A dual-aptamer biosensor based on 3D nanostructured gold deposited multielectrode arrays (3D-GMEAs) was developed for the simultaneous detection of AβO and ATP in artificial cerebrospinal fluid.

Accurate determination of serotonin (ST) provides insight into neurological processes and enables applications in clinical diagnostics of brain diseases. Herein, we present an electrochemical aptasensor based on truncated DNA aptamers and a polyethylene glycol (PEG) molecule-functionalized sensing interface for highly sensitive and selective ST detection. The truncated aptamers have a small size and adopt a stable stem-loop configuration, which improves the accessibility of the aptamer for the analyte and enhances the sensitivity of the aptasensor. Upon target binding, these aptamers perform a conformational change, leading to a variation in the Faraday current of the redox tag, which was recorded by square wave voltammetry (SWV). Using PEG as blocking molecules minimizes nonspecific adsorption of other interfering molecules and thus endows an enhanced antifouling ability. The proposed electrochemical aptamer sensor showed a wide range of detection lasting from 0.1 nM to 1000 nM with a low limit of detection of 0.14 nM. Owing to the unique properties of aptamer receptors, the aptasensor also exhibits high selectivity and stability. Furthermore, with the reduced unspecific adsorption, assaying of ST in human serum and artificial cerebrospinal fluid (aCSF) showed excellent performance. The reported strategy of utilizing antifouling PEG describes a novel approach to building antifouling aptasensors and holds great potential for neurochemical investigations and clinical diagnosis.

In this work, a novel sandwich-type electrochemical immunosensor was developed for the quantitative detection of the carcinoembryonic antigen, an important tumor marker in clinical tests. The capture antibodies were immobilized on the surface of a gold disk electrode, while detection antibodies were attached to redox-tagged single-walled carbon nanohorns/thionine/AuNPs. Both types of antibody immobilization were carried out through Au-S bonds using the novel photochemical immobilization technique that ensures control over the orientation of the antibodies. The electroactive SWCNH/Thi/AuNPs nanocomposite worked as a signal tag to carry out both the detection of carcinoembryonic antigen and the amplification of the detection signal. The current response was monitored by differential pulse voltammetry. A clear dependence of the thionine redox peak was observed as a function of the carcinoembryonic antigen concentration. A linear detection range from 0.001–200 ng/mL and a low detection limit of 0.1385 pg/mL were obtained for this immunoassay. The results showed that carbon nanohorns represent a promising matrix for signal amplification in sandwich-type electrochemical immune assays working as a conductive and binding matrix with easy and versatile modification routes to antibody and redox tag immobilization, which possesses great potential for clinical diagnostics of CEA and other biomarkers.

Accurate and simultaneous determination of multiple neurotransmitters (NTs) is crucial for a thorough understanding of brain functions and for diagnosing neurological disorders. We have developed an electrochemical biosensor utilizing aptamer recognition for the highly sensitive and simultaneous detection of multiple neurotransmitters, including glutamate quantification for the first time in multiplex detection. Microelectrode arrays (MEAs) served as biosensing platforms to facilitate the recording of signals from multiple channels, rapid mass transfer rates, and high spatial resolution, fundamental for studying NTs release in nervous tissue. To enhance aptamer receptor loading, gold nanostructures were electrodeposited onto the microelectrodes, enhancing the active surface area and electrode morphology. A potential-pulse-assisted method was employed to achieve site-selective immobilization of three different aptamers on a single MEA chip within 30 min, enabling fast and reproducible sensor fabrication. This unique strategy ensured aptamer-specific immobilization, minimized cross-talk, and allowed for multiplex detection of serotonin, glutamate, and dopamine with high sensitivity and specificity. Additionally, using polyethylene glycol (PEG) as a blocking molecule, the aptamer-functionalized MEAs showed enhanced antifouling properties and maintained detection capabilities in complex environments. This multiplexed detection strategy enables a high-performance and robust biosensor platform with strong clinical relevance, offering substantial potential for in vivo monitoring of neurotransmitter release and the diagnosis of neurological disorders.