The full exploitation of bacterial whole-cell biosensing systems in field applications requires the survival of bacterial cells and long term-preservation of their sensing ability during transportation and on-site storage of such analytical systems. Specifically, there is a need for rapid, simple and inexpensive biosensing systems for monitoring human health and the environment in remote areas which often suffer from harsh atmospheric conditions and inadequate commercial distribution and storage facilities. Our laboratory has previously reported the successful use of bacterial spores as vehicles for the long-term preservation and storage of whole-cell biosensing systems at room temperature. In the present research, we have accomplished a year-long study to investigate the effect of extreme climatic conditions on the stability of spores-based whole-cell biosensing systems. The spores were stored in laboratory conditions that simulated those found in real harsh environments and germination ability and analytical performance of the spore-based sensing systems upon storage in such conditions was monitored. Our results proved that the intrinsic resistance of spores to harsh environmental conditions helped maintain the integrity of the sensor bacteria. The revived active cells actually retained their analytical performance during the course of the twelve-month storage study.

The goal of the proposed study is to understand the morphology, physical, and responsive properties of synthetic polymer and biopolymer layer-by-layer (LbL) arrays using the inkjet printing and stamping technique, in order to develop patterned encapsulated thin films for controlled release and biosensor applications. In this study, we propose facile fabrication processes of hydrogen-bonded and electrostatic LbL microscopic dot arrays with encapsulated target organic and cell compounds. We study encapsulation with the controllable release and diffusion properties ofpoly(vinylpyrrolidone) (PVPON), poly(methacrylic acid) (PMAA), silk-polylysine, silk-polyglutamic acid, pure silk films, and E-coli cells from the multi-printing process. Specifically, we investigate the effect of thickness, the number of bilayers, and the hydrophobicity of substrates on the properties of inkjet/stamping multilayer films such as structural stability, responsiveness, encapsulation efficiency, and biosensing properties. We suggest that a more thorough understanding of the LbL assembly using inkjet printing and stamping techniques can lead to the development of encapsulation technology with no limitations on either the concentration of loading, or the chemical and physical properties of the encapsulated materials. In addition, this study offers new encapsulation concepts with simple, cost effective, highly scalable, living cell-friendly, and controllable patterning properties.

The generation of new nanoscale fabrication techniques is both novel and necessary for the generation of new devices and new materials. Graphene, a heavily studied and versatile material, provides new avenues to generate these techniques. Graphene’s 2-dimensional form remains both robust and uncommonly manipulable. In this project we show that graphene can be combined with the yeast cell, Saccharomyces cerevisiae, arguably the most studied and utilized organism on the planet, to generate these new techniques and devices. Graphene oxide will be used to encapsulate yeast cells and we report on the development of a method to electrically read the behaviour of these yeast cells. The advantage of an encapsulation process for a cell sensor is the ability to create a system that can electrically show both changes in ion flow into and out of the cell and mechanical changes in the cell surface. Since the graphene sheets are mechanically linked to the surface of the cell, stresses imparted to the sheets by changes in the cell wall or cell size would also be detectable. The development process for the encapsulation will be refined to eradicate excess gold on the yeast cells as well as to minimize the amount of stray, unattached graphene in the samples. The graphene oxide encapsulation process will also be shown to generate a robust substrate for material synthesis. With regards to cell sensing applications, sources of noise will be examined and refinements to the device setup and testing apparatus explored in order to magnify the relevant electrical signal. The spherical topography of an encapsulated yeast cell will be shown to be an advantageous substrate for material growth. Zinc oxide, as a sample material being investigated for its own applications for photovoltaics, will be grown on these substrates. The spherical nature of the encapsulated cell allows for radial material growth and a larger photo-active area resulting in a device with increased efficiency over a planar complement. The zinc oxide nanorods are grown via an electrochemical growth process which also reduces the graphene oxide sheets to electrochemically reduced graphene. XRD analysis confirms that the material synthesized is infact zinc oxide. The nanorods synthesized are 200nm to 400nm in width and 1µm in length. The increase efficiency of the non-planar device and the effectiveness of the encapsulated cell as a growth substrate indicate encapsulated cells as a research avenue with significant potential.

Urine culture, the current gold standard for urinary tract infection (UTI) diagnosis, does not produce results in an acceptable length of time. An ultra-sensitive, cost-effective electrochemical biosensing platform with nanostructured microelectrodes was designed to address the need for a rapid, point-of-care (PoC) test that could achieve a sample-to-answer time in less than an hour. Printed circuit boards and metallized glass slides were processed using various techniques and then tested for their ability to form nanostructured microelectrodes. Peptide nucleic acid probes for the bacteria and yeast as well as ten probes for antibiotic resistance genes were designed and synthesized for use with the new platform. Validation of the sensor's specificity was performed using high concentrations (100nM) of synthetic DNA oligomers. Furthermore, a clinically relevant sensitivity of 103 cfu/mL was demonstrated by detecting 4 pathogen lysates (Staphylococcus saprophyticus, Pseudomonas aeruginosa, Enterococcus faecalis and Klebsiella pneumoniae) in a buffered solution.

This work describes the functionalization and testing of Si$_3$N$_4$-based photonic crystal slabs (PCS) for label-free biosensing. PCS support optical resonance modes that are sensitive to the local refractive index. Knowing that surface binding events change the local RI, analyte binding to the activated sensor can be detected. Various functionalization recipes were tried, and one was preferred for the biosensing experiments due to its higher yield and uniformity. Additionally, thickness of the topmost sensor layer was studied to assess biosensor performance quantified through sensitivity metrics. On the systems level, a reusable clamping system and customized microfluidic channels were designed, fabricated, and implemented on the PCS biosensors to enable device refurbishment. Proof-of-principle biodetection experiments were carried out using the established functionalization protocol on the in-house fabricated PCS. Conjugation of streptavidin and bovine serum albumin to the sensor surface was observed through wavelength shifts of the resonant modes.

Urine culture, the current gold standard for urinary tract infection (UTI) diagnosis, does not produce results in an acceptable length of time. An ultra-sensitive, cost-effective electrochemical biosensing platform with nanostructured microelectrodes was designed to address the need for a rapid, point-of-care (PoC) test that could achieve a sample-to-answer time in less than an hour. Printed circuit boards and metallized glass slides were processed using various techniques and then tested for their ability to form nanostructured microelectrodes. Peptide nucleic acid probes for the bacteria and yeast as well as ten probes for antibiotic resistance genes were designed and synthesized for use with the new platform. Validation of the sensor's specificity was performed using high concentrations (100nM) of synthetic DNA oligomers. Furthermore, a clinically relevant sensitivity of 103 cfu/mL was demonstrated by detecting 4 pathogen lysates (Staphylococcus saprophyticus, Pseudomonas aeruginosa, Enterococcus faecalis and Klebsiella pneumoniae) in a buffered solution.

This work describes the functionalization and testing of Si$_3$N$_4$-based photonic crystal slabs (PCS) for label-free biosensing. PCS support optical resonance modes that are sensitive to the local refractive index. Knowing that surface binding events change the local RI, analyte binding to the activated sensor can be detected. Various functionalization recipes were tried, and one was preferred for the biosensing experiments due to its higher yield and uniformity. Additionally, thickness of the topmost sensor layer was studied to assess biosensor performance quantified through sensitivity metrics. On the systems level, a reusable clamping system and customized microfluidic channels were designed, fabricated, and implemented on the PCS biosensors to enable device refurbishment. Proof-of-principle biodetection experiments were carried out using the established functionalization protocol on the in-house fabricated PCS. Conjugation of streptavidin and bovine serum albumin to the sensor surface was observed through wavelength shifts of the resonant modes.

This research investigates an extension of the glancing angle deposition (GLAD) technique and a biosensing application of films produced by GLAD. The extension to GLAD, called phi-sweep (PS), improves column isolation compared to films grown by traditional GLAD (TG) as well as modifies the column tilt angle, , of the slanted columns according to tan(_{PS}) = tan(_{TG}) cos(), where is the sweep angle. The biosensing application makes use of localized surface plasmon resonance in noble metal GLAD films functionalized with rabbit immunoglobulin G (rIgG) to detect binding of anti-rabbit immunoglobulin G (anti-rIgG) to the films' surface. The extinction peak red-shifts a distance dependent on the concentration of anti-rIgG solution in a manner described by the Langmuir isotherm with a saturation value, _{max}, of 29.4 0.7 nm and a surface confined thermodynamic binding constant, K, of (2.7 0.3)10 M. / Microsystems and Nanodevices

Diss. (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 6 uppsatser.

Diss. (sammanfattning) Stockholm : Tekn. högsk. / Härtill 4 uppsatser.