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Two types of random copolymer poly(d-lactide-co-ε-caprolactone) (PDLA-r-PCL) were added into poly(l-lactide) (PLLA) matrix by melt blending. The structure and property of PLLA/PDLA-r-PCL blends were investigated by thermal gravimetric analysis, differential scanning calorimetry, scanning electron microscopy, wide-angle X-ray diffraction, and mechanical measurement. The results suggested that PDLA-r-PCL had little effect on the thermal property of PLLA. PDLA-r-PCL uniformly dispersed in PLLA matrix, which contributed to the improvement of stretching properties. During stretching at 25°C, with the increased content of PDLA-r-PCL, the elongation at break of PLLA increased and the strength decreased. The degree of decrease in fracture strength was related to the molecular structure of PDLA-r-PCL. When a small amount of stereocomplex crystals (SC) were formed in PLLA/PDLA-r-PCL blends, the strength was maintained or slightly enhanced even though the elongation at break of the blends was significantly improved by soft chains of PCL. It might be caused by the synergistic effects of SC crystals and plasticization of PCL chains.

We studied human bone healing characteristics and the histological osteogenic environment by using devices made of a composite of uncalcined and unsintered hydroxyapatite (u-HA) and poly-L-lactide (PLLA). In eight cases of fixation, we used u-HA/PLLA screws for maxillary alveolar ridge augmentation, for which mandibular cortical bone block was used in preimplantation surgery. Five appropriate samples with screws were evaluated histologically and immunohistochemically for runt-related transcription factor 2 (RUNX2), transcription factor Sp7 (Osterix), and leptin receptor (LepR). In all cases, histological evaluation revealed that bone components had completely surrounded the u-HA/PLLA screws, and the bone was connected directly to the biomaterial. Inflammatory cells did not invade the space between the bone and the u-HA/PLLA screw. Immunohistochemical evaluation revealed that many cells were positive for RUNX2 or Osterix, which are markers for osteoblast and osteoprogenitor cells, in the tissues surrounding u-HA/PLLA. In addition, many bone marrow&ndash, derived mesenchymal stem cells were notably positive for both LepR and RUNX2. The u-HA/PLLA material showed excellent bioactive osteoconductivity and a highly biocompatibility with bone directly attached. In addition, our findings suggest that many bone marrow&ndash, derived mesenchymal stem cells and mature osteoblast are present in the osteogenic environment created with u-HA/PLLA screws and that this environment is suitable for osteogenesis.

This research focuses on the crystallizability and melt flow property of linear poly(L-lactide) (1-PLL) by blending with star-shaped 16-arm PLL (16-PLL). The 1-PLL/16-PLL blends were chain extended during melt blending using an epoxy-based chain extender. The crystallinities of the 1-PLL/16-PLL blends increased with the 16-PLL blend ratio and chain extension reaction. The 16-PLL enhanced formation of branched PLL during chain extension was confirmed by thermogravimetry, and improved the melt flow property of the blends. Stresses at break of the compressed blend films were improved slightly by the 16-PLL blending and chain extension. In conclusion, the 16-PLL could be used as a nucleating agent and a melt strength enhancer for linear PLL.

We demonstrated a novel strategy to toughen poly(l-lactide) (PLLA) by constructing pseudo-cross-link networks based on chain entanglements of long-chain branched structure in the toughening phase, which were anchored by stereocomplex (SC) crystallites at the interface. The formation of pseudo-cross-link network was achieved by simple blending of the copolymer of long-chain branched polycaprolactone and poly(d-lactide) (LB-PCL- b-DLA) with PLLA without introducing any chemical cross-linking structure or nonbiodegradable component. The microscopic morphology analysis suggests that the interface-formed SC crystallites not only enhanced the interfacial interaction between LB-PCL and PLLA but also obviously increased the matrix crystallization rate. Different from those blends without SC crystallites or long-chain branched structures, nano-microgels were observed in chloroform solution of the PLLA/LB-PCL- b-DLA blend, suggesting the formation of pseudo-cross-link network. The pseudo-cross-link network in LB-PCL toughening phase endows PLLA a significantly improved impact toughness (49.5 kJ/m

Summary Introduction Bone defect reconstruction in orbital wall fractures with absorbable alloplastic such as the unsintered hydroxyapatite and poly L-lactide composite (u-HA/PLLA) system is gaining popularity. The u-HA/PLLA material has osteoconductive and osteosynthetic properties. However, quantitative, long-term outcome data after the use of u-HA/PLLA for orbital wall fractures are lacking. Patients and Methods We retrospectively analyzed 115 patients who underwent surgical repair of orbital wall fractures with a u-HA/PLLA sheet from 2011 to 2016. A chart review was performed, and the time-dependent changes at fracture sites were assessed by imaging. The immediate postoperative and the latest follow-up bony orbital volumes of the affected side were compared. Results Seventy patients were eligible for this study (mean age, 44.6 ± 22.1 years; 48 men and 22 women; mean follow-up period, 29.7 ± 12.8 months). Except for one case of hematoma, there were no postoperative wound complications. Of the 70 patients, 10 had postoperative diplopia and 2 had enophthalmos; these conditions were presumably caused by the extension and severity of the fracture. Satisfactory reduction in the entire orbital wall, without pathological changes, was demonstrated. There were no significant differences in the mean bony orbital volumes of the affected side immediately after surgery (24.774 ± 3.092 cm3) and at the latest follow-up (24.749 ± 3.205 cm3) (p = 0.756). Conclusion The u-HA/PLLA sheet is useful for orbital wall fracture reconstruction because of its desirable handling characteristics, initial mechanical strength, long-term maintenance of structural stability, radiopacity, and few associated complications. Future randomized controlled trials need to be performed to compare u-HA/PLLA with other conventional materials.

Two types of poly(glycerol sebacate) (PGS) prepolymers were synthesized and electrospun with poly(l-lactic acid) (PLA), resulting in bicomponent nonwovens. The obtained materials were pre-heated in a vacuum, at different times, to crosslink PGS and investigate morphological and structural dependencies in that polymeric, electrospun system. As both PGS and PLA are sensitive to pre-heating (crosslinking) conditions, research concerns both components. More interest is focused on the properties of PGS, considering further research for mechanical properties and subsequent experiments with PGS synthesis. Electrospinning of PGS blended with PLA does not bring difficulties, but obtaining elastomeric properties of nonwovens is problematic. Even though PGS has many potential advantages over other polyesters when soft tissue engineering is considered, its full utilization via the electrospinning process is much harder in practice. Further investigations are ongoing, especially with the promising PGS prepolymer with a higher esterification degree and its variations.

This work reports on the impact of delaminated boron nitride nanosheets (BNNSs) on the crystallization behavior and crystalline structure of melt-crystallized poly-L-lactic acid (PLLA). Wide-angle X-ray diffraction and scanning electron microscopy data revealed that the addition of lower loadings of BNNSs (∼0.5 wt %) resulted in the highly dispersed PLLA nanocomposites, whereas the higher loading of BNNSs (≥1 wt %) leads to the agglomerated nanocomposites. It is shown that the presence of lower loadings of the BNNSs (∼0.5 wt %) induces the formation of ordered α form when crystallizing from the melt at a cooling rate of 10 °C/min, but the mixture of α' and α forms is formed in the presence of higher loading of BNNSs (≥1 wt %). Polarized optical microscopy images revealed that the crystallization rate of PLLA was significantly enhanced in the presence of lower loading of BNNSs (∼0.5 wt %) as corroborated by the increasing number of tiny spherulites. The strong interaction between the highly dispersed BNNSs and PLLA chains induces the conformationally ordered α form, and the various experimental techniques revealed that crystallization of PLLA occurred rapidly with the narrow distribution of crystal size and degree of crystal perfection in highly dispersed nanocomposites. Furthermore, the thermal conductivity of PLLA/BNNSs nanocomposites was found to increase significantly with BNNSs loading.

The growth rate of PCL spherulites is almost independent of the PLLA content while the band spacing of PCL spherulites decreases monotonically with increasing PLLA content.

Introduction: Axonal regeneration after a sectioning lesion is variable and depends on the environmental conditions of the two end points. An important enzymatic action and an immune response occur at this point. The Schwann cell at the end of the proximal segment starts a rapid mitotic division in an attemptto locate the target tissue for the severed neuron. The capacity for axonal regeneration after a sectioning lesion is variable and depends on the environmental conditions of the two end points. Objective: To insulate the region of nerve regeneration from biological activities coming from foreign tissues, reducing the immune and enzymatic response and improving the healing conditions of the two end points. Methods: The sciatic nerves of the right paw of twenty WISTAR EPM rats were sectioned, with a gap of 5 to 8mm.In ten animals a 20mm Poly-L Lactide-Co P-Lactide tube involved both sectioned extremities,without nerve suture. After 6 months the animals were sacrificed, the nerve was dissected and photographed. The distal muscles of the paw were sent to histological examination. Results: All animals in which entubulation with Poly-L Lactide- Co P-Lactide was performed demonstrated an excellent nerveregeneration. Histological examination demonstrated complete muscle regeneration. In the animals not submitted to nerve entubulation no nerve regeneration was demonstrated and histological examination demonstrated severe muscle atrophy. Conclusions: Poly-L Lactide-Co P-Lactide entubulationdemonstrated satisfactory nerve regeneration without nerve suture after six months spam. Paw innervated muscles did not show any histological atrophic characteristics.

Sequential addition of L -lactide (LA) followed by e-caprolactone (CL), and simultaneous addition of both monomers, afforded random LA/CL copolymers in the presence of lanthanide aryloxides under mild conditions. Transesterification was proved to play a predominant role in random copolymer formation. Moreover, treatment of poly( L -lactide) with e-CL led to random copolymer formation, which provides a new strategy not only to prepare random LA/CL copolymers, but also to directly modify PLLA.

One-hundred percent stereo-complexation in poly(l-lactide) (PLLA)/poly(d-lactide) (PDLA) fibers with non-equivalent molecular weights could be achieved via thermal treatment. Stereo-complexed polylactide (sc-PLA) fibers exhibited excellent hydrolysis resistance and thermal resistance. Till now, preparation of sc-PLA fibers with satisfactory qualities required both PLLA and PDLA with equivalently high molecular weights. Moreover, the high-molecular-weight PDLAs are expensive, restricting industrial-scale production and applications of sc-PLA products. In this study, equal-weight mixtures of low-molecular-weight PDLA (L-PDLA) and high-molecular-weight PLLA (H-PLLA) were melt spun into sc-PLA fibers and then completely stereo-complexed via thermal treatment. The hydrolysis resistance of L3/D1 fibers [PLLA (Mv = 3.0 × 105)/PDLA (Mv = 1.0 × 105)] was similar to that of L3/D3 fibers [PLLA (Mv = 3.0 × 105)/PDLA (Mv = 3.2 × 105)], but much higher than that of L3 fibers [PLLA (Mv = 3.0 × 105)]. Melting temperature and softening temperature of L3/D1 fibers (223 and 126 °C) were also similar to those of L3/D3 fibers (224 and 131 °C), but higher than that of L3 fibers (172 and 72 °C). Utilizing H-PLLA and L-PDLA to prepare sc-PLA fibers with excellent performance is conducive to the wide industrial application of sc-PLA.

In this research, poly(L-lactide) (PLLA) biocompatible and biodegradable polymer constructs were reinforced with functionalized multiwalled carbon nanotubes (MWCNTs) to overcome on insufficient mechanical properties of this polymer for high load bearing applications. To fully realize the potential of MWCNTs and have an efficient load transfer across the MWCNTs/polymer interface, PLLA chains grafted on the sidewall of aminated MWCNTs (MWCNT-g-PLLAs). The analysis results showed that the in vitro biodegradation of MWCNT-g-PLLAs/PLLA nanocomposites in PBS increased gradually with increasing the concentration of MWCNT-g-PLLAs in the composites. Additionally, the glass transition temperature of composites increased with increment the concentration of functionalized MWCNTs. The biodegradation kinetics of nanocomposites can be engineered and functionalized by varying the concentration of functionalized MWCNTs.

Bio-based blend nanocomposites of poly(L-lactic acid) (PLLA) and poly(butylene succinate) (PBS), with different concentrations (from 0.1 to 0.5 wt%) of graphene oxide (GO), are prepared via solution dispersion of PBS/GO followed by melt blending with PLLA in a 70/30 PLLA/PBS weight ratio. Scanning and Transmission Electron Microscopy reveals micron-sized droplets of PBS in the PLLA matrix with the GO nanofiller preferentially found in the PBS phase. The GO acts as nucleating agent for both semicrystalline polymers. The nanofiller nucleating effect is compared to the one of own selfnuclei for each polymer, to define a convenient nucleating efficiency (NE) scale. A value of around 80% is determined for GO towards PBS, among the highest NEs ever reported for this polymer. On the other hand, the efficiency in nucleating PLLA is equal to a modest 15%, also due to the uneven distribution of the nanofiller in the two polymers. A close relationship between the nanocomposite morphology and crystallization behavior of the two different polymers is thus established.

The preparation of block copolymers containing poly(γ-butyrolactone) blocks remains a synthetic challenge owing to the unfavorable thermodynamics towards the ring-opening polymerization (ROP) of non-strained five-membered rings that makes them prone to copolymerization with other cyclic lactones or lactides rather than the formation of homopolymers. By choosing a suitable organophosphazene superbase as a catalyst, we realized the successful one-pot preparation of poly(γ-butyrolactone)-b-poly(L-lactide) by sequential ROP of γBL and L-LA for the first time. The thermal stabilities, crystallization, and melting behaviors of the obtained diblock copolyesters were also investigated.

The aim of this study was to assess compositional changes in a forged-unsintered hydroxyapatite and poly-L-lactide (uHA/PLLA) mesh at 651 days after insertion into human body.A 35-year-old female patient had left tripod fracture, orbital medial wall and floor fracture, and superficial lateral palpebral ligament rupture. On the 9th posttrauma day, the tripod fracture was reduced and fixed with plates, and the orbital wall and floor were reconstructed with a resorbable mesh. The floor and medial wall were reconstructed with a trimmed mesh made of uHA/PLLA (Osterotrans-MX; Takiron Co, Umeda, Japan). On postoperative day 620, she complained of enophthalmos of left eye (right eye, 18 mm; left eye, 16 mm). Secondary reconstruction of the orbital floor was performed with an iliac bone graft 651 days after insertion. During the secondary operation, the uHA/PLLA mesh that had been previously inserted was removed. The mesh was removed and analyzed using gel permeation chromatography (GPC) and Fourier transform infrared spectroscopy (FTIR).The GPC revealed that the weight average molecular weight (Mw) decreased from 542,000 to 83,300 Da and the number average molecular weight (Mn) decreased from 124,000 to 20,200 Da in the specimen from the operation. In the postinsertion FTIR spectrum, weak 1648.6 and 1656.1/cm peaks newly appeared. The strong 1038/cm peak of the initial specimen changed slightly into a less strong 1041.8/cm peak.In conclusion, the reduced Mw and Mn in the postinsertion specimen suggest that uHA/PLLA has one of the favorable degradation properties. The newly appeared bands are thought to be carbon-carbon double bonds of alkenes.

Recently, various tissue engineering based strategies have been pursued for the regeneration of tracheal tissues. However, previously developed tracheal scaffolds do not accurately mimic the microstructure and mechanical behavior of the native trachea, which restrict their clinical translation. Here, we fabricate tracheal scaffolds by using three-dimensional printing and short nanofibers (SF) dispersion of poly(L-lactide)/gelatin (0.5-1.5 wt%) to afford tracheal constructs. The results display that the scaffolds containing 1.0 wt % of SF exhibit low density, good water absorption capacity, reasonable degradation rate, and stable mechanical properties, which were comparable to the native trachea. Moreover, the designed scaffolds possess good biocompatibility and promote the growth and infiltration of chondrocytes in vitro. The biocompatibility of tracheal scaffolds is further assessed after subcutaneous implantation in mice for up to 4 and 8 weeks. Histological assessment of tracheal constructs explanted at week 4 shows that scaffolds can maintain their structural integrity and support the formation of neo-vessels. Furthermore, cell-scaffold constructs gradually form cartilage-like tissues, which mature with time. Collectively, these engineered tracheal scaffolds not only possess appropriate mechanical properties to afford a stabilized structure but also a biomimetic extracellular matrix-like structure to accomplish tissue regeneration, which may have broad implications for tracheal regeneration. This article is protected by copyright. All rights reserved.

An innovative eccentric rotor extruder (ERE), which can generate continuous elongation flow, was used to prepare the poly(L-lactide) (PLLA)/poly(ethylene glycol) (PEG)/organo-modified montmorillonite (OMMT) nanocomposites. The morphology was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), and showed that the OMMT nanoparticles were uniformly dispersed in the matrix and mainly existed in intercalation mode. The influence of OMMT on the rheological behavior of plasticized PLLA was investigated by dynamic rheological measurements, showing greater improvement of rheological properties compared to that of PLLA/PEG blend. The crystallization behavior and crystalline structures were studied by differential scanning calorimetry (DSC) and XRD, respectively, and showed that the presence of OMMT further speeds up the crystallization rate of plasticized PLLA. However, the crystallization rate and crystallinity had a slight downward trend at high OMMT content because of the inhibition effect of the OMMT percolation network structure. Polarizing optical microscopy (POM) was further carried out and proved that the OMMT nanoparticles as a heterogeneous nucleating agent can increase the spherulite growth rate and nucleation density. The thermal stability was investigated by thermogravimetric analysis and indicated that the addition of OMMT at low concentration can improve the thermal stability of plasticized PLLA more effectively.

Functionalized eggshell powder (NES) with nucleating surface of calcium phenylphosphonic acid (PPCa) for poly(l-lactide) (PLLA) was compounded with PLLA via melt blending to improve the cold crystallization process of PLLA. The cold crystallization behavior of the PLLA/NES composites was studied by differential scanning calorimetry. The isothermal cold crystallization rates have been enhanced obviously in the PLLA/NES composites than in the neat PLLA, indicative of the excellent nucleating effects of NES on PLLA. For the nonisothermal cold crystallization, the overall crystallization rate of PLLA increased with both increasing NES loadings and heating rate. It was found that the Avrami equation and the combined Ozawa–Avrami model could describe the experiment data successfully.

Antibacterial property for scaffolds is an urgent problem to prevent infections in bone repair. Ag nanoparticles possess excellent bactericidal activities, whereas their agglomeration restricts the full play of antibacterial property in scaffold. Herein, a mace-like nanosystem was constructed to improve their dispersion by in-situ growth of Ag nanoparticles on cellulose nanocrystal (CNC), which was labeled CNC@Ag nanosystem. Subsequently, the CNC@Ag nanosystem was introduced into poly-L-lactide (PLLA) scaffolds. Results demonstrated that the nanosystem uniformly dispersed in scaffold. The antibacterial tests demonstrated that the scaffolds possessed robust antibacterial activities against E. coli, with bacterial inhibition rate over 95%. Moreover, ion release behavior corroborated the scaffolds continuously released Ag+ for more than 28 days, which benefited from the immobilization effect of CNC on Ag. Encouragingly, the mechanical properties of the scaffolds were remarkably higher than that of PLLA/CNC scaffolds, owing to the mace-like CNC@Ag nanosystem improved the load transfer efficiency in the scaffold.