Author: İrem Duman, University of Ege Department of Bioengineering
Lab-on-a-chip systems allow the long-term chemical analysis or DNA sequencing on miniaturized devices which normally done in the laboratory. It replaces many laboratory assays and instruments with novel intelligent chip designs. The scientist discovered this system integrated with fluidic, electronic, optical, biosensor systems and additional properties. Why do we want to do build such small systems like that?
The main idea for these systems is to reduce the cost of biochemical analysis, increase the efficiency of the assays or getting the results faster and making it portable. Initially, cost-effective and time-saving diagnosis methods in hospitals are aimed to be developed.
It may be wondered, how a flow or chemical analysis system can be formed inside really small devices at micron or nanoscale. The physical principle about microscale flow is the Reynolds numbers which give the flow characteristic of liquids inside nano-pico liter volume. Liquid flow through the micro-channels is mostly in the laminar flow regime. The regularity of flow within channels allows controlling of the interactions and molecular concentrations. In this way, the usage of different physical and chemical process properties that are not possible in large instruments becomes applicable inside the microfluidics.
History of LOAC
In the 1950s, studies on the miniaturizing of the technological tools have started by the initialization of the Apollo program in America. The search for small and functional devices to go into space brought nano and micro technologies in our daily lives. Over the years, research on this subject has been increased. In the 1979 S.C. Terry has created the first demonstration of lab-on-a-chip technology at Stanford University. This first study was based on gas chromatography.
After this development, until the end of the 1980s, there wasn't any significant research about this technology. Around the 1980s many research groups were set up in Europe and in the 1990s, many scientists began to work on the miniaturization of biochemical reactions and processes. The initial studies were about the miniaturization of PCR analysis. Afterward, the research about electrophoresis, DNA microarrays, and cell lysis applications have been almost done and commercialized. Later on, DARPA interested in this technology and developed portable detection systems.
These developments contribute to the development of lab-on-chip technology. It is still a new technology but today there are many research groups working on this subject. Numerous articles and books were written by the researchers on the properties of these miniaturized processes and portable bio-analytical systems.
Lab-on-a-chip Systems and Diagnostics
Point of care (POC) devices are used frequently in hospitals and at homes by their ability to obtain rapid and sensitive results. The other advantages are, no need for trained personnel for usage, less reactive chemical usage, small portable sizes, low power consumption, multiple and parallel analyses, low cost and mobility compared with traditional clinical test systems. POC devices are capable of analyzing various target molecules such as proteins, nucleic acids, cells or metabolites. Metabolite analysis has brought diabetic tracking and detecting devices that are frequently used even inside at home, comfortably. One of the popular examples of cell counting system is; counting of CD4 cells for the diagnosis of infectious diseases. Protein count and detection is another important area for POC devices. Immunoassay systems have been developed using antigen-antibody interactions and proteins. Immunoassay methods are important for human health so researches about immunoassay-based LOAC systems is increasing by the time.
The widely used Triage system, which works with immunoassay measurement, is a successful POC device. It is important that the patients who come to the emergency service with chest pain must be quickly diagnosed and treated. The triage device is based on immunofluorescence detection of cardiac proteins. After the blood sample is taken, red blood cells and plasma are separated from each other within the device. Plasma enters the reaction circle inside the device. Fluorescence antibody conjugates are inside this reaction chamber waiting for the sample. Cardiac proteins in the plasma react with these antibodies. Flow occurs with the help of the microfluidic pumps and valves. This mixture moves through the device. Finally, the result is shown with the fluorescence staining technique. This process takes about half an hour.
Gervais and Delamarche at IBM developed another lab-on-a-chip system using silicon and PDMS materials. Detection and capture of antibodies are made possible by sample flow provided by the low flow rate pumps and low volume valves. For the results, a fluorescent staining technique is used. As a result, a sensitivity of 1 ng / mL CRP, which is good for detecting myocardial infarction in human serum, was obtained. These systems can be used in emergency services, in the ambulance or in the field by the health officials because of the rapid, sensitive diagnostic properties and the small size.
Future Perspective and Conclusion
LOAC usage has many advantages like low-volume sample use, parallel multi-sample experimentation, micro scales, low weight, and low cost. The applicability of these systems in the medical field will help accuracy. Today, several microfluidic devices are already in use for better human health and play a key role such as infection, diabetes and heart attack detection. For almost all diseases it is vital that the diagnosis is placed quickly and accurately.
It enables the development of treatment and the appropriate service of the patient. In the future maybe we can use a POC device in our home for detecting cancer in the early stages. Lab-on-a-chip technology can use a wide range of applications from environmental research to drug tests. In the following years, it is quite possible to encounter devices developed with this system at many points in our lives.
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