Synthesis and self-assembly of a neoglycopeptide: Morphological studies and ultrasound-mediated DNA encapsulation

Article abstract of DOI:10.1002/psc.1334

Self-assembly in peptides and proteins is an often encountered concept, where constituent building blocks are recruited and stabilized, via carefully orchestrated hydrophobic interactions, hydrogen bonding and other non-covalent interactions, to eventually reveal an array of supramolecular aggregates, with defined structural features. This study presents synthesis and self-assembly of a mannosylated peptide in aqueous medium. Turbidimetric assay with Concanavalin A (Con A), a mannose binding protein, was conducted to confirm the presence of hydrophilic mannose group on the exterior surface of self-assembled structures. DNA encapsulation in these soft structures was achieved by ultrasonication of soft spherical structures in the presence of plasmid DNA. This paper describes a novel glycopeptide conjugate which self-assembles to give spherical structures, with a unique ability of encapsulating DNA, upon ultrasonication. Copyright

Full text of DOI:10.1002/psc.1334

Research Article
Received: 6 September 2010
Revised: 23 October 2010
Accepted: 25 October 2010
Published online in Wiley Online Library: 28 December 2010
(wileyonlinelibrary.com) DOI 10.1002/psc.1334
Synthesis and self-assembly
of a neoglycopeptide: morphological
studies and ultrasound-mediated
DNA encapsulation‡
Nidhi Gour,§ Sudipta Mondal and Sandeep Verma∗
Self-assembly in peptides and proteins is an often encountered concept, where constituent building blocks are recruited and
stabilized, via carefully orchestrated hydrophobic interactions, hydrogen bonding and other non-covalent interactions, to
eventually reveal an array of supramolecular aggregates, with defined structural features. This study presents synthesis and
self-assembly of a mannosylated peptide in aqueous medium. Turbidimetric assay with Concanavalin A (Con A), a mannose
binding protein, was conducted to confirm the presence of hydrophilic mannose group on the exterior surface of self-assembled
structures. DNA encapsulation in these soft structures was achieved by ultrasonication of soft spherical structures in the
c
presence of plasmid DNA. Copyright ꢀ 2010 European Peptide Society and John Wiley & Sons, Ltd.
Supporting information may be found in the online version of this article
Keywords: peptide; self-assembly; vesicles; nanocontainer; DNA encapsulation
Introduction
Materials and Methods
Construction of supramolecular architectures, involving self-
association or self-assembly of bioessential components such
as peptides, offers numerous advantages in terms of material
and biochemical applications. Amongst the various possible mor-
phologies achieved with peptide building blocks, the formation
of spherical morphology evinces keen interest due to potential
scope for guest encapsulation and subsequent application as
delivery vehicles [1–4]. In addition, modulated response of soft
molecular ensembles to external stimulus further increases their
scope as drug delivery systems, (bio)chemical sensors, and cell
adhesion mediators, to name a few [5–10]. Modifiable external
stimuli of temperature, pH, light, electric field, chemicals and ionic
strength, could produce measurable changes in responsive soft
matterleadingtomodifiedshapeandsurfaceproperties, solubility
characteristics, ability to self-assemble or disassemble [11–17]. As
a specific recent example, chemical modification of soft vesicular
structures with carbohydrate appendages has been shown to be
very useful, resulting in specific and desirable interactions [18].
We have explored the design and synthesis of a small pep-
tide motif to generate desired morphological features with the
aim of manipulating them with a suitable and biologically rele-
vant tuning mechanism [19–22]. As a result of our investigations,
we have discovered peptide-based supramolecular ensembles
which respond to colchicines [23], physiologically relevant cations
[24], covalently attached structure modifiers [25,26], and sunlight
[27]. In this study, the self-assembly property of the glycopep-
tide N2,N6-bis[(α-D-mannopyranosyl)thio]propionyl]-Lys-Pro-Phe-
Phe-Pro–OH studied in aqueous solution and the formation of
spherical morphology was confirmed using various microscopic
techniques. As an interesting application, we show that these
structures can possibly encapsulate plasmid DNA subsequent to
mild ultrasonication treatment.
General
Dichloromethane, N,N-dimethylformamide, triethylamine and
methanol were distilled, following standard procedures prior to
use.DCC,t-butyloxycarbonylcarbonate,borontrifluorideetherate,
3-mercaptopropionic acid and L-amino acids were purchased
from Spectrochem Pvt. Ltd.; mannose was obtained from SISCO
Research laboratories Pvt. Ltd.; perchloric acid, acetic anhydride
and acetic acid were purchased from S.d. Fine-chem limited,
Mumbai and used without further purification. Concanavalin A
(Con A) was purchased from Sigma Aldrich; pBR322 DNA was
purchased from Bangalore Genei, India. 1H and 13C NMR spectra
were recorded on JEOL-JNM LAMBDA 400 model operating at 400
and 100 MHz, respectively and JEOL ECX-500 model operating at
500 and 125 MHz, respectively. HRMS mass spectra were recorded
at IIT Kanpur, India, on Waters, Q-Tof Premier Micromass HAB 213
mass spectrometer using capillary voltage of 2.6–3.2 kV.
∗
Correspondenceto:Sandeep Verma, Department ofChemistry, Indian Institute
of Technology Kanpur, Kanpur, 208 016 UP, India. E-mail: sverma@iitk.ac.in
Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208
016 UP, India
‡
§
Special issue devoted to the E-MRS Symposium C ‘‘Peptide-based materials:
from nanostructures to applications’’, 7–11 June 2010, Strasbourg, France.
Department of Chemical Sciences, Tata Institute of Fundamental Research,
Homi Bhabha Road, Mumbai 400005, India.
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J. Pept. Sci. 2011; 17: 148–153
Copyright ꢀ 2010 European Peptide Society and John Wiley & Sons, Ltd.

DNA ENCAPSULATION IN A SELF-ASSEMBLED NEOGLYCOPEPTIDE
Synthesis and Characterization
evaporation as hygroscopic solid (0.04 g, 26%). Rf = 0.1 (30%
◦
25
methanol/dichloromethane). [α]D = +198.5 (c 0.2, CH3OH); 1H
NMR (500 MHz, DMS0-d6, 25 ◦C, TMS) δ (ppm) 1.19–1.27 (m, 3H),
1.47–1.84(m,13H),2.08–2.11(m,2H),2.35–2.43(m,5H),2.71–2.77
(m, 10H), 2.99(bs, 6H), 3.57–3.69 (m, 13H), 4.21–4.26, 4.36, 4.44,
4.60–4.69, 4.80, 4.96 (m, 3H), 5.12–5.14 (bs, 2H), 5.56–5.58 (d,
J = 8.05 Hz, 2H), 7.11–7.30 (m, 10H), 7.76–7.89 (m, 2H), 8.08–8.12
(m, 2H); 13C NMR (125 MHz, DMS0-d6, 25 ◦C, TMS) δ (ppm) 23.41,
24.99, 25.83, 27.24, 27.49, 29.15, 29.47, 31.41, 33.85, 36.27, 37.34,
38.51, 39.59, 39.92, 40.24, 46.90, 47.30, 48.03, 49.12, 52.39, 59.16,
59.87, 61.69, 67.75, 72.03, 72.32, 74.82, 85.70, 126.78, 128.46,
129.91, 157.21, 169.71, 171.07, and 173.69; m/z (HRMS) Calculated
[M+Na+] 1157.4399, Found 1157. 4395.
N2,N6-Bis[(2, 3, 4, 6-tetra-O-acetyl-α-D-mannopyranosyl) thio] pro-
pionyl]-lysine N-hydroxysuccinimide ester
N-hydroxysuccinimide (0.13 g, 1.13 mmol) and compound 1
[20] (1.0 g, 1.01 mmol), were taken in a two-necked round
bottom flask and dissolved in dry dichloromethane (20 ml). This
resulting solution was stirred in ice-cold water under nitrogen
atmosphere for 10 min. DCC (0.25 g, 1.2 mmol) was dissolved in
dry dichloromethane (5 ml) and added to the reaction mixture in
small batches. The stirring was continued for 1 h in ice-cold water
followed at room temperature over night. The white precipitate
of N,Nꢁ-dicyclohexylurea was filtered off and the filtrate was
washed with 10% sodium-bicarbonate solution (2 × 10 ml) and
brine solution (2 × 10 ml). The combined organic layer was dried
over anhydrous sodium sulfate, followed by the removal of the
solvent by evaporation to yield product (0.56 g, 52%). Rf = 0.45
(10% methanol/dichloromethane). The product was used without
further purification in next step.
Atomic Force Microscopy
Atomic force microscopy (AFM) was carried out in air using an
Agilent Technologies AFM (5500 AFM/SPM) operating under the
Acoustic AC mode (AAC). The sample was mounted on the XY
stage of the AFM and the integral video camera (NAVITAR, Model
N9451A-USO6310233 with the Fiber-light source, MI-150 high
intensity illuminator from Dolan-Jenner Industries) was used to
locate the regions of interest. Silicon nitride cantilevers with
resonant frequency of 150 kHz were used. The average dimension
thickness, width and length of cantilever were approximately
2.0, 51 and 446 µm, respectively. The scanner model N9524A-
USO7480132.xml/N9520A-USO7480152.xml was calibrated and
used for imaging. The images were taken in air at room
temperature, with the scan speed of 1.5–2.2 lines/s. Data
acquisition and analysis were carried out using PicoView 1.4
and Pico Image Basic software, respectively. Fresh solutions of
3 (1 mM) in water were prepared and incubated at 37 ◦C for 12 h,
prior to microscopic investigation. A 10 µl aliquot of the solution
was transferred onto freshly cleaved mica surface. The sample-
coated mica was dried for 30 min under lamp, and finally vacuum
was applied for 30 min followed by AFM imaging.
N2,N6-Bis[(2, 3, 4, 6-tetra-O-acetyl-α-D-mannopyranosyl) thio] pro-
pionyl]-Lys-Pro-Phe-Phe-Pro-OMe (2)
A solution of N-hydroxysuccinimide ester of 1 (0.5 g, 0.46 mmol)
in dry dichloromethane (∼15 ml) was added to TFA salt of H-Pro-
Phe-Phe-Pro-OMe [21] (0.22 g, 0.34 mmol) dissolved in dry DMF
(∼5 ml) and stirred. TEA (78 µl, 0.56 mM) was added to the reaction
mixtureinadropwisefashionandtheresultingsolutionwasstirred
for ∼12 h under nitrogen atmosphere. The reaction mixture was
evaporated to dryness and the residue obtained was dissolved in
dichloromethane (15 ml) and the organic layer was washed with
1 N HCl (2 × 10 ml) and saturated sodium-bicarbonate solution
(2 ×10 ml). The combined organic layer was dried over anhydrous
sodium sulfate and the solvent was evaporated to yield a yellow oil
whichwaspurifiedusing silicagelcolumnchromatography(5–6%
CH3OH gradient in CH2Cl2) to give final product as hygroscopic
solid (0.28 g, 40.7%). Rf = 0.3 (5% methanol/dichloromethane).
1H NMR (500 MHz, CDCl3, 25 ◦C, TMS) δ (ppm) 1.29–1.36 (q, 2H,
J = 12.25 Hz, 24.25 Hz), 1.57–1.60 (d, 2H, J = 12.65), 1.70–1.73 (d,
6H, J = 13.00), 1.90–2.15 (m, 28H), 2.49–2.57 (m, 2H), 2.89–2.94
(m, 6H), 3.22–3.26 (m, 2H), 3.46–3.46 (m, 6H), 3.64–3.67 (m, 2H),
3.72(s, 3H), 4.06–4.12(m,3H), 4.29–4.32(m, 7H), 5.17–5.22(m, 2H),
5.29 (bs, 7H), 6.94–6.96 (m, 2H), 71.3–7.25 (m, 10H), 8.10–8.11 (m,
2H); 13C NMR (125 MHz, CDCl3, 25 ◦C, TMS) δ (ppm) 15.09, 20.40,
20.88, 21.06, 24.61, 25.30, 29.79, 33.07, 50.15, 52.35, 62.52, 65.89,
66.32, 69.17, 69.61, 126.67, 126.80, 128.46, 129.75, 169.83, 170.00,
and 171.00. m/z (HRMS) Calculated [M+Na+ ] 1507.5400, Found
1507.5249.
Scanning Electron Microscopy
A 20 µl aliquot of 3 dissolved in water (1 mM) and incubated
at 37 ◦C for 12 h was dried under lamp on copper stubs and
subsequently coated with gold. Scanning electron microscopic
images were acquired on FEI QUANTA 200 microscope, equipped
with a tungsten filament gun, operating at WD 10.6 mm and 20 kV.
Optical Microscopy
A 20 µl aliquot of the 3 (1 mM) dissolved in water and incubated at
37 ◦C for 16 h was dried under lamp on glass slide and visualized
without filter in (Leica DM2500M) microscope under 100× lens.
N2,N6-Bis[(α-D-mannopyranosyl)thio]propionyl]-Lys-Pro-Phe-Phe-
Pro–OH (3)
Fluorescence Microscopy
To a solution of compound 2 (0.2 g, 0.13 mmol) in methanol
(10 ml) sodium methoxide (0.09 g, 1.6 mmol) was added and the
reaction mixture was stirred for 1 h at room temperature under
nitrogen atmosphere. The resulting solution was neutralized on a
Amberliteresincolumn,whichwasactivatedpriortouseby2NHCl,
followed by solvent evaporation to yield deprotected compound
2a. It was further dissolved in minimum volume of methanol
and 0.14 ml 1 N NaOH was added. The resulting solution was
stirred for 12 h, followed by neutralization by activated Amberlite
resin. The deprotected compound 3 was obtained upon solvent
Compound 3 was dissolved in rhodamine B aqueous solution
(1 µM) to a final concentration of 1.0 mM and incubated for 16 h
at 37 ◦C. After 16 h, 20 µl of the solution was loaded on the glass
slide and dried under lamp. Dye stained structures were examined
under a fluorescent microscope (Leica DM2500M), provisioned
witharhodaminefilter(absorption540 nm/emission625 nm). This
filterallowsoptimizedvisualizationofrhodamine-treated(positive
resolution)comparedwithuntreated(negativeresolution)vesicles
that are virtually invisible to this light.
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J. Pept. Sci. 2011; 17: 148–153 Copyright ꢀ 2010 European Peptide Society and John Wiley & Sons, Ltd. wileyonlinelibrary.com/journal/psc

GOUR, MONDAL AND VERMA
OAc
OAc
AcO
AcO
O
O
O
OAc
OAc
O
S
S
1. NHS/ DCC, Dry DCM, 0°C, 1 h
N
H
2. TFA.PFFPOMe in DMF/ Et3N, rt, 12 h
AcO
AcO
OH
N
H
1
O
OAc
OAc
AcO
AcO
O
O
O
NaOMe, MeOH, 4 h
O
H
OAc
OAcS
O
N
O
N
H
N
N
AcO
AcO
H
O
O
N
O
N
H
S
O
OH
OH
OH
HO
HO
O
O
O
H
N
OH S
O
NaOH, MeOH, 4 h
O
N
H
N
N
HO
HO
H
O
O
O
N
O
N
H
S
O
2a
OH
OH
OH
HO
HO
O
O
O
H
OH S
O
N
O
N
H
N
N
HO
HO
H
O
O
OH
N
O
N
H
S
O
3
Figure 1. Synthetic scheme for compound 3.
Turbidimetric Assay
added to 180 µl of 12 h aged solution of 3 and then sonicated
for 2 min in a sonicator from Entertech Pvt. Ltd. (200 W) under
ice. The samples were loaded onto 0.7% agarose gel containing
ethidium bromide (1 µg/ml). Electrophoresis was carried out for
1 h at constant current (80 mA) in 0.5× TBE buffer (1.1 M Tris;
900 mM Borate; 25 mM EDTA; pH 8.3). Gels were imaged with a
PC-interfaced Bio-Rad Gel Documentation System 2000.
Time-dependent turbidimetric assay was performed in a quartz
cell (1 cm × 1 cm). Aliquots of Con A solution (300 µl, l.0 mg/ml)
dissolved in HEPES buffer (10 mM, pH 7.4, containing CaCl2 1 mM,
MnCl2 1 mM) were diluted with same HEPES buffer (1125 µl). Then
a solution of 3 (1 mM, 10 µl) incubated for 12 h at 37 ◦C in water
was added. UV spectra of mixture were recorded after every 2 min.
The absorbance of mixture was monitored by scanning samples in
range 250–600 nm and was recorded in UV visible spectrometer
Varian Cary 100 Bio UV–Visible spectrophotometer.
Acridine Orange Binding Assay with DNA
Compound 3 was dissolved in Acridine orange aqueous solution
(10 µM) to a final concentration of 1.0 mM and incubated for 16 h
at 37 ◦C. To this incubated solution (180 µl) was added 20 µl of
DNA (50 µg/ml). One part of this aliquot was then sonicated for
2 min while other left as control. Greenish fluorescence inside
sonicated sphere was visualized using fluorescent microscope
(Leica DM2500M), provisioned with a fluorescence illuminator
and a fluorescein filter (absorption 494 nm/emission 521 nm). For
sonication studies, solution was sonicated for 2 min in a sonicator
from Entertech Pvt. Ltd. (200 W) under ice.
Agarose Gel Electrophoresis
Samples for gel electrophoresis were prepared by mixing 20 µl of
pBR322DNA(50 µg/ml)to3(180 µl, threedifferentconcentrations
viz. 1, 0.5 and 0.1 mM were used) for 12 h at 37 ◦C. These samples
were sonicated for 2 min in a sonicator from Entertech Pvt. Ltd.
(200 W) under ice. Control samples were prepared by adding 20 µl
of DNA to 180 µl of autoclaved water (DNA alone); 20 µl of DNA
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DNA ENCAPSULATION IN A SELF-ASSEMBLED NEOGLYCOPEPTIDE
Figure 2. Microscopic images of spherical aggregates formed by self-assembly of 3 (1 mM, aqueous solution) after 12 h of incubation at 37 ◦C. (A) Optical
micrograph of 3 on glass slide; (B) SEM micrograph of 3 on Cu stubs; (C) AFM image of spheres on mica; (D) Fluorescent micrograph showing intensely
red spherical aggregates.
Results and Discussion
Encouraged by our earlier studies where the tetrapeptide H-Pro-
Phe-Phe-Pro–OH afforded spherical morphology in 50% aqueous
methanol [21], we decided to conjugate this tetrapeptide with
neoglycosylated lysine (1), with the aim of synthesizing water
soluble conjugates to bring application of these soft structures
in biological studies. The glycopeptide conjugate N2,N6-Bis[(α-
D-mannopyranosyl)thio]propionyl]-Lys-Pro-Phe-Phe-Pro–OH (3)
was synthesized as outlined in Figure 1 and its self-assembly
properties were studied in aqueous medium.
Self-assembly of 3 was studied after aging the sample (1 mM) in
aqueous solution at 37 ◦C for 12 h. Optical microscopic studies
revealed the formation of spherical structures after 12 h of
incubation in water (Figure 2(A)). SEM confirmed formation of
spherical structures (Figure 2(B)). Further evidence was obtained
from AFM experiments (Figure 2(C)). It was also possible to stain
these structures with rhodamine B and fluorescence microscopy
image once again afforded brightly stained spherical aggregates
arising from the non-covalent ensemble of 3 (Figure 2(D)). This
suggested that the gross morphology of self-assembly remained
the same, while engineering a beneficial property of water
solubility.
A closer inspection of the chemical structure of 3 reveals
a surfactant-like, where hydrophobic peptide fragment could
possibly be envisioned as a tail and the hydrophilic mannose
residue may act as head group. As a result of the self-aggregation
in aqueous solution, it is likely that the aromatic amino acid
side chains get buried in the interior of the soft structure and
the hydrophilic mannose residues will eventually decorate the
exterior surface of spherical structures. A carbohydrate–lectin
interaction assay was employed to test the projection of mannose
Figure 3. Interaction of 3 with Con A. UV visible spectrum of Con
A with 3 at time intervals of 3 min shows turbidity (inset: turbidity
with respect to time). This figure is available in colour online at
wileyonlinelibrary.com/journal/jpepsci.
units on the surface, based on the known mannose–Concanavalin
A (Con A) interactions. The mannose–Con A interaction affords
aggregation due to multivalent effect, thus enhancing turbidity of
the solution [28–31]. Thus, a turbidimetric assay was performed
to evaluate interaction of 3 with Con A and it leads to an increase
in the absorbance at 400 nm as a function of time (Figure 3) (see
supporting information). Such an observation suggests for the
presence of mannose on the exterior of the spherical structures
affording Con A aggregation, thus confirming the premise of
exposed hydrophilic residues conferring water solubility to 3.
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GOUR, MONDAL AND VERMA
Figure 4. Gel of DNA with 3: Lane 1: DNA alone; Lane 2, DNA coincubated
with 3 (1 mM); Lane 3: DNA coincubated with 3 (0.5 mM); Lane 4: DNA
coincubated with 3 (0.1 mM); Lane 5: DNA alone ultrasonicated for 2 mins;
Lane 6, DNA coincubated with 3 (1 mM) ultrasonicated for 2 mins; Lane 7,
DNA coincubated with 3 (0.5 mM) ultrasonicated for 2 mins; Lane 8, DNA
coincubated with 3 (0.1 mM) ultrasonicated for 2 mins.
In our earlier study, we had reported that lysine conjugated with
a biantennary mannose derivative (1) forms spherical structures
that are hollow in nature and afford effective encapsulation of
alkaline phosphatase enzyme, plasmid DNA and a GFP reporter
gene, thereby illustrating their potential for confinement and
delivery applications [19]. But these soft structures were not very
robust and disrupted rather quickly when sonicated. It was thus
of great interest to evaluate the stability of the soft structures of 3
for possible use as delivery vehicle for biologics, as the biological
importance of glycoclusters is documented [32,33].
Using a standardized protocol, pBR322 was coincubated with
3 with an aim of encapsulating it within the confines of 3, for
gene delivery applications. Agarose gel electrophoresis of this
mixture (Figure 4; lanes 2–4) revealed a band corresponding to
pBR322 plasmid. The presence of DNA in the mixture suggested
the lack of complexation/encapsulation of plasmid. Following
our experience concerning disruption of soft structures with
ultrasound, we decided to irradiate DNA–3 mixture in an
ultrasonic bath for 2 min, followed by electrophoresis. To our
surprise, the band corresponding to pBR322 DNA disappeared
(Figure 4; lanes 6–8). We surmise that these observations results
from the gentle exposure of DNA–3 complex to ultrasound
resulting in complexation or encapsulation of DNA within the
spherical aggregates of 3. In a control experiment, DNA alone
was ultrasonicated for 2 min to ensure that the disappearance
of the plasmid band does not involve DNA degradation due to
ultrasonication.
We resorted to Acridine orange dye binding assay to further
ascertain the encapsulation of plasmid DNA in soft structures
achieved from the self-assembly of 3. Acridine orange is a nucleic
acid selective fluorescent cationic dye and it interacts with DNA
and RNA by intercalation or electrostatic attraction [34]. The
appearance of green fluorescence on Acridine orange addition
to DNA confirms the intercalation process. Ultrasonication of 3,
plasmid DNA and the dye in the same reaction mixture, afforded
a bright green fluorescence contained within the spherical
structures as observed by fluorescence microscopy (Figure 5(A)
and (B)). Preformed spheres of 3 with added plasmid DNA,
in the absence of ultrasound treatment, showed pale, diffused
fluorescence when incubated with Acridine orange (Figure 5(C)).
These experiments also suggest that controlled irradiation of
ultrasound affords transient opening of pores/channels in the
soft structures which enables DNA and Acridine orange to enter
Figure 5. (A) Fluorescent micrograph of spheres of 3 which are ultrason-
icated in presence of DNA showing green fluorescence due to binding
of Acridine orange with DNA; (B) isolated sphere of 3 ultrasonicated in
the presence of DNA; (C) Isolated spheres of 3 with added DNA, but not
ultrasonicated.
the inner hollow compartment leading to intense, punctuated
fluorescent response.
These results could be somewhat correlated to the concept
of electroporation, where one capitalizes on the relatively
weak nature of phospholipid bilayer hydrophobic/hydrophilic
interactions and an impulse of mild current/voltage shock
temporarily disrupts membrane, allowing polar molecules to pass
through them [35,36]. This deformity in the lipid bilayer quickly
dies out when the electrical impulse is discontinued and leaves
the cell intact. This approach is used for transforming cell lines as
it is not harmful to the cells. In a way, the entry of plasmid DNA in
the soft spherical structures of 3, upon mild ultrasound irradiation,
resembles electroporation technique and offers an interesting
alternate mechanism for transiently making the soft structures
porous in nature.
Conclusions
In conclusion, we have demonstrated that the N,N-bis-mannosyl-
Lys-Pro-Phe-Phe-Pro–OH peptide derivative (3) exhibits self-
association leading to the formation of spherical structures, in
aqueous medium. The presence of multiple mannose residues on
the surface will enable targeting of such structures to specialized
cells such as dendritic cells, which are potent antigen-presenting
cellsthatexpressseveralmembranelectins,includingthemannose
receptor. The soft structures offer DNA encapsulation upon
sonication, which was ascertained by an increase in fluorescence
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DNA ENCAPSULATION IN A SELF-ASSEMBLED NEOGLYCOPEPTIDE
contained within spherical aggregates due to Acridine orange
intercalation with encapsulated DNA. Thus, the self-assembling
property of 3 and the possibility of loading cargo inside these
structures suggest their possible use as delivery vehicles for
specialized cells supporting multivalent mannose interactions.
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Acknowledgements
NG thanks IIT Kanpur for a pre-doctoral fellowship and SM thanks
CSIR for a senior research fellowship. This work is supported by
Department of Science and Technology, India (SV).
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J. Pept. Sci. 2011; 17: 148–153 Copyright ꢀ 2010 European Peptide Society and John Wiley & Sons, Ltd. wileyonlinelibrary.com/journal/psc