SERS-based detection of haptoglobin in ovarian cyst fluid as a point-of-care diagnostic assay for epithelial ovarian cancer.

PURPOSE: To evaluate haptoglobin (Hp) in ovarian cyst fluid as a diagnostic biomarker for epithelial ovarian cancers (EOCs) using surface-enhanced Raman spectroscopy (SERS)-based in vitro diagnostic assay for use in an intraoperative setting. METHODS: SERS-based method was used to detect and quantify Hp in archived ovarian cyst fluids collected from suspicious ovarian cysts and differentiate benign tumors from EOCs. The diagnostic performance of SERS-based assay was verified against the histopathology conclusions and compared with the results of CA125 test and frozen sections. RESULTS: Hp concentration present in the clinical cyst fluid measured by SERS was normalized to 3.3 mg/mL of standard Hp. Normalized mean values for patients with benign cysts were 0.65 (n=57) and malignant cysts were 1.85 (n=54), demonstrating a significantly (P<0.01) higher Hp in malignant samples. Verified against histology, Hp measurements using SERS had a sensitivity of 94% and specificity of 91%. Receiver operating characteristic curve analysis of SERS-based Hp measurements resulted in area under the curve of 0.966±0.03, establishing the robustness of the method. CA125 test on the same set of patients had a sensitivity of 85% and specificity of 90%, while frozen section analysis on 65 samples had 100% sensitivity and specificity. CONCLUSION: With a total execution time of <10 minutes and consistent performance across different stages of cancer, the SERS-based Hp detection assay can serve as a promising intra-operative EOC diagnostic test.

High nuclearity carbonyl clusters as near-IR contrast agents for photoacoustic in vivo imaging.

High nuclearity carbonyl clusters of ruthenium and osmium are found to exhibit good photoacoustic (PA) activity in the near-IR (NIR) region. Their potential as PA contrast agents for full body imaging has been demonstrated for the first time with mice; intravenous administration of the osmium carbonyl cluster Na2[Os10(µ6-C)(CO)24] afforded up to a four-fold enhancement of the PA signal in various tissues. The cluster exhibits low toxicity, high stability and superior PA stability compared to the clinically approved NIR dye, indocyanine green.

Rapid SERS monitoring of lipid-peroxidation-derived protein modifications in cells using photonic crystal fiber sensor.

We proposed a side channel photonic crystal fiber (SC-PCF) based Surface enhanced Raman spectroscopy (SERS) platform which is able to accurately monitor lipid peroxidation derived protein modifications in cells. This platform incorporates linoleamide alkyne (LAA), which is oxidized and subsequently modifies proteins in cells with alkyne functional group upon lipid peroxidation. By loading the side channel of SC-PCF with a mixture of gold nanoparticles and LAA treated cells, and subsequently measuring the interference-free alkyne Raman peak from these proteins in cells, strong SERS signal was obtained. The platform provides a method for the rapid monitoring of lipid peroxidation derived protein modification in cells.

Sensitive surface enhanced Raman scattering multiplexed detection of matrix metalloproteinase 2 and 7 cancer markers.

A surface enhanced Raman spectroscopy (SERS) based platform was developed for sensitive multiplexed detection of matrix metalloproteinases (MMP) (MMP-2 and MMP-7) with low limit of detection and high specificity. Detection is based on the virtue of enzymatic reaction where a peptide can be cleaved only by its corresponding enzyme. The platform comprises two components, a specialized SERS-based bimetallic-film-over-nanosphere (BMFON) substrate and gold nanoparticles (AuNPs). The two components were functionalized such that binding between the two would occur through biotin-avidin-biotin complexation. Binding is hindered by MMP peptide chains conjugated onto the surfaces of the substrate and AuNPs, and can be removed only by cleaving the peptide chains with corresponding enzymes. Since AuNP binding sites become free after the peptides are cleaved, the number of binding sites for AuNPs onto the substrate would increase. By tagging the AuNPs, concentrations of MMP-specific enzymes can be quantified through examining intensities of signature SERS peaks of the tags. This cleave-and-bind mechanism was first validated by individual detection and quantification of MMP-2 and MMP-7. The platform was demonstrated to be able to sensitively detect concentrations of specific enzymes ranging from 1 ng/mL to 40 µg/mL, with close correlation between SERS intensity and concentrations. Finally, the multiplexed detection of MMP-2 and MMP-7 was demonstrated. The multiplexity of this platform provides a robust way to analyze diseases associated with MMP-2 and MMP-7 enzymes. Our work can be further developed as a clinical diagnostic tool to detect other MMP proteinase in bio-fluids samples, widening the number of biomarkers needed to characterize diseases better.

Highly sensitive SERS detection and quantification of sialic acid on single cell using photonic-crystal fiber with gold nanoparticles.

An ultrasensitive surface enhanced Raman spectroscopy (SERS) based sensing platform was developed to detect the mean sialic acid level on the surface of single cell with sensitivity as low as 2 fmol. This platform adopted the use of an interference-free Raman tag, 4-(dihydroxyborophenyl) acetylene (DBA), which selectively binds to sialic acid on the cell membrane. By loading the side channel of a photonic crystal fiber with a mixture of gold nanoparticles and DBA-tagged HeLa cell, and subsequently propagating laser light through the central solid core, strong SERS signal was obtained. This SERS technique achieved accurate detection and quantification of concentration of sialic acid on a single cell, surpassing previously reported methods that required more than 10(5) cells. Moreover, this platform can be developed into a clinical diagnostic tool to potentially analyze sialic acid-related diseases such as tumor malignancy and metastasis in real-time.

A rapid and label-free SERS detection method for biomarkers in clinical biofluids.

A metal carbonyl-functionalized nanostructured substrate can be used in a rapid and simple assay for the detection of A1AT, a potential biomarker for bladder cancer, in clinical urine samples. The assay involves monitoring changes in the carbonyl stretching vibrations of the metal carbonyl via surface-enhanced Raman spectroscopy (SERS). These vibrations lie in the absorption spectral window of 1800-2200 cm(-1), which is free of any spectral interference from biomolecules.

In vitro toxicity and bioimaging studies of gold nanorods formulations coated with biofunctional thiol-PEG molecules and Pluronic block copolymers.

In this work, we investigated the cytotoxicity, colloidal stability and optical property of gold nanorods before and after functionalizing them with thiolated PEG and Pluronic triblock copolymer (PEO-PPO-PEO) molecules. The morphology of functionalized gold nanorods was characterized by UV-visible absorption spectroscopy, transmission electron microscopy, and dynamic light scattering. Solution phase synthesis of gold nanorods has remained the method of choice for obtaining varying shapes and aspect ratios of rod nanoparticles. This method typically involves the use of cetyltrimethylammonium bromide (CTAB) surfactants as directing agents to grow gold nanorods in the solution phase. The as-synthesized gold nanorods surfaces are terminated with CTAB molecules and this formulation gives rise to adverse toxicity in vitro and in vivo. To employ the gold nanorods for biological studies, it is important to eliminate or minimize the exposure of CTAB molecules from the gold nanorods surface to the local environment such as cells or tissues. Complete removal of CTAB molecules from the gold nanorods surface is unfeasible as this will render the gold nanorods structurally unstable, causing the aggregation of particles. Here, we investigate the individual use of thiolated PEG and PEO-PPO-PEO as capping agents to reduce the cytotoxicity of gold nanorods formulation, while maintaining the optical, colloidal, and structural properties of gold nanorods. We found that encapsulating gold nanorods with the thiolated PEG or PEO-PPO-PEO molecules guarantees the stability and biocompatibility of the nanoformulation. However, excessive use of these molecules during the passivation process leads to a reduction in the overall cell viability. We also demonstrate the use of the functionalized gold nanorods as scattering probes for dark-field imaging of cancer cells thereby demonstrating their biocompatibility. Our results offer a unique solution for the future development of safe scattering color probes for clinical applications such as the long term imaging of cells and tissues.

Engineering bioconjugated gold nanospheres and gold nanorods as label-free plasmon scattering probes for ultrasensitive multiplex dark-field imaging of cancer cells.

In this paper, we proposed the use of gold nanoparticles as plasmon scattering probes for dark-field multiplex imaging of live cancer cells. By carefully engineering the surfaces, aqueous dispersions of anti-EGFR antibody-conjugated gold nanospheres and gold nanorods are prepared. We demonstrated the receptor-mediated delivery of antibody conjugated gold nanospheres and gold nanorods into EGFR receptor-positive oral squamous cell carcinoma cell line by using darkfield microscopy technique. Our result suggests that gold nanospheres and gold nanorods formulations could provide up to 7 types of plasmon scattering probes based on their tunability range with a 100 nm spectral separation in absorption bands.