Acid‐base properties of poly(amidoamine)s

Abstract

Polyamidoamines (PAAs) represent a family of degradable polymers carrying tert-amine groups in the polymer backbone, which behave as polyelectrolytes in aqueous solutions. Many relevant properties of PAAs, including the ability to interact with components of the biological environments, such as nucleic acids, proteins, and living cells, are strongly dependent on their acid-base properties, hence on their ionization state in different biological districts. In this article, the protonation constants of a series of PAAs have been precisely determined by electrochemical techniques in order to build up a homogeneous library containing both the protonation constants and the average distribution of the charged species, hence the net average charge as a function of pH. Moreover, correlations between chemical and cytotoxicity, have been attempted.

Amphoteric, Prevailingly Cationic L‐Arginine Polymers of Poly(amidoamino acid) Structure: Synthesis, Acid/Base Properties and Preliminary Cytocompatibility and Cell‐Permeating Characterizations

“…The titration curves were processed assuming that all repeating units behave independently and, for the same reason, the dissociation constants were not biased by the polymer molecular weight. In other words, no significant polyelectrolyte effect was considered . The p K a values obtained are summarized in Table , where, for comparison purposes, the p K a values L ‐arginine, from literature data, are also reported.…”

“…As regards L‐ARGO7‐ co ‐MBAP, potentiometric measurements revealed only four p K a values, namely p K a1 ≤ 2.0, p K a2 = 5.7, p K a3 = 7.2 and p K a4 > 12.0. p K a2 and p K a4 were virtually identical to p K a1 and p K a3 of L‐ARGO7. Considering that the p K a values determined for several 2‐piperazine‐based PAAs were approximately 7.3 and 3.3, p K a1 of L‐ARGO7‐ co ‐MBAP corresponded to the first de‐protonation of the di‐piperazinium ion and p K a3 results from the merging of the higher p K a of the piperazine moiety with that of the tertiary amine group of the L ‐arginine moiety.…”

Degradable Poly(amidoamine) Hydrogels as Scaffolds for In Vitro Culturing of Peripheral Nervous System Cells

“…On the other side, the biocompatibility of PAAs is usually higher the lower their cationic charge at pH 7.4. A library of acid‐base properties of PAAs indicates that the piperazine‐derived ones are the weakest of all, with p K a1 and p K a2 in the order of 7.4 and 3.8, respectively, independently of the structure of the bis(acrylamide) moiety 27. Therefore, it can be predicted that at physiological pH only one‐half of the piperazine moieties bears a positive charge, resulting in a modest density of positive charges along the polymer chain, on the average one every 500 Da.…”

Polyamidoamine and polyglycerol; their linear, dendritic and linear–dendritic architectures as anticancer drug delivery systems

“…192 Therefore using aminoacids as starting monomer leads to more cytobiocompatible PAAs. 193 The PAAs in their salt 65 forms together with different counter ions including acetate, citrate and lactate were found to be non-hemolytic and noncytotoxic at the pH 5.5. 194 Additionally, some other factors including concentration of PAAs, exposure time to cells, density of cationic residues interacting with the cell and the basic 70 monomer structure can also affect the cytotoxicity of PAAs.…”