Oligo-glycerol based non-ionic amphiphilic nanocarriers for lipase mediated controlled drug release

Article abstract of DOI:10.1039/d0ra07392j

A new class of non-ionic amphiphiles is synthesized using a diaryl derivative of diglycerol as a central core and functionalizing it with long alkyl chains (C-12/C-15) and monomethoxy PEG moiety (M_n: 350/550) by following a chemo-enzymatic approach. The aggregation behavior of the amphiphiles in aqueous medium is studied by using dynamic light scattering (DLS) and fluorescence spectroscopy, whereas the size and morphology of the aggregates are studied by transmission electron microscopy (TEM). A hydrophobic dye, Nile red and a hydrophobic drug, nimodipine, are used to demonstrate the nano-carrier capability of these non-ionic amphiphilic systems and the results are compared with amphiphilic analogues obtained from the triaryl derivatives of triglycerol. Thein vitrocontrolled release of the encapsulated dye is successfully carried out in the presence of immobilizedCandida antarcticalipase (Novozym 435). Furthermore, cytotoxicity data is also collected which suggests that the amphiphiles are suitable for biomedical applications.

Full text of DOI:10.1039/d0ra07392j

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PAPER
Oligo-glycerol based non-ionic amphiphilic
nanocarriers for lipase mediated controlled drug
Cite this: RSC Adv., 2020, 10, 37555
release†
a
a
ab
a
c
Parmanand, Ayushi Mittal, Abhishek K. Singh, Aarti, Katharina Achazi,
b
b
a
Chuanxiong Nie, Rainer Haag and Sunil K. Sharma
*
A new class of non-ionic amphiphiles is synthesized using a diaryl derivative of diglycerol as a central core
and functionalizing it with long alkyl chains (C-12/C-15) and monomethoxy PEG moiety (M : 350/550) by
n
following a chemo-enzymatic approach. The aggregation behavior of the amphiphiles in aqueous
medium is studied by using dynamic light scattering (DLS) and fluorescence spectroscopy, whereas the
size and morphology of the aggregates are studied by transmission electron microscopy (TEM). A
hydrophobic dye, Nile red and a hydrophobic drug, nimodipine, are used to demonstrate the nano-
carrier capability of these non-ionic amphiphilic systems and the results are compared with amphiphilic
analogues obtained from the triaryl derivatives of triglycerol. The in vitro controlled release of the
encapsulated dye is successfully carried out in the presence of immobilized Candida antarctica lipase
Novozym 435). Furthermore, cytotoxicity data is also collected which suggests that the amphiphiles are
suitable for biomedical applications.
Received 28th August 2020
Accepted 3rd October 2020
DOI: 10.1039/d0ra07392j
(
rsc.li/rsc-advances
(
PLGA), etc. each having their own limitations. The pluronics
1
. Introduction
have a fast degradation rate in vivo whereas in PAMAM, the
The observance of self-assembly phenomena in lipids, carbo- probability of retro-Michael addition may restraint their shelf-
hydrates, proteins and nucleic acids producing structurally life at the ambient conditions, lipoplexes favour non-specic
1–6
precise and functional supramolecular architectures
has electrostatic interactions with negatively charged hydrophobic
inspired researchers for the fabrication of structurally different serum albuminate, cellular components and other negatively
and functional nano-structured materials having applications charged systemic molecules and PLA/PLGA based nanocarriers
7–11
13,18–20
in various elds such as biomedicine and bio-technology.
exhibits burst release and poor loading of the drug.
In
Amongst the various promising applications of nano- order to overcome these problems small non-ionic amphiphilic
architectures, drug delivery is of immense importance due to systems can enhance the properties of pharmaceutics in terms
the concerns of lipophilicity and limited aqueous solubility of solubility, bioavailability, and increase the lifetime of drug
associated with the commonly used drugs of low molecular and selective release at the target site. Furthermore, the trig-
ꢀ
1
weight (under 500 g mol ). Also, such drugs are known to gered release of drug in the body is an important aspect which is
diffuse rapidly in the body, have shorter circulation time, lack somehow missing in traditional drug delivery systems. Herein,
selectivity, and can interact through multiple binding sites stimuli responsive amphiphilic architectures have been
1
2,13
leading to unwanted side effects.
to address these issues by developing amphiphilic nano- carriers possess ester linkages and their hydrolysis is lipase
structured drug delivery agents.
Attempts have been made explored for drug delivery and release. The reported nano-
12,14–17
There are various tradi- responsive facilitating the release of the drug. Such amphiphilic
tional drug carriers e.g. PAMAM dendrimers, pluronics, lipo- architectures facilitate a higher concentration of a drug to reach
somes, poly(lactic acid) (PLA) and poly(lactic-co-glycolic acid) the target cell than would occur in the natural aqueous milieu
and thus lowering the required dosage of the drug.
The amphiphilic nanocarriers can either be ionic or non-
Department of Chemistry, University of Delhi, Delhi 110 007, India. E-mail: sk. ionic, however, toxicity issues associated with ionic counter-
a
sharma90@gmail.com; Tel: +91-11-27666696
part and particular with the cationic amphiphilic systems are
widely reported, it makes them less important for biomedical
applications. Cationic amphiphiles are known to exhibit non-
specic electrostatic interactions with negatively charged
hydrophobic serum albuminate, cellular components and other
negatively charged systemic molecules. Due to such non-
b
Institut f u¨ r Chemie und Biochemie, Freie Universit a¨ t Berlin, Takustraße 3, 14195
Berlin, Germany
c
Institut f u¨ r Chemie und Biochemie, Freie Universit a¨ t Berlin, Arnimallee 22, 14195
Berlin, Germany
†
Electronic supplementary information (ESI) available. See DOI:
0.1039/d0ra07392j
1
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specic interactions, the transfection complexes bind to the favorable properties such as aqueous solubility, non-toxicity, good
biological cell surfaces and other systemic molecules, eventu- chemical stability and biocompatibility.
ally leading to compromised with targeted lipofection. To
We have synthesized a series of new non-ionic diglycerol-based
address these issues, non-ionic amphiphilic architectures were amphiphilic compounds (15–18) that self-assemble in aqueous
introduced as an alternative to cationic ones. They offer many medium forming an inner hydrophobic core capable of encapsu-
advantages over ionic amphiphilic architectures including lating hydrophobic guest and its subsequent release under
better stability, pH independence, long shelf-life and minimum hydrolytic conditions (Fig. 1). For the construction of these
unwanted interaction, due to which non-ionic amphiphiles amphiphiles two hydrophobic aliphatic acid moieties were
13,21–23
have preferred acceptance in the biomedical eld.
attached via the primary hydroxyl groups of diglycerol, whereas
Furthermore, most of the amphiphiles reported in literature for hydrophilic (mPEG acid) moieties were attached to the secondary
this purpose are either polymer or dendritic architectures hydroxyl groups through an aromatic spacer, i.e., p-hydroxybenzoic
produced from monomer moieties, however, replacing mono- acid (Scheme 1). The self-assembly behavior of these amphiphiles
mers with oligomers for the polymers synthesis is emerging as was studied using uorescence spectroscopy, DLS and TEM. Nile
an interesting line of development.
red and nimodipine were used as model hydrophobic guests to
Herein, our major focus is to design and develop newer study the nanocarrier potential of amphiphiles.
amphiphilic architectures using oligomeric building blocks to
have improved nanocarrier characteristics. The use of monomers
leads to the formation of low molecular weight reaction products,
2
. Experimental section
2.1. NMR, IR, mass and GPC analysis
which adversely affects the properties of the macromolecular
24,25
1
13
compounds.
In contrast, glycerol oligomers may be used as
H and C NMR spectrum were recorded on JEOL 400 and 100.5
superior building blocks for the synthesis of supramolecular MHz spectrometer, respectively; the solvent residual peak was
architectures in polycondensation or polymerization reactions. used for referencing. The chemical shi values are on d scale
The oligomers of glycerol such as di-, tri- and tetraglycerol have and coupling constant (J) values are in hertz. The IR spectra of
been well studied for various applications such as emulsier, the samples were recorded using either Perkin-Elmer FT-IR
26,27
thickeners, and antifogging agents, etc.
Our group has earlier model 9 or Compact FT-IR Spectrometer ALPHA II from
synthesized functionalized glycerol oligomers using a chemo- Bruker. Mass and GPC data were recorded on an Agilent-6530 Q-
27
enzymatic pathway. As an extension of our ongoing research TOF LCMS and Waters GPC system equipped with a Waters 515
program to design and develop glycerol oligomers based nano- HPLC pump, respectively.
carriers, we decided to use diglycerol for the synthesis of amphi-
philic nano-transporters as glycerol is renewable, nontoxic, and
3
. Results and discussion
28
biodegradable.
Furthermore, as the hydrophilic–lipophilic
balance (HLB) have a vital role in the aggregation and transport A series of new non-ionic amphiphilic architectures have been
29,30
capacity of amphiphiles,
our interest is to ne tune the physi- synthesized by rst preparing diaryloxydiglycerol core by the
cochemical characterization of amphiphilic systems by varying reaction of diacetoxydiglycerol (3) with methyl p-hydrox-
hydrophilic and hydrophobic components. For this purpose, ybenzoate by following Mitsunobu reaction to yield compound
monomethoxy-polyethyleneglycol (mPEG) is used because of its 4. The compound 4 was subsequently hydrolyzed in two steps to
give diaryloxydiglycerol 6. It was reacted further with propargyl
Fig. 1 Representation of synthesis, self-assembly of the amphiphiles, guest encapsulation and its release under hydrolytic conditions using the
enzyme Novozym 435.
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ꢁ
ꢁ
Scheme 1 Synthesis of hydrophobic moiety: (i) MsCl, triethyl amine, DCM, 0–25 C, 2 h; (ii) solketal, KOH, TBAB, toluene, 70 C, 40 h; (iii) Dowex
ꢁ
ꢁ
5
2
0wx8, methanol, 50 C, 12 h; (iv) vinyl acetate, Novozym 435, THF, 30 C, 12 h; (v) ethyl p-hydroxybenzoate, DIAD, triphenylphosphine, THF,
ꢁ
ꢁ
ꢁ
ꢁ
5 C, 15 h; (vi) K
2
CO
3
, ethanol, 25 C, 12 h; (vii) KOH, ethanol, 80 C, 12 h; (viii) K
2
CO
3
, propargyl bromide, DMF, 50 C, 12 h; (ix) n-alkyl carboxylic
ꢁ
acid, EDC$HCl, DMAP, DCM, 25 C, 12 h.
bromide to obtain the compound 7. Incorporating lipophilic diglycerol (2). The primary hydroxyls of diglycerol were chemo-
long chain aliphatic acid (C-12/C-15) via the primary hydroxyl selectively acylated using vinyl acetate in the presence of
groups of 7 followed by coupling of hydrophilic mPEG azide immobilized Candida antarctica lipase (Novozym 435) following
ꢀ
1
31
(
M
n
: 350/550 g mol ) via copper catalyzed Click reaction led to the literature procedure to give compound 3. The unreacted
the synthesis of the amphiphilic architectures 15–18 (Schemes secondary hydroxyl groups of the compound 3 were then
–3). The physicochemical and supramolecular organization coupled with ethyl p-hydroxybenzoate via Mitsunobu reaction to
1
behavior of the resulting amphiphiles were studied using yield compound 4, on treatment with ethanolic potassium
various spectroscopic and analytical techniques, i.e., NMR, IR, carbonate compound 4 undergoes chemo-selective aliphatic
UV-vis, uorescence spectroscopy, gel permeation chromatog- acid ester hydrolysis to yield compound 5. The dihydroxy
raphy (GPC), and DLS.
compound so obtained was puried by column chromatog-
raphy and then subjected for further hydrolysis using ethanol
and potassium hydroxide yielding diaryloxydiglycerol (6), which
was found to be sufficiently pure and suitable to act as
a precursor of central core (7) for the synthesis of amphiphiles
around it. Treatment of diaryloxydiglycerol (6) with propargyl
bromide in the presence of potassium carbonate yield dipro-
pargyl derivative 7, which was coupled with dodecanoic/
pentadecanoic acid using N-(3-dimethylaminopropyl)-N-ethyl-
carbodiimide hydrochloride (EDC$HCl) to yield compounds 8
and 9, respectively.
3.1. Synthesis and characterization
An A2B2 monomer (7) bearing a dialkyne system was rst
synthesized from diglycerol (2) by the procedure outlined in
Scheme 1.
Diglycerol in turn was synthesized from the coupling of
commercially available solketal with its mesyl derivative to yield
0
protected diglycerol (3,3 -oxybis(propane-1,2-diol)) (1). The
compound 1 was then hydrolyzed using cationic Dowex to yield
ꢁ
Scheme 2 Synthesis of hydrophilic moiety: (i) EDC$HCl, DMAP, DCM, 35 C, 12 h.
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ꢁ
3 3
Scheme 3 Synthesis of amphiphiles: (i) [Cu(PPh ) ]Br, DIPEA, DMF, 60 C, 24 h.
Azido-glycerol (10) and mPEG acids (11/12) were coupled very poor aqueous solubility and it exhibits prominent sol-
using EDC$HCl and DMAP (Scheme 2) to yield mPEG based vatochromic effect, it shows strong uorescence in hydrophobic
hydrophilic moieties (13/14). mPEG acids (11/12) and azido- environment, i.e., on encapsulation by supramolecular archi-
34
glycerol (10) in turn were synthesized following the earlier re- tectures. Furthermore, it was observed that at a specic
31,32
ported procedure by our group
Azide functionality onto the amphiphile concentration in aqueous medium, a noticeable
hydrophilic moiety (13/14) facilitated its coupling with the increment in the uorescent intensity of the dye was observed,
compound 8/9 simply by Click reaction (Scheme 3) to yield this is referred to as the minimum concentration at which the
amphiphiles 15–18 in quantitative yield.
molecules form aggregates (CAC). The plot of uorescence
intensity of encapsulated Nile red versus log[amphiphile
concentration] (Fig. S13, ESI†) provides the CAC value of the
amphiphiles. The CAC value of the synthesized amphiphiles
3.2. Physicochemical characterization and self-assembly
study of amphiphiles in aqueous medium
ꢀ6
ꢀ4
lies in the range of 3.994 ꢂ 10 to 1.140 ꢂ 10 M and it was
All of the synthesized amphiphiles (15–18) showed supramo- observed that by varying the mPEG from M : 350 to 550 led to
n
lecular aggregation behavior in aqueous medium. The critical the lowering of CAC i.e. the amphiphiles 15 and 16 consisting of
aggregation concentration (CAC) measurement of the resulting mPEG 550 hydrophilic moiety and C-12/C-15 alkyl chain have
micelles was performed by uorescence spectrophotometer. lower CAC values as compared to their corresponding
DLS measurements were used for determining the particle size. analogues 17 and 18 containing relatively smaller mPEG (Mn:
To have an idea about the morphology of the nanocarriers 350) units (Table 1). The HLB value of all the amphiphiles was
transmission electron microscopy (TEM) micrograph was also evaluated by the Griffin equation (Table 1). Furthermore,
recorded.
.2.1. Critical aggregation concentration measurement (15 and 16) having lower CAC with the previously reported tri-
using uorescence spectroscopy. The CAC of the synthesized aryloxytriglyceryl analogue 19/20 synthesized by earlier reported
a comparison of these diaryloxydiglycerol based amphiphiles
3
35
amphiphiles 15–18 was measured by uorescence spectropho- method shows that on moving from triaryloxytriglycerol
33
tometer, using Nile red as a uorescent probe. Nile red has
Table 1 Physico-chemical data of amphiphiles
DLS size (nm)
a
b
Amphiphile
Intensity
Volume
CAC (M)
HLB ¼ 20 ꢂ M
h
/MW
ꢀ
ꢀ
6
6
C-12/DG/mPEG-550 (15)
C-15/DG/mPEG-550 (16)
C-12/DG/mPEG-350 (17)
C-15/DG/mPEG-350 (18)
C-15/TG/mPEG-550 (19)
C-15/TG/mPEG-350 (20)
10.11
10.12
8.91
10.13
10.15
10.83
10.11
10.53
8.95
11.65
—
3.944 ꢂ 10
3.175 ꢂ 10
15.51
15.43
15.68
15.46
15.04
12.23
ꢀ
ꢀ
4
5
1.14 ꢂ 10
7.14 ꢂ 10
6.196 ꢂ 10
5.208 ꢂ 10
ꢀ
ꢀ
5
5
—
a
b
Molecular weight of hydrophilic part. Molecular weight of amphiphiles determined by GPC.
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Fig. 2 Structure of (a) diaryloxydiglycerol based and (b) triaryloxytriglycerol based amphiphilic architectures.
Table 2 Transport behavior of the amphiphiles for Nile red and nimodipine
Transport capacity
ꢀ1
ꢀ1
Transport efficiency (mg g
)
(mmol mol
)
Encapsulation efficiency (%)
Amphiphile
Nile red
Nimodipine
Nile red
Nimodipine
Nile red
Nimodipine
1
1
1
1
1
2
5
6
7
8
9
0
1.55
1.99
0.38
0.42
3.38
1.57
22.60
23.00
15.67
17.37
39.00
37.46
16.80
21.50
02.85
03.17
51.60
18.07
186.14
188.96
89.14
100.24
440.21
344.70
6.46
8.28
1.58
1.75
8.47
3.90
14.13
14.38
9.79
10.85
24.38
23.41
spacer to diaryloxydiglycerol spacer reduces the CAC (Fig. 2 and distribution plots of the amphiphiles are shown in Fig. 3. The
Table 1) and this improvement in CAC may be because of proper size distribution prole was monomodal in volume and
structural balance of hydrophobic and hydrophilic segments.
number, whereas it was bimodal in intensity. The two peaks
3.2.2. Aggregation, particle size, and morphological study present in the intensity distribution prole may be assigned to
of amphiphiles using DLS and TEM. DLS was used to study the micelles and micellar aggregates, whereas a single peak in
aggregation behavior and measure the hydrodynamic size of the volume and number could be corresponding to micelles. It
particles formed in aqueous medium by the amphiphiles at suggests that micellar aggregates are present in very small
ꢀ
1
a concentration of 5 mg mL (Table 1). The particle size of the proportion, whereas micelles are the predominant species in
aggregates was found to be ranging from 7 to 9 nm (Fig. 3) for all the aqueous solution. To check the long-term stability, we
of the four amphiphiles synthesized. Intensity and volume recorded DLS at different time intervals over a period of nearly
Fig. 3 DLS size distribution plots for the amphiphiles 15–18 in water (a) intensity distribution and (b) volume distribution.
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(Fig. 5). The assay results revealed that all the synthesized
amphiphiles are non-toxic up to
a
concentration of
ꢀ
1
0
0
.1 mg mL , though amphiphile 18 exhibits slight toxicity at
.5 mg mL (Fig. 5).
ꢀ
1
3.4. Transport studies
The signicant importance of nanocarriers in the eld of
biomedicine such as drug delivery motivated us to carry out the
encapsulation studies of the synthesized aqueous soluble
amphiphiles 15–18 using a model hydrophobic drug ‘nimodi-
pine’, a 1,4-dihydropyridine derivative and a well-known
calcium channel blocker. Also, it helps in maintaining the
37
cerebral blood ow in humans and animals. In addition,
a model hydrophobic dye Nile red was used for the evaluation of
the transport potential of the resulting amphiphilic systems.
Nile red encapsulation furnishes useful information about the
site of encapsulation in nanocarriers as it exhibits a strong
Fig. 4 TEM micrograph of amphiphile 16.
34
two weeks and didn't observe any noticeable change in the light emission in a lipophilic environment. Nile red and nimodi-
scattering data thus suggesting the nanoparticles to be stable pine encapsulation in the amphiphilic systems was accom-
34
enough. The formation of nano-sized aggregates of a size up to plished by either the lm method or solid dispersion
38
ꢀ1
2
00 nm is appropriate for biological applications as these can be method. An aqueous amphiphilic solution (5 mg mL ) was
used for prolonged delivery of therapeutic agents and enhanced used to encapsulate 0.12/0.5 mg of Nile red/nimodipine. The
36
drug uptake as compared to microparticles. The TEM micro- quantication of encapsulated dye/drug was achieved by
graph for amphiphile 16 (Fig. 4) shows micelles with a diameter lyophilization of the encapsulated samples and measurement
of nearly 6 nm. These results are in good agreement with the of their absorbance spectra aer re-dissolving in a known
DLS data, as the hydration shell does not contribute density in quantity of methanol (for Nile red) or ethanol (for nimodipine).
the visible assembly structure.
The transport efficiency (Fig. S14a, ESI†), transport capacity
(Fig. S14b, ESI†) and encapsulation efficiency of the synthesized
amphiphiles for the encapsulated Nile red/nimodipine (Table 2)
3
.3. Cytotoxicity study
were calculated by using the Beer–Lambert's law and the molar
Cytotoxicity data is crucial for consideration of an amphiphile
to be suitable for biomedical applications. The cytotoxicity
study for the synthesized amphiphiles 15–18 was carried out by
incubating the HeLa cells with amphiphiles at the concentra-
tion of 0.5, 0.1 and 0.05 mg mL and analyzed by the cell
viability measurement using the colorimetric CCK-8 assay
ꢀ1
ꢀ1
extinction coefficient (3) of 45 000 M cm at 552 nm for Nile
ꢀ1
ꢀ1
red in methanol or 7200 M cm at 356 nm for nimodipine in
39
ethanol.
Comparison of the transport potential i.e. the transport
efficiency, transport capacity and encapsulation efficiency of the
amphiphiles 15–18 for nimodipine and Nile red reveals that
longer (C-15) alkyl chain containing amphiphiles 16 and 18 are
better nano-transporters as compared to their analogues 15 and
ꢀ
1
17 with shorter (C-12) alkyl moiety, thus suggesting hydropho-
bicity to play a key role in enhancing the transport potential.
Similarly, while comparing the effect of PEG size, it was
observed that the amphiphiles 15 and 16 with larger hydrophilic
PEG (M
n
: 550) moiety have improved transport potential as
: 350) i.e. amphiphiles
7 and 18. Larger PEG improves the CAC for compounds 15 and
6 (ꢃ10 M) and the micelles formed are more stable and have
compared to those with smaller PEG (M
n
1
1
ꢀ
6
better encapsulation efficiency for Nile red and nimodipine, but
the amphiphiles 17 and 18 are not so efficient to encapsulate in
particular the highly hydrophobic dye Nile red due to their
lesser hydrophilic content and hence the difference in encap-
sulation efficiency for the mentioned guests i.e. dye and drug
nimodipine is large. However, these amphiphiles reported here
constituted from diaryloxydiglycerol core have inferior trans-
port potential as compared to the amphiphiles 19 and 20 con-
sisting of triaryloxytriglycerol core reported earlier by our group
Fig. 5 Cytotoxicity profile of amphiphiles 15–18 after 24 h using HeLa
cells. Each bar represents the mean value of three independent
experiments (n ¼ 3) and the standard deviation.
35
(Fig. 2).
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Fig. 6 Confocal laser scanning fluorescence microscopy images from HeLa cells after 4 h (a–d) and 24 h (e–h) incubation of Nile red
encapsulated in amphiphile 16. In the images, Nile red is shown in red color and blue color indicates the nucleus stained with Hoechst 33342. The
scale bar equals 50 mm.
Fig. 7 Study of release of encapsulated Nile red from nanocarrier 16 under physiological conditions by measuring the intensity of emission of
ꢁ
encapsulated dye at 37 C (a) in the absence of enzyme; and (b) in the presence of enzyme.
3
.5. Cellular uptake study
435 to investigate the time-dependent release of the encapsu-
lated guest from the core of nanocarriers by measuring uo-
rescence at regular intervals. It was observed that the complete
release of encapsulated dye takes place within 100 h, however
no noticeable release of encapsulated dye was observed in the
absence of the enzyme (Fig. 7).
Because of the observance of the highest encapsulation of Nile
red by amphiphile 16, this was shortlisted for further studying
the cellular uptake potential by confocal laser scanning
microscopy (cLSM) using HeLa cells. The cLSM images (Fig. 6)
show that aer 4 h of incubation, a strong signal is seen inside
the cell's cytosol. Aer 24 h an increase of the intensity of Nile
red was seen, which indicate that Nile red is accumulating in 4. Conclusions
cells with time. These results indicate that the amphiphile is
well suited as a drug delivery system.
A new series of diaryloxydiglycerol-based amphiphiles have
been designed and synthesized using a biocompatible starting
material like glycerol, p-hydroxybenzoic acid, and mPEG, these
self-assemble into supramolecular architectures. All the
3.6. Enzyme-triggered release of encapsulated guest
Besides encapsulation and cellular uptake, triggering the synthesized amphiphiles were completely characterized by IR,
1
13
release of guest in a controlled manner is of paramount
H and C-NMR spectra, and GPC techniques. Investigation of
importance. Since the amphiphiles contain ester functionality, the self-assembly behavior of the synthesized amphiphiles was
we employed a general de-esterication method using Novozym carried out using DLS, which conrmed that amphiphiles form
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small-sized aggregates with hydrodynamic diameter in the 8–
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1 nm range and form aggregates at low concentration of the
ꢀ
4
ꢀ6
order of 10 to 10 M. The TEM study of amphiphile also
conrmed the formation of aggregates in nm range. For eval-
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ꢁ
investigated. The present data testify the potential of these
newer amphiphiles for the design and development of efficient
nanocarriers for biomedical applications.
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Conflicts of interest
There are no conicts to declare.
2
2 R. S. G. Krishnan, S. Thennarasu and A. B. Mandal, J. Phys.
Chem. B, 2004, 108, 8806–8816.
Acknowledgements
The authors gratefully acknowledge the nancial support from 23 B. Trappmann, K. Ludwig, M. R. Radowski, A. Shukla,
DST, Government of India, and DFG, Germany for supporting
a collaboration research project (Grant No. INT/FRG/DFG/P-03/
A. Mohr, H. Rehage, C. B ¨o ttcher and R. Haag, J. Am. Chem.
Soc., 2010, 132, 11119–11124.
2017). The authors would like to thank Elisa Quaas for per- 24 K. Urata, Eur. J. Lipid Sci. Technol., 2003, 105, 542–556.
forming cell viability experiments. The authors would also like 25 M. O. Sonnati, S. Amigoni, E. P. Taffin de Givenchy,
to acknowledge CSIR-UGC, New Delhi for providing fellowships
to Parmanand, Aarti and Ayushi Mittal and the assistance of the
Core Facility BioSupraMol supported by the DFG.
T. Darmanin, O. Chouletb and F. Guittard, Green Chem.,
2013, 15, 283–306.
26 H. Baumann, M. B u¨ hler, H. Fochem, F. Hirsinger,
H. Zoebelein and J. Falbe, Angew. Chem., Int. Ed. Engl.,
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