Synthesis and preliminary evaluation of poly(amidoamine)–melittin conjugates as endosomolytic polymers and/or potential anticancer therapeutics

Abstract

The pH-responsive poly(amidoamine)s (PAAs) have been previously described. Whereas ISA23 enhances transfection in vitro and ISA1 promotes the cytosolic delivery of the non-permeant toxins this process shows poor efficiency. The aim of this study was to prepare and evaluate PAA conjugates containing the membrane disrupting peptide melittin (MLT). It was hypothesised that PAA conjugation would reduce the haemolytic activity of MLT at pH 7.4, however, upon delivery to tumours by the EPR effect, the polymer would uncoil in an acidic environment exposing MLT and allowing it to interact with membranes. PAA-MLT conjugates were prepared using MLT as a comonomer together with bis-acryloylpiperazine, 2-methylpiperazine and bis-hydroxyethylethylenediamine (ISA1-like), or bis-acrylamidoacetic acid and 2-methylpiperazine (ISA23-like). The melittin content of the conjugates was 6-19% (w/w). Although ISA1-MLT improved gelonin delivery compared to the parent polymer ISA1 (␣ 13-fold increase) and showed pH-dependent haemolytic activity at a polymer concentration of 0.05 mg/ml, this conjugate also displayed high haemolytic activity at pH 7.4. In contrast, ISA23-MLT like the parent compound ISA23 did not deliver gelonin. However, this conjugate could have potential as a novel polymeric anticancer conjugate due to its lack of haemolytic activity at pH 7.4 and retention of cytotoxicity.

Melittin: a Membrane-active Peptide with Diverse Functions

“…These results suggest that naturally occurring melittin possesses a dual endosomolytic and nuclear-homing functionality that can form the basis of a powerful transfection agent and makes it an interesting candidate for the further development of systemic gene delivery in vivo. A very recent report supports the endosomolytic function of melittin conjugates (Lavignac et al 2005).…”

Novel chimeric peptide with enhanced cell specificity and anti-inflammatory activity

“…Melittin, from the European honeybee venom (Apis mellifera), is cytotoxic peptide with 26 amino acids and possesses a broad spectrum of antimicrobial activity [29,30]. Although its cytotoxicity and allergenicity are high, a number of studies have examined potential applications in therapeutic and biotechnological fields, focusing on bacterial infections [31], rheumatoid arthritis [32], arteriosclerosis [33], immunologic adjuvants [32], cancer [34], and endosomolytic material in drug delivery systems [35,36]. The substitution and deletion of amino acids are general methods to reduce the cytotoxic effect, but it is sometimes limited due to the length and structure of the peptide.…”

Controlling and Monitoring Intracellular Delivery of Anticancer Polymer Nanomedicines

“…However, although MLT conjugation was beneficial for endosomal disruption, at least for one of the conjugates, its hemolytic activity at pH 7.4 was still considered unacceptable. [143] …”