Biocompatible surface-enhanced Raman scattering nanotags for in vivo cancer detection

Design and Synthesis of SERS Materials for In Vivo Molecular Imaging and Biosensing

Surface-enhanced Raman scattering (SERS) is a feasible and ultra-sensitive method for biomedical imaging and disease diagnosis. SERS is widely applied to in vivo imaging due to the development of functional nanoparticles encoded by Raman active molecules (SERS nanoprobes) and improvements in instruments. Herein, the recent developments in SERS active materials and their in vivo imaging and biosensing applications are overviewed. Various SERS substrates that have been successfully used for in vivo imaging are described. Then, the applications of SERS imaging in cancer detection and in vivo intraoperative guidance are summarized. The role of highly sensitive SERS biosensors in guiding the detection and prevention of diseases is discussed in detail. Moreover, its role in the identification and resection of microtumors and as a diagnostic and therapeutic platform is also reviewed. Finally, the progress and challenges associated with SERS active materials, equipment, and clinical translation are described. The present evidence suggests that SERS could be applied in clinical practice in the future.

Investigation of dual plasmonic core-shell Ag@CuS nanoparticles for potential surface-enhanced Raman spectroscopy-guided photothermal therapy

Aim: To prepare efficient metal-semiconductor nanoparticles as noninvasive, real-time imaging probes for photothermal therapy (PTT) applications. Materials & methods: A bottom-up approach was used to fabricate core-shell Ag@CuS nanoparticles (NPs). PTT and Raman mapping were done using HeLa cells. Theoretical simulation of electric field enhancement and heat dissipation density of Ag@CuS NPs was performed. Results: PTT-induced hyperthermia was achieved under 940 nm near-infrared light irradiation. Surface-enhanced Raman spectroscopy (SERS) signals of dye molecules were observed when conjugated with Ag@CuS NPs. Conclusion: Ag@CuS NPs are found to be efficient for SERS imaging and localized heating under laser irradiation, making a promising candidate for SERS-guided PTT.

Gold Nanoparticles in Cancer Theranostics

Conventional cancer treatments, such as surgical resection, radiotherapy, and chemotherapy, have achieved significant progress in cancer therapy. Nevertheless, some limitations (such as toxic side effects) are still existing for conventional therapies, which motivate efforts toward developing novel theranostic avenues. Owning many merits such as easy surface modification, unique optical properties, and high biocompatibility, gold nanoparticles (AuNPs and GNPs) have been engineered to serve as targeted delivery vehicles, molecular probes, sensors, and so on. Their small size and surface characteristics enable them to extravasate and access the tumor microenvironment (TME), which is a promising solution to realize highly effective treatments. Moreover, stimuli-responsive properties (respond to hypoxia and acidic pH) of nanoparticles to TME enable GNPs’ unrivaled control for effective transport of therapeutic cargos. In this review article, we primarily introduce the basic properties of GNPs, further discuss the recent progress in gold nanoparticles for cancer theranostics, with an additional concern about TME stimuli-responsive studies.

SERS-fluorescence-superresolution triple-mode nanoprobe based on surface enhanced Raman scattering and surface enhanced fluorescence

Multifunctional nanoprobes play important roles in cell imaging and sensing. Here, we present a novel optical nanoprobe based on surface enhanced Raman scattering (SERS) and surface enhanced fluorescence (SEF), which can realize the SERS-fluorescence and superresolution triple-mode imaging of cancer cells. Compared with other previously reported multifunctional nanoprobes, the proposed nanoprobe holds two exquisite properties. The first one is that, in addition to normal SERS and fluorescence imaging, the nanoprobe can also be used for single molecule localization microscopy (SMLM) imaging, which helps compensate for the diffraction limited spatial resolution of normal SERS and fluorescence imaging. The second one is that, other than simple fluorescence, SEF is used in the nanoprobe to produce a stronger signal for fluorescence imaging and, more importantly, better photo-switching for SMLM imaging. In the experiment, we optimized the structure of the nanoprobe to obtain the best SEF effect. With the optimal structure, the triple-mode imaging of a breast cancer cell line (SKBR3) is realized. Since such triple-mode imaging of cancer cells has never been achieved before, we believe that the presented nanoprobe holds great potential for cancer cell targeting or the investigation of cell-nanomaterial interactions.

Applications of near infrared and surface enhanced Raman scattering techniques in tumor imaging: A short review

Imaging technologies play a vital role in clinical oncology and have undergone massive growth over the past few decades. Research in the field of tumor imaging and biomedical diagnostics requires early detection of physiological alterations so as to provide curative treatment in real time. The objective of this review is to provide an insight about near infrared fluorescence (NIRF) and surface enhanced Raman scattering (SERS) imaging techniques that can be used to expand their capabilities for the early detection and diagnosis of cancer cells. Basic setup, principle and working of the instruments has been provided and common NIRF imaging agents as well as SERS tags are also discussed besides the analytical advantages/disadvantages of these techniques. This review can help researchers working in the field of molecular imaging to design cost effective fluorophores and SERS tags to overcome the limitations of both NIRF as well as SERS imaging technologies.

Breast Tumor Analysis Using Shifted-Excitation Raman Difference Spectroscopy (SERDS)

We used a shifted-excitation Raman difference spectroscopy method for the ex vivo classification of resected and formalin-fixed breast tissue samples as normal (healthy) tissue, fibroadenoma, or invasive carcinoma. We analyzed 8 tissue samples containing invasive carcinoma that were surrounded by normal tissue and 3 tissue samples with fibroadenoma only. We made various measurement sites on various tissue samples, in total 240 measurements for each type of tissue. Although the acquired raw spectra contain enough information to clearly differentiate between normal and tumor (fibroadenoma and invasive carcinoma) tissue, the differentiation between fibroadenoma and invasive carcinoma was possible only after the shifted-excitation Raman difference spectroscopy isolation of pure Raman spectra from the heavily fluorescence interfered raw spectra. We used 784 and 785 nm as excitation wavelengths for the shifted-excitation Raman difference spectroscopy method. The differences in the obtained pure Raman spectra are assigned to the different chemical compositions of normal breast tissue, fibroadenoma, and invasive breast carcinoma. Principal component analysis and linear discriminant analysis showed excellent classification results in the Raman shift range between 1000 and 1800 cm-1. Invasive breast carcinoma was identified with 99.15% sensitivity, and the absence of invasive carcinoma was identified with 90.40% specificity. Tumor tissue in tumor-containing tissue was identified with 100% sensitivity, and the absence of tumor in no-tumor containing tissue was identified with 100% specificity. As gold standard for the determination of the sensitivity and the specificity, we considered the conventional histopathological classification. In summary, shifted-excitation Raman difference spectroscopy could be potentially very useful to support histopathological diagnosis in breast pathology.

Ultrasensitive Detection of Protein with Wide Linear Dynamic Range Based on Core-Shell SERS Nanotags and Photonic Crystal Beads

Detection of proteins in a wide concentration range from fg mL^-1 to sub mg mL^-1 is a challenge in the high throughput analysis of precision medicine. Herein, we proposed a biosensor consisting of core-shell surface-enhanced Raman scattering (SERS) nanotags as labels and photonic crystal beads (PCBs) as carriers for ultrasensitive detection of proteins. In practice, Raman dyes (RDs) were embedded in the interface of gold core and silver shell in the bimetal nanoparticles to form SERS nanotags. It was found that the sensitivity was significantly improved due to the enhanced Raman signal by the coupling of the core-shell structure and linear dynamic range (LDR) was extended owing to the high surface to volume ratio of PCBs as well. In addition, we also demonstrated that the biosensor exhibited fine stability and low background, which has great application potential in the detection of protein biomarkers.

Microchemical Pen: An Open Microreactor for Region-Selective Surface Modification

Various micro surface-modification approaches including photolithography, dip-pen lithography and ink-jet systems have been developed and used to extend the functionalities of solid surfaces. While those approaches work in the "open space", push-pull systems which work in solutions have recently drawn considerable attention. However, the confining flows performed by push-pull systems have realized only the dispense process, while microscale, region-selective chemical reactions have remained unattainable. This study reports a microchemical pen that enables region-selective chemical reactions for the micro surface modification/patterning. The chemical pen is based on the principle of microfluidic laminar flows and the resulting mixing of reagents by the mutual diffusion. The tiny diffusion layer performs as the working region. This report represents the first demonstration of an open microreactor in which two different reagents react on a real solid sample. The multifunctional characteristics of the microchemical pen are confirmed by different types of reactions in many research areas, including inorganic chemistry, polymer science, electrochemistry and biological sample treatment.

Multiplexed Molecular Imaging of Fresh Tissue Surfaces Enabled by Convection-Enhanced Topical Staining with SERS-Coded Nanoparticles

There is a need for intraoperative imaging technologies to guide breast-conserving surgeries and to reduce the high rates of re-excision for patients in which residual tumor is found at the surgical margins during postoperative pathology analyses. Feasibility studies have shown that utilizing topically applied surface-enhanced Raman scattering (SERS) nanoparticles (NPs), in conjunction with the ratiometric imaging of targeted versus untargeted NPs, enables the rapid visualization of multiple cell-surface biomarkers of cancer that are overexpressed at the surfaces of freshly excised breast tissues. In order to reliably and rapidly perform multiplexed Raman-encoded molecular imaging of large numbers of biomarkers (with five or more NP flavors), an enhanced staining method has been developed in which tissue surfaces are cyclically dipped into an NP-staining solution and subjected to high-frequency mechanical vibration. This dipping and mechanical vibration (DMV) method promotes the convection of the SERS NPs at fresh tissue surfaces, which accelerates their binding to their respective biomarker targets. By utilizing a custom-developed device for automated DMV staining, this study demonstrates the ability to simultaneously image four cell-surface biomarkers of cancer at the surfaces of fresh human breast tissues with a mixture of five flavors of SERS NPs (four targeted and one untargeted control) topically applied for 5 min and imaged at a spatial resolution of 0.5 mm and a raster-scanned imaging rate of >5 cm2 min-1 .

Surgical Guidance via Multiplexed Molecular Imaging of Fresh Tissues Labeled with SERS-Coded Nanoparticles

The imaging of dysregulated cell-surface receptors (or biomarkers) is a potential means of identifying the presence of cancer with high sensitivity and specificity. However, due to heterogeneities in the expression of protein biomarkers in tumors, molecular imaging technologies should ideally be capable of visualizing a multiplexed panel of cancer biomarkers. Recently, surface-enhanced Raman-scattering (SERS) nanoparticles (NPs) have attracted wide interest due to their potential for sensitive and multiplexed biomarker detection. In this review, we focus on the most recent advances in tumor imaging using SERS-coded NPs. A brief introduction of the structure and optical properties of SERS NPs is provided, followed by a detailed discussion of key imaging issues such as the administration of NPs in tissue (topical versus systemic), the optical configuration and imaging approach of Raman imaging systems, spectral demultiplexing methods for quantifying NP concentrations, and the disambiguation of specific vs. nonspecific sources of contrast through ratiometric imaging of targeted and untargeted (control) NP pairs. Finally, future challenges and directions are briefly outlined.

Nanostructure-based surface-enhanced Raman scattering biosensors for nucleic acids and proteins

Detection of nucleic acid and protein targets related to human health and safety has attracted widespread attention. Surface-enhanced Raman scattering (SERS) is a powerful tool for biomarker detection because of its ultrahigh detection sensitivity and unique fingerprinting spectra. In this review, we first introduce the development of nanostructure-based SERS-active substrates and SERS nanotags, which greatly influence the performance of SERS biosensors. We then focus on recent advances in SERS biosensors for DNA, microRNA and protein determination, including label-free, labeled and multiplex analyses as well as in vivo imaging. Finally, the prospects and challenges of such nanostructure-based SERS biosensors are discussed.

Facile and sensitive detection of influenza viruses using SERS antibody probes

We report facile and sensitive influenza virus detection method using surface-enhanced Raman scattering antibody probes.

Utilising polymers to understand diseases: advanced molecular imaging agents

This review describes how the highly tuneable size, shape and chemical functionality of polymeric molecular imaging agents provides a means to intimately probe the various mechanisms behind disease formation and behaviour.