Ultrasensitive detection of small biomolecules using aptamer-based molecular recognition and nanoparticle counting

Detection of small biomolecules is critical for understanding molecular mechanisms in biological systems and performing in vitro diagnosis in clinics. Current antibody based detection methods face large challenges in detecting small biomolecules at low concentrations. We report a new method for detecting small biomolecules based on molecular recognition and nanoparticle (NP) counting. Aptamer-functionalized NPs are attached to complementary sequence (CS)-conjugated microparticle (MP) carriers. In the presence of target small biomolecules at ultra low concentrations, NPs would be released from the MP carriers. Coupled with a resistive pulse sensor (RPS) using a micropore that counts the released NPs, this method can measure the concentrations of target biomolecules at low concentrations with high sensitivity and high throughput. Adenosine was used as a model to demonstrate the feasibility of this method. It is demonstrated that this method can detect a wide range of adenosine concentrations with a low detection limit of 0.168 nM, which is 10 times lower than that of the ELISA kit. With its simple structure, high sensitivity, and high reproducibility, this detection method holds great potential for the ultrasensitive detection of low abundance small biomolecules.