Surface stress-induced membrane biosensor based on double-layer stable gold nanostructures for E. coli detection

Aptamer-functionalized polydiacetylene biosensor for the detection of three foodborne pathogens

Rapid, simple and sensitive screening of foodborne pathogens is of great significance to ensure food safety. In this study, an aptamer-functionalized polydiacetylene (Apta-PDA) biosensor was developed for the detection of E. coli O157:H7, S. typhimurium or V. parahaemolyticus. First, aptamers responding to the target bacteria were modified on the surface of magnetic beads by covalent binding to form MBs-oligonucleotide conjugates for bacterial enrichment. Then, an Apta-PDA biosensor was obtained by connecting the aptamers to the PDA nanovesicles using the carbodiimide method. Molecular recognition occurred in the presence of the target bacteria, whereby the aptamer folded into a sequence-defined unique structure, resulting in an MBs-Apta/bacteria/Apta-PDA sandwich structure. Due to the optical properties of PDA, the blue-red transition of the detection system could be observed by the naked eye and quantified by the colorimetric response percentage (CR%). Under optimized conditions, the detection limits of E. coli O157:H7, S. typhimurium and V. parahaemolyticus were 39, 60 and 60 CFU/ml, respectively, with a selectivity of 100% and a reaction time of 30 min. Compared with the gold standard method, the accuracy of the three target bacteria detection reached 98%, 97.5% and 97%, respectively, and the sensitivity and specificity were both greater than 90%. The entire detection process was rapid and easy to execute without any special equipment, making this technology particularly suitable for resource-poor laboratories or regions.

A mechanical biosensor based on membrane-mediated magneto-stress-electric coupled sensitization for human serum albumin detection

Recently, mechanical biosensors have attracted more attention on single molecule detection due to its high accuracy, low cost, and convenience. However, the sensitivity of the mechanical biosensors restricted their clinical application. Herein, a mechanical biosensor based on membrane-mediated magneto-stress-electric coupled sensitization (MSEC-MMB) was developed to enhance performance. Through introducing Fe3O4 nanoparticles (MNPs) to traditional stress-electric biosensors and applying a magnetic field, a magneto-stress-electric coupled biosensing system was constructed. The sensitivity of the MSEC-MMB was improved via enhancing the deformation of the mechanical membrane, which was demonstrated by detecting HSA. The optimal limit of detection (LOD) was 24 pg mL-1 under a magnetic field of 50 mT. The LOD was significantly 1 order of magnitude lower than that without the magnetic field. Besides, the MSEC-MMB showed a high specificity, selectivity, and stability. The clinical proteinuria samples were accurately detected, suggesting a good practicability of the MSEC-MMB. All these results proved the high sensitivity and practicality of the MSEC-MMB and provide a platform for early nephropathy diagnosis.

A mechanical HSA biosensor based on multi-field-coupling-mediated magnetic sensitization strategy

The conventional mechanical biosensor based on stress and electrical conversion can be an effective method to detect key human biomarkers for clinical diagnosis and early disease prevention. However, the applications of this type of biosensor are greatly limited due to their unsatisfactory sensitivity. In this work, a magnetic-sensitized (MS) mechanical biosensor based on multi-field coupling was developed for higher sensitivity, giving access to detect human serum albumin (HSA). Via introducing secondary magnetic antibodies labeled with magnetized Fe2O3 nanoparticles to the stress and electrical conversion element of the MS-biosensor, the multi-field coupling was realized based on stress, electricity, and magnetism. Under the action of the magnetic field, the magnetic force of the secondary magnetic antibody and the stress of antigen-antibody binding jointly drove and enhanced the deformation of the MS-biosensor, amplifying the electrical signal, and realizing magnetic sensitization. The HSA was detected by the MS-biosensor at a range of 0-80 μg/mL with a limit of detection (LOD) of 0.14 μg/mL, demonstrating the high performance of the MS-biosensor. Moreover, the MS-biosensor showed high selectivity, specificity, and stability, indicating that the magnetic sensitization strategy of the MS-biosensor was significant for the clinical application of mechanical biosensors.