PHB/PCL fibrous membranes modified with SiO2?TiO2-based core?shell composite nanoparticles for hydrophobic and antibacterial applications

Article abstract of DOI:10.1039/c9ra04465e

In order to prepare multifunctional fibrous membranes with hydrophobicity, antibacterial properties and UV resistance, we used silica and titanium dioxide for preparing SiO₂?TiO₂ nanoparticles (SiO₂?TiO₂ NPs) to create roughness on the fibrous membranes surfaces. The introduction of TiO₂ was used for improving UV resistance. N-Halamine precursor and silane precursor were introduced to modify SiO₂?TiO₂ NPs to synthesize SiO₂?TiO₂-based core?shell composite nanoparticles. The hydrophobic antibacterial fibrous membranes were prepared by a dip-pad process of electrospun biodegradable polyhydroxybutyrate/poly-?-caprolactone (PHB/PCL) with the synthesized SiO₂?TiO₂-based core?shell composite nanoparticles. TEM, SEM and FT-IR were used to characterize the synthesized SiO₂?TiO₂-based core?shell composite nanoparticles and the hydrophobic antibacterial fibrous membranes. The fibrous membranes not only showed excellent hydrophobicity with an average water contact angle of 144° ± 1°, but also appreciable air permeability. The chlorinated fibrous membranes could inactivate all S. aureus and E. coli O157:H7 after 5 min and 60 min of contact, respectively. In addition, the chlorinated fibrous membranes exhibited outstanding cell compatibility with 102.1% of cell viability. Therefore, the prepared hydrophobic antibacterial degradable fibrous membranes may have great potential application for packaging materials.

Full text of DOI:10.1039/c9ra04465e

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PHB/PCL fibrous membranes modified with
SiO @TiO -based core@shell composite
2
2
Cite this: RSC Adv., 2019, 9, 23071
nanoparticles for hydrophobic and antibacterial
applications
Xinghuan Lin, Shanshan Li, Joonhoo Jung, Wei Ma, Lin Li, Xuehong Ren, *a
Yuyu Sun
a
a
b
a
a
b
c
and Tung-Shi Huang
In order to prepare multifunctional fibrous membranes with hydrophobicity, antibacterial properties and UV
resistance, we used silica and titanium dioxide for preparing SiO @TiO nanoparticles (SiO @TiO NPs) to
create roughness on the fibrous membranes surfaces. The introduction of TiO was used for improving
UV resistance. N-Halamine precursor and silane precursor were introduced to modify SiO @TiO NPs to
synthesize SiO @TiO -based core@shell composite nanoparticles. The hydrophobic antibacterial fibrous
membranes were prepared by a dip-pad process of electrospun biodegradable polyhydroxybutyrate/
poly-3-caprolactone (PHB/PCL) with the synthesized SiO @TiO -based core@shell composite
nanoparticles. TEM, SEM and FT-IR were used to characterize the synthesized SiO @TiO -based
core@shell composite nanoparticles and the hydrophobic antibacterial fibrous membranes. The fibrous
2
2
2
2
2
2
2
2
2
2
2
2
2
ꢀ
ꢀ
membranes not only showed excellent hydrophobicity with an average water contact angle of 144 ꢁ 1 ,
but also appreciable air permeability. The chlorinated fibrous membranes could inactivate all S. aureus
and E. coli O157:H7 after 5 min and 60 min of contact, respectively. In addition, the chlorinated fibrous
membranes exhibited outstanding cell compatibility with 102.1% of cell viability. Therefore, the prepared
hydrophobic antibacterial degradable fibrous membranes may have great potential application for
packaging materials.
Received 14th June 2019
Accepted 14th July 2019
DOI: 10.1039/c9ra04465e
rsc.li/rsc-advances
materials for food packing and medical materials still show
shortcomings, especially in respect to antibacterial properties.
1
Introduction
Due to a heightened awareness of environmental issues, there is Therefore, there is an urgent need to impart antimicrobial
an increasing demand on biodegradable materials as potential performance to improve their range of uses. Recently, antimi-
replacements of traditional polymeric materials, such as poly- crobial agents, such as inorganic metals and their oxides,
propylene (PP), polyethylene (PE), and polystyrene (PS), to organic macromolecules, including chitosan compounds and
1
–3
reduce waste accumulation. Furthermore, there is a growing quaternary ammonium compounds, and N-halamine have been
1
0–17
demand for global healthcare issues in regard to microbial widely used.
infections in a variety of areas such as food packing, medical extensively drawn attention due to their excellent antibacterial
Among these, N-halamine materials have
4–6
devices, textile materials and biomedical materials. There- efficacies, broad-spectrum sterilization and easy regener-
18,19
fore, the development of environmental-friendly alternative ability.
materials with efficient antibacterial properties is highly bicity of material surfaces is one of the most important
desirable.
characteristics for packaging materials. On one hand, materials
Aside from antibacterial properties, high hydropho-
Due to their biodegradability and biocompatibility, biode- applied for food packaging with excellent hydrophobicity can
gradable materials have been widely investigated concerning block the ingress of moisture and oxygen to slow down bacterial
20
potential applications as food packaging and biomedical growth and food spoilage. On the other hand, materials with
7–9
materials.
However, the properties of the biodegradable prominent hydrophobicity can exhibit a self-cleaning function
and may improve their antimicrobial properties. At present,
a salient hydrophobic surface is mainly prepared by building
a
a nano-structured surface and reducing surface energy on the
substrate.
Key Laboratory of Eco-textiles of Ministry of Education, College of Textiles and
Clothing, Jiangnan University, Wuxi, Jiangsu, 214122, China
21
b
Department of Chemistry, University of Massachusetts Lowell, Lowell, 01854, USA
Nanomaterial due to its small size and large specic surface
c
22–24
Department of Poultry Science, Auburn 36849, AL, USA. E-mail: xhren@jiangnan.edu.
area has many physical and chemical properties.
cn
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16
2 2 2 2
Electrospinning is a well-known and cost-effective technique to vibration of Ti–O. In contrast to SiO @TiO NPs, SiO @TiO -
produce nanobers from various polymers. The resulting elec- based core@shell composite nanoparticles had a few new
ꢂ1
trospun nanobers are useful in many applications such as bands at 2915 and 2850 cm attributed to the –CH and –CH –
3
2
25–27
ꢂ1
biomedical, lter and energy related materials.
bending vibration of the HDTMS, while 1771 and 1712 cm can
Over the last few years, nanoparticles including inorganic be ascribed to the C]O stretching vibration of the SPH.
38
particles, metal particles and others have been synthesized to
prepare different shapes and sizes with outstanding proper-
2
.2 Characterization of composite brous membranes
28,29
ties.
Subsequently, core@shell nanoparticles have attracted
2.2.1 SEM. The surface morphology and diameters distri-
considerable attention for nanotechnology elds owing to
chemical and colloidal stabilities, adjustable physical proper-
ties and controllability of interparticle interactions within
bution of the brous membranes were observed by SEM and are
shown in Fig. 2. The PHB/PCL brous membranes (Fig. 2A)
obtained were bead-free; the brous diameter ranged from 0.5
mm to 4 mm with an average of 2.32 mm. It can be seen from
30,31
assemblies.
In our previous study,
32,33
we found that synthesized N-
Fig. 2B that the surface of the PHB/PCL–SiO
SPH membranes became rough and the average diameter of
bers was 2.49 mm, thus showed no signicant difference
2 2
@TiO –HDTMS/
halamine siloxane compounds had poor stability under UV
irradiation, because its Si-alkyl group bond easily decomposed
which in return led to decreased chlorine content. Therefore, in

compared with the PHB/PCL brous membranes. Aer chlori-
nation (Fig. 2C), again there were no obvious changes in the
surface morphologies and the average diameter of brous
membranes measured 2.25 mm.
2 2 2 2
this study, we used TiO and SiO for building SiO @TiO NPs,
which SiO acted as a core for it is chemically inert, does not
2
affect redox reactions at the core surface and can easily be
34
modied with many other compounds, while TiO as a UV
2
2.2.2 FT-IR. FT-IR spectra of the prepared brous
light protecting agent acted as the shell owing to its unique
membranes are shown in Fig. 3. Compared with the spectra of
PHB/PCL brous membranes (a), additional bands appeared at
16,35
physical properties under UV light irradiation.
the hydrophobicity, we graed the N-halamine precursors and
silane precursors onto the SiO @TiO NPs to build multilevel
To improve
ꢂ1
1771, 1084 and 794 cm of PHB/PCL–SiO @TiO –HDTMS/SPH
2
2
2
2
(
b) which were assigned to the vibrational band of C]O,
asymmetric stretching vibration of Si–O–Si and a symmetric
stretching vibration of Si–O–Si on SiO @TiO -based core@shell
nanostructures. Polyhydroxybutyrate/poly-3-caprolactone (PHB/
PCL) served as a biodegradable substrate that could be elec-
trospun into nanobers. Subsequently, the synthesized N-
2
2
3
6,37
composite nanoparticles, respectively.
ties of –CH and –CH
Besides, the intensi-
halamine containing SiO @TiO -based core@shell composite
2
2
ꢂ1
3
2
– peak at 2918 and 2850 cm in spectra
nanoparticles were deposited onto these brous membranes
and chlorinated. Results demonstrated that the obtained
membranes exhibited remarkable antimicrobial activity against
S. aureus and E. coli O157:H7, respectively, outstanding hydro-
phobicity and appreciable air permeability. Moreover, the
chlorinated brous membranes displayed excellent UVA light
and storage stability. Besides, the active chlorine of that chlo-
rinated brous membranes could easily be recovered.
(
b) and (c) were obviously stronger than those in (a), which was
38
mainly attributed to the long alkyl chains of HDTMS. Aer
chlorination, the characteristic vibrational band of C]O shif-
ted from 1771 cm to 1788 cm , which was ascribed to the
ꢂ1
ꢂ1
39
transformation of N–H bond to N–Cl bond.
2
.3 Thermal analysis
The TGA and DTG of brous membranes are shown in Fig. 4.
There were two degradation steps that became apparent in the
TGA curves for PHB/PCL brous membranes (Fig. 4A). PHB was
the rst to degrade with its weight loss temperature ranging
2
Results and discussion
2 2
2.1 Characterization of SiO @TiO -based core@shell
composite nanoparticles
ꢀ
26
from 250 to 300 C. And PCL was the second to degrade with
ꢀ
The surface morphologies and structures of the nanoparticles its weight loss temperature ranging from 350 to 450 C. The
were observed by TEM and FT-IR and the results are shown in main decomposition temperature of PHB and PCL of PHB/PCL–
Fig. 1. It can be seen that the size of the prepared SiO
Fig. 1A) was relatively uniform; the average diameter was these in curve of PHB/PCL brous membranes, which might be
determined to be 129.6 ꢁ 10 nm, while the average diameter of due to cross-linking of SiO @TiO NPs at the surface of PHB/
2 2 2
NPs SiO @TiO –HDTMS/SPH brous membranes was higher than
(
2
2
SiO @TiO NPs (Fig. 1B) was 274.5 ꢁ 16 nm. It could be inferred PCL brous membranes. There was a new degradation step of
2
2
that the thickness of shell (TiO
2
) was 60 ꢁ 5 nm. Upon modi- PHB/PCL–SiO
@TiO
2
@TiO
2
–HDTMS/SPH brous membranes which
ꢀ

cation with HDTMS and SPH, the size of SiO
2
2
-based was ascribed to SPH, and its weight loss occurred at 450 C to
ꢀ
40
core@shell composite nanoparticles (Fig. 1C) was not visibly 550 C. Aer chlorination, the main degradation temperature
changed, which might due to the fact that HDTMS and SPH are of PHB, PCL and SPH decreased. It is possible that the N–Cl
rather small compounds compared to SiO
2
@TiO
2
NPs.
bonds of SPH broke and further accelerated the thermal
FT-IR spectra (Fig. 1D) show the bands at around 1058, 945 decomposition of brous membranes via a free radical
ꢂ1
15
and 794 cm owing to asymmetric stretching vibration of Si– process. The remaining residual mass of PHB/PCL brous
ꢀ
O–Si, stretching vibration of Si–O–H, and a symmetric stretch- membranes was 1.17% at 600 C, while it was 10.8% and 13.6%
ing vibration of Si–O–Si, respectively.
in the spectra of SiO @TiO NPs was assigned to the stretching PHB/PCL–SiO
36,37
ꢂ1
ꢀ
The band at 1100 cm
at 600 C, respectively, before and aer chlorination in case of
@TiO –HDTMS/SPH brous membranes. The
2
2
2
2
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Fig. 1 TEM images of (A) SiO
2
NPs, (B) SiO
2
@TiO
2
2 2
NPs and (C) SiO @TiO -based core@shell composite nanoparticles; (D) FT-IR spectra of
nanoparticles.
ꢀ

nal residual in case of PHB/PCL brous membranes at 600 C improvement in hydrophobicity of PHB/PCL brous
was just carbon, while in case of PHB/PCL–SiO @TiO –HDTMS/ membranes did not compromise the air permeability of the
2
2
ꢀ
SPH brous membranes at 600 C it included nitrogen, silica membranes aer surface modied. In addition, the chlorina-
and titanium.
tion process made no difference to hydrophobicity and air
permeability. Therefore, in conclusion the brous membranes
had good hydrophobicity and air permeability and may have
a great potential for applications as textile and biomedical
materials.
2.4 Hydrophobicity and air permeability
The contact angles and air permeability of brous membranes
were determined and the results are shown in Table 1. The
surface of PHB/PCL brous membranes was quickly wetted with
2.5 Antibacterial efficacy
2
mL of distilled water, while the surface of PHB/PCL–SiO
2
@-
TiO
2
–HDTMS/SPH brous membranes exhibited outstanding The antibacterial efficacy of brous membranes against S.
ꢀ
ꢀ
hydrophobicity with a contact angle up to 144 ꢁ 1 . There were aureus and E. coli O157:H7 were tested and the results are dis-
no signicant differences in contact angle before and aer played in Fig. 5. The initial populations of S. aureus and E. coli
6
6
chlorination. The PHB/PCL brous membranes displayed O157:H7 were 1.03 ꢃ 10 CFU per sample and 1.00 ꢃ 10 CFU
ꢂ1
excellent air permeability (54.6 ꢁ 2.6 mm s ), whereas the air per sample. Clearly, the PHB/PCL brous membranes (Fig. 5A)
permeability of the PHB/PCL–SiO @TiO –HDTMS/SPH brous had poor antibacterial property against S. aureus with log value
2
2
ꢂ1
membranes declined to 44.8 ꢁ 1.3 mm s . Aer chlorination, of 0.011 (2.43%) reduction within 60 min. Similarly, the PHB/
the PHB/PCL–SiO
2
@TiO
2
–HDTMS/SPH brous membranes PCL brous membranes (Fig. 5B) only caused 0.145 log reduc-
ꢂ1
showed good air permeability of 50.9 ꢁ 1.7 mm s . Thus, the tion of E. coli O157:H7 within 60 min. Aer modied with
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2 2 2 2
Fig. 2 SEM images and diameters distribution of PHB/PCL (A and D), PHB/PCL–SiO @TiO –HDTMS/SPH (B and E) and PHB/PCL–SiO @TiO –
HDTMS/SPH–Cl (C and F) fibrous membranes.
+
oxidative halogens (Cl ) to attracted to bacterial organisms, and
then destroyed the cell membrane of bacteria by oxidizing thiol
41
groups or halogenating amino groups in proteins. From
Fig. 5A and B, it can be seen that the chlorinated brous
membranes inactivated 100% of S. aureus and E. coli O157:H7
within 5 min and 60 min of contact time, respectively. The
antibacterial efficiency of the chlorinated brous membranes
against S. aureus was signicantly higher than E. coli O157:H7.
The different shapes and surface structures of bacteria might
cause them to adhere to the samples at different degrees, which
was in accordance with results reported by other research
32,42,43
groups.
2.6 Cytotoxicity test
The results of cytotoxicity tests of brous membranes were
shown in Fig. 6. The cell viability cultured in extract solution of
2 2
Fig. 3 FT-IR spectra of PHB/PCL (a), PHB/PCL–SiO @TiO –HDTMS/
SPH (b) and PHB/PCL–SiO
membranes.
2
@TiO
2
–HDTMS/SPH–Cl (c) fibrous PHB/PCL brous membranes declined dramatically to 69.6%
compared with the control sample. According to the Interna-
tional Standard Organization (ISO/EN 10993-5), the reduction of
44
cell viability by more than 30% is considered a cytotoxic effect.
2 2
SiO @TiO -based core@shell composite nanoparticles, the In this study, PHB/PCL brous membranes showed some
bactericidal efficacies of brous membranes against S. aureus degree of cytotoxic effect aer 24 h incubation. Aer modied
and E. coli O157:H7 improved slightly with log reductions of with SiO @TiO -based core@shell composite nanoparticles, the
2
2
0
.111 and 0.210, respectively, which might be attributed to the brous membranes showed good cell compatibility with 95.3%
35
addition of TiO2. In contrast, as expected, the bactericidal of cell viability. Aer chlorination, the cell viability of PHB/PCL–
percentages of the chlorinated membranes against S. aureus SiO @TiO –HDTMS/SPH brous membranes increased to
2
2
and E. coli O157:H7 were dramatically increased with the 102.1%, which was higher than that of the control. The result is
extension of contact time. Aer chlorination, N–H bonds of SPH consistent with the previous report that low concentration of
were converted to N–Cl bonds, which were able to release oxidative chlorine on the surface aer deoxidation transferred
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Fig. 4 TGA (A) and DTG (B) curves of the fibrous membranes.
ꢂ
46
into chloride containing Cl and these compounds could decomposition of N–Cl bonds. Aer rechlorination, the active
45
promote cell growth.
chlorine of the samples was 0.26 wt%, suggesting that 70% of
+
the initial active chlorine content (Cl % ¼ 0.37 wt%) could be
regained. The unrecovered chlorine content was ascribed to
2
.7 UVA light stability and storage stability
33,47
decomposition of Si–C bond.
compound had poor UVA light stability because Si-alkyl group
bond could break and result in the loss of the hydantoin ring
N-Halamine siloxane
The PHB/PCL–SiO @TiO –HDTMS/SPH–Cl brous membranes
2
2
were evaluated for UVA light and storage stability, and the
results are displayed in Fig. 7. From Fig. 7A, it can be seen that
the active chlorine content decreased with the extension of
irradiation time, and only 0.04 wt% (10.8% of the initial active
chlorine content) of active chlorine content remained aer 24 h
exposure. The loss of active chlorine was attributed to the
32,33
under UV irradiation.
2
The introduction of TiO in building
the core@shell structure and further modication of the brous
membranes could signicantly increase UVA light stability.
TiO2 is composed of a full valence band and a vacant
Table 1 Hydrophobicity and air permeability of fibrous membranes
Samples (brous membranes)
Air permeability
(mm s )
ꢀ
ꢂ1
Contact angle ( )
PHB/PCL
54.6 ꢁ 2.6
PHB/PCL–SiO
2
@TiO
2
–HDTMS/SPH
44.8 ꢁ 1.3
PHB/PCL–SiO
2
@TiO
2
–HDTMS/SPH–Cl
50.9 ꢁ 1.7
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Fig. 5 Antibacterial efficacy of fibrous membranes against (A) S. aureus and (B) E. coli O157:H7.
16,35
387.5 nm.
Thus, TiO
2
played an important role as a UV light
protecting agent to guard the structure of SPH from decompo-
sition, improving the UVA light stability of the chlorinated

brous membranes.
Fig. 7B shows that there was a slight decrease in the chlorine
content over storage time when the samples were kept in the
dark. Aer 60 days, the active chlorine content of the chlori-
nated PHB/PCL–SiO @TiO –HDTMS/SPH brous membranes
2
2
was 0.30%, and thus 83.3% of the original chlorine content
48
(
0.37%), which still had efficient antibacterial effect. Aer
rechlorination, almost all of the active chlorine of the brous
membranes was recovered. The above results indicated that the
N–Cl bond of the chlorinated PHB/PCL–SiO @TiO –HDTMS/
2 2
SPH brous membranes was relatively stable under dark
condition. Overall, the good UVA light and storage stability as
well as their chlorine rechargeability make the prepared anti-
microbial brous membranes useful materials for numerous
practical applications.
Fig. 6 Cell viability of rat skin fibroblasts on control and different
fibrous membranes after 24 h incubation.
3
Experimental
3.1 Materials and characterization
ꢂ1
conduction band, which allows the electrons to become tran- Polyhydroxybutyrate (PHB, M ¼ 30 000 g mol ) was provided
n
sitional between the valence band and the conduction band by Tianjin Green Bio Materials Co., Ltd (Green Bio), China. 5,5-
under UV light irradiation with wavelengths less than Dimethylhydantoin (DMH) was purchased from Hebei Yaguang
2 2
Fig. 7 UVA light stability (A) and storage stability (B) of chlorinated PHB/PCL–SiO @TiO –HDTMS/SPH fibrous membranes.
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Fine Chemical Co. Ltd. Octyl phenol ethoxylates-10 (OP-10) stirred vigorously to form a homogeneous solution. Then,
from Shengyu Chemical Co., Ltd, Shanghai, China. Poly-3-cap- a stock solution containing 10 mL TEOS and 10 mL ethanol was
ꢂ1
ꢂ1
rolactone (PCL, Mn ¼ 80 000 g mol ), tetra-n-butyl titanate added into the mixture at a rate of 0.5 mL min with a constant
(
TBT), hexadecyltrimethoxysilane (HDTMS) and (3-chlor- pressure funnel. Aer mixing vigorously, the mixture solution
opropyl) triethoxysilane were purchased from J&K Technology was vigorously stirring at 60 C for 2 h. Finally, the SiO
Co., Ltd, Shanghai, China. Tetraethoxysilane (TEOS), sodium were separated by centrifugation.
ꢀ
2
NPs
hydroxide (NaOH), sodium thiosulfate (Na
hypochlorite (10% chlorine content), azobis(isobutyronitrile) 100 mL ethanol : H
AIBN), potassium iodide (KI), chloroform (CHCl ), N,N-dime- 30 min, and 0.5 g OP-10 was added into the mixture. Another
2
S
2
O
3
), sodium
In the next step the SiO
2
NPs were dispersed uniformly in
2
O (19 : 1, v/v) in an ultrasonic bath for
(
3
thylformamide (DMF), ethanol and acetic acid were purchased solution containing 10 mL TTB and 10 mL ethanol was injected
ꢂ1
from Sinopharm Chemical Reagent Co., Ltd, Shanghai, China. into the above mixture at a rate of 0.5 mL min with a constant
Bacteria of S. aureus ATCC 6538 and E. coli O157:H7 ATCC 43895 pressure funnel. The resulting mix was stirred vigorously at
ꢀ
(
American Type Culture Collection, Rockville, MD) were used in 50 C for 12 h. Finally, the SiO
2
@TiO
2
NPs were separated by
this study.
The morphologies of membranes were characterized by
centrifugation.
The prepared SiO
2
@TiO
2
NPs were dispersed uniformly in
scanning electron microscopy (TM3030, Hitachi High Tech- the 100 mL ethanol solution and 0.5 g OP-10 was added to the
nologies, Japan) and the average diameter and size distribution dispersion in an ultrasonic bath for 30 min. Then, 8 wt% SPH,
of bers from the SEM images were determined by a nano- and 12 wt% HDTMS were added with vigorously stirring at room
measurer soware (Department of Chemistry, Fudan Univer- temperature for
4 h. The SiO @TiO -based core@shell
2 2
sity, Shanghai, China). Fourier transform infrared (FT-IR) composite nanoparticles were separated by centrifugation,
ꢀ
spectra were tested by a NEXUS 470 spectrometer (Nicolet washed 2 times with ethanol, and dried at 45 C. In Scheme 1
Instrument Corporation, USA). Transmission electron micro- the process is schematically illustrated.
scope (TEM) were characterized by a JEM 2100 TEM microscope
operated at 200 kV (Hitachi High Technologies, Japan), and the 3.5 Preparation of hydrophobic antibacterial brous
ꢂ1
samples (c ¼ 0.1–0.2 g L ) were obtained by dipping copper membranes
4
00-mesh carrier grids. Thermogravimetric analysis (TGA) was
Ten percent (w/v) of SiO @TiO -based core@shell composite
nanoparticles and one percent (w/v) AIBN were dissolved in the
ethanol solution in an ultrasonic bath for 30 min. The PHB/PCL
2
2
tested by a Q500 TGA (TA Instruments Co. Ltd., USA) via heating
ꢀ
5
1
mg sample from room temperature to 600 C at a rate of
ꢀ
0 C min. The air permeability was tested with a water vapor

brous membranes were dipped in the above colloidal solution,
transmission tester (YG 461E, Ningbo Textile Instrument Co.
Ltd., China).
followed by two dips (30 s of each dip) and two pads (wet pick-up
ꢀ
7
1
5–80%). Then, the brous membranes were dried at 60 C for
h. The treated brous membranes were washed thoroughly
3
.2 Preparation of PHB/PCL electrospun brous membranes
with ethanol and dried. And these membranes were called PHB/
Ten percent (w/v) of PHB/PCL (w/w, 40/60) were dissolved in PCL–SiO @TiO –HDTMS/SPH. Then, brous membranes were
2
2
ꢀ
chloroform at 45 C for 3–5 h under stirring. The nal solution soaked in a sodium hypochlorite solution (10 wt%, pH 7) at
was electrospun at room temperature to make brous room temperature for 1 h to render antimicrobial properties.
membranes. And the parameters were as followed: 20 kV of The chlorinated brous membranes were washed thoroughly
voltage, 1.5 mL h of ow rate and 20 cm of tip-to-collector and dried at 45 C for 1 h to remove unbound chlorine. These
distance.
membranes were called PHB/PCL–SiO @TiO –HDTMS/SPH–Cl.
ꢂ1
ꢀ
2
2
0
3
.3 Synthesis of 5,5-dimethyl-3-(3 -triethoxysilylpropyl)
3.6 Chlorine content measurement
hydantoin (SPH)
The active chlorine content on brous membranes was tested
by a modied iodometric/thiosulfate titration method. The
active chlorine weight percent of brous membranes was
calculated according to the eqn (1):
0
,5-Dimethyl-3-(3 -triethoxysilylpropyl)hydantoin (SPH) was
5
49
synthesized according to S. D. Worley reported. Hydantoin
sodium salt was prepared by mixing DMH with an equimolar
ꢀ
quantity of NaOH in ethanol to react for 10 min at 90 C. Aer
3
5:45 ꢃ N ꢃ V
ꢀ
þ
drying at 45 C for 2 days, the prepared hydantoin sodium salt
Cl ð%Þ ¼
ꢃ 100
(1)
2
ꢃ W
was dissolved in DMF, and subsequently (3-chloropropyl)trie-
+
ꢀ
thoxysilane was added with stirring at 95 C for 10 h. The SPH where, Cl (%) is the weight percent of active chlorine on the
was obtained through ltration and evaporation of DMF.
membranes, N is the normality (equiv. per L) and V is the
volume (L) of the Na solution, respectively, while W is the
weight (g) of chlorinated brous membranes.
2 2 3
S O
3
.4 Synthesis of SiO @TiO -based core@shell composite
2 2
nanoparticles
3
.7 Biocidal efficacy test
according to the protocol of previous studies. First, a mixture Gram-positive S. aureus (ATCC 6538) and Gram-negative E. coli
100 mL) of ethanol, H O and 10% NH OH (v/v/v, 5 : 4 : 1) was O157:H7 (ATCC 43895) were used to test the antibacterial
Colloidal silica nanoparticles (SiO2 NPs) were prepared
32
(
2
4
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2 2
Scheme 1 Synthesis of SiO @TiO -based core@shell composite nanoparticles.
properties for samples according to the modied AATCC 100- 3.8 Cell viability test
2
004 method. In this test, a certain volume of bacterial
In vitro biocompatibility of brous membranes was tested on rat
skin broblasts (ATCC CRL-1213) according to International
Standard Organization (ISO/EN 10993-5). Rat skin broblasts
6
7
suspensions (10 –10 CFU) were added to the center between
2
two pieces of brous membranes (2.54 ꢃ 2.54 cm ) and the
44
sample assemblies were held in place by putting a sterile weight
on top to make sufficient contact between the bacteria and the
membranes. Aer exposure to the bacteria for 5, 10, 30 and
were cultured in a media of Dulbecco's Modied Eagle Medium
(
1
DMEM), Fetal Bovine Serum (FBS) and Penstrip (v/v/v,
00 : 10 : 1) at 37 C under 5% CO2 atmosphere. Aer
ꢀ
6
0
0 min, the membranes were quenched with 5.0 mL sterile
.02 N sodium thiosulfate solutions to remove oxidative chlo-
culturing 3 generation of cells, an aliquot of 100 mL cell
4
suspension (ꢄ10 cells) was seeded in each well of 96-well
rine residuals and vortexed to release bacteria from brous
membranes to solution. 10-fold serial dilutions of the sterilized
solutions were prepared with phosphate buffer (100 mM, pH 7),
and each dilution was plated on Trypticase soy agar plate. The
agar plates were incubated at 37 C for 24 h, and the bacterial
colony counts were calculated for biocidal efficacy analysis.
plates, and, meanwhile, the membranes were immersed into
ꢀ
culture medium at 37 C under 5% CO
2
atmosphere for 24 h to
prepare liquid extracts. Aer 24 h incubation, the culture
medium was replaced with liquid extracts. Aer another 24 h
incubation with the extracts, 100 mL of fresh medium and 50 mL
of XTT/PMS reagent (v/v, 50 : 1) were replaced to each well and
ꢀ
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the plates were incubated dark for another 2–4 h. The absor-
bance of each well at OD490 nm was measured with a reference
Conflicts of interest
wavelength of OD690 nm using a microplate reader (Innity There are no conicts to declare.
M200 Pro, Tecan). Cells only incubated in culture medium were
tested under the same conditions to act as negative controls and
data were normalized with this blank control.
Acknowledgements
We would like to thank for the support of the Project of Jiangsu
Science and Technological Innovation Team, and the Funda-
mental Research Funds for the Central Universities (No.
JUSRP51722B, No. JUSRP11806), the National First-Class
Discipline Program of Light Industry Technology and Engi-
neering (LITE2018-2), and 111 Projects (B17021).
3
.9 Contact angle measurements
Water contact angle was tested by digital microscope contact
angle tester (26700-300, Instrument & Equipment Specialties
Inc., USA). 2 mL of distilled water was dropped on the surface of

brous membranes, and the contact angle was recorded aer
min for more than 5 times in different positions to calculate
1
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