Abstract
Nanoparticles (NPs) are substances between 1 and 100 nm in size. They have been the subject of numerous studies because of their potential applications in a wide range of fields such as cosmetics, electronics, medicine, and food. For biological applications of nanoparticles, they are usually coated with a substance capable of preventing agglomeration of the nanoparticles and nonspecific binding and exhibiting water-solubility characteristics with specific immobilized (bio)molecules. In order to evaluate the chemical properties of the surface-modified nanoparticles for bioapplications, including drug delivery, a simple and reliable method for the analysis of the presence of the surface chemicals and the ligand states of the nanoparticles is necessary. In this study, the authors numerically evaluated the extent of polyethylene glycol (PEG) ligand conjugation on AuNPs by concurrently adopting a microliquid inkjet printing system for sampling of the PEGylated AuNPs solution and ToF-SIMS imaging together with statistical analysis. The statistical correlation values calculated from the signals of PEG and Au measured by ToF-SIMS imaging on the sample spots made by a microliquid inkjet printing system showed better reproducibility and improved correlation values compared to the pipet spotting. Their improved method will be useful to evaluate ligand-conjugated nanoparticles for quality control of each conjugation process.
Highlights
Nanoparticles (NPs) with surface modification with ligands have been widely used as carrier molecules in the fields of biomedicine such as internal/external diseases diagnosis and treatment, owing to such characteristics as biocompatibility and stability.1–4 Since nanoparticles generally have a high surface energy, organic ligands are introduced to control the attractive force between the nanoparticles that induces their aggregation
When it is in the form of a particle, a status of change in its surface can be indirectly estimated through localized surface plasmon resonance (LSPR)
When polyethylene glycol (PEG) is coated on citrate amounts of nanoparticles. Gold nanoparticles (AuNPs), an organic layer in thickness of several nm is formed on the surface so that the change of LSPR due to this can be observed by the UV-Vis, which appears as a redshift of the band
Summary
Nanoparticles (NPs) with surface modification with ligands have been widely used as carrier molecules in the fields of biomedicine such as internal/external diseases diagnosis and treatment, owing to such characteristics as biocompatibility and stability. Since nanoparticles generally have a high surface energy, organic ligands are introduced to control the attractive force between the nanoparticles that induces their aggregation. As it is capable of dispensing of a small volume of liquids, it requires less analyte solution and facilitates instantaneous drying, making the printed sample spots less vulnerable to the factors that can affect the result of the analysis such as physicochemical properties of nanoparticles, ligands, and substrates (i.e., hydrophobicity of silicon wafer surface) By utilizing this advantageous feature, we demonstrated that the free ligands existing in the nanoparticle solution must be removed thoroughly to effectively assess the surface modification status by measuring the AuNP samples from each gradual washing step for free ligand removal. By adopting a micro-liquid inkjet printing system, the reproducibility of the sampling was significantly improved, and this resulted in the enhancement of the correlation of the results of ToF-SIMS imaging This allowed assessment of the extent of free ligand removal and surface modification by analyzing the samples of each sampling step. It is expected that our method can be applied to the assessment of various nanoparticles
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