Creation of dextrin vesicles and their loading-delivering capabilities

Article abstract of DOI:10.1039/c3ra43652g

Dextrin vesicles are created, for the first time, by cleverly customizing the polysaccharide backbone with renewable resource 3-pentadecylphenol pendant molecules, which are capable of loading hydrophilic and hydrophobic drugs and subsequently release the

Full text of DOI:10.1039/c3ra43652g

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Creation of dextrin vesicles and their loading-delivering
capabilities†
Cite this: RSC Adv., 2013, 3, 21237
*
Uma Sridhar, P. S. Pramod and M. Jayakannan
Received 15th July 2013
Accepted 9th September 2013
DOI: 10.1039/c3ra43652g
www.rsc.org/advances
Dextrin vesicles are created, for the first time, by cleverly customizing information known on these polysaccharide vesicles for drug
the polysaccharide backbone with renewable resource 3-pentade- delivery applications.
cylphenol pendant molecules, which are capable of loading hydro-
Polysaccharide vesicular assemblies are very important
philic and hydrophobic drugs and subsequently release their 100% nano-scaffolds for drug delivery since they resemble the struc-
cargoes by esterase enzyme action under physiological in vitro ture of the cell membrane and also have unique features for
conditions.
loading and delivering hydrophilic and hydrophobic drugs. Cell
membranes are typically composed of glycolipids formed from
the conjugation of saccharides with lipid molecules.14 These
glycol-conjugates play vital roles in various physiological
processes such as cellular signalling, recognition, pathogen
infection, etc. via interaction of sugar moiety with receptor
proteins.15 Thus, polysaccharide vesicles could interact with the
cell membranes through like–like interactions which could
enable their adhesive or penetrating ability much higher
compared to other synthetic polymer analogues. Recent report
on polysaccharide vesicles by Lecommandoux and co-
workers16,17 and dextran vesicles18 from our research group are
worth mentioning.
Here, we report the rst creation of dextrin vesicles and their
loading and delivering capabilities of hydrophilic and hydro-
phobic molecules under in vitro physiological conditions (see
Fig. 1). Corn-dextrin was suitably modied using renewable
hydrophobic pendant 3-pentadecylphenol (PDP) (a product
from cashew nut fruit) through tailor made synthetic
approaches. Aliphatic ester functionality was chosen to link the
hydrophobic PDP unit in the dextrin backbone; thus the
esterase enzyme could act as stimuli19 for the cleavage of vesi-
cles to deliver their cargoes (see Fig. 1).
Briey, PDP was reacted with ethyl chloroacetate in the
presence of K2CO3 as base to give (1). The ester bond in 1 was
hydrolysed using KOH to give (2). 2 was then coupled with
dextrin to afford DEX–PDP using DCC/DMAP coupling reaction.
The degree of substitution (DS) was determined by comparing
the peak intensities of anomeric proton in dextrin with the PDP
aryl protons (see SF-1 to SF-3, for IR spectra and TGA see SF-4
and SF-5, and NMR data in Table ST1 in ESI†). These dextrin
derivatives are named as DEX–PDP-x where the suffix ‘x’ refers
the actual incorporation of the PDP unit. DEX–PDP-x molecules
Self-assembled Polymer structures are emerging as important
cargo transporters in the biomedical eld for oral and intrave-
nous administration of drug molecules.1 Polysaccharides offer
many inherent advantages such as high molecular weight,
hydrophilic backbone, biodegradable, biocompatible and so
on.2 Dextran,3 chitosan,4 pullulan,5 alginate6 and hyaluronic
acid7 are some of the polysaccharides that are currently being
explored for drug delivery applications. Cellulose and starch are
natural polysaccharides; however, they are less explored for
drug delivery applications. Cellulose is not suitable for admin-
istration of drugs since mammalians cannot digest cellulose
owing to the absence of the enzyme cellulase. Starch is an edible
polysaccharide; however, it is not useful due to poor water
solubility or miscibility. Starch is partially hydrolysed into low
molecular weight fractions (named: dextrin) and employed for
various clinical applications in peritoneal dialysis,8 post-
operative adhesions9 and so on. Dextrin micelles or nano-
particles bearing doxorubicin,10 biotin,10 phospholipase A2,11
and trypsin12 conjugates were reported for tissue repair, wound
healing and drug masking materials, etc. Dextrin hydrogels
were also reported for delivering anti-inammatory drug cur-
cumin.13 Until now, there is no report known for vesicles (or
polymersomes) based on dextrin; as a result there is no
Department of Chemistry, Indian Institute of Science Education and Research (IISER),
Dr Homi Bhabha Road, Pune 411008, Maharashtra, India. E-mail: jayakannan@
iiserpune.ac.in; Fax: +91-20-2590 8186
† Electronic
supplementary
information
(ESI)
available:
Synthesis,
characterization, DLS, FE-SEM, encapsulation and releasing data are available.
See DOI: 10.1039/c3ra43652g
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concentrations (see SF7†). The nano-assemblies were found to
be stable in low pH to neutral pH and also at various concen-
trations ranging from 0.2 mg mLꢀ1 to 1.0 mg mLꢀ1. Further, the
stability of vesicles were continuously monitored for more than
a month by DLS. It was found that the size of the vesicles did not
ꢁ
change signicantly in PBS at 25 C. However, at higher pH ¼
9.2, we noticed a change in the sizes of the aggregate. This was
attributed to the possible destabilization of ester-linkage which
connects the PDP with dextrin backbone. Hence, the dextrin
vesicles are suitable for applications in acidic to neutral condi-
tions (pH < 7.4). DLS histograms of DEX–PDP-13 to DEX–PDP-33
(see SF-6†) revealed that the size of self-assembled aggregates
increased with increase in the degree of substitution in the
dextrin backbone. The average size (see Table ST1†) increased
from 164 nm to 500 nm upon varying DS from 7 to 33%.
Dextrin nano-assemblies were analyzed by electron micros-
copy to image their shape and size. Field-emission scanning
electron microscopy (FE-SEM) image of DEX–PDP-7 is shown in
Fig. 2b (other samples are shown in SF-8a†). DEX–PDP-7
appeared as so spherical objects and resembled the morphology
of polymer vesicles whereas other samples showed the formation
of nano-particular nature (see SF-8a†). The average sizes of the
objects were determined using image J soware and the values
are summarized in Table-ST1.† Vesicles or nano-particles are
stable self-assembled nano-objects in water. For example, a stable
vesicular assembly is expected to show the hydrodynamic volume
equal to its diameter. However, in solution, the vesicles (or nano-
particles) are usually cluster together as two or three species.
Therefore, the sizes of the vesicular assemblies determined by
DLS were typically found to be much higher than expected for
individual species. This can be clearly evident from the FE-SEM
image in Fig. 2b (also see Fig. SF-8a†) that the particles or vesicles
were cluster together rather than isolated. Since, the dextrin
vesicles are freely soluble in water, they showed better correlation
between DLS and FE-SEM techniques. On the other hand, the
sparingly soluble nanoparticles showed larger difference in sizes
between DLS and FE-SEM (see ST-1†).
Fig. 1 (a) Dextrin vesicle design strategy, (b) self-assembly of dextrin with
respect to hydrophilic and hydrophobic content, (c) loading and releasing capa-
bilities of dextrin vesicles under normal and esterase enzyme and (d) synthetic
methodologies.
have unique amphiphilic nature having hydrophilic dextrin
backbone in which the hydrophobic PDP units are anchored for
self-assembly. To determine their self-assembled structures in
water, they were subjected to dynamic light scattering (DLS)
measurement in PBS buffer at pH ¼ 7.4. The DLS histogram of
DEX–PDP-7 is shown in Fig. 2 (for other samples see SF-6†). The
DLS proles of DEX–PDP-7 showed uniform mono-model
distributions with an average size of 160 nm. The stability of
DEX–PDP-7 was also investigated at different pH and
High resolution transmission electron microscope (HR-
TEM) images for DEX–PDP-7 are given in Fig. 2c. The spherical
objects in Fig. 2c clearly showed the existence of dark hydro-
philic layer with distinct inner cavity with respect to the
formation of unilamellar vesicles. Further, the vesicular
assemblies were recorded by staining them with Uranyl acetate
following the literature method.20 It is very clear that these
stained TEM image of that the vesicle features (see Fig. 2d) was
similar to that of un-stained ones as shown in Fig. 2c (see more
images in SF-8b†). Further, the TEM image in Fig. 2d clearly
showed the hydrophobic layer (as more contrast) which is
distinguished from the hydrophilic dextrin. PDP is a very good
hydrophobic unit for producing polymer vesicles. Earlier, the
crystal structure of the PDP unit was resolved by us to under-
stand their molecular packing.18,21 PDP showed inter-digitations
of the long pentadecyl hydrophobic units and these lattice
˚
parameters were obtained as ꢂ29.0 A (or 2.90 nm). The wall
thicknesses of the dextrin vesicles were measured as 3.3 ꢃ 0.3
nm (in Fig. 2c and d) which matched to that of the PDP crystal
packing. Atomic force microscope (AFM) images (see Fig. 2e and f)
Fig. 2 (a) DLS histograms of DEX–PDP-7 at 1 mg mLꢀ1 in PBS. (b) FE-SEM image
of DEX–PDP-7. HR-TEM images of DEX–PDP-7 without (c) or with (d) uranyl
acetate staining. (e and f) AFM images of DEX–PDP-7.
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of DEX–PDP-7 further revealed the internal features of the vesi-
cles. The expanded image (see Fig. 2f) showed the formation of
spherical vesicles with a tent or opening on one-side. This implies
that the vesicles are typically lled with water which was escaped
during the sample drying or AFM analysis.22 The dimensions of
vesicles are obtained as 160 ꢃ 10 nm in the AFM image which
matched with HR-TEM images shown in Fig. 2c and d.
Dextrin was found to undergo self-organization trans-
formation from vesicular to nanoparticle assemblies while
varying the degree of substitution from 7 to 33%. As indicated in
Fig. 1b, the increase in the hydrophobic content changed the
morphology of the dextrin scaffolds from vesicle to nano-
particle. To further support this trend, the critical vesicular
concentration (CVC) of the dextrin vesicle and the critical
association constant (CAC) of the nanoparticles were deter-
mined using pyrene23 as the probe (see SF-9 and ST1† for
details). The CVC of the DEX–PDP-7 was obtained as 8.33 ꢄ
10ꢀ3 mg mLꢀ1. Similarly the critical aggregation concentration
of DEX–PDP-13 and DEX–PDP-20 were determined and their
values are given in the Table ST-1.† It is clear from the table that
the CVC of DEX–PDP-7 was much lower compared to that of
CAC of nano-particles. The CAC and CVC values of the present
cases are in the range of 10ꢀ3 to 10ꢀ2 mg mLꢀ1 which is similar
to that of other reports.3b,21 The CVC of dextrin vesicles were
obtained one order lower compared to the CAC of the nano-
particles. The lower CVC value for vesicles conrmed their
formation of stable and superior self-assembly in water. Thus,
Fig. 3 (a) Photographs of Rh-B loaded DEX–PDP-x samples. DLS histograms (b),
SLS data (c), HR-TEM image (d) and fluorescence microscope image (e) of Rh-B
loaded dextrin vesicles.
CPT encapsulation was done as similar to Rh-B and the
the renewable PDP hydrophobic unit is very unique to produce details are provided in the ESI.† The CPT loading content in the
the dextrin vesicular scaffolds.
vesicles was determined as 12.5 mg mgꢀ1 of polymer by using
The loading capabilities of dextrin vesicles were tested for absorption spectroscopy technique (see SF 12†). DLS measure-
water soluble rhodamine-B (Rh-B) and hydrophobic anticancer ment conrmed the size of the CPT loaded dextrin vesicles as
drug molecule camptothecin (CPT). The polymer and Rh-B were 170 nm which was almost similar to the dextrin vesicles. CPT
taken in a semi-permeable membrane and dialysed at 25 ꢁC loaded dextrin vesicles under uorescent microscope showed
against large amount of water (see SF-10†). The photographs of the existence of spherical blue luminescent objects (see SF 12†).
the polymer samples in vials aer dialysis are shown in Fig. 3a The loading capacities of the vesicles are 0.50 and 1.25 wt% for
(under hand held UV-light exposure). As can be expected, Rh-B and CPT in the core and layer of the vesicles, respectively.
dextrin did not stabilize Rh-B since there is no self-assembly. These loading capacity values are comparable to that of poly(-
The dextrin vesicle (sample DEX–PDP-7) showed the stable styrene oxide)-poly(ethylene oxide) block copolymers,25 where
encapsulation of Rh-B. Unlike vesicles, the nanoparticle DOX loading content was from 0.05 wt% to 1.8 wt% and poly-
internal part is hydrophobic in nature; thus the samples DEX– methacrylic acid gelatin particles, where rhodamine B loading
PDP-13 and DEX–PDP-25 did not show any Rh-B encapsulation. was 0.26 wt%.26 The loading efficiency of the dextrin vesicles
Rh-B loaded dextrin vesicles were characterized by dynamic and were obtained as 40–45% for Rh-B and CPT. However, it is
static light scattering (SLS) methods (see Fig. 3b and c). The important to mention that the drug loading content and effi-
hydrodynamic diameter (Dh) of the Rh-B encapsulated vesicles ciency of the dextrin vesicle may vary to drugs or dye molecules
was determined from DLS as 170 nm (see Fig. 3b) which is very which have to be examined separately. The above preliminary
close to the size of un-encapsulate vesicles (see Fig. 2a). The encapsulation studies showed the importance of dextrin vesi-
hydrodynamic radius of Rh-B loaded vesicle (Dh/2 ¼ Rh) was cles for loading both hydrophobic and hydrophilic molecules,
calculated as 85 nm. SLS provided the radiation of gyration of but they are not restricted to only to these few examples.
vesicular assemblies (Rg) which was determined from the slope
The releasing capabilities of Rh-B and CPT loaded dextrin
ꢁ
of Guinier plot as 86 nm (see Fig. 3c, for details see SF11†). The vesicles were studied under physiological conditions i.e. 37 C
ratio of Rg/Rh ¼ 1 which conrmed the existence of vesicular and pH 7.4. Fig. 4a showed the in vitro release characteristics of
geometry24 in Rh-B loaded samples. HR TEM image of the Rh-B Rh-B encapsulated vesicles. It can be evident that Rh-B was
loaded samples (see Fig. 3d) were further conrmed the exis- released in a controlled manner under standard physiological
tence of spherical vesicles with dark outer hydrophobic conditions. The plot showed 20% Rh-B release in 6 h thereaer
membrane. The uorescent microscopy images (see Fig. 3e) a sustained release to nearly 30% in 24 h (see Fig. 4a). The
showed red uorescent dots in dark background with respect release of CPT went up to 80% in 12 h time period (see Fig. 4b).
Rh-B encapsulated vesicles.
These differences are attributed to the CPT loading in the
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demonstrated using esterase enzyme as stimuli under physio-
logical conditions. The present investigation provides the rst
insight into the designing, encapsulating and delivery aspects
of dextrin vesicles. These vesicles are high in demand for the
fast growing polymer based drug deliveries in cancer therapy.
Further, the approach demonstrated here is also expected to
create new opportunities for the less explored dextrin or starch
based nano-scaffolds for various applications in the area of
nanotechnology.
Acknowledgements
Research funds from Department of Science and Technology
under the Nano-mission SR/NM/Ns-42/2009 is acknowledged.
Notes and references
1 (a) T. M. S. Chang, Nat. Rev. Drug Discovery, 2005, 4, 221; (b)
V. P. Torchillin, J. Controlled Release, 2001, 73, 137.
2 (a) Z. Liu, Y. Jiao, Y. Wang, C. Zhou and Z. Zhang, Adv. Drug
Delivery Rev., 2008, 60, 1680; (b) S. Mizrahy and D. Peer,
Chem. Soc. Rev., 2012, 41, 2623.
3 (a) P. Liu, C. Yue, B. Shi, G. Gao, M. Li, B. Wang, Y. Ma and
L. Cai, Chem. Commun., 2013, 49, 6143; (b) Y.-Z. Du, Q. Weng,
H. Yuan and F.-Q. Hu, ACS Nano, 2010, 4, 6894; (c)
K. E. Broaders, J. A. Cohen, T. T. Beaudette,
Fig. 4 Releasing capabilities of free Rh-B and Rh-B loaded vesicles (a) and free
CPT and CPT-loaded vesicles under normal and in the presence of esterase
enzyme.
´
E. M. Bachelder and J. M. J. Frechet, Proc. Natl. Acad. Sci.
USA, 2009, 106, 5497.
4 (a) B. R. Lee, K. T. Oh, Y. T. Oh, H. J. Baik, S. Y. Park,
Y. S. Youn and E. S. Lee, Chem. Commun., 2011, 47, 1147;
(b) B. Wang, C. He, C. Tang and C. Yin, Biomaterials, 2011,
32, 4630; (c) L. Hu, Y. Sun and Y. Wu, Nanoscale, 2013, 5,
3103.
5 N. Morimoto, S. Hirano, H. Takahashi, S. Loethen,
D. H. Thompson and K. Akiyoshi, Biomacromolecules, 2011,
14, 2013.
6 (a) Y. Jia, J. Fei, Y. Cui, Y. Yang, L. Gaoa and J. Li, Chem.
Commun., 2011, 47, 1175; (b) D. Zhao, C.-J. Liu, R.-X. Zhuo
and S.-X. Cheng, Mol. Pharmaceutics, 2012, 9, 2887.
7 (a) M. Kurisawa, J. E. Chung, Y. Y. Yang, S. J. Gao and
H. Uyama, Chem. Commun., 2005, 4312; (b) S. Ganesh,
A. K. Iyer, D. V. Morrissey and M. M. Amiji, Biomaterials,
2013, 34, 3489.
8 S. J. Davis, G. Woodrow, K. Donovan, J. Plum, P. Williams,
A. C. Johansson, H.-P. Bosselman, O. Heimberger,
O. Simonson, A. Davenport, A. Traneus and J. C. D. Filho,
J. Am. Soc. Nephrol., 2003, 14, 2338.
hydrophobic membrane and Rh-B in the interior cavity of the
vesicles. The hydrophobic PDP unit (see Fig. 1d) is linked by
ester linkage in the dextrin backbone that can be readily cleaved
by esterase enzyme. The release studies were carried by 10 U
horse liver esterase (see Fig. 4a and b). It was found that both
Rh-B and CPT were released very fast within 2 h in the presence
of esterase. This indicates that the ester linkage cleaves almost
immediately; as a result the vesicular structure ruptures and
releases their 100% cargoes at much faster rates. The free drug
or Rh-B release patterns are almost similar to the vesicle
collapsing in the presence of esterase. This conrmed that the
esterase is an excellent stimulus for releasing the loaded
cargoes from the dextrin vesicles instantaneously. Thus, the
customized dextrin vesicles are unique nano-scaffolds for
loading and releasing drug molecules. At present, the drug
loaded dextrin vesicles are subjected to cellular uptake studies
in collaboration with other research groups.
The present investigation demonstrates the creation of
dextrin vesicles, their loading and releasing capabilities. The
9 C. B. Brown, A. A. Luciano, D. Martin, E. Peers, A. Scrimgeour
and G. S. diZerega, Fertil. Steril., 2007, 88, 1413.
renewable resource PDP unit was found to be very unique in 10 D. Hreczuk-Hirst, D. Chicco, L. German and R. Duncan, J.
producing dextrin vesicles at 7% incorporation. At higher Bioact. Compat. Polym., 2001, 16, 353.
incorporation, the modied dextrins were found as nano- 11 R. Duncan, H. R. P. Gilbert, R. J. Carbajo and M. J. Vincent,
particles (from 13 to 50%). Dextrin vesicles were capable of Biomacromolecules, 2008, 9, 1146.
encapsulating both water soluble molecules such as Rh-B in 12 T. H. Senanayake, G. Warren and S. V. Vinogradov,
their internal core and hydrophobic anticancer drug like Bioconjugate Chem., 2011, 22, 1983.
camptothecin (CPT) in the hydrophobic layer. The in vitro 13 C. Goncalves, J. A. Martins and F. M. Gama,
release characteristics of these loaded vesicles were
Biomacromolecules, 2007, 8, 392.
21240 | RSC Adv., 2013, 3, 21237–21241
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14 C. Schatz, S. Louguet, J.-F. Le Meins and S. Leocommandoux, 22 (a) M. Yang, W. Wang, F. Yuan, X. Zhang, J. Li, F. Liang,
Angew. Chem., Int. Ed., 2009, 48, 2572–2575.
B. He, B. Minch and G. Wegner, J. Am. Chem. Soc., 2005,
127, 15107; (b) A. Jeremic, A. S. Quinn, W. J. Cho,
D. J. Taatjes and B. P. Jena, J. Am. Chem. Soc., 2006, 128,
26.
15 J. J. Lundquist and E. J. Toone, Chem. Rev., 2002, 102, 555–578.
16 C. Bonduelle, J. Haung, E. Ibarboure, A. Heise and
S. Lecommandoux, Chem. Commun., 2012, 8353–8355.
17 J. Haung, C. Bonduelle, J. Thevenot, S. Lecommandoux and 23 (a) F. M. Winnik, Chem. Rev., 1993, 93, 587; (b)
A. Heise, J. Am. Chem. Soc., 2012, 134, 119–122.
18 P. S. Pramod, K. Takamura, S. Chapekar, N. Balasubramanian
and M. Jayakannan, Biomacromolecules, 2012, 13, 3627.
19 Y. Shen, B. Zhang, C. J. Murphy, M. Sui, J. Zhao, J. Wang,
J. Tang, M. Fan, E. V. Kirk and W. J. Murdoch, J. Am.
Chem. Soc., 2010, 132, 4259.
20 (a) A. O. Moughton and R. K. O'Reilly, Chem. Commun., 2010,
1091–1093; (b) W. Zhao, D. Chen, Y. Hu, G. M. Grason and
T. P. Russell, ACS Nano, 2011, 5, 486–492.
K. Kalyanasundaram and J. K. Thomas, J. Am. Chem. Soc.,
1977, 99, 2039.
24 C. M. Houga, J. Giermanska, S. B. Lecommandoux,
R. Borsali, D. Tanton, Y. Gnanou and J.-F. L. Meins,
Biomacromolecules, 2009, 10, 32.
25 A. Cambon, A. Rey-Rico, S. Barbosa, J. F. A. Soltero,
S. G. Yeates, J. Bera, M. I. Loza, C. Alvarez-Lorenzo,
A. Concherio, P. Taboada and V. Mosquera, J. Controlled
Release, 2013, 167, 68–75.
21 S. Kashyap and M. Jayakannan, J. Phys. Chem. B, 2012, 116, 26 Z. Gan, J. Ju, T. Zhang and D. Wu, J. Nanomater., 2011, 2011,
9820–9831.
128.
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