Preparation of Giant Polyion Complex Vesicles (G-PICsomes) with Polyphosphobetaine Shells Composed of Oppositely Charged Diblock Copolymers

Abstract

Diblock copolymers composed of a water-soluble polyphosphobetaine block with a short chain length and either a cationic or anionic block were prepared. Giant polyion complex vesicles (G-PICsomes), with a size on the order of micrometers, were prepared by dialysis from a mixture of oppositely charged diblock copolymers in a 1.5 M NaCl aqueous solution against pure water. Hydrophilic guest molecules could be encapsulated into the G-PICsomes. Vesicles formed from phospholipids, 1 low-molecularweight surfactants, 2 and block copolymers 3 have been studied intensively for a wide range of applications such as drug carriers, 4 cell membrane models, 5 and templates for hollow particles. 6,7 Vesicles formed from block copolymers are called polymer vesicles or polymersomes. 8 To prepare polymersomes, reaction conditions, such as the choice of the solvent, composition of the polymer, water content, ionic strength, and temperature, should be optimized. 913 Precise size control of the vesicles can be very important. Although ultrasonic, 14 extrusion, 15 homogenization, 16 and solution methods 17 can help create vesicles of relatively uniform size, strict size control has been difficult to achieve. Controlling the size of polymersomes also can be difficult.The fabrication of giant vesicles using low-molecularweight surfactants 18,19 and polymers 20 has been reported. Zhou et al. 21 reported the synthesis of giant vesicles via the selforganization of an amphiphilic multi-arm copolymer (HBPOstar-PEO) composed of a hyperbranched poly(3-ethyl-3-oxetanemethanol) core and poly(ethylene oxide) arms. Kataoka et al. 22 reported the preparation of polymersomes (PICsomes) with a size of up to 10¯m using a polyion complex (PIC), which consist of oppositely charged polymers held together via electrostatic interactions. The giant-PICsomes (G-PICsomes) were prepared by mixing of a pair of oppositely charged diblock copolymers composed of nonionic water-soluble poly(ethylene glycol) blocks and charged poly(amino acid) blocks.The present study describes a novel preparation method for G-PICsomes through the dialysis of a 1.5 M NaCl aqueous solution containing a mixture of oppositely charged diblock copolymers (Figure 1 , M w /M n = 1.07) composed of PMPC blocks and anionic poly[sodium 2-(acrylamido)-2-methylpropanesulfonate] (PAMPS) blocks also was prepared via RAFT polymerization (P, M, and A indicate PMPC, PMAPTAC, and PAMPS blocks, respectively). Subscript numbers indicate the degree of polymerization (DP) of each block estimated by 1 H NMR. Characteristic data for each polymer are summarized in Table S1. Separate 0.1 M NaCl aqueous solutions of P 20 M 190 and P 20 A 196 were mixed to neutralize the charges and form PIC Figure 1. (a) Chemical structures of oppositely charged diblock copolymers (P 20 M 190 and P 20 A 196 ) and (b) preparation of giant polyion complex vesicles (G-PICsomes) using a dialysis method to reduce NaCl concentration.

Preparation of Water-soluble Polyion Complex (PIC) Micelles Covered with Amphoteric Random Copolymer Shells with Pendant Sulfonate and Quaternary Amino Groups

“…PIC micelles can encapsulate charged compounds such as metal ions, proteins, and nucleic acid in the PIC core via electrostatic interactions [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ]. Recently, water-soluble PIC micelles were prepared with hydrophilic poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) coronas without net charge [ 12 , 13 , 14 ]. PMPC has pendant phosphorylcholine groups with the same chemical structure as the hydrophilic part of phospholipids comprising cell membranes.…”

Thermo-Responsive Polyion Complex of Polysulfobetaine and a Cationic Surfactant in Water

“…This indicated that [NaCl] strongly influenced the T p value of the PSBP/CTAB complex. At an [NaCl] of 0.06 M, the T p of the PSBP/CTAB complex was 31.2 °C, whereas it decreased to 4.8 °C for an [NaCl] of 0.15 M. This might be due to the counterions, Na + and Cl − , replacing the anionic and cationic groups in PSBP and CTAB [ 60 ], which would partially reduce the total energy required to break the electrostatic interactions that form the complex.…”

Creation of supramolecular biomembrane by the bottom-up self-assembly: Where material science meets biophysics

“…Artificial membranes can be produced also solely by synthetic polymers based on the self-assembly of block copolymers. Yusa et al have extensively studied the supramolecular assembly of block copolymers in an aqueous solution mediated by the formation of polyion complex [17][18][19]. The formation of polyion complex originated in the multi-point electrostatic interactions between polymer chains aids the self-assembly in water that plays a similar role to Figure 2 Chemical structures of polymers for the spontaneous formation of nanodiscs (1) [14] and supramolecular assembly via polyion complex formation (2) [19].…”

“…In contrast, the block polymer with a zwitterionic domain shorter than the charged domain assembles into vesicles [ 18 ]. Giant polyion complex vesicles in μm scale were also produced by the dialysis of the polymer solution containing a high concentration of sodium chloride as a salt due to the gradual modulation of the electrostatic interaction between charged domains [ 19 ].…”