Synthesis and NMR characterization of dendrimers based on 2, 2-bis-(hydroxymethyl)-propanoic acid (bis-HMPA) containing peripheral amino acid residues for gene transfection

Abstract

Dendrimers, the emerging man made, highly branched, star-shaped macromolecules with nanometerscale dimensions are well known for their well defined and high controlled architecture, their versatility and high functionality and are of eminent interest in nanomedical applications such as drug delivery, gene transfection, and imaging. In this paper, versatile protocols for the synthesis of polyester-based, hydrolysable, polycationic dendrimers have been setup. A fourth generation dendrimer equipped with 48 peripheral hydroxyl groups was prepared from 2,2-bis(hydroxymethyl)propanoic acid and was used for grafting BOC-amino acids or as "hypercores" on which dendrons functionalized with BOC-amino acids were attached. A library of 15 polycationic homo-and hetero-dendrimers in the form of hydrochloride was obtained. Their structures and composition were confirmed by NMR analysis and by experimental molecular weight computed by volumetric titration. Their buffer capacity and results obtained from cytotoxicity assays and tests of binding with both pDNA and siRNA were very satisfactory. Keywords:Polyester-based polycationic dendrimers; 2, 2-bis(hydroxymethyl)propanoic acid; amino acids; pDNA and siRNA binding; buffer capacity.

Synthesis and characterization of versatile amphiphilic dendrimers peripherally decorated with positively charged amino acids

“…To complete the characterization of the prepared cationic dendrimers, having further confirmation of their composition on the periphery and to determine their molecular weight without having to resort to routine well‐known but very expensive techniques like matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry, the titration of amine hydrochlorides with HClO 4 solutions in AcOH in the presence of mercuric acetate and quinaldine red as indicator proved simple and affordable. The accuracy of this method, already adopted by us to determine the molecular weight of cationic amino acid‐modified dendrimers previously prepared was secured by a sharp endpoint of titration, while its reliability has been demonstrated by the reproducibility of the results. Table shows the estimated peripheral composition of each prepared dendrimer, the N value and the molecular weight estimated by NMR spectra compared with the observed experimental values obtained from volumetric titration ( N (degree of freedom) = 5).…”

“…For the construction of dendrimer architectures of this work, as core molecules, besides the trifunctional 2,2‐bis(hydroxymethyl)propan‐1‐ol ( 1 ), a novel tetrafunctional ‘kernel’, 2,2‐bis(hydroxymethyl)‐1,3‐propanediol ( 2 ) (Fig. ), was adopted and as a further innovation a hydrocarbon chain, provided by the biocompatible stearic acid, was directly inserted by esterification reaction of one of the hydroxyls.…”

Synthesis and characterization of fourth generation polyester‐based dendrimers with cationic amino acids‐modified crown as promising water soluble biomedical devices

“…The accuracy of this method, already adopted by us to determine molecular weight of cationic amino acids-modified dendrimers previously prepared, 59,60,63 was secured by a sharp endpoint of titration, while its reliability has been demonstrated by the reproducibility of results. Table 2 shows the estimated peripheral composition of dendrimers prepared, the N value, and the molecular weight estimated by NMR spectra compared with the experimental one obtained from volumetric titrations [N (degree of freedom) = 5].…”

“…As other target, the aimed materials had to have a better hydrophilic lipophilic balance than the last prepared ones, ie, a limited number of not functionalized residual peripheral hydroxyls. So, in this paper, two successful, versatile, and reproducible procedures to introduce onto a 48 hydroxyls dendrimer scaffold of fourth generation (G4OH) 1 , a mixture of L‐arginine (Arg), L‐lysine (Lys), N,N′‐ dimethylglycine (DMG), and N‐ methylglycine (MG) was set up, described, and discussed. The peripheral composition of the obtained amino acids‐modified dendrimers was respectful of the designed ones, and one or none free residual OH group remained not esterified.…”

Tert‐Butoxycarbonyl Protecting Group Location Induces Different Reactive Behaviors in the Five Possible Isoforms of Tri‐Boc‐Arginine

“…For example, arginine‐rich hyperbranched polymers shown significant enhancement of their transfection efficiency and lower toxicity in COS‐7 cells in dependence of the polymer content of arginine, under all the studied conditions . Our research line aims at preparing non‐cytotoxic polyester dendrimer matrices based on 2,2‐bis‐(hydroxymethyl)propanoic acid (AB2 type monomer) functionalized with amino acids, L ‐arginine included,, for obtaining polycationic biodegradable macromolecules able to bind DNA, RNA or drugs and to transfect cells for gene or drug delivery uses. The converging and diverging synthetic strategy used by us provides a series of protection‐activation‐deprotection reactions of the bifunctional monomer AB2 and its dendrons derivatives.…”