Nano-and micro-particles are being increasingly used to tune interfacial frictional properties in diverse applications,from friction modifiers in industrial lubrication to enhanced biological fluids in human osteoarth...Nano-and micro-particles are being increasingly used to tune interfacial frictional properties in diverse applications,from friction modifiers in industrial lubrication to enhanced biological fluids in human osteoarthritic joints.Here,we assessed the tribological properties of a simulated synovial fluid enriched with non-spherical,poly lactic-co-glycolic acid(PLGA)microparticles(μPL)that have been previously demonstrated for the pharmacological management of osteoarthritis(OA).Three different μPL configurations were fabricated presenting a 20μm×20μm square base and a thickness of 5μm(thin,5H μPL),10μm(10H μPL),and 20μm(cubical,20H μPL).After extensive morphological and physicochemical characterizations,the apparent Young’s modulus of the μPL was quantified under compressive loading returning an average value of~6 kPa,independently of the particle morphology.Then,using a linear two-axis tribometer,the static(μ_(s))and dynamic(μ_(d))friction coefficients of the μPL-enriched simulated synovial fluid were determined in terms of particle configuration and concentration,varying from 0(fluid only)to 6×10^(5) μPL/mL.The particle morphology had a modest influence on friction,possibly because the μPL were fully squeezed between two mating surfaces by a 5.8 N normal load realizing boundary-like lubrication conditions.Differently,friction was observed to depend on the dimensionless parameterW,defined as the ratio between the total volume of the μPL enriching the simulated synovial fluid and the volume of the fluid itself.Both coefficients of friction were documented to grow withWreaching a plateau of μ_(s)~0.4 and μ_(d)~0.15,already at Ω~2×10^(-3).Future investigations will have to systematically analyze the effect of sliding velocity,normal load,and rigidity of the mating surfaces to elucidate in full the tribological behavior of μPL in the context of osteoarthritis.展开更多
Studying the lubrication properties of osteoarthritis(OA)synovial fluid(SF)enables an understanding of the boundary lubrication joint,mobility,and friction.However,tribology has never been combined with the clinical r...Studying the lubrication properties of osteoarthritis(OA)synovial fluid(SF)enables an understanding of the boundary lubrication joint,mobility,and friction.However,tribology has never been combined with the clinical reality of the presence of worn particles within the synovial fluid and how they affect the osteoarthritic joints.Part of the problem relates to the tribology methods studying friction by applying inadequate pin-on-disc techniques.In this study,synovial fluid with and without worn particles was studied using a customized tribometer.This method enables opening the contact at the end of each cycle and simulates better contact conditions of a natural knee joint and can thus be applied for evaluating the severity of joint OA and the treatment given to the patient.展开更多
文摘Nano-and micro-particles are being increasingly used to tune interfacial frictional properties in diverse applications,from friction modifiers in industrial lubrication to enhanced biological fluids in human osteoarthritic joints.Here,we assessed the tribological properties of a simulated synovial fluid enriched with non-spherical,poly lactic-co-glycolic acid(PLGA)microparticles(μPL)that have been previously demonstrated for the pharmacological management of osteoarthritis(OA).Three different μPL configurations were fabricated presenting a 20μm×20μm square base and a thickness of 5μm(thin,5H μPL),10μm(10H μPL),and 20μm(cubical,20H μPL).After extensive morphological and physicochemical characterizations,the apparent Young’s modulus of the μPL was quantified under compressive loading returning an average value of~6 kPa,independently of the particle morphology.Then,using a linear two-axis tribometer,the static(μ_(s))and dynamic(μ_(d))friction coefficients of the μPL-enriched simulated synovial fluid were determined in terms of particle configuration and concentration,varying from 0(fluid only)to 6×10^(5) μPL/mL.The particle morphology had a modest influence on friction,possibly because the μPL were fully squeezed between two mating surfaces by a 5.8 N normal load realizing boundary-like lubrication conditions.Differently,friction was observed to depend on the dimensionless parameterW,defined as the ratio between the total volume of the μPL enriching the simulated synovial fluid and the volume of the fluid itself.Both coefficients of friction were documented to grow withWreaching a plateau of μ_(s)~0.4 and μ_(d)~0.15,already at Ω~2×10^(-3).Future investigations will have to systematically analyze the effect of sliding velocity,normal load,and rigidity of the mating surfaces to elucidate in full the tribological behavior of μPL in the context of osteoarthritis.
基金The experimental test rig was funded by Maof Fellowships,the Council for Higher Education of Israel(Prof.Haytam KASEM).
文摘Studying the lubrication properties of osteoarthritis(OA)synovial fluid(SF)enables an understanding of the boundary lubrication joint,mobility,and friction.However,tribology has never been combined with the clinical reality of the presence of worn particles within the synovial fluid and how they affect the osteoarthritic joints.Part of the problem relates to the tribology methods studying friction by applying inadequate pin-on-disc techniques.In this study,synovial fluid with and without worn particles was studied using a customized tribometer.This method enables opening the contact at the end of each cycle and simulates better contact conditions of a natural knee joint and can thus be applied for evaluating the severity of joint OA and the treatment given to the patient.
