Molecular Scaffolds as Double-Targeting Agents For the Diagnosis and Treatment of Neuroblastoma

Article abstract of DOI:10.1002/anie.201811691

The selective delivery of therapeutic and imaging agents to tumoral cells has been postulated as one of the most important challenges in the nanomedicine field. Meta-iodobenzilguanidine (MIBG) is widely used for the diagnosis of neuroblastoma (NB) due to its strong affinity for the norepinephrine transporter (NET), usually overexpressed on the membrane of malignant cells. Herein, a family of novel Y-shaped scaffolds has been synthesized, which have structural analogues of MIBG covalently attached at each end of the Y-structure. The cellular uptake capacity of these double-targeting ligands has been evaluated in vitro and in vivo, yielding one specific Y-shaped structure that is able to be engulfed by the malignant cells, and accumulates in the tumoral tissue, at significantly higher levels than the structure containing only one single targeting agent. This Y-shaped ligand can provide a powerful tool for the current treatment and diagnosis of this disease.

Full text of DOI:10.1002/anie.201811691

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Accepted Article
Title: Molecular scaffolds as double targeting agents for the diagnosis
and treatment of Neuroblastoma.
Authors: Gonzalo Villaverde, Arantzazu Alfranca, África Gonzalez-
Murillo, Gustavo J. Melen, Rafael R. Castillo, Manuel
Ramírez, Alejandro Baeza, and Maria Vallet-Regi
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To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201811691
Angew. Chem. 10.1002/ange.201811691
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Molecular scaffolds as double targeting agents for the diagnosis
and treatment of Neuroblastoma.
Gonzalo Villaverde,[a] Arantzazu Alfranca,[b], [c] África Gonzalez-Murillo,[c], [d] Gustavo J. Melen, [c], [d]
Rafael R. Castillo,[a] Manuel Ramírez,* [c], [d] Alejandro Baeza, * [a],[e] and María Vallet-Regí.*[a]
Abstract: The selective delivery of therapeutic and imaging agents
to tumoral cells has been postulated as some of the most important
challenges in nanomedicine field. The cellular selectivity of
nanocarriers is usually achieved by their surface decoration with
targeting moieties able to recognize these cells in a specific manner.
Neuroblastoma (NB) is the most frequent extra-cranial pedriatic
tumor, almost incurable at advanced stages. Meta-iodo-
benzilguanidine (MIBG) is widely used for the diagnosis of this
disease due to its strong affinity by the norepinephrine transporter
(NET) usually overexpressed on the membrane of the malignant
cells. Herein, a complete family of novel Y-shaped scaffolds which
contains structural MIBG analogues covalently attached in each end
of the Y-structure has been synthesized. The enhanced cellular
uptake capacities of these double-targeting ligands have been
evaluated in vitro and in vivo yielding one specific Y-shape structure
which presents capacity to be engulfed by the malignant cells and be
accumulated in the tumoral tissue, significantly higher than the
structure which contains only one single targeting agent. This Y-
shaped ligand can provide a powerful tool for the current and
treatment diagnosis of this disease.
agents.[2] Despite this multimodal treatment, up to 60% of
children with stage IV of NB relapse. Thus, the prognosis of
advanced NB is very poor, which demonstrates the inability of
the current treatment to eradicate the entire disease. NB cells
come from the neural crest, such as precursors of the
sympathetic nervous system. Around 95% of NB cells present
an overexpression of the transmembrane protein norepinephrine
transporter (NET) being able of capturing norepinephrine
precursors. The synthetic norepinephrine analogue meta-
iodobenzylguanidine (MIBG) selectively binds to NET receptor
and for this reason, it is widely used for the diagnosis of NB
when the molecule is labeled with a radioactive iodine.[3],[4][5]
Several structure/activity relationship (SAR) studies have
demonstrated that benzene ring and guanidine moiety are the
pillars for maintaining the NET binding capacity of MIBG. Thus,
the rest of the structure admits some degree of modification
such as substitution of the iodine for other group with different
electro-donor / attractor character. Further, changes in the
position of the substitution and even replacing the aromatic ring
itself have been carried out for improving both, cell uptake and
tumor tissue accumulation.[6-10] However, the in vivo assays did
not yield the expected results, being the MIBG the most active.
Even, the incorporation of a second guanidine group in position
4 led to a significant decrease in the internalization in NB
cells.[11] Until now, only the incorporation of a methyl group in
position 4 improves the retention of this molecule by the NB
cells.[7–9,11] The MIBG analogue which contains an amino group
instead of the iodine, meta-aminobenzylguanidine (MABG), has
shown similar NET binding ability that MIBG. For this reason,
Neuroblastoma (NB) is the most common extra-cranial solid
tumor in childhood. The 50% of the cases are diagnosed at late
stages when the disease has spread throughout the entire body,
in metastatic stage.[1] The treatment of metastatic NB (stage IV)
is usually based on the combination of various
chemotherapeutic agents in high doses, together with surgical
removal of the primary tumor, only in cases of a good response
to the initial chemotherapy. Finally, the treatment is completed
with radiotherapy, or complementation of the initial
chemotherapy with autologous for hematopoietic rescue and
pre-treatment of possible residual disease with differentiating
MABG was
conjugated to non-radioactive fluorescence
compounds in the near infrared by organic spacers acting as
image agent,[12] resulting an excellent vectorization agent that
yields improved spatial imaging resolution in comparison to that
obtained by SPECT. Furthermore, we previously employed
MABG as targeting moiety for guiding nanoparticles specifically
to neuroblastoma in murine models.[13] In this work, MABG was
anchored on the surface of mesoporous silica nanoparticles
(MSN) through a polyethylene glycol polymer (PEG) of 2000 Da
of molecular weight which acted as spacer between the
nanoparticle surface and the recognition moiety. The presence
of this targeting group enhanced the nanoparticle uptake in NB
cell around 4-fold. Additionally, it was found that the presence of
this targeting group on the nanoparticle surface, led
[a]
Prof. María Vallet-Regí and Dr. Alejandro Baeza
Dpto. Química en Ciencias Farmacéuticas. Facultad de Farmacia,
Universidad Complutense de Madrid. Plaza Ramon y Cajal s/n.
Instituto de Investigación Sanitaria Hospital 12 de Octubre i+12 ¡
Centro de Investigación Biomédica en Red de Bioingeniería,
Biomateriales y Nanomedicina (CIBER-BBN)
Madrid, Spain
E-mail: vallet@ucm.es; abaezaga@ucm.es
[b]
[c]
Servicio de Inmunología. Hospital Universitario de La Princesa.
Instituto de Investigacion Sanitaria La Princesa. Diego de León, 62.
28006 Madrid, Spain.
[d]
Dr. Manuel Ramírez, Dr. Gustavo Melen, Dr. Africa Gonzalez-
Murillo. Servicio de Hematología y Oncología Pediátrica, Hospital
Infantil Universitario Niño Jesús, Madrid, Spain.
Supporting information for this article is given via a link at the end of
the document.
[e]
Dpto. Materiales y Producción Aeroespacial, ETSI Aeronáutica y del
Espacio, Universidad Politécnica de Madrid, 28040-Madrid, Spain.
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Figure 1. Fluorescein PEGylated analogues for in vitro analysis from all families of single and double targeting system. X1 and X2 = amide bond in all cases.
(fluorescein (ƛex = 492 nm; ƛem= 520 nm). Thus, the marked
to
a
selective accumulation and high retention of the
single derivates, F-PEG-S3, (m-glycinamido-benzylguanidine),
F-PEG-S4 (p-glycinamido-benzylguanidine), F-PEG-SCl (p-
nanocarriers in the tumoral mass of a xenograft mice model
whereas untargeted to the rapid excretion of the nanoparticles.
This approach is based on the use of one single targeting agent
which interacts with a membrane cell receptor overexpressed in
the tumoral cells. Nature usually employs antibodies as
recognition agents and these proteins present a Y-shaped
structure able to bind to the antigens by two points instead of
one.[14] Inspired by these natural molecules, the following two
questions were raised to the authors; synthetic Y-shaped
scaffold which contains two MABG-based binding points could
improve even more the cellular uptake within NB cells?, and the
second question related to this first one, which is the optimal Y-
structure that yielded the best NET-binding capacities? The
present work describes the synthesis and biological evaluation
chloro-m-glycinamido-benzylguanidine
) and F-PEG-SI, (p-
glycinamido-m-iodo-benzylguanidine) ) were synthetized from
the corresponding compounds with terminal primary alkyl amine
group proportioned by glycine coupling. (See Supporting
information (SI) from Scheme S1 to Scheme S5). The cellular
uptake of these conjugates was evaluated in the NB cell line
(NB1691-luc). Cells were incubated for 2 hours with each of
these conjugates at 50 μg·mL-1 in culture medium, washed once
with PBS and the well refilled with fresh medium. Finally, cells
were incubated overnight and washed with PBS for removing
the non-incorporated conjugate. The cellular uptake was
measured by flow cytometry showing that the introduction of
halogens in the benzyl ring yielded lower internalization capacity
of different Y-shaped scaffolds decorated with MABG analogues, whereas the system which presents only one amide group (both
and also with other usually employed targeting moieties, for the
look out of improved vectorization agents which allow the
therapeutic / imaging targeted delivery to neuroblastoma.[15] This
Y shape promising prototype could pave the way of a safer
delivery of chemotherapy and also for a more sensitive and
efficient diagnosis of NB lesions. Previous to the construction
of Y-shape moieties, we decided to synthesize a small collection
of MABG-based derivatives in order to select the analogue
which yielded the higher cellular uptake in NB. These
experiments will be essential in order to choose the best
candidate for its introduction in the Y shape scaffold. Thus,
different MABG analogues which carry halogens attached to the
benzyl ring or with the amide group in meta- or para- position
were synthesized. Then, these molecules were conjugated with
a fluorescein-labeled polyethylene glycol (PEG) chain of 3500
Da of molecular weight (Figure 1) The PEGylated fluorescein
acts as fluorescent marker payload emulation which makes
possible their tracing on in vitro assays by flow cytometry
in meta- and para- position) achieved the best results. After 2
hours of incubation with the corresponding analogue the para-
amide substituted compound (S4) showed the best performance
with 75% of cells with fluorescence inside, versus the barely
50 % obtained by the meta- analogue (S3). Thus, para- and
meta-amino derivatives were selected as the best systems to be
incorporated in the Y-shaped structures. As a first approximation
for doubling the uptake properties of the MAGB analogues,
flexible medium length amino acid Y-shape scaffold (DF) was
chosen as initial candidate to combine the benzylguanidine
analogues to each other. On the other hand, other motives, were
also tested in combination with the MABG analogues in the DF
scaffold. DF structure is based on a two Lysine units connected
by a peptidic bond. Both targeting agents were connected to the
scaffold by amidation of the primary amine groups. For this aim
succinic derivative of S3 and S4 were synthetized previously (SI,
Scheme S6) in order to afford DF3 and DF4. Besides these
systems, DFS3-TPP and DFS3-RGD were also synthetized.
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DFS3-TPP was designed with the two unit peptide scaffold
internalization in NB cells, were carried out by screening the
connecting the succinic S3 analogue and triphenilphosphine unit, PEGylated and fluorescein marked analogues for each family at
that present vectorization to the mitochondria.[16],[17],[18] On the
other hand, DFS3-RGD, was constructed with the same
structure changing the motif for the tripeptide RGD trying to
combine two different tumoral receptors that will be present in
the NB tumor endothelium and cell membrane.[19] (See SI
Scheme S12 and S13). In all cases the system have a primary
amine group as exclusive anchoring point to link with the pre-
activated acid group from PEG, which connected to the
corresponding payload. Similar to the mentioned analogues, a
fluorescent moiety was anchored for following the system in in
vitro experiments (F-PEG-DFX). Figure S7 from SI shows how
double systems DF3 and DF4 present more than 90 % of
cellular uptake at 50 µg.mL-1and even at 25 µg.mL-1. Following
the tendency, the single S4 showed an excellent results with a
75 %, leading the rest of single ligands which presented an
average of 50 % of internalization at the higher concentration.
The behavior of the double systems DF3-TPP and DF3-RGD,
with a notable decrease of internalization versus the double DF3
and DF4, even worse than the single agents S3 and S4, showed
that the introduction of nonspecific moieties in the system could
interfere with the binding properties of the benzylguanidine
group and into the recognition process with the NET. These data
made the authors to stake out the final aim of the work and
focus their efforts on obtaining the best benzylguanidine based
Y shape multivalent ligand applicable as vectorization agent for
NB. For this aim, studies about the influence of the length and
flexibility of the scaffold on their uptake properties were carried
out for the following F-PEGylated double ligands families
classified according with their rigid or flexible nature and their
length (Figure 1 and Figure 2 a): Double rigid (DR3, DR4),
Double flexible small (DFS3, DFS4), Double flexible (DF3, DF4),
and double flexible large (DFL3, and DFL4).
Double Rigid scaffolds (DR) are based on aromatic core body.
They were synthetized by amide formation coupling reaction
with same starting material described for single analogues
connecting two units of S3 and S4 with terminal alkyl amine
group with isophthalic acid analogue for affording the
homogeneous DR3 and DR4, respectively. (See SI Scheme S7
and S8). Double Flexible ligands (DF) are based on the
presence of an oligopeptidic chain. Among this group, three
different types of flexible structures were synthesized according
with their lengths, presenting one, two and up to three amino
acids, DFS, DF, DFL, respectively. Briefly, these DF analogues
were synthesized by coupling amidebezylguanidine analogues
in meta- and para- conformation (S3 and S4) through a peptide
chain, affording DFS3 and DFS4, with one amino acid in the
structure, DF3 and DF4 with two amino acids, and DFL3 and
DFL4, with three amino acids conferring more flexibility and
distance between the binding points with the increase of units in
the scaffold structure. DF ligands were synthetized through
typical solid phase peptide synthesis, by conventional Fmoc
deprotection/HOBT-based acid activation coupling starting from
Fmoc-NH-Lys-NH-Mtt Wang resin. The rest of amino acids, as
well as the targeting agents previously synthetized in this case
with terminal carboxylic acid group proportioned by succinic acid
coupling with the corresponding initial analogue S3 and S4 (See
SI from Scheme S9 to S11 and Scheme S6), were consecutively
coupled. Finally, the complete systems were released from the
resin by the addition of TFA cocktail. In vitro experiments for
12.5 µg/ml and 6.5 µg/ml following conditions previously
described. The analogues analyzed were: S3 and S4, as
references, plus, rigid ligands DR3 and DR4, and finally from
flexible scaffolds, DFS3, DFS4, DF3, DF4 and both DFL3 and
DFL4.
Figure 2. a) Calculated distance by molecular mechanics (MM2) calculations
between recognition spots in the double scaffolds structures DR4 (7 Å), DFS4
(4 Å), DF4 (8 Å) and DFL4 (16.9 Å), NOTE: The distances are equivalent in
the case of meta-substituted systems b) Initial screening of single (S3 and S4)
versus double ligands for uptake in NB cells at low concentrations, 12.5
µg.mL-1 (blue) and 6.25 µg.mL-1 (red).
As Figure 2. b shows, the act of doubling the number of
targeting moieties did not govern the entire uptake process.
Moreover instead of number of targeting agent, their disposition,
their distance to each other and their freedom to adopt cluster
configuration in their interaction with the receptor in the cell
membrane seemed determinant. Thus, the effect of the structure
and length of the scaffold has a dominant effect in order to
interact with the NET of the NB cell membrane. Taking as an
example the data for the meta-derivate, double rigid scaffold
DR3 improved the internalization properties in front of its
corresponding single counterpart S3 barely at same scale to
flexible analogues DF3. This equal behavior may be explained
by the duplication of the interaction points with NET in both
analogues, further they present equal distance between
recognition points following MM2 calculations (DR3 (7 Å), DF7
(8 Å)) . Thus, in this case, the effect in the uptake process is
governed by the duplication of targeting agent. On the other
hand, the larger and more flexible analogue, DFL3 (16 Å, of
distance between recognition points)), resulted significantly the
more efficient in the uptake process compared to S3 and the
rest of the ligands in the family. Thus, the fact of having two
benzyl guanidine derivate in the same system sharpens when
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Figure 3. a) Upper panel, Graphic shows relative fluorescent signal (tumor area/whole mouse) obtained from xenograft neuroblastoma-inoculated mice 72h after
injection with either NP-NH2, NP-PEG-DFL3, or NP-PEG-DFL4 (mean+SD; n=3-5 per group); lower panel b) Representative photographs of xenograft mice
treated as in a), showing luminescent tumor signal (upper panels) and fluorescent nanoparticle signal (lower panels)
the distance between the recognition moieties is the barely three
amino acids and the system is flexible.
Previous results of our group have shown that MSN´s are highly
efficient nanotransporters for drug delivery, due to their optimal
loading and controlled release properties. Additionally, MSN´s
may be easily functionalized for adding vectorization agents.[20–
22]. Cy7 is a near infrared marker frequently used for in vivo
assays, given the reduced tissue auto fluorescence at this
wavelength. This characteristic makes Cy7 a suitable candidate
to label the nano-transporters for their in vivo evaluation. We
carried out functionalization of the agents to the nanoparticle´s
surface through a PEG linker; PEG confers more ability in
dispersion and helps to abolish the opsonization process which
may prolong circulation time in the blood stream.[23] We
subcutaneously implanted human neuroblastoma NB1691-luc
cells (2x106 cells/mouse) into the flank of immuno-deficient NGS
mice (NOD/SCID deficient in the common gamma chain). These
cells constitutively express Luciferase, which allows in vivo
monitoring of tumor growth by bioluminescence quantification
upon injection of Luciferase substrate Luciferin (1,25 mg/mouse).
Thus, three weeks after cell inoculation we assessed tumor
development in mice, and sorted mice into three groups with a
homogeneous distribution of tumor size among them (3-5
specimens per group (see Figures S9 and S10 in SI). Mice
received intravenous injections of 1 mg of NP-NH2, NP-PEG-
DFL3, or NP-PEG-DFL4 in 0.2 mL of saline solution. In order to
evaluate system accumulation in the tumor mass in each case,
we quantified fluorescent signal ratio of Cy7 in tumor area vs.
the whole mouse, at 72 hours after system administration. As
shown in Figure 3, we observed preferential accumulation of
Para analogues from Figure 2a kept a similar behavior, when
the distance is about 16.9 Angstrom (DFL4) the internalization
folds up around 3 times versus their double more rigid (DR4)
and flexible shorter families (DF and DFS) counterparts. This
fact gave light for understanding the behavior of the targeting
ligand. The distance and the flexibility of the ligand allow the
system to work such as, common bio- receptor with double
anchoring point, and if the distant and flexibility of the ligand is
not appropriate the double ligand works such as single targeting
agent interacting with only one of the recognitions points present
in the scaffold. Thus, comparing the uptake properties of the
best bi-functional system (DFL4) with the best mono-functional
(S4) we can conclude that for 100 % of internalization in NB cell,
DFL4 analogue needs 10 times less concentration than S4.
Once known the behavior in terms of cell uptake, the next step
to corroborate the characteristics of these systems, was to study
the selective transporting and accumulation of significate
payload (drugs, nanoparticles or even image agents) to the
neuroblastoma tumoral environment. To achieve this goal, we
conducted in vivo experiments to compare ligands with the best
performance in vitro (i.e. DFL3 and DFL4) versus a non-targeted
system. To this end, mesoporous silica nanoparticles (MSN´s)
marked with Cy7 were synthetized and surface-functionalized
with the corresponding vectorization agents, through a PEG
linker chain affording the control naked material NP-NH2 and the
targeted nanoparticles NP-PEG-DFL3 and NP-PEG-DFL4.
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targeted MSN´s systems (NP-PEG-DFL3 and NP-PEG-DFL4) in
tumor mass, which was detected by bioluminiscence. In
conclusion, this work has allowed the selection of a novel
system based on a Y-shape multivalent double ligand targeting
for NB with a specific composition and length . Their behavior in
terms of selectivity and efficacy for improving cell internalization
and in vivo accumulation in neuroblastoma xenografts have
been evaluated. These new Y-shape double system presents a
substantial improvement in cell uptake in vitro, 20-times higher
than the single-targeted system and an effective accumulation in
tumor mass in vivo. Further, they are easily tunable for using as
versatile targeting system for drug delivery in conjugates or
nano-transporters, as well as for imaging agents. Our findings
may pave the way for rising the efficacy against NB in terms of
diagnosis or treatment.
[5]
A. Schlessinger, E. Geier, H. Fan, J. J. Irwin, B. K. Shoichet, K. M.
Giacomini, A. Sali, Proc. Natl. Acad. Sci. U. S. A. 2011, 108, 15810–
5.
[6]
[7]
D. Hadrich, F. Berthold, E. Steckhan, H. Bönisch, J. Med. Chem.
1999, 42, 3101–8.
G. Vaidyanathan, S. Shankar, D. J. Affleck, P. C. Welsh, S. K. Slade,
M. R. Zalutsky, 2001, 798–806.
[8]
[9]
G. Vaidyanathan, S. Shankar, M. R. Zalutsky, 2001, 786–797.
G. Vaidyanathan, P. C. Welsh, K. C. Vitorello, S. Snyder, H. S.
Friedman, M. R. Zalutsky, Eur. J. Nucl. Med. Mol. Imaging 2004, 31,
1362–70.
[10]
[11]
K. A. Streby, N. Shah, M. A. Ranalli, A. Kunkler, T. P. Cripe, Pediatr.
Blood Cancer 2015, 62, 5–11.
G. Vaidyanathan, S. Shankar, D. J. Affleck, K. Alston, J. Norman, P.
Welsh, H. LeGrand, M. R. Zalutsky, Bioorg. Med. Chem. 2004, 12,
1649–56.
[12]
[13]
W. Wang, J. Shohet, M. Mawad, S. Ke, Non-Radioactive Agents for
Neuroblastoma Imaging, 2011.
Acknowledgements
G. Villaverde, A. Baeza, G. J. Melen, A. Alfranca, M. Ramirez, M.
Vallet-Regí, J. Mater. Chem. B 2015, 3, 4831–4842.
T. Quynh, N. Nguyen, K. W. Lim, A. T. Phan, 2017, 33, 1–7.
V. J. Yao, S. D. Angelo, K. S. Butler, C. Theron, T. L. Smith, S.
Marchiò, J. G. Gelovani, R. L. Sidman, A. S. Dobroff, C. J. Brinker,
et al., J. Control. Release 2016, 240, 267–286.
G.-F. Luo, W.-H. Chen, Y. Liu, Q. Lei, R.-X. Zhuo, X.-Z. Zhang, Sci.
MVR thank the funding from the European Research Council
through the Advanced Grant VERDI (ERC-2015 AdG proposal
no. 694160) and Asociación NEN. Financial support from
Ministerio de Economía y Competitividad, (MEC), Spain (Project
MAT2015-64831-R) is gratefully acknowledged. AA is supported
by grant FIS PI15/01491. MR is supported by Asociación NEN,
Asociación Pablo Ugarte and Fundación Neuroblastoma.
[14]
[15]
[16]
[17]
Rep. 2014, 4, 1–10.
B. H. Kang, J. Plescia, H. Y. Song, M. Meli, G. Colombo, K. Beebe,
B. Scroggins, L. Neckers, D. C. Altieri, J. Clin Invest. 2009; 119(3), 454-
464.
Keywords: neuroblastoma • nanomedicine • targeting • meta-
[18]
[19]
[20]
W.-H. Chen, X.-D. Xu, G.-F. Luo, H.-Z. Jia, Q. Lei, S.-X. Cheng, R.-
X. Zhuo, X.-Z. Zhang, Sci. Rep. 2013, 3, 3468.
E. V Rosca, J. M. Stukel, R. J. Gillies, J. Vagner, M. R. Caplan,
2007, 3830–3835.
iodobenzylguanidine • molecular scaffold
[1]
[2]
J. M. Maris, N. Engl. J. Med. 2010, 362, 2202–2211.
N. R. Pinto, M. A. Applebaum, S. L. Volchenboum, K. K. Matthay, W.
B. London, P. F. Ambros, A. Nakagawara, F. Berthold, G.
Schleiermacher, J. R. Park, et al., 2015, 33, DOI
10.1200/JCO.2014.59.4648.
M. Vallet-Regi, A. Rámila, R. P. del Real, J. Pérez-Pariente, Chem.
Mater. 2001, 13, 308–311.
[21]
[22]
M. Vallet-Regí, E. Ruiz-Hernández, Adv. Mater. 2011, 23, 5177–218.
A. Baeza, M. Colilla, M. Vallet-Regí, Expert Opin. Drug Deliv. 2014,
1–19.
[3]
[4]
N. Tumors, S. Carlin, R. J. Mairs, A. G. Mccluskey, D. A. Tweddle, A.
Sprigg, C. Estlin, J. Board, R. E. George, C. Ellershaw, et al., 2003,
9, 3338–3344.
[23]
H. Meng, M. Liong, T. Xia, Z. Li, Z. Ji, J. I. Zink, A. E. Nel, ACS
Nano 2010, 4, 4539–50.
K. K. Matthay, R. E. George, A. L. Yu, Clin. Cancer Res. 2012, 18,
2740–53.
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