Imaging techniques that allow proteins to be examined in situ show much promise for determining the extent and physical characterization of protein on contact lens materials. These techniques indicate that the pattern of deposition of proteins onto silicone hydrogel contact lens materials differs between materials, depending upon their bulk and surface composition.

We have used localized surface plasmon resonance (LSPR) to monitor the structural changes that accompany thermal denaturing of bovine serum albumin (BSA) adsorbed onto gold nanospheres of size 5nm-60nm. The effect of the protein on the LSPR was monitored by visible extinction spectroscopy. The position of the resonance is affected by the conformation of the adsorbed protein layer, and as such can be used as a very sensitive probe of thermal denaturing that is specific to the adsorbed protein. The results are compared to detailed calculations and show that full calculations can lead to significant increases in knowledge where gold nanospheres are used as biosensors. Thermal denaturing on spheres with diameter > 20 nm show strong similarity to bulk calorimetric studies of BSA in solution. BSA adsorbed on nanospheres with d [Symbol: see text] 15nm shows a qualitative difference in behavior, suggesting a sensitivity of denaturing characteristics on local surface curvature. This may have important implications for other protein-nanoparticle interactions.

Differences between wear-scar features of simulator-tested and retrieved tibial total knee replacement (TKR) liners have been reported. This disagreement may result from differences between in vivo kinematic profiles and those defined by the International Organization for Standardization (ISO). The purpose of this study was to determine the knee kinematics of a TKR subject group during level walking and compare them with the motion profiles defined by the ISO standard for a displacementcontrolled knee wear testing simulator. Twenty-nine patients with a posterior cruciate ligamentretaining TKR design were gait tested using the point cluster technique to obtain flexion-extension (FE) rotation, anterior-posterior (AP) translation and internal-external (IE) rotation knee motions during a complete cycle of level walking. Relative ranges of motion and timing of key points within the in vivo motion data were compared against the same ranges and same key points from the input profiles of the displacement-controlled wear testing standard ISO14243-3. The subjects exhibited a FE pattern similar to ISO, with an insignificant difference in range of FE rotation from midstance to terminal stance. However, the subjects had a significantly higher range of knee flexion from terminal stance into swing. The subjects also exhibited a phase delay for the entire gait cycle. For AP translation, the standard profile had statistically significant lower magnitudes than seen in vivo. Opposite pattern of AP motion was also apparent from midstance and swing. Similarly, ISO specified a smaller IE total range of rotation with a motion pattern in complete opposition to that seen in vivo. In conclusion, significant differences were found in both the magnitudes and pattern of in vivo motion compared with ISO.

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Background Differences between wear-scar features of simulator-tested and retrieved tibial total knee replacement (TKR) liners have been reported. This disagreement may result from differences between in vivo kinematic profiles and those defined by the standard. Purpose To determine the knee kinematics of a TKR subject group during level walking and compare them with the motion profiles produced by a wear test conducted according to the force-controlled knee wear testing ISO 14243-1 (ISO-1)standard. Methods Ten patients with a posterior cruciate ligament-retaining TKR design were gait tested using the point cluster technique (PCT) to obtain flexion-extension (FE) rotation, anterior-posterior (AP) translation and internal-external (IE) rotation motions during a complete cycle of level walking. Motion data were directly compared against the output kinematics from the wear test. Results The subjects exhibited a FE rotation pattern similar to the output from ISO-1; however had higher midstance knee flexion angles. For both AP translation and IE rotation, the standard profiles had significantly smaller total ranges of motion than seen in vivo, with noticeably different patterns of motions. Conclusions For this particular implant design, significant differences were found in both the pattern and magnitudes of in vivo motion during level walking compared with the ISO-1 standard.