The influence of molecular weight and arm number of star polymers on the buildup and pH-dependent morphology changes of multilayer films assembled from star poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) and linear poly(styrenesulfonate) (PSS) was systematically investigated. Well-defined star PDMAEMA, consisting of β-cyclodextrin (CD) core and different arm number (21, 14, and 7) were successfully synthesized via atom transfer radical polymerization (ATRP). It is found that star polymers with certain arm number deposit more mass with the increase of molecular weight. As for the star polymers with almost the same arm length but different arm number, film assembled from 14-arm star PDMAEMA exhibits the fastest growth and the most significant morphology changes upon the pH 2.75 treatment. It is assumed that the interdiffusion of PSS controlled by star PDMAEMA with different structures should be responsible for the different buildup and pH-dependent morphology changes of the multilayer films.
Star-shaped copolymers based on star-shaped poly (L-lactide) (s-PLLA) and tocopheryl polyethylene glycol 1000 succinate (TPGS) (s-PLLA-TPGS) were synthesized with structural variation on arm numbers in order to investigate the relationship between the arm numbers of s-PLLA-TPGS copolymers and their micelle properties. The structure and M w of s-PLLA-TPGS were characterized with 1 H NMR, GPC, DSC, and XRD. The indometacin(IMC)-loaded s-PLLA-TPGS micelles were obtained by dialysis method. The effects of arm numbers of s-PLLA-TPGS copolymers on surface morphology, particle size, zeta potential, drug loading content (LC), drug encapsulation efficiency (EE), and in vitro drug release behavior of prepared micelles were studied. The results indicated that the average diameters, LC, and EE of IMC-loaded s-PLLA-TPGS micelles gradually increased in the order of 4-arm, 5-arm, and 6-arm s-PLLA-TPGS copolymers. The in vitro release studies showed that the IMC accumulative release can be decreased by increasing the arm numbers of the s-PLLA-TPGS copolymers, and the release profiles of IMC from the s-PLLA-TPGS copolymers followed the Baker-Lonsdale model equation. The results suggest that the arm number regulation of s-PLLA-TPGS copolymers can provide a new strategy for designing drug carriers of high efficiency.
Graphical abstract
Yong Shen,Shusheng Zhang,Yaoming Wan,Wenxin Fu,Zhibo Li
A second or fourth generation dendrimer with primary amine as the peripheral terminal group was first synthesized via Michael addition and thiol–yne addition. A series of star-shaped polypeptides was synthesized by ring opening polymerization (ROP) of γ-(2-(2-methoxyethoxy)ethyl) L-glutamate (L-EG2Glu) N-carboxyanhydride (NCA) using the amine group terminated dendrimer as the initiator. Taking advantage of the well-defined dendrimer and ROP, the arm number and arm length can be easily controlled. These star-shaped poly(L-EG2Glu) can spontaneously form hydrogels instead of micelles in water at low concentration. The critical gelation concentration (CGC) and hydrogel strength displayed a stronger dependence on arm numbers than the arm length under similar conditions. These properties can be easily modulated by varying the poly(L-EG2Glu) arm length and arm number. The hydrogels showed shear thinning and rapid recovery properties. TEM and AFM characterization revealed that the hydrogel networks were constituted by entangled and branched fibrils.
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