Synthesis and Endosomolytic Properties of Poly(amidoamine) Block Copolymers

Abstract

Summary: The poly(amidoamine)s (PAAs) ISA 1 and ISA 23 display pH‐dependent conformational change and pH‐dependent membrane perturbation. These properties confer potential for use as endosomolytic polymers for intracytoplasmic delivery of toxins and genes. Both polymers are relatively non‐toxic, and moreover ISA 23 has the beneficial property in vivo, of being non hepatotropic when administered intravenously. Although ISA 23 and ISA 1 demonstrate ability to transfect cells, ISA 1 is also able to promote intracellular delivery of non‐permeant toxins. The aim of this study was to synthesise random and block copolymers of ISA 1 and ISA 23 and investigate whether these second generation hybrids would allow optimisation of PAA biological characteristics. Random and block copolymers of ISA 1 and ISA 23 were synthesised by hydrogen transfer polyaddition to generate a library of PAAs with an ISA 23:ISA 1 molar ratios of 2:1 to 4:1. The resultant polymers have a pI slightly below 7.4 and a $\overline M _{\rm w}$ of 19 900–49 000 g/mol and a $\overline M _{\rm n}$ of 13 100–24 100 g/mol. Whereas none of the random or block copolymers were haemolytic at pH 7.4 all demonstrated pH‐dependent membrane activity. At pH 5.5 they caused 50–60% haemoglobin (Hb) release over 1 h. This was slightly less than that seen for ISA 23 (80% Hb release). None of the copolymers were cytotoxic against B16F10 cells during a 72 h incubation (IC50 > 2 mg/ml; MTT assay). The ability of the random and block copolymer PAAs to deliver the toxin gelonin was also examined, but only ISA 1 and the block copolymer B2 (ISA 23:ISA 1 at a 2:1 molar ratio) were able to promote intracellular delivery, as measured by cytotoxic activity. It would be interesting to study the body distribution of B2 and determine whether this toxin‐delivering PAA is able to escape liver capture. magnified image

Preparation of an amphiphilic triblock copolymer with pH- and thermo-responsiveness and self-assembled micelles applied to drug release

“…Thus, this thermo-responsive property has been utilized as an ''on-off" switch for drug release, attachment/detachment of cells, and so on [16][17][18][19]. Besides, pH is another important stimulus, which has been used to develop pH-responsive materials [4,20,21]. Weakly acidic or alkalescent polymers containing carboxylic acid or amine are the pH-responsive candidates that undergo a change in the ionization state on the variation of pH values, resulting in a reversible change between hydrophilicity and hydrophobicity.…”

Polyamidoamine Nanoparticles as Nanocarriers for the Drug Delivery to Malaria Parasite Stages in the Mosquito Vector

“…ISA23 in particular has been proven to be endowed with stealth-like properties without selectively concentrating in the liver [44], while a significant portion of AGMA1 did show hepatic localization after intravenous injection in mice [42]. In intracellular compartments where the pH decreases to 6.5 (endosomes) and then to 5.0 (lysosomes), PAAs become prevailingly cationic and display endosomolytic properties [72]. Fluorescence microscopy revealed colocalization of ISA1 and ISA23 with Lysotracker, a marker for lysosome and late endocytic structures, and ISA1 also colocalized with the Early Endosomal Antigen 1 that accumulates in early endocytic structures [45].…”

Poly(amidoamine)s synthesis, characterisation and interaction with BSA

“…10,11 Recent studies have demonstrated that modulation of the PAAs hydrophobicity inuenced binding of the polymer to DNA. 12,13 Although several studies have reported intracellular delivery of proteins with PAAs, [14][15][16] there is no report investigating the interaction of the poly(amidoamine)s with proteins. Polyelectrolyte-protein complexation has been studied in the context of protein purication, enzyme immobilisation, sensor development or stimuli responsive systems.…”

“…Although poly(amidoamine)s have been used to promote intracellular delivery, 5,11,14,15 the interactions between the polymers and the protein and their effect on the protein stability are poorly understood. Protein-polyelectrolyte complexation may results from different types of interactions, including ionic and hydrophobic interactions, hydrogen bonding or coulombic forces.…”