Pure Poly L-lactic Acid Research Articles

Comparison of Different Types of Poly-L-lactic Acid Microspheres In Vitro and In Vivo Studies

Abstract Background Biodegradable polymers are commonly used as dermal fillers in plastic surgery. Among these, poly-L-lactic acid (PLLA) distinguishes itself owing to its good biocompatibility, degradability, and ability to act as a collagen stimulator. Objectives In this study, the differential behavior of PLLA microspheres with varying microscopic morphology and surface hydrophilicity was investigated both in vitro and in vivo. Methods The introduction of short hydrophilic polyethylene glycol (PEG) chains into the PLLA molecule was employed to modify the morphology and enhance the surface hydrophilicity of the microspheres. The morphology and physicochemical properties of the PLLA and PLLA-b-PEG microspheres were characterized. Irregular PLLA particles, PLLA and PLLA-b-PEG microspheres were implanted into the subcutaneous tissue of rabbit models, and at 4, 26 and 52 weeks after implantation, biopsy samples were collected for hematoxylin and eosin (H&E) and Masson's trichrome staining to evaluate differences in the tissue response between different implants. Results The results of in vitro research demonstrated that while the addition of short-chain hydrophilic PEG afforded a smoother surface for the microspheres, it had no significant effect on the molecular weight and degradation rate of PLLA. The histological examination revealed that the PLLA-b-PEG microspheres exhibited enhanced biocompatibility compared to the pure PLLA microspheres, while the irregular PLLA particles showed the highest inflammatory response among the three materials. Conclusions In this study, we found that the properties of PLLA were improved upon modification by short-chain PEG without reducing the collagen regeneration ability, thereby affording a better histocompatibility.

Constructing high-strength nano-micro fibrous woven scaffolds with native-like anisotropic structure and immunoregulatory function for tendon repair and regeneration

Tendon injuries are common debilitating musculoskeletal diseases with high treatment expenditure in sports medicine. The development of tendon-biomimetic scaffolds may be promising for improving the unsatisfactory clinical outcomes of traditional therapies. In this study, we combined an advanced electrospun nanofiber yarn-generating technique with a traditional textile manufacturing strategy to fabricate innovative nano-micro fibrous woven scaffolds with tendon-like anisotropic structure and high-strength mechanical properties for the treatment of large-size tendon injury. Electrospun nanofiber yarns made from pure poly L-lactic acid (PLLA) or silk fibroin (SF)/PLLA blend were fabricated, and their mechanical properties matched and even exceeded those of commercial PLLA microfiber yarns. The PLLA or SF/PLLA nanofiber yarns were then employed as weft yarns interlaced with commercial PLLA microfiber yarns as warp yarns to generate two new types of nanofibrous scaffolds (nmPLLA and nmSF/PLLA) with a plain-weaving structure. Woven scaffolds made from pure PLLA microfiber yarns (both weft and warp directions) (mmPLLA) were used as controls. In vitro experiments showed that the nmSF/PLLA woven scaffold with aligned fibrous topography significantly promoted cell adhesion, elongation, proliferation, and phenotypic maintenance of tenocytes compared with mmPLLA and nmPLLA woven scaffolds. Moreover, the nmSF/PLLA woven scaffold exhibited the strongest immunoregulatory functions and effectively modulated macrophages towards the M2 phenotype. In vivo experiments revealed that the nmSF/PLLA woven scaffold notably facilitated Achilles tendon regeneration with improved structure by macroscopic, histological, and ultrastructural observations six months after surgery, compared with the other two groups. More importantly, the regenerated tissue in the nmSF/PLLA group had excellent biomechanical properties comparable to those of the native tendon. Overall, our study provides an innovative biological-free strategy with ready-to-use features, which presents great potential for clinical translation for damaged tendon repair.

In situ synthesis of hydroxyapatite nanorods on graphene oxide nanosheets and their reinforcement in biopolymer scaffold

IntroductionIt is urgently needed to develop composite bone scaffold with excellent mechanical properties and bioactivity in bone tissue engineering. Combining graphene oxide (GO) and hydroxyapatite (HAP) for the reinforcement of biopolymer bone scaffold has emerged as a promising strategy. However, the dispersion of GO and HAP remains to be a big challenge. ObjectivesIn this present work, the mechanical properties of GO and the bioactivity of and HAP were combined respectively via in situ synthesis for reinforcing biopolymer bone scaffold. MethodsGO nanosheets were employed to in situ synthesize GO-HAP nanocomposite via hydrothermal reaction, in which their abundant oxygen-containing groups served as anchor sites for the chelation of Ca2+ and then Ca2+ absorbed HPO42- via electrovalent bonding to form homogeneously dispersed HAP nanorods. Thereby, the GO-HAP nanocomposite was blended with biopolymer poly-L-lactic acid (PLLA) for fabricating biopolymer scaffold by selective laser sintering (SLS). ResultsGO nanosheets were uniformly decorated with HAP nanorods, which were about 60 nm in length and 5 nm in diameter. The compressive strength and modulus of PLLA/12%GO-HAP were significantly increased by 53.71% and 98.80% compared to the pure PLLA scaffold, respectively, explained on the base of pull out, crack bridging, deflection and pinning mechanisms. Meanwhile, the mineralization experiments indicated the PLLA/GO-HAP scaffold displayed good bioactivity by inducing the formation of apatite layer. Besides, cell culturing experiments demonstrated the favorable cytocompatibility of scaffold by promoting cell adhesion and proliferation. ConclusionsThe present findings show the potential of PLLA/GO-HAP composite scaffold via in situ synthesis in bone tissue engineering.

Enhanced Bioactivity of Micropatterned Hydroxyapatite Embedded Poly(L-lactic) Acid for a Load-Bearing Implant.

Poly(L-lactic) acid (PLLA) is among the most promising polymers for bone fixation, repair, and tissue engineering due to its biodegradability and relatively good mechanical strength. Despite these beneficial characteristics, its poor bioactivity often requires incorporation of bioactive ceramic materials. A bioresorbable composite made of PLLA and hydroxyapatite (HA) may improve biocompatibility but typically causes deterioration in mechanical properties, and bioactive coatings inevitably carry a risk of coating delamination. Therefore, in this study, we embedded micropatterned HA on the surface of PLLA to improve bioactivity while eliminating the risk of HA delamination. An HA pattern was successfully embedded in a PLLA matrix without degeneration of the matrix’s mechanical properties, thanks to a transfer technique involving conversion of Mg to HA. Furthermore, patterned HA/PLLA’s biological response outperformed that of pure PLLA. These results confirm patterned HA/PLLA as a candidate for wide acceptance in biodegradable load-bearing implant applications.

Acceleration of crystallisation rate in injection moulded PLLA by stereocomplex formation

An experimental study has been performed to examine the crystallisation rate of poly(L)lactic acid (PLLA) blended with poly(D) lactic acid (PDLA) in order to reduce injection moulding cycle time. Optically pure PLLA was melt blended with up to 15wt% of its enantiomer PDLA in a twin screw extruder. Flow properties, melt strength and thermal properties of the blends were assessed. PLLA/PDLA blends were then injection moulded and allowed to crystallise using two different methods, either non-isothermally in a high temperature injection mould tool or isothermally by annealing moulded samples in a hot oven after conventional injection moulding. Mechanical and thermomechanical properties of the moulded samples were investigated and optical measurement of crystal formation using polarised light microscopy was performed at conditions representative of both crystallisation methods. Addition of PDLA was found to accelerate crystallisation rate by up to 80% and the resulting morphology demonstrated increased heat resistance, melt strength and stiffness, with a corresponding reduction in strain at break.

Comparing the regeneration potential between PLLA/Aragonite and PLLA/Vaterite pearl composite scaffolds in rabbit radius segmental bone defects

Mussel-derived nacre and pearl, which are natural composites composed CaCO3 platelets and interplatelet organic matrix, have recently gained interest due to their osteogenic potential. The crystal form of CaCO3 could be either aragonite or vaterite depending on the characteristics of mineralization template within pearls. So far, little attention has been paid on the different osteogenic capacities between aragonite and vaterite pearl. In the current work, aragonite or vaterite pearl powders were incorporated into poly-l-lactic acid (PLLA) scaffold as bio-functional fillers for enhanced osteogenesis. In intro results revealed that PLLA/aragonite scaffold possessed stronger stimulatory effect on SaOS-2 cell proliferation and differentiation, evidenced by the enhanced cell viability, alkaline phosphatase activity, collagen synthesis and gene expressions of osteogenic markers including osteocalcin, osteopotin and bone sialoprotein. The bone regeneration potential of various scaffolds was evaluated in vivo employing a rabbit critical-sized radial bone defect model. The X-ray and micro-CT results showed that significant bone regeneration and bridging were achieved in defects implanted with composite scaffolds, while less bone formation and non-bridging were found for pure PLLA group. Histological evaluation using Masson's trichrome and hematoxylin/eosin (H&E) staining indicated a typical endochondral bone formation process conducted at defect sites treated with composite scaffolds. Through three-point bending test, the limbs implanted with PLLA/aragonite scaffold were found to bear significantly higher bending load compared to other two groups. Together, it is suggested that aragonite pearl has superior osteogenic capacity over vaterite pearl and PLLA/aragonite scaffold can be employed as a potential bone graft for bone regeneration.

Physico-chemical and biological properties of electrospun poly-L-lactic acid/hydroxyapatite nano-composite scaffold for bone regeneration

The main goal of tissue engineering is to design scaffolds with the suitable microenvironment, prominent mechanical properties, adequate biocompatibility, and biodegradability. In the present study, Poly-L-lactic acid (PLLA)/10% hydroxyapatite (HA) nano-composite (PLLA/HA) scaffold and pure PLLA scaffold were fabricated via electrospinning technique. They were then assessed for their potential as substrates for the cell culture. The scaffolds were characterized by scanning electron microscope, thermogravimetric analysis, differential thermal analysis, and fourier transform infrared spectroscopy. The results showed the dispersion and integration of HA nanoparticles in the composite scaffold. Pore size distribution measurements indicated that the scaffold pore size in terms of Ferret diameter varies between 0.1 and 22.0 µm. In vitro degradation behavior of the scaffold in phosphate buffered saline (PBS) was obtained by measuring water uptake, weight loss, and pH change of the PBS during the degradation period. We observed that the degradation of the scaffold could be markedly accelerated by HA nanoparticle (10%). It was also shown that acidification of the PBS due to the PLLA degradation is suppressed by the HA nanoparticles. Finally, human umbilical-cord-derived mesenchymal stem cells (hUC-MSCs) were used to evaluate the cellular support of the composite scaffolds. The presence of HA nanoparticles in the PLLA fibrous scaffolds resulted in promoting the attachment and the proliferation of the hUC-MSCs. This study suggests that the PLLA/HA scaffold could be the material of choice for functional bone tissue engineering.

Fabrication and characterization of PLLA/Mg composite tube as the potential bioresorbable/biodegradable stent(BRS)

A deeper understanding is required to develop a bioresorbable stents (BRS) for cardiovascular diseases. In this work, the biodegradable composite tubes were produced by adding 2% and 4% w/w of Magnesium (Mg) microparticles with Poly-L-lactic acid (PLLA) to achieve synergism effect. Tubes of diameter 3 mm and thickness of 150 µm were fabricated through a biaxial extrusion (BAE) process. After that, BAE tubes were cut on the Femtosecond laser for making BRS.Mg microparticles were uniformly distributed and completely encapsulated within the PLLA matrix. The thermal analysis and XRD results indicate that Mg microparticles act as a nucleating agent and promotes the crystallinity to the matrix. FTIR analysis reveals the interfacial bonding between Mg and PLLA. Thus, Mg microparticles can act as a reinforcement to the matrix, which improves the toughness, compressive strength as well as ductility as compared to pure PLLA tubes. The degradation study was carried out to explore the effect of Mg as it effectively neutralizes the acidic by-product of PLLA. As a result, the alkaline nature of Mg stabilizes the pH of the body fluid and reduces tissue necrosis. In-vitro cytocompatibility test was performed by L929 fibroblasts cells to identify the potential application of PLLA/Mg composite BAE tubes as a BRS for the future.

Biodegradability and methane fermentability of polylactic acid by thermophilic methane fermentation

Polylactic acid (PLA) is considered to be a promising polymer to replace petroleum-based plastics. The aim of this study was to evaluate the biological decomposability of PLA by thermophilic methane fermentation (TMF) and to analyse the microorganisms involved in PLA decomposition. Small- and large-scale batch tests were carried out using disposable cutlery as PLA products and pure poly L-lactic acid (PLLA) pellets. It was found that 70–77% of PLA was decomposed by TMF, based on weight changes. The yield of CH4 was 321–343 mL CH4/g PLA consumed. The addition of bacteria doubled the physicochemical degradation rate of PLA. It was determined that PLA decomposition by TMF was efficient, and that it was enhanced by microbial activity. In particular, lactic acid-consuming bacteria were found to play an important role in PLA decomposition by TMF. Thus, we can conclude that TMF is potentially suitable for PLA treatment and biofuel generation.

Poly-l-lactic acid scaffold incorporated chitosan-coated mesoporous silica nanoparticles as pH-sensitive composite for enhanced osteogenic differentiation of human adipose tissue stem cells by dexamethasone delivery

Nowadays, the development of drug-loaded electrospun organic-inorganic composite scaffolds for tissue engineering application is an attractive approach. In this study, a composite scaffold of Poly-l-lactic acid (PLLA) incorporated dexamethasone (Dexa) loaded Mesoporous Silica Nanoparticles (MSN) coated with Chitosan (CS) were fabricated by electrospinning for bone tissue engineering application. The MSN was prepared by precipitation method. After that, Dexamethasone (Dexa) was loaded into MSNs (MSN-Dexa). In the following, CS was coated over the prepared nanoparticles to form MSN-Dexa@CS and then, were mixed to PLLA solution to form MSN-Dexa@CS/PLLA composite for electrospinning. The surface morphology, hydrophilicity, tensile strength and the bioactivity of the scaffolds were characterized. The osteogenic proliferation and differentiation potential were evaluated by MTT assay and by measuring the basic osteogenic markers: the activity of the enzyme alkaline phosphatase and the level of calcium deposition. The composite scaffolds prepared here have conductive surface property and have a better osteogenic potential than pure PLLA scaffolds. Hence, the controlled release of nanoparticle containing Dexa from composite scaffold supported the osteogenesis and made the composite scaffolds ideal candidates for bone tissue engineering application and pH-sensitive delivery of drugs at the site of implantation in tissue regeneration.

Bioactive and mechanically stable hydroxyapatite patterning for rapid endothelialization of artificial vascular graft

Polymeric vascular grafts have been widely used in the vascular regeneration field because of their ease of application. However, synthetic polymer grafts have the severe problem of low biocompatibility, which may cause delayed endothelialization and hyperplasia. In this study, we fabricated a linear hydroxyapatite (HA) pattern on a silicon wafer and then transferred the pattern to a poly(L-lactic)-acid (PLLA) film for use as a tubular vascular graft. The HA pattern with its characteristic needle-like shape was successfully embedded into the PLLA. The HA-patterned PLLA film exhibited superior mechanical stability compared with that of a HA-coated PLLA film under bending, elongation, and in vitro circulation conditions, suggesting its suitability for use as a tubular vascular graft. In addition, the HA pattern guided rapid endothelialization by promoting proliferation of endothelial cells and their migration along the pattern. The hemocompatibility of the HA-patterned PLLA was also confirmed, with substantially fewer platelets adhered on its surface. Overall, in addition to good mechanical stability, the HA-patterned PLLA exhibited enhanced biocompatibility and hemocompatibility compared with pure PLLA.

Enhanced osteogenic differentiation of mesenchymal stem cells on metal-organic framework based on copper, zinc, and imidazole coated poly-l-lactic acid nanofiber scaffolds.

The presence of inorganic bioactive minerals with polymers can accelerate and promote several processes including: bone cell joining, proliferation, differentiation, and expression of osteogenic proteins. In this study, zinc (Zn), copper (Cu), and imidazole metal-organic framework (MOF) nanoparticles were synthesized and coated over poly-l-lactic acid (PLLA) nanofibrous scaffolds for bone tissue engineering application. The surface and bioactive features of the scaffolds were characterized. The osteogenic potential of the scaffolds on human adipose tissue-derived mesenchymal stem cells (MSCs) was evaluated. Zn-Cu imidazole MOF coated PLLA scaffolds (PLLA@MOF) showed a comparable rate of MSC proliferation with the pure PLLA scaffolds and tissue culture plate (TCP). However, the PLLA@MOF potential of osteogenic differentiation was significantly greater than either pristine PLLA scaffolds or TCP. Hence, coating Zn-Cu imidazole MOF has a significant effect on the osteogenesis of MSC. Therefore, PLLA@MOF is novel scaffolds with bioactive components which are crucial for osteoconductivity and also able to provoke the osteogenesis and angiogenesis.

Mechanical Characterizations of 3D-printed PLLA/Steel Particle Composites.

The objective of this study is to characterize the micromechanical properties of poly-l-lactic acid (PLLA) composites reinforced by grade 420 stainless steel (SS) particles with a specific focus on the interphase properties. The specimens were manufactured using 3D printing techniques due to its many benefits, including high accuracy, cost effectiveness and customized geometry. The adopted fused filament fabrication resulted in a thin interphase layer with an average thickness of 3 µm. The mechanical properties of each phase, as well as the interphase, were characterized by nanoindentation tests. The effect of matrix degradation, i.e., imperfect bonding, on the elastic modulus of the composite was further examined by a representative volume element (RVE) model. The results showed that the interphase layer provided a smooth transition of elastic modulus from steel particles to the polymeric matrix. A 10% volume fraction of steel particles could enhance the elastic modulus of PLLA polymer by 31%. In addition, steel particles took 37% to 59% of the applied load with respect to the particle volume fraction. We found that degradation of the interphase reduced the elastic modulus of the composite by 70% and 7% under tensile and compressive loads, respectively. The shear modulus of the composite with 10% particles decreased by 36%, i.e., lower than pure PLLA, when debonding occurred.

Fabrication and In Vitro Characterization of a Tissue Engineered PCL-PLLA Heart Valve

Heart valve diseases are among the leading causes of cardiac failure around the globe. Nearly 90,000 heart valve replacements occur in the USA annually. Currently, available options for heart valve replacement include bioprosthetic and mechanical valves, both of which have severe limitations. Bioprosthetic valves can last for only 10–20 years while patients with mechanical valves always require blood-thinning medications throughout the remainder of the patient’s life. Tissue engineering has emerged as a promising solution for the development of a viable, biocompatible and durable heart valve; however, a human implantable tissue engineered heart valve is yet to be achieved. In this study, a tri-leaflet heart valve structure is developed using electrospun polycaprolactone (PCL) and poly L-lactic acid (PLLA) scaffolds, and a set of in vitro testing protocol has been developed for routine manufacturing of tissue engineered heart valves. Stress-strain curves were obtained for mechanical characterization of different valves. The performances of the developed valves were hemodynamically tested using a pulse duplicator, and an echocardiography machine. Results confirmed the superiority of the PCL-PLLA heart valve compared to pure PCL or pure PLLA. The developed in vitro test protocol involving pulse duplicator and echocardiography tests have enormous potential for routine application in tissue engineering of heart valves.

High-resolution x-ray tomographic morphological characterisation of electrospun nanofibrous bundles for tendon and ligament regeneration and replacement.

Repair of ligaments and tendons requires scaffolds mimicking the spatial organisation of collagen in the natural tissue. Electrospinning is a promising technique to produce nanofibres of both resorbable and biostable polymers with desired structural and morphological features. The aim of this study was to perform high-resolution x-ray tomography (XCT) scans of bundles of Nylon6.6, pure PLLA and PLLA-Collagen blends, where the nanofibres were meant to have a predominant direction. Characterisation was carried out via a dedicated methodology to firmly hold the specimen during the scan and a workflow to quantify the directionality of the nanofibres in the bundle. XCT scans with 0.4 and 1.0 μm voxel size were successfully collected for all bundle compositions. Better image quality was achieved for those bundles formed by thicker nanofibres (i.e. 0.59 μm for pure PLLA), whereas partial volume effect was more pronounced for thinner nanofibres (i.e. 0.26 μm for Nylon6.6). As expected, the nanofibres had a predominant orientation along the axis of the bundles (more than 20% of the nanofibres within 3° and more than 60% within 18° from the bundle axis), with a Gaussian-like dispersion in the other directions. The directionality assessment was validated by comparison against a similar analysis performed on SEM images: the XCT analysis overestimated the amount of nanofibres very close to the bundle axis, especially for the materials with thinnest nanofibres, but adequately identified the amount of nanofibres within 12°. LAY DESCRIPTION: Repair of ligaments and tendons requires dedicated materials (scaffolds) mimicking the spatial organisation of the collagen (the main material composing such natural tissue). Electrospinning is a promising technique that allows production of fibres with nanometric dimension using high voltage to stretch very tiny drops of polymeric solutions. Electrospinning allows processing both polymers that can be resorbed by the host tissue, and nonresorbable ones, to obtain the desired structural and morphological features by arranging the nanofibres in bundles. The aim of this study was to perform high-resolution x-ray computed tomography (XCT) scans of bundles, where the nanofibres were meant to have a predominant direction. The investigation included bundles of different compositions: a biostable polymer (Nylon) and bioresorbable ones (pure Poly-L-lactic acid (PLLA) and PLLA-Collagen blends). The electrospun bundles were produced using a validated method (Sensini et al 2017: https://doi.org/10.1088/1758-5090/aa6204). To this end, we developed a dedicated methodology to scan such small specimens, and a workflow to quantify the directionality of the nanofibres in the bundle. For all the compositions, XCT scans with extremely high resolution (i.e. down to 0.4 μm) were successfully collected. As expected, better images were obtained for those bundles where the nanofibres were thicker than the scanning resolution (i.e. 0.59 μm for pure PLLA). The images of the thinnest nanofibres (i.e. 0.26 μm for Nylon) were poorer because the fibre diameter was smaller than the resolution (partial volume effect). The nanofibres had a predominant orientation along the axis of the bundles (more than 60% of the nanofibres were within 18° from the bundle axis). The nanofibres had a Gaussian-like dispersion in the other directions. As this is the first time that XCT is used to quantify the directionality of this kind of bundles, the directionality assessment was further validated by comparison against a similar analysis performed on SEM images. Overall, this study has demonstrated the usefulness and reliability of using high-resolution x-ray computed tomography (XCT) scans to investigate the morphology of polymeric scaffolds made of electrospun nanofibres.

Co-existence effect of tricalcium phosphate and bioactive glass on biological and biodegradation characteristic of Poly L-Lactic Acid (PLLA) in trinary compositescaffold form.

The purpose of this study is to analyze the co-existence effect of 30 wt.% TCP-BG phases on degradation and precipitation behaviors of PLLA based composite scaffold in biological media. First, phase separation method was used to synthesize of the pure PLLA and the trinary composite scaffolds, and second they were immersed in SBF solution for 45 days. Subsequently, the degradation and precipitation characteristic were investigated by analyzing of pH value and weight changes of the immersed samples, the ability of biological products formation and the change of relative molecular weight of PLLA matrix as function of the degradation time. Finally, the experimental data of relative molecular weight change were verified by Han and Pan model and comparisons were made between them. Results have represented precipitation of huge amount of carbonate apatite on surface of the composite scaffold, and also the acidity of SBF media changes moderately which is prove better bioactivity properties compare to the pure PLLA scaffold. The results of comparison with the model point to quiet good agreement between them in early stage of degradation. So, the consequences suggest that the TCP-BG/PLLA composite scaffold have great potential to be applied in bone replacements or repairs.

Paradoxical tunnel enlargement after ACL reconstruction with hamstring autografts when using \u03b2-TCP containing interference screws for tibial aperture fixation- prospectively comparative study

BackgroundTibial aperture fixation with a bioabsorbable interference screw is a popular fixation method in anterior cruciate ligament reconstruction (ACLR). An interference screw containing β-tricalcium phosphate (β-TCP) to improve bony integration and biocompatibility was recently introduced. This study aims to compare the clinical outcomes and radiological results of tunnel enlargement effect between the 2 bioabsorbable fixative devices of pure poly-L-lactic acid (PLLA) interference screws and β-TCP-containing screws, for tibial interference fixation in ACLR using hamstring autografts.MethodsEighty consecutive patients who had undergone double-bundle ACLR between 2011 to 2012 were prospectively reviewed and randomly divided into two groups based on the type of tibial interference screw: 28 were assigned to the pure PLLA screw group (Group A), while the other 29 were assigned to the β-TCP-containing screw fixation group (Group B). Clinical evaluations and radiological analyses were conducted in both groups with a minimum 2- year follow-up.ResultsThere was no significant difference in subjective or objective clinical outcome between the 2 groups. In radiological analyses, the use of a β-TCP-containing screw reduced tunnel widening in the portion of the tunnel with screw engagement compared to the pure PLLA screw, while the use of a β-TCP-containing screw resulted in greater tunnel enlargement in the proximal portion of the tunnel without screw engagement than use of a pure PLLA screw.ConclusionUse of a β-TCP-containing interference screw in tibial aperture fixation reduced tunnel enlargement in the vicinity of the screw, whereas greater enlargement occurred proximal to the screw end relative to use of a pure PLLA interference screw. These paradoxical enlargements in use of β-TCP containing screws suggest that for reducing tunnel enlargement, the length of the interference screw should be as fit as possible with tunnel length in terms of using soft grafts.Level of Evidence: II, Prospectively comparative study.Trial registrationRetrospectively registered with ClinicalTrials.gov. (NCT02754674), Date of trial registration: February 10, 2016.

Nanofibrous Scaffolds for Tissue Engineering Applications

The discipline of tissue engineering opens up the ways for repair and regenerate damaged organs and tissues. In the current work biomimetic nanofibrous scaffolds were fabricated by electrospinning. Poly-L-lactic acid (PLLA) was blended with collagen and gelatin to fabricate PLLLA-collagen and PLLA-gelatin fibrous scaffolds respectively. Pure PLLA and gelatin scaffolds served as controls. All the scaffolds displayed randomly oriented smooth fibers studied by SEM. Surface topography and roughness were studied by AFM and surface contact angle was also measured for all the fabricated scaffolds. Surface roughness was found to be higher in collagen and gelatin blended scaffolds in comparison to PLLA scaffold. Blending of collagen and gelatin reduced the surface hydrophobicity of the scaffolds. Human osteosarcoma cell lines MG-63 were cultured on all scaffolds up to 7 days and cell adhesion was studied through SEM and confocal microscopy. SEM and confocal results showed that gelatin blended PLLA scaffold showed better cell attachment and cell spreading.

Electrospinning 3D Scaffolds for use in Neural Tissue Engineering

ABSTRACTPolymer nanofiber scaffolds for use in neural tissue engineering have been fabricated via electrospinning of poly-L-lactic acid (PLLA) directly onto a 3D printed support. Previously, the investigators have shown success in promoting the directed growth of neural axons on highly aligned PLLA substrates both in vitro and in vivo. However, one criticism of the earlier in vitro studies is that by spinning fibers on a flat, two-dimensional surface, the growth of the axons is restricted to one plane. Thus the axon-to-fiber attachment may not be the sole mechanism for aligning the growth of the axons along the fibers, and the channels between the fibers and the substrate could contribute to the results. Using 3D-printing, elevated or “bridge” spinning stages were made with supports at varying heights, allowing the fibers to be suspended 2 to 5 mm above the substrate surface in different configurations. This 3D structure promotes better access of in vitro cell cultures on the fibers to the growth media during incubation, reduces substrate effects, allows more degrees of freedom for axonal growth, and more closely simulates the growth environment found in vivo. Using these 3D stages, we have electrospun free-standing, highly-aligned pure PLLA fiber scaffolds. We are exploring spinning coaxial fibers with a PLLA sheath and a second core polymer. These coaxial fiber scaffold structures offer additional opportunities for in situ delivery of growth agents and/or electrical stimulation for improved axonal growth results.

Electrospinning Preparation of Timosaponin B‐II‐Loaded PLLA Nanofibers and Their Antitumor Recurrence Activities In Vivo

Poly(L‐lactic)‐acid (PLLA) as a drug carrier and a water‐soluble drug timosaponin B‐II (TB‐II) as a model drug were selected to prepare drug‐loaded nanofibers by electrospinning. The average diameters of pure PLLA nanofibers and TB‐II‐loaded nanofibers were 212.5 ± 68.5, 219.7 ± 57.8, 232.8 ± 66.9, and 232.9 ± 97.7 nm, respectively. DSC and XRD results demonstrated that TB‐II was well incorporated into the nanofibers in an amorphous state. FI‐TR spectroscopy indicated that TB‐II had good compatibility with PLLA. In vitro release studies showed that TB‐II was rapidly released from the nanofibers within 6 h, followed by a gradual release for long time. In vivo biosafety test revealed no noticeable toxicity of these TB‐II nanofibers. The TB‐II released from the nanofibers had obvious inhibition effect against human hepatocellular carcinoma SMMC 7721 cells both in vivo and in vitro. It was confirmed that the TB‐II‐loaded nanofibers were a sustained delivery system which could effectively inhibit the tumor growth and recurrence after surgery.