Nanoparticle assisted nuclear relaxation-based oligonucleotide detection

Detection of Sortase A and Identification of Its Inhibitors by Paramagnetic Nanoparticle-Assisted Nuclear Relaxation

Sortase A is a virulence factor responsible for the attachment of surface proteins to Staphylococcus aureus and other Gram-positive bacteria. Inhibitors of this enzyme are potential anti-infective agents. Herein, a new highly selective magnetic relaxation-based method for screening potential sortase A inhibitors is described. A 13-amino acid-long peptide substrate of sortase A is conjugated to SiO₂-EDTA-Gd NPs. In the presence of sortase A, the LPXTG motif on the peptide strand is cleaved resulting in a shortened peptide as well as a reduced water T₂ value whose magnitude is dependent on the concentration of sortase A. The detection limit is determined to be 76 pM. In contrast, the presence of sortase A inhibitors causes the T₂ to remain at a higher value. The proposed method is used to characterize inhibition of sortase A by curcumin and 4-(hydroxymercuri)benzoic acid with an IC₅₀ value of 12.9 ± 1.6 μM and 130 ± 1.76 μM, respectively. Furthermore, this method was successfully applied to detect sortase A activity in bacterial suspensions. The feasibility to screen different inhibitors in Escherichia coli and S. aureus suspensions was demonstrated. This method is fast and potentially useful to rapidly screen possible inhibitors of sortase A in bacterial suspensions, thereby aiding in the development of antibacterial agents targeting Gram-positive bacteria.

A magnetic relaxation switch sensor for determination of 17β-estradiol in milk and eggs based on aptamer-functionalized Fe3 O4 @Au nanoparticles

BACKGROUND

A simple and rapid detection method for 17β-estradiol (E₂ ) in complex food matrix is greatly desirable. A magnetic relaxation switch (MRS) sensor for detecting E₂ based on the aptamer-functionalized gold-coated iron oxide (Fe₃ O₄ @Au) nanocomposite was designed in this study. Fe₃ O₄ @Au nanoparticles (NPs) played as a 'switch' between dispersed and aggregated states, while aptamer served as the recognition unit.

RESULTS

According to the sensing effect of monocomponent relaxation time (T_2W ) for E₂ , the volume ratio of aptamers to Fe₃ O₄ @Au, the sodium chloride (NaCl) concentration, the concentration of Fe₃ O₄ @Au@Apt, and reaction time were optimized to be 4:1, 0.03 mol L^-1 , 4 μmol L^-1 and 15 min, respectively. For the analysis of food sample, the E₂ was quantified over a concentration range of 1 to 100 nmol L^-1 with a detection limit of 7.6 nmol L^-1 for milk samples, while a linearity range of 20 to 100 nmol L^-1 and a detection limit of 8.57 nmol L^-1 for egg samples.

CONCLUSION

These results exhibited that the MRS sensor could be a promising platform for the rapid detecting of E₂ in food sample. © 2021 Society of Chemical Industry.