Impact of Green Gold Nanoparticle Coating on Internalization, Trafficking, and Efficiency for Photothermal Therapy of Skin Cancer.

Skin cancer is a global health issue and mainly composed of melanoma and nonmelanoma cancers. For the first clinical proof of concept on humans, we decided to study good prognosis skin cancers, i.e., carcinoma basal cell. In UE, the first-line treatment remains surgical resection, healing most of the tumors, but presents aesthetic disadvantages with a high reoccurrence rate on exposed areas. Moreover, the therapeutic indications could extend to melanoma and metastasis, which is a different medical strategy that could combine this treatment. Indeed, patients with late-stage melanoma are in a therapeutic impasse, despite recent targeted and immunological therapies. Photothermal therapy using gold nanoparticles is the subject of many investigations due to their strong potential to treat cancers by physical, thermal destruction. We developed gold nanoparticles synthesized by green chemistry (gGNPs), using endemic plant extract from Reunion Island, which have previously showed their efficiency at a preclinical stage. Here, we demonstrate that these gGNPs are less cytotoxic than gold nanoparticles synthesized by Turkevich's method. Furthermore, our work describes the optimization of gGNP coating and stabilization, also taking into consideration the gGNP path in cells (endocytosis, intracellular trafficking, and exocytosis), their specificity toward cancerous cells, their cytotoxicity, and their in vivo efficiency. Finally, based on the metabolic switch of cancerous cells overexpressing Glut transporters in skin cancers, we demonstrated that glucose-stabilized gGNP (gGNP@G) enables a quick internalization, fourfold higher in cancerous cells in contrast to healthy cells with no side cytotoxicity, which is particularly relevant to target and treat cancer.

Assessment of antioxidant and dermoprotective activities of gold nanoparticles as safe cosmetic ingredient.

Hubertia ambavilla, an endemic plant originating from Reunion Island in the Indian Ocean, is traditionally used as an anti-inflammatory and in healing, both for internal and external use. Polyphenolic compounds from aqueous phase extractions can reduce metal salts into nanoparticles and stabilize them in one step. Although gold nanoparticles are well described in the literature as anti-ageing ingredients, the nanoparticles presented herein are novel and are synthesized using a green process. We demonstrate their efficiency as dermoprotective, free radical scavenger and antioxidant cosmetic ingredients. Comparison with common nanoparticles obtained by the Turkevich method clearly emphasizes the necessity to carefully screen the products used for nanoparticle coatings, as they play a major role in the biological properties of the product. Hubertia ambavilla mediated gold nanoparticles are non-toxic to human dermal fibroblasts, possess free radical scavenging potential, and protect against damage to fibroblast and dermal cells caused by ultraviolet A radiation.

The Prevailing Role of Hotspots in Plasmon-Enhanced Sum-Frequency Generation Spectroscopy.

The plasmonic amplification of nonlinear vibrational sum frequency spectroscopy (SFG) at the surfaces of gold nanoparticles is systematically investigated by tuning the incident visible wavelength. The SFG spectra of dodecanethiol-coated gold nanoparticles chemically deposited on silicon are recorded for 20 visible wavelengths. The vibrational intensities of thiol methyl stretches extracted from the experimental measurements vary with the visible color of the SFG process and show amplification by coupling to plasmon excitation. Because the enhancement is maximal in the orange-red region rather than in the green, as expected from the dipolar model for surface plasmon resonances, it is attributed mostly to hotspots created in particle multimers, in spite of their low surface densities. A simple model accounting for the longitudinal surface plasmons of multimers allows the recovery of the experimental spectral dispersion.

Gold nanoparticle-based localized surface plasmon immunosensor for staphylococcal enterotoxin A (SEA) detection.

We describe the engineering of stable gold nanoparticle (AuNP) bioconjugates for the detection of staphylococcal enterotoxin A (SEA) using localized surface plasmon resonance (LSPR). Two types of AuNP bioconjugates were prepared by covalently attaching anti-SEA antibody (Ab) or SEA to AuNPs. This was achieved by reacting Traut's reagent with lysine residues of both proteins to generate thiol groups that bind to gold atoms on the AuNP surface. These bioconjugates were characterized in-depth by absorption spectroscopy, cryo-transmission electron microscopy, dynamic light scattering, and zeta potential measurements. Their stability over time was assessed after 1 year storage in the refrigerator at 4 °C. Two formats of homogeneous binding assays were set up on the basis of monitoring of LSPR peak shifts resulting from the immunological reaction between the (i) immobilized antibody and free SEA, the direct assay, or (ii) immobilized SEA and free antibody, the competitive assay. In both formats, a correlation between the LSPR band shift and SEA concentration could be established. Though the competitive format did not meet the expected analytical performance, the direct format, the implementation of which was very simple, afforded a specific and sensitive response within a broad dynamic range-nanogram per milliliter to microgram per milliliter. The limit of detection (LOD) of SEA was estimated to equal 5 ng/mL, which was substantially lower than the LOD obtained using a quartz crystal microbalance. Moreover, the analytical performance of AuNP-Ab bioconjugate was preserved after 1 year of storage at 4 °C. Finally, the LSPR biosensor was successfully applied to the detection of SEA in milk samples. The homogeneous nanoplasmonic immunosensor described herein provides an attractive alternative for stable and reliable detection of SEA in the nanogram per milliliter range and offers a promising avenue for rapid, easy to implement, and sensitive biotoxin detection. Sensitive LSPR Biosensing of SEA in buffer and milk using stable AuNP-Antibody bioconjugates Graphical abstract.

Layer-by-layer generation of PEG-based regenerable immunosensing surfaces for small-sized analytes.

Small molecules (haptens) like pharmaceuticals or peptides can serve as targets for antibody binding in competitive immunoassay-based flow-through assays. In this work, a strategy for preparing polyethylene glycol (PEG) coatings for subsequent hapten immobilization on glass-type silica surfaces is presented and characterized in detail. Two substrates bearing terminal silanol groups were utilized, a glass slide and a silicon wafer. First, surfaces were thoroughly cleaned and pretreated to generate additional silanol groups. Then, a silane layer with terminal epoxy groups was created using 3-glycidyloxypropyltrimethoxysilane (GOPTS). Epoxy groups were used to bind a layer of diamino-poly(ethylene glycol) (DAPEG) with terminal amino groups. Finally, the low molecular weight compound diclofenac was bound to the surface to be used as model ligand for competitive biosensing of haptens. The elementary steps were characterized using atomic force microscopy (AFM), water contact angle measurement, grazing-angle attenuated total reflection (GA-ATR) FT-IR spectroscopy, and X-ray photoelectron spectroscopy (XPS). The data collected using these techniques have confirmed the successive grafting of the molecular species, evidencing, that homogeneous monolayers were created on the silica surfaces and validated the proposed mechanism of functionalization. The resulting surfaces were used to investigate polyclonal anti-diclofenac antibodies recognition and reversibility using quartz crystal microbalance with dissipation (QCM-D) measurements or an automated flow-through immunoassay with chemiluminescence (CL) read-out. For both techniques, recognition and reversibility of the antibody binding were observed. The stability of sensors over time was also assessed and no decrease in CL response was observed upon 14 days in aqueous solution. The herein presented strategy for surface functionalization can be used in the future as reproducible and reusable universal platform for hapten biosensors.