Nanoobjects formed by ionic PAMAM dendrimers: hydrophilic/lipophilic modulation and encapsulation properties

Abstract

In this paper, we present the preparation and properties of some ionic PAMAM derivatives, which combine hydrophilic and lipophilic carboxylic acid chains as counter-ions for all protonable inner and outer amino groups. The amphiphilic nature of the final ionic codendrimers and, hence, their self-assembling features can be modulated by using different ratios between hydrophilic and lipophilic chains. In the bulk, these new materials self-organize into smectic A liquid crystal phases. In water, they self-assemble into different types of nano-objects depending on the molecular composition. The study of the morphology of these nano-structures, their cytotoxicity and their capability to encapsulate a lipophilic anticancer drug are reported herein. Some of these nanoobjects are non-cytotoxic and present good drug trapping ability, which make them interesting nanocarriers for applications in nanotechnology and biomedicine.

Design, synthesis and structure of novel G-2 melamine-based dendrimers incorporating 4-(n-octyloxy)aniline as a peripheral unit

“…As a consequence of the triple ionisation of the carboxyl groups in tripodal melamines C1 and C3 , only a remote upfield shift of their 1 H δ NH values was observed: from 9.47 ppm (in C1 , [ 42 ]) to 8.93 ppm (in the tris-anion of 8 ) and from 8.95 ppm (in C3 , [ 42 ]) to 8.70 ppm (in the tris-anion of 9 ) ( Table 3 ). A different diagnosis, based on aliphatic carboxyl group ionisation thus promoting 1 H shielding of proximal (α and β) methylene protons, was reported in the case of some G-2 PAMAM ionic dendrimers obtained by –COOH/H 2 N– neutralisation (NMR solvent, CDCl 3 ) [ 63 ].…”

“… a Downfield shifted resonances (Δδ as +0.25 and +0.33 ppm) of α-CH 2 protons to –NH 3 + group were reported in the case of some G-2 PAMAM dendrimers obtained by –COOH/H 2 N– neutralisation (CDCl 3 ) [ 63 ]. …”

“…To conclude, except the well-documented deshielding promoted by the magnetic anisotropy of π-delocalised systems, such as s -triazines and amides [ 64 ], no such vicinal effect created by a quaternary EWG of type >N sp3 H 2 + [ 63 ] was detected in the piperazine P-1 linker of compounds 7b , 8 and 9 , even in the case of the strongest proton donor, the trimesic acid (p K a = 3.12, 3.89 and 4.70).…”

“…On the IR timescale ( Fig. 4 –d), the comparative spectra of compounds 7a / 7b , 7b /trimesic acid, 8 / C1 and 9/C3 fully proved the presence of only the tris-carboxylate anions [ 63 , 65 – 66 ].…”

Solvent effects on the properties of hyperbranched polythiophenes

“…Since their discovery in the late 70's, [1][2][3] the research interest for dendrimers, which are virtually monodisperse hyperbranched macromolecules, has gained an increasing interest because of their broad range of applications in, for example, supramolecular chemistry, [4][5][6] self-assembly processes, [7][8][9] anticancer therapies [10][11][12] and diagnostic imaging. [13][14][15] The structure of dendrimers is divided into three distinct regions: the core, branched repeat units emanating from this core, and end-groups of the outer layer of repeat units (Figure 1a).…”