title: Orthogonal analysis of functional gold nanoparticles for biomedical applications.
abstract: We report a comprehensive strategy based on implementation of orthogonal measurement techniques to provide critical and verifiable material characteristics for functionalized gold nanoparticles (AuNPs) used in biomedical applications. Samples were analyzed before and after ≈50 months of cold storage (≈4 °C). Biomedical applications require long-term storage at cold temperatures, which could have an impact on AuNP therapeutics. Thiolated polyethylene glycol (SH-PEG)-conjugated AuNPs with different terminal groups (methyl-, carboxylic-, and amine-) were chosen as a model system due to their high relevancy in biomedical applications. Electrospray-differential mobility analysis, asymmetric-flow field flow fractionation, transmission electron microscopy, scanning electron microscopy, atomic force microscopy, inductively coupled plasma mass spectrometry, and small-angle X-ray scattering were employed to provide both complementary and orthogonal information on (1) particle size and size distribution, (2) particle concentrations, (3) molecular conjugation properties (i.e., conformation and surface packing density), and (4) colloidal stability. Results show that SH-PEGs were conjugated on the surface of AuNPs to form a brush-like polymer corona. The surface packing density of SH-PEG was ≈0.42 nm(-2) for the methyl-PEG-SH AuNPs, ≈0.26 nm(-2) for the amine-SH-PEG AuNPs, and ≈0.18 nm(-2) for the carboxylic-PEG-SH AuNPs before cold storage, approximately 10 % of its theoretical maximum value. The conformation of surface-bound SH-PEGs was then estimated to be in an intermediate state between brush-like and random-coiled, based on the measured thicknesses in liquid and in dry states. By analyzing the change in particle size distribution and number concentration in suspension following cold storage, the long term colloidal stability of AuNPs was shown to be significantly improved via functionalization with SH-PEG, especially in the case of methyl-PEG-SH and carboxylic-PEG-SH (i.e., we estimate that >80 % of SH-PEG5K remained on the surface of AuNPs during storage). The work described here provides a generic strategy to track and analyze the material properties of functional AuNPs intended for biomedical applications, and highlights the importance of a multi-technique analysis. The effects of long term storage on the physical state of the particles, and on the stability of the ligand-AuNP conjugates, are employed to demonstrate the capacity of this approach to address critical issues relevant to clinical applications.
authors.affiliation: Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA. dhtsai@mx.nthu.edu.tw.|Department of Chemical Engineering, National Tsing Hua University, Hsinchu, Taiwan, Republic of China. dhtsai@mx.nthu.edu.tw.
authors.forename: De-Hao
authors.initials: DH
authors.lastname: Tsai
authors.affiliation: Department of Chemical Engineering, National Tsing Hua University, Hsinchu, Taiwan, Republic of China.
authors.forename: Yi-Fu
authors.initials: YF
authors.lastname: Lu
authors.affiliation: Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA.
authors.forename: Frank W
authors.initials: FW
authors.lastname: DelRio
authors.affiliation: Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA.
authors.forename: Tae Joon
authors.initials: TJ
authors.lastname: Cho
authors.affiliation: Chemical Sciences Division, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA.
authors.forename: Suvajyoti
authors.initials: S
authors.lastname: Guha
authors.affiliation: Chemical Sciences Division, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA.|Departments of Chemical Engineering and Chemistry, University of Maryland, College Park, MD, 20740, USA.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Zachariah
authors.affiliation: Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA.
authors.forename: Fan
authors.initials: F
authors.lastname: Zhang
authors.affiliation: Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Allen
authors.affiliation: Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA. vince.hackley@nist.gov.
authors.forename: Vincent A
authors.initials: VA
authors.lastname: Hackley
mesh_terms: D000327:Adsorption; D000818:Animals; D003102:Colloids; D003287:Contrast Media / Q000737:chemistry; D004337:Drug Carriers / Q000737:chemistry; D031521:Fractionation, Field Flow; D006046:Gold / Q000737:chemistry*; D006801:Humans; D007700:Kinetics; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D010316:Particle Size; D011092:Polyethylene Glycols / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D003102:Colloids; D003287:Contrast Media; D004337:Drug Carriers; D013438:Sulfhydryl Compounds; D011092:Polyethylene Glycols; D006046:Gold
keywords: Nanoparticles; Nanotechnology, Interface; Surface analysis, Kinetics