Fig. 2. Representative ex vivo fluorescence images of dissected organs and tumor ofmice bearing HepG2 human liver tumors, sacrificed 4 h after intravenous injection ofNile Red-loaded PAMAM1-CA-CIT micelles.

ConclusionA tumor-targeted drug carrier with pH-sensitivity was obtained

from cholic acid and citraconic anhydride functionalized G1 PAMAM.The modified dendrimers can self-assemble and encapsulate hydro-phobic molecules in aqueous solution. Guest molecules entrapped inthe micelles were significantly accumulated in the tumors of tumorbearing mice and the intracellular delivery of guest molecules wasenhanced by pH dependent activation. Therefore, these micellesbased on low generation dendrimers may have potential applicationsfor targeted delivery of anticancer drugs.

AcknowledgmentsThe financial support from the National Natural Science Founda-

tion of China (Grant No. 20574039) and Tianjin Natural ScienceFoundation (Grant No. 07JCYBJC02700) is acknowledged.

References[1] E. Gullotti, Y. Yeo, Extracellularly activated nanocarriers: a new paradigm of tumor

targeted drug delivery, Mol. Pharm. 6 (2009) 1041–1051.[2] L.E. Gerweck, K. Seetharaman, Cellular pH gradient in tumor versus normal tissue:

potential exploitation for the treatment of cancer, Cancer Res. 56 (1996) 1194–1198.[3] Z.X. Zhou, Y.Q. Shen, J.B. Tang, M.H. Fan, E.A. Van Kirk, W.J. Murdoch, M. Radosz,

Charge-reversal drug conjugate for targeted cancer cell nuclear drug delivery, Adv. Funct.Mater. 19 (2009) 3580–3589.

[4] B.G. Hazra, V.S. Pore, S.K. Dey, S. Datta, M.P. Darokar, D. Saikia, S.P.S. Khanuja, A.P.Thakur, Bile acid amides derived from chiral amino alcohols: novel antimicrobials andantifungals, Bioorg. Med. Chem. Lett. 14 (2004) 773–777.

[5] Y. Lee, S. Fukushima, Y. Bae, S. Hiki, T. Ishii, K. Kataoka, A protein nanocarrier fromcharge-conversion polymer in response to endosomal pH, J. Am. Chem. Soc. 129 (2007)5362–5363.

doi:10.1016/j.jconrel.2011.08.147

Synthesis of amphiphilic hyperbranched polymers for thecontrolled release of double-guest molecules

Wei Tian, Xiaoying Wei, Guang Yang, Xiaodong FanDepartment of Applied Chemistry, School of Science,Northwestern Polytechnical University, Xi'an 710072, ChinaE-mail address: happytw_3000@163.com (X. Wei).

Abstract summaryIn order to achieve a controlled release of double-guest

molecules, an amphiphilic hyperbranched polymer consisting of ahydrophobic hyperbranched poly(β-cyclodextrin) core and a hy-drophilic methoxy polyethylene glycol shell was first synthesizedvia click chemistry between azido groups and alkynyl groups. Thenthe controlled release behavior of this polymer with respect todouble-guest molecules including Levofloxacin lactate and Rhoda-mine B was studied by UV. The results showed that controlledrelease of double-guest molecules using the novel polymer carriercan be achieved.

Keywords: Amphiphilic hyperbranched polymer, Click chemistry,Double-guest molecules, Controlled release behavior

IntroductionSynthesis and controlled release behavior of amphiphilic hyper-

branched polymers is one of the most attractive areas in contempor-ary polymer chemistry and shows great potential in biotechnologicaland pharmaceutical fields [1]. These polymers consist of a hyper-branched polymer as the core and external substituent's as the shellhaving solubility's different from the core [1]. Up to date, the releaseof water-soluble dyes or hydrophobic drugs from amphiphilichyperbranched polymers has been studied by several research groups[2]. However, with the development of controlled and targeteddelivery, a single-drug system cannot always satisfy the highdemands, hence, the establishment of a double-drug delivery systemis expected.

In order to fulfill this goal, a novel amphiphilic hyperbranchedpolymer [HBP(β-CD)-g-MPEG] consisting of a hydrophobic hyper-branched poly(β-cyclodextrin) [HBP(β-CD)] core [3] and a hydrophilicmethoxy polyethylene glycol (MPEG) shell was first synthesized viaclick chemistry using azido groups and alkynyl groups. β-CD with ahydrophobic cavity can be employed as a host for a variety of smallermolecular guests via noncovalent interactions [4]. The topographicstructure of hyperbranched polymers also reveals a natural cavity [5].Therefore, it is possible to encapsulate double-guest molecules in onesupramolecular structure, and then release them at predefinedconditions. In order to investigate the controlled release behavior ofHBP(β-CD)-g-MPEG loaded with double-guest molecules, Levoflox-acin lactate (LL) and Rhodamine B (RhB) were selected as guestmolecules based on their different molecular structures and absorp-tion peaks in UV spectra.

Experimental methodsPolymer synthesis. HBP(β-CD)-g-MPEG was synthesized via click

chemistry reaction between azido groups of MPEG-N3 and alkynylgroups of HBP(β-CD)-CCH. The reaction was conducted as follow: ina flask equipped with a magnetic stirrer, HBP(β-CD)-CCH (0.1 g),MPEG-N3 (1.57 g), CuBr (147 mg) and N,N,N′,N″,N″-pentamethyldiehylenetriamine (PMDETA) (163 mg) were first dissolved in DMF(4 mL). The mixed solution was bubbled with nitrogen gas for45 min, and sealed under vacuum. The reaction was conducted at80 °C for 2 days, and then, the mixture was dialyzed in a dialysisbag (molecular weight cut off: 3500) against distilled water for7 days. It was refreshed at an interval of 12 h. The dialyzed productwas lyophilized and kept in glassware under vacuum for furthercharacterization.

Investigation of the controlled release behavior. Sample slicesincluding polymer and two guest molecules LL and RhB were sealedseparately using a dialysis bag (molecular weight cut off: 3500) with4 cm in length. The bags were immersed into 40.0 mL of a buffersolution with pH=7.4 and 0.1 mol/L ionic strength at 37 °C. In acertain time interval, 5.0 mL of buffer solution was withdrawn andreplaced with 5.0 mL of fresh one. All solutions withdrawn were keptat 37 °C for 2 days prior to measurements. All release measurementswere carried out in triplicate for each sample, and an average valuewas adopted. The cumulative release was calculated by using Eq. (1)as follows:

Cumulative release %ð Þ ¼ 100� 40:0Cn þ 5:0∑Cn−1ð ÞW0

ð1Þ

where W0 (mg) is weight of drug in the polymer; Cn (mg/ml) is theconcentration of LL or RhB in buffer solution, which was withdrawnfor n times, Cn−1 (mg/ml) is the concentration of LL or RhB in buffersolution, which was withdrawn for n−1 times.

Abstracts / Journal of Controlled Release 152 (2011) e1–e132 e97

Results and discussionTo investigate the controlled released behavior of HBP(β-CD) in

aqueous solution, MPEG segments were incorporated onto theperipheries of HBP(β-CD) to obtain amphiphilic hyperbranchedpolymer HBP(β-CD)-g-MPEG. PEG was used to prepare the amphi-philic hyperbranched polymer due to its good water-solubility andgood biocompatibility in drug delivery systems [6].The syntheticroute for HBP(β-CD)-g-MPEG is shown in Scheme 1. It can be seenfrom Scheme 1, that HBP(β-CD)-g-MPEG was synthesized via clickchemistry reaction between azido groups of MPEG-N3 and alkynylgroups of HBP(β-CD)-CCH. The results of 1H NMR and 13C NMRindicated that the structure of the resulting polymer was inaccordance with the expected structure.

HBP(β-CD)O

O

OO

OO

O O

OOO

O

OO

OO

O

OO

O

NH

NH

NHNH

HN

HN

NH

HN HN

HNO

ONH

C

O

CH2N3 CH3(CH2CH2O)nODMF,CuBr,PDMETA

48h,T=80 oC

NH

N

NN

CH2 C

O

O

HBP(β-CD)

Scheme 1. Synthesis of amphiphilic hyperbranched polymer [HBP(β-CD)-g-MPEG].

The release profiles of LL and RhB are shown in Figs. 1 and 2respectively. Figs. 1 and 2 show that no significant burst releasetook place, either from LL-loaded or from RhB-loaded samples ofdouble-guest molecule loaded systems. Furthermore, sustainedrelease of LL or RhB was observed when the release took placefrom the double-guest molecule system. In case of release fromsystems only loaded with one guest molecule the release rate washigher and almost constant. The difference in the behavior of thesesystems may be mainly attributed to the presence of two guests inthe different molecular cavities in one system versus the presenceof only one guest in the other system. In the first system inter-action among different guest molecules and polymer cavities mayplay a role.

0 2 4 6 8 10 12 14

0

20

40

60

80

100

single-guest system multi-guest system

Cum

ulat

ive

Rel

ease

(%

)

Time (h)

RhB

Fig. 2. Release profiles of RhB from HBP (β-CD)-g-MPEG as a function of time at 37 °C.

ConclusionAmphiphilic hyperbranched polymer consisting of a hydrophobic

hyperbranched poly(β-cyclodextrin) core and a hydrophilic methoxypolyethylene glycol shell can be synthesized via click chemistrybetween azido groups and alkynyl groups. Furthermore, the releaserates of double-guest molecules including Levofloxacin lactate andRhodamine B from this polymer carrier can be obviously controlled.Therefore, these research results may be helpful to extend theapplication of CD-based hyperbranched polymers in complex drugdelivery systems.

AcknowledgmentsThis work is supported by China Postdoctoral Science Foundation

funded project (No. 20090461307), Natural Science Basic ResearchPlan in Shanxi Province of China (No. 2010JQ2002) and NPUFundamental Research Foundation (No. JC200920).

References[1] T. Satoh, Unimolecular micelles based on hyperbranched polycarbohydrate coresSoft

Matter 5 (2009) 1972–1982.[2] W. Tian, X.D. Fan, J. Kong, Y.Y. Liu, T. Liu, Y. Huang, Novel supramolecular system of

amphiphilic hyperbranched polymer with β-cyclodextrin and hyperbranched topographycavities: synthesis and selective encapsulation, Polymer 51 (2010) 2556–2564.

[3] W. Tian,X.D. Fan, J. Kong, T. Liu,Y.Y. Liu, Y. Huang, S.J. Wang,G.B. Zhang, Cyclodextrin-basedhyperbranched polymers: molecule design, synthesis and characterization,Macromolecules42 (2009) 640–651.

[4] V.T. D'Souza, K.B. Lipkowitz, Cyclodextrins: introduction, Chem. Rev. 98 (1998)1741–1742.

[5] C. Gao, D.Y. Yan, Hyperbranched polymers: from synthesis to applications, Prog. Polym.Sci. 29 (2004) 183–275.

[6] I. Koji, F. Taiichi, Synthesis of functionalized poly(ethylene oxide) macromonomers,Polymer 42 (2001) 7233–7236.

doi:10.1016/j.jconrel.2011.08.148

In vitro and in vivo evaluation of ibuprofen–paeonol conjugate

Dan Wu, Guizhen Ao, Qingri Cao, Dawei Chen, Jinghao CuiDepartment of Pharmaceutics, School of Pharmacy,Medical College of Soochow University, Suzhou 215123, ChinaE-mail address: jhcui@suda.edu.cn (J. Cui).

Abstract summaryIbuprofen is one of the widely used non-steroidal anti-inflamma-

tory drugs (NSAIDs) for the treatment of rheumatoid arthritis.However, the potential of causing adverse effects limits its furtherclinical application. Therefore, a novel ibuprofen–paeonol conjugate(IPC) was synthesized by esterification to improve the therapeuticefficacy and decrease the gastrointestinal (GI) tract irritation ofibuprofen. The systemic evaluations of IPC were carried out including

302514131211109876543210

0

20

40

60

80

100

single-guest system multi-guest system

Cum

ulat

ive

Rel

ease

(%

)

Time (h)

LL

Fig. 1. Release profiles of LL from HBP (β-CD)-g-MPEG as a function of time at 37 °C.

Abstracts / Journal of Controlled Release 152 (2011) e1–e132e98