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Mechanical properties of dispersed ceramic nanoparticles in polymer composites for orthopedic applications.

Liu H, Webster TJ - Int J Nanomedicine (2010)

Bottom Line: The mechanical properties of the resulting PLGA composites with well-dispersed ceramic (either titania or HA) nanoparticles were investigated and compared with composites with agglomerated ceramic nanoparticles.Results demonstrated that well-dispersed ceramic nanoparticles (titania or HA) in PLGA improved mechanical properties compared with agglomerated ceramic nanoparticles even though the weight percentage of the ceramics was the same.Specifically, well-dispersed nanoceramics in PLGA enhanced the tensile modulus, tensile strength at yield, ultimate tensile strength, and compressive modulus compared with the more agglomerated nanoceramics in PLGA.

View Article: PubMed Central - PubMed

Affiliation: Division of Engineering, Brown University, Providence, RI, USA.

ABSTRACT
Ceramic/polymer composites have been considered as third-generation orthopedic biomaterials due to their ability to closely match properties (such as surface, chemistry, biological, and mechanical) of natural bone. It has already been shown that the addition of nanophase compared with conventional (or micron-scale) ceramics to polymers enhances bone cell functions. However, in order to fully take advantage of the promising nanometer size effects that nanoceramics can provide when added to polymers, it is critical to uniformly disperse them in a polymer matrix. This is critical since ceramic nanoparticles inherently have a strong tendency to form larger agglomerates in a polymer matrix which may compromise their properties. Therefore, in this study, model ceramic nanoparticles, specifically titania and hydroxyapatite (HA), were dispersed in a model polymer (PLGA, poly-lactic-co-glycolic acid) using high-power ultrasonic energy. The mechanical properties of the resulting PLGA composites with well-dispersed ceramic (either titania or HA) nanoparticles were investigated and compared with composites with agglomerated ceramic nanoparticles. Results demonstrated that well-dispersed ceramic nanoparticles (titania or HA) in PLGA improved mechanical properties compared with agglomerated ceramic nanoparticles even though the weight percentage of the ceramics was the same. Specifically, well-dispersed nanoceramics in PLGA enhanced the tensile modulus, tensile strength at yield, ultimate tensile strength, and compressive modulus compared with the more agglomerated nanoceramics in PLGA. In summary, supplemented by previous studies that demonstrated greater osteoblast (bone-forming cell) functions on well-dispersed nanophase ceramics in polymers, the present study demonstrated that the combination of PLGA with well-dispersed nanoceramics enhanced mechanical properties necessary for load-bearing orthopedic/dental applications.

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SEM micrographs of nano-titania and nano-titania/PLGA composites: (a) nano-titania, (b,c) PTCa (the agglomerated nano-titania in PLGA composites), (d,e) PTCd (the well-dispersed nano-titania in PLGA composites). (b,d) the top surface, (c,e) the bottom surface. Magnification bars: 1 μm.
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f2-ijn-5-299: SEM micrographs of nano-titania and nano-titania/PLGA composites: (a) nano-titania, (b,c) PTCa (the agglomerated nano-titania in PLGA composites), (d,e) PTCd (the well-dispersed nano-titania in PLGA composites). (b,d) the top surface, (c,e) the bottom surface. Magnification bars: 1 μm.

Mentions: Scanning electron micrographs suggested that the distribution of nano-titania particles was much different in the PTCa and PTCd samples although both of them had the same weight percentage of titania (that is, 30 wt%) in PLGA, as shown in Figure 2. Specifically, there were less titania particles on the top surface of PTCa than PTCd because the ceramic agglomerates larger than 100 nm descended faster than the solvent evaporation rate according to the established Stoke’s Equation. The amount of surface area occupied by titania increased on the top surface of PTCd (10.1%, Figure 2d) compared with PTCa (5.7%, Figure 2b) because the solvent evaporation was much faster than the sedimentation of the well-dispersed titania particles less than 100 nm. Moreover, for the PTCa, the top surface was much different from the bottom surface, which indicated differences in the distribution of the nano-titania agglomerates. More agglomerates were concentrated on the bottom side of the PTCa non-uniformly. For the PTCd, however, there was no significant difference between the top and bottom surfaces and, thus, the distribution of nano-titania in PLGA was more uniform.


Mechanical properties of dispersed ceramic nanoparticles in polymer composites for orthopedic applications.

Liu H, Webster TJ - Int J Nanomedicine (2010)

SEM micrographs of nano-titania and nano-titania/PLGA composites: (a) nano-titania, (b,c) PTCa (the agglomerated nano-titania in PLGA composites), (d,e) PTCd (the well-dispersed nano-titania in PLGA composites). (b,d) the top surface, (c,e) the bottom surface. Magnification bars: 1 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2865024&req=5

f2-ijn-5-299: SEM micrographs of nano-titania and nano-titania/PLGA composites: (a) nano-titania, (b,c) PTCa (the agglomerated nano-titania in PLGA composites), (d,e) PTCd (the well-dispersed nano-titania in PLGA composites). (b,d) the top surface, (c,e) the bottom surface. Magnification bars: 1 μm.
Mentions: Scanning electron micrographs suggested that the distribution of nano-titania particles was much different in the PTCa and PTCd samples although both of them had the same weight percentage of titania (that is, 30 wt%) in PLGA, as shown in Figure 2. Specifically, there were less titania particles on the top surface of PTCa than PTCd because the ceramic agglomerates larger than 100 nm descended faster than the solvent evaporation rate according to the established Stoke’s Equation. The amount of surface area occupied by titania increased on the top surface of PTCd (10.1%, Figure 2d) compared with PTCa (5.7%, Figure 2b) because the solvent evaporation was much faster than the sedimentation of the well-dispersed titania particles less than 100 nm. Moreover, for the PTCa, the top surface was much different from the bottom surface, which indicated differences in the distribution of the nano-titania agglomerates. More agglomerates were concentrated on the bottom side of the PTCa non-uniformly. For the PTCd, however, there was no significant difference between the top and bottom surfaces and, thus, the distribution of nano-titania in PLGA was more uniform.

Bottom Line: The mechanical properties of the resulting PLGA composites with well-dispersed ceramic (either titania or HA) nanoparticles were investigated and compared with composites with agglomerated ceramic nanoparticles.Results demonstrated that well-dispersed ceramic nanoparticles (titania or HA) in PLGA improved mechanical properties compared with agglomerated ceramic nanoparticles even though the weight percentage of the ceramics was the same.Specifically, well-dispersed nanoceramics in PLGA enhanced the tensile modulus, tensile strength at yield, ultimate tensile strength, and compressive modulus compared with the more agglomerated nanoceramics in PLGA.

View Article: PubMed Central - PubMed

Affiliation: Division of Engineering, Brown University, Providence, RI, USA.

ABSTRACT
Ceramic/polymer composites have been considered as third-generation orthopedic biomaterials due to their ability to closely match properties (such as surface, chemistry, biological, and mechanical) of natural bone. It has already been shown that the addition of nanophase compared with conventional (or micron-scale) ceramics to polymers enhances bone cell functions. However, in order to fully take advantage of the promising nanometer size effects that nanoceramics can provide when added to polymers, it is critical to uniformly disperse them in a polymer matrix. This is critical since ceramic nanoparticles inherently have a strong tendency to form larger agglomerates in a polymer matrix which may compromise their properties. Therefore, in this study, model ceramic nanoparticles, specifically titania and hydroxyapatite (HA), were dispersed in a model polymer (PLGA, poly-lactic-co-glycolic acid) using high-power ultrasonic energy. The mechanical properties of the resulting PLGA composites with well-dispersed ceramic (either titania or HA) nanoparticles were investigated and compared with composites with agglomerated ceramic nanoparticles. Results demonstrated that well-dispersed ceramic nanoparticles (titania or HA) in PLGA improved mechanical properties compared with agglomerated ceramic nanoparticles even though the weight percentage of the ceramics was the same. Specifically, well-dispersed nanoceramics in PLGA enhanced the tensile modulus, tensile strength at yield, ultimate tensile strength, and compressive modulus compared with the more agglomerated nanoceramics in PLGA. In summary, supplemented by previous studies that demonstrated greater osteoblast (bone-forming cell) functions on well-dispersed nanophase ceramics in polymers, the present study demonstrated that the combination of PLGA with well-dispersed nanoceramics enhanced mechanical properties necessary for load-bearing orthopedic/dental applications.

Show MeSH
Related in: MedlinePlus