[Application of hyaluronic acid microneedles in insulin intelligent delivery system for the treatment of diabetes].

In this study, insulin (insulin, INS)/Ca3PO4 complex and glucose oxidase (glucose oxidase, GOx)/Cu3(PO4)2 complex were prepared by coprecipitation method. The mineralized insulin (mineralized insulin, m-INS) showed irregular crystalline clusters, and the mineralized glucose oxidase (m-GOx) showed flower spherical morphology, with a diameter of about 1-2 µm. In vitro simulated release experiment showed that m-INS released INS as the pH value of the medium decreased. When the pH value was 4.5, the release amount reached 96.68%. The enzyme activity detection experiment showed that the enzyme activity stability of m-GOx was higher than that of free GOx. It still maintained high activity after 10 days at room temperature, while the activity of GOx was less than 60%. The glucose solution was prepared to simulate the state of normal blood glucose (5.6 mmol/L) and hyperglycemia (22.2 mmol/L). When m-INS and m-GOx were added to the glucose solution, the release amount of INS showed a significant glucose concentration dependence. The higher the glucose concentration, the greater the release amount and release rate of INS. Finally, m-INS, m-GOx and hyaluronic acid (HA) solution were mixed to prepare HA microneedle arrays loaded with m-INS and m-GOx. Type 1 diabetes mice were constructed to evaluate the effect of drug-loaded HA microarray on blood glucose control in diabetic rats. The results show that the HA microneedles loaded with m-INS/m-GOx could deliver drugs effectively. The average blood glucose concentration in diabetic rats dropped to about 7 mmol/L within 1 h, normal blood glucose concentration could be maintained for 10 h, and the overall blood glucose concentration was lower than the level before administration for 36 hours. Compared with HA microneedles loaded with INS only, m-ins microneedles showed better glucose tolerance, longer-lasting glucose control effect and less risk of hypoglycemia. Compared with other sustained-release systems, the preparation process of the core components in this study is simple, efficient, safe and effective, and has great commercial potential.

Arginine-glycine-aspartate (RGD)-targeted positron-labeled dendritic polylysine nanoprobe for tumor PET imaging.

This work investigated the optimization of the 68Ga radiolabeling of the dendritic polylysine-1,4,7-triazacyclononane-1,4,7-triacetic acid conjugate (DGL-NOTA). Under pH = 4.0, reaction temperature of 70 °C, and incubation time of 10.0 min, the conjugate (DGL-NOTA) radiochemical yield was between 50% and 70%. After separation and purification, the radiochemical purity was greater than 98%. The radiolabeled formulation (68Ga-NOTA-DGL-PEG-RGDyC) remained stable in both phosphate buffer and serum (all radiochemically greater than 95%) for up to 2 hours with a specific activity of 30 GBq/µmol. Cellular experimental studies have shown that radiolabeled preparations can rapidly enter U87MG cells, and after 2 hours, there was still retention of imaging agents in the cells. In vivo distribution studies had shown that the tracer is excreted by the kidneys. Two hours after injecting the imaging agent, the U87MG tumor tissue uptake value was (4.67 ± 0.09)% ID/g. Positron emission tomography (PET) imaging in animals showed that 68Ga-NOTA-DGL-PEG-RGDyC had good targeting and can be enriched in tumor sites. Through hemolysis testing and morphological changes of red blood cells, it was proved that NOTA-DGL-PEG-RGDyC has good blood compatibility.

Sgc8 aptamer targeted glutathione-responsive nanoassemblies containing Ara-C prodrug for the treatment of acute lymphoblastic leukemia.

Cytarabine (Ara-C) is an essential medicine used in the clinical treatment of acute lymphoblastic leukemia. However, Ara-C suffers from high hydrophilicity, rapid plasma degradation and significant side effects. Thus, herein, to eliminate the limitations of Ara-C in the treatment of leukemia, Sgc8 aptamer targeting and glutathione (GSH)-responsive polymeric micelles (PCL-ss-Ara@Sgc8-BSA) were prepared. The prodrug was synthesized via covalent bond formation between acryloyl chloride-terminal PCL-ss-PCL and Ara-C, and surface decoration with Sgc8-bovine serum albumin (Sgc8-BSA). The obtained PCL-ss-Ara@Sgc8-BSA exhibited good GSH-responsive drug release behavior, obvious targetability and sufficient antitumor effect to acute lymphoblastic leukemia (ALL) cells (CCRF-CEM). A hemolysis test was further carried out to demonstrate that these polymeric micelles are safe to be administrated intravenously. Compared with free Ara-C, PCL-ss-Ara@Sgc8-BSA significantly enhanced tumor growth inhibition in mice bearing CCRF-CEM xenograft tumors, while causing little side effects, and improved the survival rate of CCRF-CEM tumor-bearing mice in vivo. Therefore, this new self-assembling small molecular prodrug equipped with Sgc8 targeting function is a potential treatment for the targeted therapy of acute lymphoblastic leukemia.

RGD/TAT-functionalized chitosan-graft-PEI-PEG gene nanovector for sustained delivery of NT-3 for potential application in neural regeneration.

In this study, we prepared a multifunctional gene delivery nanovector containing a chitosan (CS) backbone and polyethylenimine (PEI) arms with arginine-glycine-aspartate (RGD)/twin-arginine translocation (TAT) conjugated via polyethylene glycol (PEG). Branched PEI, with a molecular weight of 2000 Da, was used to achieve a balance between biocompatibility and transfection efficiency, whereas RGD/TAT peptides were conjugated for enhanced targeting ability and cellular uptake. Synthesis of the copolymers was confirmed by characterizing the chemical structure with 1H nuclear magnetic resonance and Fourier Transform Infrared Spectroscopy (FTIR). The nanovector was biocompatible with cells and showed excellent capability for DNA condensation; the resulting complexes with DNA were well-formed, and possessed small particle size and reasonable positive charge. Higher gene transfection efficiency, compared to that achieved with PEI (25 kDa), was confirmed in tumor (HeLa cells) and normal cells (293T and NIH 3T3 cells). More importantly, the cells transfected with the chitosan-graft-PEI-PEG/pCMV-EGFP-Ntf3 complex produced sustained neurotrophin-3 with a linear increase in cumulative concentration, which induced neuronal differentiation of neural stem cell and promoted neurite outgrowth. These findings suggested that our multifunctional copolymers might be ideal nanovectors for engineering cells via gene transfection, and could potentially be applied in tumor therapy and regenerative medicine. STATEMENT OF SIGNIFICANCE: We successfully prepared a multifunctional gene delivery nanovector containing branched PEI with a molecular weight of 2000 Da to balance between biocompatibility and transfection efficiency, and RGD/TAT peptides for enhanced targeting ability and cellular uptake. The well-formed CPPP/DNA complexes of small particle size and reasonable positive charges potentially enhanced gene transfection in both tumor and normal cells. More importantly, the CPPP/pCMV-EGFP-Ntf3 complex-transfected 293T cells could produce sustained NT-3 with a constant ratio, which induced neuron differentiation of NSC and promoted neurite outgrowth. Therefore, our study provided an effective strategy for producing neurotrophins by engineering cells with gene delivery, which deserved wide investigation and potential application in regenerative medicine.

Dual responsive zein hydrogel membrane with selective protein adsorption and sustained release property.

Drug-loaded hydrogels have been paid increasing attentions in biomedical fields. As a sort of natural plant protein, zein generally cannot form hydrogel with high water retention because of its predominant hydrophobicity, which will limit its application as biomaterial. In this paper, zein electrospun fibrous membranes (ZEFM) are fabricated through a chemical modification of zein using citric acid and acetic anhydride. The resulting ZEFM can be totally soluble in neutral phosphate buffer solution. After being crosslinked by sodium hexametaphosphate, the ZEFM can form a hydrogel membrane and displays stimuli-responsive behavior towards pH and ionic strength. The hydrogel membrane exhibits better protein adsorption, selectivity and sustained release profile for positively-charged proteins such as cytochrome C, compared with those unmodified ones, and also shows fast biodegradation behavior and qualified cytotoxicity, which all make it favourable for biomedical use.

Coaxial electrospun zein nanofibrous membrane for sustained release.

Zein nanofibrous membranes for sustained release have been prepared by coaxial electrospinning. Core-sheath structure has been successfully fabricated using zein as both the core and sheath component. Impact of solvent and solution concentration on the morphology of the resulting fibers was investigated. Allyltriphenylphosphonium bromide was used as a model drug to test the sustained release effect. The sustained release profile and the antimicrobial activity of the resulting membranes were investigated and compared with that of the single fluid electrospinning of zein/drug blended membrane. The ratio of the inner and outer feeding rates was found to influence the encapsulation of drugs, and in turn affect the sustained release effect of the resulting membranes. The coaxial electrospinning membrane can remarkably suppress the initial burst release of drugs by giving a releasing amount of 15% in the first 1 h when the inner/outer ratio was larger than 1:2. This drug-loaded zein membrane with preferable sustained release effect can be applied in many fields such as wound healing and packaging sector.

A novel route for the production of chitosan/poly(lactide-co-glycolide) graft copolymers for electrospinning.

Both chitosan and polylactide/polyglycolide have good biocompatibility and can be used to produce tissue engineering scaffolds for cultured cells. However the synthetic scaffolds lack groups that would facilitate their modification, whereas chitosan has extensive active amide and hydroxyl groups which would allow it to be subsequently modified for the attachment of peptides, proteins and drugs. Also chitosan is very hydrophilic, whereas PLGA is relatively hydrophobic. Accordingly there are many situations where it would be ideal to have a copolymer of both, especially one that could be electrospun to provide a versatile range of scaffolds for tissue engineering. Our aim was to develop a novel route of chitosan-g-PLGA preparation and evaluate the copolymers in terms of their chemical characterization, their performance on electrospinning and their ability to support the culture of fibroblasts as an initial biological evaluation of these scaffolds. Chitosan was first modified with trimethylsilyl chloride, and catalyzed by dimethylamino pyridine. PLGA-grafted chitosan copolymers were prepared by reaction with end-carboxyl PLGA (PLGA-COOH). FT-IR and(1)H-NMR characterized the copolymer molecular structure as being substantially different to that of the chitosan or PLGA on their own. Elemental analysis showed an average 18 pyranose unit intervals when PLGA-COOH was grafted into the chitosan molecular chain. Differential scanning calorimetry results showed that the copolymers had different thermal properties from PLGA and chitosan respectively. Contact angle measurements demonstrated that copolymers became more hydrophilic than PLGA. The chitosan-g-PLGA copolymers were electrospun to produce either nano- or microfibers as desired. A 3D fibrous scaffold of the copolymers gave good fibroblast adhesion and proliferation which did not differ significantly from the performance of the cells on the chitosan or PLGA electrospun scaffolds. In summary this work presents a methodology for making a hybrid material of natural and synthetic polymers which can be electrospun and reacts well as a substrate for cell culture.

[Preparation and biocompatibility evaluation of osteochondral composite scaffold].

OBJECTIVE: To prepare osteochondral composite scaffold and study its biocompatibility in vitro. METHODS: The composite material of nano-HAP/collagen I was prepared, and the osteochondral scaffold was manufactured by combining nano-HAP, collagen I, and PLGA as the bone section and sodium hyaluronate and PLGA as the chondral section. The diameter, chemical composition and crystallinity of the nano-HAP/collagen I composite particles were assessed with TEM, FTIR and XRD, and the biocompatibility and cytotoxicity of the scaffold were evaluated using MTT assay by co-culturing bone marrow stem cells and the scaffold. RESULTS AND CONCLUSION: The osteochondral composite scaffold has good microstructure without obvious cytotoxicity, possesses good biocompatibility with bone marrow stem cells and is suitable as an osteochondral scaffold material.

Bis[dieth-yl(hy-droxy)ammonium] benzene-1,4-dicarboxyl-ate.

In the centrosymmetric title compound, 2C(4)H(12)NO(+)·C(8)H(4)O(4) (2-), two N,N-dieth-yl(hy-droxy)ammonium cations are linked to a benzene-1,4-dicarboxyl-ate dianion by a combination of O-H⋯O and N-H⋯O hydrogen bonds, which can be described in graph-set terminology as R(2) (2)(7). The crystal structure is further stabilized by C-H⋯O hydrogen bonds, leading to the fomation of a ribbon-like network.

[Effect of bone morphogenetic protein microspheres on biological behavior of rabbit bone marrow stem cells].

OBJECTIVE: To evaluate the effect of bone morphogenetic protein (BMP) on the biological behavior of bone marrow stem cells (BMSCs) of rabbits. METHODS: BMP was either enwrapped or not in the microspheres made of chitosan and sodium alginate, and the biocompatibilities of the composites were examined by means of cell culture. The BMSCs were cultured with the two kinds of microspheres respectively, and the cell extension rate, proliferation, alkaline phosphatase activity and Coomassie blue staining of the cells were assayed. RESULTS: Inhibition of BMSC proliferation did not occur in response to in vitro culture with the microspheres, but alkaline phosphatase activity and D(lambda) values of Coomassie blue staining increased significantly in the cells cultured with BMP microspheres. CONCLUSION: BMP can increase the osteogenic capacity of BMSCs in vitro with the microspheres made of chitosan and sodium alginate as the carrier.

[Current researches in keratoprosthesis].

This paper introduced the evolution of keratoprosthesis (KPs) from the earliest devices to the newly developed types, pointed out their drawbacks and discussed the properties that an ideal keratoprosthesis or a tissue engineering keratoprosthesis must possess. Recent researches focused on the use of porous polymers as the skirt of core-skirt keratoprosthesis and tried to improve the material's biologicial intergration.