Nonionic Water-Soluble and Cytocompatible Poly(amide acrylate)s

Bioactive poly(2-oxazoline)-based nanomaterials bearing arylalkylamine and benzamide motifs possess intrinsic radical trapping and anti-ferroptosis properties

Radical trapping agents such as Ferrostatin-1 (Fer-1) are capable of rescuing cells from ferroptosis, an iron-dependent form of cell death. Previously, poly(2-oxazoline)-Fer-1 (POx-Fer-1) conjugates were reported, which possess increased water-solubility and remain active after covalent conjugation of Fer-1. In this study, we break down the structural and functional layers of POx-Fer-1 conjugates and reveal that drug-free POx containing arylalkylamine and benzamide motifs show anti-ferroptosis properties. Intriguingly, even the basic construct poly(2-methyl-2-oxazoline-grad-2-phenyl-2-oxazoline) P(MeOx-grad-PhOx) was found to be active. Therefore, P(MeOx-grad-PhOx) of varying compositions were prepared, characterized by ¹H NMR spectroscopy and size exclusion chromatography and investigated with regard to their self-assembly in aqueous solution and activity in an in vitro ferroptosis model. These findings were further explored for the design of defined and bioactive core-crosslinked micelles with intrinsic anti-ferroptosis behaviour. Cellular interaction studies involving C₁₁-BODIPY assays and confocal microscopy investigations revealed lysosomal processing of the nanomaterials and perturbation of ferroptotic cell death through reducing lipid-peroxidation. This study highlights new drug/cargo-free anti-ferroptotic nanomaterials as proof of concept that hold potential for therapy of ferroptosis-associated diseases and highlights the role of nanocarriers in a therapeutic context.

Zwitterionic Amino Acid-Derived Polyacrylates as Smart Materials Exhibiting Cellular Specificity and Therapeutic Activity

The synthesis of new amino acid-containing, cell-specific, therapeutically active polymers is presented. Amino acids served as starting material for the preparation of tailored polymers with different amino acids in the side chain. The reversible addition-fragmentation chain-transfer (RAFT) polymerization of acrylate monomers yielded polymers of narrow size distribution (Đ ≤ 1.3). In particular, glutamate (Glu)-functionalized, zwitterionic polymers revealed a high degree of cytocompatibility and cellular specificity, i.e., showing association to different cancer cell lines, but not with nontumor fibroblasts. Energy-dependent uptake mechanisms were confirmed by means of temperature-dependent cellular uptake experiments as well as localization of the polymers in cellular lysosomes determined by confocal laser scanning microscopy (CLSM). The amino acid receptor antagonist O-benzyl-l-serine (BzlSer) was chosen as an active ingredient for the design of therapeutic copolymers. RAFT copolymerization of Glu acrylate and BzlSer acrylate resulted in tailored macromolecules with distinct monomer ratios. The targeted, cytotoxic activity of copolymers was demonstrated by means of multiday in vitro cell viability assays. To this end, polymers with 25 mol % BzlSer content showed cytotoxicity against cancer cells, while leaving fibroblasts unaffected over a period of 3 days. Our results emphasize the importance of biologically derived materials to be included in synthetic polymers and the potential of zwitterionic, amino acid-derived materials for cellular targeting. Furthermore, it highlights that the fine balance between cellular specificity and unspecific cytotoxicity can be tailored by monomer ratios within a copolymer.

Thermoresponsive properties of polymer hydrogels induced by copolymerization of hydrophilic and hydrophobic monomers: comprehensive study of monomer sequence and water affinity

In order to raise the possibility of the practical use of thermoresponsive hydrogels in various fields, it is imperative to achieve on-demand control of responsive behavior especially by using a simple synthetic method with common monomers. To this end, we synthesized various hydrophilic/hydrophobic copolymer hydrogels from common acrylamide derivatives and acrylate monomers via free radical copolymerization, and examined the correlation between the structure and the swelling properties of the obtained gels, specifically from the viewpoint of the monomer sequence in the network chains and the affinity to water molecules. The obtained gels with a hydrophobic acrylamide monomer were shown to exhibit a sharp volume change in water upon heating at suitable monomer compositions. In contrast, the gels consisting of a hydrophobic acrylate monomer only decreased the swelling degree with no significant thermoresponsive volume change. The formation of a local amphiphilic structure without a long hydrophobic sequence is critical for achieving sharp thermoresponsiveness. Moreover, the water affinity was drastically changed at a sharp volume transition with the copolymer gels of a hydrophobic acrylamide. This transition was most likely driven by an entropic factor because of the strong contribution of the hydration/dehydration of the network chains. The comparison of the temperature-responsive behavior of the gels with that of the corresponding linear copolymers demonstrated that the crosslinking structure made significant hydrophobic contribution to the responsive behavior.

Poly(tertiary amide acrylate) Copolymers Inspired by Poly(2-oxazoline)s: Their Blood Compatibility and Hydration States

Modifying the side chain of poly(meth)acrylate with moieties originating from biocompatible polymers can be an effective method for developing novel blood-compatible polymers. Inspired by biocompatible poly(2-methyl-2-oxazoline) (PMeOx) and poly(2-ethyl-2-oxazoline) (PEtOx), four water-soluble poly(tertiary amide acylate) analogues bearing a pendant tertiary amide were synthesized. The results of hemolysis and cell viability tests showed that all the poly(tertiary amide acylate) analogues were compatible with red blood cells, HeLa cells, and normal human dermal fibroblasts as PMeOx or PEtOx. Among the four poly(tertiary amide acylate) analogues, poly[2-(N-methylpropionamido)ethyl acrylate] (PPEA) and poly[2-(N-ethylacetamido)ethyl acrylate] (PEAE) showed thermosensitivity in aqueous solution; especially, PPEA (10 mg mL^-1) exhibited a lower critical solution temperature of 37 °C. Water-insoluble copolymers were prepared to investigate the possibility of applying these synthesized polymers as blood-compatible coatings. The poly[n-butyl methacrylate₇₀-co-2-(N-methylacetamido)ethyl methacrylate₃₀] (coPAEM) coatings significantly suppressed plasma protein adsorption, denaturation degree of adsorbed fibrinogen, and platelet adhesion. Intermediate water (IW), whose content can generally indicate the blood compatibility of polymers, was found in all hydrated homopolymers and copolymers by differential scanning calorimetry. The present work demonstrated that the tertiary amide moiety in the side chain of poly(meth)acrylate was an effective contributor to blood compatibility and IW.

Adamantane Functionalized Poly(2-oxazoline)s with Broadly Tunable LCST-Behavior by Molecular Recognition

Smart or adaptive materials often utilize stimuli-responsive polymers, which undergo a phase transition in response to a given stimulus. So far, various stimuli have been used to enable the modulation of drug release profiles, cell-interactive behavior, and optical and mechanical properties. In this respect, molecular recognition is a powerful tool to fine-tune the stimuli-responsive behavior due to its high specificity. Within this contribution, a poly(2-oxazoline) copolymer bearing adamantane side chains was synthesized via triazabicyclodecene-catalyzed amidation of the ester side chains of a poly(2-ethyl-2-oxazoline-stat-2-methoxycarbonylpropyl-2-oxazoline) statistical copolymer. Subsequent complexation of the pendant adamantane groups with sub-stoichiometric amounts (0-1 equivalents) of hydroxypropyl β-cyclodextrin or β-cyclodextrin enabled accurate tuning of its lower critical solution temperature (LCST) over an exceptionally wide temperature range, spanning from 30 °C to 56 °C. Furthermore, the sharp thermal transitions display minimal hysteresis, suggesting a reversible phase transition of the complexed polymer chains (i.e., the β-cyclodextrin host collapses together with the polymers) and a minimal influence by the temperature on the supramolecular association. Analysis of the association constant of the polymer with hydroxypropyl β-cyclodextrin via 1H NMR spectroscopy suggests that the selection of the macrocyclic host and rational polymer design can have a profound influence on the observed thermal transitions.

Tuning Cellular Interactions of Carboxylic Acid-Side-Chain-Containing Polyacrylates: The Role of Cyanine Dye Label and Side-Chain Type

Cellular uptake and intracellular targeting to specific organelles are key events in the cellular processing of nanomaterials. Herein, we perform a detailed structure-property relationship study on carboxylic acid-side-chain-bearing polyacrylates to provide design criteria for the manipulation of their cellular interactions. Redox-initiated reversible addition-fragmentation chain-transfer (RRAFT) polymerization of three tert-butyl-protected N-acylated amino ester-based acrylate monomers of different substitutions and degrees of polymerization (DPs) yielded defined and pH-responsive carboxylic acid-side-chain polymers upon deprotection (N-acetyl, DP 1: P(M₁); N-propionyl, DP 1: P(E₁), DP 2: P(E₂)). Flow cytometry studies revealed time-dependent cell association with P(E₂) > P(E₁) > P(M₁) at any given time point. Importantly, the type of cyanine dye used for labeling was found to significantly influence the cellular processing of the polymers. Changing the dye from Cy5 to its sulfonated version sulfoCy5 resulted in a much lower cellular association. Moreover, Cy5-labeled polymers were targeted to mitochondria, while sulfoCy5 modification caused a significant change in the cellular fate of polymers toward lysosome trafficking. This study highlights the importance of selecting a suitable dye but also demonstrates the possibilities for the rational design of organelle-specific targeting of carboxylated polyacrylates.