Generation of a large volume of clinically relevant nanometre-sized ultra-high-molecular-weight polyethylene wear particles for cell culture studies.

It has recently been shown that the wear of ultra-high-molecular-weight polyethylene in hip and knee prostheses leads to the generation of nanometre-sized particles, in addition to micron-sized particles. The biological activity of nanometre-sized ultra-high-molecular-weight polyethylene wear particles has not, however, previously been studied due to difficulties in generating sufficient volumes of nanometre-sized ultra-high-molecular-weight polyethylene wear particles suitable for cell culture studies. In this study, wear simulation methods were investigated to generate a large volume of endotoxin-free clinically relevant nanometre-sized ultra-high-molecular-weight polyethylene wear particles. Both single-station and six-station multidirectional pin-on-plate wear simulators were used to generate ultra-high-molecular-weight polyethylene wear particles under sterile and non-sterile conditions. Microbial contamination and endotoxin levels in the lubricants were determined. The results indicated that microbial contamination was absent and endotoxin levels were low and within acceptable limits for the pharmaceutical industry, when a six-station pin-on-plate wear simulator was used to generate ultra-high-molecular-weight polyethylene wear particles in a non-sterile environment. Different pore-sized polycarbonate filters were investigated to isolate nanometre-sized ultra-high-molecular-weight polyethylene wear particles from the wear test lubricants. The use of the filter sequence of 10, 1, 0.1, 0.1 and 0.015 µm pore sizes allowed successful isolation of ultra-high-molecular-weight polyethylene wear particles with a size range of < 100 nm, which was suitable for cell culture studies

The zeta potential of laolin suspensions measured by electrophoresis and electroacoustics

Zeta potenciál zředěných a koncentrovaných kaolinových disperzí byl pozorován metodou elektroforézy a elektroakusticky. Vliv přídavku soli (KCl), a polymerního materiálu (Triton X-100) a anionického tenzidu (Sodium dodecylsulfátu, SDS) na vlastnosti suspenze byl studován elektroforetickými metodami. Elektroakustické metody byly použity pro měření zeta potenciálu pro nejvyšší možné koncentrace kaolinu v suspenzi a byl pozorován také vliv zřeďování. Vliv stárnutí čerstvě připravených vzorků a izoelektrický bod kaolinu byly také studovány. Použitím obou technik bylo zjištěno, že pro tento typ disperzí nebyl detegován izoelektrický bod, jenom maximum v hodnotě zeta potenciálu pro suspenzi kaolinu. Tato maxima byla pozorována také po přídavku Triton X-100 a SDS. Se zvyšující se koncentrací KCl a SDS ve vodní suspenzi se tato maxima posouvají více do kyselé oblasti, přičemž v přítomnosti Triton X-100 se poloha maxima zeta potenciálu nemění a zůstává konstantní. Elektroakustickými technikami bylo zjištěno, že čerstvě připravené koncentrované suspenze vyžadují kolem 6 hodin pro ustálení hodnoty zeta potenciálu. Zřeďování koncentrovaných suspenzí vedlo ke snížení zeta potenciálu tím, že ionty se vážou na desorbovaný povrch, čímž stlačují povrchový náboj. Maxima zeta potenciálu zůstala nezměněna také po zahřátí prášku v žíhací peci při teplotě 200°C (pro odstranění organických zbytků), což naznačuje nejmožnější vysvětlení vzniklých maxim jako důsledek izomorfní substituce.The zeta potentials of kaolin dilute and concentrated suspensions were monitored using the techniques of electrophoresis and electroacoustics, respectively. The effect of addition of salt (KCl), a polymer material (Triton X-100), and an anionic surfactant (sodium dodecyl sulphate, SDS) on the suspension properties was investigated by electrophoresis. Electroacoustics was employed for the measurement of zeta potentials for the highest possible kaolin content in suspension and the effect of dilution. The effect of aging of a freshly prepared sample and kaolin isoelectric point was also studied. Using both techniques it was noted that there was no isoelectric point, just a maximum value in the magnitude of the kaolin suspension zeta potential. These maxima were observed also in the presence of Triton X-100 and SDS. An increase of the concentration of KCl and SDS in suspension shifted the maxima towards more acidic values, while in the presence of Triton X-100 the position of the zeta potential maxima remained constant. Electroacoustic techniques revealed that a freshly prepared concentrated suspension requires about six hours to equilibrate to achieve a steady zeta potential. Diluting the concentrated suspensions led to decrease of the zeta potential as ions bound to the surface desorbed and screened the surface charge. The zeta potential maxima remained unchanged even after heating the powder in an oven at 200 degrees C (to remove any organic material) thereby suggesting that the most likely explanation for the maxima is isomorphic substitution