944 The Polymer Society of Korea www.springer.com/13233 pISSN 1598-5032 eISSN 2092-7673 Macromolecular Research, Vol. 20, No. 9, pp 944-953 (2012) Physicochemical Characterizations of Amphiphilic Block Copolymers with Different MWs and Micelles for Development of Anticancer Drug Nanocarriers Jeong Min Yun 1 , So-young Park 2 , Eun Sung Lee 3 , Yu Seok Youn 4 , Ga Young Park 1 , Chaemin Lim 1 , Beom-Jin Lee 5 , Ho-Taek Song 6 , Young Taik Oh * ,6 , and Kyung Teak Oh * ,1 1 College of Pharmacy, Chung-Ang University, Seoul 155-756, Korea 2 Department of Pharmacognosy, College of Pharmacy, Dankook University, Chungnam 330-714, Korea 3 Division of Biotechnology, The Catholic University of Korea, Gyeonggi 420-743, Korea 4 College of Pharmacy, SungKyunKwan University, Gyeonggi 440-746, Korea 5 Bioavailability Control Laboratory, College of Pharmacy, Ajou University, Gyeonggi 443-749, Korea 6 Department of Radiology and Research Institute of Radiological Science, College of Medicine, Yonsei University, Seoul 120-752, Korea Received September 19, 2011; Revised December 15, 2011; Accepted January 2, 2012 Abstract: Biocompatible polymers have been of considerable interest in developing drug delivery systems (DDSs). However, physicochemical characterizations of the polymers and DDSs had been limited because of the difficulty in obtaining the same synthesized copolymers and achieving a similar drug loading ability with the differing prop- erties of the drugs. Therefore, a correlational study of the relationships between copolymers and DDSs was required to estimate the properties of the DDSs and to develop optimal systems of delivery depending on the drug. In this study, we presented several relationship correlation equations of physicochemical properties and copolymers according to their molecular weights (MWs) using amphiphilic block copolymers composed of poly(L-lactide)- block-methoxy-poly(ethylene glycol) (PLA-b-mPEG). The PLA-b-mPEG was characterized by nuclear magnetic resonance and gel permeation chromatography, and the critical micelle concentration (CMC), sizes, and drug load- ing capacity (DLC) of the self-assembling micelles from the copolymers with different MWs were all measured. The increase in MW of the PLA led to a decrease in CMC and DLC with an increase of the particle sizes. The relationship between the MW of the PLA and the physicochemical properties of the micelles demonstrated a good correlation, which provides excellent information for the use in the development of tailor-made DDSs based on copolymers pur- suing optimal particle size, DLC, CMC, and so on. Keywords: amphiphilic block copolymer, polymeric micelles, correlation equation, PLA-b-mPEG, nano-sized drug carrier, anticancer drugs. Introduction Various drug delivery systems (DDS) including nano/ microparticles, liposomes, conjugated prodrugs, micelles, and hydrogels have attracted much interest to many formu- lation researchers because of the peculiar properties of each DDS. 1-5 DDS are studied to increase drugs’ solubility, mini- mize side effects and toxic adjuvants, control drug release into specific tissues, and enhance drug activity. Among var- ious drug carriers, polymeric micelles have been studied as nanosized carriers for hydrophobic drugs such as anticancer agents because of several advantages including simple prep- aration, high drug loading capacity, small size, controlled drug release, flexibility in surface modification, and various functionalities. 4,6-9 The polymeric micelles can be formed by self-assembly from amphiphilic block copolymer composed of hydrophobic and hydrophilic blocks above the critical micelle concentration (CMC) and solubilizing hydrophobic compounds into the micelle core (Scheme I(a)). Mainly, poly(ethylene glycol) (PEG) is usually used as a hydrophilic block. PEG is a biocompatible water-soluble polymer, which is widely used in the biopharmaceutical industry because of its excellent water solubility, chain mobility, and non-immu- nogenicity. PEG is non-toxic and can be cleared from the body through renal ltration due to its molecular weights (MW) of less than 30 kDa. 10 When it comes to a hydrophobic poly- mer, it is also highly biocompatible, non-toxic, and eco- nomic with versatile functional groups such as hydroxyl, carboxyl, amino, and thiol groups. Such a variety of func- DOI 10.1007/s13233-012-0133-z *Corresponding Authors. E-mails: kyungoh@cau.ac.kr or oytaik@yuhs.ac