An automated solid-phase extraction (SPE) device using a digital light processing 4DP technique combined with graphene-incorporated N-isopropylacrylamide resins has been developed. The device comprised flow manifolds, a monolithic packing, and a cantilever featuring a channel connected to a near-infrared (NIR)-actuated thermoresponsive actuator composed of a graphene-incorporated layer and a nonresponsive layer. Power-controlled NIR irradiation increased the temperature of the graphene-incorporated layer above its volume phase transition temperature, causing it to deswell and creating an imbalance between the two layers that induced stepwise bending of the cantilever. This manipulation enabled multiple streams to sequentially pass through the monolithic packing, thereby facilitating the automation of the SPE scheme. Coupling the optimized 4D-printed NIR-actuated stream selector-SPE device with inductively coupled plasma mass spectrometry enabled highly sensitive and reliable determination of Mn, Co, Ni, Cu, Zn, Cd, and Pb ions, with method detection limits ranging from 0.1 to 0.3 ng L− 1. The reliability and applicability of this analytical method were validated by determining the metal ions in four reference materials (CASS-6, SLRS-5, 1643f, and Seronorm™ Trace Elements Urine L-2), as well as in environmental water and human urine samples. Our results demonstrate the capability and versatility of 4DP technologies to advance the fabrication of smart analytical devices and automate conventional SPE schemes while maintaining competitive analytical performance.
Amyloid-beta 42 (Aβ42) is a key biomarker associated with Alzheimer’s disease (AD), and its plasma levels serve as a crucial indicator for early detection of AD. In this study, an electrochemical impedimetric biosensor capable of rapid, sensitive, and specific quantitative determination of Aβ42 protein was designed for the early diagnosis of Alzheimer’s disease. The composite two-dimensional nanomaterial reduced graphene oxide/protonated graphitic carbon nitride (p-CN/rGO) was used for signal amplification, with gold nanoparticles (AuNPs) providing molecular binding sites. An artificially designed peptide (sequence: CPPPEKEKEKKLVFF) enables specific recognition of Aβ42, and the fabrication and quantitative determination of Aβ42 were monitored by electrochemical impedance spectroscopy (EIS). The fabricated electrochemical biosensing platform exhibits a broad linear detection range (1 fg/mL to 1 ng/mL) and a low limit of detection (1.97 × 10− 2 fg/mL), enabling sensitive and precise detection of Aβ42 protein. Furthermore, the biosensor was investigated for excellent reproducibility, stability, selectivity, and regeneration, and demonstrates reliability in the practical analysis of Aβ42 in simulated human serum. Thus, this electrochemical biosensing platform offers a novel approach to blood-based detection of Aβ, providing an experimental foundation for early diagnosis and research into the pathological mechanisms of AD.
A surface engineering technique is described to improve the dispersibility of carbon nanofiber (CNF ) in water and to provide oxygen-rich anchor sites for ZnO nanorods (NRs) by adsorbing tannic acid (TA) on CNF surfaces through π–π interactions and hydrogen bonding, followed by sonochemically assembling the ZnO NRs onto the TA-CNF to form a TA-CNF/ZnO NRs composite. The addition of TA on CNF surfaces improved the homogeneity of ZnO NRs distribution within the composite and increased the relative surface area of the TA-CNF/ZnO NRs compared to pristine CNF from 15.16 m2 g–1 to 193.17 m2 g–1. Under optimized parameters, the TA-CNF/ZnO NRs electrode displayed superior electrocatalytic activity for CPZ detection, with a detection linear range from 0.01 to 483 µM, excellent sensitivity (3.03 µA µM–1 cm–2), and a lower limit of detection (0.005 µM). Also, the fabricated sensor showed satisfactory stability, accuracy, and anti-interference capability against CPZ detection. Recoveries of 99.64–99.97
A dual-mode (colorimetric/fluorometric) sensing system for monitoring chloramphenicol (CAP) residues has been developed. The detection system was constructed using Fe₃O₄ nanoparticles (Fe₃O₄ NPs) as magnetic separation carriers and Mn-doped carbon dots (Mn-CDs) as signal probes. Fe₃O₄ NPs were conjugated to the CAP aptamer (Apt) via amide linkages, and Mn-CDs were linked to the complementary DNA strand (cDNA).Subsequently, these two components were assembled through base complementarity. In the presence of CAP, the Mn-CDs-cDNA complex undergoes competitive dissociation due to the stronger specific binding between CAP and the aptamer compared with base pairing. Following magnetic separation, the released Mn-CDs-cDNA complex in the supernatant catalyzes the oxidation of o-phenylenediamine (OPD) to 2,3-diaminophenazine (DAP), generating a colorimetric signal with an absorption peak at 450 nm. Simultaneously, a ratiometric fluorescence signal is achieved through the inner filter effect (IFE). DAP formation enhances fluorescence at 550 nm while quenching the blue emission of Mn-CDs at 455 nm. This dual-mode strategy enables the sensitive detection of CAP via monitoring the absorbance intensity and the fluorescence ratio (F550 nm/F455 nm). Under optimized detection conditions, the linear range for the colorimetric mode was 0.002-2 µmol L-1 with a detection limit of 11.6 nmol L-1; the linear range for the fluorometric mode was 0.005-6 µmol L-1 with a detection limit of 4.02 nmol L-1. This method demonstrates reliable performance for the detection of CAP residues in food samples. The dual-mode sensing strategy offers enhanced sensitivity and provides a promising analytical approach for food safety monitoring.
A facile and sensitive potentiometric aptasensor based on Au nanoparticle and aptamer decorated infinite coordination polymer network (SH-Apt/AuNPs/ICPn) for the rapid detection of living bacteria cells is introduced. In the present system, AuNPs/ICPn composites served as the electron‑transducing layer for the sensing electrode, in which the unique network structure of ICPn could provide a large specific surface area for the deposition of conductive AuNPs. The aptamer layer immobilized via Au-S covalent bonding was used for target recognition, and the potentiometric response shift can be attributed to the change in the interfacial charge environment induced by the target-aptamer interaction. Taking Escherichia coli O157:H7 as a model bacterium, a good linear relationship between potentiometric response and logarithm of bacterium concentration was acquired with a low detection limit of 2.8 CFU·mL− 1. Moreover, the proposed aptasensor was applied to milk and fruit juice samples and yielded satisfactory results. We believe that such a potentiometric aptasensor is promising for food safety monitoring.
