Raman ratios on the repair of grafted surgical bone defects irradiated or not with laser (λ780 nm) or LED (λ850 nm)

• Repair of large bone defects may be timing consuming and improper.
• We studied the effects of association of biomaterial and IR Laser or IR LED light.
• Raman metrics indicate of a positive effect of the association on the repair.
• The mineralization was intense in grafted defects at early remodeling time.
• Collagen level decreased with time and bone mineralization.

This work aimed to assess biochemical changes associated to mineralization and remodeling of bone defects filled with Hydroxyapatite + Beta-Beta-tricalcium phosphate irradiated or not with 2 light sources. Ratios of intensities, band position and bandwidth of selected Raman peaks of collagen and apatites were used. Sixty male Wistar rats were divided into 6 groups subdivided into 2 subgroups (15th and 30th days). A standard surgical defect was created on one femur of each animal. In 3 groups the defects were filled with blood clot (Clot, Clot + Laser and Clot + LED groups) and in the remaining 3 groups the defects were filled with biomaterial (Biomaterial, Biomaterial + Laser and Biomaterial + LED groups). When indicated, the defects were irradiated with either Laser (λ780 nm, 70 mW, Φ ∼ 0.4 cm2) or LED (λ850 ± 10 nm, 150 mW, Φ ∼ 0.5 cm2), 20 J/cm2 each session, at 48 h intervals/2 weeks (140 J/cm2 treatment). Following sacrifice, bone fragments were analyzed by Raman spectroscopy. Statistical analysis (ANOVA General Linear Model, p < 0.05) showed that both grafting and time were the variables that presented significance for the ratios of ∼1660/∼1670 cm−1 (collagen maturation), ∼1077/∼854 cm−1 (mineralization), ∼1077/∼1070 cm−1 (carbonate substitution) and the position of the ∼960 cm−1 (bone maturation). At 30th day, the ratios indicated an increased deposition of immature collagen for both Clot and Biomaterial groups. Biomaterial group showed increased collagen maturation. Only collagen deposition was significantly dependent upon irradiation independently of the light source, being the amount of collagen I increased in the Clot group at the end of the experimental time. On the other hand, collagen I deposition was reduced in biomaterial irradiated groups. Raman ratios of selected protein matrix and phosphate and carbonate HA indicated that the use of biphasic synthetic micro-granular HA + Beta-TCP graft improved the repair of bone defects, associated or not with Laser or LED light, because of the increasing deposition of HA.

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