Zhengqiang Li

Direct visualization of gastrointestinal tract with lanthanide-doped BaYbF5 upconversion nanoprobes

Nanoparticulate contrast agents have attracted a great deal of attention along with the rapid development of modern medicine. Here, a binary contrast agent based on PAA modified BaYbF5:Tm nanoparticles for direct visualization of gastrointestinal (GI) tract has been designed and developed via a one-pot solvothermal route. By taking advantages of excellent colloidal stability, low cytotoxicity, and neglectable hemolysis of these well-designed nanoparticles, their feasibility as a multi-modal contrast agent for GI tract was intensively investigated. Significant enhancement of contrast efficacy relative to clinical barium meal and iodine-based contrast agent was evaluated via X-ray imaging and CT imaging in vivo. By doping Tm(3+) ions into these nanoprobes, in vivo NIR-NIR imaging was then demonstrated. Unlike some invasive imaging modalities, non-invasive imaging strategy including X-ray imaging, CT imaging, and UCL imaging for GI tract could extremely reduce the painlessness to patients, effectively facilitate imaging procedure, as well as rationality economize diagnostic time. Critical to clinical applications, long-term toxicity of our contrast agent was additionally investigated in detail, indicating their overall safety. Based on our results, PAA-BaYbF5:Tm nanoparticles were the excellent multi-modal contrast agent to integrate X-ray imaging, CT imaging, and UCL imaging for direct visualization of GI tract with low systemic toxicity.

PEGylated hybrid ytterbia nanoparticles as high-performance diagnostic probes for in vivo magnetic resonance and X-ray computed tomography imaging with low systemic toxicity

Novel nanoparticulate contrast agents with low systemic toxicity and inexpensive character have exhibited more advantages over routinely used small molecular contrast agents for the diagnosis and prognosis of disease. Herein, we designed and synthesized PEGylated hybrid ytterbia nanoparticles as high-performance nanoprobes for X-ray computed tomography (CT) imaging and magnetic resonance (MR) imaging both in vitro and in vivo. These well-defined nanoparticles were facile to prepare and cost-effective, meeting the criteria as a biomedical material. Compared with routinely used Iobitridol in clinic, our PEG-Yb2O3:Gd nanoparticles could provide much significantly enhanced contrast upon various clinical voltages ranging from 80 kVp to 140 kVp owing to the high atomic number and well-positioned K-edge energy of ytterbium. By the doping of gadolinium, our nanoparticulate contrast agent could perform perfect MR imaging simultaneously, revealing similar organ enrichment and bio-distribution with the CT imaging results. The super improvement in imaging efficiency was mainly attributed to the high content of Yb and Gd in a single nanoparticle, thus making these nanoparticles suitable for dual-modal diagnostic imaging with a low single-injection dose. In addition, detailed toxicological study in vitro and in vivo indicated that uniformly sized PEG-Yb2O3:Gd nanoparticles possessed excellent biocompatibility and revealed overall safety.

Enhanced adsorptive removal of anionic and cationic dyes from single or mixed dye solutions using MOF PCN-222

Metal–organic frameworks (MOFs) are attractive for the removal of industrial dyes from aqueous pollution. However, effective simultaneous removal of oppositely charged dye ions is still a challenge. We find that zirconium–metalloporphyrin mesoMOF (PCN-222/MOF-545) exhibits excellent adsorption/removal capacities for numerous anionic and cationic dyes individually and together in solution. PCN-222 is fabricated by solvothermal synthesis and characterized by powder XRD and FT-IR methods to confirm its structure. N2 adsorption/desorption indicates PCN-222 has a large pore size of 3.2 nm and a surface area of 2336 m2 g−1. The zeta potential measurement shows that PCN-222 has a slight basic isoelectric point at pH 8 with appropriate potentials of 23.5 and −13.6 mV in the range of pH 3–10. These features facilitate the dual-function of PCN-222 toward anionic and cationic dyes, or even their complexes. The results show that PCN-222 has a maximum loading efficacy of 906 mg g−1 for anionic methylene blue (MB) and 589 mg g−1 for cationic methyl orange (MO) in a single dye system. Interestingly, when MB and MO co-exist in solution, they mutually enhance the capability by 36.8% (1239 mg g−1) for MB and 73.5% (1022 mg g−1) for MO. The adsorption kinetics, isotherms, stability and reusability of PCN-222 are reported. The results reveal that no significant changes of either crystal structure or loading capacity are observed up to eight recycles during the removal of MO and MB in solution. The adsorption efficacies of eight representative dyes are presented. Compared with previously published data, the capacity of PCN-222 ranks at the top. We prepared a facile adsorption chromatography column to demonstrate the broad application potentials of PCN-222 in dye removal from aqueous pollution. Finally, we propose a push–pull mechanism to explain the mutual enhancement of adsorption in a mixture dye solution.

Immobilization of Lactobacillus rhamnosus in mesoporous silica-based material: An efficiency continuous cell-recycle fermentation system for lactic acid production.

Lactic acid bacteria immobilization methods have been widely used for lactic acid production. Until now, the most common immobilization matrix used is calcium alginate. However, Ca-alginate gel disintegrated during lactic acid fermentation. To overcome this deficiency, we developed an immobilization method in which Lactobacillus rhamnosus cells were successfully encapsulated into an ordered mesoporous silica-based material under mild conditions with a high immobilization efficiency of 78.77% by using elemental analysis. We also optimized the cultivation conditions of the immobilized L. rhamnosus and obtained a high glucose conversion yield of 92.4%. Furthermore, L. rhamnosus encapsulated in mesoporous silica-based material exhibited operational stability during repeated fermentation processes and no decrease in lactic acid production up to 8 repeated batches.

Fish-in-net, a novel method for cell immobilization of Zymomonas mobilis.

Background Inorganic mesoporous materials exhibit good biocompatibility and hydrothermal stability for cell immobilization. However, it is difficult to encapsulate living cells under mild conditions, and new strategies for cell immobilization are needed. We designed a “fish-in-net” approach for encapsulation of enzymes in ordered mesoporous silica under mild conditions. The main objective of this study is to demonstrate the potential of this approach in immobilization of living cells. Methodology/Principal Findings Zymomonas mobilis cells were encapsulated in mesoporous silica-based materials under mild conditions by using a “fish-in-net” approach. During the encapsulation process, polyethyleneglycol was used as an additive to improve the immobilization efficiency. After encapsulation, the pore size, morphology and other features were characterized by various methods, including scanning electron microscopy, nitrogen adsorption-desorption analysis, transmission electron microscopy, fourier transform infrared spectroscopy, and elemental analysis. Furthermore, the capacity of ethanol production by immobilized Zymomonas mobilis and free Zymomonas mobilis was compared. Conclusions/Significance In this study, Zymomonas mobilis cells were successfully encapsulated in mesoporous silica-based materials under mild conditions by the “fish-in-net” approach. Encapsulated cells could perform normal metabolism and exhibited excellent reusability. The results presented here illustrate the enormous potential of the “fish-in-net” approach for immobilization of living cells.

Structure advantage and peroxidase activity enhancement of deuterohemin-peptide–inorganic hybrid flowers

This work reports a facile method for hybridizing deuterohemin-peptide (DhHP-6) with copper phosphate to form deuterohemin-peptide–inorganic hybrid flowers (DhHP-6–Cu3(PO4)2) by self-assembly. The DhHP-6–Cu3(PO4)2 flowers have been characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and solid state UV-vis. In the assembly process, the DhHP-6 peptides are fixed on Cu3(PO4)2 through the coordination of the end amino acids (Lys6) with copper(II) centers. The rearrangement of Lys6 prevents DhHP-6 aggregation. Hence, DhHP-6–Cu3(PO4)2 flowers exhibit a nearly 300% enhancement of peroxidase-like activity in comparison with free DhHP-6 in solution. Meanwhile, the DhHP-6–Cu3(PO4)2 flowers show stronger affinity towards 3,3,5,5-tetramethylbenzidine (TMB) and H2O2 than free DhHP-6 and horseradish peroxidase (HRP). In addition, EPR results provide direct evidences for the mechanisms of DhHP-6–Cu3(PO4)2 flower growth and activity enhancement. Furthermore, the sample presents excellent reusability and storage stability.

Clues for discovering a new biological function of Vitreoscilla hemoglobin in organisms: potential sulfide receptor and storage

The interaction between H2S and Vitreoscilla hemoglobin (VHb) has been studied by UV–Vis and Resonance Raman spectroscopes to confirm the binding between the ligand and the protein. Kinetic constants, kon = 1.2 × 105 m−1·s−1 and koff = 2.5 × 10−4·s−1, have been determined and compared with those for mammalian hemoglobins. Density Functional Theory study supports the binding of H2S by modeling the configurations of HOMO dispersions. We hypothesized that VHb is involved in H2S reception and storage. Different from Lucina pectinata HbI, a typical H2S‐binding hemoglobin, VHb, exhibits unusual properties on H2S reactivity such as steric constraints playing an important role in modulating H2S entry. A distinct mechanism of VHb interaction with H2S is supported by studies of variant forms of VHb.

Proximal environment controlling the reactivity between inorganic sulfide and heme-peptide model

In order to gain a comprehension of the binding between inorganic sulfide and heme-containing proteins, we synthesized a series of deuterohemin-His-peptides (DhHPs) referred to as the active centers of cytochrome c as heme models to investigate the effects of the proximal environment on the reactivity when there is a lack of distal residues. DhHPs contain synthetic peptides with 2, 3, 4, 5, and 6 amino acids, respectively, whereas the imidazole side chain of His2 serves as the fifth ligand for all ferric centers. The coordination of sulfide to the ferric iron was confirmed by UV-Vis and EPR spectroscopy and the kinetic constants of the binding reaction were determined using a stopped-flow technique. Deuterohemin-AlaHisThrValGluLys (DhHP-6) exhibits an association rate constant kon = 2.34 × 104 M−1 s−1, which is 4-times faster than that found for deuterohemin-AlaHis (DhHP-2). The koff values of all the DhHPs are close and independent of the lengths and sequences of the peptides. It is hypothesized that the proximal environment plays an important role in the association processes, in which H-bond networks provided by proximal polar residues may facilitate the reaction. Moreover, the existence of Glu induces a substantial increase in the kon value of DhHP-5 and -6, indicating that the introduction of Glu5 enhances the reactivity of sulfide towards the ferric centers. We have also prepared a deuterohemin-β-Ala-β-Ala-Thr-Val-Glu-Lys (DhAP-6) derivative with Ala2 replacing His2. The results show that sulfide does not coordinate with the ferric center in DhAP-6, but reduces it to ferrous.

Nonresonant chemical mechanism in surface-enhanced Raman scattering of pyridine on M

By employing density functional theory (DFT), this study presents a detailed analysis of nonresonant surface-enhanced Raman scattering (SERS) of pyridine on M@Au12 (M = V(-), Nb(-), Ta(-), Cr, Mo, W, Mn(+), Tc(+), and Re(+))-the stable 13-atom neutral and charged gold buckyball clusters. Changing the core atom in M@Au12 enabled us to modulate the direct chemical interactions between pyridine and the metal cluster. The results of our calculations indicate that the ground-state chemical enhancement does not increase as the binding interaction strengthens or the transfer charge increases between pyridine and the cluster. Instead, the magnitude of the chemical enhancement is governed, to a large extent, by the charged properties of the metal clusters. Pyridine on M@Au12 anion clusters exhibits strong chemical enhancement of a factor of about 10(2), but the equivalent increase for pyridine adsorbed on M@Au12 neutral and cation clusters is no more than 10. Polarizability and deformation density analyses clearly show that compared with the neutral and cation clusters, the anion clusters have more delocalized electrons and occupy higher energy levels in the pyridine-metal complex. Accordingly, they produce larger polarizability, leading to a stronger nonresonant enhancement effect.