The Lab on Foil: Fast and Economic Diagnosis
Molecular genetics makes early diagnostics of several diseases possible. So far, however, in most cases complex analyses in the laboratory are necessary to enable this. The scientists at the Fraunhofer EMFT and the KTH Royal Institute of Technology in Sweden are currently working on cost-effective miniature labs on foil, poised for a fast point-of-care diagnostics.
Cancer is still one of the scariest threats for most people. It is still the second most common cause of death in Germany, as communicated by the federal office of statistics on the world cancer day in February this year. Admittedly, several alternatives for effective treatment already exist, but in most cases the therapy success and chances of recovery greatly depend on detecting the disease at an early stage. The illness leaves its marks in the human body long before the first symptoms occur - they can be detected, for example by taking a very deep look into the microcosmos of a single cell on DNA level. Molecular genetic analyses offer great potential for giving the physicians a time advantage in the battle against cancer. An example: Certain single nucleotide polymorphisms (SNP) - alterations in single base pairs of our DNA - can be associated to certain types of cancer. Scientists have also detected a correlation between another SNP and diabetes. Further, molecular genetics opens up new possibilities for fighting dangerous infectious diseases such as malaria. So far, viruses and bacteria are generally detected via antibodies in the blood of the patient, meaning they can only be detected after a certain incubation period. However, direct detection of the pathogenic DNA not only makes earlier detection of the infection possible but also enables exact determination of the specific subtype of the pathogen.
In order to be able to examine the DNA, it first has to be isolated from the blood sample. In the next step, the relevant DNA sequences are multiplied using the polymerase chain reaction (PCR). For subsequent detection of the diagnostic markers in PCR product, several possibilities exist. One common method for detecting SNPs in a PCR product is the so called melting curve analysis, where the double-stranded DNA segments are slowly heated.
The DNA double-strands containing a mutation are more instable than the normal double-strands, which is why they dissociate at lower temperatures and can thus be identified. As yet, only well-equipped central labs provide the infrastructure required for such complex examinations. This makes them too time-consuming and expensive to be established as a standard practice. In order to be able to utilize molecular genetic examinations routinely in every-day medical practice, they first have to become considerably more affordable and easily executable at the point-of-care.
An Analysis System in Matchbox Format
How this could function is demonstrated by the scientists at the Clinical microfluidics lab at KTH Royal Institute of Technology in Stockholm and the Fraunhofer Research Institution for Modular Solid State Technologies EMFT in Munich. They have developed a measurement system on foil for the melting curve analysis, approximately the size of a matchbox. In addition to the microfluidic and microarray technologies, they have succeeded in integrating the heating elements on polymer foils for the first time. They are applied on a thin polyethylene naphthalate foil (PEN foil) by the means of photolithography. The heater rods are structured as a grid and enable a more even heat distribution than the conventional heating elements in meander format. A further benefit of the grid structure is that if a single conductor break, the heating system still continues to function. The heating element is encapsulated by a 2 µm thin parylene layer. On this layer the DNA strands serving as reference are immobilized, which then catch the multiplied complementary strands from the patient blood sample. A 50 µm thick double-sided adhesive foil containing the contour of a microfluidic structure is laminated over the heater foil. Another PEN foil seals the system to create a closed microfluidic channel for transporting the patient sample into the reaction chamber.
Fast Point-of-care Analysis
The „Lab-on-foil" is well suited for serial production: The polymer foils can be produced roll-to-roll and are considerably cheaper than micro arrays made of glass or silicone. Moreover, the system could use a 2 Volt battery as power supply and thus do without a power connection, unlike the stationary equipment. These characteristics predestine the development for point-of-care diagnostics, where small, simple analysis systems with disposable cartridges are needed. These enable physicians to carry out the examinations directly in the medical practice instead of sending the samples to a central laboratory for analysis, thus significantly reducing the cost and waiting time for the results. Beyond that, such mini-labs could improve healthcare in secluded areas or in developing countries.
Increasing Importance of Molecular Genetics
The need for simple systems for point-of-care diagnostics is likely to increase in the future, especially since molecular genetics is continuously gaining recognition as a crucial technology for medical progress. Scientists all over the world are working on identifying new diagnostic markers, expected to bring significant progress to the diagnosis and therapy of various diseases. The results could for example enable much faster and more exact identification of a specific subtype of a pathogen for infectious diseases. This could help reducing multiresistances against antibiotics, since the medication could be carefully targeted at the specific pathogen in question. False diagnosis could thanks to moleculargenetic procedures, saving the patient unnecessary operations or therapy and resulting in financial savings in the healthcare system. In this context, scientists are for example working on identifying SNPs as a diagnostic marker for prostate cancer. Further the methods of molecular genetics are gaining importance due to the trend towards "personalized medicine", aiming at developing tools for prediction of disease and individualized therapies customized for each patient. Test methods for quick and reliable determination of the most useful therapy for one specific patient are essential for this approach.
„Sample-to-answer-System" as a long-term goal
The miniature lab-on-foil has already successfully passed the first proof-of-principle test: the project partners analyzed the polymorphism "Leu7Pro". This modification in the neuropeptide Y indicates an increased risk of becoming diseased with diabetes type II or depression. Preparing the samples as well as multiplying the DNA was however carried out using a standard PCR machine in the study. Also the measurement setup for power supply, process control and data collection is currently based on using conventional laboratory equipment. The long term aim of the scientists is to integrate these steps into a miniaturized, portable format, and thus create a complete "Sample-to-answer" system. This shall then be deployable also for complex diagnoses, such as infectious diseases identified by combinations of different DNA strands containing certain point mutations (SNPs) as diagnostic markers.