In-depth investigation on DNA-AgNCs designs for adenosine detection

Silver nanocluster (AgNCs) as like other metal nanoclusters has size of approaching Fermi wavelength of electron (~ 2 nm). This nanomaterial no longer possesses surface plasmon resonance (SPR). Indeed, its energy structure is... [ view full abstract ]

Silver nanocluster (AgNCs) as like other metal nanoclusters has size of approaching Fermi wavelength of electron (~ 2 nm). This nanomaterial no longer possesses surface plasmon resonance (SPR). Indeed, its energy structure is in a discrete level that similar to those of molecules, enable it to absorb intense light and emit strong fluorescence colour upon excited with UV light. Among stabilising ligands, DNA template has particularly gained more attention. Apart from its versatility, it may due to the feasibility to integrate DNA aptamer into the template. This aptamer functions exactly like antibody and binds specific to a target analyte. Hitherto, there is no detailed study about the impact of sequence template arrangement (i.e. AgNCs nucleation sequence and target recognizing sequence) on the sensing performance of AgNCs. In this work, we are investigating the effect of different combination between AgNCs nucleation sequence (NC) and adenosine aptamer (Apt A) onto adenosine detection. Three different designs have been formulated in order to systematically position AgNCs nucleation sequences and adenosine aptamer in the same template, namely Apt A 5, Apt A 3 and Apt A M with the last letter implies the position of AgNCs nucleation sequence at 5’-end, 3’-end and in the middle. Among these designs, only Apt A 5 design gives selective result against adenosine, with a 0.5-fold enhancement in the emission intensity observed. The linear range of detection is wide and across four order of magnitude, 1 – 2500 μM. We deduced that the fluorescent increment is correlated to the guanine rich bases in the aptamer sequence.