Synergistic effect of sulfonation followed by precipitation of amorphous calcium phosphate on the bone-bonding strength of carbon fiber reinforced polyetheretherketone

Sulfonation and applications of amorphous calcium phosphate are known to make polyetheretherketone (PEEK) bioactive. Sulfonation followed by precipitation of amorphous calcium phosphate (AN-treatment) may provide PEEK with further bone-bonding strength. Herein, we prepared a carbon-fiber-reinforced PEEK (CPEEK) with similar tensile strength to cortical bone and a CPEEK subjected to AN-treatment (CPEEK-AN). The effect of AN-treatment on the bone-bonding strength generated at the interface between the rabbit’s tibia and a base material was investigated using a detaching test at two time-points (4 and 8 weeks). At 4 weeks, the strength of CPEEK-AN was significantly higher than that of CPEEK due to the direct bonding between the interfaces. Between 4 and 8 weeks, the different bone forming processes showed that, with CPEEK-AN, bone consolidation was achieved, thus improving bone-bonding strength. In contrast, with CPEEK, a new bone was absorbed mainly on the interface, leading to poor strength. These observations were supported by an in vitro study, which showed that pre-osteoblast on CPEEK-AN caused earlier maturation and mineralization of the extracellular matrix than on CPEEK. Consequently, AN-treatment, comprising a combination of two efficient treatments, generated a synergetic effect on the bonding strength of CPEEK

Development of Apatite Nuclei Precipitated Carbon Nanotube-Polyether Ether Ketone Composite with Biological and Electrical Properties

We aimed to impart apatite-forming ability to carbon nanotube (CNT)-polyether ether ketone (PEEK) composite (CNT-PEEK). Since CNT possesses electrical conductivity, CNT-PEEK can be expected to useful not only for implant materials but also biosensing devices. First of all, in this study, CNT-PEEK was treated with sulfuric acid to form fine pores on its surface. Then, the hydrophilicity of the substrate was improved by oxygen plasma treatment. After that, the substrate was promptly immersed in simulated body fluid (SBF) which was adjusted at pH 8.40, 25.0 °C (alkaline SBF) and held in an incubator set at 70.0 °C for 1 day to deposit fine particles of amorphous calcium phosphate, which we refer to as ‘apatite nuclei’. When thus-treated CNT-PEEK was immersed in SBF, its surface was spontaneously covered with hydroxyapatite within 1 day by apatite nuclei deposited in the fine pores and high apatite-forming ability was successfully demonstrated. The CNT-PEEK also showed conductivity even after the above treatment and showed smaller impedance than that of the untreated CNT-PEEK substrate

Surface Modification of Carbon Fiber-Polyetheretherketone Composite to Impart Bioactivity by Using Apatite Nuclei

The authors aimed to impart the apatite-forming ability to 50 wt% carbon fiber-polyetheretherketone composite (50C-PEEK), which has more suitable mechanical properties as artificial bone materials than pure PEEK. First, the 50C-PEEK was treated with sulfuric acid in a short time to form pores on the surface. Second, the surface of the 50C-PEEK was treated with oxygen plasma to improve the hydrophilicity. Finally, fine particles of calcium phosphate, which the authors refer to as “apatite nuclei”, were precipitated on the surface of the 50C-PEEK by soaking in an aqueous solution containing multiple inorganic ions such as phosphate and calcium (modified-SBF) at pH 8.20, 25 °C. The 50C-PEEK without the modified-SBF treatment did not show the formation of apatitic phase even after immersion in simulated body fluid (SBF) for 7 days. The 50C-PEEK treated with the modified-SBF showed the formation of apatitic phase on the entire surface within 1 day in the SBF. The apatite nuclei-precipitated 50C-PEEK will be expected as a new artificial bone material with high bioactivity that is obtained without complicated fabrication processes

Axonal localization of Ca2+-dependent activator protein for secretion 2 is critical for subcellular locality of brain-derived neurotrophic factor and neurotrophin-3 release affecting proper development of postnatal mouse cerebellum.

Ca2+-dependent activator protein for secretion 2 (CAPS2) is a protein that is essential for enhanced release of brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) from cerebellar granule cells. We previously identified dex3, a rare alternative splice variant of CAPS2, which is overrepresented in patients with autism and is missing an exon 3 critical for axonal localization. We recently reported that a mouse model CAPS2Δex3/Δex3 expressing dex3 showed autistic-like behavioral phenotypes including impaired social interaction and cognition and increased anxiety in an unfamiliar environment. Here, we verified impairment in axonal, but not somato-dendritic, localization of dex3 protein in cerebellar granule cells and demonstrated cellular and physiological phenotypes in postnatal cerebellum of CAPS2Δex3/Δex3 mice. Interestingly, both BDNF and NT-3 were markedly reduced in axons of cerebellar granule cells, resulting in a significant decrease in their release. As a result, dex3 mice showed developmental deficits in dendritic arborization of Purkinje cells, vermian lobulation and fissurization, and granule cell precursor proliferation. Paired-pulse facilitation at parallel fiber-Purkinje cell synapses was also impaired. Together, our results indicate that CAPS2 plays an important role in subcellular locality (axonal vs. somato-dendritic) of enhanced BDNF and NT-3 release, which is indispensable for proper development of postnatal cerebellum

Levels of Tetrodotoxins in Spawning Pufferfish, <i>Takifugu alboplumbeus</i>

Tetrodotoxin (TTX), also known as pufferfish toxin, is an extremely potent neurotoxin thought to be used as a biological defense compound in organisms bearing it. Although TTX was thought to function as a chemical agent for defense and anti-predation and an attractant for TTX-bearing animals including pufferfish, it has recently been demonstrated that pufferfish were also attracted to 5,6,11-trideoxyTTX, a related compound, rather than TTX alone. In this study, we attempted to estimate the roles of TTXs (TTX and 5,6,11-trideoxyTTX) in the pufferfish, Takifugu alboplumbeus, through examining the location of TTXs in various tissues of spawning pufferfish from Enoshima and Kamogawa, Japan. TTXs levels in the Kamogawa population were higher than those in the Enoshima population, and there was no significant difference in the amount of TTXs between the sexes in either population. Individual differences were greater in females than in males. However, the location of both substances in tissues differed significantly between sexes: male pufferfish accumulated most of their TTX in the skin and liver and most of their 5,6,11-trideoxyTTX in the skin, whereas females accumulated most of their TTX and 5,6,11-trideoxyTTX in the ovaries and skin

Decreased trafficking and release of NT-3 in the CAPS2^Δex3/Δex3 primary cerebellar culture.

<p>(A–F) Subcellular localization of CAPS2 (A, D) and NT-3 (B, E) in wild-type (A–C) and CAPS2^Δex3/Δex3 (D–F) cerebellar primary cultures at 7 DIV. A merged image of CAPS2 (<i>green</i>) and NT-3 (<i>red</i>) is shown in (C, F). Scale bars, 10 µm. (G) Immunolabeling intensities of NT-3 along the axons of wild-type (white bar, <i>n</i> = 27), CAPS2^+/Δex3 (gray bar, <i>n</i> = 23) and CAPS2^Δex3/Δex3 (black bar, <i>n</i> = 21) cells are shown. Axons were identified by tau immunostaining and by their characteristic thin and long processes. Signal intensities were quantified with NIH ImageJ per unit length (arbitrary unit). (H) Immunolabeling intensities of NT-3 on the somata of wild-type (white bar, <i>n</i> = 23), CAPS2^+/Δex3 (gray bar, <i>n</i> = 23) and CAPS2^Δex3/Δex3 (black bar, <i>n</i> = 22) cells are shown. Signal intensities were quantified per unit area (arbitrary unit). *<i>P</i><0.05; **<i>P</i><0.01, by Student's <i>t</i>-test. (I) NT-3 release activity in the wild-type (white bar, <i>n</i> = 16), CAPS2^+/Δex3 (gray bar, <i>n</i> = 21) and CAPS2^Δex3/Δex3 (black bar, <i>n</i> = 27) cerebellar cultures was evaluated by measuring the levels of NT-3 spontaneously secreted into the culture medium by primary dissociation cultures at 7 DIV with an enzyme immunoassay. <i>P</i><0.05, one-factor ANOVA. **<i>P</i><0.01, by post-hoc <i>t</i>-test. (J) The amount of NT-3 in the cell lysates of wild-type (white bar, <i>n</i> = 7), CAPS2^+/Δex3 (gray bar, <i>n</i> = 13) and CAPS2^Δex3/Δex3 (black bar, <i>n</i> = 7) cultures was evaluated as indicated in (I). <i>P</i><0.01, one-factor ANOVA. **<i>P</i><0.01, by post-hoc <i>t</i>-test. The error bars indicate the s.e.m.</p

Impairment of short-term synaptic plasticity at PF-PC synapses in the CAPS2^Δex3/Δex3 mouse cerebellum.

<p>(A) Plots showing the relationship between the PF-EPSC amplitude and stimulus intensity applied to PFs in CAPS2^Δex3/Δex3 mice (closed circles; <i>n</i> = 12) and wild-type littermates (open circles; <i>n</i> = 12), at P25–35. Insets show representative EPSC traces evoked by PF stimuli of different intensities. (B–D) The mean paired-pulse ratios recorded from each lobule of P19–20 cerebellar slices were plotted against various interstimulus intervals. Recordings from lobules II–V (wild-type, <i>n</i> = 14; CAPS2^Δex3/Δex3, <i>n</i> = 14), VI–VII (wild-type, <i>n</i> = 12; CAPS2^Δex3/Δex3, <i>n</i> = 16), and IX (wild-type, <i>n</i> = 13; CAPS2^Δex3/Δex3, <i>n</i> = 13) are shown in (B), (C), and (D), respectively. Insets show representative traces obtained from CAPS2^Δex3/Δex3 mice and wild-type littermates. V_h = −80 mV. The error bars indicate the s.e.m. *<i>P</i><0.05, by the Mann–Whitney <i>U</i> test.</p

Distribution of vesicles within PF terminals.

<p>(A, B) Electron micrographs of a PF-PC synapse in the P21 wild-type cerebellum (A) and another in the CAPS2^Δex3/Δex3 cerebellum (B). Scale bars, 400 nm. (C) Quantification of vesicle distribution on the electron micrographs. The distance between vesicles and the active zone is indicated on the x-axis; numbers of vesicles of wild-type (open circles; <i>n</i> = 51) and CAPS2^Δex3/Δex3 (closed circles; <i>n</i> = 54) are represented on the y-axis. The error bars indicate the s.e.m.</p