[Study of collagen mimetic peptide's triple-helix structure and its thermostability by circular dichroism].

In the present study, the authors explore the triple-helix conformation and thermal stability of collagen mimetic peptides (CMPs) as a function of peptide sequence and/or chain length by circular dichroism(CD). Five CMPs were designed and synthetized varying the number of POG triplets or incorporating an integrin alpha2beta1 binding motif Gly-Phe-Hyp-Gly-Glu-Arg (GFOGER). CD spectroscopy from 260 to 190 nm was recorded to confirm the existence of triple-helix conformation at room temperature, while thermal melting and thermal annealing of triple-helix (thermal unfolding and refolding of triple-helix, respectively) was characterized by monitoring ellipticity at 225 nm as a function of temperature. The results demonstrated that all the CMPs adopted triple-helix conformation, and the thermal stability of the CMPs was enhanced with increasing the number of POG triplets. In contrast to natural collagen, the thermal denaturation processes of CMPs were reversible, i. e. the triple-helix unfolded upon heating while refolded upon cooling. Meanwhile, the phenomenon of "hysteresis" was observed by comparing melting and thermal curves. These findings add new insights to the mechanisms of collagen and CMPs assembly, as well as provide an alternative approach to the fabrication of artificial collagen-likes biomaterials.

Self-assembled nanoparticles of cholesterol-conjugated carboxymethyl curdlan as a novel carrier of epirubicin.

The purpose of this study was to develop nanoparticles made of cholesterol-conjugated carboxymethyl curdlan (CCMC) entrapping epirubicin (EPB) and establish their in vitro and in vivo potential. CCMC was synthesized and characterized by Fourier transform infrared spectra (FT-IR) and proton nuclear magnetic resonance spectra ((1)H NMR). The degrees of substitution (DS) of the cholesterol moiety were 2.3, 3.5 and 6.4, respectively. EPB-loaded CCMC-3.5 nanoparticles were prepared by the remote loading method. The physicochemical characteristics, drug loading efficiency and drug release kinetics of EPB-loaded CCMC-3.5 nanoparticles were characterized. The in vitro release profiles revealed that EPB release was sensitive to the pH as well as the drug loading contents. The cellular cytotoxicity and cellular uptake were accessed by using human cervical carcinoma (HeLa) cells. The EPB-loaded CCMC-3.5 nanoparticles were found to be more cytotoxic and have a broader distribution within the cells than the free EPB. The in vivo pharmacokinetics and biodistribution were investigated after intravenous injection in rats. Promisingly, a 4.0-fold increase in the mean residence time (MRT), a 4.31-fold increase in the half-life time and a 6.69-fold increase in the area under the curve (AUC 0-->infinity) of EPB were achieved for the EPB-loaded CCMC-3.5 self-assembled nanoparticles compared with the free EPB. The drug level was significantly increased in liver at 24 and 72 h; however, it decreased in heart at 8 and 24 h compared with the free EPB. The in vivo anti-tumor study indicated that the EPB-loaded CCMC-3.5 self-assembled nanoparticles showed greater anti-tumor efficacy than the free EPB. Taken together, the novel CCMC self-assembled nanoparticles might have potential application as anti-cancer drug carriers in a drug delivery system due to good results in vitro and in vivo.

Stability and in vivo evaluation of pullulan acetate as a drug nanocarrier.

To develop pullulan acetate nanoparticles (PANs) as a drug nanocarrier, pullulan acetate (PA) was synthesized and characterized. Its acetylation degree determined by the proton nuclear magnetic resonance ((1)H NMR) was 2.6. PANs were prepared by the solvent diffusion method and characterized by transmission electron microscope (TEM), size distribution, and zeta potential techniques. PANs had nearly spherical shape with a size range of 200-450 nm and low zeta potentials both in distilled water and in 10% FBS. The storage stability of PANs was observed in distilled water. PANs were stored for at least 2 months with no significant size and zeta potential changes. The safety of PANs was studied through single dose toxicity test in mice, and the result showed that PANs were well tolerated at the dose of 200 mg/kg in mice. Epirubicin-loaded PANs (PA/EPI) were also prepared and characterized in this study. Moreover, the in vivo pharmacokinetics of PA/EPI was investigated. Compared with the free EPI group, the PA/EPI group exhibited higher plasma drug concentration, longer half-life time (t(1/2)) and the larger area under the curve (AUC). All results suggested that PANs were stable, safe, and showed a promising potential on improving the bioavailability of the loaded drug of the encapsulated drug.

Preparation of folate-modified pullulan acetate nanoparticles for tumor-targeted drug delivery.

The purpose of this work was to develop a novel nano-carrier with targeting property to tumor. In this study, pullulan acetate (PA) was synthesized by the acetylation of pullulan to simplify the preparation technique of nanoparticles. Folic acid (FA) was conjugated to PA in order to improve the cancer-targeting activity. The products were characterized by proton nuclear magnetic resonance (¹H NMR) spectroscopy. Epirubicin-loaded nanoparticles were prepared by a solvent diffusion method. The loading efficiencies and EPI content increased with the amount of triethylamine (TEA) increasing in some degree. FPA nanoparticles could incorporate more epirubicin than PA nanoparticles. The folate-modified PA nanoparticles (FPA/EPI NPs) exhibited faster drug release than PA nanoparticles (PA/EPI NPs) in vitro. Confocal image analysis and flow cytometry test revealed that FPA/EPI NPs exhibited a greater extent of cellular uptake than PA/EPI NPs against KB cells over-expressing folate receptors on the surface. FPA/EPI NPs also showed higher cytotoxicity than PA/EPI NPs. The cytotoxic effect of FPA/EPI NPs to KB cells was inhibited by an excess amount of folic acid, suggesting that the binding and/or uptake were mediated by the folate receptor.

Pullulan acetate nanoparticles prepared by solvent diffusion method for epirubicin chemotherapy.

Pullulan acetate (PA) was synthesized by the reaction of pullulan with acetic anhydride in the presence of pyridine. PA was characterized by Fourier transform infrared (FT-IR) and proton nuclear magnetic resonance ((1)H NMR). A solvent diffusion method was employed in the current work to prepare PA nanoparticles. This technique had some advantages compared with other methods. The particle size increased from 185.7 nm to 423.0 nm with the degree of acetylation increasing from 2.71 to 3.0. Drug-loaded PA nanoparticles were prepared for controlled release of epirubicin (EPI). The drug entrapment and drug content increased with the degree substitution of PA increasing. EPI was released from the nanoparticles in a biphasic profile with a fast release rate in the first 10h followed by a slow release in vitro. A higher cytotoxicity against KB cells was found for EPI-loaded PA nanoparticles in comparison with free EPI. Confocal laser scanning microscopy (CLSM) observations indicate that EPI-loaded nanoparticles were internalized and released in the cytoplasmic compartment.

[Structure and degradation property of the PVA-collagen complex drug membrane].

OBJECTIVE: To investigate the structure and degradation property of the polyvinyl alcohol (PVA)-collagen complex drug membrane. METHODS: Drug collagen membrane was complexed with PVA. The physical and chemical properties of the membrane were characterized by transmission electron microscopy, scanning electron microscope, forier transform-infrared spectroscopy and differential scanning calorimetry. Degradation experiment was performed to determine the degradation property of membrane and a degradation curve was therefor drawn. RESULTS: The thermodynamic stability of collagen membrane was not destroyed by adding PVA. Collagen had good compatibility with PVA. Compared with collagen membrane, collagen-PVA complex membrane had smaller and evener pores. Adding PVA decreased the degradation rate of membrane. CONCLUSIONS: PVA-collagen membrane has better microstructure and antidegradation property than collagen membrane.

[The construction of two kinds of artificial bone and the comparison of their osteogenesis capability in vivo].

OBJECTIVE: To construct artificial bone with collagen-hydroxyapatite (HA) or collagen-HA-chondroitin sulfate (CS) as the scaffolds, and observe their biological properties. METHODS: The artificial bones were constructed by attaching recombinant human bone morphogenetic protein 2 (rhBMP-2) on those scaffolds. And then they were embedded into muscles of rats. Every weekend those newly formed bones were taken from muscles for comparing the difference in osteogenetic capability of two kinds of artificial bone in vivo. RESULTS: Both kinds of artificial bones could induce bone regeneration in muscle. The collagen-HA-CS artificial bone was superior to the collagen-HA artificial in bone-guided degree. CONCLUSIONS: The CS could promote the form action of new bone and accelerate the bone healing.

[Construction of a collagen gel dermis with improved biological property].

OBJECTIVE: To improve the biological property of artificial skin. METHODS: We have ameliorated Hansburgh and Middelkoop's method of manufacturing artificial dermis. The type I collagenase and Dispase were used to isolated neonate prepuce' dermis fibroblast. The gel dermis was constructed by compounding the fibroblast and collagen swelling solution. The property of the collagen gel dermis was measured. RESULTS: The neonate prepuce's dermis fibroblast had property of high proliferation, high activation of the dermis, and it could secrete abundant extracellular matrix (ECM). CONCLUSION: The collagen gel dermis is an useful dermis substitute.