Peptides from the laser printer
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- Biochips from the laser printer. Instead of colour pigments, printed here are protein building block peptides - to customer specification. Source: PEPperPrint
28.04.2011 -
Miniature biochips are indispensable in the modern laboratory. Tiny samples are already enough for a thorough analysis of biochemical details. This enables the detection of bacteria, the identification of antibodies, or the testing of pharmaceuticals in the development stages. However, the production of these biochip is no easy undertaking. A team of scientists from the German Cancer Research Center (DKFZ) in Heidelberg and the Fraunhofer Institute for Manufacturing Engineering and Automation (IPA) in Stuttgart is pursuing an entirely new approach, and has developed a form of printer for biochips. A few years ago, the researchers founded the company PEPperPRINT on the basis of this idea. The new company is being funded up to market-viability by the Federal Ministry of Education and Research.
Biochips - also known as arrays - are long established as a standard tool in the life sciences. Following the example of computer chips - i.e. accommodating masses of information in the smallest space - the first biochip was introduced 20 years ago, and has been under continuous development since that time. They are essentially used to perform a large number of simultaneous biological tests on a very small space, such as the detection of genetic mutations, or of a variety of gene activities or proteins. Pathogens such as viruses or bacteria can be detected, for example, using so-called peptide arrays. Small protein fragments (peptides) present in the pathogens are attracted to specially coated plastic or glass plates. Like bait on a fishing line, peptides are able to fish out antibodies from patients’ blood, which can then shed light on diseases. The microchips can also be used to search selectively for peptides that could be used for cancer therapy, or which could be considered as potential vaccines against specific diseases.
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The problem lies in the production
The application possibilities in diagnostics, basic research, or in industry, are diverse. However, arrays of this type have a manufacturing problem: The previously used commercial technique in which individual protein components - i.e. amino acids - are spotted onto a membrane with a pipetting robot, is highly cumbersome. The capacity of the biochip is also limited - a maximum of 10,000 peptides can fit onto such a carrier. That might sound like a lot, but biochips with 100,000 peptides are needed to represent all of the thousands of proteins of a typical bacterium, each in the form of 100 overlapping peptides. For a malaria pathogen, this is already 500,000, and as many as four million for the full proteome of a human being. Another disadvantage of the spotting technique: a single peptide spot costs about 5 euros - a total of 10,000 peptides therefore comes to almost 50,000 euros.
"This makes absolutely no sense," says Ralf Bischoff. In 2001, the scientist from the German Cancer Research Center (DKFZ) in Heidelberg, together with his colleague Frank Breitling, founded the biotech company PEPperPRINT. Their idea: To find a means of mass-producing the peptide arrays. Together with researchers from the Fraunhofer Institute for Manufacturing Engineering and Automation (IPA), the scientists at PEPperPRINT have taken their own path: Cost-effective printed peptides.
Amino acids from the toner
The peptide printer from the DKFZ researchers is made possible by bio-toners: Instead of colour pigments, these are filled with amino acid particles; originally an idea from Breitling, who has recently took up a position at the Karlsruhe Institute of Technology. The peptides must also be linked to up to twenty different amino acids, representing another challenge for the engineers. This problem was solved by the team of IPA researchers led by Stefan Güttler: They developed a special laser printer that, with high accuracy and high throughput, can print any desired combination of 20 different amino acids onto a tiny glass plate. "The amino acids in the toners are embedded in microparticles, which gives them protection and makes them storable. We could not detect any decay even over a matter of months," says Bischoff of his system. The plate is heated to bring the amino acids into a solution, because the amino acids can only chemically react in dissolved form." The toner particles are melted in this process, and the amino acids can couple with the carrier. These are then printed and chained together in an exact process, layer by layer. "With each printing pass, the peptide chain is extended by exactly one amino acid. Thereby, a ‘protection group’ takes care of the reactive nature of the amino acid. After each extension, this is cleaved off with a basic solution so that the next amino acid can bind," says Bischoff. Block by block, the process continues until the desired peptide is chained together.
Precision required
The technique developed by the Heidelberg-based biotechnology company seems to have come of age: Already with their first printer, the PEPperPRINT scientists were able to produce biochips with 160,000 peptides on a carrier measuring just 20 square centimetres. Today, the latest generation laser printer is up and running: “Arrays of 250,000 peptides can be printed without issue. Over 500,000 peptides are theoretically possible with this printer," says Bischoff.
What tips the balance is precision. Only with super-stable components and finely tuned automatic adjustment is it possible to print 20 amino acids accurately in such a density. But these kinds of precise components are not something you can pick up in the shops: The new printer weighs all of four tons - its predecessor was just half a tonne.
| Background |
The following sites will tell you more about the PEPperPRINT scientists and the development of the peptide arrays. Click here to visit the PEPperPRINT website. Click here to visit the IPA website. Click here to visit the German Cancer Research Center website. |
Innovation in demand
The scientists have been able to bring down prices using their printing technology. The finished arrays can be provided for as little as 13 cents per peptide. "Our technology will facilitate research projects that would simply have been too expensive," says Bischoff.
This pioneering project in the field of biochips has brought the researchers a number of renowned science and business prizes in recent years, and throughout they have been continuously supported across a range of projects by the Federal Ministry of Education and Research (BMBF). Just recently, As part of the 3-year KMU (SME) funding initiative, the young innovative company received almost one million euros from the Ministry - up to March 2013 - for the development of highly complex peptide chips.
Print-off and send-off
The PEPperPRINT method is now set for further optimisation: The researchers plan on creating biochips that can be printed with even more peptides, and even more accurately and quickly. These could potentially facilitate the development of diagnostic tests for previously difficult-to-decipher diseases.
Since the spring of 2010, under the leadership of Volker Stadler, the company has stepped up its business activities with an aim to finally achieving market viability.
In 2012, Bischoff will be giving up his research post at the DKFZ to take up his position as Chief Scientist in the company. A current hot topic at PEPperPRINT headquarters is customer service: To date, individual peptide arrays could be ordered by customers by e-mail. Together with a software developer, they are working on a system that will enable customers to quickly, conveniently and directly place orders for specific peptides. “A bit like at home, when you create a PDF and finally send it to the printer,” says the researcher. “However, it takes a little longer than at home.” Indeed, one should reckon on two to three weeks before a peptide chip is fully printed.“
