Raman Spectroscopy: Guiding Light for the Extracellular Matrix

Abstract

The extracellular matrix (ECM) consists of a complex mesh of proteins, glycoproteins, and glycosaminoglycans, and is essential for maintaining the integrity and function of biological tissues. Imaging and biomolecular characterization of the ECM is critical for understanding disease onset and for the development of novel, disease-modifying therapeutics. Recently, there has been a growing interest in the use of Raman spectroscopy to characterize the ECM. Raman spectroscopy is a label-free vibrational technique that offers unique insights into the structure and composition of tissues and cells at the molecular level. This technique can be applied across a broad range of ECM imaging applications, which encompass in vitro, ex vivo, and in vivo analysis. State-of-the-art confocal Raman microscopy imaging now enables label-free assessments of the ECM structure and composition in tissue sections with a remarkably high degree of biomolecular specificity. Further, novel fiber-optic instrumentation has opened up for clinical in vivo ECM diagnostic measurements across a range of tissue systems. A palette of advanced computational methods based on multivariate statistics, spectral unmixing, and machine learning can be applied to Raman data, allowing for the extraction of specific biochemical information of the ECM. Here, we review Raman spectroscopy techniques for ECM characterizations over a variety of exciting applications and tissue systems, including native tissue assessments (bone, cartilage, cardiovascular), regenerative medicine quality assessments, and diagnostics of disease states. We further discuss the challenges in the widespread adoption of Raman spectroscopy in biomedicine. The results of the latest discovery-driven Raman studies are summarized, illustrating the current and potential future applications of Raman spectroscopy in biomedicine.

Detection of Age-Related Changes in Tendon Molecular Composition by Raman Spectroscopy—Potential for Rapid, Non-Invasive Assessment of Susceptibility to Injury

“…Since it has been shown that fascicles and interfascicular matrix have different proteomic profiles and demonstrate different age-related changes [43], differences in the Raman spectra can be expected. Future studies could use Raman spectroscopy to interrogate cells directly [12,14,15] and perform label-free classification of different cell populations in fascicles and the IFM, overcoming some of the current technological difficulties in studying tendon sub-structure composition.…”

Reagent-free Raman and quantitative phase imaging offer a unique morpho-molecular platform for recognition of malignancy and stages of B-cell acute lymphoblastic leukemia

“…Specifically, quantitative phase imaging (QPI) has been used to investigate morphology of live cells and identify disease-specific cellular phenotypes [12][13][14][15][16][17][18][19][20][21][22]. On the other hand, Raman spectroscopy has been employed to measure the biomolecular composition with single cell resolution for cell differentiation and disease identification [23][24][25][26][27][28][29][30][31][32]. Since both the molecular and morphological changes are associated with malignant transformations, we have sought to develop a morphomolecular microscopy (3M) platform, which combines the complementary morphological and biochemical information content into diagnostic frameworks [33,34].…”

Imaging the invisible—Bioorthogonal Raman probes for imaging of cells and tissues

“…Raman spectroscopy has become one of the key analytical technologies in life sciences or biomedicine enabling a label-free detection of the molecular composition of complex samples such as cells and tissues with little or no sample preparation [1][2][3][4]. In combination with microscopy-based imaging, a spatial resolution between 300 and 500 nm can be achieved, which allows for subcellular resolution, for example, imaging the nucleus and lipid droplets inside a single cell [5,6].…”