Direct monitoring of single-cell response to biomaterials by Raman spectroscopy.

There is continued focus on the development of new biomaterials and associated biological testing methods needed to reduce the time taken for their entry to clinical use. The application of Raman spectroscopy to the study of individual cells that have been in contact with biomaterials offers enhanced in vitro information in a potentially non-destructive testing regime. The work presented here reports the Raman spectral analysis of discreet U-2 OS bone cells after exposure to hydroxyapatite (HA) coated titanium (Ti) substrates in both the as-deposited and thermally annealed states. These data show that cells that were in contact with the bioactive HA surface for 7 days had spectral markers similar to those cultured on the Ti substrate control for the same period. However, the spectral features for those cells that were in contact with the annealed HA surface had indicators of significant differentiation at day 21 while cells on the as-deposited surface did not show these Raman changes until day 28. The cells adhered to pristine Ti control surface showed no spectral changes at any of the timepoints studied. The validity of these spectroscopic results has been confirmed using data from standard in vitro cell viability, adhesion, and proliferation assays over the same 28-day culture period. In this case, cell maturation was evidenced by the formation of natural bone apatite, which precipitated intracellularly for cells exposed to both types of HA-coated Ti at 21 and 28 days, respectively. The properties of the intracellular apatite were markedly different from that of the synthetic HA used to coat the Ti substrate with an average particle size of 230 nm, a crystalline-like shape and Ca/P ratio of 1.63 ± 0.5 as determined by SEM-EDX analysis. By comparison, the synthetic HA particles used as a control had an average size of 372 nm and were more-rounded in shape with a Ca/P ratio of 0.8 by XPS analysis and 1.28 by SEM-EDX analysis. This study shows that Raman spectroscopy can be employed to monitor single U-2 OS cell response to biomaterials that promote cell maturation towards de novo bone thereby offering a label-free in vitro testing method that allows for non-destructive analyses.

Reliability of RT3 accelerometer for measuring mobility in people with multiple sclerosis: pilot study.

This pilot study investigated the test-retest reliability of an RT3 accelerometer (RT3) for measuring motion in people with multiple sclerosis (MS). Ten people with MS (mean age 49 yr; Extended Disability Status Scale mean +/- standard deviation = 3.4 +/- 1.3) and ten nondisabled people (mean age 40 yr) wore the RT3 while they performed three discrete mobility tasks on two occasions separated by 1 week. The intraclass correlation coefficients (ICCs) calculated from the RT3 motion data for the group with MS were 0.64 for the 5-minute walk test (p = 0.01), 0.50 for the timed up and go test (p = 0.05), and 0.76 for the stair-climbing task (p = 0.002). For the control group, these values were 0.65 (p = 0.01), -0.04 (p = 0.54), and 0.39 (p = 0.11), respectively. We found that the RT3 can potentially provide stable data when measuring walking, but a more robust, yet participant-friendly, method of attaching the RT3 is required. Both participant groups demonstrated inconsistencies in motor-task performance, highlighting a potential source of measurement error that would need to be addressed when future studies are designed. Based on the results of the 5-minute walk test in this study, a sample of 53 participants would be required to obtain an ICC value with a 95% confidence interval of width 0.2 using two repeat measurements.