Cytotoxicity, antibacterial and antifungal activities of ZnO nanoparticles prepared by the Artocarpus gomezianus fruit mediated facile green combustion method

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Original Article

Cytotoxicity, antibacterial and antifungal activities of ZnO

nanoparticles prepared by the Artocarpus gomezianus fruit mediated

facile green combustion method

R. Anitha

a

, K.V. Ramesh

b

, T.N. Ravishankar

c

, K.H. Sudheer Kumar

d

,

T. Ramakrishnappa

d,*

a_{Department of Biochemistry, Bharathiar University, Coimbatore, 641 046, India}
b_{PG Department of Biochemistry, Dayananda Sagar College, Bangalore, 560 078, India}

c_{Department of Chemistry, Global Academy of Technology (GAT), Rajarajeshwarinagar, Off Mysore Road, Ideal Homes Township, Bangalore, 560098,}

Karnataka, India

d_{Department of Chemistry, BMS Institute of Technology and Management, Avalahalli, Doddaballapura Main Road, Yelahanka, Bangalore, 560064, India}

a r t i c l e i n f o

Article history:
Received 27 July 2018
Received in revised form
4 November 2018
Accepted 6 November 2018
Available online 22 November 2018
Keywords:

Green synthesis

ZnO nanoparticles
Anticancer activity
MCF-7

Antibacterial
Antifungal

a b s t r a c t

Spherical nanoparticles of zinc oxide (ZnO NPs) were synthesized by an eco-friendly green combustion
method using citrate containing Artocarpus gomezianus fruit extract as a fuel. The morphology,
com-positions and structure of the product were characterized by Powder X-ray Diffraction (PXRD), Scanning
Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Fourier Transform Infra-red (FTIR),
UVeVisible (UVeVis) and Raman Spectroscopy. Highly uniform spherical zinc oxide NPs were subjected
to cytotoxicity, antifungal and antibacterial activities. PXRD patterns show that the product formed
belongs to a hexagonal wurtzite system. SEM micrographs reveal that the particles are agglomerated. The
TEM images demonstrate that the particles are highly uniform spherical in shape and loosely
agglom-erated. Scherrer's method and WeH plots were used to calculate the average crystallite sizes, yielding 39,
35, 31 and 40, 37, 32 nm for ZnO NPs prepared with 5, 10 and 15 mL of 10% Artocarpus gomezianus fruit
extract, respectively. These results were confirmed by the TEM observations. Breast cancer cell lines
(MCF-7) were subjected to in vitro anticancer activity. MTT assay revealed a good anticancer activity of
ZnO NPs against MCF-7. Zone of the inhibition method shows that the spherical ZnO NPs also exhibit
significant antibacterial activity against staphylococcus aureus and antifungal activity against Aspergillus
niger. The synthesized ZnO NPs canfind plausible biological applications.

© 2018 The Authors. Publishing services by Elsevier B.V. on behalf of Vietnam National University, Hanoi.
This is an open access article under the CC BY license ( />

1. Introduction

Inorganic materials such as metals and metal oxides due to their

stability are more advantageous in many aspects than organic
com-pounds[1]. Among the metal oxides, zinc oxide nanoparticles (ZnO
NPs) have received a special attention as an anticancer, antibacterial
and antifungal material. ZnO NPs exhibit improved properties
compare to bulk materials and these novel properties are attributed
to the changes in specific characteristics such as morphology and size
of the particles[2]. ZnO NPs have a wide range of applications in solar
cells, catalysts, gas sensors, luminescent devices etc.[3]. Nowadays,

ZnO NPs gained also significant attention due to their implications
for cancer therapy[4]. It has been found from studies that ZnO NPs
cause cytotoxicity to many types of cells such as HepG2, MCF-7,
HT29, Caco-2, rat C6, HeLa, THP-1 [5e8]. In addition, ZnO NPs
exhibit antibacterial and antifungal activity. They can decrease the
viability and attachment of microbes on biomedical surfaces[9].

ZnO NPs can be chemically synthesized by different methods such
as, spray pyrolysis, hydrothermal treatment, sol-gel process,
co-precipitation, combustionor sonochemical, etc. [10e12]. Generally
the chemicals used in the synthesis and stabilization are toxic and
lead to by-products which are non eco-friendly and cause danger to
human beings and the environment[13]. The generations of toxic
by-products can be avoided using a green chemistry approach, for
instance, using plants for the synthesis of ZnO NPs. Hence, the green
combustion synthesis is an eco-friendly alternative wet-chemical

* Corresponding author.

E-mail address:(T. Ramakrishnappa).
Peer review under responsibility of Vietnam National University, Hanoi.

Contents lists available atScienceDirect

Journal of Science: Advanced Materials and Devices

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method. This method has proved to be an excellent technique for
preparing several grams due to its low processing temperature, short
processing time, cost effectiveness. It shows good ability to achieve
high purity in making multiphase or single complex oxides[14,15].

The main advantages of synthesis of ZnO NPs via the solution
combustion method towards biological activities are: (i) A larger
surface area with high porosity (as in the case of nanoparticles
fabricate by solution combustion method) ensures an increased
range of probable interaction with bio-organics present on the
viable cell surface[16]. (ii) The considerable antimicrobial activities
of inorganic metal oxide nanoparticles such as ZnO NPs and their
selective toxicity to biological systems suggest their potential
application as antimicrobial agents in therapeutic, diagnostic,
sur-gical devices and in nano-medicine as well[17]. (iii) The advantages
of using ZnO NPs as antimicrobial agents are their greater
effec-tiveness on resistant strains of microbial pathogens, less toxicity
and good heat resistance. In addition, they provide mineral
ele-ments essential to human cells and even small amounts of them
exhibit strong activity. (iv) The solution combustion method is a
very simple, low-cost one, using which highly pure and highly
crystalline size nanoparticles can be obtained.

Many articles have reported on the acute toxicity of ZnO NPs.
However, a citrate containing A. gomezianus fruit mediated spherical
ZnO NPs has not been discussed so far. In this study highly uniform
spherical ZnO NPs were successfully prepared by an eco-friendly
green combustion method using different volumes of citrate
con-taining Artocarpus gomezianus fruit source as a fuel. The as-prepared
ZnO NPs were used to study in detail the anticancer, antibacterial
and antifungal activities.

2. Experimental
2.1. Chemicals

The chemicals used for the synthesis were of analytical grade
and were used without any further purification. Zinc nitrate was
procured from Merck. The glassware used in the laboratory were
cleaned with a fresh solution of HCl/HNO3 (1:3, v/v), washed
thoroughly with double distilled water and dried. Double distilled
water was used for all the experiments.

2.2. Preparation of ZnO NPs

The citrate containing Artocarpus gomezianus fruit source was
collected from Mangalore, Karnataka. The collected fresh, healthy
fruits were washed thoroughly using double distilled water and cut
into small pieces. Then small pieces were dried at room
tempera-ture for 10 days under dust free conditions and subsequently
grinded into afine powder. 10 g of this fine powder were boiled in
100 mL doubled distilled water to prepare a 10% crude solution,
thenfiltered and stored in refrigerator for further usage. In a typical

synthesis, 5 mL of the 10% crude solution was added to 3 g of
Zn(NO3)2.6H2O which is already dissolved in 10 mL of double
distilled water. This reaction mixture was well mixed using a
magnetic stirrer for about 5e10 min and then placed in a preheated
muf_{fle furnace maintained at about 400 ± 10}
C. The reaction
mixture boils froths and thermally dehydrates to form foam. The
whole process was completed in a few min. Similar procedure was
repeated by taking 10 and 15 mL of the 10% crude sample.
2.3. Characterization of ZnO NPs

PXRD data were recorded on the PANalyticalX'Pert Pro X-ray
Diffractometer with the graphite monochromatised Cu-K_a
(1.5418Å) radiation. The surface morphology was observe by SEM

(JOEL JSM 840 A) with gold as contrast enhancing material covered
by the sputtering technique. TEM analysis was carried out using
the Hitachi H-8100 (accelerating voltage up to 200 KV, LaB6
Filament) equipped with EDS (Keney Sigma TM Quasar, USA). The
FTIR studies were performed by using the Perkin Elmer
Spec-trometer with KBr pellets. Raman spectrum was obtained at room
temperature in a back scattering geometry using a 632 nm HeNe
laser with a JobinYvonLabRam HR spectrometer (LABRM-HR). The
UVeVisible absorption spectrum was obtained on the SL 159
ELICO UVeVIS Spectrometer. Flow cytometry measurements were
done by using the BD FACS Calibur Flow Cytometry.

2.4. Anticancer activity by MTT assays

The anticancer activity was checked by the 3 e
(4,5-dimethylthiazol-2-yl) - 2,5 - diphenyltetrazolium bromide (MTT)

assay. The monolayer cell (Mammalian breast cancer _fibroblast
cells) culture was trypsinized and the cell count was adjusted such
that 200

m

L of suspension contained approximately 20,000 cells. To
each well of the 96 wells microtitre plate, 200

m

L of the diluted cell
suspension was added and incubated at 37
C and 5% CO2
atmo-sphere for 24 h. After 24 h 200

m

L of different test concentrations of
test drugs were added on to the partial monolayer. The plate was
then incubated at 37
C and 5% CO2atmosphere for 24 h. Media
containing 10% MTT reagent was then added to each well and the
plate was incubated at 37
C and 5% CO2atmosphere for 3 h. Then
100 mL of solubilization solution DMSO (DIMETHYL SULFOXIDE)
was added and the plate was gently shaken to solubilize the formed
formazan. The absorbance was measured by microplate reader at a
wavelength of 570 nm. After subtracting the background and the
blank, the percentage growth inhibition was calculated and the
concentration of the test drug needed to inhibit the cell growth by
50% (IC50) was generated from the dose-response curve for the cell
line.

The cell viability was expressed as follows:

Cell vialbility¼ Test

Control 100% (1)

2.5. Anticancer activity by apoptosis assay

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2.6. Anticancer activity by CAM method

The anticancer activity has also been checked by the

Chlorio-allantoic Membrane (CAM) assay. Whatmann filter paper bud
containing the compound ZnO NP concentration corresponding to
its respective IC50value was implanted on the chick embryo
chorio-allantoic membrane through a hole cut in to the shell of the egg.
The incubation period may range from 1 to 3 days. Afterwards, time
angiogenesis can be quantified through an image analysis.

2.7. Evaluation of the antibacterial activity

The antimicrobial activity of 15 mL of 10% Artocarpus gomezianus
fruit extract mediated ZnO NPs was examined by the zone of
in-hibition method in Muller Hinton agar (MHA) media against
Gram-Positive Staphylococcus spp.

Agglomeration was prevented by the standard sonication
method, in which particles were dispersed in the media using the
sonicator. The ZnO NPs obtained from 5 mL, 10 mL and 15 mL of 10%
crude samples were dissolved in Di Methyl Sulphoxide (DMSO) to
give a concentration of 10 mg/mL. They were marked as stock, to
carry out the minimum inhibitory concentration for the ZnO NPs.
Working concentrations of 5 mg/mL, 0.5 mg/mL, 0.05 mg/mL and
0.005 mg/mL. 0.5 mL was prepared by the serial dilution of 0.5 mL
of the stock solution.

An autoclaved petriplate wasfilled with Sterile Muller Hinton
agar. 100

m

L of 24 h. The test culture (Staphylococcus aureus) was

spread onto the four well bored media. 100

m

L of different
working concentrations of the sample were loaded to four wells.
The plate was kept at 37
C for the incubation along with a

control concerning DMSO and antibiotic (ampicillin) for a period
of 17 h.. The zone of inhibition was recorded following the
in-cubation period.

2.8. Evaluation of the antifungal activity

The examination of the antifungal activity of 15 mL of 10%
Artocarpus gomezianus fruit extract mediated ZnO NPs was carried
out by the zone of inhibition method in potato dextrose agar (PDA)
media against Aspergillus niger. An autoclaved petriplate wasfilled
with the steriled potato dextrose agar (PDA) media. 100

m

L of spore
suspension (Artocarpus niger) was spread onto the four wells.
100

m

L of different working concentrations of the sample were
loaded to the four wells. The plate was kept for incubation along
with a control concerning DMSO and antifungal (fluconazole) at
room temperature for a period of 96 h. The zone of inhibition was
recorded following the incubation period.

3. Result and discussion
3.1. Crystal structure

Fig. 1shows the PXRD patterns of spherical ZnO NPs prepared by
different volume of citrate containing 10% Artocarpus gomezianus
fruit extract (5e15 mL) as fuel via a green solution combustion
method. The diffraction peaks are shown corresponding to the
hexagonal wurtzite structure of ZnO (JCPDS NO. 36-1451) and
average crystallite size (d) was estimated using the Scherrer's
equation[18].

d¼

_b

k

l

cos

q

(2)

The shift of peaks and the widening of lines in PXRD profile arise
due to the micro strain in the nanoparticles. The Williamson and
Hall (WeH) graphs (not shown here) were used to calculate the
micro strain in ZnO NPs using the relation[19].

b

hklcos

q

hklẳ
k

l

Dỵ 4 sin

q

hkl (3)

whereε is the strain associated with the NPs. Equation(3)
repre-sents a straight line between

b

cos

q

(Y-axis) and 4sin

q

(X-axis). The
slope of the line of the W-H graphsl gives the strain (ε) and
inter-cept (0.9

l

/D) of this line on the Y-axis gives the average crystallite
size (D) for the 5, 10 and 15 mL of 10% A. gomezianus fruit extract
mediated ZnO NPs. The obtained mean crystallite size from
Scherrer's method and WeH graphs are tabulated inTable 1. As the
volume of the citrate containing 10% Artocarpus gomezianus fruit
extract increases, the broadening of the lines also increases,
indi-cating that the particle sizes decreases and it is in good agreement
with TEM results.

Fig. 1. PXRD patterns of ZnO NPs prepared with (a) 5, (b) 10 and (c) 15 mL of 10%
A. gomezianus fruit extract.

Table 1

Average crystallite size and strain of ZnO NPs synthesized by 5, 10 and 15 mL of Artocarpus gomezianus fruit extract.

Fruit extract (mL) Average crystallite size (nm) Strain (104)

Scherrer's method (d) WeH plots method (D)

5 39 40 2.42

10 35 37 3.17

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3.2. Morphological studies

Fig. 2shows the SEM micrographs and the EDS of the ZnO
nanoparticles prepared using 5, 10 and 15 mL of citrate containing
Artocarpus gomezianus fruit extract as a fuel. The combustion
product is more influenced by the type of the fuel used. The nature
of the combustion differs from flaming to non-flaming type.
Generally,flaming reaction is associated with the release of large
quantity of gases. The SEM micrographs (Fig. 2(a), (c) and (e)) show
the agglomeration, voids and pores. The pores and voids can be due
to the huge quantity of gases escaping out of the reaction mixture
during the combustion (flaming).

The energy dispersive spectrometry (EDS) analysis was used to
determine the composition of ZnO NPs prepared using 5, 10 and
15 mL of citrate containing Artocarpus gomezianus fruit extract as a
fuel and results are shown inFig. 2(b), (d) and (f), respectively. The
EDS measurements revealed the presence of Zn and O peaks for
ZnO.

Fig. 3shows the TEM image of the ZnO NPs prepared using 5, 10
and 15 mL of citrate containing Artocarpus gomezianus fruit extract
as a fuel. It clearly shows that the nanoparticles are of sizes in the
range 10e30 nm and spherical in shape of rather uniform
dimension.

3.3. FTIR analysis

FTIR spectra of ZnO NPs prepared using 5, 10 and 15 mL of citrate
containing Artocarpus gomezianus fruit extract are shown inFig. 4

(a-c). The absorption band near 3450 cm1is due to the hydroxyl
group of H2O adsorbed on the ZnO NPs. The transmittance band

between 1400 and 1649 cm1is due to the stretching mode of C]
O. The peak at 2350 cm1arises due to CO2absorption from the
atmosphere on the metallic cations. The bands at 421 and 590 cm1
correspond to the bonding between ZneO[20].

3.4. UVeVis analysis

Fig. 5shows the UVeVis spectrum of the ZnO NPs prepared at
room temperature using 15 mL of citrate containing A. gomezianus
fruit extract as a fuel. At the wavelength of 367 nm, the
charac-teristic absorption peak in the ZnO NPs spectrum is observed. Due
to the electron transitions from the valence band to the conduction
band (O2p-Zn3d), the characteristic absorption peak of the ZnO NPs
can be assigned[21]. From this absorption spectrum, using Tauc
equation, the band-gap of the ZnO thinfilm was calculated[22]:

a

hv ¼ A hv  Eg

n

(4)

where

a

h

n

is the photon energy, Egis the band gap, n¼ 1/2 for the
direct band gap transition and A is a constant which is different for
different transitions. The progress information gives the best linear
fit in the band edge location for n ¼ 1/2. The band gap was observed
as 3.39 eV which is somewhat more prominent than that of the
massive ZnO (~3.37 eV). This band gap upgrade emerges because of
the size impact of the nanoparticles.

3.5. Raman analysis

Raman spectroscopy can give information on the vibrational
properties of the ZnO NPs.Fig. 6shows the Raman spectrum of the

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sample in the range of wavelengths between 200 and 800 cm1.
The peak at 436 cm1relates to E2 (high), which is moved by
3 cm1. The peak at 582 cm1is set between E1(LO) and A1(LO),
which is a great concurrence with the literature data[23]. The peak
at 330 cm1is because of the second-order Raman scattering. The
peak at 379 cm1relates to A1(TO) and that at 410 cm1compared
to E1(TO) vibrational modes of ZnO nanocrystals[24].

3.6. Product formation mechanism

Zn(NO3)2.6H2O and the aqueous 10% A. gomezianus fruit extract
as a fuel were mixed in distilled water. When this mixture was

Fig. 4. FTIR spectra of ZnO NPs prepared by (a) 5, (b) 10 and (c) 15 mL of 10% A.
gomezianus fruit extract.

Fig. 3. TEM images of ZnO NPs prepared by (a) 5, (b) 10 and (c) 15 mL of 10% A. gomezianus fruit extract.

Fig. 5. UVeVis spectrum of ZnO NPs prepared by 15 mL of 10% Artocarpus gomezianus
fruit extract.

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heated to 400± 10
_{C, in the beginning the wet powder undergoes}
the thermal dehydration. Then it undergoes the decomposition of
Zn(NO3)2.6H2O and of the fuel. Then it breaks down into aflame,
yielding porous, agglomerated powders. The reaction was
self-propagating and the heat released was sustained for a length of
few seconds. The probable formation mechanism of ZnO NPs is as
the following

Zn(NO3)2.6H2Oỵ fruit extract / ZnO nanoparticles ỵ Gaseous
products

Phytochemicals present in the aqueous fruit extracts react with
the Zn ions. Fruit extracts act as reducing and stabilizing agents.
3.7. Anticancer activity

In vitro experiments can be easy and rapid to perform and can
provide a range from 10 to 500

m

g/mL of the in vivo toxicity. The
cytotoxicity results of in vitro experiments were taken after 24 h
of the incubation with different concentrations of ZnO NPs
ranging from 10 to 500

m

g/mL, prepared with 15 mL of 10%
A. gomezianus fruit extract and are shown inFig. 7. Cells at different

concentrations of ZnO NPs show different stages of cell
death/ne-crosis[25]. The drug of nano ZnO shows necrosis of the MCF-7 cells
at 100

m

M indicating its toxicity is approximately near to the
standard drug camptothecin whose toxicity level is 50

m

M[26]. The
cytotoxic effect of ZnO NPs in MCF-7 cell lines is presented inFig. 8.
The results obtained infers an inverse relation between the drug
concentration and the cell viability. The percentage growth
inhi-bition was found by subtracting the background and blank. The
concentration of the nano ZnO drug required to inhibit cell growth
by 50% (IC50) was got from the dose-response curve. So we have got
the inference of IC50with the value of 9.3495

m

g/mL.

Fig. 9(a) and (b) show theflow cytometry data of SSC-H versus
FSC-H, untreated and treated with ZnO NPs prepared with 15 mL of
10% Artocarpus gomezianus fruit extract. It is clear that the SSC
in-tensity is an indicator for the uptake of the ZnO NPs.Fig. 10shows a
graph of theflow cytometry analysis of MCF-7 cells with Annex
in-V Fluorescein isothiocyanate (FITC) of which graph, in the lower left
corner are the living cells. From the graph, it is clear that all the cells
undergo an apoptotic pathway as indicated by the presence of the
small amounts of cells in each plot. And in the FITC count graph of
log counts we can observe that there is a sharp peak obtained
indicating the path taken by cell during apoptotic pathway which is
expelled by the color offluorochrome FITC linked to the cell.Fig. 11

shows the graphical representation of counts versus FITC Annex
in-V for ZnO NPs.

Fig. 12shows the CAM assay involving the implantation of the
experimental drug on the blood vessels of a chick embryo. This

allows nanoparticles to observe the thinning/disappearance of
blood vessels which can be related to the destruction of tumors
(cancerous tumors) via the disruption of the blood vessel
devel-opment or inhibiting the formation of new blood vessels inside the
tumor, thereby inhibiting the further spread of cancer. This is
another proof of the anti-cancer properties of the ZnO
nanoparticles.

3.8. Antibacterial and antifungal assay

Figs. 13 and 14show the photographs illustrating the
antibac-terial and antifungal activities of the ZnO NPs prepared with 15 mL
of 10% A. gomezianus fruit extract using the zone of inhibition
method against Staphylococcus aureus and Artocarpus niger,
respectively. The zone of inhibition was observed against the ZnO
NPs and results are summarized inTable 2. The results indicate that

5, 10 and 15 mL fruit extract mediated ZnO NPs at 0.5 mg/100

m

L
exhibited rather similar antibacterial and antifungal ef_ficacy
against Gram-Positive Staphylococcus aureus and Aspergillus niger,
respectively. Nanoparticles provide relatively larger active surface
area and thus, a higher amount of those Zn atoms that trigger a
toxicity effect of ZnO towards the bacteria [27]. The detailed

Fig. 8. Cell viability of MCF-7 cells calculated by MTT assay. Cells were incubated for
24 h with the ZnO NPs prepared with 15 mL of 10% A. gomezianus fruit extract.

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reaction system of the bioactivity of ZnO is still under debate.
Numerous systems have been proposed and are identified with the
features, such as: (i) One of the conceivable mechanism depending

on the grating surface of ZnO, actually the ZnO NPs to the bacterial
surface is due to the electrostatic powers that straightforwardly
eliminate microorganisms [28], (ii) The entering ZnO NPs can
connect with the layer lipids and casues the pulverization of the cell
membrane, which prompts the lost of the membrane uprightness
and breakdown, and lastly leads to the bacterial demise[29], (iii)
The arrival of the Zn2ỵparticles from the ZnO nanoparticles and (iv)
The generation of the very responsive species of, for example,

O22, H2O2, OHwhich harm the DNA, cellfilms or cell proteins, and
may at long last prompt the hindrance of the bacterial development
and in the end leading to the bacterial death.

3.9. Mechanism of antibacterial and antifungal activities

Although the exact mechanism of antibacterial and antifungal
activities of ZnO nanoparticles is still unknown, the antimicrobial
activity of these nanoparticles was attributed to several
mecha-nisms, including the release of antimicrobial ions [30], the
interaction of nanoparticles with microorganisms followed
subse-quently by damaging the integrity of the bacterial cells[31]and the
formation of reactive oxygen species (ROS) by the effect of the light
radiation[32]. The release of the Zn2ỵantimicrobial ions has been
suggested as a reasonable hypothesis about the toxicity of ZnO
against S. cerevisiae[33]. According to this author, the toxicity of
ZnO nanoparticles could result from the solubility of the Zn2ỵions
in the medium containing the microorganisms. However, the
sol-ubility of the metal oxides, such as ZnO is a function of their
con-centration and the time [33]. Thus, low concentrations of
solubilized Zn2ỵions can trigger a relatively high tolerance by the

microorganism. In the case of yeast, labile Zn2ỵions rapidly
accu-mulates in dynamic vesicular compartments (vacuoles and
zinco-somes), which are an important cellular defense system to buffer
both the zinc excess and deficiency[34].

In addition, there are differences in the metabolic processes of
the Zn2ỵions, which depend on characteristics intrinsic to each
microorganism. This could be one of the possible reasons for the
observed differences in toxicity thresholds of ZnO nanoparticles
in various microorganisms. In this way, Reddy et al.[35]studied
the toxicity of ZnO nanoparticles on E. coli and S. aureus. The
results showed complete inhibition of E. coli growth at
concen-trations3.4 mM, while the growth of S. aureus was completely
inhibited at concentrations 1 mM. Moreover, Reddy et al.
observed that cells of E. coli treated with 1 mM of ZnO showed a
consistent increase in the number of colony forming units
(CFU) compared to control, due to the preference of this
micro-organism for low concentrations of Zn2ỵ in the growth
me-dium. Conversely, S. aureus showed an efflux mechanism of Zn2ỵ
during the exposure to ZnO nanoparticles in the millimolar
range, indicating that the sufficient ion concentration results in
undesirable and potentially toxic conditions to this
microor-ganism. Thus, concerning the effect of ZnO against E. coli at low
concentrations, rather than exercising antimicrobial activities,
the ZnO nanoparticles may actually increase the bacterial growth.
Zhang et al.[31]studied the effect of ZnO NPs on E. coli cells, and

Fig. 12. (a) Implantation of the drug ZnO 100mM (IC50 value) and (b) Thinning of blood vessels seen preceding the site of the drug implant.
Fig. 10. Graph of Flow cytometry analysis of MCF-7 cells with Annex in-V Fluorescein

isothiocyanate (FITC) of which graph in the lower left area are the living cells.

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as a result they pointed out that the interaction between the ZnO
nanoparticles and the E. coli cells is caused by electrostatic forces.
According to Stoimenov et al.[28], the global charge of bacterial
cells at biological pH values is negative, due to the excess of
carboxylic groups, which are dissociated and provide a negative
charge to the cell surface Conversely, ZnO nanoparticles have a
positive charge, with a zeta potential of ỵ24 mV, [31]). As a
result, opposite charges between the bacteria and the ZnO
ano-particles generate electrostatic forces, leading to a strong binding
between the nanoparticles and the bacteria surface and,
conse-quently, producing the cell membrane damage. The possible
mechanism of the antimicrobial activity of the ZnO nanoparticles
is still unknown. However, is it could be possibly suggested in a
schema, which is shown inFig. 15.

4. Conclusion

We successfully synthesized the spherical ZnO NPs by the
green combustion strategy utilizing the 5, 10 and 15 mL, 10%
cit-rate containing A. gomezianus solution arrangement as a fuel.
PXRD studies revealed that the pure hexagonal wurtzite structure
was obtained. The average crystallite size of the NPs was evaluated
from Scherrer's and WeH plots and observed to be in the range of
~35 nm and the outcomes were additionally affirmed by the TEM
experiments. The SEM micrographs showed that all the samples
are of agglomeration, pores and voids due to theflaming in the
green combustion synthesis. The TEM analysis makes it apparent

that, 15 mL, 10% citrate containing A. gomezianus fruit extract
mediated ZnO NPs are desirable in shape and size. FTIR and Raman
spectra affirmed the formation of ZnO. The optical band gap of the
ZnO nanoparticles was acquired to be 3.39 eV. The as-synthesized
ZnO NPs are found to be potentially usable as an alternative
anti-cancer drug other than the standard camptothecin one. The
cytotoxicity results of the in vitro experiments were obtained after
24 h of the incubation with different concentrations of the ZnO
NPs prepared with 15 mL of 10% Artocarpus gomezianus fruit
extract, ranging from 10 to 500

m

g/mL showing that different
concentrations of ZnO NPs caused different stages of the cell
death/necrosis. The nano sized ZnO drug showed necrosis of the
MCF-7 cells at 100

m

M indicating its toxicity to be approximately
near to the standard drug camptothecin whose toxicity level is
50

m

M. The percentage growth inhibition was found by
subtract-ing the background and the blank data. The concentration of the
nanosized ZnO drug required to inhibit cell growth was found
from the dose-response curve to be at 50% (IC50) and the
infer-ence of IC50 value¼ 9.3495

m

g/mL. Furthermore, our study has
shown that the ZnO NPs exhibit significant antibacterial and
antifungal activities and, thus, can be useful for biological
appli-cations. The antibacterial and antifungal activities of the ZnO NPs
prepared with 15 mL of 10% A. gomezianus fruit extract were
evaluated by the zone of inhibition method against Staphylococcus
aureus and A. niger, respectively. The zone of inhibition was
observed against the ZnO NPs and is summarized. These results
indicate that the 5, 10 and 15 mL fruit extract mediated ZnO NPs at
0.5 mg/100

m

L exhibited rather similar antibacterial and
anti-fungal efficacy against the Gram-Positive Staphylococcus aureus
and Aspergillus niger, respectively.

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2 0.05 11.0± 0.33 16.0± 0.88

3 0.005 10.5± 0.51 14.0± 0.66

4 0.0005 ne 13.5± 0.33

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