Micellar self-assembly, bridging and gelling behaviour of two reverse triblock poly(butylene oxide)–poly(ethylene oxide)–poly(butylene oxide) copolymers with lengthy hydrophilic blocks

Abstract

Reverse architecture of BOnEOmBOn block copolymers enables the formation of micellar clusters and viscous gels at low concentrations by chain bridging.

Reverse poly(butylene oxide)–poly(ethylene oxide)–poly(butylene oxide) block copolymers with lengthy hydrophilic blocks as efficient single and dual drug-loaded nanocarriers with synergistic toxic effects on cancer cells

“…These copolymers form spherical micelles ranging from 17 to 35 nm in diameter and have association numbers between 20 and 43 (see Table 1). 48,49 At higher polymer concentrations, viscous (from 1 to 6 wt%) and immobile gels (>5 wt%, depending on copolymer type and solution temperature) appear as a consequence of the cross-linking, originating from the residence of BO blocks in one polymer chain in two adjacent micelles promoting a progressively denser open network structure. For HeLa cells, cell viabilities (CVs) between 90% and 100% were found for the copolymer, BO 8 EO 90 BO 8 , over the whole concentration range.…”

“…52 As mentioned previously, BO blocks are six times more hydrophobic than PPO units present in commercial Pluronic and Tetronic block copolymers (on the basis of their molar cmcs) so a better compatibility between BO blocks and the present antineoplastic hydrophobic drugs might be expected in agreement with previous observations made for much shorter diblock EO m BO n and triblock EO m BO n EO m copolymers. 48,49 Single (DCX) and dual (DCX/DOXO) encapsulation experiments were carried out to evaluate the impact of the feeding drug amount on the entrapment efficiency and the total loaded drug amount inside micelles by means of UV-Vis spectrophotometry and HPLC. Preliminary attempts at dissolving DCX and DOXO into preformed micelles resulted in low drug loading, probably because of the slow drug diffusion into the viscous micellar core (data not shown).…”

“One-pot” aminolysis/thia-Michael addition preparation of well-defined amphiphilic PVDF-b-PEG-b-PVDF triblock copolymers: self-assembly behaviour in mixed solvents

“…Finally, if the system is too diluted, the intermicellar interactions will be too rare for bridges to form. 17 In industry most ABA triblock copolymers are prepared by anionic polymerization. 12,18 However, progress in Reversible Deactivation Radical Polymerization (RDRP) techniques, such as RAFT (Reversible Addition-Fragmentation chain Transfer), 19,20 ATRP (Atom-Transfer Radical Polymerization) 21,22 or CMRP (Cobalt-Mediated Radical Polymerization) 23 for example, have enabled the facile synthesis of ABA triblock copolymers.…”

Intelligent micellar polymeric nanocarriers for therapeutics and diagnosis

“…This structure is referred to as unimolecular micelles . Triblock copolymers with short hydrophobic end blocks (called telechelics ) may be prone to associating into flowerlike micelles, in which hydrophilic middle blocks are looped . The bridging of these micelles occurs when the middle block spans the space between different micelles.…”

“…Nevertheless, a compromise between the chain solubility and micellar core size must be attained by the tuning of the EO and SO block lengths, with an empirical optimal EO–SO ratio found at about 1.5 . Furthermore, the influence of the amount of feeding drug on the encapsulation yield was also largely evidenced …”