Xiaoyong Yang

Digital imaging scanning system and biomedical applications for biochips

Biochips have been an advanced technology for biomedical applications since the end of the 20th century. Optical detection systems have been a very important tool in biochip analysis. Microscopes are often inadequate for high resolution and big view-area detection of microarray chips, thus some new optical instruments are required. In this work, a novel digital imaging scanning system with dark-field irradiation is developed for some biomedical applications for microarray chips, characterized by analyzing genes and proteins of clinical samples with high specific, parallel, and nanoliter samples. The novel optical system has a high numerical aperture (NA=0.72), a long working distance (wd>3.0 mm), an excellent contrast and signal-to-noise ratio, a high resolving power close to 3 mum, and an efficiency of collected fluorescence more than two-fold better than that of other commercial confocal biochip scanners. An edge overlap algorithm is proposed for the image restructure of free area detection and correcting scanning position errors to a precision of 1 pixel. A novel algorithm is explored for recognizing the target from the scanning images conveniently, removing noise, and producing the signal matrix of biochip analysis. The digital imaging scanning system is equally as good for the detection of enclosed biochips as it is for the detection of biological samples on a slide surface covered with a glass cover slip or in culture solution. The clinical bacteria identification and serum antibody detection of biochips are described.

Development of a confocal optical system design for molecular imaging applications of biochip

A novel confocal optical system design and a dual laser confocal scanner have been developed to meet the requirements of highly sensitive detection of biomolecules on microarray chips, which is characterized by a long working distance (wd>3.0 mm), high numerical aperture (NA=0.72), and only 3 materials and 7 lenses used. This confocal optical system has a high scanning resolution, an excellent contrast and signal-to-noise ratio, and an efficiency of collected fluorescence of more than 2-fold better than that of other commercial confocal biochip scanners. The scanner is as equally good for the molecular imaging detection of enclosed biochips as for the detection of biological samples on a slide surface covered with a cover-slip glass. Some applications of gene and protein imagings using the dual laser confocal scanner are described.

DETECTION AND APPLICATION OF MICROFLUIDIC ISOTHERMAL AMPLIFICATION ON CHIP

Loop-mediated isothermal amplification (LAMP) is a novel nucleic acid amplification method. Compared with the widely utilized polymerase chain reaction (PCR), LAMP has higher speed and efficiency as well as lower requirement for system temperature control because the whole amplification process is isothermal and no efforts are needed to switch between different temperatures. In this paper, we designed and fabricated different kinds of polycarbonate (PC) microfluid chips, explored appropriate reaction condition for LAMP in microenvironment (1 nL → 10 μL), and developed a microfluidic isothermal amplification detection system. The DNA optimal amplification temperature is obtained; the starting time of exponential amplification of DNA is put forward farther. The optimal condition of DNA amplification in microenvironment, with a little reaction materials and early starting exponential amplification time of DNA are very important for clinic DNA detection and the application of Lab-on-a-Chip.

LABEL-FREE DETECTION OF PROTEIN MICROARRAY WITH HIGH THROUGHPUT SURFACE PLASMON RESONANCE IMAGING (SPRI)

A surface plasmon resonance imaging (SPRI) system was developed for the discrimination of proteins on a gold surface. As a label-free and high-throughput technique, SPRI enables simultaneously monitoring of the biomolecular interactions at low concentrations. We used SPRI as a label-free and parallel method to detect different proteins based on protein microarray. Bovine Serum Albumin (BSA), Casein and Immunoglobulin G (IgG) were immobilized onto the Au surface of a gold-coated glass chip as spots forming a 6 × 6 matrix. These proteins can be discriminated directly by changing the incident angle of light. Excellent reproducibility for label-free detection of protein molecules was achieved. This SPRI platform represents a simple and robust method for performing high-sensitivity detection of protein microarray.

Single Living Cell Imaging and Spectrum Detection

Microscopy is an important tool in biology and medicine, but it is often limited to high numerical aperture (NA) with a short working distance(wd), such as NA = 0.6 then wd < 1 mm. For imaging living cells in culture, a high numerical aperture and long working distance of optical imaging structure is required, and the common microscopy objective is no good here. In order to meet the single living cell imaging, a novel optical design has been performed in this paper, which is character of ultra-long working distance wd = 15 mm and high numerical aperture NA = 0.7. An optical imaging system with dual modes information of fluorescence and spectrum can be developed for the subcellular imaging of cells attached on surface of vessel or free-floating in culture.

A Novel Developed Detection and Analysis Method of DNA Microarray Hybridization Using FRET technique

Fluorescence resonance energy transfer (FRET) is a distance-sensitive energy transfer process which is widely used in probing molecular interaction in the 1-10 nm range. DNA microarray chip technique is a high throughput analysis method in molecular biology research. In this paper, we explored a novel detection and analysis method of DNA microarray hybridization using FRET technique. In our study, TMR dye labeled DNA oligomer was immobilized on the microarray chips and hybridized with complementary DNA oligomer labeled with Cy5 dye. We successfully detected and analysed the FRET signal of the hybridized DNA microarray. The variation of FRET signal intensity and the efficiency of FRET in response to the concentration of the sample were studied.

A promising method based on surface plasmon resonance for quantitative analysis of biological samples

Surface plasmon resonance (SPR) technique is based on an optical measurement approach that is highly sensitive to the refractive index unit (RIU) of the sample on its analysis surface. Here, we demonstrate the direct detection of proteins and small molecules using an advanced SPR technology with a sensitivity that is as good as Fourier transform infrared (FTIR) spectroscopy. Some quantitative results are reported in this paper.