Owing to their excellent multiplexing ability, high sensitivity, and large dynamic range, immunoassays using surface-enhanced Raman scattering (SERS) as the readout signal have found prosperous applications in fields such as disease diagnosis, environmental surveillance, and food safety supervision. Various ever-increasing demands have promoted SERS-based immunoassays from the classical sandwich-type ones to those integrated with fascinating automatic platforms (e.g., test strips and microfluidic chips). As recent years have witnessed impressive progress in SERS immunoassays, we try to comprehensively cover SERS-based immunoassays from their basic working principles to specific applications. Focusing on several basic elements in SERS immunoassays, typical structures of SERS nanoprobes, productive optical spectral encoding strategies, and popular immunoassay platforms are highlighted, followed by their representative biological applications in the last 5 years. Moreover, despite the vast advances achieved to date, SERS immunoassays still suffer from some annoying shortcomings. Thus, proposals on how to improve the SERS immunoassay performance are also discussed, as well as future challenges and perspectives, aiming to give brief and valid guidelines for choosing suitable platforms according to particular applications.

For a comprehensive understanding of cells or tissues, it is important to enable multiple studies under the controllable microenvironment of a chip. In this report, we present an integrated microfluidic cell culture platform in which endothelial cells (ECs) are under static conditions or exposed to a pulsatile and oscillatory shear stress. Through the integration of a microgap, self-contained flow loop, pneumatic pumps, and valves, the novel microfluidic chip achieved multiple functions: pulsatile and oscillatory fluid circulation, cell trapping, cell culture, the formation of ECs barrier, and adding shear stress on cells. After being introduced into the chip by gravity, the ECs arranged along the microgap with the help of hydrodynamic forces and grew in the microchannel for more than 7 days. The cells proliferated and migrated to form a barrier at the microgap to mimic the vessel wall, which separated the microenvironment into two compartments, microchannel and microchamber. An optimized pneumatic micropump was embedded to actuate flow circulation in a self-contained loop that induced a pulsatile and oscillatory shear stress at physiological levels on the ECs in the microchannel. All the analyses were performed under either static or dynamic conditions. The performance of the barrier was evaluated by the diffusion and distribution behaviors of fluorescently labeled albumin. The permeability of the barrier was comparable to that in traditional in vitro assays. The concentration gradients of the tracer formed in the microchamber can potentially be used to study cell polarization, migration and communications in the future. Additionally, the morphology and cytoskeleton of the ECs response to the pulsatile and oscillatory shear stress were analyzed. The microfluidic chip provided a multifunctional platform to enable comprehensive studies of blood vessels at the cell or tissue level.

We have found that the synthetic compound CC-5079 potently inhibits cancer cell growth in vitro and in vivo by a novel combination of molecular mechanisms. CC-5079 inhibits proliferation of cancer cell lines from various organs and tissues at nanomolar concentrations. Its IC 50 value ranges from 4.1 to 50 nmol/L. The effect of CC-5079 on cell growth is associated with cell cycle arrest in G 2 -M phase, increased phosphorylation of G 2 -M checkpoint proteins, and apoptosis. CC-5079 prevents polymerization of purified tubulin in a concentration-dependent manner in vitro and depolymerizes microtubules in cultured cancer cells. Our data indicate that CC-5079 inhibits cancer cell growth with a mechanism of action similar to that of other tubulin inhibitors. However, CC-5079 remains active against multidrug-resistant cancer cells unlike other tubulin-interacting drugs, such as Taxol and colchicine. Interestingly, CC-5079 also inhibits tumor necrosis factor-A (TNF-A) secretion from lipopolysaccharide-stimulated human peripheral blood mononuclear cells (IC 50 , 270 nmol/L). This inhibitory effect on TNF-A production is related to its inhibition of phosphodiesterase type 4 enzymatic activity. Moreover, in a mouse xenograft model using HCT-116 human colorectal tumor cells, CC-5079 significantly inhibits tumor growth in vivo. In conclusion, our data indicate that CC-5079 represents a new chemotype with novel mechanisms of action and that it has the potential to be developed for neoplastic and inflammatory disease therapy. (Cancer Res 2006; 66(2): 951-9)

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Isolating and in situ profiling the heterogeneous molecular phenotype of circulating tumor cells are of great significance for clinical cancer diagnosis and personalized therapy. Herein, an on-chip strategy is proposed that combines size-based microfluidic cell isolation with multiple spectrally orthogonal surface-enhanced Raman spectroscopy (SERS) analysis for in situ profiling of cell membrane proteins and identification of cancer subpopulations. With the developed microfluidic chip, tumor cells are sieved from blood on the basis of size discrepancy. To enable multiplex phenotypic analysis, three kinds of spectrally orthogonal SERS aptamer nanovectors are designed, providing individual cells with composite spectral signatures in accordance with surface protein expression. Next, to statistically demultiplex the complex SERS signature and profile the cellular proteomic phenotype, a revised classic least square algorithm is employed to obtain the 3D phenotypic information at single-cell resolution. Combined with categorization algorithm partial least square discriminate analysis, cells from different human breast cancer subtypes can be reliably classified with high sensitivity and selectivity. The results demonstrate that this platform can identify cancer subtypes with the spectral information correlated to the clinically relevant surface receptors, which holds great potential for clinical cancer diagnosis and precision medicine.