Synthesis of intrinsic dual-emission type N,S-doped carbon dots for ratiometric fluorescence detection of Cr (VI) and application in cellular imaging.

In this paper, intrinsic dual-emission fluorescent carbon dots (CDs) doped with N and S atoms have been firstly fabricated. The characterization results show that CDs are successfully synthesized with two separate fluorescence emissions at 468 nm and 628 nm, respectively. The strong and selective interaction of Cr (VI) ions with CDs lead to obvious fluorescence decrease of CDs at 468 nm, which is caused by a mixed quenching mechanism. At the same time, the fluorescence at 628 nm increase. Interestingly, the CDs solution show obvious color change under the daylight and UV light, so visualization detection of Cr (VI) can be realized in water samples. Based on the data of the emission intensity ratios of F468/F628, Cr (VI) can be detected from 3.8 to 38.9 µM combined with the linear correlation coefficient of 0.998, and the lowest detection concentration is 47.2 nM. The platform is satisfactorily applied to the detection of Cr (VI) ions in water samples. In addition, the CDs could be applied as fluorescent probes for cell imaging with dual fluorescent emission.

Synthesis of carbon dots for Al3+ sensing in water by fluorescence assay.

Fifty-four Eucommia ulmoides leaves were subjected to a hydrothermal technique to synthesize carbon dots (CDs) of 3.55 ± 1.45 nm size. The nanomaterial possessed excellent stability and strong fluorescence emission (φf 42.3%). In a neutral buffer solution, the fluorescence signals of CDs solution were enhanced by aluminium ion without interference from other ions. Degree of enhancement correlated linearly with the Al3+ content in the range 0.01-2.5 mM. Response of this method was fast and sensitive (detection limit was 23 nM). The CDs performed successfully as a sensitive sensor for trace Al3+ determination in water samples, and satisfactory results were obtained.

Persistence and boundedness in a two-species chemotaxis-competition system with singular sensitivity and indirect signal production.

This paper deals with a two-species chemotaxis-competition system involving singular sensitivity and indirect signal production: $ \begin{equation*} \begin{cases} u_{t} = \nabla\cdot(D(u)\nabla u)-\chi_1\nabla\cdot(\frac{u}{z^{k}}\nabla z)+\mu_1 u(1-u-a_1v), &x\in\Omega,\ t>0,\\ v_{t} = \nabla\cdot(D(v)\nabla v)-\chi_2\nabla\cdot(\frac{v}{z^{k}}\nabla z)+\mu_2 v(1-v-a_2 u), &x\in\Omega,\ t>0,\\ w_{t} = \Delta w-w+u+v,&x\in\Omega,\ t>0,\\ z_{t} = \Delta z-z+w,&x\in\Omega,\ t>0,\\ \end{cases} \end{equation*} $ where $ \Omega\subset R^{n} $ is a convex smooth bounded domain with homogeneous Neumann boundary conditions. The diffusion functions $ D(u), D(v) $ are assumed to fulfill $ D(u)\geq(u+1)^{\theta_1} $ and $ D(v)\geq(v+1)^{\theta_2} $ with $ \theta_1, \theta_2 > 0 $, respectively. The parameters are $ k\in (0, \frac{1}{2})\cup (\frac{1}{2}, 1] $, $ \chi_ {i} > 0, (i = 1, 2) $. Additionally, $ \mu_{i} $ should be large enough positive constants, and $ a_i $ should be positive constants which are less than the quantities associated with $ |\Omega| $. Through constructing some appropriate Lyapunov functionals, we can find the lower bounds of $ \int_{\Omega}u $ and $ \int_{\Omega}v $. This suggests that any occurrence of extinction, if it happens, will be localized spatially rather than affecting the population as a whole. Moreover, we demonstrate that the solution remains globally bounded if $ \min\{\theta_1, \theta_2\} > 1-\frac{2}{n+1} $ for $ n\geq2. $.

Global existence and blow up of solutions for a class of coupled parabolic systems with logarithmic nonlinearity.

According to the difference of the initial energy, we consider three cases about the global existence and blow-up of the solutions for a class of coupled parabolic systems with logarithmic nonlinearity. The three cases are the low initial energy, critical initial energy and high initial energy, respectively. For the low initial energy and critical initial energy $ J(u_0, v_0)\leq d $, we prove the existence of global solutions with $ I(u_0, v_0)\geq 0 $ and blow up of solutions at finite time $ T < +\infty $ with $ I(u_0, v_0) < 0 $, where $ I $ is Nehari functional. On the other hand, we give sufficient conditions for global existence and blow up of solutions in the case of high initial energy $ J(u_0, v_0) > d $.

An efficient fluorescent nano-sensor of N-doped carbon dots for the determination of 2,4,6-trinitrophenol and other applications.

N-Doped carbon dots (CDs) had been simply produced by a one-pot synthesis process using amygdalic acid and threonine. The resulting product was water-soluble and exhibited strong luminescence emission with a fluorescence quantum yield of 19.25%. The emission of CDs was obviously and selectively decreased upon adding 2,4,6-trinitrophenol (TNP). It was proved that the fluorescence resonance energy transfer was the main mechanism for quenching. An efficient fluorescence probe with satisfied sensitivity for TNP determination was found. The range of the linear response for TNP detection was 0.5-40.0 µmol L-1, and the limit of detection was 20 nmol L-1. The content of trace TNP in water samples was successfully detected with this method. The CDs were also applied in HepG2 cell imaging and the fabrication of fluorescent films by dispersing the solid freeze-drying CD (SCD) powder into PMMA, which exhibited some application value in biology and photovoltaics.

One-pot synthesis of aqueous soluble and organic soluble carbon dots and their multi-functional applications.

Two kinds of carbon dots (CDs) with different solubility, aqueous soluble CDs (ACDs) and organic soluble CDs (OCDs), were produced at the same time by one step hydrothermal synthesis method using sorbic acid and proline as carbon precursor and nitrogen dopant, respectively. The synthesized CDs were characterized by means of UV, fluorescence, TEM, elemental analysis, IR and XPS et al. Based on the effective and proportional fluorescence quenching by Cr(VI), ACDs were successfully used as a high sensitive and selective probe for Cr(VI) detection. Internal filtration effect (IFE) played an important role in the quenching process. Under the optimal conditions, linear response for Cr(Ⅵ) was observed in the range of 0.5-100 µmol/L, and the calculated detection limit was 34 nmol/L. The method has been satisfactorily applied to detect Cr(VI) ions in real water samples of our campus. Then, the ACDs were further applied for cell imaging in B16F10 cells. Furthermore, OCDs were well dispersed into PMMA to fabricate OCDs/PMMA composites as fluorescent films.

Oleanonic acid ameliorates pressure overload-induced cardiac hypertrophy in rats: The role of PKCζ-NF-κB pathway.

It has been reported that inflammation is closely related with cardiac hypertrophy. Some inflammatory cytokines such as tumor necrosis factor-α, interleukin-1ß, and interleukin-6 directly induce cardiac hypertrophy, which is associated with the activation of nuclear factorkappa B (NF-κB). Thus, NF-κB is an attractive target for cardiac hypertrophy. In the present study, oleanonic acid inhibited the elevation of transcriptional activity of NF-κB and reduced the mRNA expressions of hypertrophic genes such as atrial natriuretic factor (ANF) and brain natriuretic peptide (BNP) in a concentration-dependent manner in phenylephrine (PE)-treated cardiomyocytes. Furthermore, we found that oleanonic acid inhibited the phosphorylation of protein kinase C ζ (PKCζ) at Thr410 site and then reduced the activation of NF-κB using gain- and loss-of-function approaches in PE-treated cardiomyocytes. In vivo, similar results were observed in abdominal aortic constriction (AAC) rats that were intragastrically administered with oleanonic acid, and the pathological changes accompanying cardiac hypertrophy were relieved. In conclusion, oleanonic acid can effectively ameliorate cardiac hypertrophy by inhibiting PKCζ-NF-κB signaling pathway.

Insulin-loaded PLGA microspheres for glucose-responsive release.

Porous poly(lactic-co-glycolic acid) (PLGA) microspheres were prepared, loaded with insulin, and then coated in poly(vinyl alcohol) (PVA) and a novel boronic acid-containing copolymer [poly(acrylamide phenyl boronic acid-co-N-vinylcaprolactam); p(AAPBA-co-NVCL)]. Multilayer microspheres were generated using a layer-by-layer approach depositing alternating coats of PVA and p(AAPBA-co-NVCL) on the PLGA surface, with the optimal system found to be that with eight alternating layers of each coating. The resultant material comprised spherical particles with a porous PLGA core and the pores covered in the coating layers. Insulin could successfully be loaded into the particles, with loading capacity and encapsulation efficiencies reaching 2.83 ± 0.15 and 82.6 ± 5.1% respectively, and was found to be present in the amorphous form. The insulin-loaded microspheres could regulate drug release in response to a changing concentration of glucose. In vitro and in vivo toxicology tests demonstrated that they are safe and have high biocompatibility. Using the multilayer microspheres to treat diabetic mice, we found they can effectively control blood sugar levels over at least 18 days, retaining their glucose-sensitive properties during this time. Therefore, the novel multilayer microspheres developed in this work have significant potential as smart drug-delivery systems for the treatment of diabetes.

Glucose- and temperature-sensitive nanoparticles for insulin delivery.

Glucose- and temperature-sensitive polymers of a phenylboronic acid derivative and diethylene glycol dimethacrylate (poly(3-acrylamidophenyl boronic acid-b-diethylene glycol methyl ether methacrylate); p(AAPBA-b-DEGMA)) were prepared by reversible addition-fragmentation chain transfer polymerization. Successful polymerization was evidenced by 1H nuclear magnetic resonance and infrared spectroscopy, and the polymers were further explored in terms of their glass transition temperatures and by gel permeation chromatography (GPC). The materials were found to be temperature sensitive, with lower critical solution temperatures in the region of 12°C-47°C depending on the monomer ratio used for reaction. The polymers could be self-assembled into nanoparticles (NPs), and the zeta potential and size of these particles were determined as a function of temperature and glucose concentration. Subsequently, the optimum NP formulation was loaded with insulin, and the drug release was studied. We found that insulin was easily encapsulated into the p(AAPBA-b-DEGMA) NPs, with a loading capacity of ~15% and encapsulation efficiency of ~70%. Insulin release could be regulated by changes in temperature and glucose concentration. Furthermore, the NPs were non-toxic both in vitro and in vivo. Finally, the efficacy of the formulations at managing blood glucose levels in a murine hyperglycemic diabetes model was studied. The insulin-loaded NPs could reduce blood glucose levels over an extended period of 48 h. Since they are both temperature and glucose sensitive and offer a sustained-release profile, these systems may comprise potent new formulations for insulin delivery.