Nucleic acid aptamer-based diagnostic methods with novel techniques for signal enhancement

Abstract

The present invention concerns methods for the detection f target molecules in a sample including several steps of signal amplification allowing the detection of a very low number of target molecules in the tested sample. The detection assay is based on the use of a universal probe which enables the signal amplification. The specific recognition of the target molecule is achieved by using a specific binding agent, preferably an aptamer. The invention further concerns kits and methods for the diagnosis of pathological conditions.

1 . A method for the detection of a target molecule in a sample comprising:
 a. obtaining at least one binding agent capable of binding to said target molecule, wherein said at least one binding agent is bound to a matrix;   b. incubating said at least one binding agent which is bound to the matrix with a blocking agent, thereby blocking free active groups on the matrix, wherein said active groups are primary NH 2  or COOH groups;   c. incubating said at least one binding agent which is bound to the matrix with the sample under conditions allowing the binding of the binding agent to the target molecule; thereby forming a matrix-binding agent-target molecule complex;   d. contacting the matrix-binding agent-target molecule complex formed in step (c) with a polymer associated with a member of an affinity couple wherein said polymer further comprising a reactive group; thereby forming a matrix-binding agent-target molecule-polymer complex; and   e. contacting said matrix-binding agent-target molecule-polymer complex with a complementary member of said member of an affinity couple, wherein said complementary member is associated with a detectable moiety, wherein the amount of said detectable moiety is indicative, of the presence of said target molecule in the sample wherein said target molecule is a viral antigen, a cancer marker or a soluble antigen selected from the group consisting of soluble cancer markers, inflammation-associated markers, hormones, cytokines, drugs, viral derived soluble molecules, bacterial derived soluble molecules and fungal derived soluble molecules.   
     
     
         2 . A method according to  claim 1 , wherein said binding agent is an aptamer, an antibody, a receptor ligand or a molecular imprinted polymer. 
     
     
         3 . A method according to  claim 2 , wherein said binding agent is an aptamer. 
     
     
         4 . A method according to  claim 3 , wherein said aptamer comprises reactive groups and said matrix is pre-coated with a protein, and wherein said aptamer is bound to the matrix, thereby forming an aptamer-matrix complex. 
     
     
         5 . A method according to  claim 1  wherein said blocking agent is selected from a group consisting of DMP, citraconic anhydride, sulfo-NHS-Acetate, glutaraldehyde, photo-reactive groups, N-acetylcysteine and N, N′-Methanetetraylbis(2-propanamine) (DIPCDI). 
     
     
         6 . A method according to  claim 1  wherein said member of an affinity couple associated with the polymer is biotin. 
     
     
         7 . A method according to  claim 1  wherein said polymer is a nucleic acid molecule. 
     
     
         8 . A method according to  claim 1  wherein said reactive groups are reactive with primary NH 2  or COOH group. 
     
     
         9 . A method according to  claim 1  wherein said reactive group is a succinimidyl ester group or Tosyl. 
     
     
         10 . A method according to  claim 1  wherein said target molecule comprises a primary NH 2  or COOH group. 
     
     
         11 . A method according to  claim 7  wherein said nucleic acid molecule is a single stranded nucleic acid forming a complex with biotin during a branched nucleic acid process or as a pre-prepared branch unit. 
     
     
         12 . A method according to  claim 1  wherein said complementary member of said member of an affinity couple is a biotin-binding protein. 
     
     
         13 . A method according to  claim 1  wherein said detectable moiety is an enzyme capable of catalyzing a reaction producing a detectable signal and a suitable substrate for said enzyme, wherein said enzyme is Alkaline Phosphatase (AP) or Horse Radish Peroxidase (HRP). 
     
     
         14 . A kit comprising
 (a) at least one aptamer bound to a matrix; and   (b) a polymer associated with a member of an affinity couple; wherein said polymer further comprising reactive groups.   
     
     
         15 . A kit according to  claim 14  wherein said polymer is a nucleic acid molecule. 
     
     
         16 . A kit according to  claim 14  wherein said reactive groups are reactive with primary NH 2  or COOH group. 
     
     
         17 . A kit according to  claim 14  wherein said reactive group is a succinimidyl ester group or Tosyl. 
     
     
         18 . A kit according to  claim 14 , further comprising at least one detection enzyme and optionally a substrate for said detection enzyme. 
     
     
         19 . A method for the diagnosis of a pathological condition in a subject comprising using a detection method in accordance with  claim 1 , wherein said target molecule is a target molecule associated with the pathological condition and wherein the amount of said detectable moiety is indicative of the presence of a pathological condition in the subject, and wherein said pathological condition is cancer, an autoimmune disease, or a viral, bacterial or fungal infection. 
     
     
         20 . A method for monitoring the efficiency of a therapeutic regimen in a subject suffering from a pathological condition comprising using a detection method in accordance with  claim 1 , wherein said target molecule is an antigen associated with the pathological condition and wherein the amount of said detectable moiety is indicative of the level of the pathological condition and thereby of the efficiency of the therapeutic regimen in the subject, and wherein said pathological condition is cancer, an autoimmune disease, or a viral, bacterial or fungal infection.