Abstract
The self-assembly of pH-responsive random and block copolymers composed of 2-(N,N-diisopropylamino)ethyl methacrylate and 2-methacryloyloxyethyl phosphorylcholine was investigated in aqueous media. Their pH-responsive behaviors were investigated in aqueous media by dynamic light scattering (DLS) and fluorescence measurements using a pyrene hydrophobic fluorescence probe. In an acidic environment, these copolymers existed as single polymer chains that did not interact with each other. In contrast, upon increasing the pH of the solution above the critical value of ~8, separated micelles were formed in the mixture, which was indicated by bimodal distribution in DLS results with radius of 4.5 and 10.4 nm, corresponding to the random and block copolymer micelles, respectively. Fluorescence resonance energy transfer efficiencies were near to zero in the mixture of the donor labeled block and acceptor labeled random copolymers under both acidic and basic pH. These results demonstrated the coexistence of two distinct micelles.
Highlights
Amphiphilic polymer micelles have been reported to serve as carriers for the delivery of hydrophobic drugs to targeted tissues [1,2,3,4,5,6]
These results indicated that the presence of poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) blocks in the aggregates contributed to strengthen the binding of PMPC40-b-PDPAEMA70 to the cell membranes
The mole percent of DPAEMA in the random copolymer was estimated to be 50 mol% using the integral intensity ratio of the methylene protons at 3.14 and 3.80 ppm derived from the DPAEMA and methacryloyloxyethyl phosphorylcholine (MPC) units, respectively
Summary
Amphiphilic polymer micelles have been reported to serve as carriers for the delivery of hydrophobic drugs to targeted tissues [1,2,3,4,5,6]. The size of the aggregates produced from PEO122-b-DPAEMA43 and PHPMA64-b-PDPAEMA72 was smaller than that of PMPC40-b-PDPAEMA70, the former polymer aggregates were internalized in cancer cells to a lower extent as compared to healthy cells than the latter These results indicated that the presence of PMPC blocks in the aggregates contributed to strengthen the binding of PMPC40-b-PDPAEMA70 to the cell membranes. Cell viability tests evidenced that these nanoparticles did not show any significant toxicity to telomerase-immortalized rhesus fibroblasts and HeLa cells and were, suitable for biomedical applications In this context, copolymers containing 2-methacryloyloxyethyl phosphorylcholine (MPC) have been widely investigated as biomaterials [13,14,15,16,17]. The polymers containing a PMPC block or MPC units maintain their highly hydrophilic character over a wide range of aqueous solution conditions
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