Xue Qu

Template size matched film thickness for effectively in situ surface imprinting: a model study of glycoprotein imprints

Precisely controlling the material structure is a high requirement for biological target imprinting. In situ surface imprinting immobilized templates can offer thin-film molecular imprints containing site-directed binding sites on substrates, and therefore is appropriate for biological targets. However, the correlation between the required film thickness for superior imprinting effect and the bulk structure of biological template is not clearly understood. Here we use a series of glycoprotein imprinted films as a model to give a semi-quantitative description for their correlation. Glycoproteins with distinguished molecular sizes including ribonuclease B, glucose oxidase and horseradish peroxidase were used as templates. Covalently immobilizing glycoproteins was achieved by using m-aminophenylboronic acid modified SiO2 or Fe3O4 surface. Dopamine was polymerized onto this surface for glycoprotein imprinting. Varying polymerization time provided a series of thickness tunable imprinting films in nanometer-scale. The binding isotherm study for each glycoprotein imprints with different film thickness was performed. The optimal film thickness for the highest binding capacities and imprinting factors shows a positive correlation with its template size. The each optimized glycoprotein imprints can recognize their template in a simple or complex environment. These results suggest that the thickness of imprinted film should be tailored for matching the geometric size of fixed templates, and reveal the substantial influence of template structure on imprints design.

Self-assembly of dual drug-delivery coating for synergistic bone regeneration

Bone regeneration for the treatment of bone diseases represents a major clinical need. Introducing recombinant human bone morphogenetic protein-2 (rhBMP-2) into biomaterials is an extensively used approach to induce osteogenic differentiation and accelerate bone regeneration. However, serious adverse events can occur in the event of an overdose of rhBMP-2. Dexamethasone (DEX) is a synthetic hydrophobic glucocorticoid, which can enhance rhBMP-2-induced osteogenic differentiation by binding to a glucocorticoid receptor intracellularly. In this study, we have developed a multilayered composite coating made of poly(l-lactide-co-glycolide) (PLGA) nanoparticles, heparin and chitosan to deliver DEX and rhBMP-2 dually. The coating can reserve DEX and rhBMP-2 using the building blocks of the PLGA nanoparticles and heparin. Sustained release of DEX and rhBMP-2 by this coating was achieved. Moreover, a flow cytometry assay suggests that the PLGA nanoparticles could be transported across the cell membrane and presumably could improve the intracellular delivery of DEX via cell internalization. The in vitro osteogenesis studies reveal that the dual drug-loaded coating has a synergistic osteogenic differentiation effect on C2C12 myoblasts, as indicated by the upregulation of the alkaline phosphatise activity and osteo-related gene expression. In addition, μCT and histological analysis of the in vivo experiments demonstrate that the dual drug-loaded coating induced more ectopic bone formation than the individual drug-loaded coating. Therefore, this study demonstrates that our coating system can reserve these two drugs and deliver them locally to cells with the ability to induce rapid osteogenic differentiation and bone regeneration synergistically. Compared to other reported DEX/rhBMP-2 delivery systems, our coating system represents a simple, safe and effective dual drug delivery alternative. Moreover, since a layer-by-layer strategy is easily applied onto varying substrates, our coating system can be combined with many commercially available or existing biomaterials to improve their osteogenetic performance.

Biofabricated nanoparticle coating for liver-cell targeting.

Biology routinely uses noncovalent interactions to perform complex functions that range from the molecular recognition of ligand-receptor binding to the reversible self-assembly/disassembly of hierarchical nanostructures (e.g., virus particles). Potentially, biological materials that offer such recognition and reversible self-assembly functionality can be applied to nanomedicine. Here, polysaccharides with the multifunctional polysaccharide-binding protein Concanavalin A (Con A) are coupled to create a functional nanoparticle coating. This coating is self-assembled in a layer-by-layer format by sequentially contacting a nanoparticle with Con A and the polysaccharide glycogen. In the final assembly step, a galactomannan targeting ligand is self-assembled into the coating. Evidence indicates that the mannose residues of the galactomannan backbone are responsible for assembly into the coating by Con A binding, while the galactose side chain residues are responsible for targeting to the liver-specific asialoglycoprotein receptor (ASGP-R). Binding to ASGP-R induces endocytic uptake, while the low endosomal pH triggers disassembly of the coating and release of the nanoparticle-entrapped drug. In vitro cell studies indicate that the coating confers liver-cell-specific function for both nanoparticle uptake and drug delivery. These studies extend the use of Con A to sugar-mediated and organ-specific targeting, and further illustrate the potential of biologically based fabrication for generating functional materials.

Targetable N-annulated perylene-based colorimetric and ratiometric near-infrared fluorescent probes for the selective detection of hydrogen sulfide in mitochondria, lysosomes, and serum

Hydrogen sulfide (H2S) serves an effective role in biological systems as the acknowledged third endogenous gasotransmitter, so it makes great sense to detect and analyze H2S sensitively and quantitatively in subcellular environments, such as in mitochondria and lysosomes where H2S is widespread and functions as the mediator. Considering the excellent photophysical properties and multiple modification sites, N-annulated perylene (NP) was firstly chosen as the fluorophore to design a series of colorimetric and ratiometric near-infrared (NIR) fluorescent probes for the sensitive and selective detection of H2S. The probes showed near-infrared fluorescence at 681 nm in the absence of H2S. But with the addition of H2S, the NIR fluorescence decreased sharply and a new fluorescence peak at approximately 481 nm dramatically increased in a short response time, which could be clearly observed using the naked eye. Their large ratiometric fluorescence changes (about 200 nm), excellent selectivity and stability would be helpful for its detection in biological systems, and the limit of detection of the probe was calculated down to 139 nM. The reaction mechanism was studied as well. The targetable probes (Mito-NPNM and Lyso-NPNM) were also successfully employed to detect endogenous H2S in the mitochondria and lysosomes of living cells respectively. Besides, these probes were successfully applied to quantify H2S at low concentrations in serum where H2S levels are of great significance as an important indicator of various diseases.

A red fluorescent turn-on chemosensor for Al3+ based on a dimethoxy triphenylamine benzothiadiazole derivative with aggregation-induced emission

Aluminum is a known neurotoxin to organisms and believed to cause Alzheimers disease, osteomalacia, and breast cancer. Therefore, effective tools for Al3+ recognition are in great demand. In this study, a new, sensitive, and highly selective red turn-on chemosensor (TB-COOH) for Al3+ was prepared by combining the dimethoxy triarylamine benzothiadiazole motif and carboxyl group, where the benzothiadiazole derivative functioned as an aggregation-induced emission (AIE) moiety and the carboxyl motif functioned as the recognition site for Al3+. This chemosensor showed significant fluorescence enhancement upon selective addition of Al3+ and a relatively low detection limit (1.5 × 10−7 M). The fluorescence turn-on mechanism was ascribed to the aggregation of TB-COOH after complexation with Al3+, which was confirmed by 1H NMR and FT-IR spectroscopies and scanning electronic microscopy. Furthermore, benefiting from its good water solubility and biocompatibility, imaging detection and real-time monitoring of Al3+ in living HeLa cells were successfully achieved.

Synthesis, two-photon absorption and aggregation-induced emission properties of multi-branched triphenylamine derivatives based on diketopyrrolopyrrole for bioimaging

In this work, three new diketopyrrolopyrrole (DPP)-based multi-branched derivatives (YJ-1, YJ-2 and YJ-3) with triphenylamine, 2,4,6-tri([1,1′-biphenyl]-4-yl)-1,3,5-triazine and 2,2′,2′′-(nitrilotr-is([1,1′-biphenyl]-4′,4-diyl))tris(3-phenylacrylonitrile) cores have been designed and synthesized. Their one- and two-photon absorption properties have been investigated. The two-photon absorption cross sections (σ) measured by the open aperture Z-scan technique are determined to be 2912, 2016 and 2800 GM for YJ-(1–3), respectively. This result indicates that donor–acceptor–donor (D–A–D)-type molecules are benefit to improve σ and their σ data increase with the better intramolecular charge transfer (ICT). Also, all of the three DPP derivatives exhibit good aggregation-induced emission (AIE) properties which are very weakly fluorescent in DMF, but a strong red fluorescent emission in solid state and in the aggregate state. More importantly, diketopyrrolopyrrole with tri-phenylamine (YJ-1) was applied for cell imaging and two-photon excited fluorescence in vivo imaging of mouse ear.

13C NMR aided design of molecularly imprinted adsorbents for selectively preparative separation of erythromycin

Molecularly imprinted polymers (MIPs) with high binding performance and good selectivity are of interest not only in the field of analytical chemistry, but also in the bio-pharmaceutical industry because of their potential use as affinity sorbents for selectively preparative separation of drug molecules. The choice of a suitable functional monomer for the template molecule plays a key role in the performance of MIPs. Erythromycin (ERY; C37H67NO13; mol wt 733.9), produced by bio-fermentation, is a representative macrolide antibiotic with multiple polar groups. In the present study, 13C NMR spectroscopy for the first time was employed to evaluate the interactions between ERY and a set of functional monomers at the atomic level. Based on the 13C chemical shift changes in the ERY molecular structure when binding with different functional monomers, the optimal monomer of methacrylic acid (MAA) was selected and the rational binding sites were predicted. A sequence regarding the interaction force of these binding sites for MAA was proposed, and Density Functional Theory (DFT) theoretical calculation of Lewis basicity of the O/N atoms located at these sites confirmed its reliability. Molecularly imprinted sorbents (MIAs) for ERY were prepared by a suspension polymerization method using MAA as a functional monomer and ethylene glycol dimethacrylate (EGDMA) as a cross-linker. The effects of the monomer to template ratio and the solvent environment employed during the adsorption on the imprinting efficiency of MIAs were both discussed. The adsorption isotherm of ERY on MIAs was fitted by the Langmuir isotherm model. And the specific selectivity of these materials towards ERY was confirmed. The optimized MIAs as column packing materials can separate ERY from its crystal mother liquid with high recovery and good selectivity, exhibiting a promising capability for productive separation of ERY in a large scale. To the best of our knowledge, these results for the first time indicated that 13C NMR spectroscopy is a simple and effective method for the rational design of MIAs towards complex template molecules. The separation model built in this study represents a novel application of MIPs for future industrial production.

Electrical signals triggered controllable formation of calcium-alginate film for wound treatment

Wound dressings play important roles in the management of wounds, and calcium cross-linked alginate (Ca2+-Alg) is a commonly used hydrogel that is adapted for wound treatment. However, conventional methods for fabricating Ca2+-Alg hydrogels can be tedious and difficult to control because of the rapid Ca2+-induced gelation of alginate. In this study, An electrodeposition method was used to rapidly and controllably fabricate Ca2+-Alg films for wound treatment. Several measures of film growth (e.g., thickness and mass) are shown to linearly correlate to the imposed charge transfer at the electrode. Similarly, this charge transfer was also observed to control important physicochemical wound healing properties such as water uptake and retention capacity. Furthermore, a wound healing animal test was performed to evaluate the performance of this electro-fabricated calcium alginate film for wound treatment. This in vivo study demonstrated that wounds dressed with an electro-fabricated Ca2+-Alg film closed faster than that of untreated wounds. Further, the new dermis tissue that formed was composed of reorganized and stratified epithelial layer, with fully developed connective tissue, hair follicle, sebaceous glands as well as aligned collagen. Therefore, our study indicates that this electrofabrication method for the rapid and controlled preparation of alginate film could provide exciting opportunities for wound treatment. More broadly, this study demonstrates the potential of electrochemistry for the fabrication of high performance polymeric materials.Graphical AbstractHere we report a rapid and controllable fabrication of free-standing alginate films by coupling anodic electrodeposition with subsequent peeling of deposited materials for wound dressing.

Selective extraction of bioactive glycoprotein in neutral environment through Concanavalin A mediated template immobilization and dopamine surface imprinting

Glycoproteins play important roles in various biological events. Extraction of specific bioactive glycoproteins from physiological fluids is highly required for clinical diagnosis and treatment. Concanavalin A (Con A) is a tetramer lectin protein that can specifically bind glycospecies containing sugar units, and this binding occurs in physiological environments. Inspired by this, we propose a sugar–lectin recognition based glycoprotein surface imprint, which is anticipated to selectively extract bioactive glycoproteins in physiological environments. The glycosylated biomarker, transferrin, was used as a model template. Transferrin was first immobilized on a Con A modified Fe3O4 surface via the sugar–lectin interaction at pH 7.4. Dopamine was then polymerized onto this surface for glycoprotein imprinting at the same pH, and continuous oxygen bubbling into the dopamine solution improved the polymerization speed. After removal of the template by boronate buffer, transferrin imprinted Fe3O4 was obtained. The subsequent binding experiment indicated that the transferrin imprint has pH dependent binding affinity towards this protein. The optimal transferrin binding capacity, as well as the maximum imprinting factor was observed at neutral pH. The isotherm adsorption study reveals that imprinted and non-imprinted material are both fitted with the Langmuir adsorption model. Single selective adsorption and competitive adsorption experiments show that the obtained surface imprint has selectivity towards template glycoprotein, and circular dichroism (CD) spectral analysis indicates that boronate buffer washing has no negative influence on the natural structure of transferrin and Con A. These results demonstrate that this novel glycoprotein surface imprint can work under physiological conditions, and the glycoprotein extraction method is mild enough to keep the bioactivity of these targets for further bio-application.

Effect of the solvent on improving the recognition properties of surface molecularly imprinted polymers for precise separation of erythromycin

The formation of thin films with imprinting sites that can be accessed more rapidly by target molecules is an improvement in bulk molecular imprinting polymers. To achieve suitable properties for specific application, on the basis of our previous study of bulk erythromycin (ERY) imprinted polymers, we here rationally design, generate and test surface-imprinted polymers specific for ERY. ERY-A surface-imprinted glass fibers (GF-MIPs) were fabricated using glass fibers as the matrix, methacrylic acid (MAA) as the functional monomer, ethyleneglycol dimethacrylate (EGDMA) as the cross-linker and azobis(4-cyanovaleric acid) as the initiator. Then, we specifically studied the effect of the solvent on the recognition performance of the GF-MIPs. 13C-NMR and isothermal titration calorimetry (ITC) measurements were employed to demonstrate that the addition of NH3·H2O can block the interactions between the –COOH group and the tertiary amine on ERY-A. The results of static adsorption and dynamic separation experiments also indicate that an increase of specificity can easily be obtained by mediating the solvent environment, thus satisfying the more stringent requirements of precise separation.