Biology

A novel and simple microcontact printing technique for tacky, soft substrates and/or complex surfaces in soft tissue engineering

Abstract

Microcontact printing (μCP) has attracted much interest due to its simplicity and wide range of applications. However, when conventional μCP is applied to soft and/or tacky substrates, substrate sagging and difficulty in stamp removal cause non-conformance in the patterns. Moreover, it is almost impossible to apply conventional μCP on complex or wavy surfaces. In this study, we developed a novel yet simple trans-print method to create efficient micropatterning on soft and/or tacky substrates such as polydimethylsiloxane and polyacrylamide gel, and also on curved surfaces, by introducing polyvinyl alcohol film as a trans-print media. This technique is simple as it only involves one trans-print step and is also cost-effective. Most importantly, this technique is also versatile and we have proven this by printing various designs on more complex non-flat surfaces using various proteins as inks. The quality of the trans-printed pattern was excellent with high reproducibility and resolution as verified by immunostaining. Human mesenchymal stem cells cultured on these patterns displayed good conformance on the soft and tacky substrates printed using this technique. These results suggest that this novel trans-print technique can be extended to a potentially generic methodology for μCP of other proteins and biomolecules, other shapes and sizes, and cells, and will also be useful in three-dimensional micropatterning for soft tissue engineering.

Link

A novel and simple microcontact printing technique for tacky, soft substrates and/or complex surfaces in soft tissue engineering

Optical Label-Free Biodetection Based on the Diffraction of DNA Molecular Gratings for In Vitro Diagnostic

Abstract

Development of biodetection techniques has become the matter of intense research in the field of bioassays. Modern DNA microarrays now target in vitro diagnostics and allow simultaneous identification of several hundred biomarkers. Thus, targeting complex diseases due to the deregulation of several genes can be reached. However some technological bottlenecks slow down the blooming of this technology. Our research focuses on microarray improvement for in vitro diagnostic by implementing nanotechnology processes in order to reduce the cost of multiplexed analysis. For immobilizing the probe molecules at the surface of the biochip, we selected a modified microcontact printing technique which enables us to generate patterns of probe DNA fragments of arbitrary shape and dimensions while preserving the capability of multiplexing in one printing step. Due to its submicrometric resolution, this biopatterning method has been used to generate periodic arrays of DNA probe molecules (1micron pitch). We demonstrated that these molecular gratings efficiently diffracted light from a laser beam. We exploited the changes in the diffracted intensity of these gratings to perform a label-free optical biodetection. In this contribution, using a modified scanner system capable of collecting at high speed the diffracted intensity, we could perform detection of specific DNA fragments (from 25pb to 320pb). Based on this principle, we show that we are able to detect a change of signature due to DNA hybridization. This biodetection method should allow detection of specific gene targets from an analytical solution and will solve the technological bottleneck of target labeling required for fluorescence read out. Test validation of this technology focuses on a dedicated DNA microarray used for screening validated genetic signatures for breast cancer diagnostic as a new medical tool helping the orientation of therapies.

Link

Optical Label-Free Biodetection Based on the Diffraction of DNA Molecular Gratings for In Vitro Diagnostic

Biological functionalization of massively parallel arrays of nanocantilevers using microcontact printing

Abstract

In this paper, we present a back-end method for biofunctionalizing a large-scale array of nanocantilevers. Our method relies on the use of a modified microcontact printing process where molecules are delivered onto the fragile structures from the grooves of the stamp while its base sits on the chip, thus providing mechanical stability. We have used this method to print antibodies onto fabricated chips containing up to 105 nanostructures/cm2and the presence of antibodies was validated by fluorescent microscopy. Furthermore, measurement of the nanocantilever resonant frequency shifts provoked by a mean added mass of ∼140 fg/cantilever demonstrated that the cantilevers retained their mechanical integrity. Hence, the method presented here aims at providing an answer to the biofunctionalization of freestanding nanostructures for their use as biosensors.

Lien

Biological functionalization of massively parallel arrays of nanocantilevers using microcontact printing

Page 5 of 35