Synthesis,Characterization and Application of Methyl 3,5-Disulfo-benzoate Dipotassium Dihydrate as Nucleating Agent for Poly（L-lactide）

A newly synthesized aromatic sulfonate compound,complex 2 with formula of K2[H3COOC-C6H3（SO3）2]·2H2O（methyl 3,5-disulfo-benzoate dipotassium dihydrate） was synthesized and characterized by elemental analysis,infrared（IR） spectrometry,nuclear magnetic resonance（NMR） and crystal structure measurement.Single-crystal X-ray diffraction（XRD） revealed that complex 2 crystallized in the triclinic system with space group P（i）.Complex 2 was used as nucleating agent for poly（L-lactide）（PLLA）.The crystallization of PLLA with powder of complex 2 was investigated by means of differential scanning calorimetry（DSC） and polarized optical microscopy （POM）.The results prove that complex 2 was effective as nucleating agent for PLLA.It could accelerate crystallization by reducing the induction time and increasing the density of nuclei in the crystallization process.The half-time of crystallization（t0.5） for pure PLLA was about 8 times longer than that of PLLA sample with 1.0％（mass fraction） of complex 2.     

改性羟基磷灰石/聚乳酸纳米复合材料的结晶行为

利用溶剂复合的方法制备了具有良好生物相容性的表面接枝聚(γ-苄基-L-谷氨酸)的改性羟基磷灰石/聚乳酸纳米复合材料, 并研究了其熔融与结晶行为. 结果表明, 聚乳酸的玻璃化转变温度为60.3 ℃, 而复合材料的玻璃化转变温度达到65.8 ℃, 不同样品在140 ℃等温结晶后, 改性羟基磷灰石/聚乳酸复合材料的球晶直径仅为聚乳酸(PLLA)球晶直径的16.7%~66.7%. 复合材料的熔点提高到184.4 ℃.     

聚乳酸接枝改性纳米生物玻璃/PLGA复合材料的制备、表面性质及生物活性

以丙交酯开环聚合原位接枝改性的纳米生物玻璃(PLLA-g-BG)与聚丙交酯-乙交酯(PLGA)复合材料为研究对象, 采用TGA, ESEM和EDX分析其接枝率, 粒子分散性和表面元素分布, 通过将兔成骨细胞种植于材料膜表面进行体外培养, 采用荧光染色法、NIH Image J图像分析软件、MTT法和流式细胞术等手段检测细胞在材料表面的平均黏附数量、扩展面积比、增殖能力和细胞周期的变化, 综合评价新型改性纳米复合材料的生物相容性和生物活性. 结果表明, 聚乳酸表面接枝改性可明显改善纳米生物玻璃粒子的团聚; PLGA中掺入一定比例的改性PLLA-g-BG可明显促进兔成骨细胞的黏附、扩展与增殖; 改性纳米生物玻璃的应用可提高生物可降解聚酯材料的生物相容性和生物活性.     

Antibacterial poly(D,L-lactide) (PDLLA) fibrous membranes modified with quaternary ammonium moieties

<正>Antibacterial poly(D,L-lactide)(PDLLA) fibrous membranes were developed via electrospinning,followed by surface modification which involved plasma pretreatment,UV-induced graft copolymerization of 4-vinylpyridine(4VP) and quaternization of the grafted pyridine groups with hexylbromide.The success of modification with quatemized pyridinium groups on the PDLLA fibrous membranes was ascertained by X-ray photoelectron spectroscopy(XPS).The antibacterial activities of these membranes were assessed against Gram-positive Staphylococcus aureus(S.aureus) and Gram-negative Escherichia coli(E.coli).The PDLLA fibrous membranes modified with quaternized pyridinium groups showed antibacterial efficiency against both bacteria as high as 99.999%.The results demonstrated that the antibacterial activity was based on the interaction of the positive charge of pyridinium group and negatively charged cell membrane of bacteria, resulting in loss of membrane permeability and cell leakage.     

Biocompatibility properties of composite scaffolds based on 1,4-butanediamine modified poly(lactide-co-glycolide) and nanobioceramics

Three-dimensional biodegradable porous scaffolds play an important role in tissue engineering. The degradable scaffold material, based on 1,4-butanediamine-modified poly(lactide-co-glycolide) (BMPLGA), nano-bioactive glass (NBAG), and nano-β-tricalciumphosphate (β-TCP), was prepared by a solution-casting/salt-leaching method. The biological properties were studied by using cell cytotoxicity, von Kossa staining, alkaline phosphatase activity, hemolytic test, acute toxicity, and genetic toxicity test. The MTT results indicated that the BMPLGA/NBAG-β-TCP materials did not show any cytotoxicity. The result of von Kossa staining showed that the introduction of the NBAG and β-TCP promoted fibroblastic differentiation and improved the mineral deposition of the BMPLGA matrix. In addition, the presence of NBAG and β-TCP in the composite further enhanced the ALP activity in comparison with the sole BMPLGA material. The hemolytic potential showed that the nanocomposite scaffolds were non-hemolytic. The BMPLGA/NBAG-β-TCP scaffolds showed no acute systemic toxicity or mutagenic action. Therefore, the results indicated the BMPLGA/NBAG-β-TCP nanocomposite scaffold could be considered as a potential bone tissue engineering implant.     

Enzymatic degradation of poly(L-lactide) and poly(epsilon-caprolactone) electrospun fibers

Poly(L-lactide) (PLLA) and poly(epsilon-caprolactone) (PCL) ultrafine fibers were prepared by electrospinning. The influence of cationic and anionic surfactants on their enzymatic degradation behavior was investigated by measuring weight loss, molecular weight, crystallinity, and melting temperature of the fibers as a function of degradation time. Under the catalysis of proteinase K, the PLLA fibers containing the anionic surfactant sodium docecyl sulfate (SDS) exhibited a faster degradation rate than those containing cationic surfactant triethylbenzylammonium chloride (TEBAC), indicating that surface electric charge on the fibers is a critical factor for an enzymatic degradation. Similarly, TEBAC-containing PCL fibers exhibited a 47% weight loss within 8.5 h whereas SDS-containing PCL fibers showed little degradation in the presence of lipase PS. By analyzing the charge status of proteinase K and lipase PS under the experimental conditions, the importance of the surface charges of the fibers and their interactions with the charges on the enzymes were revealed. Consequently, a "two-step" degradation mechanism was proposed: (1) the enzyme approaches the fiber surface; (2) the enzyme initiates hydrolysis of the polymer. By means of differential scanning calorimetry and wide-angle X-ray diffraction, the crystallinity and orientation changes in the PLLA and PCL fibers during the enzymatic degradation were investigated, respectively.     

Electron-beam treatment of poly(lactic acid) to control degradation profiles

Bioresorbable polymers such as polylactide (PLA) and polylactide-co-glycolide (PLGA) have been used successfully as biomaterials in a wide range of medical applications. However, their slow degradation rates and propensity to lose strength before mass have caused problems. A central challenge for the development of these materials is the assurance of consistent and predictable in vivo degradation. Previous work has illustrated the potential to influence polymer degradation using electron beam (e-beam) radiation. The work addressed in this paper investigates further the utilisation of e-beam radiation in order to achieve a more surface specific effect. Variation of e-beam energy was studied as a means to control the effective penetrative depth in poly-l-lactide (PLLA). PLLA samples were exposed to e-beam radiation at individual energies of 0.5 MeV, 0.75 MeV and 1.5 MeV. The near-surface region of the PLLA samples was shown to be affected by e-beam irradiation with induced changes in molecular weight, morphology, flexural strength and degradation profile. Moreover, the depth to which the physical properties of the polymer were affected is dependent on the beam energy used. Computer modelling of the transmission of each e-beam energy level used corresponded well with these findings.     

In vitro and in vivo degradation behavior of aqueous-derived electrospun silk fibroin scaffolds

We investigated the in vitro degradation behavior of the electrospun silk fibroin (SF) scaffolds by protease XIV. Phosphate-buffered saline (PBS) without enzyme was used as a control. About 65% of the electrospun SF scaffolds were degraded within 24 d in protease XIV, while almost no scaffolds were degraded in PBS. A great deal of fragments was visible in protease XIV solution. SEM indicated surface erosion of the scaffolds increased during protease degradation with increasing exposure time. FTIR and XRD indicated the crystalline structure of the scaffolds decreased after protease degradation for 24 d, and a degradation mechanism was proposed. Furthermore, the results of the in vivo degradation by implantation in rats showed that the scaffolds were completely degraded in vivo after implantation for 8 weeks and well tolerated by the host animals. The insights gained in this study can serve as a guide to match desired degradation behavior with specific applications for the electrospun SF scaffolds, such as tissue engineering and drug delivery.     

Separation of proteins on surface-modified poly(dimethylsiloxane) microfluidic devices

Separation and detection of proteins have been realized on nonionic surfactant-modified poly(dimethylsiloxane) (PDMS) microfabricated devices with end-column amperometric detection. The hydrophobic PDMS channels are turned into hydrophilic ones after being modified with Brij35 and facilitate the separation of proteins. The coating can remarkably reduce the adsorption of large protein molecules and is stable in the range of pH 6-12. The detection of proteins in such channels needs less rinsing time and thus efficiency is raised. Even large molecules of proteins can also be detected with better reproducibility and enhanced plate numbers. The relative standard deviation (RSD) of the migration time for glucose oxidase (GOD) is 2.2% (n = 19). Separation of GOD and myoglobin has been developed in modified channels. Predominant operational variables, such as the coating conditions, the concentration of surfactant and buffer, are studied in detail.     

Mechanical and thermal properties of polypeptide modified hydroxyapatite/poly(L-lactide) nanocomposites

A new type of polypeptide(poly(-benzyl-L-glutamate)(PBLG))modified hydroxyapatite(HA)/poly(L-lactide)(PLLA)nanocomposites(PBLG-g-HA/PLLA)were prepared by the solvent-mixing method,and their mechanical and thermal properties were investigated.The tensile test showed that the mechanical properties of PBLG-g-HA/PLLA nanocomposites were better than that of PLLA,even a 0.3 wt%content of PBLG-g-HA in the nanocomposites could make the tensile strength 12%higher than that of the neat PLLA sample,and the tensile mod...     

Preparation and evaluation of nano-hydroxyapatite/poly(styrene-divinylbenzene) porous microsphere for aspirin carrier

A novel vehicle for the delivery of aspirin (ASA) was prepared from porous nano-hydroxyapatite/poly(styrene-divinylbenzene) [nano-HAP/P(St-DVB)] composite microspheres by grafting nano-HAP [Ca10(PO4)6(OH)2] onto porous P(St-DVB) microspheres. Four types of porous composite microspheres were prepared, each with different nano-HAP contents. The ASA-loaded composite microspheres prepared with 10% and 15% nano-HAP (mass ratio) exhibited excellent buoyancy with relatively short instantaneous floating time (within 10 min) and a long sustained floating time (12 h) in simulated gastric juice. They also offered good sustained release of ASA (up to 8 h). Furthermore, these composite microspheres displayed good buffering capacity that prevented the buildup of acidity caused by hydrolysis of ASA, keeping the pH of gastric juice within the normal range (pH 0.9 to 1.5). The results showed that porous nano-HAP/P(St-DVB) composite microspheres prepared with 10% and 15% nano-HAP could be used as a novel drug carrier for ASA, providing a sustained release dose without leading to stomach irritation, a side effect that is often associated with ASA medication.