Study On Preparation And Properties Of PMMA Bone Cement

PMMA has been widely used in surgical implantation because of its good plasticity,chemical inertia and mechanical properties.Methyl methacrylate（MMA）is the main components of PMMA bone cement monomer and an important raw material when synthesizing other products.At present,the production of MMA is mainly concentrated in developed countries such as Japan,Western Europe and the United States.The domestic production obviously can not meet the market demand.Therefore,it is necessary to design and prepare new catalysts for catalytic synthesis of MMA;Radiopacifier is an indispensable part of bone cement.It will have a serious destruction on the mechanical properties of bone cement and reduce the service life of bone cement because of its poor compatibility.Therefore,it is necessary to make new modification research on the basis of traditional radiopacifier to keep good visibility and improve the mechanical properties of bone cement.PMMA bone cement with antibiotics can effectively kill bacteria,avoid tissue infection and prolong the service life of bone cement.However,practical studies have found that only about 5%of antibiotics can be released,and most of them were trapped in the cement matrix.Therefore,it is particularly important to develop a new type of bone cement that can significantly enhance drug release.This topic takes PMMA bone cement as the research object,mainly including the following three aspects:（1）A novel surface-functionalized SBA-15 coordination supported Pd catalyst was designed and prepared for one-step oxidation esterification of methacrolein（MAL）to MMA（monomers of PMMA）.The factors affecting the reaction were optimized.It was found that the yield of MMA could reach 25.8%under the conditions of temperature 50^oC,oxygen pressure 0.3 MPa,reaction time 2 h and catalyst amount 50 mg.（2）ZrO₂ particles with an average diameter approximately 2μm was prepared by hydrothermal reaction and functionalized in organic solvents using a di-functional surface modification agent,3-methacrylopropyltrimethoxysilane（MPS）.Surface-functionalized ZrO₂particles were investigated by a variety of characterization methods.Furthermore,fabrication of PMMA bone cement was conducted with MPS-functionalized ZrO₂ particles as a inorganic filler.ZrO₂ particles with surface vinyl groups exhibited good compatibility in the fabricated bone cement,leading to an improved bending strength of the PMMA bone cement.The MPS-functionalized ZrO₂ particles,as a kind of filler,may be a potential candidate for the PMMA bone cement.（3）To achieve sustained and efficient release of drugs,SBA-15 was modified with chitosan（CS）,polyvinyl alcohol（PVA）and polyethylene glycol（PEG）respectively,and the modified SBA-15 was then used as a drug carrier in PMMA bone cement.Comparing with the modifiers of CS and PVA,the presence of PEG in PMMA bone cement has the best effect on the release of 37%of gentamicin（GTMC）in 70 days.We found that the release of GTMC was greatly improved（up to 77%）when the mass ratio of PEG/SBA-15 was 30%.As a comparison,the release of GTMC was not obviously increased in the PMMA bone cement formulated with SBA-15（up to 18%）or PEG（up to 42%）.while the high content of SBA-15shown deterimental to the mechanical properties although the release of GTMC can be substantially increased.However,the mechanical properties did not show a significant change with increasing mass ratio of PEG/SBA-15.It indicated that the synergism of PEG and SBA-15 not only can greatly enhance drug release but also can maintain good mechanical properties.The combination of sustainable drug release efficiency and good mechanical properties demonstrate the potential applicability of PEG/SBA-15-functionalized PMMA bone cement for orthopedic surgery to prevent post-surgery infection.