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1.
Coraça DC Duek EA Padovani CA Camilli JA 《Journal of materials science. Materials in medicine》2008,19(7):2699-2704
Natural or synthetic materials may be used to aid tissue repair of fracture or pathologies where there has been a loss of bone mass. Polymeric materials have been widely studied, aiming at their use in orthopaedics and aesthetic plastic surgery. Polymeric biodegradable blends formed from two or more kinds of polymers could present faster degradation rate than homopolymers. The purpose of this work was to compare the biological response of two biomaterials: poly(L: -lactic acid)PLLA and poly(L: -lactic acid)PLLA/poly(ethylene oxide)PEO blend. Forty four-week-old rats were divided into two groups of 20 animals, of which one group received PLLA and the other PLLA/PEO implants. In each of the animals, one of the biomaterials was implanted in the proximal epiphysis of the right tibia. Each group was divided into subgroups of 5 animals, and sacrificed 2, 4, 8 and 16 weeks after surgery, respectively. Samples were then processed for analysis by light microscopy. Newly formed bone was found around both PLLA and PLLA/PEO implants. PLLA/PEO blends had a porous morphology after immersion in a buffer solution and in vivo implantation. The proportion 50/50 PLLA/PEO blend was adequate to promote this porous morphology, which resulted in gradual bone tissue growth into the implant. 相似文献
2.
Behzad Damadzadeh Hamideh Jabari Mikael Skrifvars Karri Airola Niko Moritz Pekka K. Vallittu 《Journal of materials science. Materials in medicine》2010,21(9):2523-2531
One main application of resorbable poly-l-lactic acid (PLLA) and poly-l-lactic-co-glycolic acid (PLGA) based materials is in medical implants. In this study composites were made from PLLA and PLGA
with hydroxyapatite (HAp) respective β-tricalcium phosphate (β-TCP) fillers. The filler content and particle size were varied,
and the thermal properties as well as the mechanical strength of the composites were investigated. The composites were made
by an extrusion compounding process giving 2–2.5 mm diameter sized profiles. The results verified that the thermal stability
of the composites was reasonable during the optimized compounding conditions. Scanning electron microscopy revealed that the
fillers were well dispersed in the polymer matrices. The mechanical properties were improved by the addition of the fillers.
The optimum mechanical properties for the extruded profiles were obtained with the HAp fillers. The E-modulus was increased
from 3.3 to 4.6 GPa by addition of filler particles (30 wt%) whereas the flexural strength was reduced from 133 to 106 MPa. 相似文献
3.
Cai K Yao K Yang Z Qu Y Li X 《Journal of materials science. Materials in medicine》2007,18(10):2017-2024
Biocompatibility and tissue regenerating capacity are essential for biomaterials that used in tissue engineering. The aim
of this study was to histologically assess the tissue reactions and bone conductivities of surface modified three dimensional
(3-D) poly (d, l-lactic acid) (PDLLA) scaffolds, which were coated with chitosan via a physical entrapment method. The native PDLLA scaffold
was prepared via thermally induced phrase separation technique and was characterized by scanning electron microscopy (SEM)
and differential scanning calorimetry (DSC). Osteocalcin assay, a method to evaluate the bone formation potential, has shown
that the osteocalcin production in chitosan-modified 3-D PDLLA scaffold group was significantly higher (p < 0.05) than that of in control. The tissue reactions and bone conductivities between surface modified PDLLA and native PDLLA
scaffolds were evaluated using a rabbit radialis defect model in vivo and compared at different implantation intervals (2,
4, 8 and 12 weeks). The histological results have shown a higher bone formation potential and better biocompatibility of chitosan-modified
3-D PDLLA scaffolds as compared with the control group scaffolds. 相似文献
4.
Aydin E Planell JA Hasirci V 《Journal of materials science. Materials in medicine》2011,22(11):2413-2427
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. 相似文献
5.
Thermally conductive carbon fiber/poly(l-lactic acid) (PLLA) composites were made by using fatty acid amides as binders to form a net-like structure of carbon fibers
in them, aiming at achieving high thermal diffusivity of the composites with a small amount of the fibers and facilitating
their processing without much cost. Infrared thermography analysis of composites with varying the size of carbon fibers and
controlling the solubility parameters of fatty acid amides in them revealed that the composite with 10 wt% of 6 mm-long carbon
fiber and 5 wt% of N,N′-ethylene bis-olearamide had a thermal diffusivity comparable to that of stainless steel (SUS304). This high thermal diffusivity
was due to percolation networks of long carbon fibers bound by the specific low-polarity amide in the composite. 相似文献
6.
Petra J. Kluger Ralf Wyrwa Jürgen Weisser Julia Maierle Miriam Votteler Claudia Rode Matthias Schnabelrauch Heike Walles Katja Schenke-Layland 《Journal of materials science. Materials in medicine》2010,21(9):2665-2671
Electrospinning is a long-known polymer processing technique that has received more interest and attention in recent years
due to its versatility and potential use in the field of biomedical research. The fabrication of three-dimensional (3D) electrospun
matrices for drug delivery and tissue engineering is of particular interest. In the present study, we identified optimal conditions
to generate novel electrospun polymeric scaffolds composed of poly-d/l-lactide and poly-l-lactide in the ratio 50:50. Scanning electron microscopic analyses revealed that the generated poly(d/l-lactide-co-l-lactide) electrospun hybrid microfibers possessed a unique porous high surface area mimicking native extracellular matrix
(ECM). To assess cytocompatibility, we isolated dermal fibroblasts from human skin biopsies. After 5 days of in vitro culture,
the fibroblasts adhered, migrated and proliferated on the newly created 3D scaffolds. Our data demonstrate the applicability
of electrospun poly(d/l-lactide-co-l-lactide) scaffolds to serve as substrates for regenerative medicine applications with special focus on skin tissue engineering. 相似文献
7.
Poly (d,l-lactide-co-glycolide) (PLGA) copolymers are among the few synthetic polymers approved for human use, but the biocompatibility of PLGA-derived
oligomers and particles remains questionable. Here, high molecular weight PLGA (Mw = 32,000) was radiolabeled with 125I in chloroform solution, and the body distribution of PLGA copolymer degradation products was examined following subcutaneous
implantation of round 125I-PLGA films on the back of Sprague Dawley rats. Autoradiographic images of the PLGA implant taken at 2, 4, 6, 8, 10, and
12 weeks revealed that the central portion of the film degraded much more rapidly than the marginal portions. Examination
of the body compartment distribution at these time points revealed that over one-half of the radioactivity was recovered from
skin. The remaining radioactivity was concentrated in the blood, liver, and kidneys. Radioactivity steadily appeared in the
blood and remained elevated up to 12 weeks after implantation, while the liver to kidney distribution began to decrease after
6 weeks. Cumulatively, these results indicate that the clearance of degraded particles and fragments from the implantation
site is extremely delayed. Moreover, the degraded particles and fragments were selectively concentrated in the liver and kidneys,
following release of degraded products into the bloodstream from the implantation site. 相似文献
8.
W. Yan C. Y. Zhang L. L. Xia T. Zhang Q. F. Fang 《Journal of materials science. Materials in medicine》2016,27(8):130
Calcium phosphate ceramics such as synthetic hydroxyapatite and tricalcium phosphate are widely used in the clinic, but they stimulate less bone regeneration. In this paper, nano-hydroxyapatite/poly(l-lactic acid) (nano-HA/PLLA) spindle composites with good mechanical performance were fabricated by a modified in situ precipitation method. The HA part of composite, distributing homogenously in PLLA matrix, is spindle shape with size of 10–30 nm in diameter and 60–100 nm in length. The molar ratio of Ca/P in the synthesized nano-HA spindles was deduced as 1.52 from the EDS spectra, which is close to the stoichiometric composition of HA (Ca/P & 1.67). The compress strength is up to 150 MPa when the HA content increase to 20 %. The in vitro tests indicate that HA/PLLA bio-composites have good biodegradability and bioactivity when immersed in simulated body fluid solutions. All the results suggested that HA/PLLA nano-biocomposites are appropriate to be applied as bone substitute in bone tissue engineering. 相似文献
9.
A biodegradable polymer coated with a bonelike apatite layer on its surface would be useful as a scaffold for bone tissue
regeneration. In this study, poly(l-lactic acid) (PLLA) was treated with oxygen plasma to produce oxygen-containing functional groups on its surface. The plasma-treated
specimen was then alternately dipped in aqueous CaCl2 and K2HPO4·3H2O solutions three times, to deposit apatite precursors onto the surface. The surface-modified specimen then successfully formed
a dense and uniform bonelike surface apatite layer after immersion for 24 h in a simulated body fluid with ion concentrations
approximately equal to those of human blood plasma. The adhesive strength between the apatite layer and the specimen surface
increased as the power density of the oxygen plasma used increased. The maximum adhesive strength of the apatite layer to
the specimen was significantly higher than that to the commercially available artificial bone, HAPEXTM. The resultant bonelike apatite–PLLA composite would be useful as a scaffold for bone tissue regeneration. 相似文献
10.
Paakinaho K Heino H Pelto M Hannula M Törmälä P Kellomäki M 《Journal of materials science. Materials in medicine》2012,23(3):613-621
This study reports of the novel water-induced shape-memory of bioabsorbable poly(d,l-lactide). We have developed an orientation-based programming process that generates an ability for poly(d,l-lactide) to transform its shape at 37°C in an aqueous environment without external energy and to adapt to a predefined stress
level by stress generation or relaxation. In this orientation-programming process, polymer material is deformed and oriented
at an elevated temperature and subsequently cooled down while retaining its deformed shape, tension, and polymer chain entanglements.
At body temperature and in an aqueous environment, the shape-memory is activated by the plasticizing effect of water molecules
diffused into the polymer matrix causing an entropy-driven directed relaxation of oriented and preloaded polymer chains. This
plasticizing effect is clearly seen as a decrease of the onset glass transition temperature by 10–13°C. We found that γ-irradiation
used for sterilizing the orientation-programmed materials strongly affected the shape-recovery rate, but not the recovery
ratio. Both non-γ-irradiated and γ-irradiated sample materials showed excellent shape-recovery ratios during a ten-week test
period: 94 and 97%, respectively. The orientation-programmed materials generated a predefined load in a 37°C aqueous environment
when their shape-recovery was restricted, but when external tension was applied to them, they adapted to the predefined level
by stress relaxation. Our results show that functionality in terms of shape-memory can be generated in bioabsorbable polymers
without tailoring the polymer chain structure thus shortening the time from development of technology to its utilization in
medical devices. 相似文献
11.
Ren J Zhao P Ren T Gu S Pan K 《Journal of materials science. Materials in medicine》2008,19(3):1075-1082
Biodegradable polymer/bioceramic composite scaffolds can overcome the limitations of conventional ceramic bone substitutes
such as brittleness and difficulty in shaping. However, conventional methods for fabricating polymer/bioceramic composite
scaffolds often use organic solvents (e.g., the solvent casting and particulate leaching (SC/PL) method), which might be harmful
to cells or tissues. In this study, Poly (d,l-lactide)/nano-hydroxyapatite (PDLLA/NHA) composites were prepared by in-situ polymerization, and highly porous scaffolds
were fabricated using a novel method, supercritical CO2/salt-leaching method (SC CO2/SL). The materials and scaffolds were investigated by scanning electronic microscopy (SEM), transmission electronic microscopy
(TEM) and gel permeation chromatography (GPC). GPC showed that the molecular weight of composites decreased with increase
of NHA content. However, the water absorption and compressive strength increased dramatically. The SEM micrographs showed
that the scaffolds with pore size about 250 μm were obtained by controlling parameters of SC CO2/SL. The biocompatibility of PDLLA/NHA porous scaffolds were evaluated in vitro and in vivo. The evaluation on the cytotoxicity
were carried out by cell relative growth rate (RGR) method and cell direct contact method. The cytotoxicity of these scaffolds
was in grade I according to ISO 10993-1. There was no toxicosis and death cases observed in acute systemic toxicity test.
And histological observation of the tissue response (1 and 9 weeks after the implantation) showed that there are still some
slight inflammation responses. 相似文献
12.
Chain conformation order of poly (l-lactic acid) (PLLA) was investigated by time-lapsed Fourier transform infrared (FTIR) spectroscopy and two-dimensional infrared correlation spectroscopy during the isothermal crystallization at 140 °C. The result showed that the PLLA formed α-crystal during the isothermal crystallization at 140 °C. According to the detailed information in the region of 1000–1500 cm?1 investigated by infrared and 2D correlation spectroscopy, it was found that the conformation of C–O–C groups changed prior to that of CH3 groups. Moreover, the formation of the initial helix chain conformation was interfered by the interchain interactions between the CH3 groups, which consequently resulted in the formation of α-crystal with the distorted 103 helix conformation. 相似文献
13.
Mukherjee S Gualandi C Focarete ML Ravichandran R Venugopal JR Raghunath M Ramakrishna S 《Journal of materials science. Materials in medicine》2011,22(7):1689-1699
In myocardial tissue engineering the use of synthetically bioengineered flexible patches implanted in the infarcted area is
considered one of the promising strategy for cardiac repair. In this work the potentialities of a biomimetic electrospun scaffold
made of a commercial copolymer of (l)-lactic acid with trimethylene carbonate (P(l)LA-co-TMC) are investigated in comparison to electrospun poly(l)lactic acid. The P(l)LA-co-TMC scaffold used in this work is a glassy rigid material at room temperature while it is a rubbery soft material at 37°C.
Mechanical characterization results (tensile stress–strain and creep-recovery measurements) show that at 37°C electrospun
P(l)LA-co-TMC displays an elastic modulus of around 20 MPa and the ability to completely recover up to 10% of deformation. Cell culture
experiments show that P(l)LA-co-TMC scaffold promotes cardiomyocyte proliferation and efficiently preserve cell morphology, without hampering expression
of sarcomeric alpha actinin marker, thus demonstrating its potentialities as synthetic biomaterial for myocardial tissue engineering. 相似文献
14.
Gerhardt LC Jell GM Boccaccini AR 《Journal of materials science. Materials in medicine》2007,18(7):1287-1298
Titanium dioxide (TiO2) nanoparticles were investigated for bone tissue engineering applications with regard to bioactivity and particle cytotoxicity.
Composite films on the basis of poly(d,l lactid acid) (PDLLA) filled with 0, 5 and 30 wt% TiO2 nanoparticles were processed by solvent casting. Bioactivity, characterised by formation of hydroxyapatite (HA) on the materials
surface, was investigated for both the free TiO2 nanoparticles and PDLLA/TiO2 composite films upon immersion in supersaturated simulated body fluid (1.5 SBF) for up to 3 weeks. Non-stoichiometric HA
nanocrystals (ns-HA) with an average diameter of 40 nm were formed on the high content (30 wt% TiO2) composite films after 2 weeks of immersion in 1.5 SBF. For the pure PDLLA film and the low content composite films (5 wt%
TiO2) trace amounts of ns-HA nanocrystals were apparent after 3 weeks. The TiO2 nanopowder alone showed no bioactivity. The effect of TiO2 nanoparticles (0.5–10,000 μg/mL) on MG-63 osteoblast-like cell metabolic activity was assessed by the MTT assay. TiO2 particle concentrations of up to 100 μg/mL had no significant effect on MG-63 cell viability. 相似文献
15.
Chen AZ Pu XM Kang YQ Liao L Yao YD Yin GF 《Journal of materials science. Materials in medicine》2007,18(12):2339-2345
Poly(l-lactide) (PLLA) microparticles were prepared in supercritical anti-solvent process. The effects of several key factors on
surface morphology, and particle size and particle size distribution were investigated. These factors included initial drops
size, saturation ratio of PLLA solution, pressure, temperature, concentration of the organic solution, the flow rate of the
solution and molecular weight of PLLA. The results indicated that the saturation ratio of PLLA solution, concentration of
the organic solution and flow rate of the solution played important roles on the properties of products. Various microparticles
with the mean particle size ranging from 0.64 to 6.64 μm, could be prepared by adjusting the operational parameters. Fine
microparticles were obtained in a process namely solution-enhanced dispersion by supercritical fluids (SEDS) process with
dichloromethane/acetone mixture as solution. 相似文献
16.
Novel reinforced poly(l-lactic acid) (PLLA) scaffolds such as solid shell, porous shell, one beam and two beam reinforced scaffolds were developed
to improve the mechanical properties of a standard PLLA scaffold. Experimental results clearly indicated that the compressive
mechanical properties such as the strength and the modulus are effectively improved by introducing the reinforcement structures.
A linear elastic model consisting of three phases, that is, the reinforcement, the porous matrix and the boundary layer was
also introduced in order to predict the compressive moduli of the reinforced scaffolds. The comparative study clearly showed
that the simple theoretical model can reasonably predict the moduli of the scaffolds with three phase structures. The failure
mechanism of the solid shell and the porous shell reinforced scaffolds under compression were found to be buckling of the
solid shell and localized buckling of the struts constructing the pores in the porous shell, respectively. For the beam reinforced
scaffolds, on the contrary, the primary failure mechanism was understood to be micro-cracking within the beams and the subsequent
formation of the main-crack due to the coalescence of the micro-racks. The biological study was exhibited that osteoblast-like
cells, MC3T3-E1, were well adhered and proliferated on the surfaces of the scaffolds after 12 days culturing. 相似文献
17.
Meng Zhang Yajiang Huang Miqiu Kong Hong Zhu Guangling Chen Qi Yang 《Journal of Materials Science》2012,47(3):1339-1347
The successful development of co-continuous structure from poly(l-lactide) (PLLA) blends by melt mixing with lower PLLA content is highly desired in preparing macroporous biomaterials. However,
the low viscosity of PLLA makes it difficult to prepare co-continuous PLLA blends at low PLLA concentration. In this study,
hydrophilic silica nanoparticle is adopted to control the morphology of co-continuous polystyrene (PS)/PLLA blends. The influence
of nanoparticle concentration on the co-continuity intervals and rheological properties of PS/PLLA blends are examined. The
morphological stability of blends against melt annealing is also determined and discussed with a conceptual coarsening model
for co-continuous structure. The results demonstrate that the incorporation of silica nanoparticles into PS/PLLA blends can
be used to prepare macroporous PLLA structure with controllable pore size at lower PLLA content. 相似文献
18.
Poly(l-lactic acid)/hydroxyapatite (PLLA/HA) nanocomposite, which combines the properties of PLLA and HA, is suitable to construct scaffold for bone tissue engineering. Its mineralization behavior plays a key role in composite’s property. In this present work, two PLLA/HA composites with porous and compact architecture were fabricated and soaked into simulated body fluid (SBF) at 37 °C for in vitro mineralization, respectively. An attenuated total reflection Fourier transform infrared (ATR FTIR) mapping coupled with principal component analysis was developed to investigate the mineralization kinetics. The FTIR images with an area of 300 × 300 μm2 were collected every 7 days. The results suggest that the mineralization of PLLA/HA composites in SBF follows a zero-order kinetic model, no matter what the architecture is. However, it follows a second-order model when the composite is degraded in phosphate-buffered saline solution based on our previous work. The mechanisms of the in vitro mineralization kinetics in different submersion solutions are discussed. Our results alert researchers that they should choose the mineralization medium cautiously. 相似文献
19.
Aleksandra Buzarovska Sorina Dinescu Leona Chitoiu Marieta Costache 《Journal of Materials Science》2018,53(16):11151-11166
Cytocompatibility is one of the most important aspects in evaluating biomaterials for tissue engineering applications. In this study, biodegradable polymer scaffolds based on nanocomposites of poly(l-lactic acid) and TiO2 nanoparticles functionalized with oleic acid (5 and 10 wt%) were prepared by thermally induced phase separation method. The aim of this research was to evaluate the properties of nanocomposite scaffolds and to investigate the influence of functionalized nanofiller on their bioactivity, biodegradability and cytocompatibility. The nanocomposite scaffolds showed bioactivity in supersaturated fluids and reduced biodegradation in simulated body fluid when compared to pure PLA scaffold. Cell viability and proliferation potential in contact with nanocomposite scaffolds were tested via MTT assay, while the scaffolds cytotoxic potential was evaluated using lactate dehydrogenase method. It was found that incorporation of functionalized TiO2 nanofiller with content of 5 wt% in the corresponding PLA matrix has a significant positive effect on the cell viability and proliferation, while at higher nanofiller content (10 wt%), insignificant cell proliferation and increased cytotoxicity were confirmed. Furthermore, PLA/TiO2–OA nanocomposite scaffolds were proved as promising materials for drug delivery. 相似文献
20.
LTI was attempted to modify the microstructure of poly (l-lactic acid) (PLLA) and to improve its mechanical properties in this study. Bending modulus, strength and fracture toughness
of PLLA/LTI were evaluated, and compared to those of the base PLLA to assess the effectiveness of LTI blending. Effect of
LTI addition on fracture micromechanism was also investigated by observing and comparing the fracture surfaces of PLLA/LTI
and PLLA using a field emission scanning electron microscope (FE-SEM). Experimental results showed that the bending properties
such as the bending modulus and the strength are effectively improved due to polymerization of PLLA molecules by LTI blending.
The fracture toughness value was also improved due to increase of ductile deformation, i.e., energy dissipation in the crack-tip
region. 相似文献