M\NSTER, Germany ¿ The way Staffan Nilsson of Lund University in Sweden practices chemistry could be compared to the gunslingers in the Old West, who shoot coins after tossing them into the air. He levitates drops of liquids containing few or single cells and shoots them with smaller droplets containing active ingredients or other reagents.
This airborne chemistry platform opens new perspectives for biotechnology by showing a way to investigate single cells and the interactions of very few molecules. Nilsson presented his platform at the ¿Nanobiotech 2001¿ congress in M|nster on Thursday.
What nano means ¿ one-billionth ¿ was illustrated by Eshel Ben-Jacob of Tel-Aviv University. ¿What a football is to earth, a nanoparticle is to a football,¿ he said.
Doing research on the nano level is necessary in life sciences, said Stefan M|llner, director of new business at D|sseldorf-based chemistry company Henkel KGaA. ¿We have to find new technologies that enable us to work with single cells, with protein complexes and to study the ligand interaction with protein complexes, because this is real life.¿
Such requirement needs investigation of very low amounts of substance, which hardly can be done in vials or microtiter plates. The few molecules under consideration in the assay can get lost during any reaction in the assay.
That¿s why Nilsson works on flying drops. ¿You have no surfaces your molecule can adsorb,¿ he told BioWorld International. His team at Lund University has put single primary fat cells into 250 nanoliter drops of buffer, and then levitated the drops using an acoustic levitation device working on ultrasound.
Once airborne the droplets were shot by picoliter dispensers ¿ ¿without splash,¿ Nilsson emphasized. The drops contain _-adrenergic agonists. A pH-dependent fluorophore in the main drop enabled the researchers to detect release of free fatty acid, which correlates with pH.
Shooting additional droplets of water into the main drop compensates for evaporation during the assays.
Using its airborne chemistry technique, Nilsson¿s team can perform several chemical techniques. For example, the levitation approach decreases time for crystallization of proteins to a range of one to 3 days vs. one year using conventional methods, Nilsson explained. Crystallized proteins are then open to structure identification.
The platform is highly flexible. pH is not the only parameter open to remote detection. ¿[We can investigate] whatever you can follow by laser-induced fluorescence,¿ Nilsson said. ¿If we take the drop out we can do all the biochemical analysis we want to do.¿
In Nilsson¿s vision even ¿3-dimensional arrays sitting in the air¿ seem possible. ¿We haven¿t focused on it. But you can do this on piezoelectric chips. I¿ve been speaking with people about it and it should be possible.¿
Nilsson¿s work has inspired a group of researchers from academia and from companies.
They also don¿t like walls for chemistry.
They invented a 2D/3D Biochip, which they expect to facilitate DNA and proteome research, drug discovery and assays in a high-throughput manner.
On 2D/3D biochips nanoliter droplets containing proteins are standing upright. The chip¿s body of glass, plastic or metal is coated with a hydrophobic film. But there are very tiny holes in the film. These holes are hydrophilic spots, perfectly round. They act as anchors for droplets containing the biomolecules of interest. There may be any ligands on the anchors. The chips may be loaded by an application device or by dipping the whole chip into a solution with the substance of interest.
The platform is open to many applications. ¿Everything you can examine in a liquid, you can also examine on these chips,¿ said Sebastian Delbr|ck, vice president of business development at Berlin-based Scienion AG, which commercializes the technology. As examples he named investigation of protein-protein-interactions. There is space enough for thousands of droplets on a chip as big as a microscope slide.
Once made, the life span of the droplets depends on evaporation, which can be controlled in a humidity chamber. But in some cases evaporation may be wanted. ¿If you let DNA containing drops dry, you¿ll get a fine DNA array afterward,¿ Delbr|ck said.
Scienion got a license to the technology from Max Planck Gesellschaft (MPG), of Munich.
Protagen AG in Bochum also seeks a license from MPG to commercialize the 2D/3D biochips for proteomics applications, Protagen¿s CEO Christoph H|ls told BioWorld International.
Single biomolecules are in the focus of Filipp Oesterhelt, chief scientific officer and co-founder of Grdfelfing, Germany-based Nanotype GmbH. Nanotype specializes on single-molecule force measurements using the atomic force microscope.
¿We have learned that force measurements on single molecules reveal new insights into interactions between receptor ligand systems,¿ Oesterhelt told BioWorld International.
Using this technique enables researchers, for example, to ¿look how strongly antigens and antibodies interact or whether DNA has a mismatch or not. You can investigate those interactions with the parameter force, and can get insights on that.¿
Nanotype developed a technology, paralleling such investigations, doing tens of thousands to millions of single molecule measurements at once. This opens the technology to industrial biotechnological applications, making it available for use in high-throughput processes, for example.