3290
Biomacromolecules 2010, 11, 3290–3293
Biocatalytic Synthesis and in Vitro Release of Biodegradable
Linear Polyesters with Pendant Ketoprofen
Hai-Yang Wang, Wei-Wei Zhang, Na Wang,* Chao Li, Kun Li, and Xiao-Qi Yu*
Key Laboratory of Green Chemistry & Technology, Ministry of Education, College of Chemistry,
Sichuan University, Chengdu 610064, P. R. China
Received June 25, 2010; Revised Manuscript Received October 13, 2010
Enzyme-catalyzed polycondensation for the synthesis of polyester prodrugs of ketoprofen was reported. Lipase
acrylic resin from Candida antarctica (CAL-B) was used to synthesize the linear polyesters with pendent ketoprofen
groups based on ketoprofen glycerol ester, poly(ethylene glycol), and divinyl sebacate. The products were
characterized by GPC and 1H NMR. The results indicated that the molecular weight and yields of the polyesters
depend on experimental conditions such as temperature and feed ratio. The in vitro study showed that the drug
release from the polyester was slow under physiological conditions, which indicated that the polyester could be
a promising prodrug with extended pharmacological effects by delayed release of ketoprofen.
preparation of the polyester prodrug of ketoprofen. The in vitro
study showed that the polyester can release ketoprofen ef-
fectively under physiological conditions, which indicated that
the polyester could be a promising prodrug.
1. Introduction
Ketoprofen is an important 2-Arylpropionic acid class of
nonsteroidal anti-inflammatory drugs (NSAIDs), which is widely
used in the treatment of pain and inflammation under many
conditions.1 However, the long-term use of NSAIDs may cause
some side effects such as gastrointestinal irritation (GI),
bleeding, and ulceration. The prodrug of NSAIDs for tempo-
rarily masking the carboxylic group of NSAIDs is promising
to reduce or abolish the GI toxicity due to the localized effect.2
2. Experimental Section
2.1. Materials. Lipase from acrylic resin from Candida antarctica
(CAL-B), lipase from porcine pancreas (PPL), glycerol, and PEG were
purchased from Sigma-Aldrich. Ketoprofen was obtained from Wuhan
Gang Zheng Biology Technology (China). Ketoprofen vinyl ester was
synthesized and purified as described by Wang et al.9 Divinyl sebacate
was synthesized according to the literature.10 All other chemicals used
in this work were of analytical grade and were first dried over 3 Å
molecular sieves for 24 h prior to use.
In recent years, polymeric prodrugs have gained prominence
in the pharmaceutical field. Conjugating of drugs to polymers
and their modification through the formation of covalent bonds
such as ester or amide should be relatively stable to prevent
drug release during its transport before the cellular localization
of the drug.3 Polymeric prodrugs of NSAIDs have been
developed to reduce gastrointestinal side effects and improve
delivery problems such as solubility and release rate.4 Among
synthetic polymer, poly(ethylene glycol) (PEG) has been the
lead polymer for drug conjugation because of its well-known
low toxicity and good biocompatibility. Choi et al. reported that
ketoprofen-PEG conjugates could be a promising prodrug with
extended pharmacological effects by delayed release.5 However,
the poor drug-loading capacity accompanying the available
methoxy or diol forms of PEG presents a crucial limitation in
the case of low-molecular-weight drug PEG conjugates.6
Moreover, most of polymeric prodrugs have been prepared by
chemical polymerization, which often used toxic catalyst and
harsh reaction conditions.
1
2.2. Instrumental Methods. H NMR and 13C NMR spectra were
obtained on a Bruker DMX 400. Spectra were run in CDCl3 and
referenced to an internal TMS standard. Electrospray ionization (ESI)
mass spectrometry experiments were performed on Bruker Daltonics
Bio TOF mass spectrometer. The quantitative analysis of samples was
made by HPLC on a reverse phase column (Welchrom-C18, 5 µm, 4.6
× 150 mm, Welchrom) using a Shimadzu LC-2010AHT apparatus
equipped with a UV detector at 254 nm. For the analysis of ketoprofen,
methanol/water 70:30 (v/v) was used as eluent (flow rate, 0.8 mL/min).
Gel permeation chromatography (GPC) analyses of the copolymer
molecular weight and its distribution were performed on an Agilent-
1100 system consisting of 5 µm × 10 000 Å and 5 µm × 100 Å PLgel
columns and a refractive index detector. The eluting solvent was
tetrahydrofuran at a flow rate of 1.0 mL/min at 35 °C. The retention
times were calibrated against polystyrene standards.
2.3. Synthesis of 1-O-Ketoprofen Glycerol Ester. The typical
reaction mixture consisted of 15 mmol ketoprofen vinyl ester, 15 mmol
of glycerol, 100 mg of CAL-B, and 25 mg/mL of 3 Å molecular sieves
in 50 mL of acetone. The mixtures were refluxed at 70 °C for 12 h.
Then, the reaction mixture was filtered and the organic solvent was
removed in vacuum. All reactions were detected by thin layer
chromatography (TLC) plates using petroleum ether/ethyl acetate
(3:1, v/v) as eluent. 1-O-Ketoprofen glycerol ester: Yellow liquid (yield:
48.5%). 1H NMR (CDCl3, ppm): 7.82-7.43 (m, 9H, ph-H), 4.23-4.13
(m, 2H, -CH2), 3.91-3.85 (m, 2H, -CH), 3.59-3.47 (m, 2H, -CH2),
1.55 (d, J ) 7.2 Hz, 3H, -CH3). 13C NMR (CDCl3, ppm): 196.7 (CO-
ph), 174.2 (CHCO), 140.9, 137.7, 137.1, 132.7, 131.7, 129.9, 128.5
(-CH), 70.0 (-CH), 65.5 (-CH2), 63.2 (-CH2), 45.0 (-CH), 18.3
(-CH3). ESI-MS (m/z) calcd. for [M+Na], 351.1208; found, 351.1201.
An enzyme can act as a powerful catalyst for the production
and chemical recycling of green and sustainable polymers.
Enzyme-catalyzed synthesis of biodegradable polyesters has
been developed as a novel methodology that has received much
attention owing to its environmentally benignness, energy
savings, atom economy, and so on.7 Recently, Kobayashi and
Makino reviewed the enzymatic polymer synthesis, which may
provide an opportunity for conducting green polymer chemistry.8
Herein we report the enzyme-catalyzed polycondensation of
divinyl sebacate, PEG, and ketoprofen glycerol ester for the
* To whom correspondence should be addressed. E-mail: xqyu@tfol.com.
Tel: +86 28 85460576. Fax: +86 28 85415886.
10.1021/bm100712k
2010 American Chemical Society
Published on Web 11/05/2010