Synthesis and characterization of β-lactam functionalized superparamagnetic Fe3O4@SiO2 nanoparticles as an approach for improvement of antibacterial activity of β-lactams

Article abstract of DOI:10.1039/c6ra03634a

In this paper, we reported, for the first time, a new multistep method for preparing β-lactam functionalized Fe₃O₄@SiO₂ nanoparticles with high saturation magnetization. The synthesized nanostructures were characterized by

Full text of DOI:10.1039/c6ra03634a

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Synthesis and characterization of β-lactam functionalized
superparamagnetic Fe3O4@SiO2 nanoparticles as an approach for
improvement of antibacterial activity of β-lactams
Mohsen Esmaeilpour(1), Ali Reza Sardarian(1)∗, Aliasghar Jarrahpour(1), Edris Ebrahimi(1),
Jaber Javidi(2,3)
(1) Chemistry Department, College of Sciences, Shiraz University, Shiraz, Iran
(2) Department of Pharmaceutics, School of Pharmacy, Shahid Beheshti University of
Medical Sciences, Tehran, Iran
(3) Students Research Committee, School of Pharmacy, Shahid Beheshti University of
Medical Sciences, Tehran, Iran
*Corresponding author. Tel.: +98 7116137107, fax: +98 7112286008.
Eꢀmail addresses: asardarian55@shirazu.ac.ir (A.R. Sardarian)
Abstract
In this paper, we reported, for the first time, a new multistep method for preparing βꢀlactam
functionalized Fe3O4@SiO2 nanoparticles with high saturation magnetization. The
synthesized nanostructures were characterized by FTꢀIR, XRD, TEM, FEꢀSEM, TGA, DLS,
N2 adsorption–desorption isotherm analysis, elemental analysis, NMR and Mass
spectroscopy. Also, the magnetic property of these Fe3O4 nanoparticles allowed simple
separation of these nanoparticles from the reaction mixture by an external magnetic field. βꢀ
Lactams (2a-f) and nano Fe3O4@SiO2/βꢀlactams (3a-f) were tested against Gramꢀpositive S.
aureus (ATCC 25923) and Gramꢀnegative Escherichia coli (ATCC 25922) and results
showed the minimum inhibitory concentrations (MICs) of 3a-f were less than 2a-f.
Keywords:
βꢀLactam; [2+2] Cycloaddition; Coreꢀshell; Fe3O4@SiO2; Superparamagnetism;
Antibacterial activity
1. Introduction
Invasive all bacterial, fungal and viral infections are a serious and escalating health
issue. Current therapies are limited in safety and resistant fungi, bacteria, and viruses
are an emerging problem.1 It is widely recognized that there is a need for the
optimization of pharmacological properties or development of new drugs that have a
different mode of action to those currently in use.2
βꢀLactam antibiotics have played an important role in antibacterial drugs and in
medicinal chemistry.3ꢀ5 βꢀLactams are not only useful fragments of antibiotics, but are
also used as intermediates and synthons for the production of several organic
compounds.6ꢀ9 They have been widely used as chemotherapeutic agents for treating
microbial diseases.10ꢀ11 They also show many other interesting biological properties,
such as antiꢀHIV,12 anti malarial activities,13 antitumor,14 antiꢀhyperglycemic,15 antiꢀ
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inflammatory, analgesic activities,16 cholesterol absorption inhibitors,17 thrombin
inhibitors,18 serineꢀdependent enzyme inhibitors19 and human cytomegalovirus
protease inhibitors.20 Due to importance of βꢀlactams several synthetic methods have
been developed for the preparation of the βꢀlactam ring21ꢀ25 and among the several
methods, the [2+2] cycloaddition reaction of Schiff bases with ketenes (Staudinger
reaction) is mostly applied.26 The ketenes are commonly generated in situ from acyl
halides or activate carboxylic acids in the presence of tertiary amines.27ꢀ29 The activate
carboxylic acids are conventionally useful when the acid halides are not commercially
available, difficult to prepare or when they are unstable.30 Some acid activating agents
include trifluoroacetic anhydride,31 triꢀphosgene,32 cyanuric chloride,33 1,1ꢀ
carbonyldiꢀimidazole,34 phosphorusꢀderived reagents,35 acetic anhydride,36
Mukaiyama reagent37 and thionyl chloride (or oxalyl chloride).38
Nanomedicine as drug delivery vehicles have been designed and synthesized that can
carry drug and efficiently cross physiological membranes to reach target sites.39 The
most representative nanoscale carriers include gold nanoparticles,40 liposomes,41
quantum dots,42 magnetic nanoparticles,43 polymeric nanoparticles,44 carbon
nanotubes,45 engineered viral nanoparticles,46 nucleic acidꢀbased nanoconstructs47 and
dendrimers.48
In last decades, magnetic nanoparticles have attracted much attention because of their
unique physioꢀchemical properties and potential applications such as medical
diagnostics and therapeutics,49,50 data storage,51 environmental remediation,52
magnetic resonance imaging (MRI)53,54 and catalysis.55
Because of biological restrictions, such as avoiding toxic materials or using
sufficiently low frequencies and field amplitudes to prevent the formation of eddy
currents inside the patient’s body, several papers have focused on magnetic
nanostructures,56ꢀ58 in particular, magnetite Fe3O4 nanoparticles. These nanoparticles
have shown significant attractive for the preparation of immobilized derivative
penicillin G, cephalosporin and amoxicillin because of the easy and complete
separation from the reaction mixture by applying a magnetic field.59ꢀ61 Using
magnetite nanosystems have been investigated to improve the efficiency of current
antimicrobials with proved effect.62
For many applications, magnetic nanoparticles are suitable to be chemically stable and
uniform in size to prevent their aggregation, which is happened due to their nanoscale
and strong interaction among them. This problem can be solved by coating of
magnetite nanoparticles with a silica layer as the stabilizer, which prevents direct
contact between the nanoparticles. Furthermore, it provides the abound hydroxyl
groups on the surface of composite particles and the opportunity to conjugate various
function molecules for many special applications.63,64
Recently, magnetic coreꢀshell materials have gained much attention and undergone
intensive investigation for their unique potential applications in medicinal, low
cytotoxicity, chemically modifiable surface, magnetic responsively, good stability,
optical, biological, environmental and chemical areas.65,66 On the other hand, coreꢀ
shell nanostructure magnetic catalysts could be easily separated conveniently and
economically using an external magnetic field.66
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Therefore, regarding to the previous report on the synthesis of functionalized iron
nanoparticlesꢀpenicillin conjugates to combat the rapid emergence of βꢀlactamase
resistance,67 we decided, herein to use Fe3O4 nanoparticles, which have high saturation
magnetization, for preparation of βꢀlactam functionalized Fe3O4@SiO2 nanoparticles
and then characterize their structure and properties by different techniques such as FTꢀ
IR, XRD, TEM, FEꢀSEM, TGA, DLS, N2 adsorption–desorption isotherm analysis,
elemental analysis, NMR and Mass spectroscopy. Finally, the antibacterial activity of
βꢀlactam (2a-f) and βꢀlactam functionalized Fe3O4@SiO2 nanoparticles (3a-f) were
tested against gramꢀpositive S. aureus (ATCC 25923) and gramꢀnegative Escherichia
coli (ATCC 25922) bacterial strain.
.
2. Results and discussion
2.1. Characterization of β-lactam functionalized Fe3O4@SiO2 nanoparticles
In this paper, the synthesis of βꢀlactam functionalized Fe3O4@SiO2 nanoparticles are
reported for the first time to the best of our knowledge on the basis of the reactions
presented in Scheme1.
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OH
O
SiO2
O
O
O
HO
O
OH
OH
O
O
SiO2
O
HO
HO
OH
OH
O
O
O
SiCH2CH2CH2NH2
HO
Fe3O4
(EtO)3SiCH2CH2CH2NH2
EtOH, reflux
Fe3O4
O
O
O
O
O
O
O
HO
HO
(1)
O
OH
O
O
O
OH
OH
O
O
OH
CHO
OCH3
CH2Cl2(dry), Et3N, 0 oC to rt
CH2=CHCOCl
EtOH
+
N
N
Reflux
OH
NH2
(1b)
(1a)
OCH3
OCH3
CO2H
O
or
O
ROCH2CO2H
O
CH2Cl2 (dry), Et3N, TsCl, rt
O
O
O
RO
or
N
N
O
O
2b, 3b: R=Me
2c, 3c: R=Ph
2d, 3d: R=4-Cl-C6H4
2e, 3e: R=2,4-Cl-C6H3
2f, 3f: R=2-Naphthyl
OCH3
OCH3
(2a)
(2b-2f)
(1)
+
THF, 50 o
C
H3CO
H3CO
O
O
N
N
O
SiO2
O
SiO2
O
O
OR
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
Fe3O4
Fe3O4
O
Si-(CH2)3-NHCH2CH2CO
O
Si-(CH2)3-NHCH2CH2CO
HO
HO
O
O
O
O
O
O
O
O
O
O
HO
HO
O
O
O
O
O
O
O
O
O
(3b-3f)
O
(3a)
Scheme1. Process for preparation of βꢀlactam functionalized Fe3O4@SiO2 nanoparticles.
Acrylatedꢀβꢀlactams 2a-f were synthesized from acrylatedꢀSchiff base 1b and acetic
acid derivatives. For synthesis of Schiff base 1a a mixture of 4ꢀmethoxyaniline and 4ꢀ
hydroxybenzaldehyde was refluxed in ethanol. In the next step acrylatedꢀSchiff base
1b was achieved from Schiff base 1a and acryloyl chloride in the presence of Et3N in
o
dry CH2Cl2 at 0 C to room temperature. The acrylatedꢀSchiff base 1b was used to
synthesize acrylatedꢀβꢀlactams 2a-f by modified [2+2] keteneꢀimine cycloaddition
reactions (Staudinger) in the presence of pꢀtoluenesulfonyl chloride and Et3N in dry
CH2Cl2 at room temperature. The acrylatedꢀβꢀlactams 2a-f were characterized by
spectral analyses. The cis and trans stereochemistry of 2ꢀazetidinones were realized
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from the coupling constants of Hꢀ3 and Hꢀ4 (J3,4> 4.0 Hz for the cis and J3,4< 3.0 Hz
for the trans stereoisomer).68
As a model, IR spectrum of 2c showed a sharp band at 1762 cmꢀ1 for the βꢀlactam
carbonyl which is a proof of the βꢀlactam ring and absorption at 1682 cmꢀ1 for the
carbonyl of the acrylate. The 1HꢀNMR spectrum of 2c displayed two doublets for Hꢀ3
and Hꢀ4 of βꢀlactam ring at 5.55 ppm (d, J= 4.70, 1H) and 5.36 ppm (d, J= 4.70, 1H),
respectively. The detected coupling constants of these protons established the cis
13
stereochemistry for this compound. The CꢀNMR spectrum of compound 2c showed
the βꢀlactam carbonyl peak at 164.1 ppm. In addition, the carbon of methoxy group,
Cꢀ4 and Cꢀ3 of βꢀlactam ring appeared at 55.4, 61.4 and 81.1 ppm, respectively.
Magnetic nanoparticles coated by 3ꢀ(triethoxysilyl)ꢀpropylamine (Fe3O4@SiO2ꢀNH2)
(1) was prepared by addition of 3ꢀ(triethoxysilyl)ꢀpropylamine to dispersed powder of
Fe3O4@SiO2 in ethanol. After 12h reflux, suspension of Fe3O4@SiO2ꢀNH2 was
separated with the external magnetic field, washed with ethanol and water and dried at
80 oC.
Finally, to synthesize βꢀlactam functionalized Fe3O4@SiO2 nanoparticles
(Fe3O4@SiO2/βꢀlactam) (3a-f), Fe3O4@SiO2ꢀNH2 (1) was added to the solution of
o
acrylateꢀβꢀlactams in THF and resulting mixture was stirred at 50 C for 5 h. After
that, the product was removed by an external magnetic field, washed with ethanol and
dried at 70 ◦C.
Table 1 depicts the TGA results of Fe3O4@SiO2/βꢀlactam nanoparticles under a
nitrogen atmosphere. Based on the weight loss analysis given in Table1, the
percentages of organic compounds (βꢀlactam) in Fe3O4@SiO2/βꢀlactam nanoparticles
are 16.5ꢀ21.3 %.
N2 adsorption–desorption isotherm analysis provide information on the specific
surface area and porosity of the prepared samples. Adsorption–desorption isotherm
measurements were conducted with N2 for the Fe3O4@SiO2/βꢀlactam nanoparticles
and result shown in Table1. BET surface area measurements have revealed that all
samples present the adsorption isotherms characteristic of nanoparticles and show a
similar surface area of ca. 410ꢀ430 m2g−1.
Table 1. Structures of βꢀlactams (2a-f), Fe3O4@SiO2/βꢀlactams (3a-f) and their properties.
Properties
Entry βꢀlactam
Fe3O4@SiO2/βꢀlactam
Functionalization Surface area
(%)a
(m2gꢀ1)b
21.3 ± 0.02
415.2
1
(2a)
(3a)
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17.3± 0.04
424.0
2
3
4
(2b)
(2c)
(2d)
(3b)
18.8± 0.05
416.5
(3c)
16.5± 0.02
18.1± 0.03
19.2± 0.04
417.1
(3d)
(3e)
(3f)
410.5
5
(2e)
428.0
6
(2f)
aFunctionalized percentages were evaluated using thermogravimetric analysis.
bSurface areas were evaluated from the N2 adsorption isotherm.
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The binding of βꢀlactam on surfaces of Fe3O4@SiO2 nanoparticles was confirmed by
FTꢀIR spectroscopy. Fig. 1 shows the FTꢀIR spectra of Fe3O4, Fe3O4@SiO2,
Fe3O4@SiO2ꢀNH2, βꢀlactam compounds and Fe3O4@SiO2/βꢀlactam in the 500ꢀ4000
cm−1 wave number range.
For pure magnetic nanoparticles exhibit a strong band at 570 cm−1, characteristic of
the FeꢀO vibration correlated to the magnetic core and the peaks at around 3400 cmꢀ1
and 1621 cmꢀ1 are due to the OꢀH stretching and deforming vibrations of adsorbed
water in the sample (Fig.1a).69,70 For all samples, the absorption peak at 570ꢀ580 cm−1
is observed, corresponding to the FeꢀO vibration from the magnetite phase. The
surfaces of pure Fe3O4 nanoparticles were readily covered with SiO2 layers. The
adsorption peaks at 1100 and 780 cm−1 corresponds to the antisymmetric and
symmetric stretching vibration of SiꢀOꢀSi bond in oxygenꢀsilica tetrahedron,
respectively.71 In Fig. 1b, the unfunctionalized silica coated magnetite nanoparticles
show stretches at 569, 1000ꢀ1150 and 3300 cmꢀ1, which can be attributed to the FeꢀO,
SiꢀOꢀSi, and ꢀOH bonds, respectively. Fig.1c shows the FTꢀIR spectrum of
Fe3O4@SiO2ꢀNH2 nanoparticles, the peaks at 570, 1000ꢀ1150, 1400ꢀ1420 and 1561
cm−1 are attributed to FeꢀO (stretching vibration), SiꢀOꢀSi (asymmetric stretching), Cꢀ
N (stretching vibration) and NꢀH (bending), respectively. Also, the presence of several
bands with medium intensity in 28010ꢀ2986 cmꢀ1 and 3050ꢀ3250 regions are allocated
to CꢀH stretching of propyl group and NꢀH stretching (Fig.1c).
Fig.1dꢀi shows the FTꢀIR spectrum of βꢀlactam compounds, the presence of
absorbencies at 2860ꢀ3087, 1749ꢀ1762, 1670ꢀ1690, 1600ꢀ1630, 1480ꢀ1600, 1380ꢀ
1390, 1200ꢀ1310, 1100ꢀ1200 are attributed to CH (stretching), C=O (amide
stretching), C=O (ester stretching), C=C (acrylate stretching), C=C (aromatic ring
stretching), CH3 (bending), CꢀO (stretching) and CꢀN (stretching), respectively. From
the IR spectra presented in Fig.1jꢀo, the absorption peaks at 570ꢀ580 cm−1 belonged to
the stretching vibration mode of FeꢀO bonds in Fe3O4, the absorption peak presented
at 1000ꢀ1150 cm−1 due to stretching vibration of framework and terminal SiꢀOꢀ
groups. The presence of vibration bands in 3400 (OꢀH stretching), 2850ꢀ3090 (CꢀH
stretching), 1680ꢀ1750 (C=O amid and ketone stretching), 1560ꢀ1570 cm−1 (NꢀH
bending), 1480ꢀ1600 (C=C aromatic ring stretching) and 1380ꢀ1390 (CH3 bending)
demonstrates the existence of βꢀlactam supported on Fe3O4@SiO2 nanoparticles in the
spectrum (Fig.1jꢀo).
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Fig 1. FTꢀIR spectra of Fe3O4 (a), Fe3O4@SiO2 (b), Fe3O4@SiO2ꢀNH2 (c), βꢀlactam (2d) (d),
βꢀlactam (2e) (e), βꢀlactam (2b) (f), βꢀlactam (2c) (g), βꢀlactam (2f) (h), βꢀlactam (2a) (i),
Fe3O4@SiO2/βꢀlactam (3d) (j), Fe3O4@SiO2/βꢀlactam (3e) (k), Fe3O4@SiO2/βꢀlactam (3b)
(l), Fe3O4@SiO2/βꢀlactam (3c) (m), Fe3O4@SiO2/βꢀlactam (3f) (n) and Fe3O4@SiO2/βꢀlactam
(3a) (o).
The crystalline structures of Fe3O4, Fe3O4@SiO2 and βꢀlactam supported on
superparamagnetic Fe3O4@SiO2 nanoparticles (3a) were studied by Xꢀray diffraction
(XRD) analysis (Fig.2). The position and relative intensities of all peaks confirm well
with standard XRD pattern of Fe3O4 (JCPDS card No. 85ꢀ1436) indicating retention
of the crystalline cubic spinel structure during functionalization of MNPs.64 The
characteristic peaks at 2Ө= 30.1◦, 35.4◦, 43.1◦, 53.4◦, 57◦ and 62.6 for pure Fe3O4
nanoparticles, which were marked respectively by their indices (220), (311), (400),
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(422), (511), and (440), were also observed for Fe3O4@SiO2 and Fe3O4@SiO2/βꢀ
lactam (3a) nanoparticles (reference JCPDS card no.19ꢀ629).72,73 This revealed that
modification on the surface of Fe3O4 nanoparticles did not lead to their phase change.
Fig 2. XRD patterns of Fe3O4 (a), Fe3O4@SiO2 (b) and Fe3O4@SiO2/βꢀlactam (3a) (c).
The XRD pattern of Fe3O4@SiO2 nanoparticles presented a broad featureless XRD
peak at low diffraction angle (2Ө=15–25◦), which corresponded to the amorphous
state SiO2 shells (Fig.2b). For Fe3O4@SiO2/βꢀlactam (3a) nanoparticles, the broad
peak was transferred to lower angles due to the synergetic effect of amorphous silica
and βꢀlactam (Fig.2c). The mean size of the crystallites was calculated by applying
Scherer's equation: D= 0.9λ/β cosƟ, where D is the average diameter in A˚, λ is the
wavelength of the Xꢀrays, β is the broadening of the diffraction line measured at half
of its maximum intensity in radians and Ɵ is the Bragg diffraction angle. The peak at
2Ө= 35.4◦ is chosen to calculate the crystallite size, according to the result calculated
by Scherrer equation, it is found that the diameter of Fe3O4 nanoparticles obtained is
about 12 nm.
Transmission electron microscopy (TEM) was employed to characterize the
morphology and size of Fe3O4 and Fe3O4@SiO2. Fig.3a showed that the Fe3O4
nanoparticles had uniform spherical morphology with a uniform size of about 12 nm,
corresponding with the result calculated by Scherrer equation.64 After treatment by the
modified Stöber's reaction, the Fe3O4 particles were completely covered with a
uniform transparent silica layer.
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Fig 3. TEM images of a) Fe3O4, b) Fe3O4@SiO2 and FEꢀSEM images of c) Fe3O4@SiO2/βꢀ
lactam (3a), d) Fe3O4, e) Fe3O4@SiO2 and the size distributions of f) Fe3O4, g) Fe3O4@SiO2
and h) Fe3O4@SiO2/βꢀlactam, respectively.
Furthermore, the particle size is roughly increased to 20 nm. The mesoporous silica
shell on the surface of Fe3O4 is quite homogeneous and exhibits good monodispersity
with estimated thickness of 8 nm.64
The morphology and size of Fe3O4, Fe3O4@SiO2 and Fe3O4@SiO2/βꢀlactam (3a)
nanoparticles were also observed by FEꢀSEM (Fig. 3). Uniform nanospheres of Fe3O4
with a diameter of approximately 15 nm were observed in Fig. 3d. The FEꢀSEM
images indicate agglomerations of particles with homogenous size and the successful
coating of the magnetic Fe3O4 particles (Fig. 3c,e). Fig. 3b and c shows that the
Fe3O4@SiO2 and Fe3O4@SiO2/βꢀlactam (3a) nanoparticles are semispherical with an
average size of 15ꢀ25 and 40ꢀ50 nm, respectively.
The hydrodynamic diameter of the Fe3O4, Fe3O4@SiO2 and Fe3O4@SiO2/βꢀlactam
(3a) nanoparticles is determined by DLS technique. This size distribution is centered
at a value of 12, 20 and 35 nm for Fe3O4, Fe3O4@SiO2 and Fe3O4@SiO2/βꢀlactam
(3a), respectively (Fig 3f to h).
Fig. 4A depicts the TGA results of Fe3O4@SiO2 and Fe3O4@SiO2/βꢀlactam (3a) under
a nitrogen atmosphere. The samples were measured in the condition of nitrogen
atmosphere at the heating rate of 20oC/min until the temperature elevated to 650 oC. In
the case of Fe3O4@SiO2 nanoparticles the weight loss between 50 and 150 ◦C is due
to loss of physically adsorbed water molecules (Fig.4Aa). Meanwhile, the weight loss
above 200 ◦C was also possibly caused by the loss of structural water within
amorphous SiO2.74
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In this way, the slow slope appeared at the temperature range of 200ꢀ650 ◦C in the
TGA curve of Fe3O4@SiO2 (Fig.4Aa) can be explained. Fe3O4@SiO2/βꢀlactam shows
twoꢀstep weight loss behavior (Fig4.Ab). The initial weight loss 3.1 % from the
o
Fe3O4@SiO2/βꢀlactam up to 130 C is due to the removal of physically adsorbed
solvent and surface hydroxyl groups. The two stages can be ascribed to the
decomposition of βꢀlactam and organic volatile compounds. For Fe3O4@SiO2/βꢀ
o
lactam (3a), the mass loss of about 18.2 % by weight in the range of 150ꢀ450 C is
attributed to the decomposition of βꢀlactam (2a) and the temperature of the maximum
weight loss is 420 oC.
Fig 4. A) Thermogravimetric analysis of Fe3O4@SiO2 (a) and Fe3O4@SiO2/βꢀlactam (3a)
o
nanoparticles (b); B) Magnetization curves at 300 K for Fe3O4 (a), Fe3O4@SiO2 (b) and
Fe3O4@SiO2/βꢀlactam (3a) nanoparticles (c); C) Magnetic separation image of Fe3O4
@SiO2/βꢀlactam by an external magnet.
The magnetic property of the obtained samples was investigated using a vibrating
sample magnetometer. The magnetic hysteresis loop of the magnetic nanoparticles
o
Fe3O4, Fe3O4@SiO2 and Fe3O4@SiO2/βꢀlactam (3a) measured at T= 300 K is shown
in Fig. 4Ba,b,c and indicate that the magnetization saturation values of Fe3O4,
Fe3O4@SiO2 and Fe3O4 @SiO2/βꢀlactam (3a) are 62.4, 39.2 and 30.7 emu/g,
respectively. It indicated that all products had superparamagnetism. No hysteresis
curve was observed at the low magnetic field in the case of nanoparticles, and it was
o
completely reversible at 300 K. The magnetic reduction of the functionalized Fe3O4
nanoparticles was mostly attributed to the coating layer of the silica and βꢀlactam on
the surface of Fe3O4 nanoparticles. Nevertheless, the βꢀlactam supported on
superparamagnetic Fe3O4@SiO2 can still be separated from the solution by using an
external magnetic field on the sidewall of the reactor. As shown in Fig.4C inset, the
magnetic separation was quickly fulfilled by supplying an external magnetic field near
the suspension system of Fe3O4@SiO2/βꢀlactam.
2.2. Antibacterial activities
The antibacterial activity of βꢀlactam (2a-f) and βꢀlactam supported on Fe3O4@SiO2
nanoparticles (3a-f) against gramꢀpositive S. aureus (ATCC 25923) and gramꢀ
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negative Escherichia coli (ATCC 25922) bacterial strain were tested according
reported method.75 The minimum inhibitory concentrations (MICs) were defined as
the lowest concentrations of the βꢀlactams (2a-f) and βꢀlactam supported on
Fe3O4@SiO2 nanoparticles (3a-f) that prevented visible growth and results were
shown in Table 2. Also, standard antibacterial Fe3O4@SiO2 nanoparticles were tested
under the similar conditions for comparison. The results showed that Fe3O4@SiO2
nanoparticles have no antibacterial activity against E. coli. The significant decrease of
the MIC value for Fe3O4@SiO2/βꢀlactams suggests that the magnetic nanoparticles
have improved the antibacterial activity of prepared βꢀlactams. The antibacterial
activity of the functionalized Fe3O4@SiO2 is related to the increasing of reactive
oxygen species (ROS) which could damage the DNA of the bacterial cells and inhibit
particular enzyme activities that are vital for cell growth without harming the human
cells.76,77 These results indicated when βꢀlactams were connected covalently to
Fe3O4@SiO2 magnetic nanoparticles, a synergic effect was observed and the
antibacterial inhibition of βꢀlactams were improved and among the Fe3O4@SiO2/βꢀ
lactams, those with the aryl substitution with chlorine atom on Cꢀ3 of βꢀlactam ring
enhance the antibacterial activity.
Table 2. Antimicrobial activity of the βꢀlactams (2a-f) and Fe3O4@SiO2/βꢀlactams (3a-f)
(MIC, µg /mL).
Compound
S. aureus
E. coli
100
100
100
100
50
Compound
S. aureus
25
E. coli
50
100
50
25
12.5
50
50
25
25
50
50
50
100
2a
2b
2c
2d
2e
2f
3a
3b
3c
3d
3e
3f
12.5
12.5
50
12.5
25
100
naa
Fe3O4@SiO2
ana= no activity.
3. Conclusions
In summary, we have successfully prepared several novel βꢀlactam functionalized
Fe3O4@SiO2 nanoparticles for the first time. The FTꢀIR and TGA results
demonstrated the formation βꢀlactams supported on superparamagnetic Fe3O4@SiO2
nanoparticles. Both TEM and FEꢀSEM indicated that the Fe3O4@SiO2 nanoparticles
have been wellꢀcoated with βꢀlactams. XRD showed the significant effects of the
Fe3O4 NPs on the crystallization behavior of the Fe3O4@SiO2/βꢀlactams. The
vibrating sample magnetometer test showed that the saturation magnetization of the
Fe3O4@SiO2/βꢀlactam (3a) was 30.7 emu/g and the presence of an external magnetic
field would facilitate the separation of the Fe3O4@SiO2/βꢀlactams from the reaction
mixture. Also, the results of antimicrobial activity study signified that supporting of βꢀ
lactams on superparamagnetic Fe3O4@SiO2 nanoparticles provide a synergic effect
and improve their antibacterial inhibition.
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4. Experimental
4.1. Material and methods
The reagents and solvents used in this work were obtained from Fluka or Merck and
used without further purification. Fourier transform infrared spectroscopy (FTꢀIR)
analysis of the samples was taken on a Shimadzu FTꢀIR 8300 spectrophotometer and
the sample and KBr were pressed to form a tablet. NMR spectra were recorded on a
Bruker avance DPX 250 MHz spectrometer in CDCl3 or DMSOꢀd6 using
tetramethylsilane (TMS) as an internal reference. The phase formation and
crystallographic state of magnetic nanoparticles were determined by Bruker AXS D8ꢀ
advance Xꢀray diffractometer with Cu Kα radiation (λ=1.5418). The size and
morphology of the nanoparticles were observed using a Philips EM208 transmission
electron microscope (TEM) with an acceleration voltage 100 kV. The nanoparticles
were thoroughly dispersed in water by ultraꢀsonication and placing a drop of solution
on the carbon coated copper grid. Field Emission Scanning Electron Microscopy (FEꢀ
SEM) images were obtained on HITACHI Sꢀ4160. The hydrodynamic size of the
particle was measured by dynamic light scattering (DLS) techniques, using a
HORIBAꢀLB550 particle size analyzer. The BET surface area and porosity of
catalysts were determined from nitrogen physisorption measured on a Micromeritics
ASAP 2000 instrument at ꢀ196 oC. Thermogravimetric analysis (TGA) was carried out
using Perkin Elmer with N2 carrier gas and the rate of temperature change of 20 ºC
minꢀ1. The magnetic properties of the composite nanoparticles were measured by
o
BHVꢀ55 vibrating sample magnetometer (VSM) 298 K. Melting points were
determined on a MelꢀTemp apparatus and are Uncorrected. Elemental analysis was
done on a 2400 series PerkinꢀElmer analyzer. The mass spectra were recorded on a
Shimadzu GCꢀMS QP 1000 EX instrument. Determination of the purity of the
substrate and monitoring of the reaction were accomplished by thinꢀlayer
chromatography (TLC) and purification was achieved by silica gel column
chromatography.
4.2. General procedure
2.2.1. Preparation of Fe3O4@SiO2 coreꢀshell
The coreꢀshell Fe3O4@SiO2 nanospheres were prepared by a modified Stober method
in our previous work.78, 79
4.2.2. Preparation of magnetic nanoparticles coated by (3ꢀaminopropyl)ꢀ
triethoxysilane (Fe3O4@SiO2ꢀNH2)
The obtained Fe3O4@SiO2 powder (1 g) was dispersed in 10 mL ethanol solution by
sonication for 20 min, and then 3ꢀaminopropyl (triethoxy) silane (2 mmol, 0.352 g)
13

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was added to the mixture. After mechanical stirred under reflux conditions for 12 h,
the suspended substance (Fe3O4@SiO2ꢀNH2) was separated with the external magnetic
field. Then, the product was washed with ethanol and water to remove no reacted
species and dried at 80 oC for 6 h.
4.2.3. General procedure for the preparation of Schiff base 4ꢀ(((4ꢀmethoxy phenyl)
imino) methyl) phenol (1a)
A mixture of 4ꢀmethoxyaniline (1 mmol) and 4ꢀhydroxybenzaldehyde (1 mmol) was
refluxed in ethanol (20 mL) for 5 hours. After cooling, the resulting Schiff base, as the
gray precipitate, was separated by filtration and washed with ethanol (5 mL) and then
dried in vacuum. The crude product was recrystallized from ethanol to obtain the pure
product in 88 % yield.
4.2.4. General procedure for the preparation of 4ꢀ(((4ꢀmethoxyphenyl) imino) methyl)
phenyl acrylate (1b)
To the solution of 1a (1 mmol) in 10 mL of CH2Cl2 was added triethylamine (2.2
mmol). Acryloyl chloride (2.2 mmol) was added dropwise to the solution at 0 oC. The
resulting solution was stirred at room temperature for 15 minutes, and then washed
with H2O (2×10 mL). The organic layer was dried with anhydrous MgSO4, filtered,
and evaporated. The crude of acrylate imine 1b, as oil, was used for the next step.
4.2.5. General procedure for the preparation of acrylateꢀβꢀlactams (2aꢀf)
A mixture of crude Schiff base 1b, triethylamine (5 mmol), 9Hꢀxanthenꢀ9ꢀcarboxylic
acid or derivatives of oxyacetic acid (1.5 mmol) and tosyl chloride (1.5 mmol ) in dry
CH2Cl2 (15 mL) was stirred at room temperature for overnight. Then it was washed
with HCl 1N (20 mL), saturated NaHCO3 (20 mL) and brine (20 mL). The organic
layer was dried over Na2SO4, filtered and the solvent was evaporated to give the
product as a solid which was then purified by column chromatography
(EtOAc/Petroleum ether (8/2)).
4.2.6. General procedure for the preparation of βꢀlactam functionalized Fe3O4@SiO2
nanoparticles (Fe3O4@SiO2/βꢀlactam) (3aꢀf)
Fe3O4@SiO2ꢀNH2 (1 g) was added to the solution of acrylateꢀβꢀlactams (1 mmol) in
THF (5 mL) and the resultant mixture was stirred at 50 oC for 5 h. The resulting solid
was removed by an external magnetic field. Then the solid was washed with ethanol
to eliminate any impurities in the solid and dried at 70 ◦C for 4 h. FTꢀIR (KBr pellets,
cm−1): Fe3O4@SiO2/βꢀlactam (3a): 3400 (OꢀH), 2846ꢀ3070 (CꢀH stretching), 1690ꢀ
1750 (overlap 2C=O amide and ester, stretching), 1480ꢀ1600 (C=C aromatic ring),
1462 (CH2 bending), 1396 (CH3 bending), 1000ꢀ1150 (SiꢀOꢀSi asymmetric
stretching), 571 (FeꢀO stretching). Fe3O4@SiO2/βꢀlactam (3b): 3400 (OꢀH), 2854ꢀ
3076 (CꢀH stretching), 1736 (C=O amide, stretching), 1691 (C=O ester, stretching),
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1480ꢀ1600 (C=C aromatic ring), 1464 (CH2 bending), 1374, 1395 (2CH3 bending),
1000ꢀ1150 (SiꢀOꢀSi asymmetric stretching), 573 (FeꢀO stretching). Fe3O4@SiO2/βꢀ
lactam (3c): 3400 (OꢀH), 2854ꢀ3076 (CꢀH stretching), 1745 (C=O amide, stretching),
1694 (C=O ester, stretching), 1480ꢀ1600 (C=C aromatic ring), 1462 (CH2 bending),
1373 (CH3 bending), 1000ꢀ1150 (SiꢀOꢀSi asymmetric stretching), 570 (FeꢀO
stretching). Fe3O4@SiO2/βꢀlactam (3d): 3400 (OꢀH), 2857ꢀ3069 (CꢀH stretching),
1748 (C=O amide, stretching), 1698 (C=O ester, stretching), 1480ꢀ1600 (C=C
aromatic ring), 1476 (CH2 bending), 1369 (CH3 bending), 1000ꢀ1150 (SiꢀOꢀSi
asymmetric stretching), 571 (FeꢀO stretching). Fe3O4@SiO2/βꢀlactam (3e): 3400 (Oꢀ
H), 2862ꢀ 3085 (CꢀH stretching), 1690ꢀ1750 (overlap 2C=O amide and ester,
stretching), 1480ꢀ1600 (C=C aromatic ring), 1472 (CH2 bending), 1392 (CH3
bending), 1000ꢀ1150 (SiꢀOꢀSi asymmetric stretching), 570 (FeꢀO stretching).
Fe3O4@SiO2/βꢀlactam (3f): 3400 (OꢀH), 2870ꢀ 3072 (CꢀH stretching), 1690ꢀ1750
(overlap 2C=O amide and ester, stretching), 1480ꢀ1600 (C=C aromatic ring), 1458
(CH2 bending), 1388 (CH3 bending), 1000ꢀ1150 (SiꢀOꢀSi asymmetric stretching), 570
(FeꢀO stretching).
4.2.7. Determination of minimum inhibitory concentrations (MICs)
Gramꢀpositive S. aureus (ATCC 25923) and gramꢀnegative Escherichia coli (ATCC
25922) bacterial strain were used as test bacteria. Cultures were grown in 10 mL of
Brain Heart Infusion solution and incubated for overnight at 37 °C and shaking at 100
rpm. These cultures were washed and diluted to a final concentration of 5 × 105
bacteria/mL in Brain Heart Infusion solution containing various concentrations of free
of βꢀlactam (2a-f) or Fe3O4@SiO2/βꢀlactam (3a-f) (ranging from 0 to 100 ꢁ g/mL).
Bacterial densities were estimated by diluting method after incubation at 37 °C and
shaking at 200 rpm for 24 h, then plating bacterial on Brain Heart Infusion agar
followed by incubation overnight at 37 °C. The MIC was determinate as the last
dilution of the tested samples which inhibited the microbial growth.
Spectral data
Schiff base 4-(((4-methoxyphenyl)imino)methyl)phenol (1a)
1
Gray solid, mp 200ꢀ203 °C; H NMR (250 MHz, DMSOꢀd6): δ= 3.79 (s, 3H, OMe), 6.85ꢀ
6.91 (m, 4H, ArꢀH), 7.17 (d, J= 8.00 Hz, 2H, ArꢀH), 7.72 (d, J= 8.00 Hz, 2H, ArꢀH), 8.38 (s,
1H, CH=N), 9.75 (s, 1H, OH); 13C NMR (62.9 MHz, DMSOꢀd6): δ= 60.2 (OMe), 119.1,
120.5, 126.8, 132.7, 135.1, 149.9, 160.0, 162.6, 165.3 (C=N); IR (Neat, Cmꢀ1): 1027, 1243
(sp2CꢀOꢀCsp3), 1390 (CH3 bending), 1480ꢀ1600 (C=C aromatic ring), 1638 (C=N stretching),
2844ꢀ3075 (CH stretching); Analysis calculated for C14H13NO2: C, 73.99; H, 5.77; N, 6.16%.
Found: C, 73.71; H, 5.51; N, 5.65%.
4-(1-(4-Methoxyphenyl)-2-oxospiro[azetidine-3,9'-xanthen]-4-yl)phenyl acrylate (2a)
Yellow oil, 1H NMR (250 MHz, CDCl3): δ= 3.80 (s, 3H, OMe), 5.08 (d, J= 4.75 Hz, 1H, Hꢀ
3), 5.93ꢀ5.98 (m, 1H, acrylat), 6.21ꢀ6.25 (m, 1H, acrylat), 6.49ꢀ6.52 (m, 1H, acrylat), 6.84–
13
7.50 (m, 16H, ArꢀH); C NMR (62.9 MHz, CDCl3): δ= 55.5 (OMe), 63.9 (Cꢀ4), 73.8 (Cꢀ3),
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114.5, 116.2, 116.9, 119.0, 121.3, 122.7, 124.3, 127.6, 128.4, 129.1, 131.3, 132.2, 132.8,
149.9, 152.0, 156.6, 164.2 (CO acrylat), 165.6 (CO βꢀlactam). MS m/z = 489 [M+]. IR (Neat,
cmꢀ1): 1384 (CH3 bending), 1480ꢀ1600 (C=C aromatic ring), 1607 (ꢀCH=CH2 acrylat), 1689
(C=O acrylat), 1751 (C=O βꢀlactam), 2839ꢀ3082 (CH stretching). Analysis calculated for
C31H23NO5: C, 76.06; H, 4.74; N, 2.86%. Found: C, 76.51; H, 4.93; N, 2.93%.
4-(3-Methoxy-1-(4-methoxyphenyl)-4-oxoazetidin-2-yl) phenyl acrylate (2b)
1
Yellow oil, H NMR (250 MHz, CDCl3): δ= 3.73 (s, 3H, OMe), 3.77 (s, 3H, OMe), 4.80 (d,
J= 4.70 Hz, 1H, Hꢀ4,), 5.19 (d, J= 4.70 Hz, 1H, Hꢀ3), 5.69ꢀ5.73 (m, 1H, acrylat,), 6.00ꢀ6.05
(m, 1H, acrylat), 6.56ꢀ6.64 (m, 1H, acrylat), 6.76–7.51 (m, 8H, ArꢀH,); 13C NMR (62.9 MHz,
CDCl3): δ= 55.4, 58.4 (OMe), 61.3 (Cꢀ4), 84.7 (Cꢀ3), 114.1, 114.4, 116.1, 118.8, 122.0,
127.4, 129.0, 131.1, 132.3, 132.9, 156.4, 163.0 (CO acrylat), 163.8 (CO βꢀlactam); MS m/z=
353.2 [M+]; IR (Neat, Cmꢀ1): 1387 (CH3 bending), 1480ꢀ1600 (C=C aromatic ring), 1608 (ꢀ
CH=CH2 acrylat), 1680 (C=O acrylat), 1749 (C=O βꢀlactam), 2839ꢀ3071 (CH stretching);
Analysis calculated for C20H19NO5: C, 67.98; H, 5.42; N, 3.96%. Found: C, 68.21; H, 5.53;
N, 4.03%.
4-(1-(4-Methoxyphenyl)-4-oxo-3-phenoxyazetidin-2-yl) phenyl acrylate (2c)
White solid, mp 155ꢀ157 °C; 1H NMR (250 MHz, CDCl3): δ= 3.74 (s, 3H, OMe), 5.36 (d, J=
4.70 Hz, 1H, Hꢀ4), 5.55 (d, J= 4.70 Hz, 1H, Hꢀ3), 5.96ꢀ6.01 (m, 1H, acrylat), 6.21ꢀ6.32 (m,
1H, acrylat), 6.53ꢀ6.60 (m, 1H, acrylat), 6.79ꢀ7.39 (m, 13H, ArꢀH); 13C NMR (63 MHz,
CDCl3): δ= 55.4 (OMe), 61.4 (Cꢀ4), 81.1 (Cꢀ3), 114.4, 115.7, 118.9, 121.5, 122.2, 127.7,
129.1, 129.3, 129.5, 130.2, 132.7, 150.8, 156.5, 156.8, 162.3 (CO acrylat), 164.1 (CO βꢀ
lactam); MS m/z= 415.1 [M+]; IR (Neat, Cmꢀ1): 1381 (CH3 bending), 1480ꢀ1600 (C=C
aromatic ring), 1612 (ꢀCH=CH2 acrylat), 1682 (C=O acrylat), 1762 (C=O βꢀlactam), 2843ꢀ
3078 (CH stretching); Analysis calculated for C25H21NO5: C, 72.28; H, 5.10; N, 3.37; %.
Found: C, C, 71.98; H, 4.03; N, 3.21; %.
4-(3-(4-Chlorophenoxy)-1-(4-methoxyphenyl)-4-oxoazetidin-2-yl)phenyl acrylate (2d)
1
Light yellow oil, H NMR (250 MHz, CDCl3): δ= 3.74 (s, 3H, OMe), 5.36 (d, J= 4.75 Hz,
1H, Hꢀ4), 5.50 (d, J= 4.75 Hz, 1H, Hꢀ3), 6.02ꢀ6.03 (m, 1H, acrylat), 6.23ꢀ6.34 (m, 1H,
acrylat), 6.55ꢀ6.62 (m, 1H, acrylat), 6.70ꢀ6.82 (m, 4H, ArꢀH), 7.08ꢀ7.14 (m, 4H, ArꢀH), 7.26ꢀ
7.39 (m, 4H, ArꢀH); 13C NMR (62.9 MHz, CDCl3): δ= 55.4 (OMe), 61.3 (Cꢀ4), 81.3 (Cꢀ3),
114.4, 115.9, 117.0, 118.9, 121.6, 127.7, 129.1, 129.2, 129.4, 130.0, 132.9, 150.9, 155.4,
156.6, 162.0 (CO acrylat), 164.2 (CO βꢀlactam); MS m/z= 449 [M+]; IR (Neat, Cmꢀ1): 1393
(CH3 bending), 1480ꢀ1600 (C=C aromatic ring), 1628 (ꢀCH=CH2 acrylat), 1681 (C=O
acrylat), 1736 (C=O βꢀlactam), 2869ꢀ3078 (CH stretching); Analysis calculated for
C25H20ClNO5: C, 66.74; H, 4.48; N, 3.11%. Found: C, 66.25; H, 4.39; N, 3.08%.
4-(3-(2,4-Dichlorophenoxy)-1-(4-methoxyphenyl)-4-oxoazetidin-2-yl)phenyl acrylate (2e)
1
Light yellow oil, H NMR (250 MHz, CDCl3): δ= 3.74 (s, 3H, OMe), 5.40 (d, J= 4.70 Hz,
1H, Hꢀ4), 5.50 (d J= 4.70 Hz, 1H, Hꢀ3), 5.98ꢀ6.18 (m, 1H, acrylat), 6.30ꢀ6.35 (m, 1H,
acrylat), 6.55ꢀ6.62 (m, 1H, acrylat), 6.92ꢀ7.34 (m, 11H, ArꢀH); 13C NMR (62.9 MHz,
CDCl3): δ= 55.4 (OMe), 60.9 (Cꢀ4), 81.6 (Cꢀ3), 114.5, 116.0, 118.9, 121.7, 122.3, 124.2,
127.4, 127.7, 129.1, 130.0, 131.2, 132.3, 132.9, 151.0, 151.4, 156.7, 161.7 (CO acrylat),
162.7 (CO βꢀlactam); MS m/z= 483.3 [M+]; IR (Neat, Cmꢀ1): 1389 (CH3 bending), 1480ꢀ1600
(C=C aromatic ring), 1612 (ꢀCH=CH2 acrylat), 1681 (C=O acrylat), 1751 (C=O βꢀlactam),
2885ꢀ3086 (CH stretching); Analysis calculated for C25H19Cl2NO5: C, 62.00; H, 3.95; N,
2.89%. Found: C, 62.11; H, 4.02; N, 2.95%.
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4-(1-(4-Methoxyphenyl)-3-(naphthalen-2-yloxy)-4-oxoazetidin-2-yl)phenyl acrylate (2f)
Brown oil, 1H NMR (250 MHz, CDCl3): δ= 3.72 (s, 3H, OMe), 5.39 (d, J= 4.65 Hz, 1H, Hꢀ
4), 5.65 (d, J= 4.70 Hz, 1H, Hꢀ3), 5.94ꢀ5.98 (m, 1H, acrylat), 6.23ꢀ6.33 (m, 1H, acrylat),
6.51ꢀ6.81 (m, 1H, acrylat), 6.90ꢀ7.75 (m, 15H, ArꢀH); 13C NMR (62.9 MHz, CDCl3): δ= 55.4
(OMe), 61.5 (Cꢀ4), 81.0 (Cꢀ3), 109.2, 114.0, 114.4, 116.0, 118.3, 118.9, 121.5, 121.9, 124.2,
126.4, 126.8, 127.6, 129.1, 129.5, 130.1, 131.0, 132.2, 132.8, 133.8, 156.6, 162.4 (CO
acrylat), 163.8 (CO βꢀlactam); MS m/z= 465 [M+]; IR (Neat, Cmꢀ1): 1389 (CH3 bending),
1480ꢀ1600 (C=C aromatic ring), 1605 (ꢀCH=CH2 acrylat), 1682 (C=O acrylat), 1751 (C=O βꢀ
lactam), 2831ꢀ3070 (CH stretching); Analysis calculated for C29H23NO5: C, 74.83; H, 4.98;
N, 3.01%. Found: C, 74.97; H, 5.11; N, 3.13%.
Acknowledgements
Authors are grateful to the research council of Shiraz University and Iran National
Science Foundation for their financial support to undertake this work.
References
1 K.A. Jolliffe, Inhibitors of fungal phospholipase B: novel antifungal agents. Congdes of drug
design. Amongst The Vines, Hunter Valley, NSW, Australia, 2006.
2 A. Jarrahpour, J. Sheikh, I. El Mounsi, H. Juneja and T.B. Hadda, Med. Chem. Res., 2013, 22,
1203-1211.
3 A. FernandezꢀGonzalez, R. Badıa and M.E. DiazꢀGarcıa, Anal. Biochem., 2005, 341, 113ꢀ121.
4 R. Southgate, Contemp. Org.Synth., 1994, 1, 417ꢀ431.
5 T.E. Long and E. Turos, Curr. Med. Chem. AntiꢀInfect. Agents., 2002, 1, 251ꢀ268.
6 B. Alcaide, P. Almendros, G. Cabrero and M.P. Ruiza, Synthesis., 2008, 17, 2835ꢀ2839.
7 E. Leemans, M. D’hooghe, Y. Dejaegher, K.W. Tornroos and N. De Kimpe, J. Org.Chem., 2008,
73, 1422ꢀ1428.
8 R.K. Mishra, C.M. Coates, K.D. Revell and E. Turos, Org. Lett., 2007, 9, 575ꢀ578.
9 L.R. Domingo, M.J. Aurell and M. Arno, Tetrahedron., 2009, 65, 3432ꢀ3440.
10 A.K. Halve, D. Bhadauria and R. Dubey, Bioorg. Med. Chem. Lett., 2007, 17, 341ꢀ345.
11 A. Jarrahpour, E. Ebrahimi, R. Khalifeh, H. Sharghi, M. Sahraei, V. Sinou, C. Latour and J.M.
Brunel, Tetrahedron., 2012, 68, 4740ꢀ4744.
12 T. Sperka, J. Pitlik, P. Bagossi and J. Tozser, Bioorg. Med. Chem. Lett., 2005, 15, 3086ꢀ3090.
13 A. Jarrahpour, E. Ebrahimi, E. De Clercq, V. Sinou, C. Latour, L. Djouhri Bouktab and J.M.
Brunel, Tetrahedron., 2011, 67, 8699ꢀ8704.
14 G. Veinberg, I. Shestakova, M. Verma, I. Kenepe and E. Lukevics, Bioorg. Med. Chem.
Lett., 2004, 14, 147ꢀ150.
15 R.K. Goel, M.P. Mahajan and S.K. Kulkarni, J. Pharm. Pharm. Sci., 2004, 7, 80ꢀ83.
16 C. Saturnino, B. Fusco, P. Saturnino, G. De Martino, F. Rocco and J.C. Lanceolat, Biol.
Pharm. Bull., 2000, 23, 654ꢀ656.
17 S.B. Rosenblum, T. Huynh, A. Afonso, H.R. Davis, N. Yumibe, J.W. Clader and D.A. Burnett,
J. Med. Chem., 1998, 41, 973ꢀ980.
18 W.T. Han, A.K. Trehan, J.J.K. Wright, M.E. Federici, S.M. Seiler and N.A. Meanwell, Bioorg.
Med. Chem., 1995, 3, 1123ꢀ1143.
19 M.I. Konaklieva, Curr. Med. Chem. AntiꢀInfective. Agents., 2002, 1, 215ꢀ238.
20 A.D. Borthwick, G. Weingarte, T.M. Haley, M. Tomaszewski, W. Wang, Z. Hu, J. Bedard,
H. Jin, L.Yuen and T.S. Mansour, Bioorg. Med. Chem. Lett., 1998, 8, 365ꢀ370.
21 J. MarchandꢀBrynaert, M. Laurent and M. Ceresiat, J. Org. Chem., 2004, 69, 3194ꢀ3197.
22 M.A. Bonache, G. GeronaꢀNavarro, C. GarciaꢀAparicio, M. Alias, M. MartinꢀMartinez, M.T.
17

RSC Advances
Page 18 of 20
View Article Online
DOI: 10.1039/C6RA03634A
Garciaꢀ Lopez, P. Lopez, C. Cativiela and R. GonzalezꢀMuniz, Tetrahedron Asymmetry. 2003,
14, 2161ꢀ2169.
23 X. Zhang, R.P. Hsung, H. Li, Y. Zhang, W.L. Johnson and R. Figueroa, Org. Lett., 2008, 10,
3477ꢀ3479.
24 E. Bandini and G. Favi, Org. Lett., 2000, 2, 1077ꢀ1079.
25 S. Hata, T. Iwasawa, M. Iguchi, K. Yamada and K. Tomioka, Synthesis., 2004, 9, 1471ꢀ1475.
26 H. Staudinger, Liebigs Ann. Chem., 1907, 356, 51ꢀ123.
27 F.H. Van der Steen and G. Van Koten, Tetrahedron., 1991, 47, 7503ꢀ7524.
28 A. Jarrahpour and P. Alvand, Iran. J. Sci. Tech. Trans. A., 2007, 31, 17ꢀ22.
29 G.I. Georg, The Organic Chemistry of βꢀLactams, VCH: New York, 1993.
30 A. Jarrahpour and M. Zarei, Tetrahedron., 2009, 65, 2927ꢀ2934.
31 A.K. Bose, J.C. Kapur, S.D. Sharma and M.S. Manhas, Tetrahedron Lett., 1973, 14, 2319ꢀ2320.
32 A.R.A.S. Deshmukh, D. Krishnaswamy, V.V. Govande, B.M. Bhawal and V.K. Gumaste,
Tetrahedron., 2002, 58, 2215ꢀ2225.
33 M.S. Manhas, A.K. Bose and M.S. Khajavi, Synthesis., 1981, 46, 209ꢀ210.
34 M. Nahmany and A. Melman, J. Org. Chem., 2006, 71, 5804ꢀ5806.
35 A. Bhalla, P. Venugopalany and S.S. Bari, Tetrahedron., 2006, 62, 8291ꢀ8302.
36 P.D. Croce and C. La Rosa, Tetrahedron Asymmetry., 1999, 10, 1193ꢀ1199.
37 S. Matsui, Y. Hashimoto and K. Saigo, Synthesis., 1998, 8, 1161ꢀ1166.
38 E. Ebrahimi and A. Jarrahpour, Iran. J. Sci. Technol. A., 2014, 38, 49ꢀ53.
39 S. Shen, J.X. Xia and J. Wang, Biomaterials., 2016, 74, 1ꢀ18.
40 P. Pengo and L. Pasquato, J. Fluorine. Chem., 2015, 117, 2ꢀ10.
41 E. Reimhult, New. Biotechnol., 2015, 32, 665ꢀ672.
42 J.B. BlancoꢀCanosa, M. Wu, K. Susumu, E. Petryayeva, , T.L. Jennings, P.E. Dawson, W.R.
Algar, and I.L. Medintz, Coordin. Chem. Rev., 2014. 263, 101ꢀ137.
43 S.V. Salihov, Y.A. Ivanenkov, S.P. Krechetov, M.S. Veselov, N.V. Sviridenkova, A.G.
Savchenko, N.L. Klyachko, Y.I. Golovin, N.V. Chufarova, E.K. Beloglazkina and A.G. Majouga,
J. Magn. Magn. Mater, 2015, 394, 173ꢀ178.
44 E. Ebrahimi, A. Jarrahpour, N. Heidari, V. Sinou, C. Latour, J.M. Brunel, A.R. Zolghadr and E.
Turos, Med. Chem. Res., 2016. 25, 247ꢀ262.
45 A. Jarrahpour, M.M. Doroodmand and E. Ebrahimi, Tetrahedron Lett., 2012, 53, 2797ꢀ2801.
46 I. Capek, Adv. Colloid. Interface., 2015, 222, 119ꢀ134.
47 A. Dehshahri and H. Sadeghpour, Colloid. Surface. B., 2015, 132, 85ꢀ102.
48 P. Kesharwani, S. Banerjee, U. Gupta, M.C.I.M. Amin, S. Padhye, F.H. Sarkar and A.K. Iyer,
Mater. Today., 2015, 18, 565ꢀ572.
49 L. DouziechꢀEryrolles, H. Marchais and K. Herve, Int. J. Nanomedicine., 2007, 2, 541ꢀ550.
50 G. Reiss and A. Huetten, Nat Mater., 2005, 4, 725ꢀ726.
51 T. Hyeon, Chem Commun., 2003, 8, 927ꢀ934.
52 C.T. Yavuz, J.T. Mayo, W.W. Yu, A. Prakash, J.C. Falkner, S. Yean, L.L. Cong, H.J.
Shipley, A. Kan, M. Tomson, D. Natelson and V.L. Colvin, Science., 2006, 314, 964ꢀ967.
53 J.W.M. Bulte and D.L. Kraitchman. NMR Biomed., 2004, 17, 484ꢀ499.
54 C. Corot, M. Port, I. Guilbert, P. Robert, I. Raynal, C. Robic, J.S. Raynaud, P. Prigent, A.
Dencausse, J. Idee, Superparamagnetic Contrast Agents, In: M.M.J. Modo, W.M. Jeff, J.W.M.
Bulte (Eds.), Molecular and Cellular MR Imaging, CRC Press, Boca Raton, FL, 2007, 60ꢀ78.
55 A.H. Lu, W. Schmidt, N. Matoussevitch, H. Bönnemann, B. Spliethoff, B. Tesche, E. Bill,
W.Kiefer and F. Schüth, Angew. Chem., 2004, 116, 4403ꢀ4406.
56 A. Ito, H. Honda and T. Kobayashi, Cancer. Immunol. Immun. 2006, 55, 320ꢀ328.
57 B. Thiesen and A. Jordan, Int. J. Hyperthermia., 2008, 24, 467ꢀ474.
58 J. Javidi and M. Esmaeilpour, Colloid. Surface B., 2013, 102, 265ꢀ272.
59 P. Xue, W.G. Su, Y.H. Gu, H.F. Liu and J.L. Wang, J. Magn. Magn. Mater., 2015, 378, 306ꢀ312.
60 P. Xue, Y. Gu, W. Su, H. Shuai and J. Wang, Appl. Surf. Sci., 2016, 362, 427ꢀ433.
61 U.A. Hasanova, M.A. Ramazanov, A. M. Maharramov, Q.M. Eyvazova, Z.A. Agamaliyev, Y.V.
Parfyonova, S.F. Hajiyeva, F.V. Hajiyeva and S.B. Veliyeva, J. Biomater. Nanobiotechnol.,
2015, 6, 225ꢀ235.
18

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View Article Online
DOI: 10.1039/C6RA03634A
62 A.M. Grumezescu, M.C. Gestal, A.M. Holban, V. Grumezescu, B.S. Vasile, L. Mogoantă, F.
Iordache, C. Bleotu and G.D. Mogoșanu, Molecules., 2014, 19, 5013ꢀ5027.
63 M. Esmaeilpour, J. Javidi, F. Nowroozi Dodeji and M. Mokhtari Abarghoui, J. Mol. Catal. A:
Chem., 2014, 393, 18ꢀ29.
64 J. javidi, M. Esmaeilpour, F. Dehghani and F. Nowroozi Dodeji, RSC Adv., 2015, 5, 26625ꢀ26633.
65 J. Javidi and M. Esmaeilpour, Mater. Res. Bull., 2016, 73, 409ꢀ422.
66 Y.H. Deng, Y. Cai, Z.K. Sun, J. Liu, C. Liu, J. Wei, W. Li, Y. Wang and D.Y. Zhao, J. Am.Chem.
Soc., 2010, 132, 8466ꢀ8473.
67 V. Ahmed, J. Kumar, M. Kumar, M.B. Chauhan, P. Dahiya and N.S. Chauhan, J. Exp. Nanosci.,
2015, 10, 718ꢀ728.
68 M. Zarei, Tetrahedron 2013, 69, 6620ꢀ6626.
69 J. Javidi, M. Esmaeilpour and M. Rajabnia Khansari, RSC Adv., 2015, 5, 73268ꢀ73278.
70 M. Esmaeilpour, J. Javidi and M. Zandi, Mater. Res. Bull., 2014, 55, 78ꢀ87.
71 C. Yang, J. Wu and Y. Hou, Chem. Commun., 2011, 47, 5130.
72 J. Yang, D. Wang, W. Liu, X. Zhang, F. Bian and W. Yu, Green Chem., 2013, 15, 3429ꢀ3437.
73 M. Esmaeilpour, J. Javidi, M. Mokhtari Abarghoui and F. Nowroozi Dodeji, J. Iran. Chem. Soc.,
2014, 11, 499ꢀ510.
74 J. Wang, S. Zheng, Y. Shao, J. Liu, Z. Xu and D. Zhu. J. Colloid. Interf. Sci., 2010, 349, 293ꢀ299.
75 Clinical and Laboratory Standards Institute. Methods for Dilution Antimicrobial Susceptibility
Tests for Bacteria That Grow Aerobically; Approved Standard M7ꢀA7; Clinical and Laboratory
Standards Institute: Wayne, PA, USA, 2006.
76 B. Das, M. Mandal, A. Upadhyay, P. Chattopadhyay and N. Karak, Biomed. Mater., 2013, 8,
035003.
77 J.A. Lemire, J.J. Harrison and R.J. Turner, Nat. Rev. Micro., 2013, 11, 371ꢀ384.
78 M. Esmaeilpour, A.R. Sardarian and J. Javidi, Appl. Catal A: Gen., 2012, 445-446, 359ꢀ367.
79 F. Dehghani, A.R. Sardarian and M. Esmaeilpour, J. Organomet. Chem., 2013, 743, 87ꢀ96.
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Synthesis and characterization of β-lactam functionalized
superparamagnetic Fe3O4@SiO2 nanoparticles as an approach for
improvement of antibacterial activity of β-lactams
Mohsen Esmaeilpour(1), Ali Reza Sardarian(1)∗, AliasgharJarrahpour(1), EdrisEbrahimi(1),
JaberJavidi(2,3)
Preparation of magnetic β-lactam functionalized Fe3O4@SiO2 nanoparticles has a synergic
effect to improve the antibacterial activity.