5-Hydroxymethyl-2-vinylfuran: A biomass-based solvent-free adhesive

Article abstract of DOI:10.1039/c6gc02723g

5-Hydroxymethylfurfural (HMF) is an important platform chemical derived from biomass. Tremendous efforts have been made to transform HMF into valuable chemicals for applications in biofuels, materials science, and pharmaceuticals. Here we report the conversion of HMF into 5-hydroxymethyl-2-vinylfuran (HMVF), a versatile adhesive. HMVF can bond to a variety of substrates, e.g. metal, glass, plastics and rubber, under heating or acid treatment at room temperature. Mechanistic studies show that the vinyl group undergoes free radical polymerization and the hydroxyl group dehydrates to form an ether linkage to crosslink HMVF under either heating or acid treatment. The bonding strength (τ) of HMVF cured by heating (h-HMVF) is close to that of Krazy Glue (Loctite 401, cyanoacrylate) and higher than that of white glue (Pattex No. 710, PVA) and Pattex PKME15C epoxy glue. The outstanding adhesive performance of HMVF is attributed both to the interaction of hydroxyl groups with substrates and crosslinking by etherification between hydroxyl groups. Similar to Krazy Glue, HMVF is also used in its monomer form, which eliminates the use of solvents. Cells show good adhesion on crosslinked HMVF, which makes HMVF a potential bio-adhesive.

Full text of DOI:10.1039/c6gc02723g

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5-Hydroxymethyl-2-vinylfuran: A biomass-based solvent-free
adhesive
Miaomiao Han,a Xiao Liu,a,b Xiaosa Zhang,a,b Yuanyuan Pang,a,b Peng Xu,a,c Jianwei Guo,a,b Yadong
Liu,a Shuangyan Zhangd and Shengxiang Ji*a
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
5-Hydroxymethylfurfural (HMF) is an important platform chemical derived from biomass. Tremendous efforts have been
made on the transformation of HMF into valuable chemicals for applications in biofuels, materials science, and
pharmaceuticals. Here we report the conversion of HMF into 5-hydroxymethyl-2-vinylfuran (HMVF), a versatile adhesive.
HMVF can bond to a variety of substrates, e.g. metal, glass, plastics and rubber, under heating or acid treatment at room
temperature. Mechanistic studies show that the vinyl group undergoes free radical polymerization and the hydroxyl group
www.rsc.org/
dehydrates to form an ether linkage to crosslink HMVF under either heating or acid treatment. The bonding strength (τ) of
HMVF cured by heating (h-HMVF) is close to that of the Krazy Glue (Loctite 401, cyanoacrylate) and higher than that of the
white glue (Pattex No. 710, PVA) and the Pattex PKME15C epoxy glue. The outstanding adhesion performance of HMVF is
attributed to both the interaction of hydroxyl groups with the substrates and crosslinking by etherification between
hydroxyl groups. Similar to the Krazy Glue, HMVF is also used in its monomer form, which eliminates the use of solvents.
Cells show good adhesion on crosslinked HMVF, which makes HMVF a potential bio-adhesive.
by mussels. This mussel adhesive has striking underwater
adhesion property, and can bond dissimilar materials without
surface treatment;8 however, about 10,000 mussels are
Introduction
required to obtain 1 g of adhesive proteins.9 Instead of
extracting the proteins from mussels, lots of mussel mimetic
polymers have been developed by incorporating DOPA or
catechol into the side chains of polymers including
Adhesives play an important role in all aspects of our daily life.
Traditional adhesive materials, e.g. phenolic resin,
polyurethane (PU), polyvinyl acetate (PVA), epoxy, and
cyanoacrylate, are mostly made from petroleum resources.
Recently, the conversion of renewable biomasses to high-value
products has attracted considerable attention in order to tap
renewable feedstocks instead of fossil fuels.1 This has driven
lots of researches on the development of biomass derived
adhesives.2
polypeptides,8,10
polystyrenes,11-13
polyacrylates,14-18
polyethylene glycols,19-24 polyethylene,25 and polyurethanes.26
These bio-mimic adhesives show low to medium adhesion
performance.
Moreover, many of adhesives contain organic solvents and
auxiliary agents. The emission of toxic chemicals and volatile
organic compounds (VOCs) has caused consequent
environmental issues and shown certain damage to human
health for indoor use. Reduced usage of toxic chemicals and
VOCs is a state goal for many governments.27 163 states have
signed the “Stockholm Convention on Persistent Organic
Pollutants” in 2013 to reduce the emission of VOCs. Water-
based adhesives can substitute organic-based adhesives in
certain applications, but the poor solubility of polymeric
components will be an issue. Another alternative will be the
solvent-free adhesive which typically consists of either a
polymerizable monomer, e.g. cyanoacrylate, or crosslinkable
low Tg resins, e.g. liquid silicone resin.28 Compared to the
Soy protein-based adhesives have been widely used and are
characterized by low cost and high protein contents.3
However, the adhesive with native soy proteins exhibits a low
bonding strength (
are still working on the development of soy protein-based
τ
) (1.15 MPa).4 Up to now, a lot of studies
adhesives to address their drawbacks such as low
water resistance and enhance their performance.4-7
τ and poor
Another important protein-based adhesive which contains
high levels of 3,4-dihydroxyphenylalanine (DOPA) is produced
a.Key Laboratory of Polymer Ecomaterials, Changchun Institute of Applied
Chemistry, Chinese Academy of Sciences, 5625 Renmin Street, Changchun 130022,
P. R. China. E-mail: sji@ciac.ac.cn; Tel: +86-431-85262286
b.University of Chinese Academy of Sciences, 19 A Yuquan Rd, Shijingshan District,
Beijing 100049, P. R. China
evaporation of solvents in the solvent-based adhesives, the
τ
c. College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou,
Jiangsu 225009, China
builds up upon the consumption of monomers by
polymerization or the crosslinking of liquid resins in solvent-
free adhesives.
d.Petroleum Production Engineering Research Institute of Huabei Oilfield Company,
041 Huizhan South Road, Renqiu, Hebei 061552, China
†
DOI: 10.1039/x0xx00000x
Electronic
Supplementary
Information
(ESI)
available.
See
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In this report, we aim to develop a solvent-free biomass-
Journal Name
based adhesive from 5-hydroxymethylfurfural (HMF). HMF is
one of the valuable platform chemicals and mainly produced
by hydrolysis of saccharides. Extensive researches focus on the
conversion of HMF to 2,5-disubstituted furan derivatives such
as 2,5-furandicarboxylic acid, 2,5-bis(hydroxymethyl)furan, and
2,5-bis(aminomethul)furan.29-32 We, instead, intend to convert
HMF to 5-hydroxymethyl-2-vinylfuran (HMVF) and polymerize
HMVF to form a furan polymer with hydroxyl groups as the
side chains. Analogous to polyvinyl alcohol (PVA) which is a
common adhesive, the hydroxyl groups of the resulting
polymer from HMVF should interact with surfaces of many
materials and impart the adhesion to the substrates. We
envision that the intramolecular etherification reaction
between hydroxymethyl groups can take place to crosslink the
materials to significantly improve its adhesion performance.33
In addition, HMVF is a fully polymerizable and crosslinkable
Figure 1. Influence of the curing temperature and time on of HMVF under heating on
copper and aluminum plates. (square, dot and triangle marks refer to 90, 100 and 110
oC, respectively; blue and red marks refer to copper and aluminum plates, respectively.
)
liquid without the need of solvents. The
τ of HMVF is higher
than that of PVA and epoxy glues and similar to that of the
cyanoacrylate glue. The results demonstrate that HMVF is
indeed a good biomass-based solvent-free adhesive.
the adhesion was too weak to stand the weight of the copper
plate.
τ of h-HMVF on copper increased from 2.2±0.2 to
9.0±0.2 MPa with the increase of the temperature from 90 to
110 oC. It is unrealistic to further increase the curing
temperature since the evaporation of HMVF will be an issue.
Results and discussion
Preparation of HMVF
The curing time was optimized by heating the sandwiched
o
structures at 110 C for various times.
τ of h-HMVF on copper
The synthetic route for HMVF is outlined in Scheme 1. HMF was
synthesized by dehydration of fructose according to a literature
method.34 HMF in the aqueous phase was extracted by MIBK and
evaporation of the combined MIBK phase gave the crude HMF
with >95% purity by 1H NMR analysis (Figure S1 ). The crude HMF
was then converted to HMVF through the Wittig reaction.35 Vacuum
distillation gave HMVF, a colorless liquid with >98% purity by H
NMR analysis (Figure S2) and a viscosity of 4.2 mPa⋅s was
measured by a rotational viscometer.
increased from 0 to 9.0±0.2 MPa with the increase of the
heating time from 0.5 to 2 h. did not show further
improvement when the heating time was increased to 3 h. of
τ
τ
h-HMVF on aluminum showed a similar trend and the highest
(8.4±0.6 MPa) was also obtained at 110 oC for 2 h. The
τ
adhesion at high temperatures was also evaluated for the test
specimens cured at 110 oC for 2 h. When the adhesion test was
1
o
performed at 100 C,
τ of h-HMVF on aluminum dropped to
1.13±0.02 MPa. When the testing temperature was further
o
o
increased to 200 C, above its Tg of ~160 C,
aluminum was only 0.32±0.06 MPa.
τ of h-HMVF on
Subsequently, steel, glass, polyethylene (PE), PTFE, and
high-density white rubber were also used as lap shear
specimens. The τs of h-HMVF on different substrates were in
Scheme 1. Synthesis of 5-hydroxymethyl-2-vinylfuran (HMVF).
the following order: steel (9.7±0.4 MPa) > copper (9.0±0.2
MPa) > aluminum (8.4±0.6 MPa) > PE (2.8±0.4 MPa) > rubber
(0.38±0.01 MPa) > PTFE (0.31±0.02 MPa) (Figure 2). The HMVF
Evaluation of the adhesion property of HMVF
τ can be determined by measuring the bonding failure energy adhesive can easily bond to high-energy metals and the
of adhesives and is the most widely used parameter to maximum
τ of 9.7±0.4 MPa was obtained on steel substrates.
determine the adhesion property.13 Two substrates (copper The excellent adhesion performance on metals may be
and aluminum) were used for the lap shear test. We attributed to the coordination of the hydroxyl group of h-
performed experiments to investigate the effect of the curing HMVF to metal surfaces. Compared to metal surfaces, τ of h-
temperature and time on of h-HMVF on copper (Figure 1). HMVF sandwiched between low-energy surfaces, e.g rubber,
τ
HMVF polymerized upon heating to form h-HMVF, an insoluble PE or PTFE, was much lower. Moreover, glass substrates were
resin. The optimum curing temperature was determined by broken during the lap shear test, and the overlap area was
heating a ~100 ꢀm-thick layer of HMVF that was sandwiched reduced to 0.4 cm×2.5 cm. Glass surface, a typical polar
between two copper plates at 80-110 oC for 2 h. When the surface, has an attraction with the hydroxyl group of h-HMVF.
curing temperature was 80 oC, the adhesive turned viscous and
τ on glass is 5.7±0.25 MPa, higher than that of polymer
substrates but lower than that of metal substrates.
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Table 1. The bonding strength (
τ
), in MPa, for HMVF under heating and commercial glues sandwiched between substrates.
Aluminum
Copper
Rubber
PE
HMVF a
8.4±0.6
6.0±0.5
5.0±0.5
8.5±0.7
9.0±0.2
3.4±0.3
2.2±0.1
8.9±0.2
0.38±0.01
0.10±0.02
0.21±0.01
0.76±0.01
2.8±0.4
0.17±0.03
0.17±0.12
1.7±0.1
PVA (white glue, No. 710, Pattex, Henkel Corp.)b
Epoxy (PKME15C, Pattex, Henkel Corp.)b
Cyanoacrylate (Loctite 401, Henkel Corp.)b
Curing conditions: a 110 oC 2 h; b room temperature. Time from bonding to testing for all samples is 24 h.
shear test (Table 1). HMVF and PVA (Pattex No. 710) were
compared side by side since cured HMVF also contained lots of
hydroxyl groups. In both PVA and h-HMVF, the interaction of
the hydroxyl groups with the substrate imparted the
outstanding adhesion performance. Although PVA and h-
HMVF both have hydroxyl groups, the PVA glue is already
polymerized and did not subsequent react while HMVF is
applied onto substrate in the form of a flowing monomer
followed by polymerization and crosslinking. The cured HMVF
outperformed PVA on these four substrates and the
HMVF were much higher than those of PVA.
τs of h-
To verify the effect of hydroxyl group of HMVF for bonding,
the hydroxyl group was methylated to form 5-methoxymethyl-
2-vinylfuran (MMVF) (Scheme S1). MMVF could not bond the
glass plates under the same curing process as HMVF, but could
be polymerized via free radical polymerization to form fully
soluble PMMVF, indicating that the hydroxyl group plays a key
role for bonding.
Figure 2. Adhesion performance of HMVF sandwiched between two substrates. (Note:
the overlap area of glass substrates was reduced to 0.4 cm × 2.5 cm, because the glass
substrates were broken before the failure of adhesives during the lap shear test)
HMVF was also compared with epoxy resins since both of
them were in insoluble, crosslinked forms after cure and
crosslinking contributed to their high bonding properties.8,36,37
The two-component epoxy adhesive Pattex PKME15C was
cured at room temperature. The adhesion tests showed that
Instead of thermal curing, exposure to an acid can cure
HMVF at room temperature to form a crosslinked mat (a-
HMVF), which might find applications for low temperature
o
applications. A thin film (~100 ꢀm) of HMVF was coated on the
HMVF cured at 110 C outperformed Pattex PKME15C on the
copper plate and exposed to CF3COOH, HCl and CH3COOH
vapor, respectively. The film turned dark and solidified
immediately upon the exposure to CF3COOH vapor for 3
seconds. In contrast, the film became viscous and had brown
color when it was placed over concentrated HCl for 3 seconds.
Two films exposed to the HCl vapor were sandwiched right
after exposure and the sandwiched structure was cured at
room temperature for 1 day. The adhesion test showed that
four substrates (Table 1). In addition, HMVF catalyzed by HCl
vapor also had higher τ than epoxy cured by base at room
temperature on copper. For both adhesives, crosslinking
played an important role in adhesion.
HMVF is used in its pure monomer form and the liquid can
be cured without the addition of any additive or solvent,
analogous to the cyanoacrylate glue. For both glues, the
adhesion gradually builds up upon polymerization. The
difference is that cyanoacrylate undergoes anionic
polymerization in the presence of a weak base, such as water,
while in addition to crosslinking HMVF mainly undergoes free
radical polymerization. The overall performance of HMVF is
close to that of the cyanoacrylate glue Loctite 401 on these
four substrates.
τ
was 4.9±0.2 MPa. CH3COOH vapor treatment for 1 minute
did not result in noticeable change of color and viscosity.
These results showed that the stronger the acid the faster the
curing process, which might allow us to optimize the choice of
acid for specific application.
Comparison to commercial glues
Cytotoxicity of HMVF and cell adhesion of h-HMVF
The main text of the article should appear here with headings
as appropriate. A better evaluation and understanding of the
adhesion performance of a new adhesive is to directly
compare with commercially available glues. Three
commercially available glues (Loctite 401, Pattex No. 710, and
Pattex PKME15C) were chosen for comparison. Two metal
substrates (aluminum and copper), a rubber substrate (white
rubber), and a plastic substrate (PE) were employed for the lap
There is a growing interest in developing medical adhesives in
demand for applications such as surgical adhesives, orthopedic
cements, and dental glues over the past decades. Accordingly,
the adhesive should be nontoxic for use. The cytotoxicity is an
important parameter to evaluate for the use as a bio-adhesive.
The MTT assay by using preosteoblast MC3T3-E1 cells was
measured in vitro and the result was shown in Figure 3A.
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o
MC3T3-E1 cells were incubated in the culture media with the chamber at 110 C and the FTIR spectra were collected every
HMVF concentration ranging from 0.01 to 20 mg/mL. When minute during heating. Figure 4 shows the time evolution of
the concentration is less 2.5 mg/mL, the cell viability was FTIR spectra of HMVF heated for 0, 30, 60 and 120 min. The
higher than 80%. Moreover, the biocompatibility of h-HMVF intensities of the bands at 1810 (=CH2 overtone), 1641 (C=C st)
was also assessed. H9C2 cells were seeded and cultured for 3, and 902 (C=C-H
δ
oop) cm-1 that are associated with the vinyl
6, 12 and 24 h on h-HMVF and the morphologies of cultured group in HMVF gradually decreased with the increase of
cells were shown in Figure 3B. Cytoskeleton staining showed heating time. The curing process consumed the vinyl group by
that H9C2 cells were well spread and organized. The H9C2 cells radical polymerization, in agreement with the increase of
showed an elongated, spindle-like morphology on the h-HMVF intensities of C-H stretching of saturated hydrocarbons at 2937
after 6 h culturing. Meanwhile, F-action staining showed the and 2870 cm-1.
presence of polymerized action fibers lying parallel one to
each other. Overall, the H9C2 cells maintained their normal
polygonal morphology with multiple cellular projections on the
substrate. These results proved that h-HMVF showed good cell
adhesion and HMVF could be potentially used as a bio-
adhesive.
Figure 4. Time evolution of FTIR spectra of HMVF heated at 110 oC.
h-HMVF is a glassy solid and insoluble in any solvent. The
solubility property revealed that crosslinking also happened
along with the radical polymerization during curing. The h-
HMVF solid was then vitrified in liquid nitrogen and grinded
into fine powders. Solid state 13C NMR spectroscopy was also
used to investigate the structure of h-HMVF (Figure 5). The
peaks at 124.9 and 112.5 ppm in HMVF (Figure 5A)
disappeared in h-HMVF (Figure 5B) and a strong peak at 34.7
ppm associated with the saturated hydrocarbons showed up in
h-HMVF, which agreed with FTIR results that the vinyl group
was consumed through polymerization to form saturated
hydrocarbons. There also had a new broad peak at 64.7 (7’)
ppm which was from the etherification product between the
hydroxylmethyl group. Analogous to h-HMVF, HMVF exposed
to an acid vapor also formed a brown insoluble solid (a-HMVF).
The broad peak at 67.8 ppm which was from the etherification
product was also appeared in a-HMVF (Figure 5C). Compare to
h-HMVF, there is some unreacted vinyl group (~125 ppm) in a-
HMVF, but the degree of etherification of a-HMVF was higher
and the ether peak intensity was stronger. The
τ of a-HMVF
on copper was lower than that of h-HMVF, which might be due
to the lower degree of polymerization.
Figure 3. (A) In vitro cytotoxicity of HMVF against rat MC3T3-E1 cells as a function of
HMVF concentration. (B) The morphology of rat H9C2 cells cultured for 3, 6, 12 and 24
h on h-HMVF films. The scale bar represents 100 ꢀm.
Moreover, elemental analysis showed that the h-HMVF
powder contained 69.64 wt.% C and 6.47 wt.% H (C7H7.81O1.80),
and the a-HMVF powder contained 68.92 wt.% C and 6.29
wt.% H (C7H7.67O1.89). Compared to HMVF (C7H8O2, 67.73 wt.%
C and 6.50 wt.% H), the slight increase of C and decrease of H
in h-HMVF and a-HMVF was attributed to the loss of water
Curing mechanism of HMVF
The curing process was monitored by FTIR equipped with a
heating chamber. A drop of HMVF was sandwiched between
two KBr plates. The plates were placed in the pre-heated
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through dehydration, which agreed with the ether formation simultaneously. A possible mechanism for the HMVF curing
in 13C NMR spectra.
process was proposed and illustrated in Figure 6. The curing
process might undergo two pathways: 1) HMVF was
polymerized to form a linear PHMVF and then crosslinked via
dehydration; and 2) HMVF was dimerized via dehydration to
form biHMVF which functioned as a crosslinker during HMVF
polymerization.
Experimental
Materials
Methyltriphenylphosphonium bromide was purchased from
Sigma-Aldrich, and all the other reagents and solvents used in
this work were purchased from Aladdin. The reagents and
solvents were used as received without purification.
Measurements
The 1H and 13C NMR spectra were collected on a Bruker DDMX
300 spectrometer (300 MHz) at 25 oC with CDCl3 as the
solvent. Solid-state 13C NMR spectra were collected on a
Figure 5. (A) 13C NMR spectrum of HMVF (in CDCl3, 300 MHz); (B) solid-state 13C NMR
spectrum of h-HMVF (400 MHz); (C) solid-state 13C NMR spectrum of a-HMVF (400
MHz).
Bruker AVANCEⅢ 300 WB spectrometer (400 MHz).
Synthesis of 5-hydroxymethylfurfural (HMF) and 5-
hydroxymethyl-2-vinylfuran (HMVF) (Scheme 1)
HMF was synthesized according to our previous report.34 D-
fructose (20.0 g, 112 mmol), deionized water (20 mL), MIBK
(20 mL) and phosphoric acid doped polybenzimidazole (PA-PBI)
(2.0 g) were charged into a pressure flask. The reaction
o
mixture was heated in the oil bath under stirring at 180 C for
2 h. After reaction, the aqueous solution was extracted with
MIBK (3×20 mL) and the combined organic phase was dried
over MgSO4. Evaporation of MIBK gave 10.1 g (71%) of crude
HMF, a dark brown oil.
Methyltriphenylphosphonium bromide (37.0 g, 104 mmol),
K2CO3 (33.0 g, 240 mmol) and H2O (5 mL) was dispersed into
1,4-dioxane (400 mL) under a nitrogen atmosphere at room
temperature. HMF (10.1 g, 80 mmol) in 1,4-dioxane (100 mL)
was slowly added into the above slurry and the resulting
o
mixture was stirred at 90 C for 3 h. The reaction mixture was
filtered and 1,4-dioxane was removed by evaporation. The
residue was dissolved in diethyl ether. The organic phase was
washed with deionized water five times and dried over MgSO4.
Evaporation of diethyl ether gave a slightly yellow oil. Vacuum
distillation of the crude oil gave HMVF, a colorless liquid (6.8 g,
o
1
69%, T=41-43 C/0.2 mbar). H NMR (CDCl3, 300 MHz):
δ 2.04
(s, 1H, -OH), 4.59 (s, 2H, -CH2-OH), 5.16 (d, J=12 Hz, 1H, cis –
CH=CH2), 5.67 (d, J=18 Hz, 1H, trans –CH=CH2), 6.20 (d, J=3 Hz,
1H, furan H-3), 6.28 (d, J=3 Hz, 1H, furan H-4), 6.47 (q, J1=12 Hz,
Figure 6. Proposed cross-linking mechanism for HMVF.
J2=18 Hz, 1H, -CH=CH2). 13C NMR (CDCl3, 300 MHz):
δ 57.41 (-
Both FTIR and 13C NMR analyses confirmed that the vinyl
group was consumed by polymerization, while 13C NMR and
elemental analysis revealed that etherification between the
hydroxyl group happened. A small fraction of insoluble
materials was observed even at the early stage of curing, while
the soluble part contained HMVF monomer and linear PHMVF
CH2-OH), 108.81 (furan C-3), 109.48 (furan C-4), 112.46 (-
CH=CH2), 124.93 (-CH=CH2), 153.17 (furan C-2), 153.50 (furan
C-5).35
Adhesion study
The lap-shear adhesion was measured according to GB 7124-
86. The test substrates include steel, copper, aluminum, glass,
1
as shown in the H NMR spectrum (Figure S7), indicating that
vinyl
polymerization
and
etherification
occurred
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PE, PTFE, and rubber with a size of 10 cm (length) × 2.5 cm cells were observed by an inverted microscope (TE2000-U,
(width) x 3 mm (thickness). The overlap area is 1.2×2.5 cm2, Nikon).
and the schematic is shown in Figure S3. All substrates were
washed in acetone by ultrasonication. Metal substrates were
Conclusions
polished by sand paper before applying the glues. The
substrates were clamped and cured by heating in an oven, and
then placed at room temperature for 24 h; or the coated glue
layer was treated with an acid vapor for 3 seconds and the
substrate was clamped and cured at room temperature for 24
h. Lap shear adhesion measurements were conducted on an
INSTRON-5869 50 KN at a test speed of 2 mm/min. The
A
biomass
-based solvent-free adhesive
,
HMVF, was
synthesized from HMF through the Wittig reaction. HMVF
could be cured by either heating or acid treatment and
exhibited strong adhesion to steel, copper, aluminum and glass
and relatively weak adhesion to PE, rubber and PTFE. The
interaction of the hydroxyl groups with the substrate and
crosslinking between hydroxyl groups through etherification
imparted the outstanding adhesion performance of HMVF.
HMVF was used in the monomer form, which eliminates the
use of solvents. HMVF might also be formulated with other
glues as both the solvent and the active component. Cell
adhesion results showed that HMVF had the potential to be a
bio-adhesive.
maximum bonding force in Newtons was recorded. The final
τ
in megapascals was obtained by dividing the maximum load at
failure, in Newtons, by the measured overlap area of adhesive
in square meters. The values were averaged from five
repeated runs.
In vitro cytotoxicity assay
The cytotoxicity of HMVF was assayed using the 3-(4,5-
dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium
bromide
(MTT) assay. All samples were sterilized by UV for 1.5 h before
use. HMVF was added into RPMI 1640 medium (Gibco)
Acknowledgements
supplemented with 10% fetal calf serum (FBS) (Gibco) and 100 We gratefully thank the funding from the National Natural
U/mL penicillin-streptomycin (Sigma) with different Science Foundation of China (No. 51303175, 51203154,
concentrations. Preosteoblast MC3T3-E1 cells were seeded in 51173181, and 51373166), “The Hundred Talents Program"
96-well plates at the density of 1×104 cells per well and from the Chinese Academy of Sciences, the Program of
o
incubated at 37 C in a humidified 5% CO2 atmosphere for 24 Scientific Development of Jilin Province (No. 20150204027GX)
h. 20
to each well. The MTT solution was removed 4 hours later and Department of Science and Technology of Jilin Province (No.
200 L of DMSO was added to dissolve the formazan crystals. 20160414032GH).
ꢀL of the MTT stock solution in PBS (5 mg/mL) was added and the International S&T Cooperation Program from
ꢀ
The optical density (OD) of the well was measured at 492 nm
with a Microplate Spectrophotometer (MultiskanMK3, Thermo
Electron Corporation, USA). The relative cell viability (%) was
calculated according to Equation 1:
Notes and references
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2
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ꢌ
ꢐ
ꢐ
ꢍꢎꢏ
ꢑꢒꢓꢔꢕꢖꢜ × 100
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ꢊ
ꢀꢁꢂꢂ ꢃꢄꢅꢆꢄꢂꢄꢇꢈ % = ꢋꢌ
ꢍꢎꢏ
ꢗꢘꢙꢚꢛꢘꢕ
3
where [abs]sample and [abs]control were the absorbance of the
cell treated with the material solution and culture medium,
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HMVF was coated onto cover slides (15 mm diameter) that
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