PEG-b -Pt BA-b -PHEMA well-defined amphiphilic triblock copolymer: Synthesis, self-assembly, and application in drug delivery

Self-Assembly of Linear Amphiphilic Pentablock Terpolymer PAAx-PS48-PEO46-PS48-PAAxin Dilute Aqueous Solution

A series of linear amphiphilic pentablock terpolymer PAA_x-b-PS₄₈-b-PEO₄₆-b-PS₄₈-b-PAA_x (A_xS₄₈O₄₆S₄₈A_x) with various lengths x of the PAA block (x = 15, 40, 60, and 90) were synthesized via a two-step atom transfer radical polymerization (ATRP) using Br-poly(ethylene oxide)-Br (Br-PEO₄₆-Br) as the macroinitiator, styrene (St) as the first monomer, and tert-butyl acrylate (tBA) as the second monomer, followed with the hydrolysis of PtBA blocks. The A_xS₄₈O₄₆S₄₈A_x pentablock terpolymers formed micelles in dilute aqueous solution, of which the morphologies were dependent on the length x of the PAA block. Cryogenic transmission electron microscopy (cryo-TEM), dynamic light scattering (DLS), and zeta potential measurement were employed to investigate the morphologies, chain structures, size, and size distribution of the obtained micelles. The morphology of A_xS₄₈O₄₆S₄₈A_x micelles changed from spherical vesicles with ordered porous membranes to long double nanotubes, then to long nanotubes with inner modulated nanotubes or short nanotubes, and finally, to spherical micelles or large compound vesicles with spherical micelles inside when x increased from 15 to 90. The hydrophobic PS blocks formed the walls of vesicles and nanotubes as well as the core of spherical micelles. The hydrophilic PEO and PAA block chains were located on the surfaces of vesicle membranes, nanotubes, and spherical micelles. The PAA block chains were partially ionized, leading to the negative zeta potential of A_xS₄₈O₄₆S₄₈A_x micelles in dilute aqueous solutions.

Thermoresponsive P(HEMA-co-OEGMA) copolymers: synthesis, characteristics and solution behavior

Random, thermoresponsive copolymers of 2-hydroxyethyl methacrylate (HEMA) and oligo(ethylene glycol) methyl ether methacrylate M _n = 300 (OEGMA) were synthesized via atom transfer radical polymerization (ATRP) in a DMSO/H₂O solvent mixture. Reactivity ratios were determined by the extended Kelen-Tudos method and found to be close to 1. Studies confirmed the randomness of the obtained copolymers. The thermoresponsiveness in water and in phosphate buffer (PBS) solutions and the influence of copolymer composition and solution concentration on the cloud point temperature (T _cp) were investigated. Phase transitions in water solutions were reversible and narrow. The response of P(HEMA-co-OEGMA) to temperature could be adjusted in the range from 66.5 °C to 21.5 °C by changing the HEMA content. In PBS solutions, significant differences in the heating/cooling cycle were observed for all investigated concentrations. The presence of kosmotropic salts in PBS decreased the T _cp value and caused thermal aggregation of chains to form a macroscopic aggregate at temperatures above the T _cp.

Synthesis of drug-crosslinked polymer nanoparticles

A new kind of drug-crosslinked polymer nanoparticle was synthesized. The nanoparticles were composed by a phenylboronic acid modified 10-hydroxycamptothecin (the crosslinker) and 1,2-diol-rich PEG-PGMA diblock copolymer (the backbone), and crosslinked by phenylboronic ester bond.

Polymer–paclitaxel conjugates based on disulfide linkers for controlled drug release

Controlled drug delivery system based on hydrophilic diblock copolymer covalently linked paclitaxel (PTX) via a disulfide linker.

Self-repairing nonfouling polyurethane coatings via 3D-grafting of PEG-b-PHEMA-b-PMPC copolymer

Long-lasting nonfouling polyurethane coatings via 3D-grafting of a triblock copolymer showed inhibition ability for the adhesion of protein and human platelets.

Poly(ethylene oxide)-block-polyphosphoester-graft-paclitaxel conjugates with acid-labile linkages as a pH-sensitive and functional nanoscopic platform for paclitaxel delivery

There has been an increasing interest to develop new types of stimuli-responsive drug delivery vehicles with high drug loading and controlled release properties for chemotherapeutics. An acid-labile poly(ethylene oxide)-block-polyphosphoester-graft-PTX drug conjugate (PEO-b-PPE-g-PTX G2) degradable, polymeric paclitaxel (PTX) conjugate containing ultra-high levels of PTX loading is improved significantly, in this second-generation development, which involves connection of each PTX molecule to the polymer backbone via a pH-sensitive β-thiopropionate linkage. The PEO-b-PPE-g-PTX G2 forms well-defined nanoparticles in an aqueous solution, by direct dissolution into water, with a number-averaged hydrodynamic diameter of 114 ± 31 nm, and exhibits a PTX loading capacity as high as 53 wt%, with a maximum PTX concentration of 0.68 mg mL(-1) in water (vs 1.7 μg mL(-1) for free PTX). The PEO-b-PPE-g-PTX G2 shows accelerated drug release under acidic conditions (≈50 wt% PTX released in 8 d) compared with neutral conditions (≈20 wt% PTX released in 8 d). Compared to previously reported polyphosphoester-based PTX drug conjugates, PEO-b-PPE-g-PTX G1 without the β-thiopropionate linker, the PEO-b-PPE-g-PTX G2 shows pH-triggered drug release property and 5- to 8-fold enhanced in vitro cytotoxicity against two cancer cell lines.

Contribution of hydrophobic/hydrophilic modification on cationic chains of poly(ε-caprolactone)-graft-poly(dimethylamino ethylmethacrylate) amphiphilic co-polymer in gene delivery

Nanoparticles (NPs) assembled from amphiphilic polycations have been certified as potential carriers for gene delivery. Structural modification of polycation moieties may be an efficient route to further enhance gene delivery efficiency. In this study two electroneutral monomers with different hydrophobicities, 2-hydroxyethyl methacrylate (HEMA) and 2-hydroxyethyl acrylate (HEA), were incorporated into the cationic poly(dimethylamino ethyl methacrylate) (PDMAEMA) side-chains of amphiphilic poly(ε-caprolactone)-graft-poly(dimethylamino ethylmethacrylate) (PCD) by random co-polymerization, to obtain poly(ε-caprolactone)-graft-poly(dimethylamino ethyl methacrylate-co-2-hydroxyethyl methacrylate) (PCD-HEMA) and poly(ε-caprolactone)-graft-poly(dimethylamino ethyl methacrylate-co-2-hydroxyethyl acrylate) (PCD-HEA). Minimal HEA or HEMA moieties in PDMAEMA do not lead to statistically significant changes in particle size, zeta potential, DNA condensation properties and buffering capacity of the naked NPs. However, the incorporation of HEMA and HEA lead to reductions and increases, respectively, in the surface hydrophilicity of the naked NPs and NPs/DNA complexes, which was confirmed by water contact angle assay. These simple modifications of PDMAEMA with HEA and HEMA moieties significantly affect the gene transfection efficiency on HeLa cells in vitro: PCD-HEMA NP/DNA complexes show a much higher transfection efficiency than PCD NPs/DNA complexes, while PCD-HEA NPs/DNA complexes show a lower transfection efficiency than PCD NP/DNA complexes. Fluorescence activated cell sorter and confocal laser scanning microscope results indicate that the incorporation of hydrophobic HEMA moieties facilitates an enhancement in both cellular uptake and endosomal/lysosomal escape, leading to a higher transfection efficiency. Moreover, the process of endosomal/lysosomal escape confirmed in our research that PCD and its derivatives do not just rely on the proton sponge mechanism, but also on membrane damage due to the polycation chains, especially hydrophobic modified ones. Hence, it is proved that hydrophobic modification of cationic side-chains is a crucial route to improve gene transfection mediated by polycation NPs.

Poly(ethylene oxide) (PEO)-based ABC triblock terpolymers – synthetic complexity vs. application benefits

This review presents a short summary of possible synthetic routes for the synthesis of poly(ethylene oxide) (PEO) containing triblock terpolymers, as well as different applications in the bulk or in solution – including the preparation of porous materials, hybrid systems, and carriers for controlled drug delivery.