1
|
Improving the Stability and Kinetic Inertness of Mn(II) Complexes by Increasing the Bridge Length in Bicyclic CDTA-Like Ligands. Chemistry 2024:e202400570. [PMID: 38597334 DOI: 10.1002/chem.202400570] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2024] [Revised: 04/08/2024] [Accepted: 04/10/2024] [Indexed: 04/11/2024]
Abstract
Kinetic inertness of Mn(II)-based MRI contrast agents can be improved by increasing the rigidity of the polydentate ligand that tightly coordinate the metal ion. Taking inspiration from the remarkable increase in kinetic inertness of [Mn(CDTA)]2- compared to [Mn(EDTA)]2- due to the cyclohexyl backbone rigidity, we devised that bicyclic ligands would further improve the kinetic inertness of the Mn(II) complexes. The length of the alkyl bridge on the cyclohexane ring was varied from methylene (BCH-DTA), ethylene (BCO-DTA) to propylene (BCN-DTA) to evaluate the influence of the different trans-diaminotetraacetate ligands on relaxometric, thermodynamic and kinetic properties of the Mn(II) complexes. 1H and 17O NMR relaxometric studies showed a slight increase in relaxivity and a faster water exchange rate in these Mn(II)-complexes with respect to [Mn(CDTA)]2-. Solution studies revealed that the conditional stability (pMn) and dissociation half-life (t1/2) at pH 7.4 follow the order [Mn(BCH-DTA)]2-<[Mn(BCO-DTA)]2-<[Mn(BCN-DTA)]2- highlighting the effect of the bridge length on the overall stability of the Mn(II) complexes. Remarkably, [Mn(BCN-DTA)]2- shows an improved pMn value and a 7-times higher kinetic inertness than [Mn(CDTA)]2-. NMR studies on the Zn(II) analogues confirm the rigidity of the bicyclic complexes with an isomerization process at >313 K for the smaller bridged complex [Zn(BCH-DTA)]2-.
Collapse
|
2
|
Risk of infections related to endovascular catheters and cardiac implantable devices in hemodialysis patients. J Vasc Access 2024:11297298241240502. [PMID: 38506890 DOI: 10.1177/11297298241240502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/21/2024] Open
Abstract
Patients requiring dialysis are extremely vulnerable to infectious diseases. The high burden of comorbidities and weakened immune system due to uremia and previous immunosuppressive therapy expose the patient on dialysis to more infectious events than the general population. The infectious risk is further increased by the presence of endovascular catheters and implantable cardiologic devices. The former is generally placed as urgent vascular access for dialysis and in subjects requiring hemodialysis treatments without autogenous arteriovenous fistula. The high frequency of cardiovascular events also increases the likelihood of implanting indwelling implantable cardiac devices (CIED) such as pacemakers (PMs) and defibrillators (ICDs). The simultaneous presence of CVC and CIED yields an increased risk of developing severe prosthetic device-associated bloodstream infections often progressing to septicemia. Although, antibiotic therapy is the mainstay of prosthetic device-related infections, antibiotic resistance of biofilm-residing bacteria reduces the choice of infection eradication. In these cases, the resolution of the infection process relies on the removal of the prosthetic device. Compared to CVC removal, the extraction of leads is a more complex procedure and poses an increased risk of vessel tearing. As a result, the prevention of prosthetic device-related infection is of utmost importance in hemodialysis (HD) patients and relies principally on avoiding CVC as vascular access for HD and placement of a new class of wireless implantable medical devices. When the combination of CVC and CIED is inevitable, prevention of infection, mainly due translocation of skin bacteria, should be a mandatory priority for healthcare workers.
Collapse
|
3
|
Novel Nanogels Loaded with Mn(II) Chelates as Effective and Biologically Stable MRI Probes. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 19:e2302868. [PMID: 37345577 DOI: 10.1002/smll.202302868] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Revised: 06/01/2023] [Indexed: 06/23/2023]
Abstract
Here it is described nanogels (NG) based on a chitosan matrix, which are covalently stabilized by a bisamide derivative of Mn-t-CDTA (t-CDTA = trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid). the Mn(II) complex acts both as a contrast medium and as a cross-linking agent. These nanogels are proposed as an alternative to the less stable paramagnetic nanogels obtained by electrostatic interactions between the polymeric matrix and paramagnetic Gd(III) chelates. The present novel nanogels show: i) relaxivity values seven times higher than that of typical monohydrated Mn(II) chelates at the clinical fields, thanks to the combination of a restricted mobility of the complex with a fast exchange of the metal-bound water molecule; ii) high stability of the formulation over time at pH 5 and under physiological conditions, thus excluding metal leaking or particles aggregation; iii) good extravasation and accumulation, with a maximum contrast achieved at 24 h post-injection in mice bearing subcutaneous breast cancer tumor; iv) high T1 contrast (1 T) in the tumor 24 h post-injection. These improved properties pave the way for the use of these paramagnetic nanogels as promising magnetic resonance imaging (MRI) probes for in vitro and in vivo preclinical applications.
Collapse
|
4
|
Thermodynamic and Kinetic Stabilities of Al(III) Complexes with N 2O 3 Pentadentate Ligands. Molecules 2023; 28:molecules28093764. [PMID: 37175174 PMCID: PMC10180113 DOI: 10.3390/molecules28093764] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Revised: 04/21/2023] [Accepted: 04/24/2023] [Indexed: 05/15/2023] Open
Abstract
Al(III) complexes have been recently investigated for their potential use in imaging with positron emission tomography (PET) by formation of ternary complexes with the radioisotope fluorine-18 (18F). Although the derivatives of 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) are the most applied chelators for [Al18F]2+ labelling and (pre)clinical PET imaging, non-macrocyclic, semi-rigid pentadentate chelators having two N- and three O-donor atoms such as RESCA1 and AMPDA-HB have been proposed with the aim to allow room temperature labelling of temperature-sensitive biomolecules. The paucity of stability data on Al(III) complexes used for PET imaging instigated a complete thermodynamic and kinetic solution study on Al(III) complexes with aminomethylpiperidine (AMP) derivatives AMPTA and AMPDA-HB and the comparison with a RESCA1-like chelator CD3A-Bn (trans-1,2-diaminocyclohexane-N-benzyl-N,N',N'-triacetic acid). The stability constant of [Al(AMPDA-HB)] is about four orders of magnitude higher than that of [Al(AMPTA)] and [Al(CD3A-Bn)], highlighting the greater affinity of phenolates with respect to acetate O-donors. On the other hand, the kinetic inertness of the complexes, determined by following the Cu2+-mediated transmetallation reactions in the 7.5-10.5 pH range, resulted in a spontaneous and hydroxide-assisted dissociation slightly faster for [Al(AMPTA)] than for the other two complexes (t1/2 = 4.5 h for [Al(AMPTA)], 12.4 h for [Al(AMPDA-HB)], and 24.1 h for [Al(CD3A-Bn)] at pH 7.4 and 25 °C). Finally, the [AlF]2+ ternary complexes were prepared and their stability in reconstituted human serum was determined by 19F NMR experiments.
Collapse
|
5
|
High spin Fe(III)-doped nanostructures as T 1 MR imaging probes. WILEY INTERDISCIPLINARY REVIEWS. NANOMEDICINE AND NANOBIOTECHNOLOGY 2023; 15:e1858. [PMID: 36251471 DOI: 10.1002/wnan.1858] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 09/13/2022] [Accepted: 09/14/2022] [Indexed: 12/05/2022]
Abstract
Magnetic Resonance Imaging (MRI) T1 contrast agents based on Fe(III) as an alternative to Gd-based compounds have been under intense scrutiny in the last 6-8 years and a number of nanostructures have been designed and proposed for in vivo diagnostic and theranostic applications. Excluding the large family of superparamagnetic iron oxides widely used as T2 -MR imaging agents that will not be covered by this review, a considerable number and type of nanoparticles (NPs) have been employed, ranging from amphiphilic polymer-based NPs, NPs containing polyphenolic binding units such as melanin-like or polycatechols, mixed metals such as Fe/Gd or Fe/Au NPs and perfluorocarbon nanoemulsions. Iron(III) exhibits several favorable magnetic properties, high biocompatibility and improved toxicity profile that place it as the paramagnetic ion of choice for the next generation of nanosized MRI and theranostic contrast agents. An analysis of the examples reported in the last decade will show the opportunities for relaxivity and MR-contrast enhancement optimization that could bring Fe(III)-doped NPs to really compete with Gd(III)-based nanosystems. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Diagnostic Tools > Diagnostic Nanodevices Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.
Collapse
|
6
|
AAZTA-Like Ligands Bearing Phenolate Arms as Efficient Chelators for 68 Ga Labelling in vitro and in vivo. Chemistry 2023; 29:e202203798. [PMID: 36719326 DOI: 10.1002/chem.202203798] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Revised: 01/31/2023] [Accepted: 01/31/2023] [Indexed: 02/01/2023]
Abstract
The introduction of a phenolate pendant arm in place of an acetate on AAZTA- and DATA-like ligands resulted in hepta- and hexadentate chelators able to form Ga(III) complexes with thermodynamic stability and kinetic inertness higher than that of other Ga(III) complexes based on the parent 6-amino-6-methylperhydro-1,4-diazepine scaffold. In particular, the heptadentate AAZ3A-endoHB with a phenolate arm on an endocyclic N-atom shows a logKGaL of 27.35 and a remarkable resistance to hydroxide coordination up to basic pH (pH>9). This behaviour allows to also improve the kinetic inertness of the complex showing a dissociation half-life (t1/2 ) at pH 7.4 of 76 h. Although also the hexadentate AAZ2A-exoHB chelator forms a stable (logKGaL =24.69) and inert (t1/2 =33 h at pH 7.4) Ga(III) complex, the 68 Ga labelling showed a better radiochemical yield with AAZ3A-endoHB, especially at room temperature. Thus, a bifunctional chelator of AAZ3A-endoHB was synthesized bearing an isothiocyanate group that was conjugated to the N-terminus of a c(RGD) peptide for integrin receptor targeting. Finally, the conjugate was successfully labelled with 68 Ga isotope, and the resulting radiotracer tested for its stability in human serum and then in vivo for targeting B16-F10 tumours with miniPET imaging.
Collapse
|
7
|
A Neutral and Stable Macrocyclic Mn(II) Complex for MRI Tumor Visualization. ChemMedChem 2022; 17:e202200508. [PMID: 36198652 PMCID: PMC10092550 DOI: 10.1002/cmdc.202200508] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Revised: 10/05/2022] [Indexed: 01/14/2023]
Abstract
A stable and inert amphiphilic Mn(II) complex based on a bisamide derivative of 1,4-DO2A (DO2A=tetraazacyclododecane-1,4-diacetic acid) was synthesized and its 1 H NMR relaxometric behavior was investigated as a function of the magnetic field strength, pH and temperature. The interaction with human serum albumin (HSA) was also studied via relaxometry showing a good relaxivity enhancement at low field (at 1T and 298 K the relaxivity increases from 4.5 mM-1 s-1 of the Mn(II)-complex to 14.0 mM-1 s-1 of the complex-HSA supramolecular adduct). In vivo biodistribution and MRI studies highlighted a rapid and mixed renal/liver elimination without spleen accumulation from healthy mice and good contrast enhancing properties in a breast tumor murine model. A comparison with a clinically approved Gd(III) agent (GdBOPTA, Multihance®) underlined that the proposed Mn(II) contrast agent gave comparable tumor contrast enhancement up to 3 hours post-injection.
Collapse
|
8
|
Derivatives of GdAAZTA Conjugated to Amino Acids: A Multinuclear and Multifrequency NMR Study. Inorg Chem 2022; 61:13199-13209. [PMID: 35944034 PMCID: PMC9400103 DOI: 10.1021/acs.inorgchem.2c02110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
The GdAAZTA (AAZTA = 6-amino-6-methylperhydro-1,4-diazepinetetraacetic
acid) complex represents a platform of great interest for the design
of innovative MRI probes due to its remarkable magnetic properties,
thermodynamic stability, kinetic inertness, and high chemical versatility.
Here, we detail the synthesis and characterization of new derivatives
functionalized with four amino acids with different molecular weights
and charges: l-serine, l-cysteine, l-lysine,
and l-glutamic acid. The main reason for conjugating these
moieties to the ligand AAZTA is the in-depth study of the chemical
properties in aqueous solution of model compounds that mimic complex
structures based on polypeptide fragments used in molecular imaging
applications. The analysis of the 1H NMR spectra of the
corresponding Eu(III)-complexes indicates the presence of a single
isomeric species in solution, and measurements of the luminescence
lifetimes show that functionalization with amino acid residues maintains
the hydration state of the parent complex unaltered (q = 2). The relaxometric properties of the Gd(III) chelates were analyzed
by multinuclear and multifrequency NMR techniques to evaluate the
molecular parameters that determine their performance as MRI probes.
The relaxivity values of all of the novel chelates are higher than
that of GdAAZTA over the entire range of applied magnetic fields because
of the slower rotational dynamics. Data obtained in reconstituted
human serum indicate the occurrence of weak interactions with the
proteins, which result in larger relaxivity values at the typical
imaging fields. Finally, all of the new complexes are characterized
by excellent chemical stability in biological matrices over time,
by the absence of transmetallation processes, or the formation of
ternary complexes with oxyanions of biological relevance. In particular,
the kinetic stability of the new complexes, measured by monitoring
the release of Gd3+ in the presence of a large excess of
Zn2+, is ca. two orders of magnitude higher than that of
the clinical MRI contrast agent GdDTPA. Novel
GdAAZTA derivatives conjugated to four amino acids
were synthesized and characterized through a multi-technique approach.
The complexes maintained the favorable thermodynamic and kinetic properties
of the parent compound and showed higher relaxivity values in clinical
fields. Therefore, they represent a useful model of more complex bio-conjugated
structures used in molecular imaging applications.
Collapse
|
9
|
MO137: Sarcoidosis in a Living Kidney Donor Candidate: Case Report and Review of the Literature. Nephrol Dial Transplant 2022. [DOI: 10.1093/ndt/gfac066.039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Abstract
BACKGROUND AND AIMS
Sarcoidosis (SCD) is a granulomatous disease that mostly affects young adults, presenting with hilar adenopathy, lung reticular opacities and skin/joint/eye lesions. Incidence varies in Europe between 0.3% and 1.5%, higher in southern countries. Up to one-third of patients have extrathoracic manifestations.
Renal involvement varies among different case series. Despite a prevalence of about 13% in autopsies on systemic SCD affected individuals, it is clinically evident in 0.7–4.3% of patients, with a reduced glomerular filtration rate associated with mild or absent urinary anomalies. It usually presents as a tubulointerstitial nephritis at kidney biopsy. Noncaseating granulomas are typical but not always present. Renal injury can also derive from hyperkalcaemia and hypercalciuria (secondary to vitaminD production in granulomas), which cause nephrocalcinosis or nephrolitiasis. A clinical presentation with hyperkalcaemia associates to a better response to therapy (prednisone 1 mg/kg/day for 6–12 weeks, tapered in 6–9 months). An Italian survey on SCD acute kidney injury (AKI) described female sex, hyperkalaemia and absence of granulomas at biopsy as positive prognostic factors, without any correlation between proteinuria and histological damage. SCD AKI evolved to CKD in over 60% of cases (37.5% without comorbidities at onset), with a mean GFR slope of 5 mL/min/year when granulomatous interstitial nephritis was present.
METHOD
We describe the case of a 55-year-old male, who proposed as a living kidney donor for his wife. His clinical history included a paranoid episode 20 years before, compensated and on psychiatric follow-up at the moment of the screening, dyslipidaemia and normal blood pressure.
RESULTS
Preoperative screening showed a renal function just above safety threshold for donation (cystatin C-creatinine CKD-EPI 80 mL/min/1.73 m2), a normal urinary sediment and no proteinuria. A thoracic and abdominal CT scan (Figure 1) described numerous aorto-caval adenopathies, stable at a second CT after 3 months. Lungs were unaffected, kidneys and the urinary tract were regular, without calcifications or stones.
No infection was detected (negative QuantiFERON, HIV, EBV <1000 copies/mL), suggesting a differential diagnosis between lymphoma and SCD. Serum and urine electrophoresis, immunofixation, light chains, Bence Jones and peripheral blood lymphocyte typing were checked in parallel to ACE dosing; 24-h urine calcium, calcemia, vitamin D, dermatological and ocular examination all normal. An endobronchial ultrasound biopsy was performed, after a PET (Figure 2) to identify the targets with the highest SUV (3.9–6.7). Histology described normal lymphocytes, noncaseating granulomas with sarcoidosis epithelioid histiocytes.
CONCLUSION
Stage 1 pulmonary SCD without clinical renal involvement was confirmed. Although in a single case of living kidney donation from SCD affected subject was reported, data on GFR deterioration in the long term are lacking. Considering the baseline renal function of the potential donor and the not-quantifiable risk of future AKI, we decided to deem him unfit for donation, despite the absence of markers of disease activity at the moment of the screening. Kidney biopsy will be considered in the future in case of urinary abnormalities or GFR deterioration.
Collapse
|
10
|
High Relaxivity with No Coordinated Waters: A Seemingly Paradoxical Behavior of [Gd(DOTP)] 5- Embedded in Nanogels. Inorg Chem 2022; 61:5380-5387. [PMID: 35316037 PMCID: PMC8985129 DOI: 10.1021/acs.inorgchem.2c00225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
Nanogels (NGs) obtained
by electrostatic interactions between chitosan
and hyaluronic acid and comprising paramagnetic Gd chelates are gaining
increasing attention for their potential application in magnetic resonance
bioimaging. Herein, the macrocyclic complexes [Gd(DOTP)]5−, lacking metal-bound water molecules (q = 0), were
confined or used as a cross-linker in this type of NG. Unlike the
typical behavior of Gd complexes with q = 0, a remarkable
relaxivity value of 78.0 mM–1 s–1 was measured at 20 MHz and 298 K, nearly 20 times greater than that
found for the free complex. A careful analysis of the relaxation data
emphasizes the fundamental role of second sphere water molecules with
strong and long-lived hydrogen bonding interactions with the complex.
Finally, PEGylated derivatives of nanoparticles were used for the
first in vivo magnetic resonance imaging study of
this type of NG, revealing a fast renal excretion of paramagnetic
complexes after their release from the NGs. Nanogels incorporating [Gd(DOTP)]5− complexes
(q = 0) exhibit remarkable relaxivity values, thanks
to structured water molecules in the second coordination shell of
the metal ion involved in strong H-bonding interactions with the phosphonate
groups.
Collapse
|
11
|
The critical role of ligand topology: strikingly different properties of Gd( iii) complexes with regioisomeric AAZTA derivatives. Inorg Chem Front 2022. [DOI: 10.1039/d2qi00451h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Two regioisomeric Gd(III) complexes with heptadentate AAZTA-like ligands show different hydration state (q = 1 and 2) and astonishingly different thermodynamic stability and dissociation kinetics.
Collapse
|
12
|
Abstract
The controlled synthesis of amphiphilic di-block copolymers allows a large array of nanostructures to be created, including block copolymer particles, which have proved valuable for biomedical applications. Despite progress in...
Collapse
|
13
|
Immunosuppressive therapy reduction and early post-infection graft function in kidney transplant recipients with COVID-19. GIORNALE ITALIANO DI NEFROLOGIA : ORGANO UFFICIALE DELLA SOCIETA ITALIANA DI NEFROLOGIA 2021; 38:2021-vol6. [PMID: 34919795] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Background: Kidney transplant (KT) recipients with COVID-19 are at high risk of poor outcomes due to the high burden of comorbidities and immunosuppression. The effects of immunosuppressive therapy (IST) reduction are unclear in patients with COVID-19. Methods: A retrospective study on 45 KT recipients followed at the University Hospital of Modena (Italy) who tested positive for COVID-19 by RT-PCR analysis. Results: The median age was 56.1 years (interquartile range,[IQR] 47.3-61.1), with a predominance of males (64.4%). Kidney transplantation vintage was 10.1 (2.7-16) years, and 55.6 % of patients were on triple IST before COVID-19. Early immunosuppression minimization occurred in 27 (60%) patients (reduced-dose IST group) and included antimetabolite (88.8%) and calcineurin inhibitor withdrawal (22.2%). After SARS-CoV-2 infection, 88.9% of patients became symptomatic and 42.2% required hospitalization. One patient experienced irreversible graft failure. There were no differences in serum creatinine level and proteinuria in non-hospitalized patients before and post-COVID-19, whereas hospitalized patients experienced better kidney function after hospital discharge (P=0.019). Overall mortality was 17.8%. without differences between full- and reduced-dose IST. Risk factors for death were age (odds ratio [OR]: 1.19; 95%CI: 1.01-1.39), and duration of kidney transplant (OR: 1.17; 95%CI: 1.01-1.35). One KT recipient developed IgA glomerulonephritis and two ones experienced symptomatic COVID-19 after primary infection and SARS-CoV-2 mRNA vaccine, respectively. Conclusions: Despite the reduction of immunosuppression, COVID-19 affected the survival of KT recipients. Age of patients and time elapsed from kidney transplantation were independent predictors of death . Early kidney function was favorable in most survivors after COVID-19.
Collapse
|
14
|
Abstract
![]()
Typically, Ln(III)
complexes are isostructural along the series,
which enables studying one particular metal chelate to derive the
structural features of the others. This is not the case for [Ln(AAZTA)(H2O)x]− (x = 1, 2) systems, where structural variations along the
series cause changes in the hydration number of the different metal
complexes, and in particular the loss of one of the two metal-coordinated
water molecules between Ho and Er. Herein, we present a 1H field-cycling relaxometry and 17O NMR study that enables
accessing the different exchange dynamics processes involving the
two water molecules bound to the metal center in the [Gd(AAZTA)(H2O)2]− complex. The resulting
picture shows one Gd-bound water molecule with an exchange rate ∼6
times faster than that of the other, due to a longer metal–water
distance, in accordance with density functional theory (DFT) calculations.
The substitution of the more labile water molecule with a fluoride
anion in a diamagnetic-isostructural analogue of the Gd-complex, [Y(AAZTA)(H2O)2]−, allows us to follow the
chemical exchange process by high-resolution NMR and to describe its
thermodynamic behavior. Taken together, the variety of tools offered
by NMR (including high-resolution 1H, 19F NMR
as a function of temperature, 1H longitudinal relaxation
rates vs B0, and 17O transverse
relaxation rates vs T) provides a complete description
of the structure and exchange dynamics of these Ln-complexes along
the series. Herein, we present a 1H field−cycling
relaxometry and 17O NMR study that enables accessing the
different exchange dynamics processes involving the two water molecules
bound to the metal center in the [Gd(AAZTA)(H2O)2]− complex.
Collapse
|
15
|
Defining the conditions for the development of the emerging class of Fe III-based MRI contrast agents. Chem Sci 2021; 12:11138-11145. [PMID: 34522311 PMCID: PMC8386674 DOI: 10.1039/d1sc02200h] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Accepted: 07/07/2021] [Indexed: 02/05/2023] Open
Abstract
Fe(iii) complexes are attracting growing interest in chemists developing diagnostic probes for Magnetic Resonance Imaging because they leverage on an endogenous metal and show superior stability. However, in this case a detailed understanding of the relationship between the chemical structure of the complexes, their magnetic, thermodynamic, kinetic and redox properties and the molecular parameters governing the efficacy (relaxivity) is still far from being available. We have carried out an integrated 1H and 17O NMR relaxometric study as a function of temperature and magnetic field, on the aqua ion and three complexes chosen as reference models, together with theoretical calculations, to obtain accurate values of the parameters that control their relaxivity. Moreover, thermodynamic stability and dissociation kinetics of the Fe(iii) chelates, measured in association with the ascorbate reduction behaviour, highlight their role and mutual influence in achieving the stability required for use in vivo. An integrated 1H and 17O NMR relaxometric study on model systems allowed to highlight that the Fe(III) complexes might represent the best alternative to Gd-based MRI contrast agents at the magnetic fields of current and future clinical scanners.![]()
Collapse
|
16
|
Rigid and Compact Binuclear Bis-hydrated Gd-complexes as High Relaxivity MRI Agents. Chemistry 2021; 27:11811-11817. [PMID: 34114699 PMCID: PMC8456821 DOI: 10.1002/chem.202101701] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Indexed: 11/21/2022]
Abstract
The first binuclear Gd‐complex of the 12‐membered pyridine‐based polyaminocarboxylate macrocyclic ligand PCTA was synthesized by C−C connection of the pyridine units through two different synthetic procedures. A dimeric AAZTA‐ligand was also synthesized with the aim to compare the relaxometric results or the two ditopic Gd‐complexes. Thus, the 1H relaxometric study on [Gd2PCTA2(H2O)4] and on [Gd2AAZTA2(H2O)4]2− highlighted the remarkable rigidity and compactness of the two binuclear complexes, which results in molar relaxivities (per Gd), at 1.5 T and 298 K of ca. 12–12.6 mM−1 s−1 with an increase of ca. 80 % at 1.5 T and 298 K (+70 % at 310 K) with respect to the corresponding mononuclear complexes.
Collapse
|
17
|
Underlining the Importance of Peripheral Protic Functional Groups to Enhance the Proton Exchange of Gd-Based MRI Contrast Agents. Inorg Chem 2021; 60:13626-13636. [PMID: 34387463 PMCID: PMC8769378 DOI: 10.1021/acs.inorgchem.1c01927] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
![]()
In
this study, we report the synthesis and the equilibrium, kinetic,
relaxation, and structural properties of two new GdIII complexes
based on modified 10-(2-hydroxypropyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic
acid (HPDO3A) designed to modulate the relaxivity at acidic and basic
pH due to intra- and intermolecular proton exchange. The presence
of a carboxylic or ester moieties in place of the methyl group of
HPDO3A allowed differentiation of a protic and nonprotic functional
group, highlighting the importance of the formation of an intramolecular
hydrogen bond between the coordinated hydroxyl and the carboxylate
groups for proton exchange (kH = 1.5 ×
1011 M–1 s–1, kOH = 1.7 × 109 M–1 s–1). The determination of the thermodynamic stability
and kinetic inertness of the GdIII complexes confirmed
that the modification of peripheral groups does not significantly
affect the coordination environment and thus the stability (log KGdL = 19.26, t1/2 = 2.14 × 107 hours, pH = 7.4, 0.15 M NaCl, 25 °C).
The relaxivity (r1) was measured as a
function of pH to investigate the proton exchange kinetics, and as
a function of the magnetic field strength to extrapolate the relaxometric
parameters (r1GdL1 = 4.7 mM–1 s–1 and r1GdL2 = 5.1 mM–1 s–1 at 20 MHz, 25 °C, and pH 7.4). Finally, the X-ray crystal structure
of the complex crystallized at basic pH showed the formation of a
tetranuclear dimer with alkoxide and hydroxide groups bridging the
GdIII ions. The peripheral
carboxylic moiety of a 2-hydroxypropanoic
pendant arm of a GdHPDO3A-like complex forms an intramolecular hydrogen
bond with the −OH group that allows both acid- and base-catalyzed
proton exchange and thus a relaxivity enhancement. Conversely, the
nonprotic ester group in the same position permits only the base-catalyzed
mechanism.
Collapse
|
18
|
Towards Enhanced MRI Performance of Tumor-Specific Dimeric Phenylboronic Contrast Agents. Molecules 2021; 26:molecules26061730. [PMID: 33808910 PMCID: PMC8003780 DOI: 10.3390/molecules26061730] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2021] [Revised: 03/15/2021] [Accepted: 03/16/2021] [Indexed: 01/06/2023] Open
Abstract
It is known that phenylboronic acid (PBA) can target tumor tissues by binding to sialic acid, a substrate overexpressed by cancer cells. This capability has previously been explored in the design of targeting diagnostic probes such as Gd- and 68Ga-DOTA-EN-PBA, two contrast agents for magnetic resonance imaging (MRI) and positron emission tomography (PET), respectively, whose potential has already been demonstrated through in vivo experiments. In addition to its high resolution, the intrinsic low sensitivity of MRI stimulates the search for more effective contrast agents, which, in the case of small-molecular probes, basically narrows down to either increased tumbling time of the entire molecule or elevated local concentration of the paramagnetic ions, both strategies resulting in enhanced relaxivity, and consequently, a higher MRI contrast. The latter strategy can be achieved by the design of multimeric GdIII complexes. Based on the monomeric PBA-containing probes described recently, herein, we report the synthesis and characterization of the dimeric analogues (GdIII-DOTA-EN)2-PBA and (GdIII-DOTA-EN)2F2PBA. The presence of two Gd ions in one molecule clearly contributes to the improved biological performance, as demonstrated by the relaxometric study and cell-binding investigations.
Collapse
|
19
|
Polymerizable Gd(iii) building blocks for the synthesis of high relaxivity macromolecular MRI contrast agents. Chem Sci 2021; 12:3999-4013. [PMID: 34163670 PMCID: PMC8179470 DOI: 10.1039/d0sc04750c] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
A new synthetic strategy for the preparation of macromolecular MRI contrast agents (CAs) is reported. Four gadolinium(iii) complexes bearing either one or two polymerizable methacrylamide groups were synthesized, serving as monomers or crosslinkers for the preparation of water-soluble, polymeric CAs using Reversible Addition–Fragmentation Chain Transfer (RAFT) polymerization. Using this approach, macromolecular CAs were synthesized with different architectures, including linear, hyperbranched polymers and gels. The relaxivities of the polymeric CAs were determined by NMR relaxometry, revealing an up to 5-fold increase in relaxivity (60 MHz, 310 K) for the linear polymers compared with the clinically used CA, Gd-DOTA. Moreover, hyperbranched polymers obtained from Gd(iii) crosslinkers, displayed even higher relaxivities up to 22.8 mM−1 s−1, approximately 8 times higher than that of Gd-DOTA (60 MHz, 310 K). A detailed NMRD study revealed that the enhanced relaxivities of the hyperbranched polymers were obtained by limiting the local motion of the crosslinked Gd(iii) chelate. The versatility of RAFT polymerization of Gd(iii) monomers and crosslinkers opens the doors to more advanced polymeric CAs capable of multimodal, bioresponsive or targeting properties. A new synthetic strategy for the preparation of efficient macromolecular MRI contrast agents is reported.![]()
Collapse
|
20
|
Optimizing the relaxivity at high fields: systematic variation of the rotational dynamics in polynuclear Gd-complexes based on the AAZTA ligand. Inorg Chem Front 2021. [DOI: 10.1039/d1qi00904d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A homogeneous series of polynuclear Gd-complexes (n = 1–8) based on a stable and bis-hydrated [Gd(AAZTA)]− chelate shows high relaxivity values at high fields (1.5–7 T), per Gd, particularly pronounced for the more rigid and compact members.
Collapse
|
21
|
Scrutinising the role of intramolecular hydrogen bonding in water exchange dynamics of Gd(iii) complexes. Dalton Trans 2021; 50:5506-5518. [DOI: 10.1039/d1dt00204j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The water exchange rate in GdIII-complexes bearing substituted acetophenone moieties is modulated by the ability of peripherical substituents to establish hydrogen bonds with the coordinated and/or second sphere water molecules.
Collapse
|
22
|
1H NMR Relaxometric Study of Chitosan-Based Nanogels Containing Mono- and Bis-Hydrated Gd(III) Chelates: Clues for MRI Probes of Improved Sensitivity. ACS APPLIED BIO MATERIALS 2020; 3:9065-9072. [PMID: 35019583 DOI: 10.1021/acsabm.0c01295] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Hydrogel nanoparticles composed of chitosan and hyaluronate and incorporating Gd-based MRI contrast agents with different hydration number (e.g., [Gd(DOTA)(H2O)]- and [Gd(AAZTA)(H2O)2]-) were prepared and fully characterized. In particular, 1H NMR relaxometric data, acquired as a function of temperature and applied magnetic field strength, were for the first time thoroughly analyzed using a theoretical model that includes the effects of a static zero-field splitting and an anisotropic molecular tumbling. The paramagnetic nanoparticles show excellent stability in aqueous solution for over 150 h and do not release the load of Gd(III) chelates. These nanoparticles exhibit enhanced efficacy (relaxivity) as relaxation agents, over 6 times that of the free complexes, thanks to the combination of a restricted molecular dynamics in the presence of a fast exchange of metal-bound water molecule(s) and between the water inside the nanogel and the bulk water. The knowledge of the molecular parameters that control the effectiveness of these MRI nanoprobes and those that limit their further increase will be crucial for the development of optimized systems with high sensitivity and stability.
Collapse
|
23
|
Selective functionalization of 6-amino-6-methyl-1,4-perhydrodiazepine for the synthesis of a library of polydentate chelators. Org Biomol Chem 2020; 18:5245-5252. [PMID: 32614034 DOI: 10.1039/d0ob00980f] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Polydentate chelators are an important part of an imaging probe, which consists of an agent that usually produces signals for imaging purposes connected to a targeting moiety. The goal of this study was to set up a generic protocol to prepare a library of polydentate ligands having a 6-amino-6-methyl-1,4-perhydrodiazepine (AMPED) core and able to chelate metal ions of interest for various diagnostic imaging techniques, including Magnetic Resonance Imaging (MRI), Positron Emission Tomography (PET) and Single-Photon Emission Computed Tomography (SPECT). These ions, among which we can include Mn(ii), Cu(ii), Al(iii) or Ga(iii), require penta- or hexa-dentate chelators for this purpose, and the AMPED scaffold has considerable potential to support various pendant arms for coordination of such ions. AMPED already has three amino nitrogen donors; thus, only two or three additional arms should be introduced to obtain penta- or hexa-dentate systems. This condition implies that symmetrical or asymmetrical structures have to be developed, depending on the functionalization of cyclic and exocyclic amines. Starting from easily available materials, we have designed a convenient protocol for the preparation of multiple AMPED-based ligands endowed with different characteristics, several of which were synthesized as examples.
Collapse
|
24
|
Acid-catalyzed proton exchange as a novel approach for relaxivity enhancement in Gd-HPDO3A-like complexes. Chem Sci 2020; 11:7829-7835. [PMID: 34123071 PMCID: PMC8163333 DOI: 10.1039/d0sc02174a] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
A current challenge in medical diagnostics is how to obtain high MRI relaxation enhancement using GdIII-based contrast agents (CAs) containing the minimum concentration of GdIII ions. We report that in GdHPDO3A-like complexes a primary amide group located in close proximity to the coordinated hydroxyl group can provide a strong relaxivity enhancement at slightly acidic pH. A maximum relaxivity of r1 = 9.8 mM−1 s−1 (20 MHz, 298 K) at acidic pH was achieved, which is more than double that of clinically approved MRI contrast agents under identical conditions. This effect was found to strongly depend on the number of amide protons, i.e. it decreases with a secondary amide group and almost completely vanishes with a tertiary amide. This relaxivity enhancement is attributed to an acid-catalyzed proton exchange process between the metal-coordinated OH group, the amide protons and second sphere water molecules. The mechanism and kinetics of the corresponding H+ assisted exchange process are discussed in detail and a novel simultaneous double-site proton exchange mechanism is proposed. Furthermore, 1H and 17O NMR relaxometry, Chemical Exchange Saturation Transfer (CEST) on the corresponding EuIII complexes, and thermodynamic and kinetic studies are reported. These highlight the optimal physico-chemical properties required to achieve high relaxivity with this series of GdIII-complexes. Thus, proton exchange provides an important opportunity to enhance the relaxivity of contrast agents, providing that labile protons close to the paramagnetic center can contribute. A novel GdHPDO3A-like complex featuring primary amide side chain induces extraordinary high relaxivity by virtue of a simultaneous double-site proton exchange mechanism under slight acidic conditions.![]()
Collapse
|
25
|
COVID-19 pneumonia in a kidney transplant recipient successfully treated with tocilizumab and hydroxychloroquine. Am J Transplant 2020; 20:1902-1906. [PMID: 32324331 PMCID: PMC7264495 DOI: 10.1111/ajt.15935] [Citation(s) in RCA: 72] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Revised: 04/13/2020] [Accepted: 04/15/2020] [Indexed: 01/25/2023]
Abstract
Coronavirus disease 2019 (COVID-19) pneumonia has been poorly reported in solid organ transplanted patients; prognosis is uncertain and best management unclear. We describe the case of a 61-year-old kidney transplant recipient with several comorbidities who was hospitalized and later received a diagnosis of COVID-19 pneumonia; the infection was successfully managed with the use of hydroxychloroquine and a single administration of tocilizumab, after immunosuppression reduction; the patient did not require mechanical ventilation. During the rapid spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, transplant clinicians should be readily informed about new cases of COVID-19 pneumonia in solid organ transplant recipients, with focus on therapeutic strategies employed and their outcome.
Collapse
|
26
|
Correction to Mn(II)-Based Lipidic Nanovesicles as High-Efficiency MRI Probes. ACS APPLIED BIO MATERIALS 2020; 3:3924. [PMID: 35029121 DOI: 10.1021/acsabm.0c00547] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
27
|
Combination of solid-state NMR and 1H NMR relaxometry for the study of intercalated saponite clays with the macrocyclic derivatives of Gd(iii) and Y(iii). Dalton Trans 2020; 49:6566-6571. [PMID: 32347275 DOI: 10.1039/d0dt01125h] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Positively charged Gd(iii) and Y(iii) complexes were intercalated in the gallery of a synthetic saponite. A combination of solid-state NMR and 1H NMR relaxometric investigations has been employed to characterize these hybrid systems. This enabled us to gain atomic level insights into the local environment of the chelates and to evaluate the interactions of the metal species with the co-intercalated water molecules.
Collapse
|
28
|
Abstract
Although nowadays there is a renewed and growing interest in Mn-based contrast agents, there are only few studies dealing with Mn-based lipophilic nanoparticles and how they may be optimized as MRI contrast agents. Three amphiphilic paramagnetic Mn(II) complexes based on derivatives of EDTA and 1,4-DO2A were used for the preparation of lipidic nanoparticles. The length and position of the aliphatic chains were found to control whether either vesicular liposomes, nonvesicular bicelles, or a mixture of both was produced as well as the size and morphology of phospholipid-based self-assembling nanoaggregates. These differences determine whether hydrophilic Gd-based contrast agents or fluorescent dyes can be entrapped in the aqueous core of the nanoaggregate. Structural characterization was performed by cryo-TEM. Detailed 1H NMR relaxometric analyses were carried out on all systems. The effect of entrapping gadoteridol in the aqueous core (where present) was studied by preparing diamagnetic amphiphilic Zn(II) analogues. In the case of homogeneous systems, the data were also fitted to obtain the relaxometric parameters for comparison with literature data. The results of these studies demonstrate enhanced relaxivity of the nanoaggregates with respect to monomeric analogues. This work allowed us to understand how to control the formation of different types of nanovesicles (liposomes, bicelles, and micelles), optimize their MRI contrast, and provide different in vivo biodistribution characteristics.
Collapse
|
29
|
Room Temperature Al 18 F Labeling of 2-Aminomethylpiperidine-Based Chelators for PET Imaging. ChemMedChem 2020; 15:284-292. [PMID: 31830368 DOI: 10.1002/cmdc.201900652] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Revised: 12/02/2019] [Indexed: 01/14/2023]
Abstract
Positron emission tomography (PET) is a non-invasive molecular imaging technology that is constantly expanding, with a high demand for specific antibody-derived imaging probes. The use of tracers based on temperature-sensitive molecules (i. e. Fab, svFab, nanobodies) is increasing and has led us to design a class of chelators based on the structure of 2-aminomethylpiperidine (AMP) with acetic and/or hydroxybenzyl pendant arms (2-AMPTA, NHB-2-AMPDA, and 2-AMPDA-HB), which were investigated as such for {Al18 F}2+ -core chelation efficiency. All the compounds were characterized by HPLC-MS analysis and NMR spectroscopy. The AlF-18 labeling reactions were performed under various conditions (pH/temperature), and the radiolabeled chelates were purified and characterized by radio-TLC and radio-HPLC. The stability of labeled chelates was investigated up to 240 min in human serum (HS), EDTA 5 mM, PBS and 0.9 % NaCl solutions. The in vivo stability of [Al18 F(2-AMPDA-HB)]- was assessed in healthy nude mice (n=6). Radiochemical yields between 55 % and 81 % were obtained at pH 5 and room temperature. High stability in HS was measured for [Al18 F(2-AMPDA-HB)]- , with 90 % of F-18 complexed after 120 min. High stability in vivo, rapid hepatobiliary and renal excretion, with low accumulation of free F-18 in bones were measured. Thus, this new Al18 F-chelator may have a great impact on immuno-PET radiopharmacy, by facilitating the development of new fluorine-18-labeled heat-sensitive biomolecules.
Collapse
|
30
|
Combined NMR, DFT and X-ray studies highlight structural and hydration changes of [Ln(AAZTA)]− complexes across the series. Inorg Chem Front 2020. [DOI: 10.1039/c9qi01442j] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
1H NMR, CEST, DFT and X-ray studies reveal that [Ln(AAZTA)]− chelates experience a transition across the Ln(iii) series from fast-exchanging, bisaqua 9-coordinate species, to slow-exchanging monoaqua 8-coordinate structures.
Collapse
|
31
|
Photoacoustic ratiometric assessment of mitoxantrone release from theranostic ICG-conjugated mesoporous silica nanoparticles. NANOSCALE 2019; 11:18031-18036. [PMID: 31570915 DOI: 10.1039/c9nr06524e] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
A theranostic nanosystem based on indocyanine green (ICG) covalently conjugated to mesoporous silica nanoparticles (MSNs) loaded with the anticancer drug mitoxantrone (MTX) is proposed as an innovative photoacoustic probe. Taking advantage of the characteristic PA signal displayed by both ICG and MTX, a PA-ratiometric approach was applied to assess the drug release profile from the MSNs. After complete in vitro characterization of the nanoprobe, a proof-of-concept study has been carried out in tumour-bearing mice to evaluate in vivo its effectiveness for cancer imaging and chemotherapeutic agent delivery.
Collapse
|
32
|
A Porous Carbon with Excellent Gas Storage Properties from Waste Polystyrene. NANOMATERIALS 2019; 9:nano9050726. [PMID: 31083428 PMCID: PMC6567234 DOI: 10.3390/nano9050726] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 04/30/2019] [Accepted: 04/30/2019] [Indexed: 01/19/2023]
Abstract
In this paper, we describe the synthesis and gas adsorption properties of a porous carbonaceous material, obtained from commercial expanded polystyrene. The first step consists of the Friedel-Craft reaction of the dissolved polystyrene chains with a bridging agent to form a highly-crosslinked polymer, with permanent porosity of 0.7 cm 3 /g; then, this polymer is treated with potassium hydroxide at a high temperature to produce a carbon material with a porous volume larger than 1.4 cm 3 / g and a distribution of ultramicro-, micro-, and mesopores. After characterization of the porous carbon and determination of the bulk density, the methane uptake was measured using a volumetric apparatus to pressures up to 30 bar. The equilibrium adsorption isotherm obtained is among the highest ever reported for this kind of material. The interest of this product lies both in its excellent performance and in the virtually costless starting material.
Collapse
|
33
|
On the Gas Storage Properties of 3D Porous Carbons Derived from Hyper-Crosslinked Polymers. Polymers (Basel) 2019; 11:polym11040588. [PMID: 30960572 PMCID: PMC6523183 DOI: 10.3390/polym11040588] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2019] [Revised: 03/11/2019] [Accepted: 03/13/2019] [Indexed: 11/21/2022] Open
Abstract
The preparation of porous carbons by post-synthesis treatment of hypercrosslinked polymers is described, with a careful physico-chemical characterization, to obtain new materials for gas storage and separation. Different procedures, based on chemical and thermal activations, are considered; they include thermal treatment at 380 °C, and chemical activation with KOH followed by thermal treatment at 750 or 800 °C; the resulting materials are carefully characterized in their structural and textural properties. The thermal treatment at temperature below decomposition (380 °C) maintains the polymer structure, removing the side-products of the polymerization entrapped in the pores and improving the textural properties. On the other hand, the carbonization leads to a different material, enhancing both surface area and total pore volume—the textural properties of the final porous carbons are affected by the activation procedure and by the starting polymer. Different chemical activation methods and temperatures lead to different carbons with BET surface area ranging between 2318 and 2975 m2/g and pore volume up to 1.30 cc/g. The wise choice of the carbonization treatment allows the final textural properties to be finely tuned by increasing either the narrow pore fraction or the micro- and mesoporous volume. High pressure gas adsorption measurements of methane, hydrogen, and carbon dioxide of the most promising material are investigated, and the storage capacity for methane is measured and discussed.
Collapse
|
34
|
Modifying LnHPDO3A Chelates for Improved
T
1
and CEST MRI Applications. Chemistry 2019; 25:4184-4193. [DOI: 10.1002/chem.201806023] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Indexed: 12/14/2022]
|
35
|
Accelerating water exchange in GdIII–DO3A-derivatives by favouring the dissociative mechanism through hydrogen bonding. Chem Commun (Camb) 2019; 55:513-516. [DOI: 10.1039/c8cc08556k] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The water exchange rate in GdIII-complexes increases by one order of magnitude due to H-bonding between the phenol(ate) group and the water molecules involved in the dissociative exchange mechanism.
Collapse
|
36
|
Multifunctional Gd-based mesoporous silica nanotheranostic for anticancer drug delivery. J Mater Chem B 2019. [DOI: 10.1039/c9tb00375d] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
A theranostic MRI nanoprobe based on mesoporous silica nanoparticles with attached stable Gd-complexes with high relaxivity, rhodamine dyes, PEG and cyclooctyne moieties was synthesized and loaded with mitoxantrone for bio-orthogonal targeted anticancer drug delivery.
Collapse
|
37
|
|
38
|
Synthesis, identification and quantification of oligomers from polyester coatings for metal packaging. J Chromatogr A 2018; 1578:15-27. [PMID: 30314684 DOI: 10.1016/j.chroma.2018.10.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Revised: 06/13/2018] [Accepted: 10/02/2018] [Indexed: 11/26/2022]
Abstract
Polyester can coatings protect both food and packaging from mutual contamination. Even though, can coatings may release Non-Intentionally Added Substances (NIAS) in addition to Intentionally Added Substances (IAS). As NIAS are mainly constituted by cyclic or linear side products that are formed during the polymerization process, we focused our attention on these oligomeric species of molecular weight <1000 Da. These oligomers were obtained from two different polyester resins, each synthesized from four monomers (two phthalic acids and two diols), and from the corresponding final enamel can coatings using ethanol at 95% and 50% at 60 °C for 4 h and 10 days, respectively, as food simulants. HPLC-ESI-MS analysis on the extracts allowed identifying various cyclic and linear oligomers. For the conclusive identification of the different oligomers and their isomeric structures, ad hoc standards were synthesized by acylation reaction between alkyl diols and phthaloyl chlorides. By comparison of 1H NMR spectra, linear and cyclic oligomers were characterized by finding the major presence of 2 + 2 cyclic compounds. The 16 synthesized standards, 4 linear and 12 cyclic compounds were used to establish a method for quantification of linear and cyclic oligomers in enamel migration samples by micro HPLC-high-resolution MS (HRMS). The results showed no significant differences between the amounts of cyclic oligomers extracted with both ethanol concentrations (50 and 95%) and time contact. The extracts showed only a small amount of linear compounds and a prevalence of 2 + 2 cyclic oligomers. The work shows the great importance of the synthesis of specific standards to allow exact quantification in food contact material migrates.
Collapse
|
39
|
Preclinical Evaluation of the Hsp70 Peptide Tracer TPP-PEG 24-DFO[ 89Zr] for Tumor-Specific PET/CT Imaging. Cancer Res 2018; 78:6268-6281. [PMID: 30228173 DOI: 10.1158/0008-5472.can-18-0707] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Revised: 06/04/2018] [Accepted: 09/14/2018] [Indexed: 11/16/2022]
Abstract
High precision in vivo PET/CT imaging of solid tumors improves diagnostic credibility and clinical outcome of patients. An epitope of the oligomerization domain of Hsp70 is exclusively exposed on the membrane of a large variety of tumor types, but not on normal cells, and thus provides a universal tumor-specific target. Here we developed a novel PET tracer TPP-PEG24-DFO[89Zr] based on the tumor cell-penetrating peptide probe TPP, which specifically recognizes membrane Hsp70 (mHsp70) on tumor cells. The implemented PEG24 moiety supported tracer stability and improved biodistribution characteristics in vivo The K d of the tracer ranged in the low nanomolar range (18.9 ± 11.3 nmol/L). Fluorescein isothiocyanate (FITC)-labeled derivatives TPP-[FITC] and TPP-PEG24-[FITC] revealed comparable and specific binding to mHsp70-positive 4T1, 4T1+, a derivative of the 4T1 cell line sorted for high Hsp70 expression, and CT26 tumor cells, but not to mHsp70-negative normal fibroblasts. The rapid internalization kinetics of mHsp70 into the cytosol and the favorable biodistribution of the peptide-based tracer TPP-PEG24-DFO[89Zr] in vivo enabled a tumor-specific accumulation with a high tumor-to-background contrast and renal body clearance. The tumor-specific enrichment of the tracer in 4T1+ (6.2 ± 1.1%ID/g), 4T1 (4.3 ± 0.7%ID/g), and CT26 (2.6 ± 0.6%ID/g) mouse tumors with very high, high, and intermediate mHsp70 densities, respectively, reflected mHsp70 expression profiles of the different tumor types, whereas benign mHsp70-negative fibroblastic hyperplasia showed no tracer accumulation (0.2 ± 0.03%ID/g). The ability of our chemically optimized peptide-based tracer TPP-PEG24-DFO[89Zr] to detect mHsp70 in vivo suggests its broad applicability in targeting and imaging with high specificity for any tumor type that exhibits surface expression of Hsp70.Significance: A novel peptide-based PET tracer against the oligomerization domain of Hsp70 has potential for universal tumor-specific imaging in vivo across many tumor type. Cancer Res; 78(21); 6268-81. ©2018 AACR.
Collapse
|
40
|
Abstract
We report two novel macrocyclic ligands based on the 1,4-DO2AM platform (1,4-DO2AM = 2,2'-(1,4,7,10-tetraazacyclododecane-1,4-diyl)diacetamide) and containing two benzyl groups attached either to the nitrogen atoms of the macrocyclic unit (1,4-BzDO2AM) or to the amide pendant arms (1,4-DO2AMBz). The protonation constants of the ligands and the stability constants of their Mn2+ complexes were determined using pH potentiometry. The introduction of benzyl groups results in a slight decrease of the stability constants of the Mn2+ complexes and a slight increase of their acid-catalysed dissociation reactions. A detailed relaxometric characterisation of the complexes using nuclear magnetic dispersion relaxation (NMRD) and 17O NMR studies indicated that the increase in molecular weight associated with the presence of benzyl groups results in a remarkable increase of proton relaxivities r1p, which take values of 3.8, 3.5 and 2.5 mM-1 s-1 for [Mn(1,4-BzDO2AM)]2+, [Mn(1,4-DO2AMBz)]2+ and [Mn(1,4-DO2AM)]2+ (at 25 °C and 20 MHz). The [Mn(1,4-BzDO2AM)]2+ and [Mn(1,4-DO2AMBz)]2+ complexes form relatively strong adducts with Human Serum Albumin (HSA) with association constants of (3.9 ± 0.6) × 103 and (2.0 ± 0.3) × 103 M-1, respectively. The interaction with the protein slows down the rotational tumbling of the complex in solution, which results in adducts endowed with remarkably high proton relaxivities (r1pb = 18.5 ± 0.7 and 27.4 ± 1.4 mM-1 s-1 for [Mn(1,4-BzDO2AM)]2+ and [Mn(1,4-DO2AMBz)]2+, respectively).
Collapse
|
41
|
Efficient Route to Label Mesenchymal Stromal Cell-Derived Extracellular Vesicles. ACS OMEGA 2018; 3:8097-8103. [PMID: 30087935 PMCID: PMC6072237 DOI: 10.1021/acsomega.8b00908] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Accepted: 07/06/2018] [Indexed: 05/23/2023]
Abstract
Recent research results report that extracellular vesicles (EVs) have a central role in both physiological and pathological processes involving intercellular communication. Herein, a simple EVs labeling procedure based on the metabolic labeling of secreting cells (mesenchymal stroma cells, MSCs) with a fluorescein-containing bio-orthogonal dye is described. This procedure was carried out by incubating cells for 72 h with tetraacetylated N-azidoacetyl-d-mannosamine (Ac4ManNAz), a modified sugar containing an azido group that, upon incorporation on the external surface of the cytoplasmatic cell membrane, is specifically conjugated with cyclooctyne-modified fluorescein isothiocyanate (ADIBO-FITC). MSCs released fluorescent EVs did not need any further purification. Finally, cellular uptake and tracking of the fluorescein-labeled EVs were successfully assessed by targeting experiments with MSCs. The method appears of general applicability and it may be very useful opening new horizon on diagnostic and therapeutic protocols exploiting EVs.
Collapse
|
42
|
|
43
|
Abstract
Novel paramagnetic lanthanide-exchanged saponite clays, bearing in the interlamellar region positively charged Gd3+-complexes, were synthesized using a hydrothermal approach followed by a classical ion exchange reaction. A detailed characterization was performed to assess the physico-chemical properties of the samples, which showed a hydrodynamic diameter between 50 and 90 nm and good thermal stability. 1H-NMR relaxometric studies in aqueous solution as a function of magnetic field and temperature were carried out to evaluate the local chemical environment of the intercalated paramagnetic centres and their interaction with water molecules. The data indicate a strong interaction of the confined complexes with the lamellae, resulting in a restriction of the local rotational dynamics and of the exchange process of water molecules between the inner coordination sphere of Gd3+ and the bulk. The stability over time in aqueous solutions of varying complexity was also studied by relaxometric techniques.
Collapse
|
44
|
PO-517 Peptide-based diagnostic in vivo targeting of membrane Hsp70 positive tumours. ESMO Open 2018. [DOI: 10.1136/esmoopen-2018-eacr25.532] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
|
45
|
Optimizing the Relaxivity of MRI Probes at High Magnetic Field Strengths With Binuclear Gd III Complexes. Front Chem 2018; 6:158. [PMID: 29868561 PMCID: PMC5962812 DOI: 10.3389/fchem.2018.00158] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Accepted: 04/19/2018] [Indexed: 12/05/2022] Open
Abstract
The key criteria to optimize the relaxivity of a Gd(III) contrast agent at high fields (defined as the region ≥ 1.5 T) can be summarized as follows: (i) the occurrence of a rotational correlation time τR in the range of ca. 0.2–0.5 ns; (ii) the rate of water exchange is not critical, but a τM < 100 ns is preferred; (iii) a relevant contribution from water molecules in the second sphere of hydration. In addition, the use of macrocycle-based systems ensures the formation of thermodynamically and kinetically stable Gd(III) complexes. Binuclear Gd(III) complexes could potentially meet these requirements. Their efficiency depends primarily on the degree of flexibility of the linker connecting the two monomeric units, the absence of local motions and the presence of contribution from the second sphere water molecules. With the aim to maximize relaxivity (per Gd) over a wide range of magnetic field strengths, two binuclear Gd(III) chelates derived from the well-known macrocyclic systems DOTA-monopropionamide and HPDO3A (Gd2L1 and Gd2L2, respectively) were synthesized through a multistep synthesis. Chemical Exchange Saturation Transfer (CEST) experiments carried out on Eu2L2 at different pH showed the occurrence of a CEST effect at acidic pH that disappears at neutral pH, associated with the deprotonation of the hydroxyl groups. Then, a complete 1H and 17O NMR relaxometric study was carried out in order to evaluate the parameters that govern the relaxivity associated with these complexes. The relaxivities of Gd2L1 and Gd2L2 (20 MHz, 298 K) are 8.7 and 9.5 mM−1 s−1, respectively, +77% and +106% higher than the relaxivity values of the corresponding mononuclear GdDOTAMAP-En and GdHPDO3A complexes. A significant contribution of second sphere water molecules was accounted for the strong relaxivity enhancement of Gd2L2. MR phantom images of the dinuclear complexes compared to GdHPDO3A, recorded at 7 T, confirmed the superiority of Gd2L2. Finally, ab initio (DFT) calculations were performed to obtain information about the solution structure of the dinuclear complexes.
Collapse
|
46
|
Relaxivity Enhancement of Ditopic Bishydrated Gadolinium(III) Complexes Conjugated to Mesoporous Silica Nanoparticles. Eur J Inorg Chem 2018. [DOI: 10.1002/ejic.201800041] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
|
47
|
Macrocyclic trinuclear gadolinium( iii) complexes: the influence of the linker flexibility on the relaxometric properties. NEW J CHEM 2018. [DOI: 10.1039/c7nj04696k] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The flexibility/rigidity of the linker causes different relaxometric behavior in both mononuclear and trinuclear GdIII complexes based on DO3A-like structures.
Collapse
|
48
|
Supramolecular assemblies based on amphiphilic Mn2+-complexes as high relaxivity MRI probes. Dalton Trans 2018; 47:10660-10670. [DOI: 10.1039/c8dt01250d] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The Mn2+ complexes of amphiphilic derivatives of EDTA and 1,4-DO2A ligands show a strong increase in relaxivity upon micellar aggregation and human serum albumin binding.
Collapse
|
49
|
Abstract
An unexpectedly slow water exchange rate makes [Yb(AAZTA)(H2O)]− a ParaCEST agent.
Collapse
|
50
|
Developing High Field MRI Contrast Agents by Tuning the Rotational Dynamics: Bisaqua GdAAZTA-based Dendrimers. Isr J Chem 2017. [DOI: 10.1002/ijch.201700041] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|