Raman detection of localized transferrin-coated gold nanoparticles inside a single cell

Carbon capture and biocatalytic oxygen production of photosystem II from thylakoids and microalgae on nanobiomaterials

Enhanced carbon capture and oxygen production via water splitting was observed by controlling the plasmon-induced resonance energy transfer (PIRET) for photosystem II (PSII) in thylakoid extracts and spirulina assembled on gold nanoparticle (AuNP) dimer arrays. The two types of vertical (V) and horizontal (H) AuNP dimer arrays were uniformly inserted inside pore diameter-controlled templates. Based on the theoretical calculations, the longitudinal mode of the H AuNP dimer array was found to be sensitive to the nanogap distances between the two AuNPs in resonance with the absorption at P680 of the PSII. The longitudinal modes that interacted with P680 of PSII increased from the V to the H conformer. The optical properties from the H AuNP dimer array caused overlapping absorbance and photoluminescence with PSII, and the H AuNP dimer arrays exhibited a significant increase in carbon capture and oxygen generation rates in comparison with those of the bare PSII protein complex under light irradiation via the controlled PIRET process.

Uptake quantification of gold nanoparticles inside of cancer cells using high order image correlation spectroscopy

The application of gold nanoparticles (AuNPs) in cancer therapeutics and diagnostics has recently reached a clinical level. Functional use of the AuNP in theranostics first requires effective uptake into the cells, but accurate quantification of AuNPs cellular uptake in real-time is still a challenge due to the destructive nature of existing characterization methods. The optical imaging-based quantification method is highly desirable. Here, we propose the use of high-order image correlation spectroscopy (HICS) as an optical imaging-based nanoparticle quantification technique. Coupled with dark field microscopy (DFM), a non-destructive and easy quantification method could be achieved. We demonstrate HICS analysis on 80 nm AuNPs coated with cetyltrimethylammonium bromide (CTAB) uptake in HeLa cells to calculate the percentage of aggregate species (dimer) in the total uptake and their relative scattering quantum yield inside the cells, the details of which are not available with other quantification techniques. The total particle uptake kinetics measured were in a reasonable agreement with the literature.

Analytical methodology for studying cellular uptake, processing and localization of gold nanoparticles

Interactions of gold nanoparticles (AuNPs) with live cells are known to exert a great impact on their functions, including cell signalling, genomic, proteomic, and metabolomic processes. Modern analytical techniques applied to studying nanoparticle-cell interactions are to improve our understanding of the mode of action of AuNPs, which is essential for their approval in disease therapeutics. Such methods may vary depending on what step of particle internalization is in question, i.e., cellular uptake, intracellular transport (accompanying by changes in the chemical state), translocation to different cell compartments, interaction with relevant subcellular structures and localization. This review focuses on the implementation and critical assessment of advanced analytical methodologies to investigate the cellular processing of AuNPs. Also addressed is a sought-after issue of accounting in in-vitro studies for a chemical form in which the AuNPs enter the cell in vivo.

Apolipoprotein E3-mediated cellular uptake of reconstituted high-density lipoprotein bearing core 3, 10, or 17 nm hydrophobic gold nanoparticles

We have developed a high-density lipoprotein (HDL)-based platform for transport and delivery of hydrophobic gold nanoparticles (AuNPs). The ability of apolipoprotein E3 (apoE3) to act as a high-affinity ligand for the low-density lipoprotein receptor (LDLr) was exploited to gain entry of HDL with AuNPs into glioblastoma cells. AuNPs of 3, 10, and 17 nm diameter, the latter two synthesized by phase transfer process, were solubilized by integration with phospholipids and apoE3, yielding reconstituted HDL (rHDL) bearing AuNPs. Ultraviolet–visible spectra of rHDL-AuNP indicated the presence of stable particles with surface plasmon band at ~530 nm. Transmission electron microscopy (TEM) of rHDL-AuNP revealed roughly spherical particles with AuNPs embedded in the core. The rHDL-AuNP particles displayed robust binding to the LDLr and were internalized by receptor-mediated endocytosis in glioblastoma cells. Confocal microscopy confirmed cellular uptake of AuNPs in the endosomal–lysosomal compartments, while TEM revealed intracellular aggregated AuNPs. Cell viability assay demonstrated that >85% of cells were viable with rHDL-AuNP treatment of 0.1–100 μg/mL for 24 hours. These findings are significant since they offer an effective means of delivering AuNPs across the cell membrane, which is particularly relevant in tumor cells that overexpress LDLr.

Gold Nanoparticles in Single-Cell Analysis for Surface Enhanced Raman Scattering

The need for new therapeutic approaches in the treatment of challenging diseases such as cancer, which often consists of a highly heterogeneous and complex population of cells, brought up the idea of analyzing single cells. The development of novel techniques to analyze single cells has been intensively studied to fully understand specific alternations inducing abnormalities in cellular function. One of the techniques used for single cell analysis is surface-enhanced Raman spectroscopy (SERS) in which a noble metal nanoparticle is used to enhance Raman scattering. Due to its low toxicity and biocompatibility, gold nanoparticles (AuNPs) are commonly preferred as SERS substrates in single cell analysis. The intracellular uptake, localization and toxicity issues of AuNPs are the critical points for interpretation of data since the obtained SERS signals originate from molecules in close vicinity to AuNPs that are taken up by the cells. In this review, the AuNP-living cell interactions, cellular uptake and toxicity of AuNPs in relation to their physicochemical properties, and surface-enhanced Raman scattering from single cells are discussed.

Enhancing the antitumor effect of methotrexate in intro and in vivo by a novel targeted single-walled carbon nanohorn-based drug delivery system

The present research reports a smart multifunctional oxidized single-wall carbon nanohorns (oxSWNHs) drug delivery system (DDS) which could enhance the anti-tumor effect of methotrexate (MTX).

Note: Raman microspectroscopy integrated with fluorescence and dark field imaging

A Raman detection platform integrated with both fluorescence and dark field microscopes was built for in situ Raman detection with the assistance of fluorescence and dark field imaging to locate the target micro regions. Cells and organelles can be easily found via fluorescence imaging with labeling techniques. Besides, nano-sized particles could be observed and located by dark field microscopes. Therefore, comparing with the commercial Raman spectrometers, much more researches based on Raman spectroscopy could be carried out on this integrated Raman platform, especially in the fields of analyzing biological tissues and subwavelength samples.

Gold nanorod-assembled PEGylated graphene-oxide nanocomposites for photothermal cancer therapy

Gold nanorod-attached PEGylated graphene-oxide (AuNR-PEG-GO) nanocomposites were tested for a photothermal platform both in vitro and in vivo. Cytotoxicity of AuNR was reduced after encapsulation with PEG-GO along with the removal of cetyltrimethylammonium bromide (CTAB) from AuNR by HCl treatment. Cellular internalization of the CTAB-eliminated AuNR-PEG-GO nanocomposites was examined using dark-field microscopy (DFM), confocal Raman microscopy and transmission electron microscopy (TEM). To determine the photothermal effect of the AuNR-PEG-GO nanocomposites, A431 epidermoid carcinoma cells were irradiated with Xe-lamp light (60 W cm(-2)) for 5 min after treatment with the AuNR-PEG-GO nanocomposites for 24 h. Cell viability significantly decreased by ~40% when the AuNR-PEG-GO-encapsulated nanocomposites were irradiated with light as compared with the cells treated with only the AuNR-PEG-GO nanocomposites without any illumination. In vivo tumor experiments also indicated that HCl-treated AuNR-PEG-GO nanocomposites might efficiently reduce tumor volumes via photothermal processes. Our graphene and AuNR nanocomposites will be useful for an effective photothermal therapy.

Label-free Raman spectroscopy for accessing intracellular anticancer drug release on gold nanoparticles

We investigated glutathione (GSH)-induced purine or pyrimidine anticancer drug release on gold nanoparticle (AuNP) surfaces by means of label-free Raman spectroscopy. GSH-triggered releases of 6-thioguanine (6TG), gemcitabine (GEM), acycloguanosine (ACY), and fadrozole (FAD) were examined in a comparative way by means of surface-enhanced Raman scattering (SERS). The GSH-induced dissociation constant of GEM (or ACY/FAD) from AuNPs was estimated to be larger by more than 38 times than that of 6TG from the kinetic relationship. Tripeptide control experiments were presented to check the turn-off Raman signalling mechanism. Dark-field microscopy (DFM) and transmission electron microscopy (TEM) indicated the intracellular AuNP loads. After their cellular uptake, GEM, ACY, and FAD would not show SERS intensities as strong as 6TG. This may be due to easier release of GEM, ACY, and FAD than 6TG by intracellular reducing species including GSH. We observed fairly strong SERS signals of GEM and 6TG in cell culture media solution. Our CCK-8 cytotoxicity assay data support that 6TG-AuNPs did not exhibit a substantial decrease in cell viability presumably due to strong binding. Label-free confocal Raman spectroscopy can be utilized as an effective tool to access intracellular anticancer drug release.