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Synthesis, characterization, and biological activity of cationic ruthenium-arene complexes with sulfur ligands.
JBIC Journal of Biological Inorganic Chemistry (2024) 29:331–338
https://doi.org/10.1007/s00775-024-02054-0
ORIGINAL PAPER
Potential antiprostatic performance of novel lanthanide‑complexes
based on 5‑nitropicolinic acid
Amalia García‑García1 · Pablo Cristobal‑Cueto2 · Tania Hidalgo2 · Iñigo J. Vitórica‑Yrezábal1 ·
Antonio Rodríguez‑Diéguez1 · Patricia Horcajada2 · Sara Rojas1
Received: 17 November 2023 / Accepted: 20 February 2024 / Published online: 8 May 2024
© The Author(s) 2024
Abstract
Two new lanthanide-complexes based on the 5-nitropicolinate ligand (5-npic) were obtained and fully characterized. Singlecrystal X-ray diffraction revealed that these compounds are isostructural to a Dy-complex, previously published by us,
based on dinuclear monomers link together with an extended hydrogen bond network, providing a final chemical formula
of [Ln2(5-npic)6(H2O)4]·(H2O)2, where Ln = Dy (1), Gd (2), and Tb (3). Preliminary photoluminescent studies exhibited a
ligand-centered emission for all complexes. The potential antitumoral activity of these materials was assayed in a prostatic
cancer cell line (PC-3; the 2nd most common male cancerous disease), showing a significant anticancer activity (50–60%
at 500 μg·mL−1). In turn, a high biocompatibility by both, the complexes and their precursors in human immunological
HL-60 cells, was evidenced. In view of the strongest toxic effect in the tumoral cell line provided by the free 5-npic ligand
(~ 40–50%), the overall anticancer complex performance seems to be triggered by the presence of this molecule.
Graphical Abstract
Keywords 5-Nitropicolinic acid · Lanthanide · Coordination compounds · Single-crystal X-ray diffraction · Prostate cancer
Amalia García-García and Pablo Cristobal-Cueto contributed
equally to this work.
* Patricia Horcajada
patricia.horcajada@imdea.org
* Sara Rojas
srojas@ugr.es
1
Department of Inorganic Chemistry, Faculty of Science,
University of Granada, Av. Fuente Nueva S/N,
18071 Granada, Spain
2
Advanced Porous Material Unit, IMDEA Energy Institute,
Av. Ramón de La Sagra 3, 28935 Móstoles, Madrid, Spain
Introduction
Cancer is one of the leading causes of death worldwide,
compromising more than 20 million people with nearly 10
million deaths worldwide only in 2020 [1, 2], remaining
still as one of the biggest global health challenges in the
twenty-first century. Particularly for men, prostate cancer is the second most frequent type of cancer, just after
lung carcinoma, with ~ 1.3 million new diagnosis each year
worldwide, making it a serious health concern [3]. Currently,
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early-stage prostate cancer treatments include prostate
removal, hormone and/or radiotherapy [4, 5], which are
associated with numerous side effects such as urinary or
erectile dysfunctions [6]. In advanced-stages, the frequent
tumoral metastasis and/or the appearance of resistance to
classical chemotherapeutic agents lead to inefficient therapies or prognosis. The current used chemotherapeutic agents
(e.g., mitoxantrone, estramustine, docetaxel) show short
average lifetime with a great resistant generation rate [7].
In this sense, European Union (EU) has fostered a renewed
commitment for cancer prevention, treatment and care for
improvement the patient´s quality life through novel missions and actions based on repurposing medicines, underpinning data sharing or reinforce collaborations (e.g., Europe’s
Beating Cancer Plan). One of these approaches in recent
years has been the use of metal complexes in chemotherapy
[8, 9], as for instance platinum complexes like oxaliplatin
or cisplatin [10–12], some of the most successful anticancer compounds clinically used for diverse cancers (ovarian,
gastrointestinal, bladder, etc.). For that reason, the relevance
of metallodrugs as therapeutic and imaging diagnostics has
exponentially risen in recent years: since cisplatin (1978) to
numerous emerged coordinated compounds, such as carboplatin for treating ovarian carcinoma, 99mTc-exametazime as
an imaging agent in inflammatory bowel disease, or bismuth
potassium citrate, currently evaluated in clinical trial for
COVID-19 treatment. Particularly, trivalent lanthanide ions
exhibit unique photoactive characteristics, including precise
emission spectra for exceptional color purity, wide emission
band that encompass the UV–Vis and near-infrared regions,
a diverse range of lifetimes spanning from microseconds
to seconds, remarkable luminescence quantum efficiencies
which makes them suitable for combining diagnostics and
therapy [13]. Further, they present a very low cytotoxicity, making them ideal for their application in biomedicine.
Among them, few lanthanide-based compounds were able to
undergo clinical trials, such as 177Lu-labeled anti-prostatespecific membrane antigen (PSMA) monoclonal antibody
J591 in radiotherapy against metastatic castration-resistant
prostate cancer (in phase II) [14], motexafin gadolinium for
photodynamic therapy against brain metastasis (in phase III)
or gadofosveset trisodium (based also on GdIII) for imageology of blood vessels (in phase IV) [15].
In our search for more efficient and potent metal-based
compounds to combat diverse types of cancer [16–18],
5-nitropicolinic acid has been chosen for the design and
preparation of novel coordination compounds. Picolinic
acid is a metabolic by-product of L-tryptophan catabolism,
exhibiting additional physiological effects such as anti-proliferative, immunological and neuroprotective features [19].
In particular, its anticancer properties have been already
demonstrated through its ability to disrupt the cell proliferation, triggering the programmed cell-death or, even, being
JBIC Journal of Biological Inorganic Chemistry (2024) 29:331–338
able to arrest the cell cycle in cancer cells [20]. Further, in
an attempt to improve its antitumor activity, we decided to
use the nitro-derivative, as nitro-group possesses a strong
electron attracting ability that creates localized electrondeficient sites with molecules and interacts with biological nucleophiles present in living systems, such as amino
acids [21]. Importantly, some nitro-group-containing drugs
(i.e., misonidazole [22], pimonidazole [23], niclosamide
[24]) present interesting antitumor properties, particularly
in prostate cancer.
In view of this scenario, we have focused on the synthesis of new picolinic-derived complexes with potential
antitumoral activity against prostate cancer. In an effort to
create a flexible platform for imaging and treatment purposes, lanthanides with known luminescent and/or antitumoral effects have been selected as the metal coordination
group [25, 26]: starting from the compound based on D
yIII
[27], previously reported by our group and complemented
by two new isostructural complexes based on G
dIII and
III
Tb (i.e., [Ln2(5-npic)6(H2O)4]·(H2O)2; 5-npic = 5-nitropicolinate; Ln = DyIII (1), GdIII (2), TbIII (3)). Their physicochemical characterization was performed using a set of
experimental techniques (e.g., Fourier-transform infrared
(FTIR), thermogravimetric analysis (TGA), fluorescence
and UV–Vis spectroscopies and X-ray diffraction). Finally,
their safety and antitumor activity were evaluated in vitro
using human promyelocytic HL-60 and prostatic tumoral
PC-3 cell lines, respectively.
Experimental
Materials and experimental techniques
All reagents were purchased from commercial sources
(Sigma-Aldrich, Merck Group, Darmstadt, Germany) and
were used as received without additional purification. Fourier transformed infrared (FTIR) spectra were measured in
solid state on a Bruker Tensor 27 FT-IR in the range of
4000–400 cm−1, and Opus software was used as a data collection program. Thermogravimetric analysis (TGA) of solid
samples were performed on a Shimadzu mod. TGA/50H
analyzer. Samples were heated from 28 to 950 ºC at a heating rate of 10 ºC·min−1 under air atmosphere. Routine X-ray
powder diffraction (XRPD) patterns were collected on a
BRUKER D8 DISCOVER diffractometer equipped with a
PILATUS3R 100 K-A detector and using Cu Kα radiation
(λ = 1.5406 Å). The XRPD patterns were registered with a
2θ range from 3° to 45° with a step size of 0.02° and scan
rate of 30 s per step. Stability profiles in phosphate buffered
saline (PBS) were measured by UV–Vis absorption on a
Cary 100 UV–Vis spectrophotometer (Agilent Technologies,
CA, USA) at a scan rate of 600 nm·min−1. Fluorescence
JBIC Journal of Biological Inorganic Chemistry (2024) 29:331–338
spectra in solid state at room temperature were carried out
in a Varian Cary-Eclipse spectrofluorometer (Agilent Technologies, CA, USA) at a scan rate of 120 nm·min−1.
Synthesis of metal complexes
Compounds 1–3 were obtained by following a hydrothermal
route. Firstly, 0.06 mmol of 5-npic ligand were dissolved
in 2 mL of distilled water. In a separate vial, 0.02 mmol
of the corresponding lanthanide salt (Dy(NO3)3·6H2O,
Gd(NO3)3·6H2O, or T
bCl3·6H2O) were dissolved in 1 mL
of distilled water. Then, the lanthanide salt was mixed over
ligand solution and the closed vial was introduced in the
oven at 95 ºC. After 48 h, suitable crystals for single-crystal
X-ray diffraction (SC-XRD) were obtained. The obtained
crystals were filtered off in air atmosphere and washed with
distilled water. The reproducibility of the synthesis was demonstrated by X-ray powder diffraction (XRPD; Fig. S1).
Single‑crystal X‑ray diffraction refinement
and crystallographic data
For all compounds, diffraction intensities were recorded on a
Bruker APEX-II CCD with a photon detector equipped with
graphite monochromated Mo Kα radiation (λ = 0.71073 Å).
The data reduction was carried out with APEX2 software
[28] and corrected for absorption with SADABS-2016/2
[29]. The structures were solved by direct methods and
refined by full-matrix least-squares with SHELXL-2018/3
[30] by using OLEX2 1.5 software [31]. The refinement
parameters are listed in Table S1. Details of selected bond
distances and angles are given in Tables S2–S3 (see Supporting information-SI). CCDC numbers are 2300374 and
2300375 for 2 and 3, respectively.
Stability assays
The chemical stability of the obtained complexes was determined in phosphate buffered saline (PBS) solution at 37 ºC
by measuring the release of 5-npic ligand by UV–Vis spectroscopy. A 0.1 mM solution of each compound was prepared in 30 mL of PBS and incubated under bidimensional
stirring at 37 ºC. At different incubation times (0, 0.25, 0.5,
1, 2, 3.5, and 5 h), an aliquot of 15 mL was extracted and the
same volume of PBS was added to the suspension in a way
to keep sink conditions. All kinetic studies were carried out
in triplicate (n = 3; see SI-Sect. 4 for further details).
Cell culture and cellular viability (MTT assay)
Human prostatic adenocarcinoma cell line PC-3 (ATCC
®
, CRL-1435™) was selected to evaluate the antitumoral
capacity in comparison with a non-tumoral cell line, the
333
human promyelocytic cells HL-60 (ATCC®, CCL-240™).
Both cell lines were cultured in RPMI 1640 (Roswell Park
Memorial Institute 1640) medium supplemented with 10%
fetal bovine serum (FBS) and 1% penicillin/streptomycin
(P/S) at 37 °C and 5% CO2 atmosphere. Cell lines were passaged twice a week at an 80% of cellular confluence (8 × 104,
∼1 × 105 cells per cm2), being harvested by trypsinization
(1% trypsin–EDTA solution).
For the cytotoxicity assays, compounds 1–3 along with
their metallic precursors and the organic ligand 5-npic were
evaluated by an MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) colorimetric assay. The cell line
was seeded 24 h before in 96-well plates at a density of
1 × 104 cells per well in RPMI medium supplemented with
10% FBS and 1% P/S. Treatment suspensions were prepared
as dilution series with cell culture media (30 µL of the sample in aqueous solution were added to a final volume of 300
µL in RPMI media) achieving different decreasing concentrations diluting from 500 to 8 µg·mL−1. Then, treated cells
were cultured for 24 h at 37 °C with a 5% CO2 atmosphere.
Subsequently, the MTT reagent was added (5 mg·mL−1 in
PBS) and incubated at 37 ºC for 2 h. Afterwards, MTT was
removed, adding 100 µL of dimethyl sulfoxide (DMSO) to
each well for 10 min. Finally, absorbance was determined at
λ = 539 nm. The percentage of cell viability was calculated
by the absorbance measurements of control growth and test
growth in the presence of the formulations at various concentration levels.
Results and discussion
Structural description of metal complexes
Compounds 1–3 are isostructural materials with the general
formula [Ln2(5-npic)6(H2O)4]·(H2O)2, where Ln = Dy (1),
Gd (2), and Tb (3). Compound 1 has already been described
by Raya-Barón et al. [27], thus, only compounds 2 and 3
will be here deeply described. The materials crystallize in
the monoclinic space group P21/c, which consist of LnIII
dinuclear complexes connected by an intricated hydrogenbond network (Fig. 1).
The asymmetric unit is composed by one lanthanide ion,
three coordinated 5-npic ligand molecules, two coordinated
water molecules, and one crystallization water molecule.
LnIII center is coordinated to four oxygen atoms from four
carboxylate groups of different ligand molecules, two water
molecules, and two nitrogen atoms belonging to two different pyridine rings, creating a LnO6N2 coordination polyhedron. The Ln-Ocarb bond distances are in the range of
2.296(4)–2.489(4) Å for 2 and 2.285(3)–2.471(3) Å for 3,
whereas the Ln-Npyr distances are 2.558(5) and 2.655(5) Å
for compound 2, and 2.545(4) and 2.648(4) for 3 (Tables
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JBIC Journal of Biological Inorganic Chemistry (2024) 29:331–338
Fig. 1 Isolated dinuclear entity
[Gd2(5-npic)6(H2O)4]·(H2O)2
and its detailed coordination
sphere. Color code: gadolinium,
green; carbon, grey; nitrogen,
blue; oxygen, red; and hydrogen, white
S2–S3), all in accordance with other similar complexes
[32–34]. In these materials, the ligand exhibits three different coordination modes, thanks to which, L
nIII ions are connected by two μ2-oxygen atoms of two monodentated carboxylates ligands to form the dinuclear entity. The formed
rhombus contains a crystallographic inversion center in the
middle and impose an intra-dinuclear Ln–Ln distance of
4.0984(11) and 4.0805(8) Å for 2 and 3, respectively.
Within the structure, inter- and intramolecular interactions assist to stabilize the structure (Fig. 2). There
are two intramolecular O···HO hydrogen bonds (2.759
and 2.754 Å for 2 and 3, respectively) that involve one
carboxylate group coordinated to one LnIII atom and one
water molecule coordinated to an adjacent L n III center.
Neighboring dinuclear entities form a 1D chain network
along the crystallographic c axis extended by O···HO
hydrogen bonds with distances in the range of 2.64–2.677
and 2.647–2.669 Å for 2 and 3, respectively, corresponding to the second coordinated water molecule and two oxygen atoms belonged to the adjacent carboxylate groups.
Finally, these 1D chains are packed along a axis by O···HO
hydrogen bonds involving the crystallization water molecules creating a 2D hydrogen bond network. In addition,
glide planes perpendicular to b axis create a like zig-zag
3D assembly.
Fig. 2 The dinuclear entities are packed one another along the a and c axis by an intricate hydrogen bond network (red dotted lines). In addition,
glide planes parallel to b axis create a like zig-zag 3D assembly. Color code as Fig. 1
JBIC Journal of Biological Inorganic Chemistry (2024) 29:331–338
335
5-npic
Transmittance
(C=O)
(C=C)
sym(N-O)
asym(N-O)
(C-H)in-plane
(C-N) (C-H)in-plane
(C-C-C)ring
(1)
(2)
(3)
1800
1600
1400
1200
1000
800
600
400
Wavenumber (cm-1)
Fig. 3 FTIR spectra of 5-npic and compounds 1–3 in solid state and
at room temperature
Infrared spectroscopy
The infrared spectra of complexes 1–3 and 5-npic ligand
were registered in solid state at room temperature (Fig. 3).
The characteristic bands of aromatic C–H bonds are
observed in the ligand spectra at 3090–3078 cm−1, being
nearly constant in the complexes’ spectra, as would be
expected according to linker position in the crystalline
structures. The peak correlated to stretch vibration of the
C=O bond of the carboxylic acid is shifted from 1699 to
1695 cm−1 for 5-npic ligand and lanthanide complexes,
respectively. This is indicative of the coordination between
the lanthanide ions and the organic linker by this functional group. In addition, the peaks at 1518 and 1354 cm−1,
attributed to the respective asymmetric and symmetric
vibrations of the N–O bond, did not shown any variation,
which suggests that the nitro group is not involved in any
type of interaction with the ligand. The next intense band
at 1296–1278 cm−1 is found in the ligand spectrum, which
corresponds to the stretching vibration of the C–N bond of
the pyridine ring, being shifted to 1317–1284 cm−1, since
the nitrogen atom of the ring is also coordinated to the lanthanide ions.
The linker emission is maintained for all complexes, with
almost identical spectrum with a slight intensity (Fig. 4).
The excitation spectra (recorded at λem = 486 nm) are characterized by two maxima peaks at 254 and 264 nm. Upon
excitation at the maximum λex = 254 nm, the emission spectra show several bands with an intense peak at 486 nm. Considering that complexes’ spectra were practically identical
compared to the free ligand, the emission process of 1–3
could be attributed to a ligand-centered mechanism. These
results demonstrate the potential of these as-prepared compounds as attractive fluorescence antitumoral molecules.
Stability properties
Bearing this in mind, a key feature for their effective antiproliferative or luminescent action is the investigation of the
material stability prior to any in vitro assay. In other words,
the potential leaching of their active constituents to the
physiological environment («its degradation process») in a
buffered solution. To this effect, the chemical stability of the
prepared compounds was investigated by UV–Vis spectroscopy over the time. As depicted in Fig. S4, all lanthanidecomplexes exhibited a similar degradation profile, with a fast
degradation profile (100% of linker release in 5 h in PBS). At
shorter times, the phosphate presence on the surroundings
seems to affect in a similar manner to all the lanthanides
complexes with a rapid initial release of the 5-npic (55 ± 9%,
40 ± 6% and 61 ± 6% in 30 min for 1, 2 and 3, respectively, namely as «burst effect»). The first 5-npic release
data (0–1 h) were fitted to a zero-order kinetic (Fig. S4).,
describing drug release at a constant rate independent from
its concentration in the media [39, 40]. Based on the calculated rate of release constants (K = 0.0114, 0.0152 and
0.0103 h−1 for 1, 2 and 3, respectively), compounds 1 and
3 exhibited a similar behavior, whereas the linker released
in 2 showed a slower leaching to the media. This could be
explained by the increase in the atomic numbers and the
corresponding decrease in ionic radii (GdIII > TbIII > DyIII),
Luminescent features
Several coordination complexes based on diverse picolinic
derivatives have already proven appealing photoluminescent
properties on its picolinate skeleton [35–37]. Regarding the
inorganic core, the potential application of lanthanide complexes in cancer therapy and diagnosis are growing great
interest as a result of their luminescent and magnetic properties [38]. In view of these previous attributes, solid-state
excitation and emission spectra of the novel compounds 1–3
and their 5-npic ligand were investigated at room temperature for polycrystalline samples.
Fig. 4 Excitation and emission spectra of compounds 1–3 and free
5-npic ligand (solid state) at room temperature
336
JBIC Journal of Biological Inorganic Chemistry (2024) 29:331–338
One of the current drawbacks of the antitumoral treatments
is the associated side effects, thus alternative strategies
to reduce toxicological concerns have been a challenging
research aim [43, 44]. Taking this into account, together with
the recognized antitumoral activity of both picolinate [20]
and lanthanide ions/complexes (Dy, Gd, and Tb) [45–47],
the safety and the antitumoral activity of the three obtained
complexes were evaluated. First, their biocompatibility was
assessed in human immunological cells HL-60, involved
in relevant biological processes such as the cellular redox
homeostasis or the activation of the immune system (e.g.,
reactive oxygen species, ROS, complement activation)
[48, 49]. Lastly, their antitumor effect was investigated in
a carcinogenic model, the prostatic PC-3 adenocarcinoma,
selected as the most diagnosed male cancer and the 2nd
highest cause of male cancer-related death [50]. After 24 h
of exposure, both cell lines were influenced by the presence
of these complexes regardless the metallic nature, observing
a slightly higher toxicological effect with the higher complex
doses in contact with the prostatic cells. In particular, cell
viability decreased up to 50 ± 10% in the case of compounds
1 and 2, and 60 ± 25% for 3 at the highest concentration
(500 µg·mL−1 of all compounds; Fig. 5). Regarding their
immunological impact, this metallic tendency was also noted
but providing greatest biocompatible profile since the cellular viability was maintained ~ 70 ± 12%. IC50 calculated
values are: Compound 1 = 427 ± 16 and 819 ± 12 µg·mL−1,
Compound 2 = 538 ± 23 and 682 ± 11 µg·mL−1, Compound
3 = 654 ± 22 and 667 ± 15 µg·mL−1, for PC-3 and HL-60,
respectively). Hence, one could suggest that these lanthanides-based complexes could provide potential effective
antitumoral activity against tumoral cells in comparison with
the non-tumoral nature.
In view of these circumstances, the cytotoxicity repercussion of each precursor was also assessed to shed light on the
antitumoral mechanism of these materials. Thus, both the
5-npic linker along with the three lanthanide salts sources
(Dy(NO3)3·6H2O, Gd(NO3)3·6H2O, and TbCl3·6H2O) were
put in contact under the immunological and tumoral cellular
scenario at the same proportion of each coordination complex. A high biocompatibility profile was obtained regardless
the metallic precursors or chosen concentration, observing a
slight reduction coming from the terbium, gadolinium and
dysprosium hydrated salts (80 ± 20, 90 ± 13, and 100 ± 15%
for TbCl3, Gd(NO3)3, and Dy(NO3)3, respectively; Fig. S6).
In contrast, it should be noted that the strongest toxicity effect
produced by 5-npic linker with a decrease of the tumoral cell
viability up to ~ 40–50% in comparison with the non-tumoral
(~ 60%). Thus, the main activity seems to be provided by the
presence of the linker since 55 ± 9%, 40 ± 6% and 61 ± 6%
of 5-npic for 1, 2 and 3 were released in 30 min under PBS
(reaching 100% of leakage after 5 h; see Fig. S4). Despite
the free linker was also able to impact on the immunological cells, this effect seemed to be potentially decreased by
its complexation with the lanthanide ions under the selected
A)
B)
which significantly affects the bond strength [41]. Finally,
and considering the Pourbaix diagram [42], the metallic species will be released as trivalent lanthanide ions to the solution considering the working conditions.
In vitro biocompatibility
100
100
50
0
Compound 3 - Tb
Compound 2 - Gd
Compound 1 - Dy
Cell Viability (%)
HL-60 cells
Cell Viability (%)
PC3 cells
Compound 3 - Tb
Compound 2 - Gd
Compound 1 - Dy
8
16
31
63
125
250
500
-1
Concentration (µg·mL )
Fig. 5 Cell viability of A) PC-3 cells and B) HL-60 after 24 h of
incubation with 1–3. Note that the shown data corresponds to the
average of triplicate for each concentration, obtained in three inde-
50
0
8
16
31
63
125
250
500
-1
Concentration (µg·mL )
pendent experiments (a total of n = 9). Vertical error bars indicate calculated standard deviations
JBIC Journal of Biological Inorganic Chemistry (2024) 29:331–338
337
in vitro conditions (e.g., structural maintenance, delayed linker
release). For those reasons, a higher antitumoral effect and
lower cytotoxicity in immunological cells were observed for
lanthanide-complexes compared to free ligand. Finally, further
investigations are required to study the potential action mechanism depending on the complex composition and/or material
stability (chemical and structural).
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Conclusions
References
Two novel lanthanide-complexes have been newly prepared
and characterized based on Gd and Tb and 5-nitropicolinate,
which are isostructural to a previous one published by us
based on Dy: [ Ln2(5-npic)6(H2O)4]·(H2O)2, where Ln = Dy
(1), Gd (2), and Tb (3).
Photoluminescent measurements revealed that the complexes exhibit ligand-centered emission probably due to
π–π* electronic transitions in the aromatic ring of the ligand.
On the other hand, all complexes showed anti-proliferative
activity against the prostatic PC-3 adenocarcinoma cell line,
regardless of the metallic nature with, however, a lower cytotoxic impact against healthy immunological cells. Considering that these are the first metal complexes based on Ln-ions
with antiprostatic and luminescent properties, these results
open the door of the development of novel Ln-complexes
with potential combined treatment and diagnosis capabilities. Work can be anticipated in extending these intriguing
results to novel 5-nitropicolinic acid with higher stability.
Supplementary Information The online version contains supplementary material available at https://d oi.o rg/1 0.1 007/s 00775-0 24-0 2054-0.
Acknowledgements S.R. is grateful for the grant (RYC2021‐032522‐I)
funded by MCIN/AEI /https://d oi.o rg/1 0.1 3039/5 01100 01103 3 and for
El FSE invierte en tu futuro. A.G.-G. thanks Ministerio de Universidades and Next Generation for a Margarita Salas postdoctoral contract. T.H. and P.H. acknowledge the Multifunctional Metallodrugs
in Diagnosis and Therapy Network (MICIU, RED2018-102471-T).
T.H. thanks the European Union’s Horizon 2020 Research and Innovation Programme under the Marie Sklodowska-Curie grant agreement No 897678 (NeuroMOF). I.J.V.-Y. thanks Junta de Andalucía
(P20_01041).
Funding Funding for open access publishing: Universidad de Granada/
CBUA.
Data availability The data that support the findings of this study are
available on request from the corresponding author.
Declarations
Conflict of interest The authors declare that there is no conflict of interest.
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long
as you give appropriate credit to the original author(s) and the source,
provide a link to the Creative Commons licence, and indicate if changes
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