A novel of pH-sensitive amphiphilic block copolymer poly(isobutyl acrylate-co-crylic acid)-b-poly-(2-hydroxypropyl acrylate)(P(IBA-co-AA)-b-PHPA) was synthesized by reversible addition fragmentation chain transfer radical (RAFT) polymerization.The block copolymer was characterized by Fourier transform infrared spectroscopy (FTIR)

1H nuclear magnetic resonance (1H-NMR) and gel permeation chromatography (GPC).Nanosized micelles were formed by self-assembly when the P(IBA-co-AA)-b-PHPA was dissolved in water solution

the critical micelle concentration value was about 2.0 mg/L.These nanosized micelles were characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS).The assembled micelles were regularly spherical in the shape with an average size of ca.100 nm.The diameters of the micelles increased with increasing the pH values were studied by DLS.The drug delivery behaviors of the micelles embedding anti-cancer drug paclitexel (PTX) in a simulated human body environment were studied.The Cell Counting Kit-8 assay (CCK-8) was used to evaluate cytotoxicity of the polymeric micelles.The in vitro antitumor activity was evaluated in human breast carcinoma cell line MCF-7 and human lung adenocarcinoma cell line A-549

then the nanosized micelles used as the carrier of the paclitaxel (PTX) were studied.The in vitro antitumor activity was evaluated in MCF-7 cells and A-549 cells.The results showed that P(IBA-co-AA)-b-PHPA micelles exhibited pH-sensitive behavior because of the presence of AA in the feed.The amphiphilic block copolymer P(IBA-co-AA)-b-PHPA was one of novel and ideal biomaterials as PTX nano-carrier

PTX-loaded micelles presented sustained release profiles and achieved higher anti-tumor activity.It was a promising anti-cancer drug carrier.