Cortical bone composition and orientation as a function of animal and tissue age in mice by Raman spectroscopy.

Important aspects of bone tissue quality include the physicochemical properties of its main constituents, the organic matrix and the mineral crystals. One of the most commonly reported measurements of Raman analysis of bone is the mineral to matrix ratio, obtained from the ratio of the integrated areas of any of the phosphate and amide peaks which depend on both tissue organization and composition. Cube-like samples of normal mouse cortical bone taken from the diaphysis and metaphysis of the femur were investigated within different age groups (2, 4, 8 and 12 weeks) by Raman microspectroscopy. Anatomically identical bone in both longitudinal and transverse directions was analyzed, enabling the discrimination between orientation and composition changes both as a function of animal age, and tissue age within the same animal. The results of the present study indicate that there is a parallel evolution of both orientation and chemical composition as a function of animal age, as well as tissue age within the same specimen. Our tissue age modified ratio of the carbonate to phosphate Raman peaks suggests that the bone mineral crystallite maturity remains relatively constant with animal age. Comparisons of polarized and depolarized experiments in the transversal plane of the diaphysis show a lack of orientation effects as a function of tissue age within the same animal, but exhibit differences as a function of animal age. In the metaphysis, the orientation effect is evident too, albeit less pronounced. This is most likely due to either the age difference between the two tissues within the same specimen in the long bone axis, as metaphyseal bone is generally younger than diaphyseal, or the more random orientation of the tissue collagen itself.

Raman imaging of two orthogonal planes within cortical bone.

The lamellar bone's strength is mainly affected by the organization of its mineralized collagen fibers and material composition. In the present study, Raman microspectroscopic and imaging analyses were employed to study a normal human femoral midshaft bone cube-like specimen with a spatial resolution of approximately 1-2 microm. Identical bone lamellae in both longitudinal and transverse directions were analyzed, which allowed us to separate out orientation and composition dependent Raman lines, depending on the polarization directions. This approach gives information about lamellar bone orientation and variation in bone composition. It is shown that the nu1 PO4 to amide I ratio mainly displays lamellar bone orientation; and nu2 PO4 to amide III and CO3 to nu2 PO4 ratios display variation in bone composition. The nu2 PO4 to amide III ratio is higher in the interstitial bone region, whereas the CO3 to nu2 PO4 ratio has lower values in the same region. The present study provides fresh insights into the organization of a lamellar bone tissue from two orthogonal orientations.

Complementary information on in vitro conversion of amorphous (precursor) calcium phosphate to hydroxyapatite from Raman microspectroscopy and wide-angle X-ray scattering.

In addition to mechanical functions, bones have an essential role in metabolic activity as mineral reservoirs that are able to absorb and release ions. Bioapatite, considered the major component in the mineralized part of mammalian bones, is a calcium phosphate mineral with a structure that closely resembles hydroxyapatite (HA, Ca10[PO4]6[OH]2) with variable chemical substitutions. It is important to note that it continues to be chemically active long after it has been initially deposited. Detailed understanding of changes in the mineral phase as HA matures is essential for understanding how normal bone achieves its remarkable mechanical performance, how it is altered in disease, as well as the effects of therapeutic interventions. A model system for investigation of the in vivo maturation of HA is available, namely, the in vitro conversion of amorphous calcium phosphate (ACP) to HA in a supersaturated solution of calcium and phosphate ions. In the present study, this system was employed to correlate with the changes in chemistry and poorly crystalline HAP crystal size, shape, and habit. The results of the X-ray diffraction as well as Raman analyses showed that as the crystallites mature in the 002 and 310 directions both the full width at half-height and wavelength at maximum of the Raman peaks change as a function of reaction extent and crystallite maturation, size, and shape. Moreover, such analyses can be performed in intact bone specimens through Raman microspectroscopic and imaging analyses with a spatial resolution of 0.6-1 mu, by far superior to the one offered by other microspectroscopic techniques, thus potentially yielding important new information on the organization and mineral quality of normal and fragile bone.

Bone osteonal tissues by Raman spectral mapping: orientation-composition.

Bone is a composite material with a hierarchical structure. Its strength depends on its structural and material properties. In the present study, Raman microspectroscopic and Imaging analyses were employed to study 12 osteons in tissue sections from the femoral midshaft of a healthy human female, with a spatial resolution of approximately 1mum. Spatial changes in amount of mineral and organic matrix, as well as the variation in the mineral content were determined, imaged, and plotted as a function of the polarization of incident light. The results showed that the prominent bands, such as nu(1) PO(4) and amide I, commonly used for the determination of mineral and organic compositions, are quite sensitive to the orientation and the polarization direction of the incident light. On the other hand, bands such as amide III, nu(2) PO(4) and nu(4) PO(4) are less susceptible to the orientational effects. As a result, exclusive consideration of the nu(1) PO(4) and amide I bands for the calculation of material properties might lead to erroneous conclusions. Amide III, nu(2) PO(4) and nu(4) PO(4) Raman bands should also be taken into consideration for compositional analysis of bone structures, especially ones with unknown orientational features. Moreover, the results of the present study demonstrate the versatility of the analytical technique, and provide insights into the organization of bone tissue at the ultrastructural level.

Surface oxidation of polyethylene fiber reinforced polyolefin biomedical composites and its effect on cell attachment.

Three different compositions of butene-ethylene copolymer composites reinforced by polyethylene fibers and produced by filament winding are potentially suitable for biomedical applications. This study examines the effect of various processing and finishing conditions and of sterilization on the extent and composition of surface oxidation. An XPS analysis revealed only insignificant differences between the various treatments, while fibroblast cell attachment tests indicated good attachment with no signs of cytotoxity or cell degeneration for any of the materials.