Exploring type II microcalcifications in benign and premalignant breast lesions by shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS)

Raman spectroscopy: current applications in breast cancer diagnosis, challenges and future prospects

Despite significant improvements in the way breast cancer is managed and treated, it continues to persist as a leading cause of death worldwide. If detected and diagnosed early, when tumours are small and localised, there is a considerably higher chance of survival. However, current methods for detection and diagnosis lack the required sensitivity and specificity for identifying breast cancer at the asymptomatic or very early stages. Thus, there is a need to develop more rapid and reliable methods, capable of detecting disease earlier, for improved disease management and patient outcome. Raman spectroscopy is a non-destructive analytical technique that can rapidly provide highly specific information on the biochemical composition and molecular structure of samples. In cancer, it has the capacity to probe very early biochemical changes that accompany malignant transformation, even prior to the onset of morphological changes, to produce a fingerprint of disease. This review explores the application of Raman spectroscopy in breast cancer, including discussion on its capabilities in analysing both ex-vivo tissue and liquid biopsy samples, and its potential in vivo applications. The review also addresses current challenges and potential future uses of this technology in cancer research and translational clinical application.

A universal polymer shell-isolated nanoparticle (SHIN) design for single particle spectro-electrochemical SERS sensing using different core shapes

Shell-isolated nanoparticles (SHINs) have attracted increasing interest for non-interfering plasmonic enhanced sensing in fields such as materials science, biosensing, and in various electrochemical systems. The metallic core of these nanoparticles is isolated from the surrounding environment preventing direct contact or chemical interaction with the metal surface, while still being close enough to enable localized surface plasmon enhancement of the Raman scattering signal from the analyte. This concept forms the basis of the shell isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) technique. To date, the vast majority of SHIN designs have focused on SiO₂ shells around spherical nanoparticle cores and there has been very limited published research considering alternatives. In this article, we introduce a new polymer-based approach which provides excellent control over the layer thickness and can be applied to plasmonic metal nanoparticles of various shapes and sizes without compromising the overall nanoparticle morphology. The SHIN layers are shown to exhibit excellent passivation properties and robustness in the case of gold nanosphere (AuNP) and anisotropic gold nanostar (AuNS) core shapes. In addition, in situ SHINERS spectro-electrochemistry measurements performed on both SHIN and bare Au nanoparticles demonstrate the utility of the SHIN coatings. Correlated confocal Raman and SEM mapping was achieved to clearly establish single nanoparticle SERS sensitivity. Finally, confocal in situ SERS mapping enabled visualisation of the redox related molecular structure changes occurring on an electrode surface in the vicinity of individual SHIN-coated nanoparticles.

SERS substrate fabrication for biochemical sensing: towards point-of-care diagnostics

Rapid technology development and economic growth have brought attention to public health issues, such as food safety and environmental pollution, which creates an ever-increasing demand for fast and portable sensing technologies. Portable surface-enhanced Raman spectroscopy (SERS) capable of various analyte detection with low concentration in a convenient manner shows advantages in sensing technology including enhanced diagnostic precision, improved diagnostic efficiency, reduced diagnostic cost, and alleviation of patient pain, which emerges as a promising candidate for point-of-care testing (POCT). SERS detection technology based on different nanostructures made of noble metal-based nanomaterials can increase the sensitivity of Raman scattering by 6-8 orders of magnitude, making Raman based trace detection possible, and greatly promote the application scenarios of portable Raman spectrometers. In this perspective, we provide an overview of fundamental knowledge about the SERS mechanism including chemical and electromagnetic field enhancement mechanisms, the design and fabrication of SERS substrates based on materials, progress of using SERS for POCT in biochemical sensing and its clinical applications. Furthermore, we present the prospective of developing new nanomaterials with different functionalities for advanced SERS substrates, as well as the future advancement of biomedical sensing and clinical potential of SERS technology.

Studying the pathological and biochemical features in breast cancer progression by confocal Raman microspectral imaging of excised tissue samples

Confocal Raman microspectral imaging (CRMI) has been used to detect the spectra-pathological features of ductal carcinoma in situ (DCIS) and lobular hyperplasia (LH) compared with the heathy (H) breast tissue. A total of 15-20 spectra were measured from healthy tissue, LH tissue, and DCIS tissue. One-way ANOVA and Tukey's honest significant difference (HSD) post hoc multiple tests were used to evaluate the peak intensity variations in all three tissue types. Besides that, linear discrimination analysis (LDA) algorithm was adopted in combination with principal component analysis (PCA) to classify the spectral features from tissues at different stages along the continuum to breast cancer. Moreover, by using the point-by-point scanning methodology, spectral datasets were obtained and reconstructed for further pathologic visualization by multivariate imaging methods, including K-mean clustering analysis (KCA) and PCA. Univariate imaging of individual Raman bands was also used to describe the differences in the distribution of specific molecular components in the scanning area. After a detailed spectral feature analysis from 800 to 1800 cm^-1 and 2800 to 3000 cm^-1 for all the three tissue types, the histopathological features were visualized based on the content and structural variations of lipids, proteins, phenylalanine, carotenoids and collagen, as well as the calcification phenomena. The results obtained not only allowed a detailed Raman spectroscopy-based understanding of the malignant transformation process of breast cancer, but also provided a solid spectral data support for developing Raman based breast cancer clinical diagnostic techniques.

Molecular fingerprint of precancerous lesions in breast atypical hyperplasia

OBJECTIVE

To identify atypical hyperplasia (AH) of the breast by shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS), and to explore the molecular fingerprinting characteristics of breast AH.

METHODS

Breast hyperplasia was studied in 11 hospitals across China from January 2015 to December 2016. All patients completed questionnaires on women's health. The differences between patients with and without breast AH were compared. AH breast lesions were detected by Raman spectroscopy followed by the SHINERS technique.

RESULTS

There were no significant differences in clinical features and risk-related factors between patients with breast AH (n = 37) and the control group (n = 2576). Fifteen cases of breast AH lesions were detected by Raman spectroscopy. The main different Raman peaks in patients with AH appeared at 880, 1001, 1086, 1156, 1260, and 1610 cm^-1, attributed to the different vibrational modes of nucleic acids, β-carotene, and proteins. Shell-isolated nanoparticles had different enhancement effects on the nucleic acid, protein, and lipid components in AH.

CONCLUSION

Raman spectroscopy can detect characteristic molecular changes in breast AH lesions, and may thus be useful for the non-invasive early diagnosis and for investigating the mechanism of tumorigenesis in patients with breast AH.

Plasmonic Core-Shell Nanoparticle Enhanced Spectroscopies for Surface Analysis

Probing the properties and components of reactive surfaces is crucial for illustrating reaction mechanisms. However, common surface analysis techniques are restricted to in situ acquisition of surface information at the molecular scale in the human environment and industrial catalysis processes. Plasmonic spectroscopies are promising tools to solve this problem. This Feature is intended to introduce the plasmonic core-shell nanoparticle enhanced spectroscopies for qualitatively and quantitatively analyzing surface trace species. Four different working modalities are designed for meeting varied needs, involving in situ surface species detection, catalytic process monitoring, labeled sensing, and dual mode analysis. These newly developed plasmonic spectroscopies show great potential not only in fundamental research but also in practical applications.

Clinicopathologic update of calcium oxalate in breast: A 15-year retrospective review

Mammary malignancies are radiologically detected by presence of masses, architectural distortions or microcalcifications. Unlike calcium hydroxyapatite, calcium oxalate (CaOx) deposits have been almost exclusively associated with benign mammary processes. The etiology and mechanism of mammary CaOx deposition remains poorly understood, and the original studies elucidating its histopathologic correlation are dated several decades ago. We reviewed radiopathologic findings of breast biopsies and excisions to re-examine the clinicopathologic significance of CaOx deposits and to ascertain potential radiologic characteristics for their identification. Fifty patients from 2004 to 2019 with reported "calcium oxalate" were retrospectively reviewed. CaOx was invariably detected with histopathologic changes of nonproliferative ducts/cysts (90%, 45 of 50), and less commonly, ducts/cysts with usual ductal hyperplasia (10%, 5 of 50). CaOx was missed on one biopsy with a subsequent excision showing apocrine cyst with CaOx. Despite the benign pathological findings, mammographic findings corresponding to CaOx ranged from benign to highly suspicious with 20% categorized as benign (round or punctuate), 22% as intermediate amorphous, 14% as suspicious (coarse/heterogeneous), and 18% as highly suspicious/pleomorphic, respectively. Lobular carcinoma in situ (LCIS) was present in separate fields from CaOx containing benign ducts in two cases which were radiologically characterized as "grouped heterogeneous" and "localized linear." On imaging, more than half of the cases (52.5%) had a corresponding BI-RADS score of 4 and the calcifications were associated with variable distributions and appearances. In conclusion, this is one of the largest studies of CaOx in breast with radiology and pathology correlation. The radiologic appearances of CaOx are nonspecific from benign to highly suspicious. Identification of CaOx on the biopsy is reassuring for a benign diagnosis. Incidental atypical lesions can occur that are often not directly associated with CaOx. CaOx may be overlooked on pathologic evaluation which results in unnecessary surgery. Our findings support close radiologic-pathologic correlation for clinical decision-making pertaining to breast calcifications.

Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy

In 2010, Tian et al. reported the development of a new, relatively sensitive method of the chemical analysis of various surfaces, including buried interfaces (for example the surfaces of solid samples in a high-pressure gas or a liquid), which makes it possible to analyze various biological samples in situ. They called their method shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). SHINERS spectroscopy is a type of surface-enhanced Raman spectroscopy (SERS) in which an increase in the efficiency of the Raman scattering is induced by plasmonic nanoparticles acting as electromagnetic resonators that locally significantly enhance the electric field of the incident electromagnetic radiation. In the case of SHINERS measurements, the plasmonic nanoparticles are covered by a very thin transparent protective layer (formed, for example, from various oxides such as SiO2, MnO2, TiO2, or organic polymers) that does not significantly damp surface electromagnetic enhancement, but does separate the nanoparticles from direct contact with the probed material and keeps them from agglomerating. Preventing direct contact between the metal plasmonic structures and the analyzed samples is especially important when biological samples are investigated, because direct interaction between the metal nanoparticles and various biological molecules (e.g., peptides) may lead to a change in the structure of those biomolecules. In this mini-review, the state of the art of SHINERS spectroscopy is briefly described.

Identification of breast cancer through spectroscopic analysis of cell-membrane sialic acid expression

Identification of specific and reliable biomarkers or unique characteristics is significant for cancer molecular diagnosis and cancer therapeutic assessment. As a biomarker, sialic acid expression in human biofluid or on cell surface is one of interest to determine the tumor malignancy and metastasis since it involves in many crucial metabolic processes. In this work, we aimed to develop a molecular diagnosis method to make it possible to distinguish human breast cancer and normal tissues by capturing rich spectral features of phenyboronic acid-based nanoprobe (MPBA@AgNP) when it binds to sialic acid on cell surface. We analyzed and found that the marker bands at 1074 and 1570 cm^-1 recorded by Surface-enhanced Raman spectroscopy (SERS) displayed discernible spectral differences in vitro cell lines. Density functional theory (DFT) was further used to explore and support the detailed changes of vibrational modes affected by sialic acid. This method is generally applicable by testing three types of in vitro cell lines (HepG2, Hela, BNL.CL2) and one pair of the tissue sections (cancer tissue and normal tissue) from the human breast regions. Besides, the area under receiver operating characteristic (ROC) curves for 1074 and 1572 cm^-1 are 0.9419 and 0.9023, confirming determination of the specific molecular expression by the spectral features holds potential promise for improving cancer detection accuracy. Furthermore, sialic acid expression and distribution acquired of breast tissues by confocal SERS mapping further indicated our method is possible for cancer early diagnosis and toward to real-time in vivo study.

Label-Free Molecular Imaging of Biological Cells and Tissues by Linear and Nonlinear Raman Spectroscopic Approaches

Raman spectroscopy is an emerging technique in bioanalysis and imaging of biomaterials owing to its unique capability of generating spectroscopic fingerprints. Imaging cells and tissues by Raman microspectroscopy represents a nondestructive and label-free approach. All components of cells or tissues contribute to the Raman signals, giving rise to complex spectral signatures. Resonance Raman scattering and surface-enhanced Raman scattering can be used to enhance the signals and reduce the spectral complexity. Raman-active labels can be introduced to increase specificity and multimodality. In addition, nonlinear coherent Raman scattering methods offer higher sensitivities, which enable the rapid imaging of larger sampling areas. Finally, fiber-based imaging techniques pave the way towards in vivo applications of Raman spectroscopy. This Review summarizes the basic principles behind medical Raman imaging and its progress since 2012.

Pursuing shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) for concomitant detection of breast lesions and microcalcifications

Although tissue staining followed by morphologic identification remains the gold standard for diagnosis of most cancers, such determinations relying solely on morphology are often hampered by inter- and intra-observer variability. Vibrational spectroscopic techniques, in contrast, offer objective markers for diagnoses and can afford disease detection prior to alterations in cellular and extracellular architecture by furnishing a rapid "omics"-like view of the biochemical status of the probed specimen. Here, we report a classification approach to concomitantly detect microcalcification status and local pathological state in breast tissue, featuring a combination of vibrational spectroscopy that focuses on the tumor and its microenvironment, and multivariate data analysis of spectral markers reflecting molecular expression. We employ the unprecedented sensitivity and exquisite molecular specificity offered by Au@SiO2 shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) to probe the presence of calcified deposits and distinguish between normal breast tissues, fibroadenoma, atypical ductal hyperplasia, ductal carcinoma in situ (DCIS), and invasive ductal carcinoma (IDC). By correlating the spectra with the corresponding histologic assessment, we developed partial least squares-discriminant analysis derived decision algorithm that provides excellent diagnostic power in the fresh frozen sections (overall accuracy of 99.4% and 93.6% using SHINs for breast lesions with and without microcalcifications, respectively). The performance of this decision algorithm is competitive with or supersedes that of analogous algorithms employing spontaneous Raman spectroscopy while enabling facile detection due to the considerably higher intensity of SHINERS. Our results pave the way for rapid tissue spectral pathology measurements using SHINERS that can offer a novel stain-free route to accurate and economical diagnoses without human interpretation.