A Polarized Raman Spectroscopic Method for Advanced Analyses of the Osteon Lamellar Structure of Human Bone.

Raman spectroscopy has recently been used for quantitative analyses of cortical bone tissue and related materials, such as dentin and enamel. While those analyses have proven useful as potential diagnostic tools, the Raman spectrum of bone encrypts a wealth of additional molecular scale details about structure and crystal arrangement, which are yet to be unfolded. Such details directly link to both bone physiology and pathology. In this work, a triple monochromator spectrometer with high spectral resolution, employed in polarized light configurations, was used to extract quantitative details about the preferential crystallographic orientation of apatite and collagen components in a human proximal femoral cortical bone sample. This body of information was then used to model the bone structure at the nanometric scale through a methodology that could be key in assessments of bone structure in health and disease.

Cytotoxicity and osteogenic effects of aluminum ions.

In this study, we monitored the effect of Al3+ ions on mesenchymal cells (KUSA-A1) and human fibroblasts (NHDF) by means of in vitro experiments by culturing the cells with addition of small concentrations of aluminum ions (i.e., 0.1, 1, 10, and 100 ppm). Bone formation test was then conducted using KUSA-A1. Small concentrations of aluminum ions delayed but did not completely inhibit cell proliferation. The amount of bone tissue decreased as the concentration of Al3+ increased and crystallinity changes were also detected by Raman spectroscopic experiments. Moreover, Al3+ ions greatly affected both structure and chemistry of bone tissues with mineral nodules becoming larger and atomic substitution of Ca with Al in bone tissue being more preponderant with increasing Al3+ concentration. Such effects in turn impaired the balance between mineral and collagen in the formed bone tissue.

Innovative electrospun PCL/fibroin/l-dopa scaffolds scaffolds supporting bone tissue regeneration.

Poly-caprolactone is one of the most promising biocompatible polymers on the market, in particular for temporary devices that are not subjected to high physiological loads. Even if completely resorbable in various biological environments, poly-caprolactione does not play any specific biological role in supporting tissue regeneration and for this reason has a limited range of possible applications. In this preliminary work, for the first time l-dopa and fibroin have been combined with electrospun poly-caprolactone fibers in order to induce bioactive effects and, in particular, stimulate the proliferation, adhesion and osteoconduction of the polymeric fibers. Results showed that addition of low-molecular weight fibroin reduces the mechanical strength of the fibers while promoting the formation of mineralized deposits, when testedin vitrowith KUSA-A1 mesenchymal cells. l-dopa, on the other hand, improved the mechanical properties and stimulated the formation of agglomerates of mineralized deposits containing calcium and phosphorous with high specific volume. The combination of the two substances resulted in good mechanical properties and higher amounts of mineralized deposits formedin vitro.

PCA-Assisted Raman Analysis of Osteonecrotic Human Femoral Heads.

Osteonecrosis of the femoral head (ONFH) occurs frequently in adolescents and young adults and causes progressive deformation and destruction of the hip joint and impairs standing and walking, resulting in a significant decrease in the quality of life of patients. In addition, studies have shown that a history of corticosteroid administration and heavy alcohol consumption are closely related to the occurrence of ONFH. However, the detailed mechanism by which steroid administration and alcohol consumption are associated with the development of the disease is still unknown. With many researches still ongoing and without a clear biological pathway for osteonecrosis, effective preventive measures cannot be taken. Therefore, the current focus of ONFH treatment is to establish an early diagnosis and treatment strategy. We obtained the femoral heads of four patients with steroidal ONFH and three patients with alcoholic ONFH. We then compared the femoral heads of steroidal and alcoholic osteonecrosis by analyzing them at the molecular level by Raman spectroscopy. Crystallographic changes (deformations) in the mineral phase and fraction of organic material respect to the total mass were then plotted as a function. We found that changes in bone composition in ONFH were different in steroidal and alcoholic ONFH. We conclude that this suggests that the developmental mechanisms of steroidal and alcoholic ONFH may follow different paths. We also noticed that while steroid seem to lead to a more marked degradation of the tissue, alcohol seem to affect also the quality of the healthy tissue.

Antibacterial Property of Cellulose Acetate Composite Materials Reinforced with Aluminum Nitride.

Cellulose acetate (CA) is a synthetic compound that is derived from the acetylation of cellulose. CA is well known as it has been used for many commercial products such as textiles, plastic films, and cigarette filters. In this research, antibacterial CA composites were produced by addition of aluminum nitride (AlN) at different weight percentage, from 0 wt. % to 20 wt. %. The surface characterization was performed using laser microscope, Raman and FTIR spectroscopy. The mechanical and thermal properties of the composite were analyzed. Although the mechanical strength tended to decrease as the concentration of AlN increased and needed to be optimized, the melting temperature (Tm) and glass transition temperature (Tg) showed a shift toward higher values as the AlN concentration increased leading to an improvement in thermal properties. AlN additions in weight percentages >10 wt. % led to appreciable antibacterial properties against S. epidermidis and E. coli bacteria. Antibacterial CA/AlN composites with higher thermal stability have potential applications as alternative materials for plastic packaging in the food industry.

Raman spectroscopy for early detection and monitoring of dentin demineralization.

Early detection of dental caries and variations in composition/structure of both enamel and dentin represents an important issue in modern dentistry. Demineralization has been associated to teeth discoloration, development of caries, and formation of cavities. OBJECTIVE: In this study, we systematically monitored the processes of demineralization/remineralization in dentin samples by means of three different spectroscopic techniques, namely, Raman spectroscopy, X-Ray Photo-electron spectroscopy (XPS), and X-Ray Diffractometry (XRD). METHODS: Bovine dentin samples were first exposed to acidic solutions and their structure systematically monitored as a function of time and pH. Then, the samples were rinsed in artificial saliva to simulate remineralization. RESULTS: The above three spectroscopic techniques provided quantitative structural information spanning from the nanometer to the millimeter scale of sample penetration depth. An irreversible level of demineralization was reached when dentin was exposed to pH 2 beyond a time threshold of 6h, successive treatments with artificial saliva being unable to restore the mineral fraction. On the other hand, short-term treatments at pH 5 and long-term treatments at pH 6 could partially or completely recover the dentin structure within one week of remineralization treatment. SIGNIFICANCE: Two specific Raman parameters, namely, the bandwidth of the symmetric phosphate-stretching signal and the mineral-to-matrix intensity ratio, showed strong correlations with XPS and XRD data, and matched laser microscopy observations. Such correlations open the path to apply Raman spectroscopy in monitoring dentin demineralization in vivo and provide quantitative working algorithms for the prevention of oral caries.