Sensitive detection and identification of DNA and RNA using a patterned capillary tube.

We report on a new ultrasensitive and fast technique for the detection and identification of both DNA and RNA with sensitivity of a few molecules. The new method is based on a patterned capillary tube (PCT) in which the internal surface of a glass tube is patterned with rings of different single-stranded DNA probes. A solution containing single-stranded analyte flows through the tube. Upon hybridization of appropriate DNA and RNA from the solution, DNA polymerase and reverse transcriptase (RT) are employed to synthesize the complementary nucleic acids with deoxynucleoside triphosphate (dNTP) labeled with fluorophores. The sample-analyte hybrids are detected by their fluorescence signal. We show that the new method is sensitive, is specific, can detect simultaneously both DNA and RNA from the same sample, and allows detection of analytes in serum.

Patterning gradient properties from sub-micrometers to millimeters by magnetolithography.

A new method is presented for patterning surfaces with gradient properties. The method is based on magnetolithography in which the surface patterning is performed by applying a gradient of a magnetic field on the substrate, using paramagnetic metal masks in the presence of a constant magnetic field. Superparamagnetic nanoparticles (NPs) are deposited on the substrate, and they assemble according to the field and its gradients induced by the mask. Once they pattern the substrate, they protect their sites on the substrate from interacting with any other species. The areas not protected by the NPs can be covered by molecules that chemically bind to the substrate. After these molecules are bound, the NPs are removed, and other molecules may be adsorbed on the newly exposed area. The new technique is based on a parallel process that can be carried out on a full wafer. It provides high resolution, it creates gradient continuously from sub-micrometers to millimeters, and it can be performed on surfaces that are not flat and that are even on the inside of a tube. The gradient that is formed is not limited to a specific property or type of substrate.

Magnetolithographic patterning of inner walls of a tube: a new dimension in microfluidics and sequential microreactors.

By applying magnetolithography it is possible to chemically pattern the inside of tubes. This new capability allows one to perform sequential processes within the tubes. Several enzymatic reactions are demonstrated.

Submicrometer chemical patterning with high throughput using magnetolithography.

This letter demonstrates the ability to pattern surfaces chemically with submicrometer resolution by applying the simple and inexpensive magnetolithography (ML) method. This method allows fast patterning of large surfaces without having to face contamination problems or the need to remove the substrate from the solution. With ML it is possible to obtain pattern whose width is narrower than the width of the lines in the mask. By applying the green fluorescent protein (GFP), we were able to probe a 30 nm line of hydrophobic molecules patterned on a substrate coated with a hydrophilic monolayer.