Aggregation Phenomena of Host and Guest upon the Loading of Dendritic Core-Multishell Nanoparticles with Solvatochromic Dyes

Abstract

We systematically assessed the loading behavior of core-multishell nanoparticles (CMS NPs) for the solvatochromic dyes Coumarin 153 and Nile Red and studied the influence of the guest and its concentration on CMS NP aggregation using steady state absorption and fluorescence spectroscopy and dynamic light scattering (DLS). These measurements revealed the strong fluorescence of dye-loaded CMS NPs and formation of nonemissive dye aggregates in the outer CMS layer at higher loading concentrations of Nile Red, whereas in the case of Coumarin 153, a new species with red-shifted absorption and blue-shifted emission appeared. Moreover, dye loading triggers an aggregation of CMS NPs which have a hydrodynamic radius of 8 nm, thereby leading to CMS aggregates with a radius of 100–120 nm. These results underline the need for systematic studies of the influence of the guest and its loading concentration on CMS NP size for cellular uptake and in vivo imaging studies and the rational design of CMS NPs with improved transport and targeting abilities.

Dendronized core-multishell nanocarriers for solubilization of guest molecules

“…To avoid any undesired effects that could occur due to the aqueous environment the samples were freeze-dried and redissolved in organic media. In a previous report we were able to show self-aggregation of NR in aqueous mPEG-terminated CMS nanocarrier solutions [22]. The obtained transport capacities are given in Table 1.…”

“…Analytical grade solvents and chemicals were purchased from Acros or Sigma Aldrich and used as received. Dry solvents were obtained from a MBraun SPSnanocarriers [19,22]. Depending on the guest concentration, CMS-mPEG nanocarriers with an initial radius of 8 nm formed defined aggregates with a hydrodynamic radius of around 100 nm size [22].…”

“…Dry solvents were obtained from a MBraun SPSnanocarriers [19,22]. Depending on the guest concentration, CMS-mPEG nanocarriers with an initial radius of 8 nm formed defined aggregates with a hydrodynamic radius of around 100 nm size [22]. These CMS nanocarriers were investigated for the in vivo targeting of a F9 teratocarcinoma tumor [23] and the modulation of the copper level in eukaryotic cells [24].…”

“…NR was either taken up into aggregates of CMS-mPEG nanocarriers [22] or taken up into unimolecular CMS nanocarriers where the outer shell consisted of grafted, hyperbranched PG [21]. Here, we want to systematically investigate the influence of a dendronized outer shell as opposed to one consisting of linear mPEG and study its influence on transport capacity and aggregation behavior of the CMS nanocarriers.…”

“…NR was chosen as a guest, because this dye has structural properties similar to some drug molecules, it has very low solubility in water, and its solubilization can be easily quantified by absorption spectroscopy. Furthermore, we have alreadye gained detailed insight on the behavior of NR in combination with CMS nanoparticles [22]. MTX is an antimetabolite and an antifolate drug, which is used for the treatment of cancer.…”