Hybridization signal amplification method
Hybridization signal amplification method (HSAM), developed by Hamilton Thorne Bioscience, is an elegantly simple signal amplification method that takes advantage of some of the unique structural capabilities of nucleic acids. It is a companion to ramification amplification method (RAM). Conceptually, HSAM can be thought of as a variation on traditional probe network signal amplification schemes, updated by incorporation of cutting-edge nanostructure concepts. HSAM can be used to detect nucleic acids, proteins, or other small molecules that might typically be measured by immunoassay.
In practice, a ligand-derived probe (nucleic acid or antibody) reacts specifically with the target molecule. Then, a self-assembling, structurally defined nanostructure, comprised of short ligand-derived nucleic acids and multivalent anti-ligand molecules, is introduced to bind to the target-bound probes.
Components of the nanostructure can be derived from a variety of signal-generating moieties – e.g., fluorescent tags for direct detection or enzymes that can themselves generate detectable moieties in an indirect fashion – to suit specific applications. The nanostructure provides a many-fold greater surface area for supporting detection moieties than the probe molecule itself.
HSAM is an attractive alternative to enzymatic amplification systems in situations where simplicity and speed are primary criteria in assay design. It should be particularly useful in solid phase or microarray types of applications where enzymatic amplification/detection can be cumbersome. HSAM also expands the signal amplification capabilities beyond nucleic acids to include proteins and other small antigens in the same analytical system. RAM and HSAM (Hybridization Signal Amplification Method), represent the next generation of technology after PCR. RAM and HSAM have significant advantages in sensitivity, multiplexing, quantification, and dynamic range over older amplification methods and offer real-time, super-exponential amplification. These technologies are capable of detecting, quantifying and analyzing all classes of biomolecules, including DNA, RNA and proteins. The high sensitivity is singularly appropriate for detection down to the levels of single cells and even single molecules (rare events). This method is also used with extreme simplicity and sensitivity to detect viruses and bacteria in clinical specimens. In-situ (on a slide) detection of multiple viral sequences in cells is also possible using RAM technology. Most importantly, much of the work performed with RAM and HSAM has been done on actual clinical samples and not in idealized research laboratory conditions. Other advantages of RAM and HSAM over current amplification techniques include:
1. The platform offers high specificity and reproducibility.
2. Multiplexing: Simultaneous measurement is possible of many protein analytes or DNA sequences. The objective is rapid and low cost analysis.
3. This technology can quantify target analytes or sequences over a wide dynamic range and with an accuracy that is considerably above current methods.
4. Simple preparation and high throughput: Some of the formats require only one step to perform the assay, bringing DNA analysis on level with the ease and low cost of common clinical tests.
5. The RAM/HSAM platform is highly effective in solution, on solid surfaces such as biochips, in microfluidics, with a wide range of solid supports and as a slide based cell assay.
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