As a steroid hormone, cortisol has a close relationship with the stress response, and therefore, can be used as a biomarker for early detection of stress. An electrochemical immunosensor is one of the most widely used methods to detect cortisol, with antibodies as its bioreceptor. Apart from conventional laboratory-based methods, the trend for cortisol detection has seemed to be exploiting antibodies and aptamers. Both can provide satisfactory performance with high selectivity and sensitivity, but they still face issues with their short shelf life. Molecularly imprinted polymers (MIPs) have been widely used to detect macro- and micro-molecules by forming artificial antibodies as bioreceptors. MIPs are an alternative to natural antibodies, which despite demonstrating high selectivity and a low degree of cross-reactivity, often also show a high sensitivity to the environment, leading to their denaturation. MIPs can be prepared with convenient and relatively affordable fabrication processes. They also have high durability in ambient conditions, a long shelf life, and the ability to detect cortisol molecules at a concentration as low as 2 ag/mL. By collecting data from the past five years, this review summarizes the antibody and aptamer-based amperometric sensors as well as the latest developments exploiting MIPs rather than antibodies. Lastly, factors that can improve MIPs performance and are expected to be developed in the future are also explained.

Various implant treatments, including total disc replacements, have been tried to treat lumbar intervertebral disc (IVD) degeneration, which is claimed to be the main contributor of lower back pain. The treatments, however, come with peripheral issues. This study proposes a novel approach that complies with the anatomical features of IVD, the so-called monolithic total disc replacement (MTDR). As the name suggests, the MTDR is a one-part device that consists of lattice and rigid structures to mimic the nucleus pulposus and annulus fibrosus, respectively. The MTDR can be made of two types of thermoplastic polyurethane (TPU 87A and TPU 95A) and fabricated using a 3D printing approach: fused filament fabrication. The MTDR design involves two configurations—the full lattice (FLC) and anatomy-based (ABC) configurations. The MTDR is evaluated in terms of its physical, mechanical, and cytotoxicity properties. The physical characterization includes the geometrical evaluations, wettability measurements, degradability tests, and swelling tests. The mechanical characterization comprises compressive tests of the materials, an analytical approach using the Voigt model of composite, and a finite element analysis. The cytotoxicity assays include the direct assay using hemocytometry and the indirect assay using a tetrazolium-based colorimetric (MTS) assay. The geometrical evaluation shows that the fabrication results are tolerable, and the two materials have good wettability and low degradation rates. The mechanical characterization shows that the ABC-MTDR has more similar mechanical properties to an IVD than the FLC-MTDR. The cytotoxicity assays prove that the materials are non-cytotoxic, allowing cells to grow on the surfaces of the materials.

Dopamine (3,4‐dihydroxyphenethylamine) (DA) plays an important role in influencing emotions, pleasure sensations, concentration, pain, and coordination of body movements. However, abnormal levels of DA in the brain can lead to Parkinson’s, Alzheimer’s, or schizophrenia diseases. A biosensor is defined as an analytical tool that combines certain biological recognition components with a physical transducer. A comprehensive study was conducted to enhance the performance of DA detection by incorporating reduced graphene oxide (rGO), polypyrrole (PPy), and nickel oxide (NiO) into the glassy carbon electrode (GCE). DA levels were measured using cyclic voltammetry (CV) with a three‐electrode configuration. Material characterization was evaluated by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The results obtained indicate that PPy/rGO/NiO/GCE has a detection limit of 0.195 mM and a sensitivity of 25.887 A mM⁻¹ cm⁻² for a linear range of 0.01–1 mM.

Dopamine (DA) is a hormone and a neurotransmitter that plays many important roles within the brain and body. It is an organic compound in the catecholamines and phenethylamines groups. A considerable effort has been made since its discovery, and numerous techniques for DA detection have been developed. Graphene and its derivatives have great potential for the development of sensors and biosensors. Since it has excellent characteristics, such as good conductivity and a large surface area, a graphene-based biosensor is expected to have high sensitivity, selectivity, and long-term stability characteristics. Graphene oxide (GO) was synthesized using a chemical method through graphite oxidation. Graphene oxide/poly (3,4-ethylene-dioxythiophene):poly (4-styrenesulfonate) (GO/PEDOT:PSS) composite films were prepared using an electropolymerization method on the surface of the working electrode. The properties of this composite electrode were characterized by cyclic voltammetry (CV) and scanning electron microscopy (SEM). The performance of the composite film was evaluated using three-electrode systems that consisted of a glassy carbon electrode (GCE) modifying a composite film electrode as a working electrode, a platinum electrode as an auxiliary electrode, and Ag/AgCl as a reference electrode. The variation of the composite electrode was applied and evaluated to DA electrochemical sensing. The GO/PEDOT:PSS-modified electrode also exhibits high performance with a low detection limit of 1 ?M. The results obtained have shown that GO/PEDOT:PSS/GCE composites are promising candidates for modifying electrode material used in electrochemical sensing.