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Unexpected Changes in Functionality and Surface Coverage for Au Nanoparticle PEI Conjugates: Implications for
Tae Joon Cho1, John M Pettibone1, Justin M Gorham1
1Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States.
Langmuir : the ACS Journal of Surfaces and Colloids
|June 27, 2015
Summary
Polyethylenimine-conjugated gold nanoparticles (AuNP-PEI) show variable properties. Branched PEI (25 kDa) yielded stable conjugates, while linear PEI caused aggregation, highlighting the need for careful characterization in drug delivery applications.
Area of Science:
- Nanotechnology
- Materials Science
- Biomedical Engineering
Background:
- Cationic polyethylenimine conjugated gold nanoparticles (AuNP-PEI) are promising for drug delivery and studying nanoparticle-cell interactions.
- Existing literature shows inconsistencies in the reproducibility of AuNP-PEI physicochemical properties, colloidal stability, and efficacy.
- A systematic examination is needed to understand factors influencing AuNP-PEI characteristics.
Purpose of the Study:
- To systematically investigate the preparation, stability, and formation mechanism of PEI-conjugated gold nanoparticles (AuNP-PEI).
- To elucidate the influence of polyethylenimine (PEI) properties (molar mass, conformation) and citrate capping on AuNP-PEI characteristics.
- To address the knowledge gap regarding the role of citrate and PEI in determining conjugate stability and functionality.
Main Methods:
- Preparation of AuNP-PEI conjugates using citrate-capped gold nanoparticles (AuNPs) and varying PEI types.
- Characterization of conjugation mechanism using attenuated total reflectance FTIR and X-ray photoelectron spectroscopy.
- Assessment of colloidal stability across different media and correlation with residual citrate and PEI properties.
Main Results:
- Branched PEI (25 kDa) conjugates demonstrated superior colloidal stability compared to linear PEI (25 kDa), which induced agglomeration.
- Colloidal stability correlated with displaced citrate, indicating its role in conjugation and stability.
- An unexpected conversion of PEI amine groups to quaternary ammonium species was observed for 10 kDa branched conjugates, potentially catalyzed by the AuNP surface.
Conclusions:
- The physicochemical properties and colloidal stability of AuNP-PEI conjugates are highly dependent on PEI characteristics and preparation methods.
- Citrate plays a crucial role in the conjugation process and subsequent stability of AuNP-PEI.
- Understanding these factors is essential for reproducible synthesis and predictable biological performance of AuNP-PEI for drug delivery and biomedical applications.
