Abstract
It is of great significance to study the structure property and self-assembly of amphiphilic block copolymer in order to effectively and efficiently design and prepare drug delivery systems. In this work, dissipative particle dynamics (DPD) simulation method was used to investigate the structure property and self-assembly ability of pH-responsive amphiphilic block copolymer poly(methyl methacrylate-co-methacrylic acid)-b-poly(aminoethyl methacrylate) (poly(MMA-co-MAA)-b-PAEMA). The effects of different block ratios (hydrophilic PAEMA segment and pH-sensitive PMAA segment) in copolymer on self-assembly and drug loading capacity including drug distribution were extensively investigated. The increase of hydrophilic PAEMA facilitated the formation of a typical core-shell structure as well as a hydrophobic PMAA segment. Furthermore, the optimal drug-carrier ratio was confirmed by an analysis of the drug distribution during the self-assembly process of block copolymer and model drug Ibuprofen (IBU). In addition, the drug distribution and nanostructure of IBU-loaded polymeric micelles (PMs) self-assembled from precise block copolymer (PMMA-b-PMAA-b-PAEMA) and block copolymer (poly(MMA-co-MAA)-b-PAEMA) with random pH-responsive/hydrophobic structure were evaluated, showing that almost all drug molecules were encapsulated into a core for a random copolymer compared to the analogue. The nanostructures of IBU-loaded PMs at different pH values were evaluated. The results displayed that the nanostructure was stable at pH < pKa and anomalous at pH > pKa which indicated drug release, suggesting that the PMs could be used in oral drug delivery. These findings proved that the amphiphilic block copolymer P(MMA30-co-MAA33)-b-PAEMA38 with random structure and pH-sensitivity might be a potential drug carrier. Moreover, DPD simulation shows potential to study the structure property of PMs self-assembled from amphiphilic block copolymer.
Highlights
Various core-shell polymeric nanocarriers self-assembled from amphiphilic block copolymers in aqueous solution have been extensively developed and investigated [1,2,3,4,5,6]
When this ratio increased to 38% (Figure 2D), the copolymer poly(MMA30-co-MAA33)-b-PAEMA38 was dispersed in water and self-assembled into onion-like IBU-loaded polymeric micelles (PMs)
It is observed that the PM exhibited a typical core-shell architecture with the poly(MMA-co-MAA) core and surrounded the poly(2-amino ethyl methacrylate) (PAEMA) shell. These findings indicated that the poly(MMA30-co-MAA33)-b-PAEMA38 was able to self-assemble into PM by coalescence of small clusters in aqueous solution
Summary
Various core-shell polymeric nanocarriers self-assembled from amphiphilic block copolymers in aqueous solution have been extensively developed and investigated [1,2,3,4,5,6]. Natural chitosan-based copolymers used as oral delivery carriers are limited widely due to the lack of pH sensitivity and mucoadhesivity [19]. To address these challenges, the development of multi-functional intelligent nanocarriers has gained vast attention. The block copolymer poly(methyl methacrylate-co-methacrylicacid)-b-poly(2-amino ethyl methacrylate) poly(MMA-co-MAA)-b-PAEMA with mucoadhesivity and pH-sensitivity has been successfully synthesized and used as stimuli-responsive carriers for insulin delivery and controlled release [29]. It is still a challenge to effectively develop stimuli-responsive PMs for drug delivery and controlled release with desired properties. This is because lots of time, financial and human resources are used in the design, synthesis and characterization of drug delivery systems, such as repeated synthesis of undesired stimuli-responsive copolymer
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