Article

Surface-modified hydroxyapatite linked byL-lactic acid oligomer in the absence of catalyst

Journal of Polymer Science Part A Polymer Chemistry (Impact Factor: 3.54). 01/2005; 43(21):5177-5185. DOI: 10.1002/pola.21006

ABSTRACT A new surface modification method of hydroxyapatite nanoparticles (n-HA) by surface grafting reaction of L-lactic acid oligomer with carboxyl terminal (LAc oligomer) in the absence of any catalyst was developed. The LAc oligomer with a certain molecular weight was directly synthesized by condensation of L-lactic acid. Surface-modified HA nanoparticles (p-HA) were attested by Fourier transformation infrared spectroscopy, 31P MAS-NMR, and thermal gravimetric analysis (TGA). The results showed that LAc oligomer could be grafted onto the n-HA surface by forming a Ca carboxylate bond. The grafting amount of LAc oligomer was about 13.3 wt %. The p-HA/PLLA composites showed good mechanical properties and uniform microstructure. The tensile strength and modulus of the p-HA/PLLA composite containing 15 wt % of p-HA were 68.7 MPa and 2.1 GPa, respectively, while those of the n-HA/PLLA composites were 43 MPa and 1.6 GPa, respectively. The p-HA/PLLA composites had better thermal stability than n-HA/PLLA composites and neat PLLA had, as determined by isothermal TGA. The hydrolytic degradation behavior of the composites in phosphate buffered saline (PBS, pH 7.4) was investigated. The p-HA/PLLA composites lost their mechanical properties more slowly than did n-HA/PLLA composites in PBS because of their reinforced adhesion between the HA filler and PLLA matrix. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5177–5185, 2005

0 Bookmarks
 · 
48 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: 3-aminopropyltrimethoxysilane (APS) surface modification of sol-gel bioactive glass (BG) was performed to improve the phase compatibility between poly-L-lactide (PLLA) and BG. The composite based on PLLA and modified BG was fabricated by using hot pressing methods. The effects of APS modification on the morphology of BG and mechanical properties of the PLLA/BG composite were investigated. The results indicated that uniformly dispersed BG particles, without agglomeration, were obtained after surface modification. Furthermore, the bending strength, bending modulus and shearing strength of PLLA/BG-APS composites were all higher than those of unmodified composites. However, the bending strength and shearing strength of PLLA/BG-APS composites significantly decreased with increasing BG content for all, whereas the bending modulus increased.
    Journal of Macromolecular Science Part B 08/2012; · 0.63 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Although microRNAs are expressed extensively in the central nervous system in physiological and pathological conditions, their expression in neurological disorder of epilepsy has not been well characterized. Here we investigated microRNA expression pattern in post status epilepticus rats (24h after status). Rat MicroRNA array and differential analysis had detected 19 up-regulated microRNAs and 7 down-regulated microRNAs in rat hippocampus, and four randomly selected deregulated microRNAs (microRNA-34a, microRNA-22, microRNA-125a, microRNA-21) were confirmed by qRT-PCR, then their expression alterations in rat peripheral blood were analyzed. We found that these four deregulated microRNAs were also differentially expressed in rat peripheral blood, and trends for their blood expression alterations were just the same as their counterparts in rat hippocampus. Thus, our results have not only characterized the microRNA expression profile in post status epilepticus rat hippocampus but also demonstrated that some rat hippocampal microRNAs were probably associated with rat peripheral blood microRNAs. Moreover, targets of these deregulated microRNAs were analyzed using bioinformatics and the identified enriched MAPK pathway and long-term potentiation pathway might have been involved in molecular mechanisms concerning neuronal death, inflammation and epileptogenesis.
    Neuroscience Letters 01/2011; 488(3):252-7. · 2.03 Impact Factor
  • Journal of Materials Chemistry 12/2009; · 5.97 Impact Factor