Drug delivery using gold nanoparticles.

Modern nanotechnologies provide various possibilities for efficiently delivering drugs to biological targets. This review focuses on using functionalized gold nanoparticles (GNPs) as a drug delivery platform. Owing to their exceptional size and surface characteristics, GNPs are a perfect drug delivery vehicle for targeted and selective distribution.

Monitoring of optical properties of tumors during laser plasmon photothermal therapy.

We studied grafted tumors obtained by subcutaneous implantation of kidney cancer cells into male white rats. Gold nanorods with a plasmon resonance of about 800 nm were injected intratumorally for photothermal heating. Experimental irradiation of tumors was carried out percutaneously using a near-infrared diode laser.

Surface-enhanced Raman scattering from Au nanorods, nanotriangles, and nanostars with tuned plasmon resonances.

Electromagnetic theory predicts that the optimal value of the localized plasmon resonance (LPR) wavelength for the maximal SERS enhancement factor (EF) is half the sum of the laser and Raman wavelengths. For small Raman shifts, the theoretical EF scales as the fourth power of the local field. However, experimental data often disagree with these theoretical conclusions, leaving the question of choosing the optimal plasmon resonance for the maximal SERS signal unresolved.

Enhanced Antibacterial Activity of Novel Fluorescent Glutathione-Capped Ag Nanoclusters.

Ag nanomaterials are promising candidates for the discovery of next-generation antibiotics with a high antibacterial effect against multi-drug resistant strains. This paper reports a simple synthesis of novel water-soluble glutathione-capped silver nanoclusters (GSH-Ag NCs) with an enhanced antibacterial activity. According to thin layer chromatography (TLC), the synthesized GSH-Ag NCs are an individual fraction of the same composition without any impurities.

One-Shot Laser-Pulse Modification of Bare and Silica-Coated Gold Nanoparticles of Various Morphologies.

Gold nanoparticles are widely used in laser biomedical applications due to their favorable properties, mainly localized plasmon resonance. However, laser radiation can cause a change in the shape and size of plasmonic nanoparticles, thus resulting in an unwanted reduction of their photothermal and photodynamic efficiency due to a drastic alteration of optical properties. Most previously reported experiments were carried out with bulk colloids where different particles were irradiated by different numbers of laser pulses, thus making it difficult to accurately evaluate the laser power photomodification (PM) threshold.

Immunization of Mice with Gold Nanoparticles Conjugated to Thermostable Cancer Antigens Prevents the Development of Xenografted Tumors.

Gold nanoparticles as part of vaccines greatly increase antigen stability, antigen accumulation in the lymph nodes, and antigen uptake by antigen-presenting cells. The use of such particles as part of anticancer vaccines based on heat shock proteins to increase vaccine effectiveness is timely. We prepared and characterized nanoconjugates based on 15-nm gold nanoparticles and thermostable tumor antigens isolated from MH22a murine hepatoma cells.

Albumin-Based Nanocarriers for the Simultaneous Delivery of Antioxidant Gene and Phytochemical to Combat Oxidative Stress.

Human serum albumin (HSA) nanoparticles are promising biocompatible, nontoxic, and non-immunogenic platforms for biomedical applications such as bioimaging and drug and gene delivery. The development of nonviral gene delivery vectors is a great challenge for efficient and safe gene therapy. Sulforaphane (SF) can stimulate the expression of antioxidant genes activation of a nuclear transcription factor, the erythroid-2 related factor 2 (Nrf-2).

SERS and Indicator Paper Sensing of Hydrogen Peroxide Using Au@Ag Nanorods.

The detection of hydrogen peroxide and the control of its concentration are important tasks in the biological and chemical sciences. In this paper, we developed a simple and quantitative method for the non-enzymatic detection of HO based on the selective etching of Au@Ag nanorods with embedded Raman active molecules. The transfer of electrons between silver atoms and hydrogen peroxide enhances the oxidation reaction, and the Ag shell around the Au nanorod gradually dissolves.

Photothermal and Photodynamic Therapy of Tumors with Plasmonic Nanoparticles: Challenges and Prospects.

Cancer remains one of the leading causes of death in the world. For a number of neoplasms, the efficiency of conventional chemo- and radiation therapies is insufficient because of drug resistance and marked toxicity. Plasmonic photothermal therapy (PPT) using local hyperthermia induced by gold nanoparticles (AuNPs) has recently been extensively explored in tumor treatment.

Lateral Flow Immunoassay of SARS-CoV-2 Antigen with SERS-Based Registration: Development and Comparison with Traditional Immunoassays.

The current COVID-19 pandemic has increased the demand for pathogen detection methods that combine low detection limits with rapid results. Despite the significant progress in methods and devices for nucleic acid amplification, immunochemical methods are still preferred for mass testing without specialized laboratories and highly qualified personnel. The most widely used immunoassays are microplate enzyme-linked immunosorbent assay (ELISA) with photometric detection and lateral flow immunoassay (LFIA) with visual results assessment.

Improving SERS bioimaging of subcutaneous phantom in vivo with optical clearing.

Surface-enhanced Raman scattering (SERS) has proven to be a promising technique for different types of imaging including preoperative and intraoperative in vivo tumor visualization. However, the strong scattering of the turbid tissue limits its use in subcutaneous areas. In this article, we used an optical clearing technique to improve the SERS signal from a subcutaneous tumor phantom.

Multifunctional plasmonic gold nanostars for cancer diagnostic and therapeutic applications.

Gold nanostar (AuNSt) has gained great attention in bioimaging and cancer therapy due to their tunable surface plasmon resonance across the visible-near infrared range. Photothermal treatment and imaging capabilities including fluorescence lifetime imaging at two-photon excitation (TP-FLIM) and dark-field microscopic imaging are considered in this work. Two types of AuNSts having plasmon absorption peaks centred at 600 and 750 nm wavelength were synthesized and studied.

Metal-Specific Response of High-Resolution ICP-MS for Proteins Binding to Gold Nanoparticles in Human Serum.

Metalloproteins have many different functions such as storage and transport of proteins, enzymes, signal transduction proteins, etc. Herein, for a selection of gold nanoparticles differing in shape, size, charge, and surface modification, the binding behavior in human serum was assessed with respect to metal-containing proteins. Our results based on sector-field ICP-MS measurements and a simple calculation algorithm indicate the possible involvement of proteins, incorporating Cu and Fe, in the formation of the biomolecular layer around the particle surface.

Extinction, absorption, and scattering of light by plasmonic spheres embedded in an absorbing host medium.

Although the general Lorenz-Mie formalism for spheres in an absorbing host has been developed, no correct analytical expressions in the small-particle limit have been published so far. Here, we derive two sets of analytical expressions for the extinction, absorption, and far- and near-field scattering cross sections of small particles embedded in an absorbing host. One set is a modification of the electrostatic approximation (EA) for an absorbing host, whereas the other represents an improved electrostatic approximation (IEA) based on the generalized Lorenz-Mie theory and a new form of Mie coefficients for the internal field expansion.

Correction: A novel concept of two-component dielectric function for gold nanostars: theoretical modelling and experimental verification.

Correction for 'A novel concept of two-component dielectric function for gold nanostars: theoretical modelling and experimental verification' by Nikolai G. Khlebtsov et al., Nanoscale, 2020, 12, 19963-19981, DOI: 10.

Photostability of Contrast Agents for Photoacoustics: The Case of Gold Nanorods.

Plasmonic particles as gold nanorods have emerged as powerful contrast agents for critical applications as the photoacoustic imaging and photothermal ablation of cancer. However, their unique efficiency of photothermal conversion may turn into a practical disadvantage, and expose them to the risk of overheating and irreversible photodamage. Here, we outline the main ideas behind the technology of photoacoustic imaging and the use of relevant contrast agents, with a main focus on gold nanorods.

Surface-Enhanced Raman Scattering-Based Lateral-Flow Immunoassay.

Lateral flow immunoassays (LFIAs) have been developed and used in a wide range of applications, in point-of-care disease diagnoses, environmental safety, and food control. However, in its classical version, it has low sensitivity and can only perform semiquantitative detection, based on colorimetric signals. Over the past decade, surface-enhanced Raman scattering (SERS) tags have been developed in order to decrease the detection limit and enable the quantitative analysis of analytes.

A novel concept of two-component dielectric function for gold nanostars: theoretical modelling and experimental verification.

Rational design of AuNST morphology requires adequate computational models. The bulk dielectric function is not applicable to sharp nanostar spikes. We suggest a two-component dielectric function in which the nanostar core is treated as a bulk material, whereas the size-corrected dielectric function of the spikes is treated by a modified Coronado-Schatz model.

Advantages of Highly Spherical Gold Nanoparticles as Labels for Lateral Flow Immunoassay.

The use of lateral flow immunoassays (LFIAs) for rapid on-site testing is restricted by their relatively high limit of detection (LoD). One possible way to decrease the LoD is to optimize nanoparticle properties that are used as labels. We compare two types of Au nanoparticles: usual quasispherical gold nanoparticles (C-GNPs), obtained by the Turkevich-Frens method, and superspherical gold nanoparticles (S-GNPs), obtained by a progressive overgrowth technique.

Optically activated and interrogated plasmonic hydrogels for applications in wound healing.

We disclose the use of hybrid materials featuring Au/Ag core/shell nanorods in porous chitosan/polyvinyl alcohol scaffolds for applications in tissue engineering and wound healing. The combination of Au and Ag in a single construct provides synergistic opportunities for optical activation of functions as near infrared laser tissue bonding, and remote interrogation to return parameters of prognostic relevance in wound healing monitoring. In particular, the bimetallic component ensures optical tunability, enhanced shelf life and photothermal stability, serves as a reservoir of germicidal silver cations, and changes in near-infrared and visible color according to the environmental level of oxidative stress.

Impact of Kapitza resistance on the stability and efficiency of photoacoustic conversion from gold nanorods.

Plasmonic particles have been proposed for a broad variety of optical and hybrid applications, including the photothermal ablation and photoacoustic imaging of cancer, or their integration in photonic sensors. Here, we address the effect of thermal resistance at the gold-water interface, or Kapitza resistance, on the performance of photoacoustic conversion of gold nanorods. Our findings point to possible strategies for the optimization of plasmonic particles as contrast agents for imaging, or even as transducers for biosensing.

Petal-like Gap-Enhanced Raman Tags with Controllable Structures for High-Speed Raman Imaging.

Surface-enhanced Raman scattering (SERS) is widely used for and bioimaging applications. However, reproducible and controllable fabrication of SERS tags with high density of electromagnetic hot-spots is still challenging. We report an improved strategy for the synthesis of core/shell Raman tags with high density of hot-spots and high immobilization of reporter molecules.

Gap-enhanced Raman tags: fabrication, optical properties, and theranostic applications.

Gap-enhanced Raman tags (GERTs) are emerging probes of surface-enhanced Raman scattering (SERS) spectroscopy that have found promising analytical, bioimaging, and theranostic applications. Because of their internal location, Raman reporter molecules are protected from unwanted external environments and particle aggregation and demonstrate superior SERS responses owing to the strongly enhanced electromagnetic fields in the gaps between metal core-shell structures. In this review, we discuss recent progress in the synthesis, simulation, and experimental studies of the optical properties and biomedical applications of novel spherically symmetrical and anisotropic GERTs fabricated with common plasmonic metals-gold (Au) and silver (Ag).