Smart Shell‐by‐Shell Nanoparticles with Tunable Perylene Fluorescence in the Organic Interlayer

Abstract

A new series of shell‐by‐shell (SbS)‐functionalized Al2O3 nanoparticles (NPs) containing a perylene core in the organic interlayer as a fluorescence marker is introduced. Initially, the NPs were functionalized with both, a fluorescent perylene phosphonic acid derivative, together with the lipophilic hexadecylphosphonic acid or the fluorophilic (1 H,1 H,2 H,2H‐perfluorodecyl)phosphonic acid. The lipophilic first‐shell functionalized NPs were further implemented with amphiphiles built of aliphatic chains and polar head‐groups. However, the fluorophilic NPs were combined with amphiphiles consisting of fluorocarbon tails and polar head‐groups. Depending on the nature of the combined phosphonic acids and the amphiphiles, tuning of the perylene fluorescence can be accomplished due variations of supramolecular organization with the shell interface. Because the SbS‐functionalized NPs dispose excellent dispersibility in water and in biological media, two sorts of NPs with different surface properties were tested with respect to biological fluorescent imaging applications. Depending on the agglomeration of the NPs, the cellular uptake differs. The uptake of larger agglomerates is facilitated by endocytosis, whereas individualized NPs cross directly the cellular membrane. Also, the larger agglomerates were preferentially incorporated by all tested cells.

Tunable Composition of Mixed Self‐Assembled Shell‐by‐Shell Structures on Nanoparticle Surfaces

“…[ 20 ] Based on such SAMs, vesicle‐like structures (see Scheme ) can be formed with nanoparticles as template by building up a second layer through non‐covalent interactions to a shell‐by‐shell (SbS) system. [ 21–26 ] Such unique systems provide the opportunity to switch the polarity of core–shell nanoparticles for adjusted processing, [ 21 ] to prepare model bilayers for biological investigations [ 12 ] or to serve defined 2D‐pockets for catalysis, water purification or as drug delivery carriers. [ 27,28 ] Besides the interesting chemical structure and promising applications of such SbS systems, only few artificial examples of homogeneous composition are known.…”

“…[20] Based on such SAMs, vesicle-like structures (see Scheme 1) can be formed with nanoparticles as template by building up a second layer through non-covalent interactions to a shell-by-shell (SbS) system. [21][22][23][24][25][26] Such unique systems provide the opportunity to switch the polarity of core-shell nanoparticles for adjusted processing, [21] to prepare model bilayers The formation of mixed shell-by-shell (SbS) systems with tunable shell compositions is demonstrated by using molecular self-assembly driven by chemical recognition motifs. Aluminum oxide nanoparticles (AlOx-NPs) act as template surface for a self-assembled monolayer (SAM) of either partially fluorinated fluoroalkyl or alkyl chained phosphonic acid derivatives or defined stoichiometric mixtures of those.…”