Abstract
In recent years, poly adenine (polyA) DNA functionalized gold nanoparticles (AuNPs) free of modifications was fabricated with high density of DNA attachment and high hybridization ability similar to those of its thiolated counterpart. This nanoconjugate utilized poly adenine as an anchoring block for binding with the AuNPs surface thereby facilitated the appended recognition block a better upright conformation for hybridization, demonstrating its great potential to be a tunable plasmonic biosensor. It’s one of the key points for any of the practical applications to maintaining stable conjugation between DNA oligonucleotides and gold nanoparticles under various experimental treatments. Thus, in this research, we designed a simple but sensitive fluorescence turn-on strategy to systematically investigate and quantified the dissociation of polyA DNA on gold nanoparticles in diverse experimental conditions. DNA desorbed spontaneously as a function of elevated temperature, ion strength, buffer pH, organic solvents and keeping time. What’s more, evaluating this conjugate stability as affected by the length of its polyA anchor was another crucial aspect in our study. With the improved understanding from these results, we were able to control some of our experimental conditions to maintain a good stability of this kind of polyA DNA−AuNPs nanoconjugates.
Highlights
The dissociation of DNA which derived from the Au− S bond cleavage would happen when the conjugates were exposed to other thiols, high temperatures and acidic buffer solutions[38,39]
All of the fluorescence should stem from DNA desorption. 13 nm diameter gold nanoparticles were selected for our research since these particles were readily synthesized and large enough to quench the fluorescence of bound fluorescent DNA completely
We evaluated the stabilities of these poly adenine (polyA) DNA− AuNPs probes by designing a simple but sensitive fluorescence turn-on assay (Fig. 1A) that have been used in the thiolated DNA− AuNPs38,45,46
Summary
The dissociation of DNA which derived from the Au− S bond cleavage would happen when the conjugates were exposed to other thiols, high temperatures and acidic buffer solutions[38,39]. PolyA DNA seemed to wrap around the AuNPs and failed to obtain an upright conformation[9,14]. This phenomenon may explain why few reports exploit this kind of conjugates for biosensing. Our team reported a new salt-aging strategy that using poly adenine (polyA) as an anchoring block to modified diblock polyA DNA onto the AuNPs47. The two approaches were created conjugates share similar good colloidal stability and facilitated the recognition block an upright conformation that favored DNA hybridization. We have demonstrated that polyA served as an effective anchoring block and the appended recognition block adopts an upright conformation that favored DNA hybridization. PolyA20 and polyA30 DNA− AuNPs conjugates showed preferable stability in most of the experiment conditions
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