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Disposable sensors are inexpensive, user-friendly sensing tools designed for rapid single-point measurements of a target. Disposable sensors have become more and more essential as diagnostic tools due to the growing demand for quick, easy-to-access, and reliable information related to the target. Dopamine (DA), a prevalent catecholamine neurotransmitter in the human brain, is associated with central nervous system activities and directly promotes neuronal communication. For the sensitive and selective estimation of DA, an enzyme-free amperometric sensor based on polyaniline-doped multi-walled carbon nanotubes (PANI-MWCNTs) drop-coated disposable screen-printed carbon electrodes (SPCEs) was fabricated. This PANI-MWCNTs-2/SPCE sensor boasts exceptional accuracy and sensitivity when working directly with ex vivo mouse brain homogenates. The sensor exhibited a detection limit of 0.05 μM (S/N = 3), and a wide linear range from 1.0 to 200 μM. The sensor’s high selectivity to DA amidst other endogenous interferents was recognized. Since the constructed sensor is enzyme-free yet biocompatible, it exhibited high stability in DA detection using ex vivo mouse brain homogenates extracted from both Parkinson’s disease and control mice models. This research thus presents new insights into understanding DA release dynamics at the tissue level in both of these models.

Maleimides serve as crucial components in various synthetic processes and are of significant interest to researchers in bioorganic chemistry and biotechnology. Although thermal reactions involving maleimides have been studied extensively, light-mediated reactions with maleimides remain relatively underutilized. This review focuses on understanding the behavior of maleimides in their excited state, particularly their role as synthetic scaffolds for excited-state reactions. Specific emphasis is placed on the diverse photoreactions involving maleimides and photophysical evaluation from our research group. [ABSTRACT FROM AUTHOR]

Melatonin (MT), a pineal gland hormone, regulates the sleep/wake cycle and is a potential biomarker for neurodegenerative disorders, depression, hypertension, and several cancers, including prostate cancer and hepatocarcinoma. The amperometric detection of MT was achieved using a sensor customized with ruthenium-incorporated carbon spheres (Ru–CS), possessing C- and O-rich catalytically active Ru surfaces. The non-covalent interactions and ion–molecule adducts between Ru and CS favor the formation of heterojunctions at the sensor–analyte interface, thus accelerating the reactions towards MT. The Ru–CS/Screen-printed carbon electrode (SPCE) sensor demonstrated the outstanding electrocatalytic oxidation of MT owing to its high surface area and heterogeneous rate constants and afforded a lower detection limit (0.27 μM), high sensitivity (0.85 μA μM −1 cm−2), and excellent selectivity for MT with the co-existence of crucial neurotransmitters, including norepinephrine, epinephrine, dopamine, and serotonin. High concentrations of active biomolecules, such as ascorbic acid and tyrosine, did not interfere with MT detection. The practical feasibility of the sensor for MT detection in pharmaceutical samples was demonstrated, comparable to the data provided on the product labels. The developed amperometric sensor is highly suitable for the quality control of medicines because of its low cost, simplicity, small sample size, speed of analysis, and potential for automation.

A novel electrochemical sensor based on Cu-loaded carbon nanospheres (Cu–CNSs) was designed and fabricated. Initially, the CNSs were synthesized using a natural or inexpensive carbon source (dark brown sugar), and Cu was loaded to enhance the electrocatalytic properties of the material. Subsequently, the synthesized Cu–CNSs were modified onto a screen-printed carbon electrode (SPCE), termed Cu–CNS/SPCE, to simultaneously detect the biomarkers dopamine (DA) and melatonin (MT) through differential pulse voltammetry. The surface characterization of the Cu–CNSs confirmed the formation of carbon spheres and Cu nanoparticles covering the spheres. Electrochemical studies showed that the Cu–CNS/SPCE had a high selectivity and sensitivity toward DA and MT, with a significant peak separation of 0.502 V. The two linear ranges of DA were 0.125–20 μM and 20–100 μM and the linear range of MT was 1.0–100 μM, with corresponding detection limits of 0.34 μM and 0.33 μM (S/N = 3), respectively. The quantification limits for DA and MT were 2.19 and 1.09 μM (S/N = 10), respectively. The sensor performance is attributed to the high conductivity and large, electrochemically active surface area of the Cu–CNS. In human serum samples, the Cu–CNS/SPCE exhibited good selectivity and satisfactory reproducibility for the simultaneous determination of DA and MT.

The irradiation of β‐enaminones, generated in situ from cyclic 1,3‐diketones and activated alkenes leads to polyheterocyclic skeletons. The photoproduct chemoselectivity depends on the type of cyclic 1,3‐diketones employed viz., 2‐acetylcyclopentanone and 2‐acetylcyclohexanone. The observed chemoselectivity was rationalized based on the Dieckmann‐Kon rule. [ABSTRACT FROM AUTHOR]

Bacterial infections in marine fishes are linked to mass mortality issues; hence, rapid detection of an infection can contribute to achieving a faster diagnosis using point-of-care testing. There has been substantial interest in identifying diagnostic biomarkers that can be detected in major organs to predict bacterial infections. Aspartate was identified as an important biomarker for bacterial infection diagnosis in olive flounder (Paralichthys olivaceus) fish. To determine aspartate levels, an amperometric biosensor was designed based on bi-enzymes, namely, glutamate oxidase (GluOx) and aspartate transaminase (AST), which were physisorbed on copolymer reduced graphene oxide (P-rGO), referred to as enzyme nanosheets (GluOx-ASTENs). The GluOx-ASTENs were drop casted onto a Prussian blue electrodeposited screen-printed carbon electrode (PB/SPCE). The proposed biosensor was optimized by operating variables including the enzyme loading amount, coreactant (α-ketoglutarate) concentration, and pH. Under optimal conditions, the biosensor displayed the maximum current responses within 10 s at the low applied potential of −0.10 V vs. the internal Ag/AgCl reference. The biosensor exhibited a linear response from 1.0 to 2.0 mM of aspartate concentrations with a sensitivity of 0.8 µA mM−1 cm−2 and a lower detection limit of approximately 500 µM. Moreover, the biosensor possessed high reproducibility, good selectivity, and efficient storage stability.

Aryl‐maleimides undergo a novel [2+4]‐photodimerization instead of the expected [2+2]‐photodimerization under both direct irradiation with visible light and under sensitized energy transfer conditions. This new excited state reactivity in aryl‐maleimides is deciphered through photochemical, photophysical, and spectroscopic studies. The stereochemistry of the photodimer depends on the type of non‐bonding interactions prevalent during photodimerization which is in turn dictated by the substituents on the maleimide ring. More importantly, the stereochemistry of the photodimer formed is complementary to the product observed under thermal conditions. [ABSTRACT FROM AUTHOR]

The study evaluates compatibility of stabilizers with dye doped liquid crystal (LC) scaffolds that are used in electronically dimmable materials. The photodegradation of the materials was investigated and suitable stabilizers were evaluated to slow the degradation process. Various types of benzotriazole‐based stabilizers were evaluated for stabilizing the liquid crystals. Based on spin trapping experiments, radicals generated upon UV exposure is likely responsible for the degradation of the system. The radical generation is competitively inhibited by the addition of stabilizers. [ABSTRACT FROM AUTHOR]

This account highlights the role of restricted bond rotations in influencing the excited-state reactivity of organic molecules. It highlights the photochemical reactivity of various organic molecules and the design strategies that could be exploited by chemists to utilize restricted bond rotations to uncover new excited-state reactivity and to achieve selectivity. 1 Introduction. 2 NEER-Principle and Restricted Bond Rotations in the Excited State 3 [2+2]-Photocycloaddition of Enamides 4 [3+2]-Photocycloaddition vs. Paternò–Büchi Reaction of Enamides 5 Divergent Photoreactivity of Enones Dictated by Restricted Bond Rotations: Norrish–Yang reactions vs. 6π-Photocyclization 6 Divergent Photoreactivity of Imides with Alkenes: [2+2]-Photocycloaddition vs. Photoene Reaction 7 Summary and Outlook [ABSTRACT FROM AUTHOR]

Photoreaction of enamides tethered to a phenyl ketone leads to either [3+2]‐photocycloaddition or Paternò–Büchi reaction. This divergence in chemical reactivity originating from the same excited state was dependent on the reaction temperature. At low temperatures the Paternò–Büchi reaction was preferred, whereas at higher temperatures there was preference toward formation of [3+2]‐photoproduct. [ABSTRACT FROM AUTHOR]

Intermolecular [2+2]‐photocycloaddition of atropisomeric phenyl maleimide has been evaluated with substituted alkenes with complete control over regiochemistry. We were also successful in carrying out atropselective reactions with the removal of axial chirality leading to enantio‐enriched photoproducts. Based on detailed photophysical studies, a mechanistic rationale is proposed for the observed selectivity. [ABSTRACT FROM AUTHOR]