In-situ Synthesis And Properties Of Polyvinyl Alcohol/Hydroxyapatite Composite Microspheres

As an inorganic material,hydroxyapatite has a similar chemical composition and structure to that of the hard tissues in a living body.Due to its good meachical properties,biological activity and biocompatibility,it has been widely used in the bioengineering of bone tissue.Polyvinyl alcohol?PVA?is one of the most widely used polymers in various biomedical applications.It has good biocompatibility and biodegradability and is widely used in bioengineering such as articular cartilage and artificial cornea.Therefore,the combination of PVA and HA is one of the most effective methods to achieve a suitable biomaterial with good mechanical properties,biological activity as well as well-adjusted biodegradability.A series of PVA/HA composite microspheres were prepared by the in-situ synthesis combined emulsification cross-linking method.The effects of different experimental parameters on the preparation and morphology of the PVA/HA composite microspheres were investigated,and the optimal parameters of preparing the composite microspheres were determined.Based on the above experiments,the PVA/SiO₂/HA composite microspheres were successfully prepared by the same method,and the effects of the experimental parameters on the morphology and properties of the composite microspheres were also discussed.The research results obtained in this paper are as follows:?1?The PVA/HA composite microspheres with an average particle size of 39.0?m,uniform structure and spherical regularity were successfully synthesized in the water-in-oil system by emulsion cross-linking method.The preparation parameters were as follows:the concentration of concentrated HCl was 300?L;the amount of glutaraldehyde?25%GA?as the crosslinking agent was 75?L;the amount of Span 80as the emulsifier was 1 g;the concentration of PVA was 7%;and the concentration of NaOH was 4 mol/L;HA content is 20%by weight.?2?The drug loading andrelease properties of the PVA/HA composite microspheres were evaluated by using vancomycin hydrochloride?VH?as a drug-loading model.Compared to pure PVA microspheres,PVA/HA composite microspheres exhibit superior drug loading capacity and drug encapsulation efficiency as well as longer lasting drug release behavior.The cumulative amount of VH released by the PVA-10%HA,PVA-20%HA and PVA-30%HA composite microspheres was 57.7%,60.8%and 48.6%of the initial drug amount,respectively,which was higher than the corresponding value of pure PVA microspheres?44.5%?.In addition,the PVA/HA composite microspheres were observed to have good ability to form bone-like apatite in vitro by immersion in 1.0 times SBF solution for 3 days.?3?Based on the preparation conditions of the PVA/HA composite microspheres,certain experimental parameters were changed,and the PVA/SiO₂/HA composite microspheres were also successfully prepared by the in-situ synthesis combined emulsion-crosslinking method.However,the optimal amount of glutaraldehyde?25%GA?was changed to be 60?L,and the PVA concentration was adjusted to be 6%.When the mass ratio of PVA,SiO₂ and HA was 7:2:1,the composite microspheres exhibited the best morphology,with the inorganic content of 23.1%,an average particle size of 12.3?m,regularly spherical shape andhigh dispersibility.?4?The as-prepared PVA/SiO₂/HA composite microspheres were observed to have better ability to form bone-like apatite in vitro by immersing in 1.0 times SBF solution for 3 days.Compared with both the PVA/SiO₂ and PVA/HA composite microspheres,the PVA/SiO₂/HA composite microspheres have a more sustained release behavior,with the final cumulative VH release of 81.9%.