Novel Aptasensor Platform Based on Ratiometric Surface-Enhanced Raman Spectroscopy

A novel aptasensor platform has been developed for quantitative detection of adenosine triphosphate (ATP) based on a ratiometric surface-enhanced Raman scattering (SERS) strategy. The thiolated 3′-Rox-labeled complementary DNA (cDNA) is first immobilized on the gold nanoparticle (AuNP) surface and then hybridizes with the 3′-Cy5-labeled ATP-binding aptamer probe (Cy5-aptamer) to form a rigid double-stranded DNA (dsDNA), in which the Cy5 and Rox Raman labels are used to produce the ratiometric Raman signals. In the presence of ATP, the Cy5-aptamer is triggered the switching of aptamer to form the aptamer–ATP complex, leading to the dissociation of dsDNA, and the cDNA is then formed a hairpin structure. As a result, the Rox labels are close to the AuNP surface while the Cy5 labels are away from. Therefore, the intensity of SERS signal from Rox labels increases while that from Cy5 labels decreases. The results show that the ratio between the Raman intensities of Rox labels and Cy5 labels is well linear with the ATP concentrations in the range from 0.1 to 100 nM, and the limit of detection reaches 20 pM, which is much lower than that of other methods for ATP detection and is also lower than that of SERS aptasensor for ATP detection. The proposed strategy provides a new reliable platform for the construction of SERS biosensing methods and has great potential to be a general method for other aptamer systems

Label-Free Photonic Crystal-Based β‑Lactamase Biosensor for β‑Lactam Antibiotic and β‑Lactamase Inhibitor

A simple, label-free, and visual photonic crystal-based β-lactamase biosensor was developed for β-lactam antibiotic and β-lactamase inhibitor in which the penicillinase (a β-lactamase) was immobilized on the pH-sensitive colloidal crystal hydrogel (CCH) film to form penicillinase colloidal crystal hydrogel (PCCH) biosensing film. The hydrolysis of penicillin G (a β-lactam antibiotic) can be catalyzed by penicillinase to produce penicilloic acid, leading to a pH decrease in the microenvironment of PCCH film, which causes the shrink of pH-sensitive CCH film and triggers a blue-shift of the diffraction wavelength. Upon the addition of β-lactamase inhibitor, the hydrolysis reaction is suppressed and no clear blue-shift is observed. The concentrations of β-lactam antibiotic and β-lactamase inhibitor can be sensitively evaluated by measuring the diffraction shifts. The minimum detectable concentrations for penicillin G and clavulanate potassium (a β-lactamase inhibitor) can reach 1 and 0.1 μM, respectively. Furthermore, the proposed method is highly reversible and selective, and it allows determination of penicillin G in fish pond water samples