Biosensors & Bioelectronics

Screen-printing (thick-film) technology is well identified as a reliable technique for fabrication of electrodes which can be used as transducer in biosensor, with several advantages including low cost, design flexibility, process automation, good reproducibility and a wide choice of materials. However, the immobilization of antibody molecules is a decisive factor for successful fabrication of immunosensors. Besides, the ability to measure human Chorionic Gonadotropin (hCG) is important in establishing the diagnosis of gestational trophoblastic disease and germ cell tumors. Moreover, Electrochemical Impedance Spectroscopy (EIS) recently has been being chosen as a main detection method because it is label-free, less destructive to the activities of biomolecule and very sensitive with comparable detection limits as optical-based sensor. In this work, a sensitive label-free impedimetric hCG-immunosensor was constructed by using a commercial screen-printing carbon ink electrode (namely Disposable Electrochemical Printed chip) as a basis. The hCG antibody was immobilized via the entrapment technique on the carbon ink electrode of DEP chip using functional molecule, 1-pyrenebutanoic acid, succinimidyl ester. The experimental results exposed that the designed immunosensor is more sensitive than other previously reported immunosensors, in the case of detection limit and linear range for antigen detection. With optimal fabrication parameters, the detection limit for ?-hCG was 33 pg/mL in 10mM phosphate buffer saline (PBS) solution containing 1% bovine serum albumine (BSA). Furthermore, the use of inexpensive DEP chip as a basis for these immunosensors will allow simple instrumentation, disposable and portable at low cost. This work also demonstrates a new approach to develop a sensitive and labelfree impedimetric immunosensor based on screen-printed electrode for applications in clinical diagnosis.

Photoacoustic imaging, also referred to optoacoustic imaging, is an emerging optical imaging technique that is capable of providing both structural and functional optical information of tissues up to several centimeters deep with scalable ultrasound resolution. The combination of ultrasound spatial resolution and intrinsic rich optical contrast in cancer / inflammatory tissues allow photoacoustic imaging a promising early detection tool in diagnostic medicine. At the same time, the availability of various optical absorbing nanostructures extensively studied in targeted drug delivery extends the capability of photoacoustic imaging to theranostic medicine, where functionalized nanostructures provide photoacoustic imaging contrast and targeting moieties / drug carrier for targeted drug delivery. In this paper, we provide a review of the photoacoustic imaging technique for studies in diagnostic and theranostic medicine. The technical consideration for photoacoustic imaging systems and reconstruction algorithms of structural / quantitative photoacoustic imaging have been introduced. A review of the photoacoustic imaging in breast cancer detection and osteoarthritis evaluation is included in the section of photoacoustic applications in diagnostic medicine, where patient subjects have been already recruited and photoacoustically evaluated. At the end of this paper, a brief review of optical controlled drug release and photoacoustic evaluation is presented as a view to the effort of combining laser induced photoacoustic imaging with laser controlled drug delivery / release in theranostic medicine.

The potentiometric cholesterol biosensor based on graphene nanosheets has been successfully miniaturized. Homogeneous exfoliation of the mono- and double-layered graphene nanosheets on copper wire is achieved by drop casting the graphene nanosheets suspended in N-methyl-pyrrolidone solution. The process of physical adsorption has been utilized to immobilize the cholesterol oxidase onto graphene nanosheets. Morphological, crosssectional and structural crystallinity of the nanosheets have been investigated using atomic force microscope and transmission electron microscope. Ultraviolet-visible absorption and Fourier transform infrared spectrometers have been used to confirm the presence of the graphene nanosheets and their conjugation with cholesterol oxidase. The presented potentiometric biosensor renders effective selectivity and sensitivity (~82 mV/decade) for the detection of cholesterol biomolecules in 1 × 10−6 M to 1 × 10−3 M logarithmic range and quick output response within ~ 4 sec. The stability and reusability of the biosensor have also been investigated for the above mentioned range of cholesterol concentrations. Additionally, the functioning of presented biosensor is studied for the ranges of the temperature of 15-70 °C and pH values (4-9).

In this present research, we have grown the well aligned, perpendicular to the substrate and highly dense ZnO nanorods on the gold coated substrate by using the hydrothermal growth method. The ZnO nanorods were functionalized by immobilizing the ascorbate oxidase enzyme with cross linking molecule 3-glycidoxypropy1trimethoxysilane (GPTS).The electrochemical measurements were carried out through using potentiometric technique, we observed that the output response exhibited by the biosensor to the wide linear dynamic range concentration of L-ascorbic acid from 1×10 -6 to 5×10 -2 M with good sensitivity of 32 mV/decade. Moreover the biosensor showed excellent fast response time less than 10 seconds, better selectivity, repeatability, reproducibility and no significant interference to the common interfering ions such as potassium K +1 , sodium ions Na +1 , calcium ions Ca +2 , glucose, fructose, and zinc ions Zn +2 etc. except slight interference with copper Cu +2 ions.