Block Copolymers of Polyacrilamide and Poly(ethylene oxide) as Nanocarriers for Drug Delivery: Micellization and Bulk Structure (original) (raw)
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Micellar structures of PAAc/PAAm block copolymers in the processes of doxorubicin encapsulation
Molecular Crystals and Liquid Crystals, 2018
Micelle formation of asymmetric block copolymers PAAc-b-PAAm (DBC) and PAAm-b-PAAc-b-PAAm (TBC) comprised poly(acrylic acid) and polyacrylamide were investigated. A steady increase in the critical micellization concentration and the Gibbs free micellization energy of the block copolymers at PAAm block lengthening was observed in every series, thus implying the growth of micelle stability. The existence of two morphological forms of micelles was found and discussed. The encapsulation capability of DBC and TBC micelles with respect to doxorubicin (Dox) is reduced at the increase in PAAm block length. The decrease in the Dox encapsulation degree at the pH lowering is stipulated by a strong stabilization of micellar structures.
Micellization of asymmetric triblock copolymers (TBCs) contained chemically complementary poly(ethylene oxide) (M n = 6, 14 and 35 kDa) and polyacrylamide of different chain length (PAAm-b-PEO-b-PAAm) was studied using visible spectroscopy, static light scattering, photography and transmission electron microscopy. The formation of ''hairy-type'' and ''flower-like'' micelles consequently in aqueous and aqueous/ethanol (30/70 v/v) solutions was established. An unusual morphology of the ''hairy-type'' micelles was found in aqueous solutions of TBC, which comprised the lengthiest PEO and PAAm blocks. Significant encapsulation of a model crystalline drug prednisolon (PS) by the ''hairy'' micelles due to hydrogen bonds and hydrophobic interactions was determined by ultraviolet-visible spectroscopy and Fourier transform infrared spectroscopy. This resulted in the appearance of ''snow-flakes-like'' micellar structures. The possibility of regulating crystalline properties of the drug in micellar nanocontainers was shown with differential scanning calorimetry and wide-angle X-ray scattering.
Molecular Crystals and Liquid Crystals, 2011
The micellization of asymmetric diblock copolymers (DBC) MePEG-b-PAAm formed by monomethoxy-poly(ethylene)oxide (MePEG) and polyacrylamide (PAAm) has been studied in water, a water=alcohol mixture, and a NaCl solution. The effect of added NaCl on the critical micellization concentration of DBC water solutions was examined. The interaction between DBC and antitumor drug doxorubicin is discussed. The analysis of the UV spectrum of doxorubicin is performed.
2012
The micellization of asymmetric PAAm-b-PEO-b-PAAm triblock copolymers (TBCs) with increasing length of chemically complementary polyacrylamide and poly(ethylene oxide) blocks was studied using static light scattering, photography, UV-Vis spectroscopy and TEM. The formation of “hairy-type” and “flower-like” micelles was established in dilute aqueous and aqueous/ethanol solutions. The “hairy” micelles contained a “core” comprised cooperatively interacting PEO and PAAm segments and “corona” formed by unbound units of longer PAAm blocks. Appearance of the “flower-like” micelles was conditioned by insolubility of PAAm blocks. Stability of the “flower-like” micelles was higher than that of the “hairy-type” ones. Significant encapsulation of a model drug prednisolon by TBC micelles was established.
2012
Two series of MOPEO-b-PCL diblock copolymers (DBCs) contained methoxypoly(ethylene oxide) (Mn 2.5 and 4.54 kDa) and poly(ε-caprolactone) of a variable Mn and also the triblock copolymer (TBC) PCL-b-PEO-b-PCL based on poly(ethylene oxide) (Mv 6 kDa) were synthesized and characterized by NMR spectroscopy. Their micellization in water/dioxane solutions was studied using static and dynamic light scattering, UV-Vis spectroscopy and TEM. The micelles of spherical and ellipsoidal morphology, which size and stability in a solution (estimated by CMC and-G values) grew with increase in the length of both the "core"-forming (PCL) and "corona"-forming (PEO) blocks, were found in the dilute DBC solutions. Unlike this, the "flower-like" micelles of a smaller size and stability occured in TBC solutions. The prospects for application of DBC and TBC micelles as biocompatible and biodegradable carriers for poorly soluble and anticancer drugs (prednisolon, doxorubicin etc.) were considered.
Materialwissenschaft und Werkstofftechnik, 2011
Using differential scanning calorimetry, the structure of the diblock copolymer (DBC)MePEO‐b‐PAAm was determined. The behaviour of DBCs in water and mixed solvents was investigated. It is shown that adding of dimethyl formamide to DBC water solutions leads to destruction of the H‐bonds network between the PAAm and MePEO blocks. The tendency of DBCs to micellization in water/ethanol mixture depends on the length of MePEO block and grows with increasing molecular weight of MePEO and PAAm.
Biomacromolecules, 2011
This study aimed to optimize poly(ethylene glycol)-b-poly(εcaprolactone) (PEG-b-PCL)-based amphiphilic block copolymers for achieving a better micellar drug delivery system (DDS) with improved solubilization and delivery of doxorubicin (DOX). First, the FloryÀHuggins interaction parameters between DOX and the core-forming segments [i.e., poly(εcaprolactone) (PCL) and poly[(ε-caprolactone-co-γ-(carbamic acid benzyl ester)-ε-caprolactone] (P(CL-co-CABCL))] was calculated to assess the drugÀpolymer compatibility. The results indicated a better compatibility between DOX and P(CL-co-CABCL) than that between DOX and PCL, motivating the synthesis of monomethoxy-poly(ethylene glycol)-b-poly[(εcaprolactone-co-γ-(carbamic acid benzyl ester)-ε-caprolactone] (mPEG-b-P-(CL-co-CABCL)) block copolymer. Second, two novel block copolymers of mPEG-b-P(CL-co-CABCL) with different compositions were prepared via ring-opening polymerization of CL and CABCL using mPEG as a macroinitiator and characterized by 1 H NMR, FT-IR, GPC, WAXD, and DSC techniques. It was found that the introduction of CABCL decreased the crystallinity of mPEG-b-PCL copolymer. Micellar formation of the copolymers in aqueous solution was investigated with fluorescence spectroscopy, DLS and TEM. mPEGb-P(CL-co-CABCL) copolymers had a lower critical micelle concentration (CMC) than mPEG-b-PCL and subsequently led to an improved stability of prepared micelles. Furthermore, both higher loading capacity and slower in vitro release of DOX were observed for micelles of copolymers with increased content of CABCL, attributed to both improved drugÀcore compatibility and favorable amorphous core structure. Meanwhile, DOX-loaded micelles facilitated better uptake of DOX by HepG2 cells and were mainly retained in the cytosol, whereas free DOX accumulated more in the nuclei. However, possibly because of the slower intracellular release of DOX, DOX-loaded micelles were less potent in inhibiting cell proliferation than free DOX in vitro. Taken together, the introduction of CABCL in the core-forming block of mPEG-b-PCL resulted in micelles with superior properties, which hold great promise for drug delivery applications.
Langmuir
The aim of this study was to define a block copolymer micellar system with a high solubilization capacity for poorly soluble aromatic drugs. Ethylene oxide and phenyl glycidyl ether were sequentially polymerized to form the diblock copolymer G 5 E 67 (G) phenyl glycidyl ether, OCH 2 CH(CH 2 OC 6 H 5); E) oxyethylene, OCH 2 CH 2 ; subscripts denote number-average block lengths in repeat units). The association properties in aqueous solution over the range 20-50°C were investigated by surface tensiometry and light scattering, yielding values of the cmc, hydrodynamic radius, and association number; gel boundaries in concentrated micellar solution were investigated by tube inversion. The solubilization capacity of G 5 E 67 for the poorly water-soluble drug griseofulvin was higher than that of a triblock EGE copolymer of longer G block length and considerably higher than that achieved with poloxamers (E m P n E m , P) oxypropylene).