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A label-free electrogenerated chemiluminescence (ECL) aptasensing method for highly sensitive determination of dopamine (DA) was developed based on target-induced DNA conformational change. After anti-DA specific aptamer, as molecular recognition element, was hybridized with a capture ss-DNA (complementary with the aptamer), the formed double-strand DNA (ds-DNA) was self-assembled onto the surface of a gold electrode, and then Ru(phen)32+, as ECL reagent, was intercalated into ds-DNA to form an ECL biosensing platform. In the presence of DA, DA bound with its aptamer and target-induced DNA conformational change occurred, resulting in the dissociation of ds-DNA, the release of intercalated Ru(phen)32+from the electrode surface, and the decrease of ECL intensity. For comparison, an ECL aptamer-based biosensing method using an ECL reagent-labeled aptamer was also developed for DA assay based on target-induced DNA conformational change. Because of the increase in the amount of ECL reagent into ds-DNA over that of the single-site ECL reagent-labeled aptamer, an obvious increase of ECL intensity was found at the ds-DNA modified electrode over the aptamer modified electrode. DA can be sensitively detected with a lower detection limit of 0.05 nM in the range from 0.1 to 100 nM. With the recognition of the aptamer for DA, DA can be selectively and sensitively detected in artificial cerebrospinal fluid and serum samples without interference from common small molecules. This work demonstrates that the combination of the direct transduction of specific recognition of DA and its aptamer into an ECL signal with Ru(phen)32+intercalated ds-DNA amplification provides a promising strategy for the development of a simple, sensitive, and selective method for DA assay, which is of great importance in neurochemical assays and clinical diagnosis.

A gold nanoflowers and overoxidized polypyrrole modified carbon fiber microelectrode (OPPy/Au NFs/CFME) was fabricated using electroless deposition and electrochemical method for highly selective and sensitive detection of 5-HT.

Intracellular pH undertakes critical functions in various biological and pathological processes. It is important to monitor intracellular pH fluctuations for understanding physiological and pathological processes. Here, one aldehyde-bearing cyclometalated iridium(III) complex ([(4-pba)2Ir(dcphen)]PF6, 4-pba = 4-(2-pyridyl) benzaldehyde, dcphen = 4,7-dichloro-1,10-phenanthroline, probe 1) was synthesized and used to track intracellular pH fluctuations. Probe 1 displayed pH-dependent luminescence property in pH range of 1.81–6.81 with an evaluated pKavalue of 4.30 in BR buffer-DMSO (v:v = 99:1). An intramolecular hydrogen bonds assisted pH-responsive mechanism was proposed for the pH-responsive behavior of probe 1. Probe 1 was successfully applied for imaging and tracking pH fluctuations in HeLa cells under external stimulation with fast response time, good photostability as well as low cytotoxicity and high cell permeability. This work demonstrates that aldehyde-bearing cyclometalated iridium(III) complex can be used as alternative pH-responsive probe for real-time tracking intracellular pH fluctuations, which provides a strategy for the design of pH-responsive probe in versatile applications.

Developing water-stable and adaptive supramolecular materials is of great importance in various research fields. Here, we demonstrate a new kind of water-stable, adaptive, and electroactive supramolecular ionic materials (SIM) that is formed from the aqueous solutions of imidazolium-based dication and dianionic dye (i.e., 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), ABTS) through ionic self-assembly. The formed SIM not only shows good thermostability and unique optical and electrochemical properties that are raised from precursors of the SIM, but also exhibits good water-stability, salt-stability, and adaptive encapsulation properties toward some heterocyclic cationic dye molecules. UV–vis and FT-IR results demonstrate that this encapsulation property is essentially based on the electrostatic interactions between the guest dye molecules and ABTS in the SIM. The application of the SIM prepared here is illustrated by the development of a new electrochemical sensor for NADH sensing at a low potential. This study not only opens a new avenue to the preparation of the supramolecular materials, but also provides a versatile platform for electrochemical (bio)sensing.

We demonstrate the preparation of a dual-site carbon nanozyme, boron-doped and ketonic carbonyl (−C=O) group-enriched graphdiyne (B-GDY), with an enhanced peroxidase-like activity. Taking advantage of acidic oxidation treatment, GDY oxide (GDYO) with abundant surface oxygen-containing groups is obtained from pristine bulk GDY. Upon further thermal annealing of GDYO with H3BO3under an inert atmosphere, B is introduced into GDY, while the loading of −C=O groups is increased onto B-GDY. We discover that boron-doped and ketonic carbonyl group-enriched graphdiyne as a dual-site carbon nanozyme endows it with an enhanced peroxidase-like activity, which is nearly 4.2-fold higher than that of GDY without B atoms and 6.6-fold higher than that of GDYO without B atoms and with low loading of −C=O groups. The high peroxidase-like activity of B-GDY is ascribed to the dual active sites (−C=O group and B atom) within it, which facilitates the adsorption and decomposition of H2O2into hydroxyl radicals revealed by experimental and theoretical studies. Moreover, B-GDY is successfully employed to develop a colorimetric method for the detection of glucose with good sensitivity and selectivity. This work probes into the intrinsic peroxidase activity and structure–reactivity correlation, creating effective strategies for the preparation of GDY-based nanozymes.

We report a self-terminated electroless deposition method to prepare surfactant-free and monodispersed Pt nanoparticle (NP)-modified carbon fiber microelectrodes (Pt NP/CFEs) for electrochemical detection of hydrogen peroxide (H2O2) released from living cells. The surfactant-free and monodispersed Pt NPs with a uniform size of 65 nm are spontaneously deposited on a CFE surface by immersing an exposed carbon fiber (CF) of CFE in the PtCl42–solution, in which an exposed CF can be used as the reducing agent and stabilizer. A self-terminated electroless deposition method is demonstrated, in which the density and size of Pt NPs on a CFE surface do not increase when the reaction time increases from 20 to 60 min. The self-terminated electroless deposition process not only can effectively avoid any manual electrode modification and thus largely minimize person-to-person and electrode-to-electrode deviations but also can avoid the use of any extra reductant or surfactant in the fabrication process. Therefore, Pt NPs/CFEs, with good reproducibility and sensitivity, not only exhibit high electrocatalytic activity toward the oxidation of H2O2but also maintain the spatial resolution of CFEs. Moreover, Pt NPs/CFEs can detect H2O2with a wide linear range of 0.5–80 μM and a low detection limit of 0.17 μM and then can be successfully applied in the monitoring of H2O2released from RAW 264.7 cells. The self-terminated electroless deposition method can also be extended to selectively prepare other metal NP-modified CFEs, such as Au NPs/CFEs or Ag NPs/CFEs, by choosing the metal ions with higher reduction potential as precursors. This work provides a simple, straightforward, and general method for the preparation of small, surfactant-free, and monodispersed metal NP-modified CFEs with high sensitivity, reproducibility, and spatial resolution.