A microfluidic bacteria culturing device with MALDI mass spectrometry detection

A novel microfluidic device was developed for bacterial cell culturing using mass spectrometry as the detector. One of the challenges in proteomics is to achieve high sensitivity in the identification of proteins in complex samples with widely varying concentrations. The main limitations for proteomic studies are relatively slow and labor-intensive steps such as cell culturing and protein digestion of small sample quantities. Microfluidics is a promising approach to increase throughput and to reduce the time-consuming steps that are necessary for proteomics. When an analytical detection method is combined with microfluidics it can overcome limitations that are important in the analysis of biological samples. In this work a microfluidic device was constructed from poly(methyl methacrylate) PMMA using hot embossing from a brass metal mold prepared from micro-milling and combined with off-line matrix assisted laser desorption-mass spectrometry mass spectrometry (MALDI-MS) for analysis. In this work, E. coli K12 strain was selected as a model for performing the analysis. Microfluidic devices were used to process the sample and mass spectrometry was used as detection method. The microfluidic device used in this study consists of three modules, capture, culture, and digestion chamber, integrated onto a single platform. The cells are captured on the microfluidic chip using polyclonal goat antibody on a modified PMMA surface, and are released using 0.25% trypsin, and transferred to the culture cell, which is filled with the growth medium. The temperature of the culture cell is maintained at 37 ºC using a heater and a PDMS cover slip was used for air perfusion. Samples collected at different culturing durations (4 h, and 10 h) are transferred to a micro-post bioreactor, which contains immobilized trypsin. The effluent from the microfluidic device was spotted onto a MALDI target and analyzed using MALDI time-of-flight mass spectrometry

Micro-machining techniques for the fabrication of fibre Fabry-Perot sensors

Fabry-Perot optical fibre sensors have been used extensively for measuring a variety of parameters such as strain, temperature, pressure and vibration. Conventional extrinsic fibre Fabry-Perot sensors are associated with problems such as calibration of the gauge length of each individual sensor, their relatively large size compared to the diameter of optical fibre and a manual manufacturing method that leads to poor reproducibility. Therefore, new designs and fabrication techniques for producing fibre Fabry-Perot sensors are required to address the problems of extrinsic fibre Fabry-Perot sensors. This thesis investigates hydrofluoric acid etching and F2-laser micro-machining of optical fibres to produce intrinsic Fabry-Perot cavities. Chemical etching of single mode fused silica fibres produced cavities across the core of the fibres due to preferential etching of the doped-region. Scanning electron microscope, interferometric surface profiler and CCD spectrometer studies showed that the optical quality of the etched cavities was adequate to produce Fabry-Perot interference. Controlled fusion splicing of etched fibres produced intrinsic Fabry-Perot cavities. These sensors were surface-mounted on composite coupons and their response to applied strain was studied using low coherence interferometry. These sensors showed linear and repeatable response with the strain measured by the electrical resistance strain gauges. To carry out F2-laser micro-machining of fused silica and sapphire substrates, a micro-machining station was designed and constructed. This involved the design of illumination optics for 157 nm laser beam delivery, the design and construction of beam delivery chamber, target alignment and monitoring systems. Ablation of fused silica and sapphire disks was carried out to determine ablation parameters suitable for micro-machining high aspect ratio microstructures that have adequate optical quality to produce Fabry-Perot interference. Cavities were micro-machined through the diameter of SMF 28 and SM 800 fibres at different energy densities. CCD interrogation of these intrinsic fibre cavities ablated at an energy density of 25 x 10 4 Jm -2 produced Fabry-Perot interference fringes. The feasibility of micro-machining high aspect ratio cavities at the cleaved end-face of the fused silica fibres and through the diameter of sapphire fibres was demonstrated. A technique based on in-situ laser-induced fluorescence monitoring was developed to determine the alignment of optical fibres and ablation depth during ablation through the fibre diameter. Ablation of cavities through the diameter of fibre Bragg gratings showed that the heat-generated inside the cavity during ablation had no effect on the peak reflection and the integrity of core and cladding of the fibre. Finally, a pH-sensor, a chemical sensor based on multiple cavities ablated in multimode fibres and a feasible design for pressure sensor fabrication based on ablated cavity in a single mode fibre were demonstrated.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Simultaneous DSC-FTIR spectroscopy : comparison of cross-linking kinetics of an epoxy/amine resin system

AbstractThe top-cover of a conventional differential scanning calorimeter (DSC) was modified to accommodate two custom-made fibre-optic probes. The function of the probes was to illuminate the sample and reference compartments of the DSC and to return the reflected light from the DSC pans to a fibre-coupled Fourier transform near-infrared (FTIR) spectrometer. The cross-linking kinetics of a commercially available epoxy/amine resin system were studied using the conventional and modified DSC along with conventional transmission FTIR spectroscopy. The cross-linking kinetics and the activation energies for the epoxy/amine resin system obtained via the conventional DSC and simultaneous DSC/FTIR were similar (60.22–60.97 kJ mol−1). However, the activation energy obtained for the cuvette-based conventional transmission FTIR experiments was found to be lower (54.66 kJ mol−1). This may be attributed to the temperature-control attained within the cuvette holder. The feasibility of using a simple fibre-optic probe to link the DSC to the FTIR spectrometer was demonstrated

Process monitoring of fibre reinforced composites using a multi-measurand fibre-optic sensor

AbstractThis paper reports on the design, fabrication, characterisation and deployment of a multi-measurand optical fibre sensor (MMS) that is capable of simultaneously monitoring strain, temperature, refractive index and cross-linking chemistry. The sensor design is based on the extrinsic fibre Fabry–Perot interferometer. A feature of this sensor system is that a conventional multi-channel fibre-coupled near-infrared spectrometer is used to monitor the four independent parameters. The issues relating to the measurement resolution of the individual sensors and the associated interrogation equipment are discussed. The MMS was embedded in between the fourth and fifth plies of an eight-ply E-glass plain-weave fabric. A commercially available thermosetting epoxy/amine resin system was used to impregnate the fabric layers manually. The laminated preform was vacuum-bagged and cured in an autoclave. The following parameters were monitored: the depletion rates of the epoxy and amine functional groups in the resin system; the temperature in close proximity to the “chemical sensor”; the evolution of strain; and the refractive index of the resin system. The effect of post-processing on the output from the embedded optical fibre sensors is also considered

Interferometric Fiber Optic Sensors

Fiber optic interferometers to sense various physical parameters including temperature, strain, pressure, and refractive index have been widely investigated. They can be categorized into four types: Fabry-Perot, Mach-Zehnder, Michelson, and Sagnac. In this paper, each type of interferometric sensor is reviewed in terms of operating principles, fabrication methods, and application fields. Some specific examples of recently reported interferometeric sensor technologies are presented in detail to show their large potential in practical applications. Some of the simple to fabricate but exceedingly effective Fabry-Perot interferometers, implemented in both extrinsic and intrinsic structures, are discussed. Also, a wide variety of Mach-Zehnder and Michelson interferometric sensors based on photonic crystal fibers are introduced along with their remarkable sensing performances. Finally, the simultaneous multi-parameter sensing capability of a pair of long period fiber grating (LPG) is presented in two types of structures; one is the Mach-Zehnder interferometer formed in a double cladding fiber and the other is the highly sensitive Sagnac interferometer cascaded with an LPG pair

A Semi-Physiologically Based Pharmacokinetic Model Describing the Altered Metabolism of Midazolam Due to Inflammation in Mice

This is the author's accepted manuscript.Purpose To investigate influence of inflammation on metabolism and pharmacokinetics (PK) of midazolam (MDZ) and construct a semi-physiologically based pharmacokinetic (PBPK) model to predict PK in mice with inflammatory disease. Methods Glucose-6-phosphate isomerase (GPI)-mediated inflammation was used as a preclinical model of arthritis in DBA/1 mice. CYP3A substrate MDZ was selected to study changes in metabolism and PK during the inflammation. The semi-PBPK model was constructed using mouse physiological parameters, liver microsome metabolism, and healthy animal PK data. In addition, serum cytokine, and liver-CYP (cytochrome P450 enzymes) mRNA levels were examined. Results The in vitro metabolite formation rate was suppressed in liver microsomes prepared from the GPI-treated mice as compared to the healthy mice. Further, clearance of MDZ was reduced during inflammation as compared to the healthy group. Finally, the semi-PBPK model was used to predict PK of MDZ after GPI-mediated inflammation. IL-6 and TNF-α levels were elevated and liver-cyp3a11 mRNA was reduced after GPI treatment. Conclusion The semi-PBPK model successfully predicted PK parameters of MDZ in the disease state. The model may be applied to predict PK of other drugs under disease conditions using healthy animal PK and liver microsomal data as inputs