Lanthanide-based luminescent sensors have been widely used for the detection of the anthrax biomarker dipicolinic acid (DPA). However, mainly based on DPA sensitization to the lanthanide core, most of them failed to realize robust detection of DPA in bacterial spores. We proposed a new strategy for reliable detection of DPA by perturbing a tandem energy transfer in heterobinuclear lanthanide coordination polymer nanoparticles simply constructed by two kinds of lanthanide ions, Tb and Eu, and guanosine 5'-monophosphate. This smart luminescent probe was demonstrated to exhibit highly sensitive and selective visual luminescence color change upon exposure to DPA, enabling accurate detection of DPA in complex biosystems such as bacterial spores. DPA release from bacterial spores on physiological germination was also successfully monitored in real time by confocal imaging. This probe is thus expected to be a powerful tool for efficient detection of bacterial spores in responding to anthrax threats.

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In this study, we demonstrate a facile and environmentally friendly method for the synthesis of glutathione (GSH)-capped water-soluble CdS quantum dots (QDs) with a high cytocompatibility and a tunable optical property based on alkaline post-treatment of Cd-GSH coordination polymers (CPs). Cd-GSH CPs are synthesized with the coordination reaction of Cd(2+) with GSH at different pH values, and the CdS QDs are then formed by adding NaOH to the aqueous dispersion of the Cd-GSH CPs to break the coordination interaction between Cd(2+) and GSH with the release of sulfur. The particle size and optical property of the as-formed CdS QDs are found to be easily tailored by simply adjusting the starting pH values of GSH solutions used for the formation of Cd-GSH CPs, in which the wavelengths of trap-state emission of the QDs red-shift with an increase in the sizes of the QDs that is caused by an increase in the starting pH values of GSH solutions. In addition, the use of GSH as the capping reagent eventually endows the as-formed CdS QDs with enhanced water solubility and good cytocompatibility, as demonstrated with HeLa cells. The method demonstrated here is advantageous in that the cadmium precursor and the sulfur source are nontoxic and easily available, and the size, optical properties, water solubility, and cytocompatibilty of the as-formed CdS QDs are simply achieved and experimentally regulated. This study offers a new and green synthetic route to water-soluble and cytocompatible CdS QDs with tunable optical properties.

Copper ions (Cu 2+ ) in the central nervous system play a crucial role in the physiological and pathological events, so simple, selective, and sensitive detection of cerebral Cu 2+ is of great importance. In this work, we report a facile yet effective fluorescent method for sensing of Cu 2+ in rat brain using one kind of lanthanide coordination polymer nanoparticle, adenosine monophosphate (AMP) and terbium ion (Tb 3+ ), i.e., AMP-Tb, as the sensing platform. Initially, a cofactor ligand, 5-sulfosalicylic acid (SSA), as the sensitizer, was introduced into the nonluminescent AMP-Tb suspension, resulting in switching on the luminescence of AMP-Tb by the removal of coordinating water molecules and concomitant energy transfer from SSA to Tb 3+ . The subsequent addition of Cu 2+ into the resulting SSA/AMP-Tb can strongly quench the fluorescence because the specific coordination interaction between SSA and Cu 2+ rendered energy transfer from SSA to Tb 3+ inefficient. The decrease ratio of the fluorescence intensities of SSA/AMP-Tb at 550 nm show a linear relationship for Cu 2+ within the concentration range from 1.5 to 24 μM with a detection limit of 300 nM. The method demonstrated here is highly selective and is free from the interference of metal ions, amino acids, and the biological species commonly existing in the brain such as dopamine, lactate, and glucose. Eventually, by combining the microdialysis technique, the present method has been successfully applied in the detection of cerebral Cu 2+ in rat brain with the basal dialysate level of 1.91 ± 0.40 μM (n = 3). This method is very promising to be used for investigating the physiological and pathological events that cerebral Cu 2+ participates in.

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Ever increasing needs for sustainable development in the environment, society and economy essentially require dramatic improvements of rapid and on-spot analytical methods for environmental monitoring, social safety guarantee, quality control, clinical diagnostics, and so forth.[1] Among the analytical methods demonstrated so far, electrochemical biosensors remain particularly attractive to meet such requirements because the specific recognition of biomolecules (e.g., enzymes, proteins, and aptamers) towards their targets can be integrated with the technical simplicity and high sensitivity of electrochemical methods. Such integration substantially endows the electrochemical biosensors with excellent properties including good sensitivity, easy adaptability for rapid and on-spot analysis, and relatively cheap instrumentation. [2] However, the pressing need for rapid and on-spot analysis in most cases necessitates great improvements of electrochemical biosensors both in simplifying their fabrication and in minimizing biosensor-to-biosensor deviation. This is because the involvement of multistep surface confinement of all biosensing elements, including biorecognition units (i.e., oxidases and dehydrogenases) and electronic transducers (i.e., cofactors, electron transfer mediators or electrocatalysts) onto conducting solid substrate inevitably renders a complicated and time-consuming process for biosensor fabrication, and more importantly, poor reproducibility with a large biosensor-to-biosensor variation.[3] These limitations unfortunately turn the application of this type of biosensor for rapid and on-spot analysis in a simple way to a challenge.Herein, we report a new strategy for simplifying biosensor fabrication, and thus shorten the analysis time as well as minimize the biosensor-to-biosensor deviation by integrating all the biosensing elements into a single infinite coordination polymer (ICP) nanoparticle. With such bioelectrochemically active ICP nanoparticles as the biosensing units, the biosensors can be simply fabricated by confining the nanoparticles onto the conducting substrate. As a new family of micro-and nanoscaled materials constructed from metal ions or metal ion clusters and polydentate bridging ligands by coordination polymerization, [4] ICPs have attracted increasing attention because of their unique properties including size-and morphology-dependent structural tailorability [5] and potential applications in many fields, such as sensing, catalysis, drug delivery, gas sorption, ion exchange, and bioimaging.[6] More interestingly, the rational inclusion and adaptive encapsulation of functional species into self-supported ICP networks during their self-assembly processes can well-formulate new materials with tailor-made and improved multifunctionalities. [7] This unique property of ICPs inspired us to synthesize bioelectrochemically active ICP nanostructures for simple electrochemical biosensing through efficiently encapsulating all biosensing elements into a single ICP nanoparticle during the c...

This study demonstrates the formation of a three-dimensional conducting framework through hybridization of bioelectrochemically active infinite coordination polymer (ICP) nanoparticles with single-walled carbon nanotubes (SWNTs) for highly sensitive and selective in vivo electrochemical monitoring with combination with in vivo microdialysis. The bioelectrochemically active ICP nanoparticles are synthesized through the self-assembly process of NAD(+) and Tb(3+), in which all biosensing elements including an electrocatalyst (i.e., methylene green, MG), cofactor (i.e., β-nicotinamide adenine dinucleotide, NAD(+)), and enzyme (i.e., glucose dehydrogenase, GDH) are adaptively encapsulated. The ICP/SWNT-based biosensors are simply prepared by drop-coating the as-formed ICP/SWNT nanocomposite onto a glassy carbon substrate. Electrochemical studies demonstrate that the simply prepared ICP/SWNT-based biosensors exhibit excellent biosensing properties with a higher sensitivity and stability than the ICP-based biosensors prepared only with ICP nanoparticles (i.e., without hybridization of SWNTs). By using a GDH-based electrochemical biosensor as an example, we demonstrate a technically simple yet effective online electroanalytical platform for continuously monitoring glucose in the brain of guinea pigs with the ICP/SWNT-based biosensor as an online detector in a continuous-flow system combined with in vivo microdialysis. Under the experimental conditions employed here, the dynamic linear range for glucose with the ICP/SWNT-biosensor is from 50 to 1000 μM. Moreover, in vivo selectivity investigations with the biosensors prepared by the GDH-free ICPs reveal that ICP/SWNT-based biosensors are very selective for the measurement of glucose in the cerebral system. The basal level of glucose in the microdialysates from the striatum of guinea pigs is determined to be 0.31 ± 0.03 mM (n = 3). The study offers a simple route to the preparation of electrochemical biosensors, which is envisaged to be particularly useful for probing the chemical events involved in some physiological and pathological processes.