Silver Nanoparticles Labeled Streptavidin

What is streptavidin?

Streptavidin is a protein originating from the soil bacterium Streptomyces avidinii. This bacterium is renowned for producing a range of secondary metabolites, including antibiotics. Streptavidin was discovered due to its remarkable affinity for biotin, a vital vitamin known as vitamin B7 or vitamin H, essential for numerous metabolic processes across all living organisms.

In its natural environment, Streptomyces avidinii plays a crucial role in degrading biotin, aiding the bacterium in outcompeting other microorganisms for scarce resources. The streptavidin protein binds biotin with extraordinary affinity and specificity, forming one of the strongest non-covalent interactions known in nature. This near-irreversible binding under physiological conditions makes streptavidin an invaluable tool for various biotechnological applications.

What is the Silver Nanoparticles Labeled Streptavidin?

Silver nanoparticles labeled with streptavidin involve the conjugation of silver nanoparticles (AgNPs) with the streptavidin protein. This pairing exploits the unique properties of both components: streptavidin's exceptional affinity for biotin and the distinctive physical, chemical, and optical characteristics of silver nanoparticles.

Silver nanoparticles are distinguished by their high surface area-to-volume ratio, customizable optical properties such as localized surface plasmon resonance (LSPR), and potent antimicrobial activity, making them highly versatile for applications in medical diagnostics, therapeutic treatments, and biotechnology.

Conjugating streptavidin with silver nanoparticles enables the development of highly sensitive and specific detection systems crucial for various assays, including immunoassays, biosensors, and molecular diagnostics requiring precise detection of biotinylated molecules. This process involves attaching streptavidin to the surface of silver nanoparticles while ensuring the accessibility of biotin-binding sites for effective interaction.

How to Use Silver Nanoparticles to Label Streptavidin?

The process of labeling streptavidin with silver nanoparticles involves several crucial steps aimed at ensuring the stability and functionality of the final conjugate, particularly preserving streptavidin's biotin-binding capability. Here is a comprehensive overview of the process:

1. Synthesis of Silver Nanoparticles

Silver nanoparticles are synthesized using various methods, with chemical reduction being a commonly employed technique due to its simplicity and efficiency. This method typically entails reducing a silver salt (such as silver nitrate) in the presence of a reducing agent (like sodium borohydride) and a stabilizing agent (such as citrate or polyvinylpyrrolidone).

2. Functionalization of Silver Nanoparticles

To facilitate the attachment of streptavidin to the silver nanoparticles, the surface of the nanoparticles needs to be functionalized. This can be achieved by modifying the surface with specific functional groups, such as carboxyl, amino, or thiol groups, which can form covalent bonds with the streptavidin protein.

One common approach is to coat the silver nanoparticles with a bifunctional linker molecule, such as 3-mercaptopropionic acid (MPA). MPA has a thiol group that binds strongly to the silver surface and a carboxyl group that can react with the amino groups on streptavidin through carbodiimide chemistry.

3. Conjugation of Streptavidin to Silver Nanoparticles

Once the silver nanoparticles are functionalized, the next step is to conjugate streptavidin to the nanoparticle surface. This involves activating the carboxyl groups on the functionalized nanoparticles using a carbodiimide crosslinker, such as N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC), in the presence of N-hydroxysuccinimide (NHS).

The activated carboxyl groups can then react with the amino groups on streptavidin to form stable amide bonds, resulting in the attachment of streptavidin to the nanoparticle surface. The reaction conditions, such as pH, temperature, and molar ratios, need to be carefully optimized to ensure efficient conjugation and to maintain the activity of streptavidin.

4. Purification and Characterization

After conjugation, the silver nanoparticles labeled streptavidin conjugates need to be purified to remove any unreacted streptavidin and other by-products. This can be achieved using techniques such as centrifugation, dialysis, or size-exclusion chromatography.

The final conjugates are then characterized to confirm the successful attachment of streptavidin and to assess their functionality. Techniques such as UV-Vis spectroscopy, dynamic light scattering (DLS), transmission electron microscopy (TEM), and biotin-binding assays can be used to evaluate the size, morphology, stability, and biotin-binding capability of the conjugates.

How Do Silver Nanoparticles Labeled Streptavidin Work?

Silver nanoparticles labeled streptavidin work by combining the biotin-binding properties of streptavidin with the unique optical and physical characteristics of silver nanoparticles. The fundamental principle is the high-affinity interaction between streptavidin and biotin, which is exploited in various applications for specific and sensitive detection of biotinylated molecules.

Biotin-Streptavidin Interaction: The biotin-streptavidin interaction is one of the strongest known non-covalent interactions, with a dissociation constant (Kd) in the femtomolar range. This means that once biotin binds to streptavidin, it is extremely unlikely to dissociate under physiological conditions. This strong affinity is the cornerstone of many biotechnological applications, as it provides a stable and specific binding mechanism.

Optical Properties of Silver Nanoparticles: Silver nanoparticles exhibit unique optical properties due to localized surface plasmon resonance (LSPR), which is the collective oscillation of conduction electrons in response to light. This phenomenon results in strong absorption and scattering of light at specific wavelengths, depending on the size, shape, and surrounding environment of the nanoparticles.

When streptavidin is labeled with silver nanoparticles, these optical properties can be harnessed for sensitive detection. For example, changes in the LSPR signal can be monitored upon binding of biotinylated molecules, allowing for the detection and quantification of these molecules with high sensitivity.

Signal Amplification: One of the key advantages of using silver nanoparticles labeled streptavidin is the potential for signal amplification. Due to their high surface area-to-volume ratio, silver nanoparticles can accommodate multiple streptavidin molecules on their surface, each capable of binding to a biotinylated target. This multivalency enhances the overall signal, making it possible to detect low concentrations of biotinylated molecules.

Mechanisms in Biosensing and Assays: In biosensing and assays, silver nanoparticles labeled streptavidin can be used in various formats, such as colorimetric, fluorescence, or electrochemical assays. In a colorimetric assay, for instance, the binding of biotinylated molecules to streptavidin-conjugated silver nanoparticles can lead to a visible color change, providing a simple and direct readout.

In fluorescence-based assays, silver nanoparticles can enhance the fluorescence signal of nearby fluorophores through a phenomenon known as metal-enhanced fluorescence (MEF). This enhancement can significantly improve the sensitivity and lower the detection limits of the assay.

Schematic representation of preparation of immunosensor array and trace tag, and detection strategy by linear-sweep stripping voltammetric analysis of Ag NPs on the immunosensor surface. (Lai G., et al., 2011)

Advantages of Silver Nanoparticles Labeled Streptavidin

The use of silver nanoparticles labeled streptavidin offers several advantages over traditional detection methods and other nanoparticle systems. These advantages include:

High Sensitivity and Specificity: The combination of the high-affinity biotin-streptavidin interaction with the unique optical properties of silver nanoparticles results in highly sensitive and specific detection systems. The strong binding affinity ensures minimal background noise and high signal-to-noise ratios, enabling the detection of low-abundance targets.

Signal Amplification: The large surface area of silver nanoparticles allows for the attachment of multiple streptavidin molecules, providing multiple binding sites for biotinylated targets. This multivalency leads to signal amplification, enhancing the overall sensitivity of the detection system.

Tunable Optical Properties: Silver nanoparticles can be synthesized with various sizes and shapes, allowing for the tuning of their optical properties to suit specific applications. This tunability enables the design of customized detection systems with optimal performance.

Versatility: Silver nanoparticles labeled streptavidin can be used in a wide range of applications, including immunoassays, biosensors, molecular diagnostics, and imaging. Their versatility makes them suitable for various platforms and detection formats, including colorimetric, fluorescence, and electrochemical assays.

Enhanced Stability: Streptavidin-conjugated silver nanoparticles exhibit enhanced stability compared to other nanoparticle systems. The strong binding affinity of streptavidin to biotin ensures that the conjugates remain stable under various conditions, including changes in pH, temperature, and ionic strength.

Applications of Silver Nanoparticles Labeled Streptavidin

The unique properties and advantages of silver nanoparticles labeled streptavidin make them suitable for a wide range of applications in biotechnology, diagnostics, and medical research. Some of the key applications include:

Immunoassays: Silver nanoparticles labeled streptavidin are widely used in immunoassays, where they serve as detection agents for biotinylated antibodies or antigens. These assays are employed for the detection and quantification of various biomolecules, including proteins, hormones, and pathogens, in clinical and research settings.

Biosensors: Biosensors utilizing silver nanoparticles labeled streptavidin offer high sensitivity and specificity for the detection of biotinylated targets. These biosensors can be used for the detection of various analytes, including nucleic acids, proteins, and small molecules, in environmental monitoring, food safety, and clinical diagnostics.

Molecular Diagnostics: In molecular diagnostics, silver nanoparticles labeled streptavidin are used for the detection of biotinylated DNA or RNA probes in hybridization assays. These assays are employed for the detection of genetic mutations, infectious diseases, and cancer biomarkers.

Imaging: Silver nanoparticles labeled streptavidin can be used in imaging applications, where their optical properties enable enhanced contrast and signal amplification. These applications include fluorescence microscopy, surface-enhanced Raman scattering (SERS), and photoacoustic imaging.

Drug Delivery: Silver nanoparticles labeled streptavidin can be used for targeted drug delivery, where biotinylated therapeutic agents are delivered to specific cells or tissues. The high affinity of the biotin-streptavidin interaction ensures precise targeting and efficient delivery of the therapeutic agents.

Schematic representation of (A) the preparation of Ab2-bio barcode AuNP probe, (B) the preparation of streptavidin functionalized AgNPs, and (C) the SIEP signal amplification strategy. (Lin D., et al., 2015)

Our Silver Nanoparticles Labeled Services

At BOC Sciences, we offer a comprehensive range of silver nanoparticles labeled services to meet the diverse needs of our clients. Our services include:

Custom Synthesis: We provide custom synthesis of silver nanoparticles labeled streptavidin, tailored to the specific requirements of our clients. Our team of experts can optimize the synthesis and conjugation process to ensure high-quality and reproducible results.

Functionalization and Conjugation: Our functionalization and conjugation services include the modification of silver nanoparticles with various functional groups and the attachment of streptavidin. We use advanced techniques and reagents to achieve efficient and stable conjugation, ensuring the functionality of the final product.

Characterization: We offer comprehensive characterization services to evaluate the size, morphology, stability, and biotin-binding capability of silver nanoparticles labeled streptavidin. Our state-of-the-art facilities and equipment enable accurate and reliable characterization.

Quality Control: Our rigorous quality control processes ensure that all our products meet the highest standards of quality and performance. We conduct thorough testing and validation to ensure the stability and functionality of our silver nanoparticles labeled streptavidin conjugates.

Technical Support: Our team of experienced scientists provides technical support and consultation services to assist our clients with their specific applications. We offer guidance on the optimal use of our products and help troubleshoot any issues that may arise.

Advantages of Choosing BOC Sciences

When you choose BOC Sciences for your silver nanoparticles labeled streptavidin needs, you benefit from our extensive expertise, advanced technology, and commitment to quality. Here are some of the advantages of working with us:

Expertise: Our team of scientists has extensive experience in the synthesis, functionalization, and conjugation of nanoparticles. We leverage our expertise to provide high-quality products and services that meet the specific needs of our clients.

Comprehensive Support: We provide comprehensive support and consultation services to assist our clients with their specific applications. Our team of experts is available to provide guidance and troubleshoot any issues that may arise.

Competitive Pricing: We offer competitive pricing for our silver nanoparticles labeled streptavidin services, ensuring that our clients receive high-quality products and services at affordable rates. Our flexible pricing options and packages are designed to meet the budgetary requirements of our clients.