Biocompatibility,degradability, bioactivity and osteogenesis of mesoporous/macroporous scaffolds of mesoporous diopside/poly(l-lactide) composite

Bioactive mesoporous diopside (m-DP) and poly(l-lactide) (PLLA) composite scaffolds with mesoporous/macroporous structure were prepared by the solution-casting and particulate-leaching method. The results demonstrated that the degradability and bioactivity of the mesoporous/macroporous scaffolds were significantly improved by incorporating m-DP into PLLA, and that the improvement was m-DP content-dependent. In addition, the scaffolds containing m-DP showed the ability to neutralize acidic degradation products and prevent the pH from dropping in the solution during the soaking period. Moreover, the scaffolds containing m-DP enhanced attachment, proliferation and alkaline phosphatase activity of MC3T3-E1 cells, which were also m-DP content-dependent. Furthermore, the histological and immunohistochemical analysis results showed that the scaffolds with m-DP significantly promoted new bone formation and improved the materials degraded in vivo, indicating good biocompatibility. The results suggested that the mesoporous/macroporous scaffolds of the m-DP/PLLA composite with osteogenesis had a potential for bone regeneration.     

Needle-like nano hydroxyapatite/poly(l-lactide acid) composite scaffold for bone tissue engineering application

In this paper, a new nano-hydroxyapatite / poly (l-lactide acid) (nHAP/PLLA) composite scaffold comprising needle-like nHAP particles was prepared. In the first step, the identification and morphology of chemically synthesized HAP particles were determined by XRD, EDX, FTIR and SEM analyses. The needle-like nHAP particles with an average size of approximately 30–60 nm in width and 100–400 nm in length were found similar to needle-like bone nano apatites in terms of chemical composition and morphology. In the second step, nHAP and micro-sized HAP (mHAP) particles were used to fabricate HAP filled PLLA (HAP/PLLA) composites scaffolds using solid–liquid phase separation method. The porosity of scaffolds was up to 85%, and their average macropore diameter was in the range of 64–175 µm. FTIR and XRD analyses showed the presence of molecular interactions and chemical linkages between HAP particles and PLLA matrix. The compressive strength of nanocomposite scaffolds could high up to 8.46 MPa while those of pure PLLA and microcomposite scaffolds were 1.79 and 4.61 MPa, respectively. The cell affinity and cytocompatibility of the nanocomposite scaffold were found to be higher than those of pure PLLA and microcomposite scaffolds. Based on the results, the newly developed nHAP/PLLA composite scaffold is comparable with cancellous bone in terms of microstructure and mechanical strength, so it may be a suitable alternative for bone tissue engineering applications.     

Preparation and characterization of novel CdSe quantum dots modified with poly (d,l-lactide) nanoparticles

In this paper, novel CdSe quantum dots (QDs) modified with poly (d, l-lactide) (PLA) nanoparticles by nanoprecipitation method was reported. CdSe QDs modified with PLA nanoparticles were characterized by Photon correlation spectroscope (PCS), transmission electron microscope (TEM), flluorescence spectrophotometer and fluorescence microscope. The modified CdSe QDs were spherical and relatively uniform. The modified CdSe QDs were water soluble and their strong yellow fluorescence emission was observed both in vitro and in vivo. The fluorescence of the modified CdSe QDs was stable in aqueous solution for more than 30 d. These modified CdSe QDs are expected to have much potential for biological labeling and diagnostics based on above properties.     

Preparation and characterization of biodegradable poly(d,l-lactide) and surface-modified bioactive glass composites as bone repair materials

In order to improve filler dispersion and phase compatibility between poly(d,l-lactide) (PDLLA) and inorganic bioactive glass (BG) particles, and to enhance the mechanical properties of PDLLA/BG composites, the silane coupling agent 3-glycidoxypropyltrimethoxysilane (KH570) was used to modify the surface of BG particles (represented by KBG). The structure and properties of PDLLA/BG and PDLLA/KBG composites were investigated by mechanical property testing and scanning electron microscopy (SEM). This study demonstrated that the Guth and Gold models can be combined to predict the Young’s modulus of the composites. The Pukanszky modulus showed that the interaction parameter B of PDLLA/KBG composites was higher than that of the PDLLA/BG, which indicates that there is a higher interfacial interaction between the PDLLA and KBG. The composites were incubated in simulated body fluid (SBF) at 37°C to study the in vitro degradation and bioactivity of the composites and to detect bone-like apatite formation on their surfaces.     

Synthesis and properties of poly(d,l-lactide) drug carrier with maghemite nanoparticles

A magnetic polymeric carrier, composed of biodegradable poly(d,l-lactide) microspheres, maghemite nanoparticles and anti-cancer drug (paclitaxel) was successfully prepared in dichloromethane using high-speed homogenization. Maghemite nanoparticles were well dispersed in PLA matrix. The carrier was magnetically responsive and exhibited low cytotoxicity. Release of loaded paclitaxel was enhanced by applying an oscillating magnetic field. The thermal energy generated by maghemite nanoparticles due to magnetic hysteresis loss was very low and considered negligible in influencing the release behavior. Alternating movement of the nanoparticles, stimulated by magnetic force, resulting in deterioration of the mechanical properties of polymer matrix was likely to be the main reason for the enhancement in drug release.     

Determination of thermodynamic interactions of poly(l-lactide) and biphasic calcium phosphate/poly(l-lactide) composite by inverse gas chromatography at infinite dilution

Inverse gas chromatography at infinite dilution was applied to determine the thermodynamic interactions of poly(l-lactide) (PLLA) and the composite of biphasic calcium phosphate and PLLA (BCP/PLLA). The specific retention volumes, $ V_{\text{g}}^{0} $ , of 11 organic compounds of different chemical nature and polarity (non-polar, donor or acceptor) were determined in the temperature range of 308–378 K for PLLA and 308–398 K for BCP/PLLA. The weight fraction activity coefficients of test sorbates, $ \Omega_{1}^{\infty } $ , and the Flory–Huggins interaction parameters, $ \chi_{12}^{\infty } $ , were estimated and discussed in terms of interactions of the sorbates with PLLA and BCP/PLLA. Also, the partial molar free energy, $ \Delta G_{1}^{\infty } $ , the partial molar heat of mixing, $ \Delta H_{1}^{\infty } $ , the sorption molar free energy, $ \Delta G_{1}^{\text{S}} $ , the sorption enthalpy, $ \Delta H_{1}^{\text{S}} $ , and the sorption entropy, $ \Delta S_{1}^{\text{S}} $ , were analyzed. A different chromatographic behavior of the two investigated samples, PLLA and BCP/PLLA, was observed. The values of $ \Omega_{1}^{\infty } $ indicated n-alkanes, diethyl ether, tetrahydrofurane (THF), cyclohexane, benzene, dioxane (except for 338 K), and ethyl acetate (EtAc) (except for 338 K) as non-solvents, and chloroform (CHCl₃) as good solvent (except for 378 K) for PLLA. For BCP/PLLA, CHCl₃, EtAc (for 378 K), dioxane (except for 378 K), and THF were indicated as good solvents.     

Surface modification of poly(l-lactide) electrospun fibers with nanocrystal hydroxyapatite for engineered scaffold applications

The hydrophobicity of the poly(l-lactide) (PLLA) surface was modified by incorporating hydroxyapatite (HAp) nanocrystalline particles during the electrospinning process for the engineered scaffold applications. The HAp nanocrystals were synthesized with 30 nm in diameter and 100–120 nm in length, which subsequently formed micrometer-sized agglomerates in the range of 2.5 μm. The synthesized HAp agglomerates were electrospun in the PLLA solution, and the HAp nanocrystals were desirably exposed on the surface of the electrospun PLLA fibers to give higher surface energy and lower contact angles with water. The surface-exposed hydrophilic HAp nanocrystals substantially increased the precipitation of various salts on the HAp/PLLA fiber surfaces in a buffer solution due to the hydrophilic nature and ionic affinity of HAp. Finally, the developed HAp/PLLA fibers desirably sustained the fibrous structural integrity during the accelerated-aging test in water, which was not the case with the pristine PLLA fibers.     

Novel antibacterial electrospun mats based on poly(d,l-lactide) nanofibers and zinc oxide nanoparticles

This investigation addresses the morphological, mechanical, and antibacterial evaluation of nanocomposite mats based on poly(d,l-lactide) nanofibers with different zinc oxide nanoparticles (nano-ZnO) concentration, that were elaborated by two techniques, i.e., electrospinning of polymer/ZnO solutions and the combination of electrospinning of polymer solutions with electrospraying of nano-ZnO dispersions. The analysis of the precursory solutions was carried out in order to understand the achieved morphology of nanofibers. The obtained poly(d,l-lactide)/ZnO fibrous mats showed a uniform morphology with an average porosity ca. 55 % and average pore size around 45 μm. The presence of ZnO nanoparticles increased the toughness of the mats, and an optimal nano-ZnO concentration (i.e., 3 wt%) was observed at which the tensile strength and Young’s modulus could be improved. Concerning to the antibacterial properties, a relatively low concentration of nanoparticles provoked a growth inhibition of the Gram-negative Escherichia coli and the Gram-positive Staphylococcus aureus bacteria. The mats have potential features for use as antimicrobial wound dressings.     

尿素三聚氰胺甲醛三组分复合树脂包覆苯乙烯微胶囊的制备研究

针对热塑性材料的自修复,以尿素、三聚氰胺、甲醛共聚物为囊壁,苯乙烯为囊芯合成了包覆苯乙烯的改性脲醛树脂微胶囊,并采用红外光谱、扫描电子显微镜、纳米粒度电位仪等分析了微胶囊的化学成分及表面形貌,发现其表面粗糙致密,形状基本呈球形,粒径分布较集中,包封率为72%,有望应用于自修复材料。     

Multifunctional hydroxyapatite and poly(d,l-lactide-co-glycolide) nanoparticles for the local delivery of cholecalciferol

Cholecalciferol, vitamin D₃, plays an important role in bone metabolism by regulating extracellular levels of calcium. Presented here is a study on the effects of the local delivery of cholecalciferol (D₃) using nanoparticulate carriers composed of hydroxyapatite (HAp) and poly(d,l-lactide-co-glycolide) (PLGA). Multifunctional nanoparticulate HAp-based powders were prepared for the purpose of: (a) either fast or sustained, local delivery of cholecalciferol, and (b) the secondary, osteoconductive and defect-filling effect of the carrier itself. Two types of HAp-based powders with particles of narrowly dispersed sizes in the nano range were prepared and tested in this study: HAp nanoparticles as direct cholecalciferol delivery agents and HAp nanoparticles coated with cholecalciferol-loaded poly(d,l)-lactide-co-glycolide (HAp/D₃/PLGA).Satisfying biocompatibility of particulate systems, when incubated in contact with MC3T3-E1 osteoblastic cells in vitro, was observed for HAp/D₃/PLGA and pure HAp. In contrast, an extensively fast release of cholecalciferol from the system comprising HAp nanoparticles coated with cholecalciferol (HAp/D3) triggered necrosis of the osteoblastic cells in vitro. Artificial defects induced in the osteoporotic bone of the rat mandible were successfully reconstructed following implantation of cholecalciferol-coated HAp nanoparticles as well as those comprising HAp nanoparticles coated with cholecalciferol-loaded PLGA (HAp/D₃/PLGA). The greatest levels of enhanced angiogenesis, vascularization, osteogenesis and bone structure differentiation were achieved upon the implementation of HAp/D₃/PLGA systems.     

Alkaline hydrolysis of modified poly(l-lactide) monolayers

In this work, hydrolysis of biodegradable poly(l-lactide) (l-PLA) and copolymers of l-lactide (l-LA) and (benzyloxycarbonyl) methyl mophorline-2,5-dione (BMD) was investigated at the air/water interface. In order to improve the hydrophilicity of l-PLA, small amounts of BMD were copolymerized with l-LA. NaOH was used to adjust the pH of the subphase water. Under the conditions studied here, polymer monolayers showed much faster hydrolysis as either a subphase pH or the concentration of BMD in the copolymer is increased. This result was explained by increasing numbers of base attack sites per unit area and increasing hydrophilicity.     

Improvement of surface bioactivity of poly(lactic acid) biopolymer by sandblasting with hydroxyapatite bioceramic

This study communicates a simple and effective method for modification of the surface of synthetic biopolymer poly(lactic acid) (PLA) with bioactive ceramic hydroxyapatite (HA) using a sandblasting technique. The sandblasting particles were bombarded onto the PLA, covering the surface quite evenly. The HA-sandblasted PLA showed good in vitro apatite forming ability in a simulated body fluid within a few days, which was rarely observed for pure PLA. Moreover, the HA-sandblasted PLA enhanced the initial cell adhesion and further proliferation, and up-regulated bone cell functions such as the alkaline phosphatase activity. This novel method of surface modification of the biopolymer with bioactive ceramic has the potential for use in developing bone bioactive implantable materials.     

介孔纳米羟基磷灰石/左旋聚乳酸复合材料的制备及性能

为考察介孔纳米羟基磷灰石(MHA)/左旋聚乳酸(PLLA)复合材料的性能,以十六烷基三甲基溴化铵(CTAB)为模板合成MHA,采用溶液相分离结合粒子沥滤法制备了不同纳米粒子含量的MHA/PLLA多孔支架复合材料,考察了其抗压缩性能和淬断面微观结构。采用溶液浇注法制备了MHA/PLLA复合膜,并对其拉伸性能和拉伸断面微观结构进行了研究。FTIR、XRD、TEM和氮气吸附测试等结果显示:合成的MHA具有典型的晶体结构、介孔结构和较高的比表面积。力学测试结果显示:在发生10%压缩形变时,填料含量为1%、5%和10%的MHA/PLLA多孔支架复合材料的抗压缩强度随填料含量增加而提高,与相应含量的纳米羟基磷灰石(HA)/PLLA多孔支架复合材料相比,分别提高了约37.0%、67.7%和144.7%。在填料含量为5%和10%时,MHA/PLLA复合膜的拉伸强度较HA/PLLA复合膜分别提高约38.7%和46.1%,拉伸模量分别提高约35.4%和14.5%。而且MHA/PLLA复合膜具有更高的断裂伸长率,填料含量为1%、5%和10%时断裂伸长率分别较HA/PLLA复合膜提高约91.3%、79.7%和96.1%。FESEM结果显示:尤其当填料含量较高时,MHA/PLLA多孔支架复合材料或复合膜中填料粒子分布较HA/PLLA中均匀。结果表明:与HA/PLLA复合材料相比,随着MHA含量增加,MHA/PLLA复合材料具有更好的力学性能,MHA在PLLA基体中分布相对更均匀。     

Preparation and characterization of melt processed poly(l-lactide)/layered double hydroxide nonocomposites

This work reports the fabrication and physical properties of biodegradable poly(l-lactide) (PLLA) composites containing a fraction of unmodified layered double hydroxides (LDH–NO₃) and γ-polyglutamate-modified layered double hydroxides (γ-LDH) by melt blending process. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) experimental results showed that the original LDH–NO₃ with the certain amount of aggregates was unevenly dispersed throughout the PLLA matrix. Conversely, γ-LDH allows the formation of an intercalated nanocomposite. Although the water vapor permeability of the PLLA/LDH systems was decreased with increasing the loading of LDH, the barrier property of PLLA reinforced with γ-LDH is superior to that of PLLA-L composites. The effects of both LDHs on mechanical and thermal properties of PLLA were also investigated.     

Development of degradable and bioactive composite as bone implants by incorporation of mesoporous bioglass into poly(l-lactide)

Bioactive composites containing mesoporous bioglass (MBG) and poly(l-lactide) (PLLA) for bone regeneration were fabricated by solution casting method. The results showed that the compressive strength and hydrophilicity of the MBG/PLLA composites significantly improved with the increase of MBG content. In addition, the weight loss ratio of the composites in Tris–HCl solution was obviously enhanced with the increase of MBG content. Moreover, the composite containing MBG could compensate for the decrease of pH value by neutralizing the acidic products from PLLA degradation in the Tris–HCl solution. Furthermore, the MBG/PLLA composites could induce apatite formation on their surfaces after soaked into simulated body fluid (SBF), indicating good bioactivity. In cell culture experiments, the results showed that the composite could enhance cell attachment, proliferation and alkaline phosphatase activity (ALP) of MC3T3-E1 cells, and the improvements were dependent on the MBG content in the composites. In short, the MBG/PLLA biocomposites with improved properties of hydrophilicity, degradability, bioactivity, neutralizing acidic degradable products and good cytocompatibility would be a promising orthopedic implant material for bone repair application.     

Preparation of hydroxyapatite/poly(methyl methacrylate) and calcium silicate/poly(methyl methacrylate) interpenetrating hybrid composites

Hydroxyapatite/poly(methyl methacrylate) (HAp/PMMA) and calcium silicate/poly(methyl methacrylate) (CS/PMMA) composites were prepared by interpenetrating bulk polymerization of methyl methacrylate (MMA) monomer in porous structures of HAp and CS. The porous HAp and CS templates were prepared by mixing their calcined powders with poly(vinyl alcohol) (PVA) solution, shaping by uniaxial pressing and then firing at 1,100 °C for HAp and 900 °C for CS. The templates were soaked in the solution mixture of MMA monomer and 0.1 mol% of benzoyl peroxide (BPO) for 24 h. The pre-composites were then bulk polymerized at 85 °C for 24 h under nitrogen atmosphere. The microstructures of the composites showed the interpenetrating of PMMA into the porous HAp and CS structures. Thermogravimetric analysis indicated that the PMMA content in the HAp/PMMA and CS/PMMA composites were 13 and 26 wt%, respectively. Weight average molecular weights ( ) of PMMA were about 491,000 for HAp/PMMA composites and about 348,000 for CS/PMMA composites. Compressive strengths of these composites were about 90–131 MPa in which they were significantly higher than their starting porous templates.     

Characterisation, corrosion resistance and in vitro bioactivity of manganese-doped hydroxyapatite films electrodeposited on titanium

This work elucidated the corrosion resistance and in vitro bioactivity of electroplated manganese-doped hydroxyapatite (MnHAp) film on NaOH-treated titanium (Ti). The NaOH treatment process was performed on Ti surface to enhance the adhesion of the MnHAp coating on Ti. Scanning electron microscopy images showed that the MnHAp coating had needle-like apatite crystals, and the approximately 10 μm thick layer was denser than HAp. Energy-dispersive X-ray spectroscopy analysis revealed that the MnHAp crystals were Ca-deficient and the Mn/P molar ratio was 0.048. X-ray diffraction confirmed the presence of single-phase MnHAp, which was aligned vertically to the substrate. Fourier transform infrared spectroscopy indicated the presence of phosphate bands ranging from 500 to 650 and 900 to 1,100 cm^?1, and a hydroxyl band at 3,571 cm^?1, which was characteristic of HAp. Bond strength test revealed that adhesion for the MnHAp coating was more enhanced than that of the HAp coating. Potentiodynamic polarisation test showed that the MnHAp-coated surface exhibited superior corrosion resistance over the HAp single-coated surface. Bioactivity test conducted by immersing the coatings in simulated body fluid showed that MnHAp coating can rapidly induce bone-like apatite nucleation and growth. Osteoblast cellular tests revealed that the MnHAp coating was better at improving the in vitro biocompatibility of Ti than the HAp coating.     

Immobilization of poly (ethylene imine) on poly (l-lactide) promotes MG63 cell proliferation and function

Poly (ethylene imine) (PEI) is a polycation widely used for DNA transfection to cells but also applied as primary polycation for layer-by-layer (LBL) assembly of polyelectrolytes. The aim of the present study was to investigate the effect of modification with PEI on the biocompatibility of poly (l-lactide) (PLLA) films. PEI with different molecular weight was immobilized on PLLA by either adsorption or covalent binding. Cell morphologies, immuno-fluorescence staining, cell proliferation by lactate dehydrogenase assay and cell differentiation by alkaline phosphatase assay were utilized to assess the biocompatibility of the modified PLLA using osteoblast cell line MG63. Results revealed that PEI modification remarkably improved cell adhesion, viability, proliferation and function compared with plain PLLA. Hence, PEI-modified PLLA is acceptable as transfection vehicle for engineering of bone and other tissues, or as primary layer to allow LBL assembly to generate biomimetic surface coatings.