Nanoparticle Conjugation

Nanoparticles, as versatile nanoscale platforms, exhibit tunable surface chemistry, high payload capacity, and tailorable biocompatibility. These properties enable transformative applications in biomedicine, diagnostics, catalysis, and sensing. Nanoparticle conjugation serves as a cornerstone technology for functionalizing nanomaterials by stably anchoring bioactive molecules (e.g., antibodies, proteins, peptides, nucleic acids, drugs, fluorescent dyes, targeting ligands) onto particle surfaces through physical or chemical strategies.

Core Objectives & Advantages

1.Functional Enhancement: Imparts novel bioactivity, targeting capabilities, catalytic functions, or optical properties.

2.Precision Targeting: Ligand conjugation (e.g., antibodies, folate, peptides) enables site-specific accumulation in diseased tissues (e.g., tumors).

3.Stability & Biocompatibility: PEGylation reduces opsonization, extends circulation time, and minimizes immunogenicity.

4.Multifunctionalization: Integrates targeting, imaging, and therapeutic agents into "all-in-one" theranostic platforms.

5.Controlled Drug Delivery: Achieves high loading efficiency and stimuli-responsive release (pH/enzyme/light-triggered).

6.Enhanced Diagnostics: Amplifies detection sensitivity via signal-enhancing properties (e.g., plasmonic scattering, fluorescence).

BOT Bioscience provides customized Nanoparticle Conjugation services, utilizing diverse nanomaterials (gold, silica, polymeric, magnetic NPs) to engineer stable bioconjugates for advanced applications.

Nanoparticle Conjugation Methods

I. Physical Adsorption

Relies on non-covalent interactions (electrostatic, hydrophobic, hydrogen bonding, or van der Waals forces) to attach biomolecules. This method operates under mild conditions without chemical modification, preserving biomolecule activity. However, its weak binding stability makes conjugates susceptible to dissociation in physiological environments, limiting applications requiring long-term integrity. Typical implementations include adsorption of DNA onto cationic polymer nanoparticles or hydrophobic drugs into lipid-based carriers.

II. Chemical Conjugation

1. EDC/NHS Covalent Binding

Utilizes carbodiimide chemistry where EDC activates surface carboxyl groups (-COOH), forming an unstable intermediate stabilized by NHS. This reactive ester subsequently binds to amine groups (-NH?) on biomolecules, creating stable amide bonds. The reaction occurs in aqueous buffers (pH 4.7¨C6.0) with minimal impact on protein function, though optimization is required to prevent side reactions or nanoparticle aggregation.

2. Maleimide-Thiol Conjugation

Exploits rapid, specific coupling between maleimide-activated nanoparticles and thiol-containing (-SH) biomolecules (e.g., cysteine residues in antibodies). The reaction forms irreversible thioether bonds at near-neutral pH (6.5¨C7.5) within minutes, enabling precise orientation control critical for antibody functionality. Limitations include potential thiol oxidation and mandatory free -SH group availability.

3. Click Chemistry

Employs bioorthogonal reactions between azide (-N?) and alkyne (-C¡ÔCH) groups, forming triazole linkages. Copper-catalyzed (CuAAC) versions offer fast kinetics, while copper-free alternatives (e.g., SPAAC) avoid cytotoxicity for in vivo applications. Both require pre-functionalization of nanoparticles and ligands but deliver near-quantitative yields with minimal byproducts.

4. Aldehyde-Amine Conjugation

Couples aldehyde-functionalized nanoparticles with amine-bearing ligands via Schiff base formation, stabilized by sodium borohydride reduction to secondary amines. This catalyst-free method suits glycoprotein conjugation but risks over-conjugation and requires careful pH control (7.0¨C9.0).

5. Biotin-Streptavidin System

Leverages ultra-high-affinity (Kd ~10?1? M), non-covalent binding between streptavidin-coated nanoparticles and biotinylated ligands. This approach withstands extreme pH/temperature/organic solvents and enables signal amplification, though the large streptavidin size (52 kDa) may cause steric hindrance.

Applications

Targeted Drug/Gene Delivery

In Vitro Diagnostics (ELISA, lateral flow assays, biosensors)

In Vivo Imaging (Fluorescence/MRI/CT/photoacoustic)

Cell Separation & Tracking (e.g., magnetic CTC isolation)

Theranostic Nanoplatforms

Catalysis & Enzyme Immobilization

Vaccine Development

Precision Customization

Multifunctional Conjugation

Quality Assurance