BSA-coated fluorescent organic-inorganic hybrid silica nanoparticles: preparation and drug delivery

Article abstract of DOI:10.1039/c6nj03915d

It is desirable to engineer bio-compatible construction materials and cargo release vehicles with efficient cargo loading capability and controlled drug delivery ability. Herein, an inorganic-organic hybrid composite DNDT&SiO₂-NH₂@BS

Full text of DOI:10.1039/c6nj03915d

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ISSN 1144-0546
PAPER
Jason B. Benedict et al.
The role of atropisomers on the photo-reactivity and fatigue of
diarylethene-based metal–organic frameworks
rsc.li/njc

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DOI: 10.1039/C6NJ03915D
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ARTICLE
BSA-Coated Fluorescent Organic-Inorganic Hybrid Silica
Nanoparticles: Preparation, and Drug Delivery
Zengming Yang, Hengchang Ma, Zijie Jin, Haiying Cao, Lei Lei, Yucheng Ma, Ziqiang Lei
Received 00th January 20xx,
Accepted 00th January 20xx
It is much desirable to engineering the cargo release vehicles with the efficient cargo loading capability, and the controlled
drug delivery ability, as well as the bio-compatible construction materials. Herein, an inorganic-organic hybrid composite
DNDT&SiO2-NH2@BSA was established by two steps. Technologically, the fluorescent DNDT was grafted on the particles
surface by solid phase synthesis, which was able to report the occurring of interactions between silica cores and proteins
of bovine serum albumin (BSA) by real-time optical change analysis. What should be noted that our construction method
derived from this work can be easily transposed to other surface modification procedures. Interestingly, DNDT&SiO2-
NH2@BSA could be dispersed into aqueous phase very well, leading to the homogeneous distribution of the drug over the
matrix with more efficient style. Furthermore, due to the temperature-dependent α-helix content changes, the
encapsulators of BSA can capture the drugs at low temperature, and release them with elevating temperature. Especially,
a desirable controlled release is realized at 37 oC.
DOI: 10.1039/x0xx00000x
www.rsc.org/
the clinic translation of the methods based on the
physiological changes-associated stimuli is often challenged by
the difficulty of a precise dose control in the complicated
1. Introduction
What happens by the interactions between biomolecules and
inorganic materials has attracted considerable attention,
which is of great importance in the research fields of bio-
nanotechnology,1-6 biocompatible materials synthesis, and
drug delivery.7-10 Over the past decade, extensive efforts have
been devoted to make understand the interaction mechanisms.
Thus, novel sustained/controlled drug delivery systems have
been developed.6,11-12 As usual, organic-inorganic hybrid
materials were widely employed as release vehicles, which was
due to the virtues of high delivery efficiency,13 low side-
effects,14 and low toxicity.13-16 However, a great challenge in
drug delivery system is to engineer the materials that can
efficiently encapsulate cargo at high concentration,17 and
controllably release the cargo at the target site.17-18 Not only
that much improvement in this field would be expected if
signals could be released when the encapsulation occurs. And
the long term release is also very desirable.19-22 Especially, it is
very desirable if controlled release could be realized at human
body temperature.20-21,23
physiological environment, while the external trigger-
mediated methods are limited by a need of additional
instrumentation. Thus, a wide number of materials have
emerged as drug delivery vehicles in nanomedicine, including
the mixtures of polymers and polymer-based composites.
Among of them, the hybrid nanosilica and synthetic polymers
has been demonstrated as convenient drug reservoir and
effective releaser.6,29-30 It is due to the part fact that the hard
nanosilica could provide architectural support for the soft
encapsulators, which significantly improves their physical
stability.31 However, these methods are of the disadvantage of
heterogeneity loading of samples due to the difficulty of
homogeneous distribution of the drug over the matrix, which
can affect the release rate between different samples.32 And
also, disputes are still remain because of the low
biocompatibility of the synthetic polymers.
The aim of this work is to explore the sensing property of the
functionalized nanosilica (Scheme 1) and the absorption
behaviors of protein of bovine serum albumin (BSA) on the
silica surface, both of them is of capability to act as a
convenient reservoir for controlled drug delivery. And also, we
develop an convenient optical analysis method to monitor the
interactions between nanosilica and the protein molecules. In
recent years, we have succeeded in creating a group of novel
triphenylamine (TPA) and tetraphenyl ethylene (TPE)-
containing fluoresecent molecules.33-37 These materials possess
a unique molecular structures, and the further applications
were extended. Herein, we decorate nanosilica particles with
dimethyl-3,3'-(((4-formylphenyl)azanediyl)bis(4,1-
Usually, drug delivery systems consisted of a polymeric matrix,
from which the drug was released under appropriate stimulus,
such as pH,24redox,25 ATP,26 glucose,27 and light.28 However,
Key Laboratory of Eco-Environment-Related Polymer Materials Ministry of
Education.
Key Laboratory of Polymer Materials of Gansu Province.
College of Chemistry and Chemical Engineering, Northwest Normal University,
Lanzhou, Gansu, 730070, China.E-mail:
mahczju@hotmail.com;leizq@nwnu.edu.cn.
Electronic
Supplementary
Information
(ESI)
available:.
See
DOI:10.1039/x0xx00000x
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phenylene))diacrylate (DNDT), which is emissive and very details of synthetic information can be found in Supporting
View Article Online
DOI: 10.1039/C6NJ03915D
sensitive to the external micro-environment changes. The Information. (Scheme S1).
resulted fluorescent nanosilica particles display very limited 2.3 Synthesis of dimethyl-3,3'-(((4-formylphenyl)azanediyl)bis(4,1-
dispersion ability in aqueous phase. However, a strong phenylene))diacrylate (Abbreviated as DNDT)
emissive and completely homogeneous aqueous solution
4-(bis(4-iodophenyl)amino)benzaldehyde (2.04 g, 4 mmol),
could be obtained if the protein molecules of BSA are
Methyl acrylate (MA, 1.03 g, 12 mmol, 3 equiv), Pd(OAc)2 (45
adsorbed on the surface of the nanosilica particles. During this
mg, 0.2 mmol, 0.05 equiv), Et3N (1.21 g, 12 mmol, 3 equiv) and
process, the florescent DNDT are able to report the occurring
1,3-bis(diphenylphosphino)propane (DPPP, 165 mg, 0.4 mmol,
of interactions between silica particles with BSA in real-time.
0.05 equiv) were added into 10 mL of dry dimethylformamide
What's more, in order to identify the naked and the
(DMF). After stirring for 24 h at 85 °C under N2 atmosphere.
enwrapped florescent nanosilica particles, picric acid (PA),
When the reaction was complete as determined by the
which is a electron deficient substance, is used as a probe to
disappearance of the 4-(bis(4-iodophenyl)amino)benzaldehyde,
investigate the adsorption behaviors of BSA on the silica
20 mL of water was charged, and the solution was extracted
particles surface. Due to the suppressed florescence quenching
with CH2Cl2 (3×10 mL). The organic phases were then dried
in the case of the enwrapped florescent nanosilica particles,
with anhydrous magnesium sulfate, filtered, and concentrated
we confirm that the protein molecules are really prefer to
under reduced pressure. The residue was purified by column
have an intimate interactions with nanoscale objects.
chromatography on silica gel and obtained a bright yellow
o
1
Therefore, after taking place of the interactions, the
hydrophobic silica disperses into aqueous media readily, which
supplies very convenient opportunity to capture the drugs by
totally homogeneous manners, and thus very uniform drug
loading could be distributed. Herein, we synthesize TPA-
BODIPY (TB) as drug model, which is a red fluorescent
molecule, and has large stokes shift.38 Finally, under the
stimulus of elevating temperatures, the drug release system is
established by the functionalized DNDT&SiO2-NH2@BSA as
cargo carriers, TPA-BODIPY as drug molecules.
solid (1.23 g, 3.26 mmol, 76.9% yield). M.P.: 133-137 C; H
NMR (400 MHz, CDCl3) δ 9.88 (s, 1H), 7.76 (d, J = 8.4 Hz, 1H),
7.66 (d, J = 16.0 Hz, 1H), 7.48 (d, J = 8.5 Hz, 1H), 7.15 (t, J = 8.1
Hz,1H), 6.38 (d, J = 16.0 Hz, 1H), 3.81 (s, 1H). 13C NMR (150
MHz, CDCl3) δ (ppm) 190.39, 167.37, 151.96, 147.67, 143.63,
131.31, 131.02, 130.79, 129.53, 125.36, 122.26, 117.17, 51.69.
MS (FAB): m/z = 441.16 [M+H]+.
2.4 Surface Modification of SiO2-NH2 Particles by DNDT
(Abbreviated as DNDT&SiO2-NH2)
Both of DNDT (150 mg) and SiO2-NH2 (1.5 g) was dispersed in
EtOH (50 mL) and placed into a 100 mL round bottom flask.
o
And then the mixture was refluxed at 80 C until the solution
become colorless. Then the green powders were separated by
centrifugation, and washed with EtOH (3 x 15 mL). Then it was
o
dried under vacuum at 70 C for 5 h to give obtained a light
green solid (1.5 g, yield: 91%). IR (KBr): 3788, 3453, 2923, 1627,
1594, 1109, 973, 805, 477 cm-1.
2.5 DLS Measurements
Particle size measurementsprocess were performed on a Zeta
sizer Nano ZS dynamic light scattering (DLS) system. This
system determines the particle size distribution of particles in
solution, with measurement capability from 0.3 nm to 10 μm.
2.6 Circular Dichroism
Scheme 1. The synthesis of DNDT decorated SiO2-NH2 nanoparticles.
2. Materials and methods
2.1 Materials
Circular Dichroism was measured using
a JASCO J805
Triphenylamine (TPA, 99%), phosphorus oxychloride (POCl3),
SiO2, surface area 300 m2/g，particle sizes 50-60 nm， density
1.9 g/cm3, potassiumiodide (KI, 99%), potassium iodate (KIO3,
99%), Bovine Serum Albumin (BSA, 98%), Picric acid (PA),
methylacrylate (MA, 98%), palladium acetate (Pd(OAc)2, 99%),
spectrometer. Each spectrum is presented as an average of
eight consecutive scans measured at 1 nm resolution. Different
temperature tests were finished after heating ten minutes
later. Bovine Serum Albumin (BSA) concentration: 3 x 10-7
(in water).
M
1,3-bis(diphenylphosphino)propane
(DPPP,
98%),
2.7 Immobilization of BSA on DNDT&SiO2-NH2 surface and Drug
Loading Method
triethylamine (Et3N, 99%) purchased from Aladdin Co. Other
commercial reagents were purchased from Aladdin Co. and
Energy Chemical Co. and used without further purification
unless otherwise stated.
DNDT&SiO2-NH2 (20 mg) and BSA (150 mg) dissolved into 10
mL deionized water. Then the mixture was stirred at room
temperature for 8 h to produce the BSA adsorbed DNDT&SiO2-
NH2 composites (DNDT&SiO2-NH2@BSA). Afterwards, 8.6 mg
TPA-BODIPY were added to the mixture，which was gently
stirred at room temperature for 3 h to obtain the transparent
and homogenous TPA-BODIPY loaded composites. the TB-
2.2 Synthesis of TPA-1, TPA-2, TPA-BODIPY
4-(diphenylamino)benzaldehyde
(TPA-1),
4-(bis(4-
iodophenyl)amino)benzaldehyde (TPA-2), TPA-BODIPY were
synthesized according to the published methods.39-41 The
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encapsulated DNDT&SiO2-NH2@BSA solution is concentrated
into pink-color powders by freeze drying method. We
calculated the drug loading concentration as [8.6
mg/(8.6+20+150) mg] = 4.8%.
View Article Online
DOI: 10.1039/C6NJ03915D
3. Results and discussion
3.1
DNDT,
DNDT&SiO2-NH2 synthesis
and
structural
characterization
DNDT is synthesized from TPA by three steps with acceptable
yield, which is light-yellow powder and very emissive in solid
state. (Figure 1) Structurally, DNDT is consisted of electron
donating TPA core and three electron accepting branches of
formyl and methyl acrylate groups as shown in Figure 1. As
reports declared that molecules containing both electron
donor and acceptor segments contribute to electronic
transition between the ground and excited states, which could
be manipulated by the induced charge transfer (CT) from
donor (D) to acceptor (A).41 This structural pattern endows
materials with more interesting optical behaviours when the
micro-environment changes.
Fig. 1 (A) The chemical structure of DNDT and the photographs of DNDT under room
light and UV light. (B) The optimized molecular orbital amplitude plots of HOMO and
LUMO energy levels of DNDT.
3.2 The optical properties of DNDT&SiO2-NH2
Due to the typical D-A pattern of DNDT, that exerts great
optical influence on the hybrid composite in different solvent.
The analysis results further demonstrated that DNDT&SiO2-
NH2 has obvious solvatochromism and well disperse ability in
common used organic solvents, such as EtOH, DMSO, DMF,
dichloromethane (DCM), and trichloromethane (TCM) et al at
concentration of 5 x 10-3 g/L. Clearly, the absorption spectra of
DNDT&SiO2-NH2 are almost similar toward different solvents.
(Figure S2A) This indicates that the solvent polarity has little
effect on its ground-state electronic transitions.41 In sharp
contrast, the PL spectrum of DNDT&SiO2-NH2 bathochromically
shifts with an increase in the solvent polarity. (Figure S2B) Its
Theoretical calculation using DFT//B3LYP/6-31G level in the
Gaussian 03 program is carried out to characterize the three-
dimensional structures and the frontier molecular orbital
energy levels of DNDT. As illustrated in Figure 1, DNDT shows
the three-dimensional propeller structure with a very narrow
energy gap of 0.12476 eV. The HOMO orbital is mostly
developed in the TPA core, and LUMO orbital mainly extends
across the three electron accepting branches, which indicates
that DNDT has obvious intramolecular charge transfer (ICT)
tendency.
As for DNDT, both of methyl acrylate groups not only act as
electron acceptors, but also give rise to the supramolecule
interactions between DNDTs. This soft interaction is probably
able to produce the aggregation induced optical
performance.41 Furthermore, -CHO group can apply
opportunities for DNDT to anchor on the -NH2 modificated
objects surface by the formation of C=N bond. Accordingly, we
prepared the γ-aminopropyl decorated nanosilica particles
(SiO2-NH2 NPs). Initially, SiO2-NH2 NPs disperse into EtOH, then
DNDT pours into the solution, leading to the formation of
green mixture. After refluxing the mixture for several hours,
light yellow powders are precipitated, and the solution
become colorless and transparent. That definitely confirms the
connections of SiO2-NH2 with DNDT. Finally, DNDT&SiO2-NH2 is
obtained by centrifugation and then washed by EtOH several
times. The resulted solid gave satisfactory analytical data that
corresponded to its molecular structure. The IR spectra of
DNDT&SiO2-NH2, and the precursors are shown in Figure S1.
The absorption band 1093 cm−1 in the spectrum of SiO2-NH2
and DNDT&SiO2-NH2 is stemmed from the Si-O-Si bond
stretching vibrations of nanosilica. A weak band located on the
1650 cm−1 verifies the presence of C=N bond in the sample of
DNDT&SiO2-NH2.

em shifts from 475 to 515 nm when the solvent is changed
from DCM to DMF. And the emission color changes from blue
in DCM to yellow in DMF when the DNDT&SiO2-NH2 solutions
are illuminated by 365 nm UV lamp. The PL intensity generally
decreases with increasing polarity of the solvent, showing
typical solvatochromic behavior or solvatokinetic effect.42 And,
the solvatochromism is caused by the photoinduced ICT in the
excited state.43
Additionally, we concerned that DNDT&SiO2-NH2 exhibits
better disperse ability than its precursor of SiO2-NH2 in organic
media. Reasonably, that is due to the presence of DNDT, which
enwraps on the nanosilica surface by chemical bonds.
Therefore, DNDT&SiO2-NH2 is even able to disperse well into
DCM and TCM at concentration of 5 x 10-3 g/L by ultrasound
wave. Especially, in the solvent of TCM, a very strong emission
band located at 475 nm could be observed, and the PL
intensity of maximum emission is high as almost 780-folds
than that of in EtOH. This interesting optical performance
inspires us to investigate the disperse property of DNDT&SiO2-
NH2 in different solvents. Meanwhile, dynamic light scattering
(DLS) was used to measure the hydrodynamic radius and
polydispersity of the DNDT&SiO2-NH2particles in the solvent of
TCM, DMF, and DMSO. Because of brownian motion of the
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nanoparticles, the intensity of scattered laser light fluctuates we
with time. The dynamic information can be retrieved by solvent(DMSO)/nonsolvent(H2O) mixtures following
examining the autocorrelation function g(q,τ) of the time- standard method.46 As shown in Figure S3, DNDT&SiO2-NH2 is
investigate
the
emission
behaviors
in
View Article Online
DOI: 10.1039/C6NJ039t1h5De
dependent intensity I(q,t):
highly emissive in DMSO. Addition of water into its DMSO
solution has suppressed its light emission. In 90% aqueous
mixture, the emission intensity is much lower than that in the
pure DMSO solution, exhibiting a quenched emission with the
maximum wavelength at 500 nm. Thus, we can summarize
that the higher the water content, the weaker the light
emission. That definitely confirms DNDT&SiO2-NH2 as a typical
ACQ-active fluorescent material. In order to further investigate
the self-assembling behaviors of DNDT&SiO2-NH2, its gel
formation ability is tested in several organic medias. Thanks for
the evident intermolecular interactions between DNDT&SiO2-
NH2, a very stable and emissive gel could be achieved in DMSO
as shown in Figure 3. That is even able to be stored at room
temperature for several days by inversion of the test tube
method. The critical gelation concentration (CGC) value is
determined as 1.35 wt% mL (gelator/solvent), and the phase
〈
〉
g(
〈
〉
A time correlation function G(q,τ) can be defined, which is
related to g(q, τ) by
For optically isotropic particles that are sufficiently diluted so
that interactions between particles can be neglected:
∑
Here, Γi is the rate of correlation decay, determined by the
translational diffusion coefficient DT of nanoparticles. DT is
related to the hydrodynamic radius RH by the Einstein−Stokes
law:
o
where kB is the Boltzmann constant, and ηs is the viscosity of
the solvent. Therefore, by determining the decay rate Γi and
the corresponding scattering power Gi, the size distribution of
DNDT&SiO2-NH2 particles can be determined.44-45 From the
determined results, we can see that the narrowest particle size
(143 nm) and the most uniform polydispersity (0.128) are
obtained in the solvent of DCM. However, in the cases of DMF
and DMSO, the particle size expands to 208 and 714 nm with
poly-diameter distributions. (Figure 2) Obviously, this solvent-
dependent disperse performance really corresponds to the
fluorescence behaviors of DNDT&SiO2-NH2 particles in
different solvents. And thus, a rough conclusion could be
drawn that more dispersive of the particles, and more emissive
of the composites DNDT&SiO2-NH2.
transfer temperature (Tg) could be maintained at 35 C. These
results strongly prove the successful fabrication of SiO2-NH2 by
DNDT, leading to the formation of the fluorescent DNDT&SiO2-
NH2 with self-assembling capability. The aggregation ability of
DTNT is also evidenced by H-H 2D NOESY spectrum (Figure 4).
As we reported that this correlation indicates the obvious
cross-peak signals between the protons in the C=C bond of
crylic.36
Fig. 3 Gel and sol states of DNDT&SiO2-NH2 under room light and UV lamp.
Fig. 2 Particle size distributions and the corresponding PL performances of DNDT&SiO2-
NH2 at different solvents.
For some fluorescence molecules, the physical aggregation
behaviors could induce the optical changes greatly, which is
named as aggregation-induced emissive (AIE) and aggregation-
caused quenching (ACQ).41 Accordingly, in our exploration
process, we have disclosed that the methyl acrylate groups are
able to provide the intermolecular force by C=O...π mode.36
Thus, to confirm AIE or ACQ property toward DNDT&SiO2-NH2,
Fig. 4H-H 2D NOESY NMR spectrum of DNDT in CDCl3.
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3.3 Immobilization of BSA on the surface of DNDT&SiO2-NH2
release ability toward the change of its surroundings. And also,
View Article Online
the signal release behavior verified the adDsOoI:r1p0t.i1o0n39t/aCk6iNnJg03p9la15cDe
at the silica surface. DNDT&SiO2-NH2 is a typical ACQ-active
material; its PL performance is mostly dependent on the
dispersion statues. Accordingly, we postulate that after coating
the BSA on the silica surface, DNDT&SiO2-NH2 particles are
isolated by the proteins further and further, and then, the ACQ
property is suppressed, leading to the enhanced emission. The
corresponding SEM analysis demonstrates totally different
morphology for the before and after coating. (Figure 6) In the
case of naked DNDT&SiO2-NH2, uniform spheres separately
scatter over the silicon wafer taking the size less than 100 nm.
In sharp contrast, the BSA coated DNDT&SiO2-NH2
(DNDT&SiO2-NH2@BSA) transforms into network-like shape.
Obviously, it was found that the coating really occurs due to
the disappearance of "hard" solid spheres, and also the
“protein corona” cross-links each other leading to the
formation of the more complicated net-works.
When NPs enter a biological medium, proteins from the
surrounding environment spontaneously adsorb at their
surface, forming a coating also called the “protein corona”.47
This coating can be dynamic and involve collective processes
and may vary significantly in different types of serum under
different conditions.48 Inspired from this nature of living-beings,
the successful therapeutic application has been focused on the
bio-mimicry related methodology.49 For representative
instance that the adsorption of amino acids or proteins on
silica surfaces has attracted considerable interest because the
“protein corona” has a broad range of applications in various
fields such as drug delivery.49 Proteins are often the best
choice in personal care, pharmaceuticals, and food preparation
because of their biocompatibility, and good nutritional value.
Against many synthetic polymers, proteins can also offer low
toxicity and reduced environmental impact in both personal
care and pharmaceuticals.50 Among of them, BSA is a major
protein constituent of bovine blood plasma which can bind to
various drug species as endogenous and exogenous ligands.51
3.4 Identify the naked and the enwrapped florescent nanosilica
particles by the probe of picric acid (PA)
Although the fluorescent nanoparticles has drawn
considerable research interest in the fields of chemistry,
materials, and biology, the efficient methods to monitoring the
modification, especially by more complicated bio-
macromolecules, on the surface of fluorescent nano-objects
are still limited.52 Picric acid (PA) is a health hazard as it can
cause skin/eye irritation and can affect the organs involved in
the respiratory system. Like many aromatic nitrated
compounds, it is an electron deficient substance with powerful
explosive and its explosive nature is equivalent to 105% of
trinitrotoluene (TNT).53 Thus, various fluorescent materials
have been developed as turn-off sensors for PA detection.54
Motivated by the response capability of fluorescent materials
to PA, we are interested in the development of a methodology,
which could be employed to identify the naked and the
enwrapped florescent nanosilica particles according to its
sensing activity toward PA. Initially, different concentrations of
PA ranging from 1x10-7 to 10-4 M charge into the solution of
DNDT&SiO2-NH2, then PL analysis is carried out to monitor the
optical changes. Obviously, the fluorescence quenching
Fig.
5 (A) Emission spectra of DNDT&SiO2-NH2 at different BSA concentrations.
(DNDT&SiO2-NH2 solution concentration: 5x10-2 g/L, ex = 370 nm) (B) photographs of
photographs of blank sample and the mixture of blank sample with different BSA under
365 nm UV lamp. (C) plots of maximum emission intensity (I/I0) and wavelength (em) of
DNDT&SiO2-NH2 versus with different BSA concentrations.
happens definitely.
A very low detection limited (DL)
determined as 2 PPb and a high selectivity to PA detection are
achieved. (Figure 7) That result confirms the presence of
evident interactions between the naked florescent nanosilica
particles with PA. Especially, over a group aromatic nitrated
compounds, the more efficient electron communication
occured only in the case PA, (Figure S7) demonstrating the
possibility of H-bond formation55 as shown in Figure 8.
Therefore, the stronger H-donating PA is of priority to connect
with the H-accepting oxygen atoms from carbonyl groups.
However, after coating by the biomolecules of BSA, the
quenching efficiency of DNDT&SiO2-NH2 can be almost
controlled compare to that of the naked DNDT&SiO2-NH2 when
keeping the PA concentrations from 10-7 to 10-4 M. (Figure 7C)
This result could be reasoned that the high affinity of the
proteins & PA excludes the interactions between DNDT&SiO2-
Fig. 6(A) TEM image of DNDT&SiO2-NH2 in EtOH and (B) SEM image of BSA coated
DNDT&SiO2-NH2in water.
In our research process, we prepared the BSA adsorbed
DNDT&SiO2-NH2 by simple mechanical stirring. What should be
noted, this coating process could be monitored by simple
fluorescence analysis. As shown in Figure 5, the PL intensity of
the coated solution has direct relationship to the loading
amount of BSA within the concentration range from 0.1 to 1.0
g/L. Clearly, the less emissive band narrows into a more sharp
peak at 480 nm with elevating the BSA concentration. That
confirmed the fact the DNDT&SiO2-NH2 is of sensitive signal
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NH2 with PA. And thus, we can conclude that "More close, isomeric forms for which BSA undergoesViewrAertvicelerOsinblinlee
DOI: 10.1039/C6NJ03915D
More quenching, and Less close, Less quenching". Finally, our conformational transitions. Each form is specifically
approach strongly supports the fact that the BSA are really characterized by α-helix content, the content value could be
prefer
to
have
an
intimate
interactions
with detected by Circular Dichroism spectroscopy (CD).57 We
silicondioxidenanoscale objects by the fluorescence sensing recorded the temperature-dependent CD profile of
method. Our conclusions derived from this work can be easily DNDT&SiO2-NH2@BSA as shown in Figure 9D. It was shown
transposed to other surface modification procedures.
that the characteristic CD patterns of α-helix progressively
fade along with elevating temperature. The α-helix content
decreases from 52.4% at 5 C to 32.1% at 73 C. Indicating BSA
conformations converse to extended form by the partial
impairment or breakage of intramolecular hydrogen bonds
within and between the helical structures.
o
o
Fig.
7
(A) Emission spectra of DNDT&SiO2-NH2 at different PA concentrations.
370 nm) (B)
(DNDT&SiO2-NH2 solution concentration: 5x10-3 g/L in EtOH, em
=
Photographs of blank sample and the mixture of blank sample with PA under room
light (top); under 365nm UV lamp (bottom) (C) The quenching efficiency comparison
between DNDT&SiO2-NH2 (blue bar) and BSA coated DNDT&SiO2-NH2 (red bar) with
different PA concentrations.
Fig. 9 (A) Emission spectra of the DNDT&SiO2-NH2@BSA with temperature increased
from 5 to 73 oC by a step size of 4 oC. (B) The relative PL intensity (I/I0) of DNDT&SiO2-
NH2@BSA at 490 nm under different temperatures. (Inset) Photographs of DNDT&SiO2-
NH2@BSA at 5 oC (left) and 73 oC (right) under UV lamp. (C) The I/I0 change profile
when DNDT&SiO2-NH2@BSA triggered by temperature within the window of 5 to 73 oC.
(D) Circular Dichroism for DNDT&SiO2-NH2@BSA at 5oC (black) and 73oC (red).
(DNDT&SiO2-NH2concentration: 5x10-2 g/L, BSA concentration: 1 g/L)
Herein, we have made a clear understand that DNDT&SiO2-
NH2@BSA is suffered from three important virtues for the
ideal drug vehicles, such as excellent water dispersibility,
biocompatibility, and temperature sensitivity. Then, we
determined TPA-BODIPY (TB) as the drug model, TB is of long
emission wavelength (565 nm) and large stocks shift (85 nm ),
also is an ACQ-active molecule.35 (Figure 10) The drug
encapsulating process is carried out as follows: after formation
the transparent and homogenous water mixture of
DNDT&SiO2-NH2@BSA; then TB is charged with gentle stirring
at room temperature for 5 hours, leading to produce totally
soluble mixture. What should be noted that the hydrophobic
TB is hardly dissolve into aqueous phase. However, due to the
presence of BSA, TB could be encapsulated uniformly with high
storage capacity through a rather complicated process, such as
hydrophobic and hydrogen bonding interactions.58 Afterwards,
the TB-encapsulated DNDT&SiO2-NH2@BSA solution is
concentrated into pink-color powders by freeze drying method,
which is then dispersed into aqueous phase. Finally, the
temperature-dependent PL analysis was conducted for the
dispersed aqueous solution (Figure 11). Notably, the peak at
570 nm, which is designated as TB's typical emission band,
whose intensity is decreased with the elevating temperature
Fig. 8 The interaction modes of the naked (left) and BSA-coated (right) DNDT&SiO2-NH2
with PA.
3.5 The temperature-sensitivity of DNDT&SiO2-NH2@BSA and
establishment of the cargo release mode
Depending on their molecular composition (primary structure)
and their conformational structure (secondary and tertiary
structures), proteins display not only different biological
activities, but also different physical properties under different
conditions.56 Therefore, after preparation of the stable
DNDT&SiO2-NH2@BSA samples, the temperature sensitivity is
valued. As shown in Figure 9, DNDT&SiO2-NH2@BSA exhibits
the temperature-dependent fluorescence varying within the
o
tested window from 5 to 73 C. Obviously, the higher of the
temperature, the lower of the fluorescence emission. And a
slight red-shift could be detected with elevating the
temperature. Furthermore, the fluorescence behavior can be
totally reversible when switching the temperature buttons of 5
o
and 73 C. (Figure 9C) Due to the fact that no optical response
can be detected in the case of DNDT&SiO2-NH2when
temperature changing, we found that the reversible
fluorescence emission and decay of DNDT&SiO2-NH2@BSA
mainly attributes to the adsorption-desorption behaviors of
BSA on the silica surface.57 Meanwhile, the effect of
temperature on BSA structure is declared by changes in
o
from 0 to 70 C. That quenching behaviors was attributed to
the ACQ-property of TB. Clearly, after releasing them from the
temperature-sensitive vehicles of DNDT&SiO2-NH2@BSA, TB
molecules prefer to form the aggregated objects, therefore,
6 | J. Name., 2012, 00, 1-3
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New Journal of Chemistry
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Journal Name
ARTICLE
the quenched emission occurs. As we discussed above that the NH2surfaces was processing. The well establishedVDiewNADrtTic&le SOinOlin2e-
DOI: 10.1039/C6NJ03915D
long term drug release is also very desirable. Especially, if NH2@BSA is water dispersible, which is very helpful for the
o
controlled release could be realized at 37 C. And then, we uniform and high concentration cargo loading. After
carried out the release performance at the fixed temperature encapsulating the drug mode of TB, the temperature triggered
o
of 37 C. Fortunately, as shown in Figure 12, the TB can be delivery property of DNDT&SiO2-NH2@BSA was valued by two
released for long term style. And after 8 hs, a reversible aspects, and the desirable results were achieved. One is the
equilibrium of the cargo releasing and up taking by vehicles release performance under temperature elevating from 0 to
o
was established, and the change profile of PL intensity of TB 70 C; another aspect is the controlled delivery at the fixed
has a slight decrease after 8 hs.
temperature of 37 oC. Thus, our findings suggested that the
DNDT&SiO2-NH2@BSA not only successfully encapsulate and
deliver drugs in aqueous phase in controlled manner, but they
also provide a subtle mechanism for monitoring the drug
vehicle engineering, and vehicle fabrication due to the
fluorescent nature of DNDT&SiO2-NH2.
Acknowledgements
This work is supported by the National Natural Science
Foundation of China (nos. 21174114, and 21361023). We
thank the Ministry of Education Scholars Innovation Team (IRT
1177) for financial support. We also thank the Analytical and
Testing Center of Northwest Normal University for related
analysis.
Fig.10 The chemical structure of TB and the photographs under room light and UV light.
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DOI: 10.1039/C6NJ03915D
Graphic abstract
A novel BSA-coated inorganic-organic hybrid nano-materials with drug delivery ability
under stimulating by temperature changes.