A quick plunge: By using lateral flow devices as a platform to separate aptamer‐assembled nanoparticle (NP) aggregates, highly sensitive and selective colorimetric sensors were constructed that mimic litmus paper tests. Detection of cocaine in serum was also realized.

Recent progress in an emerging area of designing aptamer and nanomaterial conjugates as molecular diagnostic and drug delivery agents in biomedical applications is summarized. Aptamers specific for a wide range of targets are first introduced and compared to antibodies. Methods of integrating these aptamers with a variety of nanomaterials, such as gold nanoparticles, quantum dots, carbon nanotubes, and superparamagnetic iron oxide nanoparticles, each with unique optical, magnetic, and electrochemical properties, are reviewed. Applications of these systems as fluorescent, colorimetric, magnetic resonance imaging, and electrochemical sensors in medical diagnostics are given, along with new applications as smart drug delivery agents.

Design of smart MRI contrast agent based on superparamagnetic iron oxide nanoparticles and aptamers has been described for the detection of human alpha-thrombin protein. The contrast agent is based on the assembly of the aptamer functionalized nanoparticles in the presence of thrombin. A detectable change in MRI signal is observed with 25 nM thrombin in human serum. Changes were neither observed with control analytes, streptavidin, or bovine serum albumin, nor with inactive aptamer functionalized nanoparticles.

Easy-to-use dipstick tests for lead have been developed by immobilizing nanoparticle–DNAzyme conjugates on lateral flow devices and their application for detecting lead in paints is demonstrated.

Smart agents. A contrast agent was designed by combining target specific nucleic‐acid aptamers against adenosine with superparamagnetic iron oxide nanoparticles. Target‐induced disassembly of clustered nanoparticles in the presence of adenosine led to an increase in T2, which was seen as an increase in the brightness of the magnetic resonance image (see figure).