Click Chemistry for Drug Development and Diverse Chemical–Biology Applications

Surface-enhanced Raman spectroscopy (SERS) inherits the rich chemical fingerprint information on Raman spectroscopy and gains sensitivity by plasmon-enhanced excitation and scattering. In particular, most Raman peaks have a narrow width suitable for multiplex analysis, and the measurements can be conveniently made under ambient and aqueous conditions. These merits make SERS a very promising technique for studying complex biological systems, and SERS has attracted increasing interest in biorelated analysis. However, there are still great challenges that need to be addressed until it can be widely accepted by the biorelated communities, answer interesting biological questions, and solve fatal clinical problems. SERS applications in bioanalysis involve the complex interactions of plasmonic nanomaterials with biological systems and their environments. The reliability becomes the key issue of bioanalytical SERS in order to extract meaningful information from SERS data. This review provides a comprehensive over...

Surface-Enhanced Raman Spectroscopy for Bioanalysis: Reliability and Challenges

1.1. Significance of IVDs in the Clinic
IVD test is a crucial component of clinical care that performs a diagnostic test on biological samples that have been taken from a living body, such as blood, urine, and tissue.1 Such tests are usually performed to determine or confirm the presence of disease in an individual. “In vitro” literally means “within the glass”, which indicates that the test was historically conducted in glass test tubes. In contrast, in vivo tests, literally “within the living”, are conducted within a whole, living organism including human body.2 IVD tests have received much public attention because of their distinct features in the medical profession. First, IVD tests do not interact with the human body directly, making such diagnosis accessible without invasive surgeries and thus saving a great deal of suffering. Second, the procedures of IVDs are performed on samples rather than human body, avoiding the possible biological safety problems on patients that often take place in the in vivo diagnostics. Third, an IVD test can quickly provide valuable information on a patient’s healthcare conditions. On the basis of the information, physicians or patients are able to make a timely decision for patient care or treatment. Fourth, the application of IVDs enables early diagnosis and makes treatment of serious diseases easier. Generally, the cost of early testing is much lower than that of the later on extensive treatment. Last, IVDs play a particularly vital role in remote settings for managing outbreaks of acute infectious diseases, where effective but simple diagnostic systems are highly desirable. These features make IVDs unique and of great importance among medical technologies.

Gold Nanoparticles for In Vitro Diagnostics

Vibrational spectroscopy has been extensively applied to the study of molecules in gas phase, in condensed phase, and at interfaces. The transition from spectroscopy to spectroscopic imaging of living systems, which allows the spectrum of biomolecules to act as natural contrast, is opening new opportunities to reveal cellular machinery and to enable molecule-based diagnosis. Such a transition, however, involves more than a simple combination of spectrometry and microscopy. We review recent efforts that have pushed the boundary of the vibrational spectroscopic imaging field in terms of spectral acquisition speed, detection sensitivity, spatial resolution, and imaging depth. We further highlight recent applications in functional analysis of single cells and in label-free detection of diseases.

https://science.sciencemag.org/content/sci/350/6264/aaa8870.full.pdf

Vibrational spectroscopic imaging of living systems: An emerging platform for biology and medicine

The application of surface-enhanced Raman spectroscopy (SERS) in biological and biomedical detection schemes is feasible due to its excellent molecular specificity and high sensitivity as well as the capability of SERS to be performed in complex biological compositions. SERS-based investigation of cells, which are the basic structure and functional unit of organisms, represents the starting point of this review. It is demonstrated that SERS provides a deep understanding of living cells as well as their microenvironment which is needed to assess the development of diseases. The clinical relevance of SERS is proved by its application for the detection of cancer cells and tumour margins under in vivo conditions and examples for theranostic approaches are discussed. This review article provides a comprehensive overview of the recent progress within the last 3 years.

Recent progress in surface-enhanced Raman spectroscopy for biological and biomedical applications: from cells to clinics

Alkynes can be metabolically incorporated into biomolecules including nucleic acids, proteins, lipids, and glycans. In addition to the clickable chemical reactivity, alkynes possess a unique Raman scattering within the Raman-silent region of a cell. Coupling this spectroscopic signature with Raman microscopy yields a new imaging modality beyond fluorescence and label-free microscopies. The bioorthogonal Raman imaging of various biomolecules tagged with an alkyne by a state-of-the-art Raman imaging technique, stimulated Raman scattering (SRS) microscopy, is reported. This imaging method affords non-invasiveness, high sensitivity, and molec- ular specificity and therefore should find broad applications in live-cell imaging.

Live-Cell Stimulated Raman Scattering Imaging of Alkyne-Tagged Biomolecules**

National Instrumentation Program [2011YQ030124]; National Basic Research Program of China (973 Program) [2012CB917303]; National Natural Science Foundation of China [21172013]

A bioorthogonal Raman reporter strategy for SERS detection of glycans on live cells.

A cell-specific metabolic glycan labeling strategy has been developed using azidosugars encapsulated in ligand-targeted liposomes. The ligands are designed to bind specific cell-surface receptors that are only expressed or up-regulated in target cells, which mediates the intracellular delivery of azidosugars. The delivered azidosugars are metabolically incorporated into cell-surface glycans, which are then imaged via a bioorthogonal reaction.

Cell-selective metabolic glycan labeling based on ligand-targeted liposomes.

Proteins are the workhorses of the cell, playing crucial roles in virtually every biological process. The revolutionary ability to visualize and monitor proteins in living systems, which is largely the result of the development of green fluorescence protein (GFP) and its derivatives, has dramatically expanded our understanding of protein dynamics and function. Still, GFPs are ill suited in many circumstances; one major drawback is their relatively large size, which can significantly perturb the functions of the native proteins to which they are fused.To bridge this gap, scientists working at the chemistry–biology interface have developed methods to install bioorthogonal functional groups into proteins in living cells. The bioorthogonal group is, by definition, a non-native and nonperturbing chemical group. But more importantly, the installed bioorthogonal handle is able to react with a probe bearing a complementary functionality in a highly selective fashion and with the cell operating in its physiologica...

Introducing Bioorthogonal Functionalities into Proteins in Living Cells

Sialic acid analogues containing a unique chemical functionality or chemical reporter have been metabolically incorporated into sialylated glycans. This process, termed metabolic glycan labeling, has emerged as a powerful tool for studying sialylation as well as other types of glycosylation. Currently, this technique can install only a single functionality. Here we describe a strategy for dual labeling of sialylated glycans using a new class of bifunctional sialic acid analogues containing two distinct chemical reporters at the N-acyl and C9 positions. These bifunctional unnatural sialic acids were metabolically incorporated into cellular glycans, where the two chemical reporters exerted their distinct functions. This approach expands the capability of metabolic glycan labeling to probe sialylation and glycan–protein interactions.

/pdf/bifunctional-unnatural-sialic-acids-for-dual-metabolic-j57euyo4li.pdf

Senlian Hong

Papers

Live-Cell Stimulated Raman Scattering Imaging of Alkyne-Tagged Biomolecules**

A bioorthogonal Raman reporter strategy for SERS detection of glycans on live cells.

Cell-selective metabolic glycan labeling based on ligand-targeted liposomes.

Introducing Bioorthogonal Functionalities into Proteins in Living Cells

Bifunctional Unnatural Sialic Acids for Dual Metabolic Labeling of Cell-Surface Sialylated Glycans