Dual-modal SERS/fluorescence AuNP probe for mitochondrial imaging

A novel SERS/fluorescent multimodal imaging probe for mitochondria has been synthesised using 12 nm diameter gold nanoparticles (AuNP) surface functionalised with a rhodamine thiol derivative ligand. The normal pH dependant acidic fluorescence of the rhodamine based ligand is inversed when conjugated with the AuNP and higher emission intensity is observed at basic pH. This switch correlates to a pKa at pH 6.62, which makes it an ideal candidate for a pH sensitive imaging probe in the biological range (6.5-7.4). The observed pH sensitivity when attached to the AuNP is thought to be due to the formation of a spirolactam ring on the ligand, going from positively charged (+18 mV) to negatively charged (-60 mV) as the pH is changed from acidic to basic. Additionally, conjugation of the ligand to the AuNP serves to enhance the Raman signal of the rhodamine ligand through Surface Enhanced Raman Scattering (SERS). Confocal microscopy has shown that the probe enters HEK293 (kidney), A2780 (ovarian cancer) and Min6 (pancreatic beta) cells within an hour and a half incubation time. The probe was shown to localise in the mitochondria, thus providing a novel pH dependent SERS/fluorescent multimodal imaging probe for mitochondria

Scaling laws for the 2d 8-state Potts model with Fixed Boundary Conditions

We study the effects of frozen boundaries in a Monte Carlo simulation near a first order phase transition. Recent theoretical analysis of the dynamics of first order phase transitions has enabled to state the scaling laws governing the critical regime of the transition. We check these new scaling laws performing a Monte Carlo simulation of the 2d, 8-state spin Potts model. In particular, our results support a pseudo-critical beta finite-size scaling of the form beta(infinity) + a/L + b/L^2, instead of beta(infinity) + c/L^d + d/L^{2d}. Moreover, our value for the latent heat is 0.294(11), which does not coincide with the latent heat analytically derived for the same model if periodic boundary conditions are assumed, which is 0.486358...Comment: 10 pages, 3 postscript figure

Glyconanoparticles for colorimetric bioassays

Carbohydrate molecules are involved in many of the cellular processes that are important for life. By combining the specific analyte targeting of carbohydrates with the multivalent structure and change of solution colour as a consequence of plasmonic interactions with the aggregation of metal nanoparticles, glyconanoparticles have been used extensively for the development of bioanalytical assays. The noble metals used to create the nanocore, the methodologies used to assemble the carbohydrates on the nanoparticle surface, the carbohydrate chosen for each specific target, the length of the tether that separates the carbohydrate from the nanocore and the density of carbohydrates on the surface all impact on the structural formation of metal based glyconanoparticles. This tutorial review highlights these key components, which directly impact on the selectivity and sensitivity of the developed bioassay, for the colorimetric detection of lectins, toxins and viruses

A Renewable and Ultrasensitive Electrochemiluminescence Immunosenor Based on Magnetic RuL@SiO2-Au∼RuL-Ab2 Sandwich-Type Nano-Immunocomplexes

An ultrasensitive and renewable electrochemiluminescence (ECL) immunosensor was developed for the detection of tumor markers by combining a newly designed trace tag and streptavidin-coated magnetic particles (SCMPs). The trace tag (RuL@SiO2-Au∼RuL-Ab2) was prepared by loading Ru(bpy)32+(RuL)-conjuged secondary antibodies (RuL-Ab2) on RuL@SiO2 (RuL-doped SiO2) doped Au (RuL@SiO2-Au). To fabricate the immunosensor, SCMPs were mixed with biotinylated AFP primary antibody (Biotin-Ab1), AFP, and RuL@SiO2-Au∼RuL-Ab2 complexes, then the resulting SCMP/Biotin-Ab1/AFP/RuL@SiO2-Au∼RuL-Ab2 (SBAR) sandwich-type immunocomplexes were absorbed on screen printed carbon electrode (SPCE) for detection. The immunocomplexes can be easily washed away from the surface of the SPCE when the magnetic field was removed, which made the immunosensor reusable. The present immunosensor showed a wide linear range of 0.05–100 ng mL−1 for detecting AFP, with a low detection limit of 0.02 ng mL−1 (defined as S/N = 3). The method takes advantage of three properties of the immunosensor: firstly, the RuL@SiO2-Au∼RuL-Ab2 composite exhibited dual amplification since SiO2 could load large amount of reporter molecules (RuL) for signal amplification. Gold particles could provide a large active surface to load more reporter molecules (RuL-Ab2). Accordingly, through the ECL response of RuL and tripropylamine (TPA), a strong ECL signal was obtained and an amplification analysis of protein interaction was achieved. Secondly, the sensor is renewable because the sandwich-type immunocomplexes can be readily absorbed or removed on the SPCE’s surface in a magnetic field. Thirdly, the SCMP modified probes can perform the rapid separation and purification of signal antibodies in a magnetic field. Thus, the present immunosensor can simultaneously realize separation, enrichment and determination. It showed potential application for the detection of AFP in human sera

Development of an Electrogenerated Chemiluminescence Biosensor using Carboxylic acid-functionalized MWCNT and Au Nanoparticles

A COOH-F-MWCNT-Nafion-Ru(bpy)32+-Au-ADH electrogenerated chemiluminescence (ECL) electrode using COOH-functionalized MWCNT (COOH-F-MWCNT) and Au nanoparticles synthesized by the radiation method was fabricated for ethanol sensing. A higher sensing efficiency for ethanol for the ECL biosensor prepared by PAAc-g-MWCNT was measured compared to that of the ECL biosensor prepared by PMAc-g-MWCNT, and purified MWCNT. Experimental parameters affecting ethanol detection were also examined in terms of pH and the content of PAAc-g-MWCNT in Nafion. Little interference of other compounds was observed for the assay of ethanol. Results suggest this ECL biosensor could be applied for ethanol detection in real samples

Polyamine ligand-mediated self-assembly of gold and silver nanoparticles into chainlike structures in aqueous solution: Towards new nanostructured chemosensors

We are grateful to the Scientific Association ProteoMass (Portugal) for financial support. C.N. thanks Xunta de Galicia (Spain) for her postdoctoral contract (I2C program).1D Nanochain formation: The binding ability of a polyamine molecular linker (L)2- bearing different functional groups, which favors the self-assembling of silver (AgNPs) and gold nano-particles (AuNPs) into 1D nanochains in aqueous solution was explored. UV/Vis spectrophotometry and TEM were used to determine time-dependent structural changes associated with these 1D structure formations. Sensing of Hg2+ using AgNPs@ (L) 2- and AuNPs@ (L)2- assemblies was also carried out in aqueous solution. © 2013 The Authors. Published by Wiley-VCH Verlag GmbH& Co. KGaA, Weinheim.publishersversionpublishe