1 research outputs found
Ultrasensitive Colorimetric Detection of 17β-Estradiol: The Effect of Shortening DNA Aptamer Sequences
We report a strategy enabling ultrasensitive
colorimetric detection
of 17β-estradiol (E2) in water and urine samples using DNA aptamer-coated
gold nanoparticles (AuNPs). Starting from an established sensor format
where aggregation is triggered when target-bound aptamers dissociate
from AuNP surfaces, we demonstrated that step-change improvements
are easily accessible through deletion of excess flanking nucleotides
from aptamer sequences. After evaluating the lowest energy two-dimensional
configuration of the previously isolated E2 binding 75-mer aptamer
(<i>K</i><sub>D</sub> ∼25 nM), new 35-mer and 22-mer
aptamers were generated with <i>K</i><sub>D</sub>’s
of 14 and 11 nM by simply removing flanking nucleotides on either
side of the inner core. The shorter aptamers were found to improve
discrimination against other steroidal molecules and to improve colorimetric
sensitivity for E2 detection by 25-fold compared with the 75-mer to
200 pM. In comparing the response of all sequences, we find that the
excess flanking nucleotides suppress signal transduction by causing
target-bound aptamers to remain adhered to AuNPs, which we confirm
via surface sensitive electrochemical measurements. However, comparison
between the 22-mer and 35-mer systems show that retaining a small
number of excess bases is optimal. The performance advances we achieved
by specifically considering the signal transduction mechanism ultimately
resulted in facile detection of E2 in urine, as well as enabling environmental
detection of E2 at levels approaching biological relevance