We have constructed an oblique-incidence reflectivity difference (OI-RD) microscope for fluorescent label-free imaging of DNA and protein microarrays on standard glass substrates. Using both OI-RD and fluorescence images, we demonstrate a difference in wetting behavior of labeled and unlabeled IgG protein molecules deposited on an aldehyde-derivatized glass surface. The potential of fluorescent labeling agents to influence the properties of proteins highlights the need for label-free microarray detection techniques to supplement existing fluorescence methods. We also present OI-RD images of an oligonucleotide microarray after printing and washing procedures to demonstrate the use of OI-RD for non-destructive monitoring of changes in the optical properties of microarrays during processing.

A single, square, voltage pulse is used to accelerate both the immobilization kinetics of DNA molecules on a functionalized thin film silicon dioxide surface and the hybridization of complementary DNA strands to immobilized DNA molecules. The voltage pulse is applied to an integrated thin-film metal electrode beneath the functionalized surface. The duration and magnitude of the voltage pulse are compatible with silicon microelectronics circuits. During immobilization, covalent thiol bonding to the functionalized surface occurs during a single pulse lasting only 100 ns. Hybridization to the immobilized complementary strand occurs during 100 μs pulses.

Developments in the field of BioMEMS share many of the same issues encountered in the development of neural interface technology that has been underway for many decades. In addition to issues of function, other issues such as biocompatibility and bioresistance have also presented great challenges. The focus of this paper is on the development and testing of electrically insulating biomaterials for micro-devices that can be implanted in biological systems. A variety of accelerated degradation and accelerated detection of degradation techniques have been developed and are used to screen candidate materials. Direct tests of mechanical properties, adhesion, and chemical resistance are used for further assessment. Promising materials indicate what chemistry might be suitable for development of a Chemical Vapor Deposited (CVD) thin film coating. CVD coatings are under development that may be useful for insulation of very small, micromachined elements of an implantable device while only increasing the size of the device by a few micrometers. Materials passing in-vitro testing are then considered for in-vivo testing. Novel instrumentation for testing devices in-vivo has been developed.

Luminescent CdSe-ZnS core-shell quantum dot (QD) bioconjugates were used as energy donors in fluorescent resonance energy transfer (FRET) binding assays. The QDs were coated with saturating amounts of genetically engineered maltose binding protein (MBP) using a noncovalent immobilization process, and Cy3 organic dyes covalently attached at a specific sequence to MBP were used as energy acceptor molecules. Energy transfer efficiency was measured as a function of the MBP-Cy3/QD molar ratio for two different donor fluorescence emissions (different QD core sizes). Apparent donor-acceptor distances were determined from these FRET studies, and the measured distances are consistent with QD-protein conjugate dimensions previously determined from structural studies.

Proteins, one of the building blocks in organisms, not only control the assembly in biological systems but also provide most of their complex functions. It may be possible to assemble materials for practical technological applications utilizing the unique advantages provided by proteins. Here we discuss molecular biomimetic pathways in the quest for imitating biology at the molecular scale via protein engineering. We use combinatorial biology protocols to select short polypeptides that have affinity to inorganic materials and use them in assembling novel hybrid materials. We give an overview of some of the recent developments of molecular engineering towards this goal. Inorganic surface specific proteins were identified by using cell surface and phage display technologies. Examples of metal and metal oxide specific polypeptides were represented with an emphasis on certain level of specificities. The recognition and self assembling characteristics of these inorganic-binding proteins would be employed in develeopment of hybrid multifunctional materials for novel bio- and nano-technological applications.

Nearly all retinal prosthetics have focused on electrical stimulation of the nervous system. We are developing a novel prosthetic interface for the retina based on neurotransmitter delivery. In the past, we have demonstrated the ability to stimulate individual rat pheochromacytoma cells (PC12 cell line) using microfluidic delivery through micron-sized apertures. This delivery was highly reproducible, very controllable, and quantifiable. But this early stage device was limited to a single stimulation site and crude microfluidics. Here, we present the next stage in microfluidic retinal prosthetics with a multi-stimulation site device that incorporates more advanced control over the microfluidic delivery. We created an array of apertures in a thin silicon nitride membrane, to which we can deliver neurotransmitters in an addressable manner. Excitable cells (PC12) are seeded on the device and imaged using Ca2+-sensitive dyes with a confocal microscope. We can then excite the cells at an array of multiple precise locations near the apertures, demonstrating the next step in neurotransmitter-based retinal prosthetics.

We report the controlled synthesis of multi-walled Carbon Nanotube-Quantum Dot (CNT-QD) heterojunctions using the Ethylene Carbodiimide Coupling procedure (EDC). Thiol stabilized ZnS capped CdSe quantum dots containing amine terminal groups (QDNH2) were conjugated with acid treated Multi-Walled Carbon Nanotubes (MWCNT) ranging from 400 nm to 4νm in length. SEM, TEM and FTIR were used to characterize the conjugation process.

A CMOS integrated microelectrode array (IMA) utilizing a low-inpedance transimpedance input has been developed. The design uses a three-stage amplifier, including a transimpedance input stage, buffer, and multiplexor. The input stage presents a low impedance which provides bias for the neural input and maximizes the current transfer into the circuit. The amplifiers are replicated in an 8x8 array, enabling measurement of a network of 64 neurons invitro. The chip was post-processed to provide a bio-compatible gold interface between the electrodes and the neurons. Simulations and experimental results demonstrate the functionality of the new design. Additional measurements are underway to provide experimental confirmation of the system with in-vitro neurons.

Luminescent quantum dots (QDs) are emerging as a new class of biological labels with unique properties and applications that are not available from traditional organic dyes and fluorescent proteins. Here we report new developments in using semiconductor quantum dots for quantitative imaging and spectroscopy of single cancer cells. We show that both live and fixed cells can be labeled with multicolor QDs, and that single cells can be analyzed by fluorescence imaging and wavelength-resolved spectroscopy. These results raise new possibilities in cancer imaging, molecular profiling, and disease staging.

Mechanical stimulation of single cells has been shown to affect cellular behavior from the molecular scale to ultimate cell fate including apoptosis and proliferation. In this, the ability to control the spatiotemporal application of force on cells through their extracellular matrix connections is critical to understand the cellular response of mechanotransduction. Here, we develop and utilize a novel pressure-driven equibiaxial cell stretching device (PECS) combined with an elastomeric material to control specifically the mechanical stimulation on single cells. Cells were cultured on silicone membranes coated with molecular matrices and then a uniform pressure was introduced to the opposite surface of the membrane to stretch single cells equibiaxially. This allowed us to apply mechanical deformation to investigate the complex nature of cell shape and structure. These results will enhance our knowledge of cellular and molecular function as well as provide insights into fields including biomechanics, tissue engineering, and drug discovery.

This paper presents a novel MEMS Ultrasound Electro-Magnetic transducer. With advances in CMOS MEMS fabrication processes [2] we can explore and build miniature devices which could only be designed till a few years back. As our understanding in MEMS evolved, we explored the use of Electro-Magnetism as an effective way to produce ultrasound waves. Thus we can use a highly efficient and inexpensive fabrication technique to fabricate transducers with a fairly good capability to produce and detect ultrasound waves.

The transducer consists of 2 concentric spiral coils, one carrying an AC current (which is tethered to the substrate at one end and free to vibrate at the other, also called the “Flapper”) and other coil carrying DC current (enveloping the inner coil, fixed and called “Stator”). The force arising from the interaction of the coupled magnetic fields induces a mechanical vibration of the flapper structure. The transducer serves as an actuator or a sensor (where we simply apply a pressure force on the flapper and note the frequency response of the flapper).

The current mode helps to associate the transducer with front-end electronics, which is one of the most critical components of ultrasound imaging systems

Advantages of this approach as compared to traditional PZT ceramics and capacitative micromachined devices are explored.

Different dimensions of the transducer to accommodate the limitations in the processes are explored and a comparison of the parameters is presented.

Potential uses and future challenges are discussed.

Extracellular potential is an important parameter which indicates the electrical activity of live cells. Membrane excitability in osteoblasts plays a key role in modulating the electrical activity in the presence of chemical agents. The complexity of cell signal makes interpretation of the cellular response to a chemical agent very difficult. By analyzing shifts in the signal power spectrum, it is possible to determine a frequency spectrum also known as Signature Pattern Vectors (SPV) specific to a chemical. It is also essential to characterize single cell sensitivity and response time for specific chemical agents for developing detect-to-warn biosensors. We used a 4x4 multiple Pt microelectrode array to spatially position single osteoblast cells, by using a gradient AC field. Fast Fourier Transformation (FFT) and Wavelet Transformation (WT) analyses were used to extract information pertaining to the frequency of firing from the extracellular potential.

Polymerase Chain Reaction (PCR) is a complicated gene amplification process using Mg2+ as an assistant factor of Taq enzyme. Influence of single-walled carbon nanotube on that reaction was investigated with scanning electron microscope (SEM), transmission electron microscope TEM) and quantitative PCR product analysis. Results showed that adding single-walled carbon nanotubes in the reaction liquid with a concentration of less than 3 νg/νl increase the amounts of PCR products. But more carbon nanotubes cause a great reduction of the PCR products. Similar effects were observed in the reaction without Mg2+. Possible reason could be the aggregation of reaction components caused by small amount of additive carbon nanotubes, which increases reaction probability. Our observations suggest that small amount of carbon nanotube could be used as an assistant factor to improve the PCR reaction.

The large optical detection systems that are typically utilized at present may not be able to reach their full potential as portable analysis tools. Accurate, early, and fast diagnosis for many diseases requires the direct detection of biomolecules such as DNA, proteins, and cells. In this research, a glass microchip with integrated microelectrodes has been fabricated, and the performance of electrochemical impedance detection was investigated for the biomolecules. We have used label-free λ-DNA as a sample biomolecule. By changing the distance between microelectrodes, the significant difference between DW and the TE buffer solution is obtained from the impedance-frequency measurements. In addition, the comparison for the impedance magnitude of DW, the TE buffer, and λ-DNA at the same distance was analyzed.

Studies of selective adhesion of biological molecules provide a path for understanding fundamental cellular properties. A useful technique is to use patterned substrates, where the pattern of interest has the same length scale as the molecular bonding sites of a cell, in the tens of nanometer range. We employ electrochemical methods to grow anodic alumina, which has a naturally ordered pore structure (interpore spacing of 40 to 400 nm) controlled by the anodization potential. We have also developed methods to selectively fill the alumina pores with materials with contrasting properties. Gold, for example, is electrochemically plated into the pores, and the excess material is removed by backsputter etching. The result is a patterned surface with closely separated islands of Au, surrounded by hydrophilic alumina. The pore spacing, which is determined by fabrication parameters, is hypothesized to have a direct effect on the spatial density of adhesion sites. By attaching adhesive molecules to the Au islands, we are able to observe and study cell rolling and adhesion phenomena. Through the measurements it is possible to estimate the length scale of receptor clusters on the cell surface. This information is useful in understanding mechanisms of leukocytes adhesion to endothelial cells as well as the effect of adhesion molecules adaptation on transmission of extracellular forces. The method also has applications in tissue engineering, drug and gene delivery, cell signaling and biocompatibility design.

We demonstrate a microfluidic actuation technique capable of directing nanoliter liquid samples on the surface of a glass substrate through the use of both electronically addressable heater arrays and chemical patterning. Pathways for liquid movement are delineated by the arrangement of microheaters, which also provide the thermocapillary actuating force. The drops are confined to these pathways by a selectively deposited fluorinated monolayer, which defines the channel edges. Operating voltages in the range of 2-3 V is used to move, split, and trap liquids. This fluid transportation technique enables direct access to liquid samples for handling and diagnostic purposes and offers a low power alternative to existing microfluidic systems.

A method is described for the fabrication of arrays of conducting, high aspect-ratio microwires for use as electrodes. The electrode arrays are fabricated by electrochemical deposition of metals, including Ni, Pt, Ag, Au and Rh, in channel glass templates having parallel, uniform, hollow channels with diameters that range from sub-micrometer to over 100 micrometers. The metals completely fill the hollow channels, yielding highly uniform electrodes with aspect ratios on the order of 1000 or more. The glass template electrically insulates the electrodes from one another. The electrode array wafers are cut and polished to a thickness ranging from about 100 to 2000 micrometers. The overall surface area is as large as 1 square centimeter. Alternatively, the wafers can be partially etched with acid to remove some of the glass matrix surrounding the electrodes, exposing an array of bare, solid wire stubs. The high aspect ratio microelectrode arrays were initially fabricated in order to provide the electrical interface for an intraocular retinal prosthesis, but have additional applications including biological and chemical sensing. Arrays with different channel sizes, different electrode spacing (with pitch from approximately 3R to 20R, where R is the electrode radius), and different geometrical arrangement are presented.

The main approach of in-vitro bone engineering is based on the use of stem cells cultured in microporous scaffolds. In order to quickly and non-destructively assess the different steps of bone formation, we have proposed the use of a permittivity-responsive sensor to monitor the microporous scaffold, which in this instance acts as a biointerface. The aim of this study is to monitor and characterize the growth and differentiation of cells in the microporous biointerface through CP measurements. Measurements are performed throughout the entire process of the cells' culture, growth and differentiation using a dielectric probe and a vector network analyser under sterile conditions. This concept of a permittivity-responsive biointerface will lead to sensitive biosensors especially adapted for use in tissue engineering.

Optimization of piezoresistive microcantilevers for biosensing applications has been studied using finite element analysis. Models have been described for predicting the static behavior of cantilevers with elastic and piezoresistive layers for analyte-receptor binding. The high-sensitivity cantilevers can be used to detect changes in surface stress due to the binding and hybridization of biomolecules. Chemo-mechanical binding forces have been analyzed to understand the issues of saturation over the cantilever surface. The introduction of stress concentration regions during cantilever fabrication has also been discussed which enhances the detection sensitivity through increased surface stress.

Molecular dynamics simulations were performed to study dynamics of carbon nanotube (CNT) interacting with biological molecules (DNA oligonucleotide and protein polypeptide) in an aqueous environment. Our results showed that an oligonucleotide or a polypeptide could be spontaneously inserted into a CNT, provided that the tube size is large enough and the oligonucleotide/polypeptide is appropriately aligned with CNT. The van der Waals and hydrophobic forces were found to be important for the insertion process, with the former playing a more dominant role in the CNT-oligonucleotide and CNT-polypeptide interaction. We discussed temperature effect on the filling process and found that higher temperature can accelerate encapsulation of biological molecules. Our study has general implications on filling nanoporous materials with water solutes of molecular cluster or nanoparticles. The encapsulated CNT-oligonucleotide/polypeptide or other CNT based bio-nano-complex can be further exploited for applications such as molecular electronics, sensors, electronic DNA sequencing, and nanotechnology of gene/drug delivery systems.