page_title: Rolling circle replication
section_title: Immuno-RCA
hierarchical_section_title: Rolling circle replication / Applications of RCA / Immuno-RCA
caption_attribution_description: English: Illustration of aptamer based immuno-rca
context_page_description: Rolling circle replication is a process of unidirectional nucleic acid replication that can rapidly synthesize multiple copies of circular molecules of DNA or RNA, such as plasmids, the genomes of bacteriophages, and the circular RNA genome of viroids. Some eukaryotic viruses also replicate their DNA or RNA via the rolling circle mechanism.
  As a simplified version of natural rolling circle replication, an isothermal DNA amplification technique, rolling circle amplification was developed. The RCA mechanism is widely used in molecular biology and biomedical nanotechnology, especially in the field of biosensing.
context_section_description: Immuno-RCA is an isothermal signal amplification method for high-specificity & high-sensitivity protein detection and quantification. This technique combines two fields: RCA, which allows nucleotide amplification, and immunoassay, which uses antibodies specific to intracellular or free biomarkers. As a result, immuno-RCA gives a specific amplified signal (high signal-to-noise ratio), making it suitable for detecting, quantifying and visualizing low abundance proteic markers in liquid-phase immunoassays and immunohistochemistry.
  Immuno-RCA follows a typical immuno-absorbent reaction in ELISA or immunohistochemistry tissue staining. The detection antibodies used in immuno-RCA reaction are modified by attaching a ssDNA oligonucleotide on the end of the heavy chains. So the Fab (Fragment, antigen binding) section on the detection antibody can still bind to specific antigens and the oligonucleotide can serve as a primer of the RCA reaction.
  
  The typical antibody mediated immuno-RCA procedure is as follows:
  1. A detection antibody recognizes a specific proteic target. This antibody is also attached to an oligonucleotide primer.
  2. When circular DNA is present, it is annealed, and the primer matches to the circular DNA complementary sequence.
  3. The complementary sequence of the circular DNA template is copied hundreds of times and remains attached to the antibody.
  4. RCA output (elongated ssDNA) is detected with fluorescent probes using a fluorescent microscope or a microplate reader.
caption: Illustration of aptamer based immuno-rca
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