Abstract
An amphoteric random copolymer (P(SA)91) composed of anionic sodium 2-acrylamido-2-methylpropanesulfonate (AMPS, S) and cationic 3-acrylamidopropyl trimethylammonium chloride (APTAC, A) was prepared via reversible addition-fragmentation chain transfer (RAFT) radical polymerization. The subscripts in the abbreviations indicate the degree of polymerization (DP). Furthermore, AMPS and APTAC were polymerized using a P(SA)91 macro-chain transfer agent to prepare an anionic diblock copolymer (P(SA)91S67) and a cationic diblock copolymer (P(SA)91A88), respectively. The DP was estimated from quantitative 13C NMR measurements. A stoichiometrically charge neutralized mixture of the aqueous P(SA)91S67 and P(SA)91A88 formed water-soluble polyion complex (PIC) micelles comprising PIC cores and amphoteric random copolymer shells. The PIC micelles were in a dynamic equilibrium state between PIC micelles and charge neutralized small aggregates composed of a P(SA)91S67/P(SA)91A88 pair. Interactions between PIC micelles and fetal bovine serum (FBS) in phosphate buffered saline (PBS) were evaluated by changing the hydrodynamic radius (Rh) and light scattering intensity (LSI). Increases in Rh and LSI were not observed for the mixture of PIC micelles and FBS in PBS for one day. This observation suggests that there is no interaction between PIC micelles and proteins, because the PIC micelle surfaces were covered with amphoteric random copolymer shells. However, with increasing time, the diblock copolymer chains that were dissociated from PIC micelles interacted with proteins.
Highlights
A mixture of oppositely charged polyelectrolytes in water forms a water-insoluble polyion complex (PIC) due to attractive electrostatic interactions between the polymer chains [1].Many researchers study polymer aggregates formed by electrostatic interactions
Charged diblock copolymers of anionic P(SA)91 S67 and cationic P(SA)91 A88 were prepared via reversible addition-fragmentation chain transfer (RAFT) using P(SA)91 macro‐chain transfer agent (CTA)
The PIC micelles were in a dynamic equilibrium state with PIC micelles and charge neutralized small aggregates composed of a P(SA)91S67/P(SA)91A88 pair
Summary
A mixture of oppositely charged polyelectrolytes in water forms a water-insoluble polyion complex (PIC) due to attractive electrostatic interactions between the polymer chains [1].Many researchers study polymer aggregates formed by electrostatic interactions. A mixture of oppositely charged polyelectrolytes in water forms a water-insoluble polyion complex (PIC) due to attractive electrostatic interactions between the polymer chains [1]. When oppositely charged diblock copolymers containing nonionic water-soluble poly(ethylene glycol) (PEG) and polyelectrolyte blocks are mixed in water, the polymers spontaneously form water-soluble PIC micelles covered with hydrophilic PEG shells [2,3]. 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]. 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
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