Changjun Liu

Mg/N double doping strategy to fabricate extremely high luminescent carbon dots for bioimaging

Carbon dots (CDs) with quantum yield up to 83% have been synthesized with a Mg/N double doping fluorescence-enhanced strategy. Besides N-mediated surface passivation by ethylenediamine, the Mg–citric acid chelate played the roles of introducing Mg and preserving the carboxyl group, both greatly contributing to the photoluminescence enhancement of the final CDs. Importantly, the N- and Mg-doping functioned in concert without mutual influence.

One-step synthesis of nanohybrid carbon dots and TiO2 composites with enhanced ultraviolet light active photocatalysis

Nano-hybrid composites of carbon dots (CDs) and titanium dioxide (TiO2) were fabricated by a designed one-step solvothermal method. The crystallinity of TiO2, morphologies and ingredients of the CDs–TiO2 composites could be adjusted by the reaction time. Furthermore, the measurements of photo-degradation on methyl blue (MB) showed excellent photocatalytic activity of the CDs–TiO2 composites under ultraviolet (UV) light irradiation, which was much higher than that of commercial Degussa P25. However, C–TiO2 composites, which were produced from the CDs–TiO2 composites by a further calcination, showed more excellent photocatalytic activity for the photo-degradation of methyl orange (MO) and rhodamine B (RB).

Modification of collagen-chitosan matrix by the natural crosslinker alginate dialdehyde.

In the present study, collagen (Coll) was mixed with the natural crosslinker chitosan (CTS), and then, alginate dialdehyde (ADA) was added to crosslink the mixtures. The properties of these Coll matrix sponges were investigated afterwards. Fourier transform infrared spectroscopy (FTIR) analysis and in vitro fiber formation analysis showed the intact retention of the classical triple-helical structure after crosslinking. Scanning electron microscopy (SEM) showed that microfibril structural interactions between Coll structures became more compact. Significant improvement in the thermostability of the crosslinked mixtures was observed with the pure mixtures of Coll and CTS. Antibacterial activity measurements indicated no affect of ADA on Coll/CTS sponges. In conclusion, the modification of the Coll/CTS mixtures with ADA preserves the classical triple-helical structure, enhances stabilization, maintains good biocompatibility and may pave the way for new medical applications.

Blood clot initiation by mesoporous silica nanoparticles: dependence on pore size or particle size?

Mesoporous silica nanoparticles (MSNs) with controllable pore size and particle size were prepared using a vesicle-organic template method. Transmission electron microscopy (TEM), nitrogen adsorption measurements, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectra were used to characterize the coagulation-promoting surface chemistry, topologies and porous structure of the MSNs. The clotting blood tests (CBTs) showed that the pore sizes of the MSNs varying from 5 nm to 15 nm greatly affected the blood clot rate of rabbit plasma, while variation of the particle size from 60 nm to 220 nm had little influence on coagulation. Associated with the blood coagulation factor XII (FXII) tests, it could be inferred that the accessibility and diffusion of clotting were mainly dependent on the pore size of the MSNs. Proper pore size could readily promote the blood proteins to contact the huge interior surfaces of the MSNs and then initiate the quick blood clot. Furthermore, the perfect biocompatibility of the MSNs was achieved through a CCK-8 and cellular uptake study, indicating that cell viability could be promoted by MSNs and MSNs with larger pore size showed better biocompatibility. Rapid hemostasis in rabbit femoral artery injury testified the superb hemostatic efficiency of the MSNs. We demonstrated that MSNs with a pore size of 15 nm showed the best hemostatic efficiency and it would be probably an optimal candidate for the first aid of hemorrhage in the field or pre-hospital.

Comparison of the properties of collagen–chitosan scaffolds after γ-ray irradiation and carbodiimide cross-linking

Abstract The property of collagen–chitosan porous scaffold varies according to cross-linking density and scaffold composition. This study was designed to compare the properties of collagen–chitosan porous scaffolds cross-linked with γ-irradiation and carbodiimide (CAR) for the first time. Eleven sets of collagen–chitosan scaffolds containing different concentrations of chitosan at a 5% increasing gradient were fabricated. Fourier transform infrared spectroscopy was performed to confirm the success of cross-linking in the scaffolds. The scaffold morphology was evaluated under scanning electron microscope (SEM). SEM revealed that chitosan was an indispensable material for the fabrication of γ-ray irradiation scaffold. The microstructure of γ-ray irradiation scaffold was less stable than those of alternative scaffolds. Based upon swelling ratio, porosity factor, and collagenase degradation, γ-ray irradiation scaffold was less stable than CAR and 25% proportion of chitosan scaffolds. Mechanical property determines the orientation in γ-irradiation and CAR scaffold. In vitro degradation test indicated that γ-irradiation and CAR cross-linking can elevate the scaffold biocompatibility. Compared with γ-ray irradiation, CAR cross-linked scaffold containing 25% chitosan can more significantly enhance the bio-stability and biocompatibility of collagen–chitosan scaffolds. CAR cross-linked scaffold may be the best choice for future tissue engineering.

Surface Functionalization of Polyethersulfone Membrane with Quaternary Ammonium Salts for Contact-Active Antibacterial and Anti-Biofouling Properties

Biofilm is a significant cause for membrane fouling. Antibacterial-coated surfaces can inhibit biofilm formation by killing bacteria. In this study, polyethersulfone (PES) microfiltration membrane was photografted by four antibiotic quaternary ammonium compounds (QACs) separately, which were synthesized from dimethylaminoethyl methacrylate (DMAEMA) by quaternization with butyl bromide (BB), octyl bromide (OB), dodecyl bromide (DB), or hexadecyl bromide (HB). XPS, ATR-FTIR, and SEM were used to confirm the surfaces’ composition and morphology. After modification, the pores on PES-g-DMAEMA-BB and PES-g-DMAEMA-OB were blocked, while PES-g-DMAEMA-DB and PES-g-DMAEMA-HB were retained. We supposed that DMAEMA-BB and DMAEMA-OB aggregated on the membrane surface due to the activities of intermolecular or intramolecular hydrogen bonds. Bacteria testing found the antibacterial activities of the membranes increased with the length of the substituted alkyl chain. Correspondingly, little bacteria were observed on PES-g-DMAEMA-DB and PES-g-DMAEMA-HB by SEM. The antifouling properties were investigated by filtration of a solution of Escherichia coli. Compared with the initial membrane, PES-g-DMAEMA-DB and PES-g-DMAEMA-HB showed excellent anti-biofouling performance with higher relative flux recovery (RFR) of 88.3% and 92.7%, respectively. Thus, surface functionalization of the PES membrane with QACs can prevent bacteria adhesion and improve the anti-biofouling activity by the contact-active antibacterial property.

Increment of the FRET efficiency between carbon dots and photosensitizers for enhanced photodynamic therapy

Mg/N double-doped carbon dots (CDs) with a quantum yield up to 84.6% were synthesized by a one-step hydrothermal method, and the as-prepared CDs were then successfully used as carriers for an insoluble photosensitizer (chlorin e6, Ce6). Besides the high fluorescence quantum yield of the CDs, the short donor–acceptor distance and excessive acceptors per donor of the designed CDs–Ce6 system contributed to the high fluorescence resonance energy transfer (FRET) efficiency (up to 84%) and final enhanced photodynamic reaction. The CDs–Ce6 system showed excellent hydrophilicity and particularly tunable FRET efficiency. Its singlet oxygen (SO) quantum yield was double that of pure Ce6, and a significant photodynamic therapy (PDT) effect was proven on HepG2 cancer cells.

Effect of Additives on Characteristics of Poly(3-Hydroxybutyrate) Microspheres

Poly(3-hydroxybutyrate) (PHB) based microspheres were prepared via double emulsion solvent evaporation using polyethylene glycol (PEG), poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV), polylactide (PLA), poly(dl-lactic-co-glycolic acid) (PLGA) or chitosan (CTS) as the additive of wall polymers. It was found that additives had distinct effect on the properties of microspheres, such as the yield, drug loading, average diameter, crystallization states microstructure and surface morphological characters. PHB based microspheres using PEG as the additive had the lowest yield, the smallest average diameter, and the highest drug loading which reached 12.2% thereinto. At the same time it had the lowest crystallinity of PHB, and the diameter of the crystal particles was only 11.44 nm. It was feasible to prepare PHB based microspheres using PEG and PHBV as additives, which had relatively high protein loading but different microstructures and surface morphologies, and they were anticipated to have a good effect of controlled release.

A rapid hemostatic sponge based on large, mesoporous silica nanoparticles and N-alkylated chitosan

Rapid bleeding control is increasingly important in current civilian and military emergency medicine, but the rapid hemostasis achieved with current hemostatic products is often unsafe. In this study, mesoporous silica nanoparticles (MSNs) with large pores were coordinated with a glycerol-modified N-alkylated chitosan sponge (GACS) to develop a rapid and safe hemostatic sponge. Due to its coagulation-promoting structure, MSN-GACS exhibited unique hemostatic potency in serial in vitro coagulation tests. In addition to enhanced platelet adhesion and whole blood absorption, MSN-GACS exhibited better biocompatibility than Combat Gauze (CG), which is popular in the US military. Furthermore, in rabbit femoral artery and liver injury in vivo models, MSN-GACS showed better hemostatic efficiency and lower cardiovascular toxicity than CG. In conclusion, MSN-GACS is an excellent prehospital hemostatic agent for first-aid applications.

Bioluminescence-initiated photodynamic therapy bridged on high-luminescent carbon dots-conjugated protoporphyrin IX

Various external lights and improved illumination methods, such as near-infrared light, X-ray, and two-photon excitation, have been tried to enhance the efficiency of photodynamic therapy (PDT) in deep-seated tumors. However, the penetration depth of light required for photosensitizers’ (PSs) activation still remains a major problem in clinic. Herein, bioluminescence (BLS), a kind of inner light induced from the firefly luciferase, is attempted to activate the treatment in deep lesions. To obtain a better therapeutic effect, carbon dots (CDs) with an excitation-independent photoluminescence are prepared by a facile hydrothermal method, and the as-prepared CDs are designed to conjugate protoporphyrin IX (PIX) to construct the PDT agents (CDs-PIX). Results indicate the nano-carrier of CDs enhances the limitations of PIX and bridges the excitation between BLS and PIX. The BLS-induced PDT system can produce the singlet oxygen and provide a certain efficient therapy (about 60%) in SMMC-7721 hepatocellular carcinoma cells through fluorescence resonance energy transfer (FRET) process, which demonstrates the firefly BLS has already functioned in some extent, but not perfect. CDs-PIX is an excellent PS for PDT applications, but its corresponding excitation inner light source needs further studies.