Gold nanoparticles (AuNPs) are small pieces of gold, 1-100 nanometers in size. They are optically, electrically and chemically special particles with a small size and a high surface area-to-volume ratio. AuNPs are now employed extensively in medicine, electronics and environmental sciences. Because they can be manipulated in size, shape and surface chemistry, they’re extremely useful and flexible to work with both for research and for manufacturing.
Fig.1 Schematic diagram of single crystal gold nanoparticles (AuNP).
(Darweesh, Ruba S., et al., 2019)
Gold nanoparticles usually consist of a gold nucleus coated with a stabilizing layer of molecules or ligands. The gold core contains metallic gold atoms in a crystal. The stabilizing layer both deter aggregation and is functional by enabling further modification of the nanoparticle surface. Some standard stabilizers are citrate ions, thiol-based compounds and polymers that react with the gold surface through chemical attachment or electrostatic force.
The AuNPs are chemically stable because they are highly reduced and so do not oxidize in normal circumstances. In addition, gold’s surface chemistry makes it possible to attach biomolecules easily, and AuNPs were therefore a natural candidate for biological applications.
AuNPs have a reputation for their unusual physical, chemical and biological attributes, and their applications in everything from biomedicine to electronics are no exception. Here is a breakdown of their main properties:
Optical Properties
One signature of gold nanoparticles is the optical property called surface plasmon resonance (SPR). This happens because conduction electrons on the surface of the nanoparticle hum in unison with the electromagnetic field of the beam of light. That leaves a bright smudging and refraction of light that renders AuNPs red-to-blue. The hue depends on the nanoparticle size, shape and aggregation state. For instance, tiny spherical nanoparticles are usually ruby-red in color, and big or anisotropic ones like rods or stars are blue or purple. These optical properties render AuNPs indispensable in biosensing, imaging and photothermal treatments.
High Surface Area
Due to their nanoscale dimensions, AuNPs possess an exceptionally high surface area-to-volume ratio. This characteristic enhances their reactivity and facilitates efficient interactions with other molecules or surfaces. This property is particularly advantageous in catalysis, where the active sites on AuNPs are maximized, and in biomedical applications, where functionalization with biomolecules is crucial for targeted delivery and detection.
Biocompatibility
Gold is inherently biocompatible and generally non-toxic, a property that translates to AuNPs. Their compatibility with biological systems allows their use in drug delivery, imaging, and therapeutic applications without eliciting significant immune responses or toxicity. Moreover, the ability to functionalize AuNPs with ligands, peptides, or DNA enhances their specificity and efficacy in biological systems.
Chemical Stability
Gold nanoparticles exhibit remarkable chemical stability. Unlike many other metals, gold is highly resistant to oxidation and corrosion, even in harsh chemical environments. This stability ensures the long-term reliability and integrity of AuNP-based systems, particularly in biological and environmental applications where oxidative conditions are common.
Size and Shape Tunability
Another extraordinary feature of AuNPs is their tunable size and shape. By manipulating synthesis conditions such as temperature, pH, and the choice of reducing and capping agents, researchers can produce nanoparticles in various morphologies, including spheres, rods, cubes, and stars. Each morphology offers unique properties, such as altered SPR peaks or specific binding affinities, expanding the versatility of AuNPs for targeted applications.
The synthesis of gold nanoparticles is a critical area of study, as the methods employed significantly influence their properties, size, shape, and functionality. The primary approaches to synthesizing AuNPs can be categorized into chemical, physical, and biological methods, each with its advantages and limitations:
Chemical Reduction: The most common method, involving the reduction of gold salts (e.g., HAuCl4) using reducing agents like citrate or ascorbic acid. This method is simple, cost-effective, and allows control over particle size.
Seed-Mediated Growth: A two-step process where small gold seeds are first synthesized and then grown into larger particles by adding a growth solution containing gold ions and a mild reducing agent.
Physical Methods: Techniques like laser ablation or sputtering can produce AuNPs by breaking bulk gold into nanoscale particles. These methods avoid chemical reagents but require sophisticated equipment.
Biological Synthesis: Green synthesis methods utilize biological agents such as plant extracts, bacteria, or fungi to reduce gold salts. This eco-friendly approach reduces the use of toxic chemicals.
Advantages
Disadvantages
Gold nanoparticles have a broad spectrum of applications, including:
Targeting Tumor Cells: AuNPs can be conjugated with antibodies or peptides that specifically bind to tumor markers, ensuring precise targeting.
Photothermal Therapy (PTT): AuNPs absorb near-infrared light and convert it into heat, effectively destroying cancer cells while sparing healthy tissues. This non-invasive technique offers a high degree of control and minimal side effects.
Drug Delivery: AuNPs serve as carriers for anticancer drugs, enabling controlled release and reducing systemic toxicity. Their small size allows them to penetrate tumor tissues effectively.
Imaging and Diagnostics: AuNPs enhance contrast in imaging techniques like computed tomography (CT) and photoacoustic imaging, aiding in early cancer detection and treatment monitoring.
Combination Therapies: AuNPs can be integrated into multimodal treatment strategies, combining PTT, drug delivery, and imaging for comprehensive cancer management.
Gold nanoparticles play a pivotal role in advancing cancer therapy due to their unique properties:
Targeting Tumor Cells: AuNPs can be conjugated with antibodies or peptides that specifically bind to tumor markers, ensuring precise targeting.
Fig.2 Gold nanoparticles in cancer therapy. (Sztandera, Krzysztof, et al., 2018)Photothermal Therapy (PTT): AuNPs absorb near-infrared light and convert it into heat, effectively destroying cancer cells while sparing healthy tissues. This non-invasive technique offers a high degree of control and minimal side effects.
Drug Delivery: AuNPs serve as carriers for anticancer drugs, enabling controlled release and reducing systemic toxicity. Their small size allows them to penetrate tumor tissues effectively.
Imaging and Diagnostics: AuNPs enhance contrast in imaging techniques like computed tomography (CT) and photoacoustic imaging, aiding in early cancer detection and treatment monitoring.
Combination Therapies: AuNPs can be integrated into multimodal treatment strategies, combining PTT, drug delivery, and imaging for comprehensive cancer management.
BOC Sciences offers a wide range of gold nanoparticle products as well as customized products in different types and sizes to meet a variety of research and application needs. Below is the list of products we can provide, if you have more needs, please contact us to customize the synthesis of your gold nanoparticles.
| Product Type | Available Sizes | Price |
| Gold Nanospheres | 2 nm, 5 nm, 20 nm, 50 nm, 100 nm | Inquiry |
| Gold Nanoshells | 2 nm, 5 nm, 20 nm, 50 nm, 100 nm | Inquiry |
| Gold Nanorods | 2 nm, 5 nm, 20 nm, 50 nm, 100 nm | Inquiry |
| Silica-Shelled Gold Nanoparticles | 2 nm, 5 nm, 20 nm, 50 nm, 100 nm | Inquiry |
| Product Type | Price |
| Colloidal Gold Nanoparticles | Inquiry |
| Gold Coated Silica Nanoparticles | Inquiry |
| Amine Functionalized Gold Nanoparticles | Inquiry |
| Biotinylated Gold Nanoparticles | Inquiry |
| Magnetic Gold Nanoparticles | Inquiry |
| PEG Coated Gold Nanoparticles | Inquiry |
| Thiol Gold Nanoparticles | Inquiry |
| Citrate Capped Gold Nanoparticles | Inquiry |
Gold nanoparticles appear red due to localized surface plasmon resonance (LSPR), where free electrons resonate with light, absorbing blue-green wavelengths and scattering red.
Gold nanoparticles are typically made by reducing chloroauric acid (HAuCl4) with reducing agents like sodium citrate, producing gold atoms that nucleate and grow into nanoparticles.
Gold nanoparticles treat cancer via photothermal therapy, where they absorb near-infrared light, converting it into heat to destroy cancer cells without harming surrounding tissues.
Gold nanoparticles interact with light, heat, or biomolecules through their unique optical, electronic, and surface properties, enabling applications in imaging, diagnostics, and targeted drug delivery.
Gold nanoparticles offer biocompatibility, stability, tunable size, and surface functionality, making them ideal for drug delivery, imaging, biosensors, and cancer therapy.
Gold nanoparticles change color with size due to shifts in their LSPR frequency, as particle size and shape affect light absorption and scattering properties.
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