Reid N. Orth

A scanning tip electrospinning source for deposition of oriented nanofibres

We present a method for controlled deposition of oriented polymeric nanofibres. The method uses a microfabricated scanned tip as an electrospinning source. The tip is dipped in a polymer solution to gather a droplet as a source material. A voltage applied to the tip causes the formation of a Taylor cone, and at sufficiently high voltages, a polymer jet is extracted from the droplet. By moving the source relative to a surface, acting as a counter-electrode, oriented nanofibres can be deposited and integrated with microfabricated surface structures. For example, we deposited fibres of polyethylene oxide with diameters ranging from 100 to 1800 nm, with the diameter primarily depending on the concentration of the polymeric solution. In addition to the uniform fibre deposition, the scanning tip electrospinning source can produce self-assembled composite fibres of micro-and nanoparticles aligned in a polymeric fibre. We also deposited oriented conductive polymeric fibres of polyaniline and investigated the conductivity of these fibres as components for polymeric nanoelectronics.

Avidin-Biotin Micropatterning Methods for Biosensor Applications

High-resolution patterning methods have been developed to immobilize functional proteins onto a silicon dioxide surface for biosensor applications. Antibody lines, as small as 5 μm in width, with intervening 5 μm spacings, were patterned on oxidized silicon wafers using avidin-biotin chemistry. The N-hydroxysuccinimide (NHS) ester of photoactivatable biotin was covalently bound to a self assembled monolayer (SAM) of 3-amino-propyltriethoxysilane (3-APTS) after irradiation by 350 nm ultraviolet (UV) light from a 25 W Hg arc lamp. The patterned layers were evaluated using fluorescent imaging of Alexa-488 conjugated avidin and two fluorescence-conjugated antibodies. This technique allows binding of any biotinylated compound without exposure to harmful UV light, extreme pH, toxic chemicals, or high salinity.

End-functionalization of poly(3-hydroxybutyrate)via genetic engineering for solid surface modification

A new approach to end-functionalization of poly(3-hydroxybutyrate)[PHB] is described. Using genetically engineered PHB synthase fused with a 10x-histidine units at its N-terminus, end-functionalized PHB was synthesized and used for the solid surface modification.

Polymeric trapezoidal microelectrospray emitter integrated with a microfluidic chip

We have demonstrated an electrospray of fluid from a tip made from a shaped thin polymer tip bonded to a microfluidic channel. A trapezoidal electrospray emitter was fabricated using lithography and plasma etching. This was integrated with a channel and used for electrospray ionization of small molecules. A lithographically produced silicon master was used to emboss a microfluidic channel in a cyclo olefin substrate. The electrospray emitter was sandwiched between the two plastic pieces at the exit of the microfluidic channel and thermally bonded. The microfluidic channel dimensions were 40 /spl mu/m wide, 20 /spl mu/m deep and 2.5 cm long. One end of channel was directly connected to the electrospray emitter and another end of channel was connected to the silica capillary tubing which was connected to an external syringe pump. 70/30 methanol/DI water with 1% acetic acid was used for testing the spraying characteristics. A grounded aluminum plate was placed 0.6 cm from the electrospray emitter and 2500 volts applied at the reservoir. A Taylor cone was formed on the trapezoid electrospray emitter film. A stable liquid flow of 300 nl/minute was created by the syringe pump for supplying liquid to the electrospray emitter and to maintain a constant spray. 40 nA of total ion current was measured by a picoammeter for 40 minutes.

Micro- and Nanofabricating Lipid Patterns Using a Polymer-Based Wet Lift-Off

Accurate placement of biomaterials at nanoscale resolution opens new capabilities for biological sensing, cell manipulation, and control of cellular transduction cascades. We demonstrate that lipid molecules can be patterned on silicon using a polymer lift-off technique. Patterned lipid bilayers serve as biomaterial patterning platforms useful for studies of cellular function. Submicron feature sizes were achieved using this templating technique which is suitable for delicate biomaterials 1 . Projection lithography and reactive ion etching were used to pattern a Parylene-coated surface. The patterned surface was subsequently exposed to 100 nm unilamellar lipid vesicles that bound to the native oxide surfaces of silicon and spread to form supported lipid bilayers. The nanoscale pattern is realized as the polymer is peeled away in deionized water. The versatility of this method is demonstrated by the successful preparation of functionalized lipid bilayer surfaces. Specific intermolecular interactions were demonstrated between supported membranes: DPPE-PE (2000) biotin/avidin, dinitrophenol (DNP)-conjugated lipids/anti-DNP IgE, and cationic lipid and M13 dsDNA:YOYO-1.

Micromachined Polymeric Tip as An Electrospray Ionization Source

We have fabricated and tested a new electrospray ionization source integrated with a microfluidic channel for interfacing to a Time-of-Flight mass spectrometry (TOF MS). A triangle shaped polymeric tip was patterned using an optical lithography and plasma etching from a polymeric thin film deposited on a silicon wafer. The shaped emitter was peeled from a silicon wafer. The emitter tip was aligned at the exit of the microfluidic channel and bonded between two plastic pieces; one of which had a microfluidic channel embossed. Liquid was supplied to the emitter tip via a reservoir hole connected to the embossed microfluidic channel by a syringe pump. A gold wire was inserted into the reservoir as a high voltage supply for an electrospray ionization. The polymeric electrospray source tip was placed 1.0 cm away from an entrance orifice of TOF MS. Berberine was used as a test sample to characterize the performance of the electrospray device. The total ion current was stable for many minutes with fluctuations ofless than 4.0%.

Nanoscale Patterning of Antigen on Silicon Substrate to Examine Mast Cell Activation

Abstract : Rat Basophilic Leukemia (RBL) cells are immobilized and stimulated on micro- and nanometer scale patterns of supported lipid bilayers. The patterns are realized as the photolithographically patterned polymer is mechanically peeled away in one contiguous piece in solution. The 0.36 micrometers (exp 2) to 4,489 micrometers(exp 2) patches can contain both fluorescent lipids and lipid-linked antigen and provide a synthetic biological substrate for analysis of cell surface receptor-mediated events. 100-nm unilamellar lipid vesicles spread to form a supported lipid bilayer on a thermally oxidized silicon surface as confirmed by fluorescence recovery after photobleaching (FRAP). Aggregation of fluorescently labeled receptors is observed as their coincidence with the patterned antigen. Cell morphology is analyzed with scanning electron microscopy (SEM). Thus, a novel method has been developed for patterning antigen. capturing and immobilizing cells via specific receptors, and spatially controlling antigenic stimulus on the nanoscale.

Nanometer-scale antibody patterning for directed eosinophil cell immobilization and stimulation

Antibodies (Ab) are patterned at nanoscale precision for the precise immobilization and stimulation of immune cells. We demonstrate that the antigen bovine serum albumin (BSA) can be patterned on silicon using a photolithographically patterned polymer lift-off technique. The nanoscale pattern is realized as the polymer is mechanically peeled away in one contiguous piece in aqueous solution. Anti-BSA Ab are bound specifically to BSA to create a pattern of oriented Ab that provides a surface for eosinophil immobilization and degranulation. The patterns ranged from 0.36 /spl mu/m/sup 2/ to 4,489 /spl mu/m/sup 2/, appropriate dimensions for the 10-14 /spl mu/m diameter eosinophil cells. This method provides a new technique for immobilizing cells onto nano and micrometer scale patterns for analyzing cellular biochemical cascade events such as degranulation and studying cellular morphological changes in response to defined nanoscale antigenic stimulus.