We have designed an environmentally-controlled chamber for near infrared spectroscopic imaging (NIRSI) to monitor changes in cortical bone water content, an emerging biomarker related to bone quality assessment. The chamber is required to ensure repeatable spectroscopic measurements of tissues without the influence of atmospheric moisture. A calibration curve to predict gravimetric water content from human cadaveric cortical bone was created using NIRSI data obtained at six different lyophilization time points. Partial least squares (PLS) models successfully predicted bone water content that ranged from 0–10% (R = 0.96, p < 0.05, root mean square error of prediction (RMSEP) = 7.39%), as well as in the physiologic range of 4–10% of wet tissue weight (R = 0.87, p < 0.05, RMSEP = 14.5%). Similar results were obtained with univariate and bivariate regression models for prediction of water in the 0–10% range. Further, we identified two new NIR bone absorbances, at 6560 cm −1 and 6688 cm −1 , associated with water and collagen respectively. Such data will be useful in pre-clinical studies that investigate changes in bone quality with disease, aging and with therapeutic use.

Applications of vibrational spectroscopy to assess bone disease and therapeutic interventions are continually advancing, with tissue mineral and protein composition frequently investigated. Here, we used two spectroscopic approaches for determining bone composition in a mouse model of the brittle bone disease osteogenesis imperfecta (OIM) with and without antiresorptive agent treatment (alendronate (ALN) and RANK-Fc). Near infrared (NIR) spectral analysis via a fiber optic probe and Fourier transform infrared spectroscopy using attenuated total reflection (FTIR-ATR) mode were applied to investigate bone composition, including water, mineral and protein content. Spectral parameters revealed differences among the control wildtype (WT) and OIM groups. NIR spectral analysis of protein and water showed that OIM mouse humerii had ~ 50% lower protein and ~ 50% higher overall water content compared to WT bone. Moreover, some OIM treated groups showed a reduction in bone water compared to OIM controls, approximating values observed in WT bone. Differences in bone quality based on increased mineral content and reduced carbonate content were also found between some groups of treated OIM and WT bone, but crystallinity did not differ among all groups. The spectroscopically-determined parameters were evaluated for correlations with gold-standard mechanical testing values to gain insight into how composition influenced bone strength. As expected, bone mechanical strength parameters were consistently up to three-fold greater in WT mice compared to OIM groups, except for stiffness in the ALN-treated OIM groups. Further, bone stiffness, maximum load and post-yield displacement showed the strongest correlations with NIR-determined protein content (positive correlations) and bound-water content (negative correlations). These results demonstrate that in this study, NIR spectral parameters were more sensitive to bone composition differences than ATR parameters, highlighting the potential of this nondestructive approach for screening of bone diseases and therapeutic efficacy in pre-clinical models.