive detection of H₂O₂ by differential pulse voltammetry. Well defined peaks were observed with a low linearity range from 0.02 × 10⁻⁶ to 1.0 × 10⁻⁶ M (R² = 0.991), with a limit of detection of 0.06 μM. The results obtained for the HRP/Bi-AgNPs/GCE biosensor compared well within the range of similar biosensors reported.