Development of a novel DNA chip based on a bipolar semiconductor microchip system

Time-lapse contact microscopy of cell cultures based on non-coherent illumination

Video microscopy offers outstanding capabilities to investigate the dynamics of biological and pathological mechanisms in optimal culture conditions. Contact imaging is one of the simplest imaging architectures to digitally record images of cells due to the absence of any objective between the sample and the image sensor. However, in the framework of in-line holography, other optical components, e.g., an optical filter or a pinhole, are placed underneath the light source in order to illuminate the cells with a coherent or quasi-coherent incident light. In this study, we demonstrate that contact imaging with an incident light of both limited temporal and spatial coherences can be achieved with sufficiently high quality for most applications in cell biology, including monitoring of cell sedimentation, rolling, adhesion, spreading, proliferation, motility, death and detachment. Patterns of cells were recorded at various distances between 0 and 1000 μm from the pixel array of the image sensors. Cells in suspension, just deposited or at mitosis focalise light into photonic nanojets which can be visualised by contact imaging. Light refraction by cells significantly varies during the adhesion process, the cell cycle and among the cell population in connection with every modification in the tridimensional morphology of a cell.

Interdigitated microelectrode array-coupled bipolar semiconductor photodiode array (IMEA-PDA) microchip for on-chip electrochemiluminescence detection

This paper reports the design, fabrication and testing of a microchip wherein interdigitated microelectrode arrays (IMEA) were integrated with bipolar semiconductor photodiode array (PDA) chip to fabricate a highly compact embodiment for on-chip handling of solutions and electrochemiluminescence (ECL) detection. A 12 x 12 micro array of photodiodes, each coupled with an interdigitated microelectrode array (IMEA), an array of current amplifiers, and a photodiode element-addressing circuit were integrated into a single 2 x 2 cm² IC chip. Each photodiode had dimensions of 300 x 300 μm² and the photodiode-to-photodiode distance was 100 μm. The chip was successfully applied to the on-chip quantification of electro-chemiluminescing probe-labeled single stranded oligonucleotides. The minimum detectable limit at signal/noise ≥ 3 was found to be 5 x 10⁻¹⁴ moles of oligonucleotides with a sample volume as low as 5 microl (i.e., 10 fmole/μl). The attractive features of the developed IMEA-PDA microchip are that a plurality of samples can be analyzed simultaneously using a chip and that for a given sample the data can be averaged from values obtained from multiple, individually addressed pixels. These in turn bring in speed and statistical confidence in analysis. The IMEA-PDA microchip system has the potential to be used as a versatile and highly compact chemical analysis tool for chemical sensing and metrology applications.

Photodiode array on-chip biosensor for the detection of E. coli O157:H7 pathogenic bacteria

An integrated circuit (IC) of photodiode array (PDA) microchip system was used for the on-chip detection of E. coli O157:H7 based on an enzymatic bioassay and light absorption property of the reaction product. The PDA microchip consisting of an array of 12 x 12 photodiode detection elements served as a photosensor as well as a protein-immobilizing sample platform. As a result, E. coli O157:H7 could be detected directly on the surface of PDA detection elements. E. coli O157:H7 was detected by forming a "sandwich-type" enzymatic immunocomplex on the PDA detection elements using an on-chip bioassay. The quantitative analysis of E. coli O157:H7 immunocomplex was carried out based on the light absorption property of the enzymatic reaction products of E. coli O157:H7 immunocomplexes with respect to a red beam produced by light emitting diodes (LEDs) installed right above the PDA microchip. During the on-chip bioassay, the wet photodiode detection elements exposed to a lot of biological materials or buffer solutions were capable of maintaining their photosensing capabilities. The portable PDA on-chip biosensor permits direct optical detection of E. coli O157:H7 and eliminates the necessity of the conventional expensive microplate reader that is incompatible with the size of the protein microarray.

An automated method for in vitro anticancer drug efficacy monitoring based on cell viability measurement using a portable photodiode array chip

An integrated circuit (IC) bipolar semiconductor photodiode array (PDA) microchip system coupled with light emitting diodes (LEDs) was used for rapid, automated cell viability measurements and high-throughput drug efficacy monitoring. Using the absorption property of trypan blue dye against the red light emitted by LEDs, we determined the effect of three anticancer drugs, viz., camptothecin (CAM), sodium salicylate (Na-Sal) and naringenin (Nar) on the cell viability of human promyelocytic leukemia cells (HL-60) and human embryonic kidney cells (HEK-293). Cell viabilities were measured based on the relative reduction in the photo responses of the photodiodes, covered with known concentration of trypan blue-stained cells. The developed method offers greater sensitivity and hence an excellent estimation of cell viability, but without all the hassle of conventional methods. Flow cytometric measurement and confocal microscopy were applied as complementary techniques for further validation of the results. The work presented here has important implications with regard to high-throughput measurement of optimal concentrations of different drugs against different cell lines in vitro.

Low noise bipolar photodiode array protein chip based on on-chip bioassay for the detection of E. coli O157:H7

A bipolar photodiode array (PDA) protein chip is presented for the detection of E. coli O157:H7. Through unique design of the bipolar PDA microchip, the device was able to detect E. coli O157:H7 directly on the surface of the bipolar PDA. The bipolar PDA microchip maintained low noise level in the entire process of on-chip protein assay and demonstrated high performance of analog signal processing. At every reaction step of the on-chip bioassay, stability of wet photodiode detection elements was confirmed by monitoring the variance of their photosignals with respect to the irradiated red beam. The background signal represented less than 1.8% variance with respect to maximum signal of photodiode detection elements. As a result of using the on-chip bioassay, any complicated optical alignment and components could be removed in the constructed protein chip. This protein chip enables direct optical detection of E. coli O157:H7 eliminating the need of conventional expensive microplate reader that is incompatible with size of sampling platform of protein chip. The independence of the constructed protein chip on conventional microplate reader can contribute greatly to further miniaturization of protein chip and field usable lab-on-a-chip.