ABSTRACT
Through miniaturization down to the molecular scale, the fabrication of innovative devices, systems, and chips dedicated to medical applications becomes possible. The expectations are very high in terms of diagnosis at the early stage of a disease, for new therapies and for increasing the capabilities of medical imagery. Another issue concerns the use of these technologies for the development of new experimental approaches for investigating living systems and for acquiring new knowledge in biology at the cellular and subcellular levels. Indeed, through micro-and nanotechnologies
the manipulation and observations of DNA, proteins, and cells allow new experiments to be conducted in the perspective of investigating in a new way basic fundamental mechanisms of biology. At the core of these systems and methods, nanopatterning is a crucial step as it allows building the interface between the inert part of the device and the biomolecule or cell. During the last decade, many new processes dedicated to immobilize bioentities without denaturing them and with submicrometric spatial resolution have been developed. Among them soft lithography combines easy implementation, low cost, and high throughput, and when combined with capillary assembly, it turned out to be capable of single-molecule resolution or single-cell manipulation. In this chapter, we illustrate these achievements through some examples related to biopatterning, biodetection, and single-molecule manipulations and open perspectives in the field of patterning virus nanoparticles. 7.1 Introduction on a Vision of the Future of
NanobiotechnologiesDuring the last century, two major technologies have emerged and have deeply modified our common perception of science and technology and are shaping our society. The first one is related to the exploding field of semiconductor technology, starting in the 1950s with the last developments of VLSI circuits and the currently penetrating systems assembled under the umbrella of nanoelectronics. The second one is related to the development of molecular biology, starting with the discovery of the structure of DNA molecules in 1953 and the last developments of biotechnologies. Since 2000, many groups around the world are working in the perspective of combining these two blooming technologies. This new field, sometimes called nanobiotechnologies, has been the matter of funding in Europe (starting with the Network of Excellence of FP6 NanoToLife), the United States, and Asia. For most of the projects, applications and patents focusing on the combination of silicon technologies and biotechnologies, the dominant approach consists of using advanced nanoelectronic platforms fabricated massively using VLSI technology for biological or medical purposes. The industrial products, fruits of this kind of investigations, are already appearing
in the market. It is clear today that multisensorial platforms, such as mobile phones, will be used for environment and health monitoring of people. However, this first generation of nanobiotechnology is only a convergence driven by applications of economic interests rather than a true hybridization of the two technological domains. One may then answer what the next technological step will be at the crossroads of nanoelectronics and biotechnologies. Our feeling is that the future generation of systems will incorporate, at the level of individual components, biological species (either molecular or cellular) and artificial devices (electrical, mechanical, or optical) fabricated by modern nanofabrication facilities. This perspective requires many advanced research dedicated to discover the new processes, materials, and technological bricks required for truly achieving hybrid bio-/artificial systems. We believe that these new processes will constitute the basis for future manufactured products arriving in the market at the horizon of 2025. The integration of bio entities is therefore a crucial starting point involving innovative techniques and processes, mixing biological entities with artificial micro-and nanoscale devices. ”Biointegrated” technologies generate a fascinating new technological domain where molecular assembly, nano-objects synthesized with “bottom up” methods, functional proteins, and bionanomachines will drastically change the already rich world of artificial systems. Two mainstreams for the integration of biology in nanotechnologies can be distinguished. The first one referred to as “nanotechnologies for biology” includes the generation of active devices capable of manipulating cells and biomolecules for biomarker detection or tissue engineering as well as modeling of molecular interactions and biological mechanisms. The second one referred to as “nanotechnologies from biology” relies on the fabrication of original nanodevices where the main functionality will be given by a bioentity such as DNA origami, DNA-based nanochannels, and bioassembled materials, to name a few. Integrating bioentities on devices requires a method for locating cells or biomolecules on surfaces with high spatial accuracy, while preserving their biological functionality. This technological process is called biopatterning. The spatial resolution and the quality of the bioentities arrangement on the surface are of great importance for various applications. In this chapter, we will show
why soft lithography and, in particular, microcontact printing (µCP) exhibit specific advantages for advanced biopatterning. This novel lithography method introduced by Whiteside’s group [1] has become a well-established technique, capable of patterning in a highly parallel way a large variety of molecules on arbitrary surfaces for both research purposes and technical applications. Initially, the technique was proposed as a route for creating patterns of selfassembled monolayers (SAMs) [1-3] and was later extended to the patterning of biomolecules [4, 5] as well as functional molecules on surfaces using supramolecular interactions [6]. The transfer of these molecules along well-controlled features is achieved through the use of a patterned elastomeric stamp, typically fabricated from poly(dimethylsiloxane) (PDMS) [7] cast onto a lithographically patterned silicon hard master. This material turned out to possess unique advantages with respect to the printing process, such as its ability to exhibit conformal contact on rough surfaces and its chemical inertness. In the first part, we will show how µCP can be used for the fabrication of DNA microarrays [8]. It has been shown that inking times and contact times of less than 30 seconds give high-quality and high-resolution microarrays. Moreover, it was found that the fluorescence signal emitted by DNA hybridization spots created by µCP was systematically higher compared to similar spots created by conventional tip deposition. To interpret the rapid and efficient adsorption of DNA molecules on a freshly cured PDMS stamp, the presence of PDMS fragments in the elastomeric stamp turned out to improve the quality of the transfer of the molecules [9]. In the second part, we will show that by biopatterning probe molecules at the nanoscale using soft lithography, innovative protein biochips can be produced. The combination of multiplexed nanoscale µCP and label-free optical detection using the principle of light diffraction has indeed been implemented for generating engineered glass slides for label-free analysis [10, 11]. In the last part, we will show how soft lithography can be used for investigating single bioentities. Arrays of single living bacteria [12, 13] and perfectly controlled arrays of single stretched DNA molecules for genetic analysis or medical diagnosis [14] can be produced by combining soft lithography with directed capillary assembly. Using similar principles, periodic bidimensional matrixes
of gold nanoparticles [15] can be fabricated for different applications in the field of plasmonics.
