D -amino acids boost the selectivity and confer supramolecular hydrogels of a nonsteroidal anti-inflammatory drug (NSAID)

Article abstract of DOI:10.1021/ja310019x

As systemically used therapeutics for treating acute or chronic pains or inflammations, nonsteroidal anti-inflammatory drugs (NSAIDs) also associate with the adverse gastrointestinal and renal effects and cardiovascular risks. Thus, it is beneficial to develop topical gels that selectively inhibit cyclooxygenase-2 (COX-2) for the management of local inflammation. In this work, we demonstrate that the covalent conjugation of d-amino acids to naproxen (i.e., a NSAID) not only affords supramolecular hydrogelators for the topical gels but also unexpectedly and significantly elevates the selectivity toward COX-2 about 20× at little expense of the activity of naproxen. This work illustrates a previously unexplored approach that employs d-amino acids for the development of functional molecules that have dual or multiple roles and exceptional biostability, which offers a new class of molecular hydrogels of therapeutic agents.

Full text of DOI:10.1021/ja310019x

Subscriber access provided by the Henry Madden Library | California State University, Fresno
Communication
D-Amino Acids Boost the Selectivity and Confer Supramolecular
Hydrogels of a Non-steroidal Anti-inflammatory Drug (NSAID)
Jiayang Li, Yi Kuang, Yuan Gao, Xuewen Du, Junfeng Shi, and Bing Xu
J. Am. Chem. Soc., Just Accepted Manuscript • Publication Date (Web): 08 Nov 2012
Downloaded from http://pubs.acs.org on November 8, 2012
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a free service to the research community to expedite the
dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts
appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been
fully peer reviewed, but should not be considered the official version of record. They are accessible to all
readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered
to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published
in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just
Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor
changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers
and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors
or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
Journal of the American Chemical Society is published by the American Chemical
Society. 1155 Sixteenth Street N.W., Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the course
of their duties.

Page 1 of 5
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
D-Amino Acids Boost the Selectivity and Confer Supramolecular Hy-
drogels of a Non-steroidal Anti-inflammatory Drug (NSAID)
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Jiayang Li, Yi Kuang, Yuan Gao, Xuewen Du, Junfeng Shi and Bing Xu*
Department of Chemistry, Brandeis University, 415 South St., Waltham, MA 02454, USA
Supporting Information Placeholder
hydrogelators) in water,7 have become an attractive choice of
soft nanomaterials8 for a variety of applications, such as scaf‐
ABSTRACT: As systemically used therapeutics for treat‐
folds for tissue engineering,9,10 carriers for drug delivery,11,12
menting acute or chronic pains or inflammations, non‐
steroidal anti‐inflammatory drugs (NSAID) also associate
with the adverse gastrointestinal and renal effects and cardi‐
ovascular risks. Thus, it is beneficial to develop topical gels
ultrathin membranes,13 and new matrices for enzyme assay,14
antibacterial cell culture,10 gel electrophoresis,15 and protein
pull‐down assay.16 Since the hydrogelators only associate
that selectively inhibit cyclooxygenase‐2 (COX‐2) for the
with each other through noncovalent interactions, supramo‐
management of local inflammation. In this work, we demon‐
lecular hydrogels are inherently biocompatible and biode‐
strate that the covalent conjugation of D‐amino acids to
gradable, which also makes them attractive candidates for
naproxen (i.e., an NSAID) not only affords supramolecular
hydrogelators for the topical gels, but also unexpectedly and
significantly elevates the selectivity towards COX‐2 about 20
times at little expense of the activity of naproxen. This work
self‐delivery therapeutics, that is, the drug molecules them‐
selves are hydrogelators.12 Comparing to the use of biode‐
gradable polymers to encapsulate therapeutic agents for con‐
trolled release of drugs by adjusting the pore sizes and func‐
tionality of the polymer networks,17 self‐delivery hydrogels
illustrates a previously unexplored approach that employs D‐
amino acids for the development of functional molecules
based on supramolecular hydrogelators minimize several
inherent shortcomings, such as inflammations,18 limited
that have dual or multiple roles and exceptional biostability,
loading of drug molecules,19 and the difficulties of functional‐
which offers a new class of molecular hydrogels of therapeu‐
tic agents.
izing the polymers with drug molecules, that limit the appli‐
cation of polymeric hydrogels.
Since the formation of supramolecular hydrogels relies on
the small molecules (i.e., hydrogelators) that self‐assemble in
water via non‐covalent interactions and the sustained drug‐
This communication reports the design, synthesis, and
characterization of hydrogelators made of D‐amino acids and
release depends on the biostability of the hydrogels, the es‐
sential requirements for the hydrogelators made of NSAIDs
are (i) enabling the self‐assembly of NSAIDs without com‐
promising the activity of the NSAIDs; (ii) resisting the prem‐
ature degradation due to proteolytic hydrolysis. To satisfy
these two requirements and to demonstrate the concept of
the design, we use one of the prescription NSAIDs, naproxen
(denoted as Npx in this report), to generate new hydrogela‐
tors that only compose of naproxen and small peptides made
of D‐amino acids. Based on the ability of diphenylalanine
(Phe‐Phe)20 motif to enable functional molecules to self‐
assembly in water,21 we conjugate D‐Phe‐D‐Phe with Npx to
afford NSAID containing hydrogelators. The use of D‐amino
acids for the conjugates not only confers proteolytic re‐
sistance to the hydrogelators, but also, unexpectedly and
significantly, enhances the selectivity of the hydrogelators as
the Npx derivatives for inhibiting COX‐2. As the first exam‐
ple of the D‐amino acids to improve the selectivity and to
maintain the desired activity of a therapeutic agent, this
work demonstrated a new approach for improving the selec‐
tivity of clinically used therapeutics and for developing mul‐
tifunctional small molecules that self‐assemble in water to
result in new supramolecular hydrogels of therapeutic agents
that are biostable, target specific, and potent.
a non‐steroidal anti‐inflammatory drug (NSAID) for the de‐
velopment of multifunctional supramolecular hydrogelators
that have excellent selectivity for inhibiting COX‐2. As a
widely, systemically used drugs for the treatment of acute or
chronic pains or inflammations, NSAIDs usually are adminis‐
tered in high dosage, which causes the adverse gastrointesti‐
nal and renal effects1 when they inhibit COX‐1,2 and associate
with cardiovascular risks with the inhibition of COX‐2.2,3
Such paradoxical effects demand the selectivity of NSAID to
be modulated according to the therapeutic objectives, as well
as minimize the systemic use of NSAIDs for localized acute
or chronic pains.4 Therefore, it is clinically beneficial to ex‐
plore gels of NSAIDs as a topical agent for treating inflamma‐
tion and relieving pain, as demonstrated by the use of diclo‐
fenac lotion for managing moderate osteoarthritis.5 The en‐
couraging results of diclofenac lotion indicate that it is
worthwhile to develop gels of other NSAIDs for more effec‐
tive localized treatment of severe chronic pains. Thus, we
choose to develop supramolecular hydrogels of NSAIDs be‐
cause, despite their promising potential, they are less ex‐
plored,6 particularly in term of how to enhance biostability
and maintain desired activity—two essential requirements of
topical gels for sustained release.
Supramolecular hydrogels, as a type of hydrogels resulted
from the self‐assembly of small molecules (usually termed as
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 2 of 5
tion test indicates that all the hydrogelators in Scheme 1 are
1
2
3
4
5
6
7
8
able to form stable hydrogels at the concentration of 0.8 wt%
(Figure 2), but the hydrogels exhibit a slightly different ap‐
pearance. For example, the aid of sonication and heating
affords the aqueous solution of 1 at pH 9.0, which turns into
an opaque hydrogel upon the adjustment of the pH to 4.0 at
room temperature. Unlike the case of 1, the addition of 0.2
U/mL of alkaline phosphatase into the solution of 2P results
in a transparent hydrogel of 2 at pH 7.6. By changing the pH
and temperature, we obtain the hydrogels of 3, 5, and 6, re‐
spectively.25 By adding 0.2 U/mL of alkaline phosphatase into
the solution of 4P, we obtain the hydrogel of 4.
9
Figure 1. The binding of (A) Npx and (B) 1 with COX‐2 en‐
zyme (the ligands as CPK model and the COX‐2 as ribbons).
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Scheme 1. The structures of the hydrogelators consisting
of D‐amino acids and naproxen (Npx).
We design the hydrogelators based on the crystal structure
of COX‐2,22 which suggests that the conjugation of amino
acids to Npx hardly disrupts the binding of Npx to COX‐2.
Figure 1 shows an example of the design. According to the
binding of Npx (red) with COX‐2 enzyme (gray) (Figure 1A),
the carboxylate end of Npx is available for modification after
Npx binds to COX‐2 due to the large open space in the struc‐
ture of COX‐2. Figure 1B shows the predicted binding model
of hydrogelator Npx‐D‐Phe‐D‐Phe (1, Npx‐ff, blue spheres
represent D‐Phe‐D‐Phe) and COX‐2: the connection of a
rather bulky D‐Phe‐D‐Phe dipeptide to Npx still allows the
Npx to bind to the active site of COX‐2. In order to generate
the hydrogels in situ (or in vivo) via enzymatic reactions,23
we introduce D‐tyrosine phosphate to 1. Additionally, we
connect Npx to the side chain of small peptides of D‐amino
acids for evaluating the correlation between the structure
and the activity of the hydrogelators of NSAIDs. Scheme 1
shows the molecular structures of the designed derivatives of
Npx in this work. The connection of D‐Phe‐D‐Phe, D‐Phe‐D‐
Phe‐D‐Tyr, D‐Phe‐D‐Phe‐D‐Lys or D‐Phe‐D‐Phe‐D‐Lys‐D‐
Tyr to Npx results in molecules Npx‐ff (1), Npx‐ffy (2), Npx‐
ffk (3), or Npx‐ffky (4), respectively, that contains Npx at the
backbone of the small peptide. The conjugation of Npx to the
side chain of D‐Phe‐D‐Phe‐D‐Lys or D‐Phe‐D‐Phe‐D‐Lys‐D‐
Tyr via the ε‐amino group of the D‐Lys residue produces
molecules ffk(Npx) (5) and ffk(Npx)y (6). The addition of a
phosphate group on the tyrosine residue of 2 and 4 affords
the precursors (2P and 4P) that would convert to molecules
2 and 4 followed by the dephosphorylation catalyzed by
phosphatases.23,24
Figure 2. The TEM images of the hydrogels of (A) 1 (pH 4.0);
(B) 2 (pH 7.6); (C) 3 (pH 7.6); (D) 4 (pH 7.6); (E) 5 (pH 7.0);
(F) 6 (pH 7.0) (inset: optical images). Hydrogels of 2 and 4
made by adding 0.2 U/mL alkaline phosphatase to the solu‐
tions of 2P and 4P. All hydrogels are at 0.8 wt% (f = D‐Phe, k
= D‐Lys, y = D‐Try). The scale bar is 100 nm.
We use transmission electron microscopy (TEM) to exam‐
ine the Npx containing hydrogels for evaluating the charac‐
teristics of the molecular assemblies. As shown in Figure 2A
and 2B, hydrogelator 1 self‐assembles to afford large and rig‐
id nanofibers with average width of 54±7 nm, while hydro‐
gelator 2 gives long, thin, and flexible nanofibers with aver‐
age width of 7±2 nm (Figure 2B). Figure 2C shows the nano‐
fibers with helical structure formed in hydrogel of 3, of which
average width is 16±3 nm. The enzymatically formed hydro‐
gel of 4 comprises of long and flexible nanofibers with aver‐
age width of 10±2 nm (Figure 2D). Hydrogel of 5 exhibits
helical, rigid, and long nanofibers with average widths of
26±3 nm (Figure 2E), meanwhile, hydrogelator 6 self‐
assembles to give rigid but short nanofibers with average
widths of 7±2 nm, which tend to form bundles (Figure 2F).
As shown in the bottom row of the images in Figure 2, the
hydrogels containing D‐Tyr (i.e., hydrogels of 2, 4, and 6)
exhibit smaller diameter nanofibers that entangle to form
network with higher density than their corresponding hy‐
drogels (i.e., hydrogels of 1, 3, and 5) without D‐tyrosine. The
incorporation of D‐Lys in hydrogelator 3 also makes it to
form more flexible and narrower nanofibers than the nano‐
fibers of hydrogelator 1. Hydrogel 4 contains the nanofibers
that have similar morphologies to those in hydrogel 2. The
hydrogels of 5 and 6, which have Npx connected at the side
chain, contains nanofibers that are rigid and straight, which
differ from those flexible and long nanofibers in the hydro‐
We synthesize the molecules in Scheme 1 according to the
synthetic procedures that combine solid phase synthesis and
N‐hydroxysuccinimide (NHS) assisted coupling reaction.25
After the synthesis of the designed hydrogelators, the gela‐
ACS Paragon Plus Environment

Page 3 of 5
Journal of the American Chemical Society
gels of 3 and 4. These differences in the morphologies of the‐
drogels 1, 5, and 6 apparently agree with the rigidity of the
1
2
3
4
5
6
7
8
se hydrogels indicate the position of Npx and the presence of
tyrosine at the C‐terminal of the hydrogelators likely play a
role in their self‐assembly in water.
nanofibers in those hydrogels, which also confers relatively
high storage moduli (G’). These results provide insights on
the correlation between molecular structures of the hydro‐
gelators and the viscoelasticity of the supramolecular hydro‐
gels. Moreover, the critical strains of the hydrogels are com‐
parable or higher than that of commercial topical gels (e.g.,
Gelrite® with the critical strain of 1%26), suggesting that the
hydrogels are rheologically suitable for topical use.
Table 1. The rheological properties and TEM characteris‐
tics of the hydrogels of the conjugates of D‐amino acids
and naproxen.
Dynamic
strain sweep
Dynamic fre‐
quency sweep
TEM images
We perform in vitro inhibition assays27 for both COX‐1 and
COX‐2 enzymes to evaluate the efficacies of the NSAID con‐
taining hydrogelators. As shown in Figure 3A, the IC50 values
of COX‐1 enzyme of hydrogelators 1, 2, 3, 4, 5, and 6 are
853.8, 273.7, 383.5, 428.9, 476.3, and 367.3 M, respectively.
All these value are almost two orders of magnitude higher
than the reported IC50 values of naproxen (0.6‐4.8 M28) in
the literature. Undoubtedly, the attachment of the small D‐
peptides to naproxen greatly reduces its binding to COX‐1,
which should reduce the associated adverse gastrointestinal
and renal effects. For COX‐2 enzyme, an inducible enzyme at
the sites of inflammation, the IC50 values of hydrogelators 1,
2, 3, 4, 5, and 6 are 487.7, 68.8, 143.2, 31.7, 132.2, and 36.7 M,
respectively. Since the reported IC50 of naproxen to COX‐2 is
2.0‐28.4 M,28 hydrogelators 4 and 6, obviously, afford rea‐
sonable IC50 values for the inhibition of COX‐2. Thus, hydro‐
gelators 4 and 6 exhibit excellent selectivity, S = 13.5 and S =
10.0, respectively, towards COX‐2. These results not only
validate 4 and 6 as potential candidates for topical NSAID
gels, but also suggest that the presence of D‐tyrosine on the
D‐peptides is beneficial for the activity and selectivity regard‐
less the position of Npx on either the side chain or the main
chain of the D‐peptide. In the control compound, the use of
L‐amino acids (L‐Phe, L‐Lys, and L‐Tyr) to replace the D‐
amino acid residues in hydrogelators 1, 2, 3, and 4 results in
the hydrogelators that exhibit higher IC50 values and poor
selectivity towards COX‐2 (Figure S12). For example, L‐4
(Npx‐FFKY) exhibits IC50 values of 38.0 and 114.8 M for
COX‐2 and COX‐1, respectively, which affords the selectivity
for COX‐2 inhibition to be about 3. These results indicate the
advantages of using D‐peptide for generating the hydrogela‐
tors containing Npx to achieve high selectivity.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Critical strain
G', G”a
Fiber width
(nm)
54±7
(%)
1.0
(Pa)
1
2
3
4
5
6
5.3 x 104, 2.3 x 103
6.2 x 102, 6.7 x 10
3.9 x 102, 4.9 x 10
1.5 x 102, 3.0 x 10
3.8 x 103, 4.2 x 102
1.4 x 103, 4.4 x 102
1.6
7±2
5.2
16±3
5.5
10±2
0.41
0.40
26±3
7±2
aThe value is taken at frequency equals 6.28 rad/s.
After studying their drug efficacies, we evaluate the sus‐
tained release of Npx containing hydrogelators from 0.8 wt%
of hydrogels. We incubate 100 L of hydrogels at 37 oC for 24
hours with 100 L of PBS buffer solution (pH 7.4), which is
refreshed and monitored at 1h, 2h, 4h, 8h, 12h, and 24h. Fig‐
ure 3B shows the release profile of these hydrogelators. After
24 hours, hydrogel 1 slowly and steadily releases 6.5% of gela‐
tors. With increased solubility contributed from hydrophilic
amino acid residues (i.e., Tyr and Lys), hydrogels 2, 3, and 4
release gelators of 8.0%, 14.5%, and 19.8%, respectively. Hy‐
drogels 5 and 6 release 35.8% and 31.7% of gelators after 24h,
likely due to their good solubility of the hydrogelators and
the brittleness of the nanofiber networks (as indicated by low
critical strains of the hydrogels 5 and 6). Dynamic light scat‐
tering of the solutions of the released hydrogelators (1 or 6)
exhibits little difference with that of the PBS buffer (Figure
S15), suggesting that the hydrogelators unlikely exist as self‐
assembled nanofibers after being released from the hydro‐
gels. These results suggest that these Npx containing hydro‐
gels may serve as topical gels for sustained drug delivery.
Figure 3. (A) The IC50 values of the Npx based hydrogelators
for inhibiting COX enzyme (the selectivity, defined as the
IC50 ratio of COX‐1 and COX‐2, is labeled on the top of the
bars). (B) The release profiles of the Npx based hydrogelators
from hydrogels of 1, 2, 3, 4, 5, and 6.
We use oscillatory rheology to examine the viscoelastic
properties of the hydrogels. All the Npx containing hydrogels
exhibit viscoelastic properties of a solid‐like material because
of the storage moduli (G’) being significantly higher than the
loss moduli (G’’) and the frequency independence of the
storage moduli of the hydrogels (Figure S14). Table 1 summa‐
rizes the critical strains and the moduli of hydrogels meas‐
ured from strain sweep and dynamic frequency sweep. The
relatively large critical strains of 3 and 4 suggest that the ‐
amino group from the lysine residue makes the networks of
the hydrogels to be resilient. The low critical strains of hy‐
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 4 of 5
K.; Anderson, K. J. Rheumatology 1999, 26, 2659‐2663; Cevc, G.;
We also examined the biocompatibility of the Npx con‐
Blume, G. Biochim. Biophys. Acta‐Biomembranes 2001, 1514, 191‐205.
(6) Bhuniya, S.; Seo, Y. J.; Kim, B. H. Tetrahedron Lett. 2006, 47, 7153‐
7156.
1
2
taining hydrogelators by incubating them with HeLa cells for
o
72 hours at 37 C. As shown in Figure S13, all of these hydro‐
3
4
5
6
7
8
9
gelators have the IC50 values higher than 500 M, except 1
with IC50 value of 357 M. The high IC50 values of the hydro‐
gels indicate that they are cell compatible. Although the ab‐
sorption of formazan in the MTT assay indicates the promo‐
tions of the growth of the cells when the cells are incubated
with hydrogelators 2, 5, or 6, we find no promotion of the cell
proliferation based on the change of the numbers of the
HeLa cells. Though the exact mechanism remains to be de‐
termined, these increase absorptions likely originate from
the increase of metabolic activity in those HeLa cells treated
by 2, 5, or 6, without increasing viability of cells. 29
(7) Terech, P.; Weiss, R. G. Chem. Rev. 1997, 97, 3133‐3159; Sangeetha,
N. M.; Maitra, U. Chem. Soc. Rev. 2005, 34, 821‐836; Estroff, L. A.;
Hamilton, A. D. Chem. Rev. 2004, 104, 1201‐1217; Yang, Z.; Liang, G.;
Xu, B. Acc. Chem. Res. 2008, 41, 315-326; Yan, C. Q.; Pochan, D. J.
Chem Soc Rev 2010, 39, 3528‐3540.
(8) Xu, B. Langmuir 2009, 25, 8375‐8377.
(9) Cui, H. G.; Pashuck, E. T.; Velichko, Y. S.; Weigand, S. J.;
Cheetham, A. G.; Newcomb, C. J.; Stupp, S. I. Science 2010, 327, 555‐
559; Silva, G. A.; Czeisler, C.; Niece, K. L.; Beniash, E.; Harrington, D.
A.; Kessler, J. A.; Stupp, S. I. Science 2004, 303, 1352‐1355; Matson, J.
B.; Stupp, S. I. Chem Commun 2012, 48, 26‐33; Jayawarna, V.; Ali, M.;
Jowitt, T. A.; Miller, A. E.; Saiani, A.; Gough, J. E.; Ulijn, R. V. Adv.
Mater. 2006, 18, 611‐614; Zhou, M.; Smith, A. M.; Das, A. K.; Hodson,
N. W.; Collins, R. F.; Ulijn, R. V.; Gough, J. E. Biomaterials 2009, 30,
2523‐2530; Capito, R. M.; Azevedo, H. S.; Velichko, Y. S.; Mata, A.;
Stupp, S. I. Science 2008, 319, 1812‐1816.
(10) Salick, D. A.; Kretsinger, J. K.; Pochan, D. J.; Schneider, J. P. J.
Am. Chem. Soc. 2007, 129, 14793‐14799.
(11) Gao, Y.; Kuang, Y.; Guo, Z. F.; Guo, Z. H.; Krauss, I. J.; Xu, B. J.
Am. Chem. Soc. 2009, 131, 13576‐13577.
(12) Zhao, F.; Ma, M. L.; Xu, B. Chem. Soc. Rev. 2009, 38, 883‐891;
Caron, P.; Beckers, A.; Cullen, D. R.; Goth, M. I.; Gutt, B.; Laurberg,
P.; Pico, A. M.; Valimaki, M.; Zgliczynski, W. J. Clin. Endocrinol.
Metab. 2002, 87, 99‐104.
(13) Cameron, P. J.; Johnson, E. K.; Adams, D. J. J. Am. Chem. Soc.
2010, 132, 5130‐5136.
(14) Kiyonaka, S.; Sada, K.; Yoshimura, I.; Shinkai, S.; Kato, N.;
Hamachi, I. Nat Mater 2004, 3, 58‐64.
(15) Yamamichi, S.; Jinno, Y.; Haraya, N.; Oyoshi, T.; Tomitori, H.;
Kashiwagi, K.; Yamanaka, M. Chem Commun 2011, 47, 10344‐10346.
(16) Gao, Y.; Long, M. J. C.; Shi, J. F.; Hedstrom, L.; Xu, B. Chem
Commun 2012, 48, 8404‐8406.
(17) Drury, J. L.; Mooney, D. J. Biomaterials 2003, 24, 4337‐4351;
Uhrich, K. E.; Cannizzaro, S. M.; Langer, R. S.; Shakesheff, K. M.
Chem. Rev. 1999, 99, 3181‐3198.
(18) Peppas, N. A.; Hilt, J. Z.; Khademhosseini, A.; Langer, R. Adv.
Mater. 2006, 18, 1345‐1360; Langer, R. Adv. Mater. 2009, 21, 3235‐3236.
(19) Torchilin, V. P. J. Control. Release 2001, 73, 137‐172; Brazel, C. S.;
Peppas, N. A. Polymer 1999, 40, 3383‐3398.
(20) Reches, M.; Gazit, E. Science 2003, 300, 625‐627; Gorbitz, C. H.
Chem.‐Eur. J. 2001, 7, 5153‐5159.
(21) Zhang, Y.; Kuang, Y.; Gao, Y. A.; Xu, B. Langmuir 2011, 27, 529‐
537.
(22) Duggan, K. C.; Walters, M. J.; Musee, J.; Harp, J. M.; Kiefer, J. R.;
Oates, J. A.; Marnett, L. J. J. Biol. Chem. 2010, 285, 34950‐34959.
(23) Yang, Z. M.; Liang, G. L.; Wang, L.; Xu, B. J. Am. Chem. Soc.
2006, 128, 3038‐3043.
(24) Gao, Y.; Shi, J. F.; Yuan, D.; Xu, B. Nat. Commun. 2012, 3, 1033.
(25) supporting information.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
In conclusion, we have developed multifunctional supra‐
molecular hydrogelators made of D‐amino acids and NSAID,
which is a new approach for delivering therapeutic agents by
biostable, target specific, and potent hydrogels. In addition,
the incorporation of D‐amino acids makes Npx a highly se‐
lective NSAID for inhibiting COX‐2 and minimizing its ad‐
verse effect. This approach may provide useful strategy for
reducing the adverse drug reactions (ADR) of other thera‐
peutic agents or candidates, a subject being investigated fur‐
ther. Although the phosphate trigger in 2P or 4P appears less
relevant to topical gel application of NSAID as a pain reliev‐
er, the enzyme triggered gelation may find new applications
in other setting when the change of physiological conditions
accompanied by the presence of phosphatases.
ASSOCIATED CONTENT
Supporting Information
Synthesis of hydrogelators, HPLC traces and LC‐MS data of
the reduction of hydrogelators, and rheological data. This
material is available free of charge via the Internet at
http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
bxu@brandeis.edu
ACKNOWLEDGMENT
This work is partially supported by Human Frontier Program
(HFSP, RGP 0056/2008), start‐up grant from Brandeis Uni‐
versity, and NIH (R01CA142746), and assisted by the Brandeis
University EM facility (supported by NIH P01 GMGM‐62580).
(26) Carlfors, J.; Edsman, K.; Petersson, R.; Jornving, K. Eur. J. Pharm.
Sci. 1998, 6, 113‐119.
(27) Blobaum, A. L.; Marnett, L. J. J. Med. Chem. 2007, 50, 1425‐1441;
Kargman, S.; Wong, E.; Greig, G. M.; Falgueyret, J. P.; Cromlish, W.;
Ethier, D.; Yergey, J. A.; Riendeau, D.; Evans, J. F.; Kennedy, B.;
Tagari, P.; Francis, D. A.; Oneill, G. P. Biochem. Pharmacol. 1996, 52,
1113‐1125; Cheong, E.; Ivory, K.; Doleman, J.; Parker, M. L.; Rhodes, M.;
Johnson, I. T. Carcinogenesis 2004, 25, 1945‐1952; Cordero, J. A.;
Camacho, M.; Obach, R.; Domenech, J.; Vila, L. Eur. J. Pharm.
Biopharm. 2001, 51, 135‐142.
(28) Barnett, J.; Chow, J.; Ives, D.; Chiou, M.; Mackenzie, R.; Osen, E.;
Nguyen, B.; Tsing, S.; Bach, C.; Freire, J.; Chan, H.; Sigal, E.; Ramesha,
C. Biochim. Biophys. Acta‐Protein Struct. Molec. Enzym. 1994, 1209,
130‐139; Laneuville, O.; Breuer, D. K.; Dewitt, D. L.; Hla, T.; Funk, C.
D.; Smith, W. L. J. Pharmacol. Exp. Ther. 1994, 271, 927‐934.
(29) Wang, P.; Henning, S. M.; Heber, D. PLoS ONE 2010, 5, e10202.
REFERENCES
(1) Silverstein, F. E.; Faich, G.; Goldstein, J. L.; Simon, L. S.; Pincus, T.;
Whelton, A.; Makuch, R.; Eisen, G.; Agarwal, N. M.; Stenson, W. F.;
Burr, A. M.; Zhao, W. W.; Kent, J. D.; Lefkowith, J. B.; Verburg, K. M.;
Geis, G. S. JAMA‐J. Am. Med. Assoc. 2000, 284, 1247‐1255.
(2) Catella‐Lawson, F.; Reilly, M. P.; Kapoor, S. C.; Cucchiara, A. J.;
DeMarco, S.; Tournier, B.; Vyas, S. N.; FitzGerald, G. A. N. Engl. J.
Med. 2001, 345, 1809‐1817.
(3) Bresalier, R. S.; Sandler, R. S.; Quan, H.; Bolognese, J. A.; Oxenius,
B.; Horgan, K.; Lines, C.; Riddell, R.; Morton, D.; Lanas, A.; Konstam,
M. A.; Baron, J. A.; Investigators, A. P. T. N. Engl. J. Med. 2005, 352,
1092‐1102.
(4) Banning, M. Expert Opin. Pharmacotherapy 2008, 9, 2921‐2929.
(5) Mason, L.; Moore, R. A.; Edwards, J. E.; Derry, S.; McQuay, H. J.
BMC Musculoskelet. Disord. 2004, 5, 28; Grace, D.; Rogers, J.; Skeith,
ACS Paragon Plus Environment

Page 5 of 5
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
ACS Paragon Plus Environment