Preparation of β-Ca<Subscript>3</Subscript>(PO<Subscript>4</Subscript>)<Subscript>2</Subscript>/Poly(D,L-lactide) and β-Ca<Subscript>3</Subscript>(PO<Subscript>4</Subscript>)<Subscript>2</Subscript>/Poly(ε-caprolactone) Biocomposite Implants for Bone Substitution

Highly permeable macroporous implants of various architectures for bone grafting have been fabricated by thermal extrusion 3D printing using highly filled β-Ca₃(PO₄)₂/poly(D,L-lactide) (degree of filling up to 70 wt %) and β-Ca₃(PO₄)₂/poly(ε-caprolactone) (degree of filling up to 70 wt %) composite filaments. To modify the surface of the composite macroporous implants with the aim of improving their wettability by saline solutions, we have proposed exposing them to a cathode discharge plasma (2.5 W, air as plasma gas) in combination with subsequent etching in a 0.5 M citric acid solution. It has been shown that the main contribution to changes in the wettability (contact angle) of the composites is made by the changes produced in their surface morphology by etching in a low-temperature plasma and citric acid. An alternative approach to surface modification of the composites is to produce a carbonate hydroxyapatite layer via precipitation from a simulated body fluid solution a factor of 5 supersaturated relative to its natural analog (5xSBF).     

Hydroxyapatite nanorod-reinforced biodegradable poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactic acid) composites for bone plate applications

Novel PLLA composite fibers containing hydroxyapatite (HAp) nanorods with or without surface lactic acid grafting were produced by extrusion for use as reinforcements in PLLA-based bone plates. Fibers containing 0–50% (w/w) HAp nanorods, aligned parallel to fiber axis, were extruded. Lactic acid surface grafting of HAp nanorods (lacHAp) improved the tensile properties of composites fibers better than the non-grafted ones (nHAp). Best tensile modulus values of 2.59, 2.49, and 4.12 GPa were obtained for loadings (w/w) with 30% lacHAp, 10% nHAp, and 50% amorphous HAp nanoparticles, respectively. Bone plates reinforced with parallel rows of these composite fibers were molded by melt pressing. The best compressive properties for plates were obtained with nHAp reinforcement (1.31 GPa Young’s Modulus, 110.3 MPa compressive strength). In vitro testing with osteoblasts showed good cellular attachment and spreading on composite fibers. In situ degradation tests revealed faster degradation rates with increasing HAp content. To our knowledge, this is the first study containing calcium phosphate–polymer nanocomposite fibers for reinforcement of a biodegradable bone plate or other such implants and this biomimetic design was concluded to have potential for production of polymer-based biodegradable bone plates even for load bearing applications.     

Preparation of nano-HA/PLA composite by modified-PLA for controlling the growth of HA crystals

In order to control the growth of hydroxyapatite (HA) crystals and obtain nano-hydroxyapatite/poly(lactide) (n-HA/PLA) composite with interfacial interaction between the two phases, PLA surfaces were modified with poly(α-methacrylic acid) (PMAA) via photooxidization and UV induced polymerization. FTIR analysis showed that the PMAA was grafted onto the PLA surface and the grafting rate increased with the grafting time. The n-HA/PLA composites were synthesized by modified-PLA and characterized by FTIR, XRD and SEM. Several analyses suggested that the m-PLA could act as a template to manipulate the nucleation and growth of n-HA crystals, control the morphology and size of n-HA crystals as well as their distribution over the organic phase.     

端羟基聚乳酸共聚物的合成及表征

以乳酸为原料,辛酸亚锡为催化剂,采用梯度升温法,在168℃、0.098 MPa下直接熔融缩聚合成端羟基改性聚乳酸共聚物聚（乳酸/1,4丁二醇）[P（LA/BDO）]、聚（乳酸/二乙醇胺）[P（LA/DEA）]和聚（乳酸/ε-己内酯）[P（LA/CL）]。用乌氏黏度法、红外光谱（FT-IR）、核磁共振（1H-NMR）、差...     

Electrospun PCL/PLA/HA based nanofibers as scaffold for osteoblast-like cells

Polycaprolactone (PCL), poly (lactic acid) (PLA) and hydroxyapatite (HA) are frequently used as materials for tissue engineering. In this study, PCL/PLA/HA nanofiber mats with different weight ratio were prepared using electrospinning. Their structure and morphology were studied by FTIR and FESEM. FTIR results demonstrated that the HA particles were successfully incorporated into the PCL/PLA nanofibers. The FESEM images showed that the surface of fibers became coarser with the introduction of HA nanoparticles into PCL/PLA system. Furthermore, the addition of HA led to the decreasing of fiber diameter. The average diameters of PCL/PLA/HA nanofiber were in the range of 300-600 nm, while that of PCL/PLA was 776 +/- 15.4 nm. The effect of nanofiber composition on the osteoblast-like MC3T3-E1 cell adhesion and proliferation were investigated as the preliminary biological evaluation of the scaffold. The MC3T3-E1 cell could be attached actively on all the scaffolds. The MTT assay revealed that PCL/PLA/HA scaffold shows significantly higher cell proliferation than PCL/PLA scaffolds. After 15 days of culture, mineral particles on the surface of the cells was appeared on PCL/PLA/HA nanofibers while normal cell spreading morphology on PCL/PLA nanofibers. These results manifested that electrospun PCL/PLA/HA scaffolds could enhance bone regeneration, showing their marvelous prospect as scaffolds for bone tissue engineering.     

Development and characterization of nano‐crystalline cellulose incorporated poly(lactic acid) composite films

Development of nano‐cellulose has fascinated a substantial attention for last few decades because of their exceptional and potentially useful features. Herein, nano‐crystalline cellulose has successfully been prepared from local cotton yarn via acid hydrolysis. Both X‐ray diffraction and scanning electron microscopy showed improvement in crystallinity of nano‐crystalline cellulose on acid hydrolysis of cotton yarn. The prepared nano‐crystalline cellulose has been used for the fabrication of poly(lactic acid) composite films using solution casting approach. The prepared composite films were characterized using advanced analytical techniques. The differential scanning calorimetry analysis, moreover, showed that on incorporating nano‐crystalline cellulose in the poly(lactic acid) matrix, glass transition temperature increased; whereas, melting temperature and cold crystallization temperature decreased. The decreasing value of crystallization temperature indicated an enhancement in chain mobility of composite films. The mechanical analysis showed that the composite films were stronger and more flexible than the pure poly(lactic acid) films.     

Ionic Colloidal Molding as a Biomimetic Scaffolding Strategy for Uniform Bone Tissue Regeneration

Inspired by the highly ordered nanostructure of bone, nanodopant composite biomaterials are gaining special attention for their ability to guide bone tissue regeneration through structural and biological cues. However, bone malformation in orthopedic surgery is a lingering issue, partly due to the high surface energy of traditional nanoparticles contributing to aggregation and inhomogeneity. Recently, carboxyl‐functionalized synthetic polymers have been shown to mimic the carboxyl‐rich surface motifs of non‐collagenous proteins in stabilizing hydroxyapatite and directing intrafibrillar mineralization in‐vitro. Based on this biomimetic approach, it is herein demonstrated that carboxyl functionalization of poly(lactic‐co‐glycolic acid) can achieve great material homogeneity in nanocomposites. This ionic colloidal molding method stabilizes hydroxyapatite precursors to confer even nanodopant packing, improving therapeutic outcomes in bone repair by remarkably improving mechanical properties of nanocomposites and optimizing controlled drug release, resulting in better cell in‐growth and osteogenic differentiation. Lastly, better controlled biomaterial degradation significantly improved osteointegration, translating to highly regular bone formation with minimal fibrous tissue and increased bone density in rabbit radial defect models. Ionic colloidal molding is a simple yet effective approach of achieving materials homogeneity and modulating crystal nucleation, serving as an excellent biomimetic scaffolding strategy to rebuild natural bone integrity.     

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.     

Fabrication and mechanical properties of PLLA/PCL/HA composites via a biomimetic, dip coating, and hot compression procedure

Currently, the bone-repair biomaterials market is dominated by high modulus metals and their alloys. The problem of stress-shielding, which results from elastic modulus mismatch between these metallic materials and natural bone, has stimulated increasing research into the development of polymer-ceramic composite materials that can more closely match the modulus of bone. In this study, we prepared poly(l-lactic acid)/hydroxyapatite/poly(ε-caprolactone) (PLLA/HA/PCL) composites via a four-step process, which includes surface etching of the fiber, the deposition of the HA coating onto the PLLA fibers through immersion in simulated body fluid (SBF), PCL coating through a dip-coating process, and hot compression molding. The initial HA-coated PLLA fiber had a homogeneous and continuous coating with a gradient structure. The effects of HA: PCL ratio and molding temperature on flexural mechanical properties were studied and both were shown to be important to mechanical properties. Mechanical results showed that at low molding temperatures and up to an HA: PCL volume ratio of 1, the flexural strain decreased while the flexural modulus and strength increased. At higher mold temperatures with a lower viscosity of the PCL a HA: PCL ratio of 1.6 gave similar properties. The process successfully produced composites with flexural moduli near the lower range of bone. Such composites may have clinical use for load bearing bone fixation.     

药物缓释材料聚(乳酸-丙氨酸)的直接法合成与表征

直接以外消旋乳酸(LA)、L-丙氨酸(Ala)为原料[n(LA):n(Ala)=9:1],采用熔融聚合法合成药物缓释材料聚(乳酸-丙氨酸)共聚物[P(LA-co-Ala)],并用特性黏数、FTIR、1H NMR、GPC、DSC、XRD等手段进行系统表征.熔融共聚中采用一次投料并分次预聚,可生成重均相对分子质量(Mw)达3200(分散度Mw/Mn＝1.23)的共聚物,相对分子质量可以达到丙交酯开环共聚法的水平.首次报道了P(LA-co-Ala)]药物缓释材料的DSC与XRD表征结果,其与聚外消旋乳酸(PDLLA)相比,共聚物具有较低的Tg、Tm和结晶度.新方法步骤少、操作简便,且成本更加低廉.     

One‐step method for the preparation of poly(methyl methacrylate) modified titanium‐bioactive glass three‐dimensional scaffolds for bone tissue engineering

A novel three‐dimensional (3D) titanium (Ti)‐doping meso‐macroporous bioactive glasses (BGs)/poly(methyl methacrylate) (PMMA) composite was synthesised using PMMA and EO₂₀ PO₇₀ EO₂₀ (P₁₂₃) as the macroporous and mesoporous templates, respectively. Unlike the usual calcination method, the acid steam technique was used to improve the polycondensation of Ti‐BGs, and then PMMA was partially extracted via chloroform to induce the macroporous structure. Simultaneously, the residual PMMA which remained in the wall enhanced the compressive strength to 2.4 MPa (0.3 MPa for pure BGs). It is a simple and green method to prepare the macro‐mesoporous Ti‐BGs/PMMA. The materials showed the 3D interconnected hierarchical structure (250 and 3.4 nm), making the fast inducing‐hydroxyapatite growth and the controlled drug release. Besides mentioned above, the good antimicrobial property and biocompatible of the scaffold also ensure it is further of clinical use. Herein, the fabricated materials are expected to have potential application on bone tissue regeneration.Inspec keywords: titanium, bone, tissue engineering, glass, materials preparation, biomedical materials, polymers, porous materials, drug delivery systems, nanomedicineOther keywords: poly(methyl methacrylate), PMMA preparation, 3D titanium‐bioactive glass scaffold, bone tissue engineering, titanium‐doping mesomacroporous bioactive glass, bioactive glass‐PMMA composite, macroporous template, mesoporous template, calcination method, acid steam technique, titanium‐bioactive glass polycondensation, macroporous structure, green method, macromesoporous titanium‐bioactive glass‐PMMA, 3D interconnected hierarchical structure, fast inducing‐hydroxyapatite growth, controlled drug release, bone tissue regeneration, Ti     

氢氧化钠催化淀粉/乳酸接枝共聚物的合成

以氢氧化钠(NaOH)为催化剂,采用原位一步法合成了淀粉/乳酸接枝共聚物。用红外光谱(IR)、扫描电镜(SEM)和核磁共振(1H-NMR)测试方法对淀粉/乳酸接枝共聚物的结构进行了表征。IR和1H-NMR核磁图谱均表明,聚乳酸确实接枝到了淀粉上;SEM分析表明,经乳酸接枝改性后的淀粉的形貌发生了很大变化。同时通过改变NaOH溶液浓度,原料比例,聚合温度和聚合时间考察了反应条件对淀粉与乳酸接枝率的影响,结果表明,当NaOH溶液浓度为0.4 mol/L,淀粉∶乳酸(质量比)为1∶6,聚合温度为90℃,聚合时间为9 h时,淀粉的接枝率可达33.6%。     

聚DL-丙交酯/羟基磷灰石(PDLLA/HA) 复合材料——Ⅱ : 硅烷偶联剂处理羟基磷灰石表面的作用研究

采用硅烷偶联剂(A -174) 对羟基磷灰石(HA ) 表面进行处理, XPS 分析表明, 偶联剂在羟基磷灰石表面形成多层结构, 并生成稳定的化学键O-P-Si。将经偶联剂处理的HA 微粉与聚DL -丙交酯(PDLLA ) 复合, 所制备的复合材料力学强度与处理前相比得到明显提高。SEM 显示, 经处理后的HA 微粒在PDLLA 基质中分散均匀, 两者结合紧密。本文作者认为, 加强复合材料的界面相互作用和提高填充质在基质中的分散度是提高复合材料力学强度的有效途径。     

端羟基聚(乳酸-己内酯)共聚物的合成及表征

以乳酸(D,L-LA)和ε-己内酯(-εCL)为原料,采用梯度升温法,通过直接熔融缩聚合成了系列端羟基聚(乳酸-己内酯)共聚物(PLCA)。最佳工艺条件为:压力0.098MPa,催化剂Sn(Oct)2用量0.8%(质量分数),n(D,L-LA)∶n(-εCL)=8∶2,聚合温度170℃,反应7h。用特性粘度、FT-IR1、H-NMR、XRD、DSC等对其进行表征,结果表明,系列PLCA中的粘均分子量最大可达20785,Tg均比PLA的小,且随-εCL含量的增加,Tg越小,有效改善了PLA的脆性。结晶度比PLA有所降低,说明-εCL的加入使柔韧性增强。     

Controlled release systems based on poly(lactic acid). An in vitro and in vivo study

A new biodegradable delivery system based on poly(lactic acid) has been formulated, with potential applications in sustained antibiotic release against bone infection. The in vitro release of a new quinolone (pefloxacin) from low molecular weight poly(D,L-lactic acid) Mw = 2×10³ lasted for 56 d whereas the in vivo delivery lasted 33 d. In both cases, the release rate is controlled by the drug diffusion and the polymer degradation, which seems to be the predominant factor. For the release experiments, discs were prepared from poly (D,L-lactide) Mw = 2×10⁴ with drug loadings of 2% and 10% w/w. It was concluded that pefloxacin concentration remains higher than the Minimum Inhibitory Concentration (MIC) against the major causative bacteria of bone infection. The results indicate that the two different types of poly(lactic acid) can be used effectively in an implantable antibiotic release system. ©2000 Kluwer Academic Publishers     

羟基磷灰石的表面改性及其对聚乳酸基多孔支架性能的影响

分别采用柠檬酸和硬脂酸对纳米羟基磷灰石（n-HA）进行表面处理,并利用TGA、FTIR、XPS等研究了不同改性剂的改性效果,发现柠檬酸和硬脂酸能够成功接枝在n-HA表面,但硬脂酸的接枝率更高。将柠檬酸改性的n-HA与聚乳酸（PLA）共混制备复合材料,通过SEM观察发现,制备的n-HA/PLA复合材料在n-HA粉体添加量不超过20wt%时,经处理后的n-HA粉体在基体中分散均匀,两相界面处结合紧密。同时研究了n-HA/PLA复合材料制备多孔骨支架的3D打印成型工艺,并测试了其力学性能,结果表明,采用熔融沉积3D打印技术制备的支架有良好的压缩模量,但达到10%形变时所承受的压缩强度与PLA相比仍然有一定差距。     

聚乙烯醇/聚丙烯酸/羟基磷灰石复合高吸水性树脂的制备及溶胀行为

以聚乙烯醇(PVA)、部分中和的丙烯酸(AA)和羟基磷灰石(HA)为原料,过硫酸铵(APS)为引发剂,N,N′-亚甲基双丙烯酰胺(MBA)为交联剂,采用水溶液聚合法制备了聚乙烯醇/聚丙烯酸/羟基磷灰石(PVA/PAA/HA)复合高吸水树脂。考察了PVA用量对吸水性能的影响,研究了树脂在不同pH值溶液和不同阳离子盐溶液中的溶胀行为。结果表明,引入适量的PVA有利于树脂吸水性能的改善;树脂在pH=4～11较宽的范围内都能保持较高的吸水倍率,在CaCl2溶液中的溶胀动力学行为表现出明显的"过溶胀平衡现象"。     

氨基酸/羟基磷灰石复合材料应用于酸蚀牛牙釉质体外再矿化

早期牙釉质龋病的再矿化在龋齿的预防和修复中起着至关重要的作用。基于牙釉质基质中所含的主要氨基酸, 在10 mmol/L甘氨酸、10 mmol/L L-丝氨酸和5 mmol/L L-天冬氨酸的存在下制备了氨基酸/羟基磷灰石(AA/HAP)复合材料, 表征了其物理、化学和生物学性质, 并评估了其对酸蚀牛牙釉质的再矿化作用。与不含氨基酸的羟基磷灰石(HAP)相比, 在氨基酸的抑制作用下, AA/HAP复合材料具有更低的结晶度和更高的生物相容性。在人工唾液中用AA/HAP对酸蚀牛牙釉质进行体外再矿化。再矿化后, 分别表征了牛牙釉质样品的表面和横截面形态、成分和力学性能。结果表明, AA/HAP可以诱导表面和深层牙釉质病变的修复。复合材料中释放的氨基酸可以吸附在有机基质残基上并诱导平行排列的HAP晶体的形成, 从而使牙釉质表面显微硬度(SMH)得到显著恢复。最后, 讨论了AA/HAP复合材料对酸蚀牛牙釉质的再矿化机制。     

聚乳酸木塑复合材料的增韧及结晶性能

选用不同弹性体乙烯-醋酸乙烯共聚物(EVA)、马来酸酐接枝乙烯辛烯共聚物(POE-MAH)、甲基丙烯酸缩水甘油酯接枝乙烯辛烯共聚物(POE-GMA)与木粉和聚乳酸在Haake转矩流变仪中熔融共混,考察弹性体对聚乳酸木塑复合材料冲击强度的影响,发现POE-GMA对聚乳酸木塑复合材料的增韧效果最好,研究了POE-GMA的用...     

Preparation and in vitro bioactivity of poly(d,l-lactide) composite containing hydroxyapatite nanocrystals

The nano-sized hydroxyapatite (n-HA) was incorporated into poly(d,l-Lactide) (PDLLA) to form a bioactive and biodegradable composite for application in hard tissue replacement and regeneration. Thin film of PDLLA composite containing 20 mass% of n-HA fillers was successfully developed through integration of solvent co-blending and hot pressing techniques. firstly, n-HA and PDLLA were chemically synthesized, respectively, then mixed together and homogeneously dispersed in N,N-dimethyl formamide(DMF) solvent, finally, the dried blended hybrid containing PDLLA matrix and n-HA fillers was put into the mould and compacted by hot-pressing machine under 8 MPa pressure at 110 °C for 15 min. In vitro studies were conducted using the simulated body fluid(SBF). Composite specimens were soaked in SBF from 1 day to 21 days prior to surface analysis. Results obtained from scanning electron microscopy(SEM) examination, Energy dispersive X-ray detector(EDX) analysis and X-ray diffraction (XRD) analysis showed that a layer of non-stoichiometric apatite formed within 7 days on HA/PDLLA composite surface after its immersion in SBF, demonstrating moderate in vitro bioactivity of n-HA/PDLLA composite, though a moderate rate of apatite formation in SBF was found on initial stage of immersion periods for n-HA/PDLLA composite, compared to the other biomaterial composite. This type of composite film exhibited certain desirable bioactive characteristics, and they are promising bone candidates to develop novel bioactive composites for biomedical application.