Devices for Nucleic Acids Analysis

Microfluidic concepts can be used to develop an integrated total chemical analysis system (TAS) [40], which include sample preparation, separation, and detection. The microminiaturization of a TAS onto a monolithic structure produces a //-TAS that resembles a small sensor. The first /(-TAS was a micro-gas chromatograph (GC) fabricated on a 5-in. silicon wafer in 1979 by a group at Stanford University [41]. Since then, developments in micromachining has led to the development of microsensors, microreactors, 

The /i-TAS offers some excellent possibilities and is in a state of rapid development. However, several challenges need to be overcome for their successful real-world implementation. For example, detection limits are low due to the small sample size, and the principal detection method so far is laser-induced fluorescence, which offers high sensitivity and low detection limits. Other problems include interfacing microfabricated devices to conventional macro-size instruments and fluid handling. 

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The second section is dedicated to the preparation for nucleic acid analysis. Specific examples of DNA and RNA analyses are presented, along with the description of techniques used in these procedures. Sections on high-throughput workstations and microfabricated devices are included. The third section deals with sample preparation techniques used in microscopy, spectroscopy, and surface-enhanced Raman. 

The classical methods on DNA detection are time-consuming and labor-intensive. However, wide-scale genetic testing requires the development of fast, inexpensive, and sensitive miniaturized devices. Thus, biosensors offer a promising alternative for faster, cheaper, and simpler detection protocols for nucleic acid analysis. These biosensors commonly rely on the immobilization of double-stranded DNA (dsDNA), single-stranded DNA (ssDNA), or an oligonucleotide... 

Quake and coworkers [16] developed a PDMS microfluidic device (shown in Eig. 4c) for nucleic acid purification from a small number of bacterial or mammalian cells. This multilayer device contained fluidic channels and a system of membrane-actuated pneumatic valves and pumps, which enabled precise control of buffers, lysis agents and cell solution, and also allowed for parallel processing. Bacterial cells, dilution buffer and lysis buffer are first introduced into the chip and then transferred into the rotary mixer. Once mixed, the lysate is flushed over a DNA affinity column and drained. The DNA is recovered from the chip with an elution buffer for further analysis. We note that this is the only microfluidic chemical C3flome-try device to use a separation method other than solution-phase electrophoresis (i. e., solid phase extraction). 

Lab-on-a-chip devices of this kind, so-called micro-total analysis systems ((xTAS), are textbook examples of how an appropriate reactor design considerably facilitates analyses. These systems benefit from highly efficient heat transfer in different reaction zones, thus allowing for realizing a complete sequence of different reactions within a single reaction channel. It is for these reasons that jtTAS are particularly well suited for nucleic acid analyses by means of the polymerase chain reaction (PCR). Other fields of application comprise molecular diagnostics or forensics [53]. 

Pellestor F, Paulasova P, Hamamah S. Peptide nucleic acids (PNAs) as diagnostic devices for genetic and cytogenetic analysis. Curr Pharm Des. 2008 14 2439-44. 

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