Inorganic nanomaterials that mimic enzymes are fascinating as they potentially have improved properties relative to native enzymes, such as greater resistance to extremes of pH and temperature and lower sensitivity to proteases. Although many artificial enzymes have been investigated, searching for highly-efficient and stable catalysts is still of great interest. In this paper, we first demonstrated that bovine serum albumin (BSA)-stabilized MnO(2) nanoparticles (NPs) exhibited highly peroxidase-, oxidase-, and catalase-like activities. The activities of the BSA-MnO(2) NPs were evaluated using the typical horseradish peroxidase (HRP) substrates o-phenylenediamine (OPD) and 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of either hydrogen peroxide or dissolved oxygen. These small-sized BSA-MnO(2) NPs with good dispersion, solubility and biocompatibility exhibited typical Michaelis-Menten kinetics and high affinity for H(2)O(2), OPD and TMB, indicating that BSA-MnO(2) NPs can be used as satisfactory enzyme mimics. Based on these findings, BSA-MnO(2) NPs were used as colorimetric immunoassay tags for the detection of goat anti-human IgG in place of HRP. The colorimetric immunoassay using BSA-MnO(2) NPs has the advantages of being fast, robust, inexpensive, easily prepared and with no HRP and H(2)O(2) being needed. These water-soluble BSA-MnO(2) NPs may have promising potential applications in biotechnology, bioassays, and biomedicine.

A facile one-step microwave-assisted approach for the preparation of strong fluorescent carbon nitride quantum dots (g-CNQDs) by using guanidine hydrochloride and EDTA as the precursors was developed. Strong chemiluminescence (CL) emission was observed when NaClO was injected into the prepared g-CNQDs, and a novel CL system for direct detection of free chlorine was established. Free residual chlorine in water was sensitively detected with a detection limit of 0.01 μM and had a very wide detection range of 0.02 to 10 μM. On the basis of CL spectral, UV-visible absorption spectral, and electron spin resonance (ESR) spectral studies, as well as investigations on the effects of various free radical scavengers, a possible CL mechanism was proposed. It was suggested that the radiative recombination of oxidant-injected holes and electrons in the g-CNQDs accounted for the CL emission. Meanwhile, (1)O2 on the surface of g-CNQDs, generated from some reactive oxygen species in the g-CNQDs-NaClO system, could transfer energy to g-CNQDs and thus further enhance the CL emission. The CL system is highly sensitive and differentiable, opening a new field for the development of novel CL-emitting species, but also expanding the conventional optical utilizations of g-CNQDs.

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Herein, we present a novel strategy based on a "turn-on" persistent luminescence imaging chemical system of graphitic carbon nitride for detecting biothiols in biological fluids. Graphitic carbon nitride (g-C3N4) as persistent luminescence probe is fabricated via a new procedure based on pyrolysis of guanidine hydrochloride under ambient atmospheric conditions. The prepared g-C3N4 nanosheets give intensively long-persistent luminescence that can avoid interference from biological media such as tissue autofluorescence and scattering light. The original persistent luminescence of g-C3N4 turns off due to the adsorption of silver ion (Ag(+)) onto g-C3N4 materials with an electron transfer process. The presence of biothiols induces the onset of persistent luminescence emission by interrupting the quenching interaction, thereby turning on the imaging probe. The approach exhibits high specificity and high sensitivity to biothiols with low detection limit for cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) with 6.4, 8.1, and 9.6 nM, respectively. It is also successfully applied for imaging detection of biothiols in human urine, plasma, and cell lysates, demonstrating its great value of practical application in biological systems.

Natural and synthetic gel-like materials have featured heavily in the development of biomaterials for wound healing and other tissue-engineering purposes. More recently, molecular gels have been designed and tailored for the same purpose. When mixed with, or conjugated to therapeutic drugs or bioactive molecules, these materials hold great promise for treating/curing life-threatening and degenerative diseases, such as cancer, osteoarthritis, and neural injuries. This focus review explores the latest advances in this field and concentrates on self-assembled gels formed under aqueous conditions (i.e., self-assembled hydrogels), and critically compares their performance within different biomedical applications, including three-dimensional cell-culture studies, drug delivery, and tissue engineering. Although stability and toxicity issues still need to be addressed in more detail, it is clear from the work reviewed here that self-assembled gels have a bright future as novel biomaterials.

Novel highly fluorescent NH2-MIL-53(Al) was controllably synthesized by a facile one-step hydrothermal treatment of AlCl3·6H2O and NH2-H2BDC in water with urea as a modulator. The as-synthesized NH2-MIL-53(Al) nanoplates exhibited excellent water solubility and stability. In the present work, it can be found that strong fluorescence of NH2-MIL-53(Al) nanoplates was significantly suppressed after the addition of free chlorine, and a simple sensing system for fast, highly selective direct detection of free chlorine in water was established. Compared with other fluorescent sensors for free chlorine, the present methodology has a comparable detection limit of 0.04 μM (S/N = 3) and a wide detection range of 0.05 to 15 μM. On the other hand, the traditional redox-based fluorescent probes sharply suffered from the interference of MnO4(-), Cr2O7(2-), and other oxidants with stronger oxidation capability than free chlorine while ours overcame this disadvantage. Further research suggests that it is more likely the energy transfer through N-H···O-Cl hydrogen bonding interaction between amino group and ClO(-) ions plays the key role in our system, providing a new and promising platform for free chlorine determination in water quality monitoring.

Biosorption of Cu 2+ and Pb 2+ by Cladophora fascicularis was investigated as a function of initial pH, initial heavy metal concentrations, temperature and other co-existing ions. Adsorption equilibriums were well described by Langmuir and Freundlich isotherm models. The maximum adsorption capacities were 1.61 mmol/g for Cu 2+ and 0.96 mmol/g for Pb 2+ at 298 K and pH 5.0. The adsorption processes were endothermic and biosorption heats calculated by the Langmuir constant b were 39.0 and 29.6 kJ/mol for Cu 2+ and Pb 2+ , respectively. The biosorption kinetics followed the pseudo-second order model. No significant effect on the uptake of Cu 2+ and Pb 2+ by co-existing cations and anions was observed, except EDTA. Desorption experiments indicated that Na 2 EDTA was an efficient desorbent for the recovery of Cu 2+ and Pb 2+ from biomass. The results showed that Cladophora fascicularis was an effective and economical biosorbent material for the removal and recovery of heavy metal ions from wastewater.

Herein we report an approach to assess in vitro cellular responses to the dissolution or degradation products from Fmoc-diphenylalanine (Fmoc-FF) self-assembled hydrogels. Three cell lines were used in these studies and two-way ANOVA was used to assess (i) the age of gel dissolution and degradation products and (ii) exposure time on cell fate and state, using viability assays in conjunction with time-lapse fluorescence and high-resolution scanning electron microscopy investigation. The studies show that leaching time but not the exposure time affects the overall cell viability. The cytotoxic effect was only observed once the gel is completely dissolved. Further analysis revealed that the principal mechanism of cell death is necrosis. In addition, the effect of chemotherapeutics (5-fluorouracil and paclitaxel) released from the Fmoc-FF gel (with addition before and after gelation) on colorectal cancer cells were investigated using this methodology, demonstrating enhanced activity of these drugs compared to bulk control. This enhanced activity, however, appears to be a combination of the apoptosis caused by the cancer drugs and necrosis caused by gel dissolution and degradation products. Given that in vivo studies by others on Fmoc-peptides that this material is not harmful to animals, our work highlights that conventional in vitro cellular assays may yield conflicting messages when used for the evaluation of cytotoxicity and drug release from self-assembled gels such as Fmoc-FF and that better in vitro models, (e.g. 3D cell culture systems) need to be developed to evaluate these materials for biomedical applications.