Effect Of Dispersion Method On The Characteristic Of Drug-Loaded Uhmwpe

It has been well reported that the ultra-high molecule weight polyethylene (UHMWPE) wear particles was the major concern for the osteolysis and further resulted in asepetic loosening for total joint replacement. UHMWPE loaded with alendronate (ALN) which was anti-osteolysis drugs in clinic were developed and expected that the drugs in UHMWPE acetabular cup could be released with the inevitable UHMWPE wear particles under the normal wear condition to prevent the particle-induced osteolysis. In our previous studies, the dispersion of ALN in UHMWPE ununiformly can result in the decrease of mechanical properties. The aim of this study is to find a better way to manufacture the samples(UHMWPE, ALN/UHMWPE, ALN/F68/UHMWPE) and expected to enhance the behaviors of as-received three different samples.Orthogonal design with four factors containing three levels was employed to determine the optimum processing conditions. The range analyses and analyses of variance (ANOVA) of tensile strength and broken elongation were carried out by Statistical Product and Service Solutions (SPSS). The energy dispersive X-Ray (EDX), secondary electron microscopy (SEM) and time-of-flight secondary ion mass spectrometry analysis (TOF-SIMS) were used to analyze the element distribution of ALN in the surface of as-received ALN/UHMWPE and ALN/F68/UHMWPE. The orthogonal design combined with statistical analyses revealed that the optimal processing conditions for uniform dispersion of ALN in UHMWPE were:surfactant (F68), ultra sonic dispersion,1wt%bALN,37°C. ANOVA shows a significant difference. The results of EDS,SEM and SIMS indicated that the addition of F68promoted the more uniform distribution of ALN in ALN/F68/UHMWPE.The three samples were manufactured by hot-press according to the optimum processing contions. The tensile test indicated that both tensile strength and broken elongation of ALN/F68/UHMWPE were increased compared with those of ALN/UHMWPE. The results of small punch test revealed that the additivity of F68effectively improved the work failure of ALN/F68/UHMWPE. The X-Ray Diffraction (XRD) and differential scanning calorimetry (DSC) demonstrated that the crystallinity of ALN/F68/UHMWPE was slightly higher than that of ALN/UHMWPE, and no phase or melting behaviors were observed after the addition of ALN and F68.Tribological properties were determined by pin-on-disc wear testing. The wear mechanism of the three specimen were explored by SEM to examine the worn surfaces and analyzed the effect of the additive F68on the micro structure and further on the properties of friction and wear of the three different samples. By adding surfactant (F68), the friction coefficient, volume of wear scar and morphology of ALN/F68/UHMWPE were compared with ALN/UHMWPE. The results demonstated that the friction coefficient, volume of wear scar and morphology of ALN/F68/UHMWPE were similar with those of UHMWPE whereas were higher than those of ALN/UHMWPE under identical lubricant and normal load. These results revealed that the agglomeration of ALN could probably cause the different morphology and the decrease in wear resistance of ALN/UHMWPE. It revealed that the addition of F68promoting the tribology properties of ALN/F68/UHMWPE.The mean sizes of UHMWPE, ALN/UHMWPE and ALN/F68/UHMWPE wear debris were range from30μm-40μm after filtration. The results of the cell culture indicated that the ALN/UHMWPE wear debris could promote the proliferation and the ALP expression of osteoblasts in some certain dosages. The addition of F68for UHMWPE loaded with ALN showed no significant difference as compared with ALN/UHMWPE. The ALN/UHMWPE and ALN/F68/UHMWPE wear debris both could inhibit the expression of IL-6at some dosages in the present study, which indicated that the ALN in ALN/UHMWPE might play a role in the treatment of the osteolysis in artificial hip joint and the effect of ALN could not been changed by the addition of F68.The present study indicated that the ALN/F68/UHMWPE manufactured from the optimum proceesing conditions possessed the better mechanical properties and wear performance compared to the control of ALN/HMWPE. ALN/F68/UHMWPE might be used as the potential implanted drug carrier to prevent the particle-induced osteolysis in joint replacements. Moreover the ALN/F68/UHMWPE wear debris could directly promote the proliferation of osteblasts and inhibit the secretion of the osteolysis factor IL-6. Therefore it might prevent the osteolysis and prolong the lifetime of the artificial hip joint finally.