Junfeng Hui

PEGylation of fluoridated hydroxyapatite (FAp):Ln3+ nanorods for cell imaging

PEGylation is a popular approach for the surface functionalization of nanoparticles to achieve improved properties and better performance. Herein, we developed a facile method for surface PEGylation of hydrophobic fluoridated hydroxyapatite (FAp):Ln3+ (Ln = Eu or Tb) nanorods via hydrophobic interactions between oleic acid and amphiphilic synthetic copolymers, which were synthesized through reversible addition-fragmentation chain transfer (RAFT) polymerization using stearyl methacrylate (SMA) and poly(ethylene glycol) methacrylate (PEGMA) as monomers. Our results demonstrated that the morphology and fluorescent properties of the FAp nanorods are not significantly changed by the PEGylation procedure, and the resulting FAp nanorods were found to be stable in aqueous solution. More importantly, these PEGylated FAp nanorods are biocompatible with cells and could be utilized for cell imaging applications. Therefore, we believe that the method described in this work is a simple, efficient and general strategy for the surface PEGylation of hydrophobic nanoparticles.

Human-like collagen/nano-hydroxyapatite scaffolds for the culture of chondrocytes

Three dimensional (3D) biodegradable porous scaffolds play a key role in cartilage tissue repair. Freeze-drying and cross-linking techniques were used to fabricate a 3D composite scaffold that combined the excellent biological characteristics of human-like collagen (HLC) and the outstanding mechanical properties of nano-hydroxyapatite (nHA). The scaffolds were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and compression tests, using Relive® Artificial Bone (RAB) scaffolds as a control. HLC/nHA scaffolds displayed homogeneous interconnected macroporous structure and could withstand a compression stress of 2.67 ± 0.37 MPa, which was higher than that of the control group. Rabbit chondrocytes were seeded on the composite porous scaffolds and cultured for 21 days. Cell/scaffold constructs were examined using SEM, histological procedures, and biochemical assays for cell proliferation and the production of glycosaminoglycans (GAGs). The results indicated that HLC/nHA porous scaffolds were capable of encouraging cell adhesion, homogeneous distribution and abundant GAG synthesis, and maintaining natural chondrocyte morphology compared to RAB scaffolds. In conclusion, the presented data warrants the further exploration of HLC/nHA scaffolds as a potential biomimetic platform for chondrocytes in cartilage tissue engineering.

Synthesis and characterization of hyaluronic acid/human-like collagen hydrogels

Injectable hydrogel plays an important role in soft tissue filling and repair. We report an injectable hydrogel based on hyaluronic acid (HA) and human-like collagen (HLC), both with favorable biocompatibility and biodegradability. These two types of biomacromolecules were crosslinked with 1,4-butanediol diglycidyl ether to form a three-dimensional network. The redundant crosslinker was removed by dialysis and distillation. An HA-based hydrogel prepared by the same method was used as a control. The cytocompatibility was studied with a Cell Counting Kit-8 (CCK-8) test. Carbazole colorimetry was used to analyze the in vitro degradation rate. The histocompatibility was evaluated by hematoxylin and eosin (H&E) staining analysis and immunohistochemical analysis. The CCK-8 assay demonstrated that the HA/HLC hydrogel was less cytotoxic than the HA-based hydrogel and could promote baby hamster kidney cell (BHK) proliferation. The cell adhesion indicated that BHK could grow well on the surface of the materials and maintain good cell viability. The in vitro degradation test showed that the HA/HLC hydrogel had a longer degradation time and an excellent antienzyme ability. In vivo injection showed that there was little inflammatory response to HA/HLC after 1, 2, and 4 weeks. Therefore, the HA/HLC hydrogel is a promising biomaterial for soft tissue filling and repair.

Surface grafting of Eu 3 + doped luminescent hydroxyapatite nanomaterials through metal free light initiated atom transfer radical polymerization for theranostic applications

We reported a simple and efficient method to prepare the hydrophilic luminescent HAp polymer nanocomposites through the combination of ligand exchange and metal free light initiated surface-initiated atom transfer radical polymerization (SI-ATRP) using 10-phenylphenothiazine (PTH) as organic catalyst and 2-methacryloyloxyethyl phosphorylcholine (MPC) and itaconic acid (IA) as monomers. The biological imaging and drug delivery performance of HAp-poly(MPC-IA) nanorods were examined to evaluate their potential for biomedical applications. Results suggested that hydrophilic HAp-poly(MPC-IA) nanorods can be successfully prepared. More importantly, the HAp-poly(MPC-IA) exhibited excellent water dispersibility, desirable biocompatibility and good performance for biological imaging and controlled drug delivery applications. As compared with other controlled living polymerization reactions, the metal free light initiated SI-ATRP displayed many advantages such as easy for handle, mild reaction conditions, toxicity and fluorescence quenching from metal catalysts. Therefore, we believe that this strategy should be a useful and effective strategy for preparation of HAp nanomaterials for biomedical applications.

Fabrication of silica nanoparticle based polymer nanocomposites via a combination of mussel inspired chemistry and SET-LRP

A highly benign, simple and effective strategy was successfully developed for the first time for the fabrication of hydrophilic thermo-responsive polymer modified silica nanoparticles (SiO2-PDA-poly(NIPAM)) at low temperature and under mild reaction conditions via a combination of mussel inspired chemistry and SET-LRP. The SiO2 NPs were first modified with polydopamine (PDA), which was formed by the self-polymerization of dopamine under rather mild conditions. 2-Bromo-2-methylpropionyl bromide was covalently attached on the surface of the PDA modified SiO2 NPs. Afterward, the poly(NIPAM) was grown in situ on the surface of the Br-containing SiO2 NPs by the SET-LRP method. Consequently, the surface of the SiO2-PDA nanoparticles is intrinsically covered by a layer of free poly(NIPAM) chains, which enables the poly(NIPAM) to be colloidally stable not only at room temperature, but also upon incubation in the presence of proteins under physiological conditions. After modifying with PNIPAM, the functional SiO2 NPs retain their pristine structure, however their dispersibility was significantly improved in polar and nonpolar solutions. As compared with previous methods, the strategy developed in this work is rather simple and effective. More importantly, due to the universality of mussel inspired chemistry, this novel strategy could also be used for the surface modification of many other materials.

A novel chitosan–collagen-based hydrogel for use as a dermal filler: initial in vitro and in vivo investigations

Novel hydrogels (termed HCD hydrogels) were synthesized based on human-like collagen (HLC) and chitosan (CS) cross-linked with dialdehyde starch (DAS). The biological stability and biocompatibility of HCD hydrogels were determined through in vitro and in vivo tests. The mechanism of hydrogel formation was studied using Fourier transform infrared spectroscopy (FTIR), which showed that covalent bonds formed via acetalization and Schiff base reactions. Biological stability was evaluated in vitro by degrading HCD hydrogels with class I collagenase, class II collagenase, and both class I and class II collagenases and in vivo after subcutaneously injecting HCD into an animal model. The biological characteristics of HCD hydrogels was studied by two methods: (i) MTT and cytomorphology cytotoxicity and cytocompatibility and (ii) in vivo, whereby histomorphometry, transmission electron microscopy (TEM), and immunohistochemistry were used to compare different types of surgically introduced hydrogels, our HCD hydrogels, SunMax Collagen Implant hydrogels (SUM hydrogels), and OUTLINE&EVOLUTION Injectable Synthetic Gel hydrogels (EVL hydrogels). The in vivo analyses were performed at 1, 9, 12, and 28 weeks after surgery. The hydrogel biodegradation results showed that the normalized residual weight (WR) of HCD hydrogels varied with DAS content. In vitro, we found that the minimum WR of HCD hydrogels was 42.19% after 28 weeks when degraded by both types of class I and class II collagenase. The MTT assay indicated that the minimum relative growth rate (RGR) of cells was 93% after they were incubated with HCD hydrogels for 7 days, suggesting good cytocompatibility. In vivo histomorphometry results indicated that HCD hydrogels effectively filled tissue voids and did not cause redness, edema, festering, or color changes. In addition, a few vessels grew into the hydrogel and a thin fibrous capsule was eventually produced. TEM and immunohistochemistry studies suggested that HCD hydrogels produced less intense inflammatory responses than those produced by SUM hydrogels and EVL hydrogels. Overall, HCD hydrogels afford both enhanced biological stability and excellent biocompatibility, making them potentially promising for skin patch scaffolds, wrinkle treatments, and tissue cavity fillers.

Monodisperse selenium-substituted hydroxyapatite: Controllable synthesis and biocompatibility

Hydroxyapatite (HA) is the major inorganic component of natural bone tissue. As an essential trace element, selenium involves in antioxidation and anticancer of human body. So far, ion-doped hydroxyapatites (HAs) are widely investigated owing to their great applications in field of biomaterial, biological labeling. In this paper, series of monodisperse HA doped with SeO32- (SeHA) was successfully synthesized based on the liquid-solid-solution (LSS) strategy. The obtained samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and energy-dispersive spectrometer (EDS). The results indicated that the SeO32- doping level of the Se/(P+Se) molar ratio of 0-0.4 can be requisitely controlled, and the morphology of SeHA nanoparticles varied from nanorods to nanoneedles with increasing Se/(P+Se) molar ratio. Significantly, the as-synthesized SeHA nanocrystals exhibit a low cytotoxicity for osteoblastic cells, showing exciting potentials for application in artificial scaffold materials inhibiting of tumor growth in bone.

Protopanaxadiol and Protopanaxatriol-Type Saponins Ameliorate Glucose and Lipid Metabolism in Type 2 Diabetes Mellitus in High-Fat Diet/Streptozocin-Induced Mice

Ginsenoside is a major active component of ginseng, which exhibits various pharmacological properties such as hepatoprotection, tumor suppression and diabetes resistance. In this study, the anti-diabetic effects of protopanaxadiol (PPD) and protopanaxatriol (PPT)-type saponins were explored and compared in high-fat diet/streptozocin-induced type 2 diabetes mellitus (T2DM) mice. Our results showed that low or high dose (50 mg/kg bodyweight or 150 mg/kg bodyweight) PPD and PPT significantly reduced fasting blood glucose, improved glucose tolerance and insulin resistance in T2DM mice. PPD and PPT also regulated serum lipid-related markers such as reduced total cholesterol (TC), triglyceride (TG), and low-density lipoprotein cholesterol in T2DM mice. In addition, PPD and PPT dramatically ameliorated the inflammatory responses by suppressing the secretion of pro-inflammatory cytokines like tumor necrosis factor-alpha and interleukin-6 in serum level and gene expression in liver level, and improved the antioxidant capacity by increasing the superoxide dismutase and decreasing malondialdehyde levels in the serum of T2DM mice. Moreover, the anti-diabetic effect of PPD and PPT appeared to be partially mediated by the suppression of hepatic metabolism genes expression such as peroxisome proliferator-activated receptor gamma coactivator 1-alpha, phosphoenolpyruvate carboxykinase, and glucose-6-phosphatase, as well as facilitating lipid metabolism genes expression such as microsomal TG transfer protein in the liver tissues of T2DM mice. Taken together, our results indicated that PPD and PPT might potentially act as natural anti-diabetic compounds to be used for preventing and treating the T2DM and its complications in the future.

Novel Scaffolds Fabricated Using Oleuropein for Bone Tissue Engineering

We investigated the feasibility of oleuropein as a cross-linking agent for fabricating three-dimensional (3D) porous composite scaffolds for bone tissue engineering. Human-like collagen (HLC) and nanohydroxyapatite (n-HAp) were used to fabricate the composite scaffold by way of cross-linking. The mechanical tests revealed superior properties for the cross-linked scaffolds compared to the uncross-linked scaffolds. The as-obtained composite scaffold had a 3D porous structure with pores ranging from 120 to 300 μm and a porosity of 73.6 ± 2.3%. The cross-linked scaffolds were seeded with MC3T3-E1 Subclone 14 mouse osteoblasts. Fluorescence staining, the Cell Counting Kit-8 (CCK-8) assay, and scanning electron microscopy (SEM) indicated that the scaffolds enhanced cell adhesion and proliferation. Our results indicate the potential of these scaffolds for bone tissue engineering.

Optimizing the Chemical Compositions of Protective Agents for Freeze-drying Bifidobacterium longum BIOMA 5920

Abstract Freeze drying has a deleterious effect on the viability of microorganisms. In front of this difficulty, the present study adopts response surface methodology to optimize the chemical compositions of protective agents to seek for maximum viability of Bifidobacterium longum BIOMA 5920 during freeze-drying. Through the comparative analysis of single protectant, the complex protective agents show better effect on the Bifidobacterium viability. Human-like collagen (HLC), trehalose and glycerol are confirmed as significant factors by Box-Behnken Design. The optimized formula for these three variables is tested as follows: HLC 1.23%, trehalose 11.50% and glycerol 4.65%. Under this formula, the viability is 88.23%, 39.67% higher in comparison to the control. The viable count is 1.07×10 9 cfu·g −1 , greatly exceeding the minimum viable count requirement (10 6 cfu·g −1 ).