Biotin-Labeled Electropolymerized Network of Gold Nanoparticles for Amperometric Immunodetection of Human Fibrinogen

Binary Ni-Fe layered double hydroxide on flexible nickel foam for the wide-range voltammetric detection of fibrinogen in simulated body fluid

Fibrinogen, a circulating glycoprotein in the blood, is a potential biomarker of various health conditions. This work reports a flexible electrochemical sensor based on Ni-Fe layered double hydroxide (Ni-Fe LDH) coated on Nickel foam (Ni-Fe LDH/NF) to detect fibrinogen in simulated human body fluid (or blood plasma). The nanoflakes like morphology and hexagonal crystal structure of LDH, synthesized via urea hydrolysis assisted precipitation technique, are revealed by scanning electron microscopy (SEM) and powder x-ray diffraction (PXRD) techniques, respectively. The fabricated sensor exhibits linearity in a wide dynamic range covering the physiological concentration, from 1 ng ml-1to 10 mg ml-1, with a sensitivity of 0.0914 mA (ng/ml)-1(cm)-2. This LDH-based sensor is found to have a limit of detection (LOD) of 0.097 ng ml-1and a limit of quantification (LOQ) of 0.294 ng ml-1(S/N = 3.3). The higher selectivity of the sensor towards fibrinogen protein is verified in the presence of various interfering analytes such as dopamine, epinephrine, serotonin, glucose, potassium, chloride, and magnesium ions. The sensor is successful in the trace-level detection of fibrinogen in simulated body fluid with excellent recovery percentages ranging from 99.5% to 102.5%, proving the synergetic combination of 2D Ni-Fe layered double hydroxide and 3D nickel foam as a promising platform for electrochemical sensing that has immense potential in clinical applications.

Amperometric aptasensor for carcinoembryonic antigen based on the use of bifunctionalized Janus nanoparticles as biorecognition-signaling element

We report herein the design of a novel biosensing strategy for the detection of carcinoembryonic antigen (CEA), based on the use of Janus-type nanoparticles having Au and silica opposite faces as integrated electrochemical biorecognition-signaling system. The Janus nanoparticles were properly functionalized with horseradish peroxidase on the silica surface to act as signaling element, and a biotin thiol-modified anti-CEA DNA hairpin aptamer the Au face to assemble the biorecognition element. The sensing approach relies on the first specific recognition of CEA by the bifunctionalized Janus nanoparticles, causing unfolding of the DNA hairpin structure and unmasking the biotin residues at the aptamer chain. This CEA-Janus nanoparticle complex was then captured by avidin-modified Fe₃O₄@SiO₂ NanoCaptors^®, allowing further magnetic deposition on carbon screen printed electrodes for the amperometric detection of the cancer biomarker. The Janus nanoparticles-based aptasensor was able to detect CEA in the range from 1 to 5000 ng mL^-1 (5.5 pM-28 nM) with a detection limit of 210 pg mL^-1 (1.2 pM). The aptasensor also showed high reproducibility and storage stability, and was successfully validated in human serum.