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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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The mold-cast tensile specimens of PLGA, agglomerated nano-titania in PLGA composites (PTCa), well-dispersed nano-titania in PLGA composites (PTCd), agglomerated nano-HA in PLGA composites (PHAa), well-dispersed nano-HA in PLGA composites (PHAd) and the casting mold for tensile specimens. The tensile specimen gage length × width × thickness = 25 × 10 × 0.5 mm. The depth of the casting mold was designed as 10 mm.
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f1-ijn-5-299: The mold-cast tensile specimens of PLGA, agglomerated nano-titania in PLGA composites (PTCa), well-dispersed nano-titania in PLGA composites (PTCd), agglomerated nano-HA in PLGA composites (PHAa), well-dispersed nano-HA in PLGA composites (PHAd) and the casting mold for tensile specimens. The tensile specimen gage length × width × thickness = 25 × 10 × 0.5 mm. The depth of the casting mold was designed as 10 mm.

Mentions: PLGA was first dissolved in chloroform (Sigma-Aldrich) at 50°C and titania nanoparticles were added into the PLGA solution to produce a 30/70 ceramic/polymer weight ratio in the nanocomposites. The nanocomposite mixture was then processed using a Misonix 3000 sonicator (Misonix Inc, Farmingdale, NY, USA) with its microtip immersed in the mixture. The dispersion status of the final composites was controlled by sonication power. The output power of 3 W and 9 W were used to obtain agglomerated and dispersed specimens, respectively. The Misonix 3000 sonicator permits the application of ultrasonic energy to suspensions on a pulsed basis. In this study, the pulse width was set at 50% of the duty cycle out of a 1 second cycle time. This intermittent operation permitted high intensity sonication while avoiding heat buildup in the processed suspensions. After sonication for 10 min, the composite suspension was immediately cast into a mold that was designed for dog-bone shaped tensile specimens or a mold for compressive specimens, evaporated in air at room temperature for 24 hours and dried in an air vacuum chamber at room temperature for 48 hours. According to the titania dispersion states in the polymer, these nano-titania/PLGA composites (PTC) were termed as PTCa (a = agglomerated) and PTCd (d = dispersed). PLGA was used as a control and was prepared by the solvent-casting technique described above except that no ceramics were added. These mold-cast tensile specimens had the same dimensions (Figure 1). The gage length was 25 mm, the gage width was 10 mm, and the thickness was 0.5 mm. The compressive specimens had a circular shape. The gage diameter of the compressive specimens was 10 mm and the thickness was 0.5 mm.


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

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

The mold-cast tensile specimens of PLGA, agglomerated nano-titania in PLGA composites (PTCa), well-dispersed nano-titania in PLGA composites (PTCd), agglomerated nano-HA in PLGA composites (PHAa), well-dispersed nano-HA in PLGA composites (PHAd) and the casting mold for tensile specimens. The tensile specimen gage length × width × thickness = 25 × 10 × 0.5 mm. The depth of the casting mold was designed as 10 mm.
© Copyright Policy
Related In: Results  -  Collection

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

f1-ijn-5-299: The mold-cast tensile specimens of PLGA, agglomerated nano-titania in PLGA composites (PTCa), well-dispersed nano-titania in PLGA composites (PTCd), agglomerated nano-HA in PLGA composites (PHAa), well-dispersed nano-HA in PLGA composites (PHAd) and the casting mold for tensile specimens. The tensile specimen gage length × width × thickness = 25 × 10 × 0.5 mm. The depth of the casting mold was designed as 10 mm.
Mentions: PLGA was first dissolved in chloroform (Sigma-Aldrich) at 50°C and titania nanoparticles were added into the PLGA solution to produce a 30/70 ceramic/polymer weight ratio in the nanocomposites. The nanocomposite mixture was then processed using a Misonix 3000 sonicator (Misonix Inc, Farmingdale, NY, USA) with its microtip immersed in the mixture. The dispersion status of the final composites was controlled by sonication power. The output power of 3 W and 9 W were used to obtain agglomerated and dispersed specimens, respectively. The Misonix 3000 sonicator permits the application of ultrasonic energy to suspensions on a pulsed basis. In this study, the pulse width was set at 50% of the duty cycle out of a 1 second cycle time. This intermittent operation permitted high intensity sonication while avoiding heat buildup in the processed suspensions. After sonication for 10 min, the composite suspension was immediately cast into a mold that was designed for dog-bone shaped tensile specimens or a mold for compressive specimens, evaporated in air at room temperature for 24 hours and dried in an air vacuum chamber at room temperature for 48 hours. According to the titania dispersion states in the polymer, these nano-titania/PLGA composites (PTC) were termed as PTCa (a = agglomerated) and PTCd (d = dispersed). PLGA was used as a control and was prepared by the solvent-casting technique described above except that no ceramics were added. These mold-cast tensile specimens had the same dimensions (Figure 1). The gage length was 25 mm, the gage width was 10 mm, and the thickness was 0.5 mm. The compressive specimens had a circular shape. The gage diameter of the compressive specimens was 10 mm and the thickness was 0.5 mm.

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