Fig. 1. Examples of self-assembled nanomaterials with core-shell structure: (A) PEGylated liposomes produced from mixture of PEGylated and non-PEGylated lipids [8]; (B) polymer micelles with hydrophobic core formed by amphiphilic block copolymer [21]; (C) polyplex obtained by reacting DNA with cationic block/graft copolymer in presence of Pluronic® [178]; (D) polymer micelles with ionic core synthesized by condensing double hydrophilic block copolymer containing ionic block (poly (methacrylic acid) (PMA)) by Ca²⁺, cross-linking of the ionic blocks in the core of the formed micelles and removal of the condensing agent [33].

Fig. 2. Chemical structures of some polymers administered in the body.

Fig. 3. Scheme 1: A cooperative polyelectrolyte interchange reaction: At the first stage the free polyion (C) diffuses to the interpolyelectrolyte complex (AB); the chains reside together in the intermediate tertiary complex, while the oppositely charged polyion (B) migrates from polyion (A) to polyion (C); at the last stage the new interpolyelectrolyte complex (AC) is formed [91]. Scheme 2: Migration of polyions adsorbed at the oppositely charged particles: Polyelectrolyte adsorbed at the surface of untargeted particles (U) cannot dissociate into a solution; instead the particles migrate to each other forming a intermediate complex; the adsorbed polyion migrates to the surface of the targeted particles (T) where it is anchored through the ligand-receptor binding [95]. This mechanism was proposed for the recognition of specific immune cells by polyelectrolyte–antigen conjugates used as artificial vaccines as discussed in Section 5.

Fig. 4. Pluronic® block copolymers activate NF-κB signaling in cells: (A) Pluronic® affects NF-κB signaling presumably by interacting with cell plasma membrane; (B) this leads to rapid phosphorylation of I-kB accompanied by the release of the NF-κB [115]; (C) the released NF-κB translocates to the nucleus and activates transcription of the corresponding genes.

Fig. 5. Sensitization of MDR tumors by Pluronic® block copolymer: (A) Pluronic® binds with the cell membrane and inhibits Pgp ATPase; (B) Pluronic® also translocates inside cells and inhibits respiration in the mitochondria resulting in ATP depletion; (C) Pgp efflux pump shuts down; (D) the drug enters the cell and induces cytotoxic effect; (E) in the presence of Pluronic® the pro-apoptotic signaling in response to the drug is enhanced.