X-ray photoelectron spectroscopy and transmission electron microscopy analysis of silver-coated gold nanorods designed for bionanotechnology applications

Portable SERS for salivary-based detection of oral pre-malignant lesions and carcinomas: a step toward clinical implementation

The rising incidence of oral cancer has emerged as a serious menace to our civilization. Modern dietary habits, lack of awareness, and delays in early detection are major contributing factors to the global spread of this issue. This work reports the promising findings for diagnostic accuracy of oral cancer in pre-malignant stages by analyzing surface enhanced Raman spectroscopy (SERS) profiles of different stages of oral cancer combined with multivariate analysis. Using 99 clinical samples from which 39 samples were from malignant stage, 28 from pre-malignant and 32 from healthy controls, SERS analysis was carried out by employing label-free silver nanorods as SERS substrates. The SERS spectra of malignant and pre-malignant samples manifest distinct peaks associated with varying concentrations of inorganic metabolites and proteins. Primarily, the elevated level of thiocyanate dominates the SERS spectra in malignant samples while antioxidants like uric acid, xanthine and hypoxanthine's are the key elements in the pre-malignant samples. A ratio-metric analysis of 2130 and 1435 cm-1 peak revealed that the pre-malignant lesions consistently lie between 2 and 3, whereas malignant samples have ratio greater than 3 due to higher intensity of thiocyanate peak. The multivariate analysis successfully separates between oral cancer positive and negative samples with a sensitivity and specificity of 93.5 and 92.7 % respectively. This study presents promising results for the early detection of oral cancer, which could assist clinicians in saving lives.

Gold Nanorod Substrate for Rat Fetal Neural Stem Cell Differentiation into Oligodendrocytes

Gold nanorods (AuNRs) have been proposed to promote stem cell differentiation in vitro and in vivo. In this study, we examined a particular type of AuNR in supporting the differentiation of rat fetal neural stem cells (NSCs) into oligodendrocytes (ODCs). AuNRs were synthesized according to the seed-mediated method resulting in nanorods with an aspect ratio of around 3 (~12 nm diameter, 36 nm length) and plasmon resonance at 520 and 780 nm, as confirmed by transmission electron microscopy (TEM) and UV-vis spectroscopy, respectively. A layer-by-layer approach was used to fabricate the AuNR substrate on the functionalized glass coverslips. NSCs were propagated for 10 days using fibroblast growth factor, platelet-derived growth-factor-supplemented culture media, and differentiated on an AuNR or poly-D-lysine (PDL)-coated surface using differentiation media containing triiodothyronine for three weeks. Results showed that NSCs survived better and differentiated faster on the AuNRs compared to the PDL surface. By week 1, almost all cells had differentiated on the AuNR substrate, whereas only ~60% differentiated on the PDL surface, with similar percentages of ODCs and astrocytes. This study indicates that functionalized AuNR substrate does promote NSC differentiation and could be a viable tool for tissue engineering to support the differentiation of stem cells.

Facile synthesis of Fe3O4@Au core-shell nanocomposite as a recyclable magnetic surface enhanced Raman scattering substrate for thiram detection

The Fe₃O₄@Au core-shell nanocomposites, as the multifunctional magnetic surface enhanced Raman scattering (SERS) substrates, were fabricated successfully by the seeds growth method based on the Fe₃O₄-Au core-satellite nanocomposites. The SERS properties of the Fe₃O₄-Au core-satellite nanocomposites and the Fe₃O₄@Au core-shell nanocomposites were compared using 4-aminothiophenol (4-ATP) as the probe molecule. It was found that Fe₃O₄@Au core-shell nanocomposites showed better SERS performance than Fe₃O₄-Au core-satellite nanocomposites. The Au shell provided an effectively large surface area for forming sufficient plasmonic hot spots and capturing target molecules. The integration of magnetic core and plasmonic Au nanocrystals endowed the Fe₃O₄@Au core-shell nanocomposites with highly efficient magnetic separation and enrichment ability and abundant interparticle hot spots. The Fe₃O₄@Au core-shell nanocomposites could be easily recycled because of the intrinsic magnetism of the Fe₃O₄ cores and had good reproducibility of the SERS signals. For practical application, the Fe₃O₄@Au core-shell nanocomposites were also used to detect thiram. There was a good linear relationship between the SERS signal intensity and the concentration of thiram from 1 × 10^-3 to 1 × 10^-8 M and the limit of detection was 7.69 × 10^-9 M. Moreover, residual thiram on apple peel was extracted and detected with a recovery rate range of 99.3%. The resulting substrate with high SERS activity, stability and strong magnetic responsivity makes the Fe₃O₄@Au core-shell nanocomposites a perfect choice for practical SERS detection applications.

Fabrication of gold-silver core-shell nanoparticles for performing as ultrabright SERS-nanotags inside human ovarian cancer cells

This paper presents the fabrication and characterization of new gold-silver core-shell nanoparticles labeled with para-mercaptobenzoic acid (4MBA) molecules and demonstrates their use as surface-enhanced Raman spectroscopy (SERS)-nanotags with ultra-bright traceability inside cells and ability to convey spectrally-coded information about the intracellular pH by means of SERS. Unlike previous reported studies, our fabrication procedure includes in the first step the synthesis of chitosan-coated gold nanoparticles as a seed material with subsequent growing of a silver shell. The bimetallic core-shell structure is revealed by transmission electron microscopy, high-angle annular dark field scanning transmission electron microscopy, energy-dispersive x-ray elemental mapping and the presence of two interacting localized surface plasmon resonance modes in UV-vis extinction spectrum. The high SERS activity and sensitivity of as fabricated 4MBA-chit-Au-AgNPs nano-constructs to different pH in solution is investigated under 532 and 633 nm laser lines excitation. Next, in view of future studies in cancer diagnosis, the in vitro antiproliferative effects of SERS-nanotags against human ovarian adenocarcinoma cells (NIH:OVCAR-3) are evaluated. The capacity to operate as bright SERS nanotags with precise localization at a single cell level as well as intracellular pH indicators is clearly demonstrated by performing cell imaging under scanning confocal Raman microscopy.

Functionalized gold nanorod nanocomposite system to modulate differentiation of human mesenchymal stem cells into neural-like progenitors

A 2D multifunctional nanocomposite system of gold nanorods (AuNRs) was developed. Gold nanorods were functionalized via polyethylene glycol with a terminal amine, and, were characterized using transmission and scanning electron microscopy, ultra violet-visible and X-ray photoelectron spectroscopy, and Zeta-potential. The system was cytocompatible to and maintained the integrity of Schwann cells. The neurogenic potential of adipose tissue - derived human mesenchymal stem cells (hMSCs) was evaluated in vitro. The expression pattern and localization of Vimentin confirmed the mesenchymal origin of cells and tracked morphological changes during differentiation. The expression patterns of S100β and glial fibrillary acidic protein (GFAP), were used as indicator for neural differentiation. Results suggested that this process was enhanced when the cells were seeded on the AuNRs compared to the tissue-culture surface. The present study indicates that the design and the surface properties of the AuNRs enhances neural differentiation of hMSCs and hence, would be beneficial for neural tissue engineering scaffolds.

Modifying Dendritic Cell Activation with Plasmonic Nano Vectors

Dendritic cells (DCs) can acquire, process, and present antigens to T-cells to induce an immune response. For this reason, targeting cancer antigens to DCs in order to cause an immune response against cancer is an emerging area of nanomedicine that has the potential to redefine the way certain cancers are treated. The use of plasmonically active silver-coated gold nanorods (henceforth referred to as plasmonic nano vectors (PNVs)) as potential carriers for DC tumor vaccines has not been presented before. Effective carriers must be able to be phagocytized by DCs, present low toxicity, and induce the maturation of DCs—an early indication of an immune response. When we treated DCs with the PNVs, we found that the cell viability of DCs was unaffected, up to 200 μg/ml. Additionally, the PNVs associated with the DCs as they were phagocytized and they were found to reside within intracellular compartments such as endosomes. More importantly, the PNVs were able to induce expression of surface markers indicative of DC activation and maturation, i.e. CD40, CD86, and MHC class II. These results provide the first evidence that PNVs are promising carriers for DC-based vaccines and warrant further investigating for clinical use.

Bimetallic gold core–silver shell nanorod performance for surface enhanced Raman spectroscopy

Plasmonic gold nanorods (AuNRs) coated with four different thickness silver shells (AuNR\Ags) were synthesized and tested for their efficiency in Surface Enhanced Raman Scattering (SERS) signal enhancement for biomedical applications.