전기방사를 이용한 하이드록시아파타이트 (HAp) / poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHB-HHx) 나노복합체의 제조

Abstract

This research investigates new methods for fabrication of hydroxyapatite (HAp) /poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHB-HHx) nanocomposites through electrospinning process. This research also introduces an original technique to synthesize HAP through microwave in a commercial microwave oven. It was concluded that microwave assisted synthesis of HAP with calcium hydroxide and phosphoric acid could be a considerable process to prepare the nanocrystalline HAP (nHAP). The result of BET analysis implies that the prepared nHAP have the mesoporosity and high BET specific surface area. By means of DLS analysis and photographs taken after 24 hrs of mixtures, it can be inferred that there is in order for the dispersion stability of HAP prepared by microwave assisted synthesis: methanol > ethanol > n-propanol > chloroform > i-propanol > distilled water. The HAP dispersed in methanol have the best dispersion stability. In conclusion, it can be insisted that this instant microwave assisted synthesis is a considerable, suitable, and facile process to obtain the nHAP as well as they can be used in the multifarious medical fields since there are no by-products which cause side effects It was prepared the PHBHHx nanofibrous webs with the co-solvent system as well as explained the reason why the diameters were increased at the concentration of 40wt% of alcohols through Hansen solubility parameter (HSP) and relative energy difference (RED). It was found that there was some probabilistic relation between the diameter of electrospun nanofibers and their specific REDCF. This means that the solubility with concentration of alcohols has some limitation where the reverse effect was occurred. At the lowest of REDCF, the each concentration of co-solvents was calculated that were 17.8, 21.5, 27.3 and 33.2 wt% for methanol, ethanol, n-propanol and i-propanol, respectively. In order to rationalize and explain the electrospinnability, the relative electrospinnability (RESA) was employed. It was based on the concept that the electrospinnability was connected with not only the moving force polymer particle in electrospinning solution but also the surface tension of electrospinning solution. With plotting of RESA on the concentraion of PHBHHx, it was highly probable just like the specific viscosity method for the decision of proper polymer concentration. In addition, it was found that there was a good correlation between the RESA and the distance to jet instability by means of the photos of the distance to jet instability with the concentration of methanol that was taken by CCD camera. The coefficient of determination, r2, was 0.9763 between RESA and the distance to jet instability. As we know, the moving track of the electrospun and/or electrosprayed polymer was divided zone of arrangement (slow acceleration) and zone of transition between liquid and solid (rapid acceleration). With the scientific intuition, it could be inferred that RESA was related with the point of intersection between slow acceleration zone and rapid acceleration zone. Accordingly, the control or RESA with solution variables, environment variables and process variable could be very important for the managing of electrospinning process. These results highly recommended the usage of 10 wt% of methanol for best co-solvent system of electrospinning PHBHHx. HAP/PHBHHx composites were prepared through electrospinning method and advanced in vitro test in the SBF. As above, we prepared the electrospinning solution for HAP/PHBHHx composite. First, the prepared HAP by microwave assisted synthesis was dispersed in methanol. Second, its supernatant was taken and mixed with chloroform. Third, 8 wt% of PHBHHx was dissolved in chloroform/methanol (90/10 wt%) for the electrospinning solution. By means of the SEM/EDX analysis, the HAP were well dispersed in the PHBHHx matrix since the HAP dispersed in methanol had a best mobility and dispersion stability. From the variation of both pH and weights, it was speculated that there should be a competition between the hydrolysis of polymer and the nucleation of HAP in SBF. Briefly, the alkaline condition of SBF (pH 7.4) induced hydrolysis and then calcium ions were bonded with the hydrolyzed surface of the PHBHHx next to bonding of the HPO42-. After soaking sufficiently, the formation of bonelike apatite has been developed on the surface of the nHAP/PHBHHx composite. So, the nHAP/PHBHHx composite was established that contained hydroxyapatite particles the inner and outer of the surface. As we know, applying to bone tissue regeneration, not only the polymer must be degraded but also the embedded HAP must be resorbed into human body with the manner of sustained release. So, it can be said that the prepared composites has a potential to be applied with the bone tissue regeneration.