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Recent advances in DNA assembly and affinity binding have enabled exciting developments of nanosensors and ultrasensitive assays for specific proteins. These sensors and assays share three main attractive features: 1) the detection of proteins can be accomplished by the detection of amplifiable DNA, thereby dramatically enhancing the sensitivity; 2) assembly of DNA is triggered by affinity binding of two or more probes to a single target molecule, thereby resulting in increased specificity; and 3) the assay is conducted in solution with no need for separation, thus making the assay attractive for potential point-of-care applications. We illustrate here the principle of assembling DNA through affinity binding, and we highlight novel applications to the detection of proteins.

Therapeutic uses of DNA functionalized gold nanoparticles (DNA-AuNPs) have shown great potential and exciting opportunities for disease diagnostics and treatment. Maintaining stable conjugation between DNA oligonucleotides and gold nanoparticles under thermally stressed conditions is one of the critical aspects for any of the practical applications. We systematically studied the thermal stability of DNA-AuNPs as affected by organosulfur anchor groups and packing densities. Using a fluorescence assay to determine the kinetics of releasing DNA molecules from DNA-AuNPs, we observed an opposite trend between the temperature-induced and chemical-induced release of DNA from DNA-AuNPs when comparing the DNA-AuNPs that were constructed with different anchor groups. Specifically, the bidentate Au–S bond formed with cyclic disulfide was thermally less stable than those formed with thiol or acyclic disulfide. However, the same bidentate Au–S bond was chemically more stable under the treatment of competing thiols (mercaptohexanol or dithiothreitol). DNA packing density on AuNPs influenced the thermal stability of DNA-AuNPs at 37 °C, but this effect was minimum as temperature increased to 85 °C. With the improved understanding from these results, we were able to design a strategy to enhance the stability of DNA-AuNPs by conjugating double-stranded DNA to AuNPs through multiple thiol anchors.

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Jüngste Fortschritte auf dem Gebiet der DNA‐Assemblierung und der Affinitätsbindung haben zu aufregenden neuen Entwicklungen bei Nanosensoren und ultraempfindlichen Nachweismethoden für spezifische Proteine geführt.1–6 Diese Sensoren und Nachweissysteme haben drei attraktive Eigenschaften gemeinsam:1, 4, 7 1) Der Proteinnachweis gelingt mittelbar durch die Detektion amplifizierter DNA, wodurch die Empfindlichkeit drastisch erhöht wird. 2) Die Zusammenlagerung der DNA wird durch Affinitätsbindung von zwei oder mehr “Sonden” zu einem einzelnen Analytmolekül ausgelöst, was eine erhöhte Spezifität bedingt. 3) Der Nachweis erfolgt in Lösung ohne die Notwendigkeit einer vorherigen Abtrennung, was die Methodik für patientennahe Anwendungen attraktiv erscheinen lässt. Wir legen in diesem Kurzaufsatz das Prinzip dar, nach dem die Zusammenlagerung von DNA‐Molekülen mittels Affinitätsbindung erfolgt. Dabei stellen wir neuartige Anwendungen für den Nachweis von Proteinen beispielhaft heraus.