Pseudocapacitive performance of phenothiazine functionalized graphene aerogel

This study utilizes light adsorbing molecule, phenothiazine (PTZ) to reduce graphene oxide (GO) and functionalize into PTZ-rGO aerogel (PTZ-rGO). The UV excited PTZ reduces GO via electron transfer while PTZ is simultaneously oxidized and functionalized onto rGO to produce PTZ-rGO aerogel. The optimum incorporation of PTZ on rGO sheets renders good electrochemical active surface area of 495.71 m2 g−1 and enhances the diffusion behavior up to 41.92%. This pseudocapacitive effect and the excellent surface property provide promising charge storage results of 235.5 F g−1 at 0.5 A g−1. Furthermore, the stable charge-discharge cycles with 92% capacitance retention after 10,000 cycles render it an excellent electrode material for supercapacitor fabrication

Bioorganometallic chemistry of osmium carbonyl clusters

Ph.DDOCTOR OF PHILOSOPH

Vibrational spectroscopy of metal carbonyls for bio-imaging and -sensing

Transition metal carbonyls exhibit strong CO absorptions in the 2200–1800 cm−1 region, which is free of interference from other functional groups. This feature has led to their applications in bio-imaging and -sensing, in particular through mid-IR, Raman and more recently, surface-enhanced Raman spectroscopy (SERS). Their use in mid-IR quantitative sensing based on vibrational intensities, and chemical sensing based on frequency shifts and vibrational lifetimes, is reviewed. Their development for Raman sensing following the breakthrough in SERS highlights the potential of coupling metal carbonyls to plasmonic nanostructures as novel optical materials for SERS-based bio-imaging and -sensing.ASTAR (Agency for Sci., Tech. and Research, S’pore)Accepted versio

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 mu g/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. (C)2015 Optical Society of Americ

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 mu g/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. (C)2015 Optical Society of Americ

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 mu g/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. (C)2015 Optical Society of Americ

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.ASTAR (Agency for Sci., Tech. and Research, S’pore)ASTAR (Agency for Sci., Tech. and Research, S’pore

Highly Efficient Blood Protein Analysis Using Membrane Purification Technique and Super-Hydrophobic SERS Platform for Precise Screening and Staging of Nasopharyngeal Carcinoma

Early screening and precise staging are crucial for reducing mortality in patients with nasopharyngeal carcinoma (NPC). This study aimed to assess the performance of blood protein surface-enhanced Raman scattering (SERS) spectroscopy, combined with deep learning, for the precise detection of NPC. A highly efficient protein SERS analysis, based on a membrane purification technique and super-hydrophobic platform, was developed and applied to blood samples from 1164 subjects, including 225 healthy volunteers, 120 stage I, 249 stage II, 291 stage III, and 279 stage IV NPC patients. The proteins were rapidly purified from only 10 µL of blood plasma using the membrane purification technique. Then, the super-hydrophobic platform was prepared to pre-concentrate tiny amounts of proteins by forming a uniform deposition to provide repeatable SERS spectra. A total of 1164 high-quality protein SERS spectra were rapidly collected using a self-developed macro-Raman system. A convolutional neural network-based deep-learning algorithm was used to classify the spectra. An accuracy of 100% was achieved for distinguishing between the healthy and NPC groups, and accuracies of 96%, 96%, 100%, and 100% were found for the differential classification among the four NPC stages. This study demonstrated the great promise of SERS- and deep-learning-based blood protein testing for rapid, non-invasive, and precise screening and staging of NPC

A Transition Metal Carbonyl Probe for Use in a Highly Specific and Sensitive SERS-Based Assay for Glucose

A triosmium carbonyl cluster–boronic acid conjugate is used as a secondary carbohydrate probe in a SERS-based assay. The assay does not require conjugation of the metal carbonyl probe to a SERS-active species, and it utilizes the CO stretching vibrations of the metal carbonyl, which lies in a silent region of the SERS spectrum (1800–2200 cm^–1), for quantification. High selectivity for glucose over fructose and galactose is obtained, and a human urine sample doped with glucose is detected accurately