Hua Hong

Preparation and characterization of bioactive mesoporous wollastonite – Polycaprolactone composite scaffold

A well-defined mesoporous structure of wollastonite with high specific surface area was synthesized using surfactant P123 (triblock copolymer) as template, and its composite scaffolds with poly(epsilon-caprolactone) (PCL) were fabricated by a simple method of solvent casting-particulate leaching. The measurements of the water contact angles suggest that the incorporation of either mesoporous wollastonite (m-WS) or conventional wollastonite (c-WS) into PCL could improve the hydrophilicity of the composites, and the former was more effective than the later. The bioactivity of the composite scaffold was evaluated by soaking the scaffolds in a simulated body fluid (SBF) and the results show that the m-WS/PCL composite (m-WPC) scaffolds can induce a dense and continuous layer of apatite after soaking for 1 week, as compared with the scattered and discrete apatite particles on the c-WS/PCL composite (c-WPC) scaffolds. The m-WPC had a significantly enhanced apatite-forming bioactivity compared with the c-WPC owing to the high specific surface area and pore volume of m-WS. In addition, attachment and proliferation of MG(63) cells on m-WPC scaffolds were significantly higher than that of c-WPC, revealing that m-WPC scaffolds had excellent biocompatibility. Such improved properties of m-WPC should be helpful for developing new biomaterials and may have potential use in hard tissue repair.

Self-setting bioactive calcium-magnesium phosphate cement with high strength and degradability for bone regeneration.

Calcium phosphate cement (CPC) has been successfully used in clinics as bone repair biomaterial for many years. However, poor mechanical properties and a low biodegradation rate limit any further applications. Magnesium phosphate cement (MPC) is characterized by fast setting, high initial strength and relatively rapid degradation in vivo. In this study, MPC was combined with CPC to develop novel calcium-magnesium phosphate cement (CMPC). The setting time, compressive strength, phase composition of hardened cement, degradation in vitro, cells responses in vitro by MG-63 cell culture and tissue responses in vivo by implantation of CMPC in bone defect of rabbits were investigated. The results show that CMPC has a shorter setting time and markedly better mechanical properties than either CPC or MPC. Moreover, CMPC showed significantly improved degradability compared to CPC in simulated body fluid. Cell culture results indicate that CMPC is biocompatible and could support cell attachment and proliferation. To investigate the in vivo biocompatibility and osteogenesis, the CMPC samples were implanted into bone defects in rabbits. Histological evaluation showed that the introduction of MPC into CPC enhanced the efficiency of new bone formation. CMPC also exhibited good biocompatibility, biodegradability and osteoconductivity with host bone in vivo. The results obtained suggest that CMPC, having met the basic requirements of bone tissue engineering, might have a significant clinical advantage over CPC, and may have the potential to be applied in orthopedic, reconstructive and maxillofacial surgery.

Degradable, antibacterial silver exchanged mesoporous silica spheres for hemorrhage control

Effective hemorrhage control becomes increasingly significant in todays military and civilian trauma, and current available local hemostatic agents have been reported to have various drawbacks and side effects. Herein in this study, a silver exchanged calcium doped ordered mesoporous silica sphere (AgCaMSS) with good degradability and antibacterial properties was developed for hemorrhage control. The well-ordered and symmetry hexagonal AgCaMSS with pore size of 3.2 nm, BET surface area of 919 m(2)/g and pore volume of 0.74 m(3)/g was prepared by one-step based catalyzed self-assembly and subsequent ion-exchange procedures. The degradation behaviors in Tris-HCl solution indicated that the addition of calcium and silver facilitated the dissolution and the weight loss of the prepared AgCaMSS could attain more than 40% after 42 days. The results obtained demonstrated that the optimal AgCaMSS formulation could significantly promote the blood clotting, activate the intrinsic pathway of coagulation cascade, induce platelet adherence. Consequently, effective hemostasis with low exothermic effects was achieved and the mortalities in femoral artery and liver injury models were reduced. The antibacterial experiment using broth culture method revealed that the prepared AgCaMSS had better antibacterial activities against Escherichia coli and Staphylococcus aureus. Based on these results, it can be concluded that the AgCaMSS developed here would be a promising material platform for designing hemostats in more extensive clinical application.

Molecular imprinted macroporous chitosan coated mesoporous silica xerogels for hemorrhage control.

Efficacious hemostatic agents have significant potential for use in rapid exsanguinating hemorrhage control by emergency medical technician or military medic nowadays. Unfortunately, the topical hemostats currently available in market still have various disadvantages. In this study, a series of macroporous chitosan coated mesoporous silica xerogel beads (CSSX) with good biocompatibility were developed. They consisted of mesoporous silica xerogel cores and chitosan layers with macroporous structure by using modified sol-gel process and PEG molecular imprinting technique. The textural properties of the CSSX beads were optimized by in vitro and in vivo evaluation for promoting blood clotting and the results indicated that the prepared CSSX beads can significantly accelerate the contact activation pathway of coagulation cascade and produce desirable hemostasis, with the best efficiency from the CSSX prepared with 2% chitosan and 5% PEG. Furthermore, these CSSX beads were observed to create no exothermic reaction and the subsequential tissue thermal injury by histological examination, and exhibited no obvious cytotoxicity even after 7 days. The results of the present study forward CSSX bead as a safe hemostatic system and present a platform for further optimization studies of materials with enhanced hemostatic capabilities for specific injury types.

Preferential tumor accumulation and desirable interstitial penetration of poly(lactic-co-glycolic acid) nanoparticles with dual coating of chitosan oligosaccharide and polyethylene glycol-poly(D,L-lactic acid).

UNLABELLED Despite advances in polymeric nanoparticles (NPs) as effective delivery systems for anticancer drugs, rapid clearance from blood and poor penetration capacity in heterogeneous tumors still remain to be addressed. Here, a dual coating of poly (ethylene glycol)-poly (d,l-lactic acid) (PEG-PDLLA) and water-soluble chitosan oligosaccharide (CO) was used to develop PLGA-based NPs (PCPNPs) with colloidal stability for delivery of paclitaxel (PTX). The PCPNPs were prepared by a modified nanoprecipitation process and exhibited homogeneous size of 165.5nm, and slight positive charge (+3.54mV). The single PEG-PDLLA-coated PLGA NPs (PPNPs) with negative charge (-13.42mV) were prepared as control. Human breast cancer MDA-MB-231 cell and mice MDA-MB-231 xenograft model were used for in vitro and in vivo evaluation. Compared to Taxol®, both PCPNPs and PPNPs increased the intracellular uptake and exerted stronger inhibitory effect on tumor cells in vitro, especially for PCPNPs. Particularly, due to the near neutral surface charge and shielding by the dual coating, the blank cationic NP presented low cytotoxicity. With the synergistic action of PEG-PDLLA and CO, PCPNPs not only strongly inhibited macrophage uptake and extended the blood circulation time, but also improved the selective accumulation and interstitial penetration capacity to/in tumor site. Consequently, a significantly enhanced antitumor efficacy was observed for the cationic PCPNPs. Our findings suggest that, the dual PEG-PDLLA/CO coating can effective improve the tumor accumulation and interstitial penetration of NPs and, therefore may have great potential for tumor treatment. STATEMENT OF SIGNIFICANCE Rapid clearance from blood and poor penetration capacity in heterogeneous tumors represent great challenge for polymeric nanoparticles (NPs) as effective delivery systems for anticancer drugs. This study provides a promising cationic nanoparticle (PCPNPs) with dual coating of chitosan oligosaccharide (CO) and PEG-PDLLA to address the above problem. The PCPNPs prepared with 165.5nm and slight positive charge (+3.54mV) showed an improved accumulation and interstitial penetration capacity to/in tumor site, and thus led to an enhanced antitumor efficacy. This is the first time to report the cooperative effect of PEG-PDLLA and CO on PLGA NPs in this field. This work can arouse broad interests among researchers in the fields of nanomedicine, nanotechnology, and drug delivery system.

effect of size and processing method on the cytotoxicity of realgar nanoparticles in cancer cell lines

In this study, the effects of the size and Chinese traditional processing (including elutriation, water cleaning, acid cleaning, alkali cleaning) on realgar nanoparticles (RN)-induced antitumor activity in human osteosarcoma cell lines (MG-63) and hepatoma carcinoma cell lines (HepG-2) were investigated. The human normal liver cell line (L-02) was used as control. RN was prepared by high-energy ball milling technology. The results showed that with the assistance of sodium dodecyl sulfate, the size of realgar could be reduced to 127 nm after 12 hours’ ball milling. The surface charge was decreased from 0.83 eV to −17.85 eV and the content of As2O3 clearly increased. Except for elutriation, the processing methods did not clearly change the size of the RN, but the content of As2O3 was reduced dramatically. In vitro MTT tests indicated that in the two cancer cell lines, RN cytotoxicity was more intense than that of the coarse realgar nanoparticles, and cytotoxicity was typically time- and concentration-dependent. Also, RN cytotoxicities in the HepG-2 and L-02 cells all increased with increasing milling time. Due to the reduction of the As2O3 content, water cleaning, acid cleaning, and alkali cleaning decreased RN cytotoxicity in HepG-2, but RN after elutriation, with the lowest As2O3 (3.5 mg/g) and the smallest size (109.3 nm), showed comparable cytotoxicity in HepG-2 to RN without treatment. Meanwhile, RN-induced cytotoxicity in L-02 cells was clearly reduced. Therefore, it can be concluded that RN may provide a strong antiproliferation effect in the MG-63 and HepG-2 cells. Elutriation processing is a suitable approach to limit the dangerous side-effects of As2O3, while maintaining the effectiveness of RN.

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.

Hierarchically macroporous/mesoporous POC composite scaffolds with IBU-loaded hollow SiO2 microspheres for repairing infected bone defects

Infected bone defects are normally regarded as contraindications for bone repair. In the present study, a hollow mesoporous structure of silica (SiO2) microspheres was first synthesized and loaded with ibuprofen (IBU). Poly(1,8-octanediol-co-citrate) (POC) and β-tricalcium phosphate (β-Ca3(PO4)2, β-TCP), together with IBU-loaded SiO2 were fabricated by a 3D printing technique based on the Freeform Fabrication System with Micro-Droplet Jetting (FFS-MDJ). The physiochemical properties, compressive modulus, drug release behavior, antimicrobial properties and cell response of the composite scaffold were systematically investigated. The developed IBU-loaded SiO2/β-TCP/POC scaffolds presented a highly interconnected porous network, macropores (350-450 μm) and mesopores (3.65 nm), as well as proper compressive modulus and biocompatibility. The addition of hollow SiO2 microspheres was found to decrease the burst release and increase the cumulative release amount of IBU. In addition, IBU-loaded SiO2/β-TCP/POC showed a long-term effect on inhibiting E. coli growth by agar diffusion. The result indicated that the IBU-loaded SiO2/β-TCP/POC scaffold, with a hierarchically macro/mesoporous, highly interconnected pore structure and an effective antimicrobial property, demonstrates promise for bone regeneration in the clinical case of infected bone defects.

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.