Nano Res
1
Quantitative study of protein coronas on gold nanoparticles with different surface modifications
Menghua Cui, Renxiao Liu, Zhaoyi Deng, Guanglu Ge, Ying Liu (), and Liming Xie () Nano Res., Just Accepted Manuscript • DOI: 10.1007/s12274-013-0400-0
http://www.thenanoresearch.com on December 14 2013
© Tsinghua University Press 2013
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Nano Research
DOI 10.1007/s12274-013-0400-0
1
Quantitative Study of Protein Coronas on Gold
Nanoparticles with Different Surface Modifications
Menghua Cui, Renxiao Liu, Zhaoyi Deng, Guanglu
Ge, Ying Liu* and Liming Xie*
Key Laboratory of Standardization and Measurement for
Nanotechnology of Chinese Academy of Sciences,
National Center for Nanoscience and Technology, Beijing
100190, China
Page Numbers. The font is
ArialMT 16 (automatically
inserted by the publisher)
For bovine serum albumin, transferrin and fibrinogen on gold
nanoparticles (AuNPs), PEG surface modification showed no
protein adsorption. For other surface modifications, the
interaction between protein and AuNPs are strongly dependent
on both surface modification and protein.
Liming Xie, www.nanoctr.cn/xie
2
Quantitative Study of Protein Coronas on Gold Nanoparticles with Different Surface Modifications
Menghua Cui, Renxiao Liu, Zhaoyi Deng, Guanglu Ge, Ying Liu (), Liming Xie () CAS Key Laboratory of Standardization and Measurement for Nanotechnology, National Center for Nanoscience and Technology,
Beijing 100190, P. R. China
Received: day month year / Revised: day month year / Accepted: day month year (automatically inserted by the publisher) © Tsinghua University Press and Springer-Verlag Berlin Heidelberg 2011
ABSTRACT Protein corona provides the biological identity of nanomaterials in vivo. Here we have used dynamic light
scattering (DLS) and transmission electron microscopy (TEM) to investigate the adsorption of serum proteins,
including bovine serum albumin (BSA), transferrin (TRF) and fibrinogen (FIB), on gold nanoparticles (AuNPs)
with different surface modifications [citrate, thioglycolic acid, cysteine, polyethylene glycol (PEG, Mw=2k and
5k)]. AuNPs with PEG (5k) surface modification showed no protein adsorption. AuNPs with non-PEG surface
modifications showed aggregation with FIB. AuNPs with citrate and thioglycolic acid surface modifications
showed 6-8nm thick BSA and TRF coronas (corresponding to monolayer to bilayer proteins), in which the
microscopic dissociation constants of BSA and TRF protein coronas are in the range of 10-8 to 10-6 M.
KEYWORDS Protein corona, gold nanoparticle, dynamic light scattering, transmission electron microscopy, surface
modification
Nanoparticles with size of 1 to 100 nm have
potential applications in bio-imaging[1,2], drug
delivery[3] and cancer therapeutics[4,5]. When
nanoparticles contact with biological fluids, protein
coatings (so-called ‘protein coronas’) are formed on
nanoparticles[6]. Protein corona changes the size of
nanoparticles, alters the surface properties of
nanoparticles and then governs the interactions
between nanoparticles and cells. As a result, protein
corona determines the fate of nanoparticles in
biological system[6]. Therefore, the dynamics and
thermodynamics of protein coronas are of
fundamental importance to various bio-applications
of nanoparticles.
Many studies have been conducted to investigate
interactions between nanoparticles (including gold
Nano Res DOI (automatically inserted by the publisher) Research Article Please choose one
———————————— Address correspondence to Liming Xie, [email protected]; Ying Liu, [email protected]
3
nanoparticles (AuNPs)[7-11], quantum dots
(QDs)[12,13], FePt nanoparticles[12,14,15], polymer
nanoparticles[16,17]) and plasma proteins
(including serum albumin[7,9,10,12,13,17],
transferrin (TRF)[14,16], fibrinogen (FIB)[9,11],
γ-globulin[9] and apolipoprotein[15]). Generally,
protein adsorption on nanoparticles can be
described by the Hill equation[10,12],
where θ is protein coverage on nanoparticle surface;
[Protein] is the free protein concentration; 'DK is
the microscopic dissociation constant (equal to
protein concentration at half coverage); n is Hill
coefficient. For positively/negatively cooperative
absorption, n is larger/less than 1, respectively. For
serum protein adsorption on nanoparticles, 'DK is
usually in the range of 10-8 to 10-3 M and n is close to
1[7,9,10]. For example, 'DK is ~10-6 M and n is ~0.8
for BSA adsorption on citrate-stabilized AuNPs[9].
Dynamically, protein coronas consist of
irreversible, strongly bounded ‘hard coronas’ and
reversible, weakly bounded ‘soft coronas’, which
were evidenced by fluorescence correlation
spectroscopy (FCS) study[16] on TRF adsorption on
sulfonate and carboxyl polystyrene nanoparticles.
Many factors, such as nanoparticle-protein
interactions, protein abundance and even
protein-protein interactions, affect the composition
and structure of protein coronas. Similar to protein
coronas determining the biological identity of
nanoparticles[6], surface properties of nanoparticles,
such as surface chemical groups and surface
electrostatic potential, may govern interactions
between nanoparticles and proteins[18,19], though
the size of nanoparticles also affects the interactions
to some extent[9,18]. The interactions between
proteins and nanoparticles with different surface
modifications are complicated. It is accepted that
polyethylene glycol (PEG) functionalization can
decrease protein adsorption[10,20]. Much work has
focused on carboxyl functionalized nanoparticles,
such as citrate-stabilized AuNPs[9],
carboxyl-polymer-warped FePt nanoparticles[12],
carboxyl-functionalized QDs[12] and carboxyl
polystyrene nanoparticles[16]. Little work has been
done on protein coronas on other surface
modifications. Here we have investigated protein
(BSA, TRF and FIB) coronas on AuNPs with
different surface modifications [citrate (physically
adsorbed), carboxyl, carboxyl plus amine and PEG]
by dynamic light scattering (DLS) and transmission
electron microscopy (TEM). Microscopic
dissociation constant 'DK , Hill coefficient n and the
thickness of protein coronas have been obtained.
As-bought citrate-stabilized AuNPs show a core
diameter distribution of 38.6±3.0 nm (imaged by
TEM, Figure 1a and 1b) and a hydrodynamic
diameter of 43 nm (measured by DLS, Figure 1d).
Slightly larger hydrodynamic diameter measured
by DLS could be due to citrate adsorption and
electrical double layer on the AuNP surfaces.
UV-Vis characterization also showed plasmonic
absorption at ~530 nm (Figure 1e). Ligand
exchange[21] and then dialysis were used to
prepare AuNPs with different surface modifications
(Figure 1c). Thioglycolic acid, cysteine,
methoxypoly(ethylene glycol) thiol
(HS(CH2CH2O)nCH3, Mw=2k, 5k) were used to
prepare AuNP-SCH2COOH (AuNP-COO-, at
pH=7.4), AuNP-SCH2CH(NH3+)COO- (at pH=7.4,
AuNP-Cys), AuNP-S-(CH2CH2O)nCH3 (Mw=2k)
[AuNP-PEG(2k)] and AuNP-S-(CH2CH2O)nCH3
(Mw=5k) [AuNP-PEG(5k)]. Since the binding of
citrate on gold surface is weak, thiols can replace all
citrates on AuNP surfaces via strong Au-S
bond[21,22]. UV-Vis characterization revealed that
neither peak broadening nor new peak at longer
wavelength was observed (Figure 1e), indicating no
aggregation.
Figure 2 (top panels) shows typical DLS correlation
curves for surface modified AuNPs at different BSA
concentrations. In Figure 2e, no hydrodynamic
diameter increase was observed, indicating no BSA
adsorption on AuNP-PEG(5k). In contrast, for
citrate-AuNPs, AuNP-COO-, AuNP-Cys and
AuNP-PEG(2k) (Figure 2a-d top panels), the
correlation curve shifted to longer lag time at higher
BSA concentrations, indicating larger particle
diameters. And the DLS correlation curves at
different BSA concentrations show a similar drop
'
[Protein] (1)
[Protein] ( )
n
n nDK
4
slope as lag time increases, indicating little changes
in diameter distribution (polydispersion index data
in Figure S-1). Cumulative fitting of the correlation
curves can give nanoparticle diameters at different
BSA concentrations (Figure 2 bottom panels). For
citrate-AuNPs, AuNP-COO-, AuNP-Cys and
AuNP-PEG(2k), the diameter increased deeply at
BSA concentration of ~50 nM. The total diameter
increase was ~16 nm, corresponding to a protein
corona thickness of ~8 nm. Considering the
hydrodynamic size of BSA[23] is 14×4×4 nm3, an
8nm-thick corona might correspond to a ‘titled’
conformation of BSA on AuNP surface or two ‘flat’
layers of BSA[10,12].
To quantify interactions between BSA and AuNPs
with different surface modifications, a model[12],
was adopted, where dz([Protein]) and dz(0) are
hydrodynamic diameters of AuNPs with/without
protein, respectively, c is a scaling constant. Since
bounded protein molecules should be much less
than free protein molecules, total protein
concentration was used as free protein
concentration. Fitting hydrodynamic diameter
dependence on protein concentration gives 'DK
and n values for protein-nanoparticle interactions
(Figure 2 bottom panels). Citrate-AuNPs shows a
lager 'DK and an n value of less than 1.
AuNP-COO- and AuNP-Cys show a smaller 'DK
and an n value of larger than 1, indicating a
stronger and positively cooperative adsorption.
AuNP-PEG(2k) shows a similar 'DK value as
citrate-AuNPs and AuNP-PEG(5k) shows no BSA
binding, which indicates that PEG chain length
matters in the BSA binding and longer PEG chain
length prohibited BSA adsorption.
The same experiments were done for TRF on
AuNPs (Figure 3) and similar results were observed.
No TRF adsorption was observed on AuNP-PEG(2k)
and AuNP-PEG(5k). More than 10nm diameter
increase was observed for AuNPs with other four
surface modifications. For citrate-AuNPs and
AuNP-COO-, the nanoparticles-protein interaction
is stronger (smaller 'DK ) for TRF than that for BSA.
The TRF corona thickness on citrate-AuNPs and
AuNP-COO- is ~6-7 nm measured by DLS,
suggesting the monolayer of TRF (hydrodynamic
diameter of TRF ~7 nm[16,24]). For TRF adsorption
on AuNP-Cys, the diameter increased by 60 nm at
high TRF concentrations. The surface of AuNP-Cys
has both –NH3+ and –COO- groups, which could
favor multiple hydrogen bonds or electrostatic
interactions between AuNPs and TRF, and then
accounts for aggregation.
FIB adsorption on AuNPs was also investigated by
DLS (Figure 4). No FIB adsorption was observed on
AuNP-PEG(2k) and AuNP-PEG(5k). Large
aggregation was observed for citrate-AuNPs,
AuNP-COO- and AuNP-Cys (hydrodynamic
diameter up to several hundreds to one thousand
nanometers. This is consistent with the fact that FIB
is easy to aggregate after structure changing
because of knob-hole interactions between different
motives of FIB[25].
At last, we did transmission electron microscopic
(TEM) imaging on the protein coronas by drying
the protein-AuNPs solution on TEM grids (Figure
5). For AuNPs without proteins (Figure 5a-e), no
corona coating was observed except that
AuNP-COO- and AuNP-Cys showed a ~1 nm-thick
corona structure (maybe due to the staining of
surface -COOH by uranyl acetate). For BSA coronas
on citrate-AuNPs, AuNP-COO-, AuNP-Cys and
AuNP-PEG(2k), TEM revealed a corona thickness of
~3-5 nm (Figure 5f-i), which was smaller than that
measured by DLS (6-8 nm). One possibility is that
the protein corona in solution consists of two layers
of proteins since usually one layer BSA corona is ~4
nm of thickness visually on AuNPs and FePt
nanoparticles[10,12]. During drying, soft coronas
were dissociated from AuNPs.
For TRF coronas on citrate-AuNPs and AuNP-COO-,
the thickness observed by TEM was also 3-5 nm
(Figure 5k,i), suggesting TRF monolayer (the
physical dimension of TRF is ~4.2×5×7 nm3[26]). The
TEM measured corona thickness was slightly
smaller than that measured by DLS (~6-7 nm)
possibly due to TRF dehydration.
FIB coronas on citrate-AuNPs, AuNP-COO- and
AuNP-Cys were loosely around AuNPs (Figure
3'
[Protein]([Protein]) (0) 1 (2)
[Protein] ( )
n
z z n nD
d d cK
5
5p-r), which was not so dense as BSA and TRF
coronas. This could be because FIB is a line-like
protein and it was not densely packed on the
surface of AuNPs.
For all protein coronas on AuNP-PEG(2k) and
AuNP-PEG(5k) except BSA on AuNP-PEG(2k), no
protein corona was observed under TEM, matching
with DLS results very well. Note that the contrast of
PEG coating was low and it was hard to be
resolved.
Table 1 summarizes the microscopic dissociation
constant 'DK and Hill coefficient n for all measured
protein coronas in our experiments and some
values from references. All measured microscopic
dissociation constants were in the range of ~9-300
nM. And the Hill coefficient was larger than 1
except for BSA adsorption on citrate-AuNPs. The
values were similar to generally measured values
for protein-nanoparticle interaction[9,11,12,14]. For
example, 'DK and n for BSA adsorption on
citrate-AuNPs measured by fluorescence quenching
method[9] is roughly same as our results.
In conclusion, quantitative analysis has been done
for several serum proteins on AuNPs with different
surface modifications (citrate, thioglycolic acid,
cysteine and PEG). The experimental results have
revealed that (1) Surface modification with long
chain PEG (Mw=5k) can prevent protein adsorption;
(2) FIB tends to introduce aggregation of any AuNPs
not modified with PEG; (3) Surface modification
(citrate, carboxy and both carboxy and amine
modifications) have profound effects on protein
coronas.
Methods
Citrate stabilized AuNPs (40 nm, 9×1010/mL) were
purchased from BBI (England). Ligand exchange was
done at room temperature for 1 h at pH=7.4
[4-(2-hydroxyethyl)-1-piperazineethane-sulfonic acid
(HEPES) buffer, 5 mM]. The concentrations of
thioglycolic acid (product#528056, Sigma-Aldrich),
cysteine (product#W326305, Sigma-aldrich),
HS(CH2CH2O)nCH3 (Mw=2k) (Shanghai Seebio
Biotech) and HS(CH2CH2O)nCH3 (Mw=5k)
(Shanghai Seebio Biotech) used in ligand exchange
experiments were 100 μM. Dialysis (MD34, 8-14 kD,
Millipore) was conducted to remove excess ligands.
AuNPs were mixed with BSA, TRF or FIB solution at
room temperature for 30 min and then DLS
characterization was conducted. Final AuNP
concentration was 4.5×108/mL and HEPES buffer was
maintained at 5 mM (pH=7.4). DLS was conducted
on a Malvern zetasizer nano ZS at 25 oC. For a given
surface modification with a certain protein
concentration, three samples were measured and
each sample was measured at least for three times.
Cumulative model was used to fit DLS correlation
curve to get hydrodynamic diameter of nanoparticles.
AuNPs-protein solution (0.5 μM of proteins) was
drop-dried on copper grid and then stained with
uranyl acetate (Zhongjingkeyi Technology Co., Ltd.,
Part# GS02625, saturated aqueous solution) for TEM
imaging. TEM imaging was done on a FEI tecnai at
an operation voltage of 200 kV. UV-Vis was done on
a Lambda 950. All chemicals were purchased from
Sigma Aldrich unless otherwise specified. In all
experiments, DI water (>18 MΩ, 0.2 μm membrane
filtered, Millipore) was used.
Acknowledgements
This work was supported by 973 program (No.
2011CB932803).
Electronic Supplementary Material: Polydispersion
index (PDI) measured for all AuNP-proteins. References
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8
400 500 600 700 8000.0
0.1
0.2
0.3
Ab
so
rpti
on
(a
. u.)
Wavelength (nm)100 101 102 103 104 105
0.0
0.2
0.4
0.6
0.8
1.0 Citrate-AuNPs (dz=43nm)
AuNP-COO- (dz=43nm)
AuNP-Cys (dz=44nm)
AuNP-PEG(2k) (dz=45nm)
AuNP-PEG(5k) (dz=50nm)
g(2
) (
Lag time (s)
Citrate-AuNPs
AuNP-COO-
AuNP-Cys
32 36 40 44 480
20
40
60
Co
un
ts
Diameter (nm)
38.6±3.0 nm
a)
b)
c)
d) e)
100 nm
20 nm
Au Au
Citrate-AuNPs AuNP-COO-
Au
AuNP-Cys
HSCH2COOH
HSCH2CH(NH2)COOH(cysteine)
HSCH2CH2O)nCH3
Au
AuNP-PEG (Mw=2k, 5k)
S
O
n
CH3
AuNP-PEG(2k)
AuNP-PEG(5k)
Figure 1 (a) Typical TEM image of as-bought citrate-stabilized AuNPs. The inset shows an enlarged image. (b) Diameter distribution
of as-bought AuNPs measured by TEM. Totally 200 AuNPs were counted.(c) Schematic illustration of ligand exchange to prepare
AuNP-COO-, AuNP-Cys and AuNP-PEG (2k, 5k). (d) DLS correlation curves and (e) UV-Vis spectra of AuNPs with different
surface modifications.
9
1 10 100 10000.0
0.2
0.4
0.6
0.8
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0nM 5nM 50nM 500nM
Lag timeS
g(2) (
)-1
AuNP-PEG(5k)-BSA
1 10 100 10000.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7 0nM 5nM 50nM 500nM
Lag timeS
g(2
) ()-
1
AuNP-Cys-BSA
1 10 100 10000.0
0.2
0.4
0.6
0.8
1.0
0nM 5nM 50nM 500nM
Lag timeS
g(2
) ()-
1
AuNP-PEG(2k)-BSA
0.5 5 50 5005000
0
10
20
30
40
cBSA
(nM)
d
Z (
nm
)
1 10 100 10000.0
0.1
0.2
0.3
0.4
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0nM 5nM 50nM 500nM
g(2
) ()-
1
Lag timeS
AuNP-COO--BSA
0.5 5 50 5005000
0
10
20
dz (
nm)
cBSA
(nM)0.5 5 50 5005000
0
10
20
cBSA
(nM)
dz (
nm
)
=266±120 nMn=0.75±0.17
= 71±32 nMn=3.8±1.7
0.5 5 50 5005000
0
10
20
cBSA
(nM)
d z (
nm)
= 46±14 nMn=1.8±0.9
0.5 5 50 5005000
0
10
20
dz (
nm)
cBSA
(nM)
= 226±54 nMn=1.3±0.2
a) b) c) d)
1 10 100 10000.0
0.2
0.4
0.6
0.8
1.0
0nM 5nM 50nM 500nM
g(2) (
)-1
Lag times
Citate-AuNPs-BSA e)
Figure 2 DLS correlation curves and diameter changes of (a) citrate-AuNPs, (b) AuNP-COO-, (c) AuNP-Cys, (d) AuNP-PEG(2k)
and (e) AuNP-PEG(5k) at different BSA concentrations. 'DK and n in lower panels are fitting parameters using euqation 2 in the
maintext.
10
0.5 5 50 5005000
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10
20
dz (
nm)
cTRF
(nM)
1 10 100 10000.0
0.2
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0nM 5nM 50nM 500nM
Lag timeS
g(2) (
)-1
AuNP-PEG(2k)-TRF
0.5 5 50 5005000
0
10
20
cTRF
(nM)
d z
(nm
)
0.5 5 50 5005000
0
20
40
60
80
cTRF
(nM)
d z
(nm
)
0.5 5 50 5005000
0
10
20
cTRF
(nM)
dz
(nm
)
= 55±15 nMn=1.4±0.5
a) b) c) d)
= 9.5±3.6 nMn=1.3±0.5
= 150±28 nMn=3.4±1.1
e)
1 10 100 10000.0
0.2
0.4
0.6
0.8
1.0
0nM 5nM 50nM 500nM
Lag timeS
g(2) (
)-1
Citrate-AuNP-TRF
1 10 100 10000.0
0.2
0.4
0.6
0.8
1.0
0nM 5nM 50nM 500nM
Lag timeS
g(2) (
)-1
AuNP-COO--TRF
1 10 100 10000.0
0.2
0.4
0.6
0.8
1.0
0nM 50nM 100nM 500nM
Lag timeS
g(2) (
)-1
AuNP-Cys-TRF
1 10 100 10000.0
0.2
0.4
0.6
0.8
1.0
0nM 5nM 50nM 500nM
Lag timeS
g(2) (
)-1
AuNP-PEG(5k)-TRF
0.5 5 50 5005000
0
10
20
dz (
nm)
cTRF
(nM)
Figure 3 DLS correlation curves and diameter changes of (a) citrate-AuNPs, (b) AuNP-COO-, (c) AuNP-Cys, (d) AuNP-PEG(2k)
and (e) AuNP-PEG(5k) at different TRF concentrations. 'DK and n in lower panels are fitting parameters using euqation 2 in the
maintext.
11
0.5 5 50 5005000
-5
0
5
10
cFIB
(nM)
dz (
nm)
0.5 5 50 5005000
-5
0
5
10
cFIB
(nM)
dz (
nm
)
a) b) c) d) e)
100 101 102 103 104 1050.0
0.2
0.4
0.6
0.8
1.0
1.2
0nM 5nM 50nM 500nM
Lag timeS
g(2) (
)-1
Citate-AuNP-FIB
100 101 102 103 104 1050.0
0.2
0.4
0.6
0.8
1.0
1.2
0nM 5nM 50nM 500nM
Lag timeS
g(2) (
)-1
AuNP-COO--FIB
100 101 102 103 104 1050.0
0.2
0.4
0.6
0.8
1.0
0nM 5nM 50nM 500nM
Lag timeS
g(2) (
)-1
AuNP-Cys-FIB
1 10 100 10000.0
0.2
0.4
0.6
0.8
1.0
0nM 5nM 50nM 500nM
Lag timeS
g(2) (
)-1
AuNP-PEG(2k)-FIB
1 10 100 10000.0
0.2
0.4
0.6
0.8
1.0
0nM 5nM 50nM 500nM
Lag timeS
g(2) (
)-1
AuNP-PEG(5k)-FIB
0.5 5 50 5005000
0
200
400
600
cFIB
(nM)
dz (
nm)
0.5 5 50 50050000
500
1000
1500
cFIB
(nM)
dz (
nm)
0.5 5 50 5005000
0
100
200
300
400
cFIB
(nM)
dz (
nm
)
Aggregation Aggregation Aggregation
Figure 4 DLS correlation curves and diameter changes of (a) citrate-AuNPs, (b) AuNP-COO-, (c) AuNP-Cys, (d) AuNP-PEG(2k) and
(e) AuNP-PEG(5k) at different FIB concentrations. Lines in lower panels are guidance for the eyes.
12
AuNP-PEG(2k)-BSA
AuNP-PEG(5k)-TRF
AuNP-COO--BSAf) g) h)
20 nm 20 nm 20 nm
Citrate-AuNPs-BSA AuNP-Cys-BSA i) AuNP-PEG(5k)-BSA
20 nm
k) l) m)AuNP-COO--TRFCitrate-AuNPs-TRF AuNP-Cys-TRF n) o)AuNP-PEG(2k)-TRF
Citrate-AuNPs-FIB AuNP-PEG(2k)-FIB AuNP-PEG(5k)-FIBp) s) t)
20 nm
20 nm 20 nm 20 nm 20 nm20 nm
j)
q) AuNP-COO--FIB r) AuNP-Cys-FIB
20 nm 20 nm 20 nm 20 nm20 nm
Citrate-AuNPs AuNP-PEG(2k)AuNP-COO- AuNP-Cys AuNP-PEG(5k)a) b) c) d) e)
20 nm 20 nm 20 nm 20 nm20 nm
Figure 5 Typical TEM images of as-prepared AuNPs (a-e) and protein coronas on different AuNPs (f-t).
13
Table 1 Summary of measured microscopic dissociation constant 'DK and Hill coefficient n for BSA and TRF adsorption on
citrate-AuNPs, AuNP-COO- and AuNP-Cys.
BSA TRF FIB
'DK (nM) n '
DK (nM) n 'DK (nM) n
Citrate-AuNPs 266±120
Ref9: 301±51
Ref10: 2.56±0.50×105
Ref7: 2.0×103
0.75±0.17
Ref9: 0.81±0.03
Ref10: 0.4±0.1
55±15 1.4±0.5 -
(Aggregation)
-
AuNP-COO- 71±32 3.8±1.7 9.5±3.6 1.3±0.5 -
(Aggregation)
-
AuNP-Cys 46±14 1.8±0.9 150±28
(Aggregation)
3.4±1.1
-
(Aggregation)
-
AuNP-PEG(2k) 226±54 1.3±0.2 -
(no binding)
- -
(no binding)
-
AuNP-PEG(5k) -
(no binding)
-
-
(no binding)
-
-
(no binding)
-
Notes: In Ref. 9, human serum albumin (HSA) and AuNPs with 30nm diameter were used. In Ref. 10, AuNPs with 56nm diameter
were used and DLS was measured immediately after AuNPs and BSA mixing. In Ref. 7, AuNPs with 60nm diameter were used and
Langmuir model fitting was used (equal to n fixed at 1 in Hill equation.)