Fluorescent gold nanoclusters for efficient cancer cell targeting

Finding new cancer treatments based on novel drug delivery approaches is critically important.Gold nanoparticles (AuNPs) for use in drug delivery and cellular imaging were functionalized using a two-step synthesis method using modified carboxylic terminated alkane-thiols to attach fluorescent dyes (DAPI or pyNH 2) to the carboxylic ends of the thiolated AuNPs.The cellular cytotoxicity showed that the fluorescently labelled AuNPs were non-toxic at low concentrations.Confocal laser scanning microscopy (CLSM) showed an efficient internalization and uptake of AuNPs by T47D breast cancer cells within 1 hour of incubation.The fluorescence intensity increases over time for both conjugates.When conjugating DAPI with gold nanoparticles, the behaviour is quite different from free DAPI.TEM results showed the localization of AuNPs in the cytoplasm, the cell periphery and near the perinuclear region.The surface chemistry of AuNPs plays an important role in facilitating their cellular uptake as TEM images for conjugates containing DAPI show more AuNPs were internalized by the cells.These various forms of imaging give a clear insight into how these potential drug carriers interact with cells and are subsequently adsorbed into the cells.These are the core processes that will determine if the drug delivery approaches will ultimately be successful.

Biomimetic synthesis has become a promising green pathway to prepare nanomaterials. In this study, bovine serum albumin (BSA)-conjugated gold nanoclusters/nanoparticles were successfully synthesized in water at room temperature by a protein-directed, solution-phase, green synthetic method. The synthesized BSA-Au nanocomplexes have fluorescence emission (588 nm) of gold nanoclusters and surface plasmon resonance of gold nanoparticles. The BSA-Au nanocomplexes display non-cytotoxicity and excellent biocompatibility on MGC803 gastric cancer cells. After conjugation of folic acid molecules, the obtained BSA-Au nanocomplexes showed highly selective targeting for MGC803 cells and dual-modality dark-field and fluorescence imaging.

Bioconjugate Chemistry, 2021

For the past two decades, atomic gold nanoclusters (AuNCs, ultrasmall clusters of several to 100 gold atoms, having a total diameter of <2 nm) have emerged as promising agents in the diagnosis and treatment of cancer. Owing to their small size, significant quantization occurs to their conduction band, which leads to emergent photonic properties and the disappearance of the plasmonic responses observed in larger gold nanoparticles. For example, AuNCs exhibit native luminescent properties, which have been well-explored in the literature. Using proteins, peptides, or other biomolecules as structural scaffolds or capping ligands, required for the stabilization of AuNCs, improves their biocompatibility, while retaining their distinct optical properties. This paved the way for the use of AuNCs in fluorescent bioimaging, which later developed into multimodal imaging combined with computer tomography and magnetic resonance imaging as examples. The development of AuNC-based systems for diagnostic applications in cancer treatment was then made possible by employing active or passive tumor targeting strategies. Finally, the potential therapeutic applications of AuNCs are extensive, having been used as light-activated and radiotherapy agents, as well as nanocarriers for chemotherapeutic drugs, which can be bound to the capping ligand or directly to the AuNCs via different mechanisms. In this review, we present an overview of the diverse biomedical applications of AuNCs in terms of cancer imaging, therapy, and combinations thereof, as well as highlighting some additional applications relevant to biomedical research.

Nanoscale research letters, 2018

Gold nanoclusters (AuNCs) have been extensively applied as a fluorescent probe for biomedical applications in imaging, detection, and therapy due to their unique chemical and physical properties. Fluorescent probes of AuNCs have exhibited high compatibility, superior photostablility, and excellent water solubility which resulted in remarkable biomedical applications for long-term imaging, high-sensitivity detection, and target-specific treatment. Recently, great efforts have been made in the developments of AuNCs as the fluorescent probes for various biomedical applications. In this review, we have collected fluorescent AuNCs prepared by different ligands, including small molecules, polymers, and biomacromolecules, and highlighted current achievements of AuNCs in biomedical applications for imaging, detection, and therapy. According to these advances, we further provided conclusions of present challenges and future perspectives of AuNCs for fundamental investigations and practical b...

Nanotechnology, 2013

A facile approach to synthesize gold nanoclusters (Au NCs) with bluish green fluorescence using histidine as both reductant and capping agent was reported. The UV-visible absorption and photoluminescence spectra measurement was performed to explore its optical properties under different circumstances (preparing condition, temperature, pH, storing time). Then, MPA, a NIR organic dye, was conjugated to Au NCs (Au-MPA) for in vivo fluorescence imaging application. Low cytotoxicity and high affinity to tumor of this nanoprobe was proved at the cellular level, and its bio-distribution in normal nude mice and MCF-7 tumor-bearing mice was also investigated. Consequently, the results demonstrated the promising potential of the green Au NCs conjugated with NIR dye as nanoprobes in bioimaging and related fields.

Gold nanoparticles have immense potential for cancer diagnosis and therapy on acount of their light absorption and scattering. Conjugation of gold nanoparticles (AuNPs) to ligands specifically targeted to biomarkers on cancer cells allows molecular-specific imaging and detection of cancer. The development of smart AuNPs that can deliver therapeutics at a sustained rate directly to cancer cells may provide better efficacy and lower toxicity for treating cancer tumors. Using targeted nanoparticles to deliver chemotherapeutic agents in cancer therapy offers many advantages to improve drug/gene delivery and to overcome many problems associated with conventional chemotherapy. AuNPs efficiently convert the absorbed light into localized heat, which can be exploited for the selective laser photothermal therapy of cancer.

ACS Nano, 2014

Here we report the synthesis of PLGA/DOXO-core Au-branched shell nanostructures (BGNSHs) functionalized with a human serum albumin/indocyanine green/folic acid complex (HSA-ICG-FA) to configure a multifunctional nanotheranostic platform. First, branched gold nanoshells (BGNSHs) were obtained through a seeded-growth surfactant-less method. These BGNSHs were loaded during the synthetic process with the chemotherapeutic drug doxorubicin, a DNA intercalating agent and topoisomerase II inhibitior. In parallel, the fluorescent near-infrared (NIR) dye indocyanine green (ICG) was conjugated to the protein human serum albumin (HSA) by electrostatic and hydrophobic interactions. Subsequently, folic acid was covalently attached to the HSA-ICG complex. In this way, we created a protein complex with targeting specificity and fluorescent imaging capability. The resulting HSA-ICG-FA complex was adsorbed to the gold nanostructures surface (BGNSH-HSA-ICG-FA) in a straightforward incubation process thanks to the high affinity of HSA to gold surface.

Progress in Biomedical Optics and Imaging - Proceedings of SPIE, 2006

Advanced optical technologies for in vivo imaging e.g. OCT and confocal reflectance endomicroscopy while being able to image stromal morphology, are unable to image biomolecular changes associated with carcinogenesis. Furthermore, the contrast between neoplastic and normal tissues from such advanced optical technologies is often too low to be of any clinical value. Due to their favorable optical properties including their ability to resonantly scatter light at surface plasmon resonance to present potentially good contrast for reflectance-mode imaging, we aim to develop gold nanoparticles as optical contrast agents coupled with these optical imaging systems to perform cancer targeting bioimaging for early diagnosis of epithelial carcinoma. In this study, 20 nm gold nanoparticles were synthesized and conjugated with anti-EGFR (Epidermal Growth Factor Receptor). EGFR is a cell surface receptor biomarker that is highly expressed in majority of epithelial cancer compared to normal cells. The resulting anti-EGFR conjugated gold nanoparticles were allowed to interact with the nasopharyngeal carcinoma CNE2 cells in vitro. The exact localization of the gold bioconjugates on the cell surface EGFR receptors was investigated using confocal immunofluorescence microscopy. We have demonstrated that the binding and localization of the gold bioconjugates on the cell surface increased the reflectance and scattering properties of the CNE2 cells and provide good optical contrast for the cancer cells under confocal reflectance microscopy. Thus our study has demonstrated the potential of gold nanoparticles to target and illuminate cancer cells for bioimaging.

Acta Biochimica Indonesiana, 2022

Background: Metal nanoclusters (NCs) with outstanding structural and optical properties have been intensively validated for applications in nanomedicine and nanotechnology. Carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6) is overexpressed in many cancer cells. Objective: The gold nanoclusters conjugated with a single domain antibody targeting CEACAM6 of 2A3 (2A3-AuNCs) were synthesized for the inhibition of cancer cells. Methods: 2A3-AuNCs were prepared via a facile hydrothermal approach. The cell viability was measured by resazurin dye reduction assay. The cell death was analyzed by fluorescence imaging. Results: Structural and optical characterizations demonstrated the successful synthesis of 2A3-AuNCs with a roughly spherical shape and a size of 2.35 nm. The 2A3-AuNCs revealed a maximum fluorescence intensity at 350 nm with a fluorescence quantum yield of 4.0%. The cell viability assay indicated that 2A3-AuNCs could inhibit the growths of cancer cells with over...

ACS Nano, 2010

The targeted delivery of nanoparticles to solid tumors is one of the most important and challenging problems in cancer nanomedicine, but the detailed delivery mechanisms and design principles are still not well understood. Here we report quantitative tumor uptake studies for a class of elongated gold nanocrystals (called nanorods) that are covalently conjugated to tumor-targeting peptides. A major advantage in using gold as a "tracer" is that the accumulated gold in tumors and other organs can be quantitatively determined by elemental mass spectrometry (gold is not a natural element found in animals). Thus, colloidal gold nanorods are stabilized with a layer of polyethylene glycols (PEGs), and are conjugated to three different ligands: (i) a single-chain variable fragment (ScFv) peptide that recognizes the epidermal growth factor receptor (EGFR); (ii) an amino terminal fragment (ATF) peptide that recognizes the urokinase plasminogen activator receptor (uPAR); and (iii) a cyclic RGD peptide that recognizes the a v b 3 integrin receptor. Quantitative pharmacokinetic and biodistribution data show that these targeting ligands only marginally improve the total gold accumulation in xenograft tumor models in comparison with nontargeted controls, but their use could greatly alter the intracellular and extracellular nanoparticle distributions. When the gold nanorods are administered via intravenous injection, we also find that active molecular targeting of the tumor microenvironments (e.g., fibroblasts, macrophages, and vasculatures) does not significantly influence the tumor nanoparticle uptake. These results suggest that for photothermal cancer therapy, the preferred route of gold nanorod administration is intra-tumoral injection instead of intravenous injection.