Poly(amidoamine)s with potential as drug carriers: degradation and cellular toxicity

Abstract

Poly(amidoamine)s were synthesized by polyaddition reaction: to bis-acryloylpiperazine of piperazine (1), or N,N'-bis(2-hydroxyethyl)ethylenediamine (2), and to 2,2-bis(acrylamido)acetic acid of piperazine (3). Compound 2 was also end-capped with 4-hydroxythiophenol, thus introducing a terminal moiety suitable for radio-iodination using the chloramine T method (4). Such polymers behave as bases in aqueous solution, and their net average charge alters considerably as the pH changes from 7.4 to 5.5. This results in a change in polymer conformation which may prove useful in the design of polymeric drug delivery systems. However, their suitability for use in the organism will depend on polymer toxicity and also on their rate of biodegradation. Here we studied the biological properties of the above poly(amidoamine)s with a view to optimizing the synthesis of novel drug carriers. The general cytotoxicity of compounds 1, 2, 3, and 4 was examined in vitro using two human cell lines, hepatoma (HepG2) and a lymphoblastoid leukaemia (CCRF). Several different methods [the tetrazolium (MTT) test, [3H]leucine or [3H]thymidine incorporation, or counting cell numbers] were used to measure cell viability. Compounds 1, 2, and 4 were much less toxic to both cell lines than equivalent concentrations of the polycationic poly-L-lysine, and in no case did viability fall below 50% (concentrations up to 2 mg/ml). Although compound 2 was not markedly toxic to HepG2 cells, concentration-dependent toxicity was observed against CCRF cells. In this case, the polymer concentration decreasing viability by 59% (ID50) was approximately 50 micrograms/ml for compound 2 compared with an ID50 of approximately 10 micrograms/ml for poly-L-lysine. The rate of hydrolytic degradation of compound 2 was examined using viscometric measurements and gel permeation chromatography (GPC). After incubation at pH 7.5 and 8.0 for 24 h, polymer intrinsic viscosity was decreased by approximately 50% and GPC elution profiles showed a simultaneous increase in polymer retention time, indicating a fall in molecular weight. Hydrolytic degradation progressed much more slowly at pH 5.5. Compound 4 was also incubated with a mixture of isolated rat liver lysosomal enzymes (tritosomes) at pH 5.5, but no increase in the rate of degradation was observed.

The AGMA1 poly(amidoamine) inhibits the infectivity of herpes simplex virus in cell lines, in human cervicovaginal histocultures, and in vaginally infected mice

“…Most PAAs are only moderately toxic despite their polycationic nature. According to a number of tests, the toxicity of most PAAs is significantly lower than that of poly-Llysine (PLL) or polyethylenimine (PEI) [24]. Amphoteric PAAs carrying side carboxyl groups switch from a prevailingly anionic to a prevailingly cationic state in a relatively small pH interval.…”

Synthesis and Endosomolytic Properties of Poly(amidoamine) Block Copolymers

“…Poly(amidoamine)s (PAAs) are synthetic tert-amino polymers, which are produced by hydrogen transfer polyaddition of primary or secondary mono(amine)s to bis(acrylamide)s. [1][2][3] They are water-soluble, biodegradable and are less toxic [4,5] than other cationic polymers such as poly(L-lysine), [6] polyethyleneimine (PEI) [7] or poly (amidoamine) (PAMAM) dendrimers [8] all of which have been widely proposed as non-viral vectors. In aqueous solution, amino and amido groups arranged along the PAA polymeric chain confer moderate basicity to the polymer.…”

“…[13,14] From the large library of PAAs so far examined, [4,9,10] two PAAs have emerged as particularly interesting. The amphoteric ISA 23 (and its analogue ISA 22, in which 4% of 2-methylpiperazine units have been replaced by 2-(4-hydroxy)phenylethylamine units to allow radioiodination) and the more cationic ISA 1 (and its 2-(4-hydroxy)phenylethylamine analogue, called ISA 4) (Figure 1).…”

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

“…In aqueous media PAAs degrade within days or weeks to oligomeric products [39,40], in a process strongly influenced by the structure of amide and amine moieties that increases at basic pH and higher temperatures (40-60 °C). The degradation mechanism seems to be purely hydrolytic and not affected by the presence of lysosomal enzymes at pH 5.5 [41]. The toxicity of PAAs and their low molecular mass degradation products is two or more orders of magnitude lower than that of other polycations such as poly-L-lysine, polyethyleneimine or PAMAM dendrimers [34].…”