Applications of Raman Spectroscopy in Dentistry: Analysis of Tooth Structure

Abstract: Tooth enamel is the most mineralized tissue in the human body, and in this article the use of Raman spectroscopy for the analysis of tooth structure, a comparison with synthetic apatites, and use in dentistry are described. Spectral peaks that are related to dental hard and soft tissues are discussed, which provide crucial data in understanding the chemical structural properties of dentin and enamel. The Raman spectrum of dentin confirms the presence of crystalline phosphate-based minerals in dentin. Both dentin and enamel consist of two primary components: an inorganic or mineral phase that closely resembles hydroxyapatite and the Raman spectrum of dentin that confirms the presence of crystalline phosphate-based minerals in dentin. Hence, the mineral phase in dentin and enamel may be characterized essentially as nonstoichiometric substituted apatite. The presence of carbonate (A and B type) incorporated in the hydroxyapatite lattice is also confirmed by the presence of spectral bands. The organic phase, which is mainly composed of type I collagen, is confirmed by the spectral bands of amide I and amide II bands, tryptophan, and phenylalanine. Furthermore, these spectral bands associated with organic and inorganic parts of the enamel and dentin are useful in predicting early formation of carries formation.     

Raman Spectroscopy of Natural Bone and Synthetic Apatites

Abstract

Raman spectroscopy of natural bones and hydroxyapatites is described. In addition, how Raman spectroscopy has proved crucial in providing baseline data for the modification of synthetic apatite powders that are routinely used now as bone replacement materials is explained. It is important to understand the chemical structural properties of natural bone. Bone consists of two primary components: an inorganic or mineral phase, which is mainly a carbonated form of a nanoscale crystalline calcium phosphate, closely resembling hydroxyapatite, and an organic phase, which is composed largely of type I collagen fibers. Other constituents of bone tissue include water and organic molecules such as glycosaminoglycans, glycoproteins, lipids, and peptides. Ions such as sodium, magnesium, fluoride, and citrate are also present, as well as hydrogenophosphate. Hence, the mineral phase in bone may be characterized essentially as nonstoichiometric substituted apatite. Such a distinction is important in the development of synthetic calcium phosphates for application as skeletal implants. An understanding of bone function and its interfacial relationship to an implant clearly depends on the associated structure and composition. Therefore, it is essential to fully understand the chemical composition of bone, and Raman spectroscopy is an excellent technique for such an analysis.     

The Effect of Blood Contamination on the Chemical Characterization of Hydrated Mineral Trioxide Aggregates and Their Dentin-Interface: A Comparative Study

The presence of blood contamination could affect the chemical characterization of mineral trioxide aggregates as endodontic repair material during surgical approach. The aim of this study was to assess and compare the chemical characterization of two white mineral trioxide aggregates (ProRoot and Angelus) mixed with blood versus water. ProRoot and Angelus were mixed with either distilled water, fresh human blood, or diluted blood and analyzed using Fourier transform infrared spectroscopy. The same materials were packed inside holes in dentin blocks for scanning electron microscopy with energy-dispersive X-ray. Gray Portland cement was used as a control. The infrared spectra of unhydrate powders showed an increase in alite in ProRoot and Angelus, belite in Portland cement, and calcium hydroxide in Angelus. Upon hydration, changes in these bands were detected. Energy-dispersive X-ray displayed significantly higher calcium, aluminum, and phosphorous in hydrated Angelus and silicon in hydrated ProRoot (p < 0.05). No phosphorous was detected in ProRoot. Traces of iron were detected in blood groups. A granular pattern was observed at the hydrated material of all tested groups. Definitive gaps were detected at certain areas within hydrated material and its dentin-interface, particularly in blood-contaminated groups. It was supported with the appearance of new bands assigned to Amide I and II of blood protein. It was concluded that the presence of blood during the hydration process of mineral trioxide aggregates produced small gaps of protein impurities within the hydrated material, affecting its chemical behavior and dentin/material-interface integrity.     

傅里叶变换红外光谱法研究PLGA微球中葡激酶突变体(K35R)的二级结构

用复乳溶剂挥发法制备了葡激酶突变体(K35R,DGR)的PLGA微球,并用傅里叶变换红外光谱法(FTIR)定量研究了PLGA微球内DGR的二级结构。 将可增强分辨率的傅里叶去卷积技术与高斯曲线拟合技术共同用于对微球内DGR酰胺Ⅰ带的定量分析,发现DGR酰胺Ⅰ带共包含9个红外吸收峰,并对各组份进行了归属。 此外,还对微球内DGR结构稳定性相关的1 623和1 650 cm-1吸收峰进行了讨论。     

红外和拉曼光谱的煤灰矿物组成研究

研究煤灰中矿物质的性质通常从矿物组成的表征入手。为了分析两种高硅铝煤灰的矿物成分,采用傅里叶变换红外光谱(FTIR)、拉曼光谱和X射线衍射(XRD)技术对煤灰样进行了测试和综合表征,将FTIR和拉曼光谱的分析结果与XRD进行了比较。FTIR结果表明,在1 100~1 000 cm-1范围内高硅铝煤灰出现最强的特征峰,例如石英峰(1 089 cm-1)和偏高岭石峰(1 042 cm-1),它们都归属于Si-O伸缩振动。对原始红外谱图进行二阶导数处理后,可获得重叠峰的峰位,有助于更完整的解析矿物吸收峰,从而获得更丰富的矿物组成信息。煤灰中硬石膏的红外和拉曼光谱发现,在1 157,1 126和674 cm-1的拉曼光谱峰与在1 151,1 120和678 cm-1的红外光谱峰振动模式分别相同且峰位接近,还存在一些完全不同的拉曼光谱与红外光谱峰,表明这两种光谱存在互补性。尽管煤灰中锐钛矿含量很低,但由于Ti-O的极化率很高,因此拉曼光谱显示锐钛矿的144 cm-1峰远远强于石英的461 cm-1峰。XRD结果表明,煤灰中主要存在石英、云母、赤铁矿、硬石膏和未知的无定形相矿物,FTIR和拉曼光谱综合分析的结果表明除了这些矿物,还存在偏高岭石、无定形氧化硅、长石、方解石和锐钛矿等。在定性分析方面,将FTIR和拉曼光谱结合起来比XRD单独获得的矿物组成信息更为详细。     

宫颈正常与宫颈癌组织傅里叶变换红外光谱的初步研究

利用傅里叶变换红外光谱对宫颈鳞癌(17例)、宫颈腺癌(5例)及宫颈正常组织(13例)进行了分析。结果显示,18个谱带在各类组织中的出现概率都在80%以上,显示其在组织中的特征性;这3类组织红外光谱的相对吸收峰吸光度差异主要表现在1 080,1 238,1 314,1 339,1 397,1 454,1 541,1 647,2 854, 2 873,2 926和2 958 cm-1处的比较上。傅里叶变换红外光谱仪可用于区分宫颈鳞癌、腺癌及宫颈正常组织,以该仪器为基础的方法有望成为宫颈癌筛检及临床诊断的新方法。     

傅里叶变换红外光谱用于肿瘤细胞株检测的研究

采取在体外培养胃癌细胞株(SGC7901), 将培养细胞涂于BaF₂窗片的方法,应用美国Nicolet(尼高力)公司Magna750-Ⅱ型红外光谱仪对细胞株进行透射红外光谱检测, 得到了时间轴上体外培养细胞株的光谱图, 将特征性光谱与胃癌组织光谱进行了比对。发现胃癌细胞株红外光谱特征与相应癌组织光谱特征存在异同,说明细胞胃癌组织所表现的红外光谱特征可以反映胃癌细胞本身的红外光谱特征, 同时也具有自身的复杂特点。实验为红外光谱法诊断胃癌奠定了细胞学基础。     

Variable Angle ATR–FTIR Study of the Surface Aminolysis of Poly(Ethylene Terephthalate) Films

Hydrophobic surfaces of poly(ethylene terephtalate) films were modified by using a mild wet chemical procedure with triethylenetetramine as a reagent. The chemical composition was determined by Fourier transform infrared (FTIR) spectroscopy. With the aim of obtaining the depth profile of the newly created species the variable angle attenuated total reflectance (ATR)–FTIR spectroscopy was used. The most important functionalities resulting from the aminolysis that we chose to monitor were amide groups. By varying the incidence angle of the infrared radiation, chemical changes were investigated from layers of different thicknesses. It was observed that the absorption bands attributed to amide moieties became weaker with increasing analyzed depth, with a pronounced heterogeneity near the surface. By assuming an exponential decay for the depth profile spectrally obtained, the surface concentration of amide groups and the decay constant were determined for the reaction times used.     

羚羊角及其角塞的傅里叶红外光谱快速识别研究

采用傅里叶变换红外光谱(FTIR)技术,对羚羊角、羚羊角塞以及二者的混合物进行了对比研究。结果表明:羚羊角的红外光谱主要由蛋白质组分的特征吸收峰组成,而羚羊角塞的红外光谱主要由蛋白质和磷酸钙组分的特征吸收峰构成,二者的酰胺谱带、C—O伸缩振动谱带以及CH基团的伸缩振动谱带也均有明显区别。通过上述差异,可有效地鉴别羚羊角、角塞以及掺有角塞的羚羊角样品。该研究为羚羊角的掺伪和杂质检查提供了快速、科学的新方法,也为羚羊角的成分与质量评价体系研究提供了一定的信息。     

Molecular structural analysis of noncarious cervical sclerotic dentin using Raman spectroscopy

Molecular structure of the sclerotic dentin in noncarious cervical lesions (NCCLs) including both the inorganic phase and organic phase was investigated using Raman spectroscopy. It was found that NCCL sclerotic dentin was hypermineralized with the mineral/matrix ratios 2–3 times higher than those of normal dentin, which was caused by both the increase of mineral content and decrease of organic matrix (collagen) content in the sclerotic dentin. For the inorganic phase, the phosphate band (PO₄³⁻, ν₁, symmetric stretching vibrational mode) in NCCL sclerotic dentin was shifted from 960 to 963 cm⁻¹, and the width of this band was decreased from 16.4 to 10.4 cm⁻¹, indicating that the degree of mineral crystallinity in NCCL sclerotic dentin was higher than that of normal dentin. In addition, the carbonate content in the mineral of NCCL sclerotic dentin was less than that of normal dentin. As compared to the inorganic phase, the changes within the organic phase were not dramatic. However, the changes in collagen cross‐link density along with other spectral changes were still detectable. There was a noteworthy reduction in the ratio of nonreducible to reducible cross‐links in the NCCL sclerotic dentin, indicating that cross‐link breaks occurred in the collagen matrix of the lesions. Copyright © 2009 John Wiley & Sons, Ltd.     

甲状腺癌的傅里叶变换红外光谱研究

应用傅里叶变换红外光谱仪,测定了17例甲状腺癌和23例良性甲状腺疾病术中新鲜离体组织的红外光谱。通过用统计学方法对比分析,发现甲状腺良恶性组织的傅里叶红外光谱之间存在明显差异,其中恶性肿瘤光谱有以下特征：(1)甲状腺癌组织的酰胺Ⅰ带明显红移(P<0.01),酰胺Ⅱ带却出现蓝移(P<0.05),癌组织光谱中I_{1 640}/I_{1 460}和I_{1 640}/I_{1 550}较良性组织明显升高(P<0.01),说明恶性肿瘤不仅蛋白质结构上发生了变化,蛋白质的量化上也有明显变化;(2)与脂类相关的2 955, 2 920, 2 870, 2 850和1 740 cm-1谱带出现概率明显变低,表明癌组织的脂类相对含量降低;(3)与核酸相关的1 241 cm-1谱带明显蓝移至(1 238.29±2.87)cm-1 ,I_{1 080}/I_{1 460}较良性肿物组织有升高(P<0.05),表明癌组织中磷酸二酯基团中PO₂增加,因为在癌细胞分裂增生加快,细胞核内DNA含量增加。研究结果表明,红外光谱有望成为术中快速诊断甲状腺恶性肿瘤的主要方法。     

应用红外光谱技术研究中药水蛭的炮制过程

考察水蚝炮制前后化学成分产生的变化,文章采用红外光谱(FTlR)二维相关红外谱图(2D-IR)对中药水蛭鲜品和制品进行了研究.结果表明:水蛭具有明显的酰胺Ⅰ和Ⅱ带蛋白质特征峰,其中鲜品的酰胺Ⅱ带吸收峰在1543 cm-1,而生品和炮制品的向低频位移至1 535cm-1;采用热微扰模拟水蛭炮制过程并分析水蛭的2D-IR,结果显示水蛭鲜品中的酰胺Ⅰ带与酰胺Ⅱ带的自动峰的强度比炮制品的更为显著.说明水蛭在炮制过程中蛋白质的空间构象破损、氢键断裂,导致变性失活,部分脂肪酸和甾醇类组分在炮制中发生氧化分解.     

Structural and Spectroscopic Investigation of Biomimetic Composites—Promising Agents for the Remineralization of Native Dental Tissue

Biomimetic materials (biocomposites) with an organic-mineral composition related to natural dental tissues (enamel and dentin) are obtained for the first time and their structural and optical characteristics are studied. It is demonstrated by a complex of structural and spectroscopic methods that in the formation of biocomposites, the introduced organic component, bearing a number of amino acids, does not affect the structure of the inorganic component (carbonate-substituted calcium hydroxyapatite) of the sample. The carbonate-substituted calcium hydroxyapatite synthesized using a biogenic source of calcium, which forms the basis of the biocomposite, has a luminescence spectrum similar to that of apatite tooth enamel. The spectrum of the intact dentin of a human tooth has a broader luminescence band than that for the enamel spectrum. It is determined that both organic and inorganic components contribute to the dentin luminescence band. The features found in the luminescence spectra of intact tissues and in simulating biocomposites can be used to develop a procedure for effective early diagnosis of the demineralization of hard dental tissues and general dental examination.     

恶性多形性腺瘤及其周围正常组织的FTIR光谱研究

文章根据医院临床需要,利用PE公司的Spectrum GX傅里叶变换红外光谱仪研究了多组恶性多形性腺瘤及其周围正常组织结构的FTIR光谱.结果发现:恶性多形性腺瘤与其周围正常组织的红外傅里叶光谱在若干波段处有所不同:相对于正常组织,癌变后核酸分子中的磷酸二脂基团的对称伸缩振动谱带、蛋白质的酰胺Ⅰ带的红外光谱都向高波数移动且吸收都得到增强,说明癌变多形性腺瘤的核酸和蛋白质的氢键化程度普遍增高,吸收普遍增强;而膜脂分子中亚甲基的无序性增加,吸收随之增强.就此可将多形性腺瘤癌区通过红外光谱从正常组织中区分出来.     

直肠癌和直肠正常组织的傅里叶变换红外光谱研究

利用傅里叶变换中红外 (FTIR)光纤和ATR技术研究了 2 1例直肠癌病人的正常和癌变组织。对319张光谱进行数据分析的结果表明 ,五个相对峰高 (I2 873 I2 854,I1 74 5 I1 6 43,I1 458 I1 40 0 ,I1 2 4 0 I1 31 5和I1 1 6 2 I1 0 82,单位为cm- 1 )的差别可用于区分直肠癌和直肠正常组织。用这一差别分析了距离直肠癌 1cm处组织的光谱 ,发现该组织处于正常和癌变的过渡状态。     

西北旱作农田黄土指纹图谱的光谱学鉴定

采用扫描电子显微镜(SEM)、 X射线荧光光谱(XRF)、 X射线衍射(XRD)、 傅里叶变换红外光谱(FTIR) 等手段对西北典型旱作农田黄土样品进行表征,Tessier连续提取法分析黄土Pb的赋存形态及含量。结果发现：黄土样品比表面积较大 (291 m2·g-1),粉粒土壤占到80.87%的比例。黄土表面轮廓清晰,可见颗粒聚集形成叠片状结构,晶片厚约3～5 μm。黄土矿物相主要为石英和钾云母,同时含有少量钾长石和蛇纹石等。FTIR图谱表明高岭石和方解石也是构成黄土样品的重要组分,但有机质的特征峰不明显,说明土样中有机质含量较低。Tessier连续提取法表明：土样中Pb全量比陕西省和全国土壤Pb的平均含量要高,其中残渣态Pb占Pb全量的64.04%。黄土指纹图谱的鉴定可以为后续污染土壤修复研究提供参考。     

Picosecond thermometer in the amide I band of myoglobin

The amide I and II bands in myoglobin show a heterogeneous temperature dependence, with bands at 6.17 and 6.43 microm which are more intense at low temperatures. The amide I band temperature dependence is on the long wavelength edge of the band, while the short wavelength side has almost no temperature dependence. We compare concepts of anharmonic solid-state crystal physics and chemical physics for the origins of these bands. We suggest that the long wavelength side is composed of those amino acids which hydrogen bond to the hydration shell of the protein, and that temperature dependent bands can be used to determine the time it takes vibrational energy to flow into the hydration shell. We determine that vibrational energy flow to the hydration shell from the amide I takes approximately 20 ps to occur.     

利用红外光谱评价文物微环境中有机酸对蚕丝纤维化学结构影响

研究文物微环境污染因素对文物材料影响是分析文物老化原因和妥善保存文物的重要基础。利用红外光谱(FTIR/ATR)剖析了文物微环境中甲酸、乙酸气体对蚕丝纤维结构影响。结果表明:低浓度甲酸气体能减弱纤维分子内氢键,使酰胺Ⅰ(1 617cm-1)谱峰减弱、酰胺Ⅱ谱峰(1 515cm-1)变窄、无规线团构象的酰胺Ⅲ谱峰(1 230cm-1)增强、纤维结晶度下降;当浓度高于8.1mg.m-3时,呈β-折叠构象的肽链段(GlyAla)n特征谱峰(1 000,975cm-1)增强、纤维结晶度提高。分析认为呈无规线团构象的短肽链发生β-折叠构象转变。乙酸气体对酰胺Ⅰ和酰胺Ⅱ谱峰影响不明显,但能引起无规线团构象增加和纤维结晶度降低,其作用弱于甲酸气体。本研究为进一步分析丝织品保存环境污染物的危害作用提供基础数据。     

采用FTIR技术研究高压处理对冻干大豆分离蛋白构象的影响

采用傅里叶转换红外光谱技术(FTIR)研究了高压(HP)处理对冷冻干燥的大豆分离蛋白(SPI)构象的影响。在SPI的去卷积FTIR光谱的酰胺Ⅰ′区域(1 600～1 700 cm-1),观察到12个与蛋白构象相关的红外吸收峰,分别对应于CO键伸缩振动与肽键的C—N伸缩振动。通过对该区域的峰强度与波数分析显示,压力为200～400 MPa的HP处理导致SPI在该区域的峰发生明显的“红移”(约2 cm-1),强度也显著增加。更高的HP处理进一步增强了SPI的酰胺Ⅰ′区域的峰强度。对酰胺Ⅱ峰分析显示,HP处理导致酰胺Ⅱ峰(如1 560～1 500 cm-1)的强度、面积逐渐增加(与压力呈正相关)。以上分析显示,HP处理导致SPI的二级与三级结构逐渐打开,然而变性蛋白的结构在高压释放后经历一个“重构过程”。     

鲤鱼耳石的拉曼及红外光谱特征研究

鱼耳石是存在于硬骨鱼内耳中的功能性沉积体,主要由碳酸钙和有机质构成,是一种典型的天然生物矿物。鱼的内耳中共有微耳石、星耳石、矢耳石各1对。利用FTIR光谱和Raman光谱对实验室中养殖锦鲤的星耳石和微耳石进行了对比分析,结果表明微耳石的矿物相为文石,而星耳石的矿物相则为球文石,微耳石中纯文石和星耳石中纯球文石的各自独立存在为文石/球文石的矿化机理研究提供了十分优异的天然样品。分别将其与无机和生物成因的文石、球文石的Raman及FTIR图谱进行比较,发现微耳石的FTIR和Raman图谱特征介于无机成因文石和其他生物成因文石之间,而星耳石的FTIR和Raman图谱特征则与其他生物成因的球文石更为接近,这可能是由于有机物参与了生物矿化过程并起到了稳定介稳相的球文石的结果。