Microcontact printing (µCP) is a new method of molecularly patterning surfaces on a micrometer scale. In this paper, we present the extension of microcontact printing to producing patterned layers of proteins on solid substrates. µCP avoids the use of strong acids and bases necessary in photolithographic patterning, allowing its use for patterning of proteins and other biological layers. We also describe the methods of thin stamp microcontact printing that allow printing of isolated features previously unattainable by microcontact printing. A solution of polylysine in borate-buffered saline was printed onto a glass coverslip, yielding micrometer scale features over an area of 4 cm 2 .

We describe a method for producing high-resolution chemical patterns on surfaces to control the attachment and growth of cultured neurons. Microcontact printing has been extended to allow the printing of micron-scale protein lines aligned to an underlying pattern of planar microelectrodes. Poly-L-lysine (PL) lines have been printed on the electrode array for electrical studies on cultured neural networks. Rat hippocampal neurons showed a high degree of attachment selectivity to the PL and produced neurites that faithfully grew onto the electrode recording sites.

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Most of us heard the story of the blind men and the elephant as children. In this old tale from India each man in a group of blind men touches a different part of an elephant. Each walks away with a different experience and subsequently argues that the elephant is like a spear (the tusk), a thick rope (the trunk), a wall (the flank), etc. Only the combination of their stories would have provided a complete, or at least more complete, picture of what an elephant really is. In some sense this is the story of surface analysis, which lacks a single analytical tool that can provide comprehensive information about a surface or interface. We rely on X-ray photoelectron spectroscopy (XPS) for surface elemental analysis and oxidation state information, spectroscopic ellipsometry for film thicknesses and optical constants, contact angle measurements to understand surface wetting, Fourier transfer infrared spectroscopy (FTIR) to reveal functional group information, negative and positive ion time-of-flight secondary ion mass spectrometry (ToF-SIMS)to provide molecular fragments and trace element detection, Rutherford backscattering (RBS) for elemental composition and atom distributions in moderately thick films (typically at least a few nanometers), nuclear reaction analysis (NRA) for absolute quantitation of atomic compositions of thin films, atomic force microscopy (AFM) for surface roughness, scanning electron microscopy (SEM) to reveal surface features and patterning, BET (Brunauer, Emmett, Teller) isotherm measurements to provide surface areas and pore sizes, etc. Combining such information typically provides the most complete view of a surface or interface. The purpose of my talk is to discuss a problem that illustrates the importance of using multiple analytical methods to better understand surfaces and interfaces -an important conclusion of my talk is that no single instrument could have provided the insight into the problem that was gained from the combination of techniques. In particular, we are currently developing and/or modifying highly stable materials based on diamond, zirconia, and/or graphite, which can withstand extreme pH values, temperatures, and/or other harsh chemical conditions, as stationary phases or supports for liquid chromatography.1-3At present this is an important topic in separations science -about 410

Someday, nanocircuits may perform complex calculations at high speeds using low power. Indeed, the need and constraints regarding complex interconnections in such nanometer scale circuits suggests that self-assembly will be a comparatively easier approach than relying solely on a top down strategy. DNA templated segments (circuit elements) of a large circuit made with DNA origami 1 and high resolution patterning of the surface by complementary DNA templates may also assist in the self assembly of nanocircuits. Semiconducting elements (carbon nanotubes) might be introduced into circuit elements to act as transistors. The self-assembled nanocircuit can be selectively metalized to make the circuit conducting. Previously, thiols have been patterned onto a gold surface by dip-pen nanolithography. 2However, although the Au-S bond is initially fairly strong, once sulfur oxidizes this bond becomes weak. An alternative approach, which we propose, is to self assemble a dithiol monolayer onto a gold nano-dot surface followed by reaction with 1,4-polybutadiene (thiol-ene chemistry). 3 Although, the dithiol monolayer should still be prone to oxidation, there will now be many of these weak Au-S (oxidized) bonds that should be cross-linked by 1,4-polybutadiene (PBd). This surface should also have many surface carbon-carbon double bonds that could be used to attach the thiolated complementary DNA required for surface patterning and immobilization of DNA origami. Such an assembly should make the entire structure more stable, reducing the likelihood that DNA templated circuit elements will detach. The 1,4-polybutadiene molecular cover should also slow the oxidation of sulfur by reducing the diffusion of oxygen to some extent. Along with thiolated complementary DNA, another thiolated molecule with a phosphate end group could be attached to PBd-terminated gold nanodots. The repulsive electrostatic interaction between phosphate end groups and the phosphate groups of DNA-templated circuit elements should assist in selective DNA binding. To date, the attachment of polybutadiene to a dithiol monolayer followed by attachment of another thiol moiety (perfluorodecanethiol) onto the surface double bonds has been successfully achieved on a flat Au(111) surface. The attachment of thiolated DNA to a PBd/mercapto silane-coated silicon wafer has also been achieved. Surfaces were characterized by contact angle goniometry, spectroscopic ellipsometry, time-of-flight mass spectrometry, and X-ray photoelectron spectroscopy. Scanning electron microscopy and atomic force microscopy will also be used for characterization of these new materials. In the near future, the stability profile of these polymer-modified surfaces, compared to thiols attached directly to a gold, surface will be studied. We will also demonstrate attachment of thiolated complementary DNA to surface double bonds on planar surfaces, followed by attachment of DNA-templated circuit elements. Once we achieve these goals, the same chemical modification strategy will be applied to gold na...

Nanobiotechnology is the fusion of biology and nanofabrication (Hoch, et al. 1996). Nanofabricated devices are increasingly being used in biological studies, and surface modification methods are important for interfacing inorganic devices with tissues.Nanofabricated implants are used to study brain physiology (Najafi and Wise, 1986). These implants can have cross-sectional dimensions as small as 15 μm. However, the implants cause glial scars that inhibit their operation. Figure 1 shows a model implant, with a trapezoidal cross section (base=200 μm, height=130 μm, top=60 μm, length=2 mm), for studying scar formation. Implants were inserted into the brains of rats and tissue was harvested after 1 hr. to 12 wks. Figure 2 shows a thick (100 μm) section of brain prepared 7 days after implantation; the section was immunolabeled for glial fibrillary acidic protein (GFAP) and imaged in a Bio-Rad confocal microscope. The implantation site is surrounded by GFAP positive material indicative of reactive astrocytes.

The technologies of nanofabrication as applied to inorganic materials and substrates are advanced and continue to develop. These sophisticated processes enable the formation of complex electronic, optical and mechanical devices with feature sizes down to tens of nanometers. Adaptation of these types of processes to surface chemical patterning and topographical patterning provides a new set of experimental tools for investigating biological systems and realizing sensors and devices that require the interaction of biological systems and fluids with inorganic materials and surfaces.In this talk we discuss methods of pattering self assembled monolayers, proteins and antibodies on silicon and glass surfaces by lithography and microcontact printing. This is of utility in a variety of experiments in cell-surface interactions and in sensor devices. In certain types of devices the manipulation of fluids and sieving of molecules is a critical function such as in DNA sequencing6 by electrophoretic separation.

The application of nano- and microfabrication to biology is an emerging area linking engineering and biology. We are using microfabrication techniques to make patterns of specific bioactive molecules on glass and silicon surfaces to study central nervous system neurons and glia. Cell adhesion and tissue reaction to implanted silicon based electronic prosthetic devices are being studied, and the methods expanded to interface neurons with integrated circuits to study their electrical properties. The number, type and distribution of cells adhering to particular portions of a substrate can be influenced by patterning amine groups, proteins or polypeptides. We are using microcontact printing as an alternative to lithography for chemical patterning.Primary cultures of rat cortical astrocytes and hippocampal neurons, and continuous cultures of transformed astrocytes were prepared on microcontact printed patterns produced by an elastomer stamp made from a silicon master. Fig. 1 shows two such patterns prepared by depositing self-assembled monolayers of N1[3-(Trimethoxylsily)propyl] diethylenetriamine (DETA) and octadecyltrichlorosilane (OTS).