Application of an Optical Biosensor to Study the Interaction between Porphyrins and Wheat Germ Agglutinin

An optical biosensor with a stirred cuvette has been used to monitor the interaction of immobilized wheat germ agglutinin （WGA） with two water-soluble cationic porphyrins, The association constants （Ka） of the free base porphyrin and its Zn（Ⅱ） complex form were 2. 66 and 27.31 × 10^5 l,/mol at 20 ℃ respectively. The interactions of the free base porphyrin were further investigated at temperatures between 15 ℃ and 37 ℃, The thermodynamics parameters, changes in free energy, enthalpy and entropy, were -31.23, 22.92, 54.15 ld/mol respectively. The heat capacity change was -355.53 J · mol^-1·K^-1 The binding was driven by entropic contribution, and showed strong enthalpy-entropy compensation. It was governed primarily by hydrophobic forces.

A Chemiluminescence Optical Fiber Glucose Biosensor Based on Co-immobilizing Glucose Oxidase and Horseradish Peroxidase in a Sol-gel Film

An optical fiber bienzyme sensor based on the luminol chemiluminescent reaction was developed and demonstrated to be sensitive to glucose. Glucose oxidase(GOD) and horseradish peroxidase(HRP) were co-immobilized by microencapsulation in a sol-gel film derived from tetraethyl orthosilicate(TEOS). The calibration plots for glucose were established by the optical fiber glucose sensor fabricated by attaching the bienzyme silica gel onto the glass window of the fiber bundle. The linear range was 0 2-2 mmol/L and the detection limit was approximately 0 12 mmol/L. The relative standard deviation was 5.3% ( n =6). The proposed biosensor was applied to glucose assay in ofloxacin injection successfully.

Thermodynamic Analysis of the Interaction between Cationic Porphyrins and Human Serum Albumin by an Optical Biosensor

An optical biosensor with a stirred cuvette has been used to monitor the interaction between immobilized human serum albumin （HSA） and three water-soluble cationic porphyrins. The binding constants at 25℃ obtained from biosensor analysis were compared with those from fluorescence spectroscopy. The interactions were further investigated at temperatures from 15℃ to 30℃. The thermodynamics parameters, changes of free energy （△G）, enthalpy （△H） and entropy （△S）, were evaluated from equilibrium data. It appeared that the binding process was governed primarily by electrostatic forces.

Polymer Integrated Waveguide Optical Biosensor by Using Spectral Splitting Effect

The polymer waveguide optical biosensor based on the Mach-Zehnder interferometer （MZI） by using spectral splitting effect is investigated. The MZI based biosensor has two unequal width sensing arms. With the different mode dispersion responses of the two-arm waveguides to the cladding refractive index change, the spectral splitting effect of the output interference spectrum is obtained, inducing a very high sensitivity. The influence of the different mode dispersions between the two-arm waveguides on the spectral splitting characteristic is analyzed. By choosing different lengths of the two unequal width sensing arms, the initial dip wavelength of the interference spectrum and the spectral splitting range can be controlled flexibly. The polymer waveguide optical biosensor is designed, and its sensing property is analyzed. The results show that the sensitivity of the polymer waveguide optical biosensor by using spectral splitting effect is as high as 10^4nm/RIU, with an improvement of 2-3 orders of magnitude compared with the slot waveguide based microring biosensor.

High-performance Refractive Index Sensor Based on Photonic Crystal Single Mode Resonant Micro-cavity

An effective refractive index sensor built with square lattice photonic crystal is proposed,which can be applicable to photonic integrated circuits.Two photonic crystal waveguides rather than conventional ridge waveguides are used as entrance/exit waveguides to the micro-cavity.Three layers of photonic lattice are set between the photonic crystal waveguides and the micro-cavity to achieve both a high transmission and a high sensitivity.The plane wave method is utilized to calculate the disperse curves and the finite difference time domain scheme is employed to simulate the light propagation.At the resonant wavelength of about 1500 nm,the resonant wavelength shifts up by 0.7 nm for each increment of Δn=0.001.A transmission of more than 0.75 is observed.Although the position disorder of the photonic crystal doesn't affect the sensitivity of the sensor, the transmission reduces rapidly as the disorder increases.

Real-Time Monitoring of Dynamic Chemical Processes in Microbial Metabolism with Optical Sensors

Monitoring microbial metabolism is vital for revealing the mechanism of disease related to microbial metabolism and providing guidance for biomanufacturing processes optimization.However,it remains a grand challenge to offer real-time insights into microbial metabolism owing to the complex and dynamic process.In this paper,the recent advances and prospects of optical biosensors including the organic,genetic coding and inorganic optical biosensors are briefly described for real-time monitoring of dynamic microbial metabolism.This paper points out that challenges remain in microbial heterogeneity.We believe that this work will inspire the application of developing new methods for single cell real-time analysis.

Feasible and reliable quantification of mRNA in Arabidopsis thaliana using optical thin-film biosensor chips

mRNA quantification is very important in molecular biological researches. Traditional spectrophotometric method cannot distinguish DNA, rRNA and tRNA species from mRNA. Northern blot can be used for mRNA quantification but is known to be time consuming. To rapidly detect mRNA levels, we developed an optical thin-film biosensor chip based method, to quantify mRNA in samples. After total RNA was extracted, the mRNA with poly（A） tails was reverse transcribed with oligo（dT）20 primers and dNTPs mixed with digoxigenin（DIG）-11-dUTE The transcribed first strand cDNA was hybridized with oligo（dA）20 nucleotide probes spotted on optical thin-film biosensor chips. Excess first strand cDNA, single-strand RNA, and mis-matched DNA/DNA hybrids were removed by washing. The perfect-matched DNA/DNA hybrid was detected with anti-DIG-AP （alkaline phosphatase） conjugate and then incubated with NBT/BCIP substrate for color development. The range of the color is from purplish red to blue, according to the cDNA mass deposited on chip sur- face. Detection of mRNA levels from Arabidopsis samples proved that this method is feasible for mRNA quantification, and has great potential for application in mRNA quantification in various organisms.

Probing the dynamic structural changes of DNA using ultrafast laser pulse in graphene-based optofluidic device

The ultrafast monitoring of deoxyribonucleic acid(DNA)dynamic structural changes is an emerging and rapidly growing research topic in biotechnology.The existing optical spectroscopy used to identify different dynamical DNA structures lacks quick response while requiring large consumption of samples and bulky instrumental facilities.It is highly demanded to develop an ultrafast technique that monitors DNA structural changes with the external stimulus or cancer-related disease scenarios.Here,we demonstrate a novel photonic integrated graphene-optofluidic device to monitor DNA structural changes with the ultrafast response time.Our approach is featured with an effective and straightforward design of decoding the electronic structure change of graphene induced by its interactions with DNAs in different conformations using ultrafast nanosecond pulse laser and achieving refractive index sensitivity of~3×10^(−5) RIU.This innovative technique for the first time allows us to perform ultrafast monitoring of the conformational changes of special DNA molecules structures,including G-quadruplex formation by K+ions and i-motif formation by the low pH stimulus.The graphene-optofluidic device as presented here provides a new class of label-free,ultrafast,ultrasensitive,compact,and cost-effective optical biosensors for medical and healthcare applications.