Structural evaluation of human and sheep bone and comparison with synthetic hydroxyapatite by FT-Raman spectroscopy

Physicochemical understanding of biomineralization by molecular vibrational spectroscopy: From mechanism to nature

The process and mechanism of biomineralization and relevant physicochemical properties of mineral crystals are remarkably sophisticated multidisciplinary fields that include biology, chemistry, physics, and materials science. The components of the organic matter, structural construction of minerals, and related mechanical interaction, etc., could help to reveal the unique nature of the special mineralization process. Herein, the paper provides an overview of the biomineralization process from the perspective of molecular vibrational spectroscopy, including the physicochemical properties of biomineralized tissues, from physiological to applied mineralization. These physicochemical characteristics closely to the hierarchical mineralization process include biological crystal defects, chemical bonding, atomic doping, structural changes, and content changes in organic matter, along with the interface between biocrystals and organic matter as well as the specific mechanical effects for hardness and toughness. Based on those observations, the special physiological properties of mineralization for enamel and bone, as well as the possible mechanism of pathological mineralization and calcification such as atherosclerosis, tumor micro mineralization, and urolithiasis are also reviewed and discussed. Indeed, the clearly defined physicochemical properties of mineral crystals could pave the way for studies on the mechanisms and applications.

Characterization of Distinct Chondrogenic Cell Populations of Patients Suffering from Microtia Using Single-Cell Micro-Raman Spectroscopy

Microtia is a congenital condition of abnormal development of the outer ear. Tissue engineering of the ear is an alternative treatment option for microtia patients. However, for this approach, the identification of high regenerative cartilage progenitor cells is of vital importance. Raman analysis provides a novel, non-invasive, label-free diagnostic tool to detect distinctive biochemical features of single cells or tissues. Using micro-Raman spectroscopy, we were able to distinguish and characterize the particular molecular fingerprints of differentiated chondrocytes and perichondrocytes and their respective progenitors isolated from healthy individuals and microtia patients. We found that microtia chondrocytes exhibited lower lipid concentrations in comparison to healthy cells, thus indicating the importance of fat storage. Moreover, we suggest that collagen is a useful biomarker for distinguishing between populations obtained from the cartilage and perichondrium because of the higher spectral contributions of collagen in the chondrocytes compared to perichondrocytes from healthy individuals and microtia patients. Our results represent a contribution to the identification of cell markers that may allow the selection of specific cell populations for cartilage tissue engineering. Moreover, the observed differences between microtia and healthy cells are essential for gaining better knowledge of the cause of microtia. It can be useful for designing novel treatment options based on further investigations of the discovered biochemical substrate alterations.

Exploration of utility of combined optical photothermal infrared and Raman imaging for investigating the chemical composition of microcalcifications in breast cancer

Microcalcifications play an important role in cancer detection. They are evaluated by their radiological and histological characteristics but it is challenging to find a link between their morphology, their composition and the nature of a specific type of breast lesion. Whilst there are some mammographic features that are either typically benign or typically malignant often the appearances are indeterminate. Here, we explore a large range of vibrational spectroscopic and multiphoton imaging techniques in order to gain more information about the composition of the microcalcifications. For the first time, we validated the presence of carbonate ions in the microcalcifications by O-PTIR and Raman spectroscopy at the same time, the same location and the same high resolution (0.5 μm). Furthermore, the use of multiphoton imaging allowed us to create stimulated Raman histology (SRH) images which mimic histological images with all chemical information. In conclusion, we established a protocol for efficiently analysing the microcalcifications by iteratively refining the area of interest.

Crystallographic Characteristics of Inorganic Mineral in Mammoth Ivory and Ivory

In this paper, the chemical composition and crystalline properties of mammoth ivory and ivory were systematically analyzed. The results revealed that the microscopic crystalline hydroxyapatites are the major component of minerals in mammoth ivory and ivory. The Ca/P ratios of the samples studied are obviously lower than apatite. Refined cell parameters showed a similar value between mammoth ivory (a = 9.4148 Å and b = 6.8821 Å) and ivory (a = 9.4166 Å and c = 6.8841 Å). Individual crystal sizes in mammoth ivory and ivory are estimated to be 20.41–23.16 and 18.92–21.50 nm, respectively. The calculated crystallinity of two kinds of ivory (mammoth ivory: 1.55; ivory: 1.4) is far lower than geological mineral fluorapatite due to the impact of tissue function and organic matrix.

The investigation of bone fracture healing under intramembranous and endochondral ossification

After trauma, fractured bone starts healing directly through bone union or indirectly through callus formation process. Intramembranous and endochondral ossification are two commonly known mechanisms of indirect healing. The present study investigated the bone fracture healing under intramembranous and endochondral ossification by developing theoretical models in conjunction with performing a series of animal experiments. Using experimentally determined mean bone densities in sheep tibia stabilized by the Locking Compression Plate (LCP) fixation system, the research outcomes showed that intramembranous and endochondral ossification can be described by Hill Function with two unique sets of function parameters in mechanical stimuli mediated fracture healing. Two different thresholds exist within the range of mechanical simulation index which could trigger significant intramembranous and endochondral ossification, with a relatively higher bone formation rate of endochondral ossification than that of intramembranous ossification. Furthermore, the increase of flexibility of the LCP system and the use of titanium LCP could potentially promote uniform bone formation across the fracture gap, ultimately better healing outcomes.

Temporal In Vitro Raman Spectroscopy for Monitoring Replication Kinetics of Epstein-Barr Virus Infection in Glial Cells

Raman spectroscopy can be used as a tool to study virus entry and pathogen-driven manipulation of the host efficiently. To date, Epstein-Barr virus (EBV) entry and altered biochemistry of the glial cell upon infection are elusive. In this study, we detected biomolecular changes in human glial cells, namely, HMC-3 (microglia) and U-87 MG (astrocytes), at two variable cellular locations (nucleus and periphery) by Raman spectroscopy post-EBV infection at different time points. Two possible phenomena, one attributed to the response of the cell to viral attachment and invasion and the other involved in duplication of the virus followed by egress from the host cell, are investigated. These changes corresponded to unique Raman spectra associated with specific biomolecules in the infected and the uninfected cells. The Raman signals from the nucleus and periphery of the cell also varied, indicating differential biochemistry and signaling processes involved in infection progression at these locations. Molecules such as cholesterol, glucose, hyaluronan, phenylalanine, phosphoinositide, etc. are associated with the alterations in the cellular biochemical homeostasis. These molecules are mainly responsible for cellular processes such as lipid transport, cell proliferation, differentiation, and apoptosis in the cells. Raman signatures of these molecules at distinct time points of infection indicated their periodic involvement, depending on the stage of virus infection. Therefore, it is possible to discern the details of variability in EBV infection progression in glial cells at the biomolecular level using time-dependent in vitro Raman scattering.

Role of artificial intelligence and vibrational spectroscopy in cancer diagnostics

INTRODUCTION

Raman and Infrared spectroscopic techniques are being used for the analysis of different types of cancers and other biological molecules. It is possible to identify cancers from normal tissues both in fresh and fixed tissues. These techniques can be used not only for the early diagnosis of cancer but also for monitoring the progression of the disease. Furthermore, chemical pathways to the progression of the disease process can be understood and followed.

AREAS COVERED

More recently, Artificial Intelligence (AI), Neural Network (NN), and Machine Learning are being combined with spectroscopy, which is making it easier to understand the chemical structural details of cancers and biological molecules more precisely and accurately. In this report, these aspects are being outlined by using breast cancer as a specific example.

EXPERT OPINION

A pathway showing to combine vibrational spectroscopy with AI and ML has immense potential in predicting various stages of different disease processes, in particular, in cancer diagnosis, staging, and designing treatment. This will result in improved patient care pathways.

Molecular analysis of the destruction of articular joint tissues by Raman spectroscopy

INTRODUCTION

Osteoarthritis (OA) is a highly heterogenous disease influenced by different molecular, anatomic, and physiologic imbalances. Some of the bottlenecks for enhanced diagnosis and therapeutic assessment are the lack of validated biomarkers and early diagnosis tools. In this narrative review, we analyze the potential of Raman spectroscopy (RS) as a label-free optical tool for the characterization of articular joint tissues and its application as a diagnosis tool for OA.

AREAS COVERED

Raman spectra produce a unique 'molecular fingerprint' providing rotational and vibrational molecular information, allowing the identification and follow-up of molecular changes associated with OA pathological mechanisms. Focusing on multiple joint tissues (cartilage, synovium, bone, tendons, ligaments, and meniscus) and their contribution in disease incidence and progression, this review highlights the current knowledge on the application of RS in the characterization of organic and inorganic molecules present at these tissues and alterations that occur in the onset of OA.

EXPERT OPINION

Vibrational spectroscopy techniques, such as RS, are low cost, rapid and minimally invasive approaches that offer high specificity in the assessment of the molecular composition of complex tissues. Combined with multivariate statistical methods, RS offers great potential for optical biomarkers discovery or disease diagnosis applications, and we hereby discuss clinical translational progresses on the field.

Effect of a novel quaternary ammonium silane cavity disinfectant on cariogenic biofilm formation

OBJECTIVE

Evaluate effect of quaternary ammonium silane (QAS) cavity disinfectant on cariogenic biofilm.

MATERIALS AND METHODS

Single- (Streptococcus mutans or Lactobacillus acidophilus), dual- (Streptococcus mutans/Lactobacillus Acidophilus), and multi-species (Streptococcus mutans, Actinomyces naeslundii, and Streptococcus sanguis) biofilms were grown on acid-etched dentine discs. Biofilms were incubated (120 min/37 °C) and allowed to grow for 3 days anaerobically. Discs (no treatment) served as control (group 1). Groups II, III, IV, and V were then treated with 2% chlorhexidine, and 2%, 5%, and 10% QAS (20 s). Discs were returned to well plates with 300 μL of bacterial suspension and placed in anaerobic incubator at 37 °C and biofilms redeveloped for 4 days. Confocal microscopy, Raman, CFU, and MTT assay were performed.

RESULTS

Raman peaks show shifts at 1450 cm^-1, 1453 cm^-1, 1457 cm^-1, 1460 cm^-1, and 1462 cm^-1 for control, 2% CHX, 2%, 5%, and 10% QAS groups in multi-species biofilms. There was reduction of 484 cm^-1 band in 10% QAS group. CLSM revealed densely clustered green colonies in control group and red confluent QAS-treated biofilms with significantly lower log CFU for single/dual species. Metabolic activities of Streptococcus mutans and Lactobacillus acidophilus decreased with increasing QAS exposure time.

CONCLUSION

Quaternary ammonium silanes possess antimicrobial activities and inhibit growth of cariogenic biofilms.

CLINICAL SIGNIFICANCE

Available data demonstrated use of QAS as potential antibacterial cavity disinfectant in adhesive dentistry. Experimental QAS can effectively eliminate caries-forming bacteria, when used inside a prepared cavity, and can definitely overcome problems associated with present available cavity disinfectants.

Fourier transform infrared spectroscopy based spectral biomarkers of metastasized breast cancer progression

Breast cancer is a global health issue and the second leading cause of cancer death in women. Breast cancer tends to migrate to bone and causes bone metastases which is ultimately the cause of death. Here, we report the use of FTIR to identify spectral biomarkers of cancer progression on 3D in vitro model of breast cancer bone metastasis. Our results indicate that the following spectral biomarkers can monitor cancer progression, for example, lipids (CH2 asymmetric/CH2 symmetric stretch), Amide I/Amide II, and RNA/DNA. Principal component analysis also confirmed the involvement of protein, lipids and nucleic acids in cancer progression on sequential culture. The collective observations from this study suggest successful application of FTIR as a non-invasive and accurate method to identify biochemical changes in cancer cells during the progression of breast cancer bone metastasis.

Isolation and characterization of canine perivascular stem/stromal cells for bone tissue engineering

For over 15 years, human subcutaneous adipose tissue has been recognized as a rich source of tissue resident mesenchymal stem/stromal cells (MSC). The isolation of perivascular progenitor cells from human adipose tissue by a cell sorting strategy was first published in 2008. Since this time, the interest in using pericytes and related perivascular stem/stromal cell (PSC) populations for tissue engineering has significantly increased. Here, we describe a set of experiments identifying, isolating and characterizing PSC from canine tissue (N = 12 canine adipose tissue samples). Results showed that the same antibodies used for human PSC identification and isolation are cross-reactive with canine tissue (CD45, CD146, CD34). Like their human correlate, canine PSC demonstrate characteristics of MSC including cell surface marker expression, colony forming unit-fibroblast (CFU-F) inclusion, and osteogenic differentiation potential. As well, canine PSC respond to osteoinductive signals in a similar fashion as do human PSC, such as the secreted differentiation factor NEL-Like Molecule-1 (NELL-1). Nevertheless, important differences exist between human and canine PSC, including differences in baseline osteogenic potential. In summary, canine PSC represent a multipotent mesenchymogenic cell source for future translational efforts in tissue engineering.

Feasibility of Spatially Offset Raman Spectroscopy for in Vitro and in Vivo Monitoring Mineralization of Bone Tissue Engineering Scaffolds

We investigated the feasibility of using spatially offset Raman spectroscopy (SORS) for nondestructive characterization of bone tissue engineering scaffolds. The deep regions of these scaffolds, or scaffolds implanted subcutaneously in live animals, are typically difficult to measure by confocal Raman spectroscopy techniques because of the limited depth penetration of light caused by the high level of light scattering. Layered samples consisting of bioactive glass foams (IEIC16), three-dimensional (3D)-printed biodegradable poly(lactic-co-glycolic acid) scaffolds (PLGA), and hydroxyapatite powder (HA) were used to mimic nondestructive detection of biomineralization for intact real-size 3D tissue engineering constructs. SORS spectra were measured with a new SORS instrument using a digital micromirror device (DMD) to allow software selection of the spatial offsets. The results show that HA can be reliably detected at depths of 0-2.3 mm, which corresponds to the maximum accessible spatial offset of the current instrument. The intensity ratio of Raman bands associated with the scaffolds and HA with the spatial offset depended on the depth at which HA was located. Furthermore, we show the feasibility for in vivo monitoring mineralization of scaffold implanted subcutaneously by demonstrating the ability to measure transcutaneously Raman signals of the scaffolds and HA (fresh chicken skin used as a top layer). The ability to measure spectral depth profiles at high speed (5 s acquisition time) and the ease of implementation make SORS a promising approach for noninvasive characterization of cell/tissue development in vitro, and for long-term in vivo monitoring the mineralization in 3D scaffolds subcutaneously implanted in small animals.

Synchrotron Imaging Assessment of Bone Quality

Bone is a complex hierarchical structure, and its principal function is to resist mechanical forces and fracture. Bone strength depends not only on the quantity of bone tissue but also on the shape and hierarchical structure. The hierarchical levels are interrelated, especially the micro-architecture, collagen and mineral components; hence, analysis of their specific roles in bone strength and stiffness is difficult. Synchrotron imaging technologies including micro-CT and small/wide angle X-ray scattering/diffraction are becoming increasingly popular for studying bone because the images can resolve deformations in the micro-architecture and collagen-mineral matrix under in situ mechanical loading. Synchrotron cannot be directly applied in vivo due to the high radiation dose but will allow researchers to carry out systematic multifaceted studies of bone ex vivo. Identifying characteristics of aging and disease will underpin future efforts to generate novel devices and interventional therapies for assessing and promoting healthy aging. With our own research work as examples, this paper introduces how synchrotron imaging technology can be used with in situ testing in bone research.

The Orientation of Nanoscale Apatite Platelets in Relation to Osteoblastic-Osteocyte Lacunae on Trabecular Bone Surface

The orientation of nanoscale mineral platelets was quantitatively evaluated in relation to the shape of lacunae associated with partially embedded osteocytes (osteoblastic-osteocytes) on the surface of deproteinised trabecular bone of adult sheep. By scanning electron microscopy and image analysis, the mean orientation of mineral platelets at the osteoblastic-osteocyte lacuna (Ot.Lc) floor was found to be 19° ± 14° in the tibia and 20° ± 14° in the femur. Further, the mineral platelets showed a high degree of directional coherency: 37 ± 7% in the tibia and 38 ± 9% in the femur. The majority of Ot.Lc in the tibia (69.37%) and the femur (74.77%) exhibited a mean orientation of mineral platelets between 0° and 25°, with the largest fraction within a 15°-20° range, 17.12 and 19.8% in the tibia and femur, respectively. Energy dispersive X-ray spectroscopy and Raman spectroscopy were used to characterise the features observed on the anorganic bone surface. The Ca/P (atomic %) ratio was 1.69 ± 0.1 within the Ot.Lc and 1.68 ± 0.1 externally. Raman spectra of NaOCl-treated bone showed peaks associated with carbonated apatite: ν1, ν2 and ν4 PO4(3-), and ν1 CO3(2-), while the collagen amide bands were greatly reduced in intensity compared to untreated bone. The apatite-to-collagen ratio increased considerably after deproteinisation; however, the mineral crystallinity and the carbonate-to-phosphate ratios were unaffected. The ~19°-20° orientation of mineral platelets in at the Ot.Lc floor may be attributable to a gradual rotation of osteoblasts in successive layers relative to the underlying surface, giving rise to the twisted plywood-like pattern of lamellar bone.

The effect of alendronate on biomineralization at the bone/implant interface

A recent approach to improve the osseointegration of implants is to utilize local drug administration. The presence of an osteoporosis drug may influence both bone quantity and quality at the bone/implant interface. Despite this, the performance of bone-anchoring implants is traditionally evaluated only by quantitative measurements. In the present study, the osteoporosis drug alendronate (ALN) was administrated from mesoporous titania thin films that were coated onto titanium implants. The effect that the drug had on biomineralization was explored both in vitro using simulated body fluid (SBF) and in vivo in a rat tibia model. The SBF study showed that the apatite formation was completely hindered at a high concentration of ALN (0.1 mg/mL). However, when ALN was administrated from the mesoporous coating the surface became completely covered with apatite. Ex vivo characterization of the bone/implant interface using Raman spectroscopy demonstrated that the presence of ALN enhanced the bone mineralization, and that the chemical signature of newly formed bone in the presence of ALN had a higher resemblance to the pre-existing mature bone than to the bone formed without drug. Taken together, this study demonstrates the importance of evaluating the quality of the formed bone to better understand the performance of implants. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part A 104A: 620-629, 2016.

Raman spectroscopy for medical diagnostics--From in-vitro biofluid assays to in-vivo cancer detection

Raman spectroscopy is an optical technique based on inelastic scattering of light by vibrating molecules and can provide chemical fingerprints of cells, tissues or biofluids. The high chemical specificity, minimal or lack of sample preparation and the ability to use advanced optical technologies in the visible or near-infrared spectral range (lasers, microscopes, fibre-optics) have recently led to an increase in medical diagnostic applications of Raman spectroscopy. The key hypothesis underpinning this field is that molecular changes in cells, tissues or biofluids, that are either the cause or the effect of diseases, can be detected and quantified by Raman spectroscopy. Furthermore, multivariate calibration and classification models based on Raman spectra can be developed on large "training" datasets and used subsequently on samples from new patients to obtain quantitative and objective diagnosis. Historically, spontaneous Raman spectroscopy has been known as a low signal technique requiring relatively long acquisition times. Nevertheless, new strategies have been developed recently to overcome these issues: non-linear optical effects and metallic nanoparticles can be used to enhance the Raman signals, optimised fibre-optic Raman probes can be used for real-time in-vivo single-point measurements, while multimodal integration with other optical techniques can guide the Raman measurements to increase the acquisition speed and spatial accuracy of diagnosis. These recent efforts have advanced Raman spectroscopy to the point where the diagnostic accuracy and speed are compatible with clinical use. This paper reviews the main Raman spectroscopy techniques used in medical diagnostics and provides an overview of various applications.

In vitro analysis of riboflavin-modified, experimental, two-step etch-and-rinse dentin adhesive: Fourier transform infrared spectroscopy and micro-Raman studies

To modify two-step experimental etch-and-rinse dentin adhesive with different concentrations of riboflavin and to study its effect on the bond strength, degree of conversion, along with resin infiltration within the demineralized dentin substrate, an experimental adhesive-system was modified with different concentrations of riboflavin (m/m, 0, 1%, 3%, 5% and 10%). Dentin surfaces were etched with 37% phosphoric acid, bonded with respective adhesives, restored with restorative composite–resin, and sectioned into resin–dentin slabs and beams to be stored for 24 h or 9 months in artificial saliva. Micro-tensile bond testing was performed with scanning electron microscopy to analyse the failure of debonded beams. The degree of conversion was evaluated with Fourier transform infrared spectroscopy (FTIR) at different time points along with micro-Raman spectroscopy analysis. Data was analyzed with one-way and two-way analysis of variance followed by Tukey's for pair-wise comparison. Modification with 1% and 3% riboflavin increased the micro-tensile bond strength compared to the control at 24 h and 9-month storage with no significant differences in degree of conversion (P<0.05). The most predominant failure mode was the mixed fracture among all specimens except 10% riboflavin-modified adhesive specimens where cohesive failure was predominant. Raman analysis revealed that 1% and 3% riboflavin adhesives specimens showed relatively higher resin infiltration. The incorporation of riboflavin in the experimental two-step etch-and-rinse adhesive at 3% (m/m) improved the immediate bond strengths and bond durability after 9-month storage in artificial saliva without adversely affecting the degree of conversion of the adhesive monomers and resin infiltration.

NELL-1 in the treatment of osteoporotic bone loss

NELL-1 is a secreted, osteoinductive protein whose expression rheostatically controls skeletal ossification. Overexpression of NELL-1 results in craniosynostosis in humans and mice, whereas lack of Nell-1 expression is associated with skeletal undermineralization. Here we show that Nell-1-haploinsufficient mice have normal skeletal development but undergo age-related osteoporosis, characterized by a reduction in osteoblast:osteoclast (OB:OC) ratio and increased bone fragility. Recombinant NELL-1 binds to integrin β1 and consequently induces Wnt/β-catenin signalling, associated with increased OB differentiation and inhibition of OC-directed bone resorption. Systemic delivery of NELL-1 to mice with gonadectomy-induced osteoporosis results in improved bone mineral density. When extended to a large animal model, local delivery of NELL-1 to osteoporotic sheep spine leads to significant increase in bone formation. Altogether, these findings suggest that NELL-1 deficiency plays a role in osteoporosis and demonstrate the potential utility of NELL-1 as a combination anabolic/antiosteoclastic therapeutic for bone loss.

Raman spectroscopic sensing of carbonate intercalation in breast microcalcifications at stereotactic biopsy

Microcalcifications are an early mammographic sign of breast cancer and frequent target for stereotactic biopsy. Despite their indisputable value, microcalcifications, particularly of the type II variety that are comprised of calcium hydroxyapatite deposits, remain one of the least understood disease markers. Here we employed Raman spectroscopy to elucidate the relationship between pathogenicity of breast lesions in fresh biopsy cores and composition of type II microcalcifications. Using a chemometric model of chemical-morphological constituents, acquired Raman spectra were translated to characterize chemical makeup of the lesions. We find that increase in carbonate intercalation in the hydroxyapatite lattice can be reliably employed to differentiate benign from malignant lesions, with algorithms based only on carbonate and cytoplasmic protein content exhibiting excellent negative predictive value (93–98%). Our findings highlight the importance of calcium carbonate, an underrated constituent of microcalcifications, as a spectroscopic marker in breast pathology evaluation and pave the way for improved biopsy guidance.

Raman Thermometry Based Thermal Conductivity Measurement of Bovine Cortical Bone as a Function of Compressive Stress

Biological materials such as bone have microstructure that incorporates a presence of a significant number of interfaces in a hierarchical manner that lead to a unique combination of properties such as toughness and hardness. However, studies regarding the influence of structural hierarchy in such materials on their physical properties such as thermal conductivity and its correlation with mechanical stress are limited. Such studies can point out important insights regarding the role of biological structural hierarchy in influencing multiphysical properties of materials. This work presents an analytic-experimental approach to establish stress–thermal conductivity correlation in bovine cortical bone as a function of nanomechanical compressive stress changes using Raman thermometry. Analyzes establish empirical relations between Raman shift and temperature as well as a relation between Raman shift and nanomechanical compressive stress. Analyzes verify earlier reported thermal conductivity results at 0% strain and at room temperature in the case of bovine cortical bone. In addition, measured trends and established thermal conductivity–stress relation indicates that the thermal conductivity values increase up to a threshold compressive stress value. On increasing stress beyond the threshold value, the thermal conductivity decreases as a function of increase in compressive strain. Interface reorganization versus interface related phonon wave blocking are the two competing mechanisms highlighted to affect such trend.

Long-term resilience of late holocene coastal subsistence system in Southeastern South america

Isotopic and molecular analysis on human, fauna and pottery remains can provide valuable new insights into the diets and subsistence practices of prehistoric populations. These are crucial to elucidate the resilience of social-ecological systems to cultural and environmental change. Bulk collagen carbon and nitrogen isotopic analysis of 82 human individuals from mid to late Holocene Brazilian archaeological sites (∼6,700 to ∼1,000 cal BP) reveal an adequate protein incorporation and, on the coast, the continuation in subsistence strategies based on the exploitation of aquatic resources despite the introduction of pottery and domesticated plant foods. These results are supported by carbon isotope analysis of single amino acid extracted from bone collagen. Chemical and isotopic analysis also shows that pottery technology was used to process marine foods and therefore assimilated into the existing subsistence strategy. Our multidisciplinary results demonstrate the resilient character of the coastal economy to cultural change during the late Holocene in southern Brazil.

In vitro evaluation of enamel demineralization after several overlapping CO2 laser applications

This study aimed to evaluate the effects of repeated CO2 laser applications on the inhibition of enamel demineralization. Sixty-five human dental enamel slabs were randomly assigned to the following groups (n = 13): control (C), one application of the CO2 laser (L1), two applications of the CO2 laser (L2), three applications of the CO2 laser (L3), and four applications of the CO2 laser (L4). Enamel slabs were irradiated by a 10.6-μm CO2 laser operating at 5 J/cm(2). The slabs were subjected to a pH-cycling regimen and then analyzed by FT-Raman spectroscopy, energy-dispersive X-ray fluorescence spectrometry (EDXRF), cross-sectional micro-hardness, and scanning electron microscopy (SEM). Statistical analysis was performed using ANOVA and Tukey tests (p < 0.05). FT-Raman spectroscopy showed a reduced carbonate content for L1, L3, and L4 groups when compared to C (p < 0.05). The EDXRF data showed no statistical differences between the control and irradiated groups for calcium and phosphorus components (p > 0.05). Cross-sectional micro-hardness data showed a statistically significant difference between the control and all irradiated groups (p < 0.05), but no difference was found among the irradiated groups (p > 0.05) up to 30-μm depth. A tendency of lower demineralization occurred in deeper depths for L3 and L4 groups. The SEM results showed that with repeated applications of the CO2 laser, a progressive melting and recrystallization of the enamel surface occurred. Repeated irradiations of dental enamel may enhance the inhibition of enamel demineralization.

Can mesenchymal stem cells and novel gabapentin-lactam enhance maxillary bone formation?

PURPOSE

Novel gabapentin-lactam (GBP-L) has shown its potency in enhancing new bone formation (NBF) in vitro. The objective of the present preclinical trial was to investigate the in vivo performance of GBP-L.

MATERIALS AND METHODS

Bilateral sinus floor augmentations in 10 adult sheep were conducted. Bovine bone mineral (BBM) and mesenchymal stem cells (MSCs) combined with novel GBP-L were placed into the test sinus of each sheep. The BBM and MSCs alone served as the control on the contralateral side. Simultaneously, 3 dental implants were inserted in each maxillary sinus. The animals were sacrificed after 8 and 16 weeks, and the amount of NBF was analyzed using histomorphometry. The osteogenic potency of the MSCs was demonstrated using the colony-forming unit and differentiation assay. Statistical evaluation was performed using the Wilcoxon signed rank test and 3-factorial nonparametric analysis of variance.

RESULTS

The histologic examination showed NBF in tight contact with the original bone in the control and test groups. The NBF was not significantly different between the test and control sites (P > .05). However, a highly significant difference in NBF between the apical and coronal sites in the specimens from the control and test groups was detected (P < .05). GBP-L did not alter the multipotency of the MSCs or impair NBF.

CONCLUSIONS

Bone formation is initiated from the residual alveolar crest and along the implant. The elected mode of GBP-L application did not induce faster NBF. Alternate forms of application (eg, slow release or systemic administration) might clarify the controversial in vitro findings.

Infrared spectroscopic characterization of carbonated apatite: a combined experimental and computational study

A combined experimental and computational approach was employed to investigate the feasibility and effectiveness of characterizing carbonated apatite (CAp) by infrared (IR) spectroscopy. First, an experimental comparative study was conducted to identify characteristic IR vibrational bands of carbonate substitution in the apatite lattice. The IR spectra of pure hydroxyapatite (HA), carbonate adsorbed on the HA surface, a physical mixture of HA and sodium carbonate monohydrate, a physical mixture of HA and calcite, synthetic CAps prepared using three methods (precipitation method, hydrothermal route, and solid-gas reaction at high temperature) and biological apatites (human enamel, human cortical bone, and two animal bones) were compared. Then, the IR vibrational bands of carbonate in CAp were calculated with density functional theory. The experimental study identified characteristic IR bands of carbonate that cannot be generated from surface adsorption or physical mixtures and the results show that the bands at ∼880, 1413, and 1450 cm(-1) should not be used as characteristic bands of CAp since they could result from carbonate adsorbed on the apatite crystals surface or present as a separate phase. The combined experimental and computational study reveals that the carbonate v3 bands at ∼1546 and 1465 cm(-1) are, respectively, the IR signature bands for type A CAp and type B CAp.

Analysis of ovarian tumor pathology by Fourier Transform Infrared Spectroscopy

Background

Ovarian cancer is the second most common cancer among women and the leading cause of death among gynecologic malignancies. In recent years, infrared (IR) spectroscopy has gained attention as a simple and inexpensive method for the biomedical study of several diseases. In the present study infrared spectra of normal and malignant ovarian tissues were recorded in the 650 cm^-1 to 4000 cm^-1 region.

Methods

Post surgical tissue samples were taken from the normal and tumor sections of the tissue. Fourier Transform Infrared (FTIR) data on twelve cases of ovarian cancer with different grades of malignancy from patients of different age groups were analyzed.

Results

Significant spectral differences between the normal and the ovarian cancerous tissues were observed. In particular changes in frequency and intensity in the spectral region of protein, nucleic acid and lipid vibrational modes were observed. It was evident that the sample-to-sample or patient-to-patient variations were small and the spectral differences between normal and diseased tissues were reproducible.

Conclusion

The measured spectroscopic features, which are the spectroscopic fingerprints of the tissues, provided the important differentiating information about the malignant and normal tissues. The findings of this study demonstrate the possible use of infrared spectroscopy in differentiating normal and malignant ovarian tissues.

Miniplate osteosynthesis with four different systems in sheep

The aim of this study was to compare a combination of a locking system with self-tapping (ST-L) or self-drilling-tapping (SDT-L) screws with a combination of conventional miniplates with self-tapping (ST) and self-forming (SF) screws. A standardized osteotomy and osteosynthesis with one of the above mentioned systems was performed in 24 sheep. Callus formation was measured with the help of CT scans assisted by a navigation system. Specimens of each osteotomy gap were taken and examined histologically. The best results were observed when self-tapping screws and the Mini-Locking-System (ST-L) were applied. The slowest healing was seen in animals treated with miniplates and SF screws. After 8 weeks an increase in bone formation could be observed in the ST, SF, SDT-L systems. The results after 8 weeks were comparable with those achieved by the ST-L system after 4 weeks. The improved stability of the osteosynthesis with the ST-L system resulted in early ossification of the osteotomy gap and the smallest amount of callus formation.

Raman and mechanical properties correlate at whole bone- and tissue-levels in a genetic mouse model

The fracture resistance of bone arises from the composition, orientation, and distribution of the primary constituents at each hierarchical level of organization. Therefore, to establish the relevance of Raman spectroscopy (RS) in identifying differences between strong or tough bone and weak or brittle bone, we investigated whether Raman-derived properties could explain the variance in biomechanical properties at both the whole bone and the tissue-level, and do so independently of traditional measurements of mineralization. We harvested femurs from wild-type mice and mice lacking matrix metalloproteinase 2 because the mutant mice have a known reduction in mineralization. Next, RS quantified compositional properties directly from the intact diaphysis followed by micro-computed tomography to quantify mineralization density (Ct.TMD). Correlations were then tested for significance between these properties and the biomechanical properties as determined by the three-point bending test on the same femurs. Harvested tibia were embedded in plastic, sectioned transversely, and polished in order to acquire average Raman properties per specimen that were then correlated with average nanoindentation properties per specimen. Dividing the ν(1) phosphate by the proline peak intensity provided the strongest correlation between the mineral-to-collagen ratio and the biomechanical properties (whole bone modulus, strength, and post-yield deflection plus nanoindentation modulus). Moreover, the linear combination of ν(1) phosphate/proline and Ct.TMD provided the best explanation of the variance in strength between the genotypes, and it alone was the best explanatory variable for brittleness. Causal relationships between Raman and fracture resistance need to be investigated, but Raman has the potential to assess fracture risk.

Bone repair by cell-seeded 3D-bioplotted composite scaffolds made of collagen treated tricalciumphosphate or tricalciumphosphate-chitosan-collagen hydrogel or PLGA in ovine critical-sized calvarial defects

The aim of this study was to investigate the osteogenic effect of three different cell-seeded 3D-bioplotted scaffolds in a ovine calvarial critical-size defect model. The choice of scaffold-materials was based on their applicability for 3D-bioplotting and respective possibility to produce tailor-made scaffolds for the use in cranio-facial surgery for the replacement of complex shaped boneparts. Scaffold raw-materials are known to be osteoinductive when being cell-seeded [poly(L-lactide-co-glycolide) (PLGA)] or having components with osteoinductive properties as tricalciumphosphate (TCP) or collagen (Col) or chitosan. The scaffold-materials PLGA, TCP/Col, and HYDR (TCP/Col/chitosan) were cell-seeded with osteoblast-like cells whether gained from bone (OLB) or from periost (OLP). In a prospective and randomized design nine sheep underwent osteotomy to create four critical-sized calvarial defects. Three animals each were assigned to the HYDR-, the TCP/Col-, or the PLGA-group. In each animal, one defect was treated with a cell-free, an OLB- or OLP-seeded group-specific scaffold, respectively. The fourth defect remained untreated as control (UD). Fourteen weeks later, animals were euthanized for histo-morphometrical analysis of the defect healing. OLB- and OLP-seeded HYDR and OLB-seeded TCP/Col scaffolds significantly increased the amount of newly formed bone (NFB) at the defect bottom and OLP-seeded HYDR also within the scaffold area, whereas PLGA-scaffolds showed lower rates. The relative density of NFB was markedly higher in the HYDR/OLB group compared to the corresponding PLGA group. TCP/Col had good stiffness to prepare complex structures by bioplotting but HYDR and PLGA were very soft. HYDR showed appropriate biodegradation, TCP/Col and PLGA seemed to be nearly undegraded after 14 weeks. 3D-bioplotted, cell-seeded HYDR and TCP/Col scaffolds increased the amount of NFB within ovine critical-size calvarial defects, but stiffness, respectively, biodegradation of materials is not appropriate for the application in cranio-facial surgery and have to be improved further by modifications of the manufacturing process or their material composition.

Carbonate assignment and calibration in the Raman spectrum of apatite

A series of apatites with varying carbonate levels was prepared in order to assign the carbonate bands and calibrate for Raman analysis of natural materials. Overlap of carbonate bands with phosphate peaks was resolved by curve fitting. A peak at 1,071 cm(-1) was assigned to a combination of the carbonate nu(1) mode at 1,070 cm(-1) with a phosphate nu(3) mode at 1,076 cm(-1). In addition, the carbonate nu(4) mode was identified in apatite samples with >4% carbonate. The carbonate nu(4) bands at 715 and 689 cm(-1) identify the samples as B-type carbonated apatite. The carbonate content of apatite was calibrated to a carbonate Raman band, and the method was used to determine the carbonate content of a sample of bovine cortical bone, 7.7 +/- 0.4%.

Synthesis and characterization of grafted nanohydroxyapatites using functionalized surface agents

Synthetic hydroxyapatite, HA [Ca10(PO4)6(OH)2], is a bioactive material that is chemically similar to biological apatite, the mineral phase of bone (a nanocomposite material). Synthetic biocomposites, comprising a polymer and hydroxyapatite that are used for bone replacement, have limitations when loaded under fatigue in that the weak mechanical bond between the two phases can result in failure at the interface. Chemical coupling of the HA and polymer matrix may provide a means of improving the interfacial bonding between the polymer and HA phases. Herein, we report our first steps toward developing chemically coupled nano-biocomposites via a two-step process. We describe the synthesis and characterization of surface-grafted hydroxyapatite (SG-HA), which possesses a reactive C=C functional group. In future work, we will report on the second step, namely the coupling of this functional group to a polymer by a copolymerization reaction to give a chemically coupled nano-biocomposite. The SG-HA reported herein was characterized by a range of methods including 31P and 13C magic-angle spinning (MAS)-NMR, Fourier transform infrared (FTIR), and Raman spectroscopy.

Laser induced fluorescence bands in the FT-Raman spectra of bioceramics

A new fluorescence band at about 1930cm-1 has been observed in the FT-Raman spectra of some bioceramics. While a fluorescence band at about 760cm-1 has been already reported in the FT-Raman spectra of hydroxyapatite and related calcium phosphates, this new band is observed for the first time. This strong band is totally absent in the anti-Stokes side of the FT-Raman spectra and therefore has been assigned as a laser induced fluorescence band. It has been concluded that in recording FT-Raman spectra of minerals, all precautions about fluorescence bands should be considered, otherwise the FT-Raman spectra may well be misinterpreted.

Parallel high-resolution confocal Raman SEM analysis of inorganic and organic bone matrix constituents

In many multi-disciplinary fields of science, such as tissue engineering, where material and biological sciences are combined, there is a need for a tool that combines ultrastructural and chemical data analysis in a non-destructive manner at high resolution. We show that a combination of confocal Raman spectroscopy (CRS) and scanning electron microscopy (SEM) can be used for such analysis. Studies of atomic composition can be done by X-ray microanalysis in SEM, but this is only possible for atomic numbers greater than five and does not reveal molecular identity. Raman spectroscopy, however, can provide information on molecular composition and identity by detection of wavelength shifts caused by molecular vibrations. In this study, CRS-SEM revealed that early in vitro-formed bone extracellular matrix (ECM) produced by rat osteoprogenitor cells resembles mature bone chemically. We gained insight into the structure and chemical composition of the ECM, which was composed of mainly mineralized collagen type I fibres and areas of dense carbonated calcium phosphate related to the collagen fibre density, as revealed by Raman imaging of SEM samples. We found that CRS-SEM allows the study of specimens in a non-destructive manner and provides high-resolution structural and chemical information about inorganic and organic constituents by parallel measurements on the same sample.

Chemical, Morphological and Thermal Effects of 10.6-.MU.m CO2 Laser on the Inhibition of Enamel Demineralization

Studies have shown that enamel can be modified by pulsed CO2 laser to form a more acid-resistant substrate. This study evaluated the effects of a 10.6-microm CO2 laser on enamel surface morphology and chemical composition as well as monitored intrapulpal temperature changes during irradiation. Human teeth were irradiated with fluences of 1.5-11.5 J/cm2, and pulpal thermal as well as chemical and morphological modifications on enamel were assessed. The teeth were submitted to a pH-cycling model, and the mineral loss was determined by means of cross-sectional microhardness. For all irradiated groups, intrapulpal temperature changes were below 3 degrees C. FT-Raman spectroscopy and scanning electron microscopy indicated that fluences as low as 6.0 J/cm2 were sufficient to induce chemical and morphological changes in enamel. Then, for fluences reaching or exceeding 10.0 J/cm2, laser-induced inhibitory effects on demineralization were observed. It was thus concluded that laser energy density in the range of 10.0 and 11.5 J/cm2 could be applied to dental enamel in order to produce chemical and morphological changes and reduce the acid reactivity of enamel without compromising the pulp vitality.

Microstructural analysis of implant-bone interface of hydroxyapatite-coated and uncoated Schanz screws

The aim of the study was to compare the pin-bone interface microstructural characteristics of hydroxyapatite-coated (HAC) and stainless steel Schanz screws after 2, 4 and 6 months of implantation in a sheep model. The microstructure and composition of the hydroxyapatite coating were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. Twelve coated and 12 uncoated screws were implanted into both femora of three sheep, each sheep receiving eight screws. Specimens of polished bone with screws were examined with SEM and light microscope for morphometric analyses. The HAC was approx. 40 microm thick, the grain size ranged from 5 to 40 microm, with pores less than 20 microm. The atomic ratio of Ca/P was 1.62. SEM showed that the bone-implant contact was better with HAC than with uncoated implants. The ingrowth of the bone in the HAC was clearly seen. Morphometric analysis showed good bone-implant contact in 65.1 (+/-24.6)% in the HAC and 32.0 (+/-23.3)% in the uncoated group (p<0.001). Although the percentage of good contact increased with time for both groups, it was significantly higher for HAC screws. Our investigation demonstrated a time dependent improvement of implant-bone contact of the HAC compared to standard stainless steel implants in the chosen experimental conditions.

Effect of pH and ionic strength on the reactivity of Bioglass® 45S5

Bioglass 45S5 is a silica-based melt-derived glass, used in medical field as a bone regenerative material because of the deposition of a layer of hydroxy carbonate apatite (HCA) on the surface of the glass when immersed in body fluid. The present paper studies the early steps of reaction of 2-microm sized particles of Bioglass, in solutions buffered with TRIS at different pH, by means of ICP-ES and FTIR spectroscopy. Only at pH 8 could a total reconstruction of the glass be observed, with the formation of both a silica and a calcium phosphate rich layers. At higher pH, selective dissolution of the glass was hindered by the immediate precipitation of a layer of calcium phosphate, whereas at lower pH a total breakdown of the glass occurred and no calcium phosphate precipitation was noted. The use of the ATR-liquid cell allowed the observation of the reaction in real time, and this showed that the process of silica formation is not separable from cation leaching from the glass, as well as the formation of the calcium phosphate rich layer.

FT-Raman spectroscopy of calcium hydroxide medicament in root canals

AIM

To investigate chemical changes in calcium hydroxide introduced into human root canals as a medicament using Fourier transform-(FT) Raman spectroscopy.

METHODOLOGY

Ten necrotic maxillary anterior teeth were selected in 10 patients. The teeth were divided into five treatment groups, according to the survey time. Root canal instrumentation was performed with hand instruments until the master apical file was size 40. Calcium hydroxide paste, in a 1 : 1.25 mixture by weight of powder and distilled water, was introduced directly into the root canal with a lentulo-spiral filler and then condensed with a finger plugger. The access cavity was sealed with a temporary dressing. After 2 and 4 days, then 2, 4 and 6 weeks, the calcium hydroxide paste was sampled with a K-file and then analysed using FT-Raman spectroscopy. The excitation source was an Nd : YAG laser with an excitation wavelength of 1064 nm. All spectra were taken with a laser power of 200 mW, 275-1185 scans, and 4 cm(-1) resolution. The conversion of calcium hydroxide to calcium carbonate was calculated on the basis of the spectral data obtained from the mixtures of both compounds.

RESULTS

The calcium hydroxide paste in the apical region showed weak bands at 1088 and 284 cm(-1), in addition to bands associated with calcium hydroxide. The weak bands, assigned to calcium carbonate, became stronger with time. Calcium carbonate content increased rapidly in the first 2 days and then tended to increase slowly. Approximately 11% of the calcium hydroxide at the apical portion of the canal was converted to calcium carbonate after 6 weeks. However, little alteration of the paste was noticed in the samples from the middle portion of the canal.

CONCLUSIONS

Calcium hydroxide medicament in root canals became transformed into calcium carbonate in the apical region within 2 days. Although the transformation continued with time, approximately 90% of the calcium hydroxide remained unchanged after 6 weeks.

Modal Damping for Monitoring Bone Integrity and Osteoporosis

We applied a noninvasive method to assess bone structural integrity. The method is based on the measurement of the dynamic characteristics of the bone (quality factor and modal damping factor) by applying vibration excitation in the range of acoustic frequencies, in the form of an acoustic sweep signal. Excised sheep femora were tested to detect changes in modal damping, density (kg/m3), bone mineral density (kg/m2) and bone mineral (hydroxyapatite) percentage. The changes were recorded after each time of chemical treatment of the bones performed to gradually cause mineral removal, thus simulating osteoporosis. It was shown that the change in quality factor and damping was in all cases on average equal or greater to the change in all other measured characteristics, thus strengthening the potential of the proposed method to become a valuable assessment tool for monitoring bone integrity and osteoporosis.

Integration of metallic endoprotheses in dog femur studied by near-infrared Fourier-transform Raman microscopy

The integration of hydroxyapatite-coated implants in dog femur was studied by near-infrared Fourier-transform Raman microscopy. Raman spectra were taken in lateral scans in step widths of 10-40 microm from the implant surface up to a distance of 320 microm into the bone tissue. The spectra were subjected to a component analysis for the quantitative determination of the protein and the inorganic components. This quantitative analysis is shown to be more reliable than conventional band fitting procedures and allows, for the first time, the quantitative distinction between the hydroxyapatite form of mature bone tissue and synthetic hydroxyapatite introduced by the implant coating. It is demonstrated that full mineralization of the ongrowing bone is not achieved after 6 months. In contrast, after a residence time of 18 months in the body, the Raman spectra reveal a complete calcification of the new bone tissue as indicated by content of biological hydroxyapatite that is the same as in mature bone tissue throughout the whole implant/bone interface. On the other hand, the content of synthetic hydroxyapatite is strongly reduced in the sample prepared after eighteen months implantation whereas for the shorter implantation time. substantial contributions of synthetic hydroxyapatite are found even at positions beyond the thickness of the implant coating. These results indicate that the coating material is actively involved in the mineralization of ongrowing bone. Possible mechanisms for the underlying transport processes in the implant/bone interface are discussed.

The effect of irrigation on peak temperatures in nerve root, dura, and intervertebral disc during laser-assisted foraminoplasty

BACKGROUND AND OBJECTIVE

The Holmium: YAG (Ho: YAG) laser has been used for the ablation of prolapsed discs but alternative techniques are available, and this application remains controversial. It also has potential for the decompression of nerve roots within narrowed foraminae with the technique of endoscopic laser foraminoplasty. Traditional methods of decompression necessitate a major surgical procedure with potential destabilisation of the lumbar spinal segment. Nevertheless, minimally invasive techniques are attractive only if serious complications can be avoided. This study reports the peak temperatures reached in surrounding tissues with and without saline irrigation.

STUDY DESIGN/MATERIALS AND METHODS

Investigation of the hypothesis was carried out in excised sheep lumbar spines. T-type thermocouples were used for the measurement of tissue temperatures during laser ablation of nerve root foraminae. The temperature was assessed in the nerve root, dura mater, and disc space.

RESULTS

The Ho: YAG laser was effective in widening the foraminae by approximately 1.5 mm with a total energy of 4.60 kJ. This was statistically significant in both vertical and horizontal directions (P < 0.0003 and P < 0.00005, respectively). The mean temperature of the nerve root, dura, and disc space during the procedure was 44 +/- 3.1 degrees C, 42.8 +/- 4.7 degrees C, and 41 +/- 3.4 degrees C respectively. There were transient high peaks seen in the temperature profiles. Using saline irrigation at 27 ml/minutes these temperatures were reduced to 34.1 +/- 1.8 degrees C (P = 0.0002), 34.9 +/- 1.5 degrees C (P = 0.002), and 37.2 +/- 1.2 degrees C (P < 0.014), for nerve roots, dura, and disc space respectively.

CONCLUSIONS

Laser ablation of bone and ligament for nerve root decompression using the Ho: YAG laser may offer substantial advantages, but the risk of serious complication may only be avoided if the technique is combined with saline irrigation.

Vibrational study and fluorescence bands in the FT-Raman spectra of Ca(10-x)Pb(x)(PO4)6(OH)2 compounds

About 40 apatitic compounds, stoichiometric or not, with different substitutions like lead, sodium and cadmium were investigated using infrared, Raman and FT-Raman spectroscopies. In the Ca(10-x)Pb(x)(PO4)6(OH)2 sequence (x runs from 0 to 10), the evolution of the fluorescence bands observed by FT-Raman, only with stoichiometric entities apatites, is mainly regarded and explained. Important spectral changes concerning the OH- and the PO4(3-) entities occur when 4 < or = x < or = 7. The intensity ratio of the two components of the v1 PO4(3-) mode is shown to be a suitable method to determine the lead content. The weak OH...O hydrogen bonds involving the OH- ions, of which the disorder is discussed, are different for the lead and calcium hydroxyapatites. The evolution of the fluorescence bands, as well as the splitting of the v(OH) mode, are due to the lead distribution in the two sites, with a preference for sites II, of the hydroxyapatite structure. The effect of temperature is also reported.

Application of vibrational spectroscopy to the study of mineralized tissues (review)

The infrared and Raman spectroscopy of bone and teeth tissues are reviewed. Characteristic spectra are obtained for both the mineral and protein components of these tissues. Vibrational spectroscopy is used to study the mineralization process, to define the chemical structure changes accompanying bone diseases, and to characterize interactions between prosthetic implants and tissues. Microspectroscopy allows acquisition of spatially resolved spectra, with micron scale resolution. Recently developed imaging modalities allow tissue imaging with chemical composition contrast.

Analysis of apatite layers on glass-ceramic particulate using FTIR and FT-Raman spectroscopy

A nucleation and crystallization schedule was adapted to produce 40% crystalline Bioglass ceramic particulates. These particles were placed in a dynamic environment in a simulated physiologic solution (SBF-9) for time periods ranging from 10 min to 7 days. Fourier transform Raman spectroscopy (FT-Raman) and infrared spectroscopy (FTIR) were used to analyze the apatite layer formation on the particulates. FTIR determined that amorphous apatite formation took place within 2 h, with the appearance of crystalline apatite in 14 h. The vibrational frequencies obtained through FT-Raman were equivalent to those obtained using FTIR. These analyses showed that a fully crystallized apatite layer was present on the particulate after 3 days of exposure in SBF solution. These findings are consistent with those associated with amorphous Bioglass particles.

Prospects for in vivo Raman spectroscopy

Raman spectroscopy is a potentially important clinical tool for real-time diagnosis of disease and in situ evaluation of living tissue. The purpose of this article is to review the biological and physical basis of Raman spectroscopy of tissue, to assess the current status of the field and to explore future directions. The principles of Raman spectroscopy and the molecular level information it provides are explained. An overview of the evolution of Raman spectroscopic techniques in biology and medicine, from early investigations using visible laser excitation to present-day technology based on near-infrared laser excitation and charge-coupled device array detection, is presented. State-of-the-art Raman spectrometer systems for research laboratory and clinical settings are described. Modern methods of multivariate spectral analysis for extracting diagnostic, chemical and morphological information are reviewed. Several in-depth applications are presented to illustrate the methods of collecting, processing and analysing data, as well as the range of medical applications under study. Finally, the issues to be addressed in implementing Raman spectroscopy in various clinical applications, as well as some long-term directions for future study, are discussed.

Spatial distribution of phosphate species in mature and newly generated Mammalian bone by hyperspectral Raman imaging

Hyperspectral Raman images of mineral components of trabecular and cortical bone at 3 μm spatial resolution are presented. Contrast is generated from Raman spectra acquired over the 600-1400 cm-1 Raman shift range. Factor analysis on the ensemble of Raman spectra is used to generate descriptors of mineral components. In trabecular bone independent phosphate (PO4-3) and monohydrogen phosphate (HPO4-2) factors are observed. Phosphate and monohydrogen phosphate gradients extend from trabecular packets into the interior of a rod. The gradients are sharply defined in newly regenerated bone. There, HPO4-2 content maximizes near a trabecular packet and decreases to a minimum value over as little as a 20 μm distance. Incomplete mineralization is clearly visible. In cortical bone, factor analysis yields only a single mineral factor containing both PO4-3 and HPO4-2 signatures and this implies uniform distribution of these ions in the region imaged. Uniform PO4-3 and HPO4-2 distribution is verified by spectral band integration. © 1999 Society of Photo-Optical Instrumentation Engineers.

Composition, constitution, and interaction of bone with hydroxyapatite coatings determined by FT Raman microscopy

An optimized FT Raman microscope (inverted microscope with high throughput of radiation) was developed that allows minimal sample preparation and Raman spectroscopy without fluorescence. A quantitative determination of the mineralization of bone tissue and hydroxyapatite (HA) coatings of hip and knee prostheses was performed. The lateral resolution reached down to 10 microm. The distribution of the HA content in the coatings investigated was found to be similar all the time. This result was independent of the composition of the coatings and the history of the whole prosthesis. In the immediate vicinity of the prosthesis a large HA content could be observed that decreased to a minimum towards the periphery of the coating and increased at the site of the ongrown bone. For the interface between bone and HA coating a transitional zone was observed at a lateral distance of 30-40 microm to the implant.