In-situ concatenation of oligo-nucleotide probes for target detection

A multiplicity of hairpin loop forming nucleic acid probes capable of concatenating in situ to form a concatenated probe complementary to a target nucleic acid sequence, each nucleic acid probe of the multiplicity comprising:

• a nucleic acid sequence complementary to the target nucleic acid sequence;
• a 5′ flanking sequence comprising a first detection moiety;
• and
• a 3′ flanking sequence comprising a second detection moiety,
• wherein the 5′ flanking sequence and the 3′ flanking sequence of a single nucleic acid probe are at least partially complementary to each other;
• wherein the multiplicity of nucleic acid probes comprises at least two populations of probe;
• a first population characterized in that the first detection moiety and the second detection moiety on a single nucleic acid probe are the same and are each of type A;
• and second population characterized in that the first detection moiety and the second detection moiety on a single nucleic acid probe are the same and are each of type B;
• wherein said multiplicity of nucleic acid probes are capable of concatenating in situ to form a concatenated probe complementary to the target sequence, in which probes of the first population alternate with probes of the second population, such that the 5′ flanking sequence of a first nucleic acid probe of a first population interlinks with at least part of the 3′ flanking sequence of a neighboring nucleic acid probe of the second population to form a stem structure such that the first detection moiety of the first nucleic acid probe and the second detection moiety of the neighboring nucleic acid probe of the stem structure interact to generate a signal.