Purpose To evaluate the speciation of gadolinium-containing species after multiple administrations of the gadolinium-based contrast agents (GBCAs) gadodiamide and gadoteridol and to quantify the ...amount of intact gadolinium complexes and insoluble gadolinium-containing species. Materials and Methods A total dose of 13.2 mmol per kilogram of body weight of each GBCA was administered in healthy Wistar rats over a period of 8 weeks. Three days after the final administration, rats were sacrificed, and the brains were excised and divided into three portions. Each portion of brain homogenate was divided into two parts, one for determination of the total gadolinium concentration with inductively coupled plasma mass spectrometry and one for determination of the amount of intact GBCA and gadolinium-containing insoluble species. Relaxometric measurements of gadodiamide and gadolinium trichloride in the presence of polysialic acid were also performed. Results The mean total gadolinium concentrations for gadodiamide and gadoteridol, respectively, were 0.317 μg/g ± 0.060 (standard deviation) and 0.048 μg/g ± 0.004 in the cortex, 0.418 μg/g ± 0.078 and 0.051 μg/g ± 0.009 in the subcortical brain, and 0.781 μg/g ± 0.079 and 0.061 μg/g ± 0.012 in the cerebellum. Gadoteridol comprised 100% of the gadolinium species found in rats treated with gadoteridol. In rats treated with gadodiamide, the largest part of gadolinium retained in brain tissue was insoluble species. In the cerebellum, the amount of intact gadodiamide accounts for 18.2% ± 10.6 of the total gadolinium found therein. The mass balance found for gadolinium implies the occurrence of other soluble gadolinium-containing species (approximately 30%). The relaxivity of the gadolinium polysialic acid species formed in vitro was 97.8 mM/sec at 1.5 T and 298 K. Conclusion Gadoteridol was far less retained, and the entire detected gadolinium was intact soluble GBCA, while gadodiamide yielded both soluble and insoluble gadolinium-containing species, with insoluble species dominating.
RSNA, 2017 Online supplemental material is available for this article.
The assessment of unregulated level of enzyme activity is a crucial parameter for early diagnoses in a wide range of pathologies. In this study, we propose the use of electron paramagnetic resonance ...(EPR) as an easy method to probe carboxylesterase (CE) enzymatic activity in vitro. For this application, were synthesized two amphiphilic, nitroxide containing esters, namely Tempo‐C12 (T‐C12) and Tempo‐2‐C12 (T‐2‐C12). They exhibit low solubility in water and form stable micelles in which the radicals are EPR almost silent, but the hydrolysis of the ester bond yields narrows and intense EPR signals. The intensity of the EPR signals is proportional to the enzymatic activity. CEs1, CEs2 and esterase from porcine liver (PLE) were investigated. The obtained results show that T‐C12 and T‐2‐C12‐containing systems display a much higher selectivity toward the CEs2, with a Limit of Detection of the same order of those ones obtained with optical methods.
In this study are reported two off/on EPR probes containing a nitroxide radical to study the enzymatic activity of carboxylesterases. Thanks to their low solubility in water, they aggregate to form stable micelles, which makes the probes EPR silent. In presence of the esterases enzymes the nitroxide radicals are release from the micelle giving an off/on transition and intense signal.
The most prominent pathophysiological hallmark of Alzheimer's disease is the aggregation of amyloid-β (Aβ) peptides into senile plaques. Curcumin and its derivatives exhibit a high affinity for ...binding to Aβ fibrils, effectively inhibiting their growth. This property holds promise for both therapeutic applications and diagnostic molecular imaging. In this study, curcumin was functionalized with perfluoro-tert-butyl groups to create candidate molecular probes specifically targeted to Aβ fibrils for use in 19F-magnetic resonance imaging. Two types of fluorinated derivatives were considered: mono-substituted (containing nine fluorine atoms per molecule) and disubstituted (containing eighteen fluorine atoms). The linker connecting the perfluoro moiety with the curcumin scaffold was evaluated for its impact on binding affinity and water solubility. All mono-substituted compounds and one disubstituted compound exhibited a binding affinity toward Aβ fibrils on the same order of magnitude as reference curcumin. The insertion of a charged carboxylate group into the linker enhanced the water solubility of the probes. Compound Curc-Glu-F9 (with one l-glutamyl moiety and a perfluoro-tert-butyl group), showed the best properties in terms of binding affinity towards Aβ fibrils, water solubility, and intensity of the 19F-NMR signal in the Aβ oligomer bound form.
Optoacoustic imaging emerged in early 1990s as a new biomedical imaging technology that generates images by illuminating tissues with short laser pulses and detecting resulting ultrasound waves. This ...technique takes advantage of the spectroscopic approach to molecular imaging, and delivers high-resolution images in the depth of tissue. Resolution of the optoacoustic imaging is scalable, so that biomedical systems from cellular organelles to large organs can be visualized and, more importantly, characterized based on their optical absorption coefficient, which is proportional to the concentration of absorbing chromophores. Optoacoustic imaging was shown to be useful in both preclinical research using small animal models and in clinical applications. Applications in the field of molecular imaging offer abundant opportunities for the development of highly specific and effective contrast agents for quantitative optoacoustic imaging. Recent efforts are being made in the direction of nontoxic biodegradable contrast agents (such as nanoparticles made of melanin) that are potentially applicable in clinical optoacoustic imaging. In order to increase the efficiency and specificity of contrast agents and probes, they need to be made smart and capable of controlled accumulation in the target cells. This review was written in recognition of the potential breakthroughs in medical optoacoustic imaging that can be enabled by efficient and nontoxic melanin-based optoacoustic contrast agents.
Purpose
Prostate cancer (PCa), the most widespread male cancer in western countries, is generally eradicated by surgery, especially if localized. However, during surgical procedures, it is not always ...possible to identify malignant tissues by visual inspection. Among the possible consequences, there is the formation of positive surgical margins, often associated with recurrence. In this work, the gastrin-releasing peptide receptor (GRPR), overexpressed in the prostatic carcinoma and not in healthy tissues or in benign hyperplasia (BPH), is proposed as target molecule to design a novel near-infrared fluorescent (NIRF) probe for image-guided prostatectomy.
Procedures
The NIRF dye Sulfo-Cy5.5 was conjugated to a Bombesin-like peptide (BBN), targeting GRPR. The final product, called BBN-Cy5.5, was characterized and tested
in vitro
on PC-3, DU145, and LnCAP cell lines, using unconjugated Sulfo-Cy5.5 as control.
In vivo
biodistribution studies were performed by optical imaging in PC-3 tumor-bearing and healthy mice. Finally, simulation of the surgical protocol was carried out.
Results
BBN-Cy5.5 showed high water solubility and a good relative quantum yield. The ability of the probe to recognize the GRPR, highly expressed in PC-3 cells, was tested both
in vitro
and
in vivo
, where a significant tumor accumulation was achieved 24 h post-injection. Furthermore, a distinguishable fluorescent signal was visible in mice bearing PCa, when the surgery was simulated. By contrast, low signal was found in healthy or BPH-affected mice.
Conclusions
This work proposes a new NIRF probe ideal to target GRPR, biomarker of PCa. The promising data obtained suggest that the dye could allow the real-time intraoperative visualization of prostate cancer.
A total of 20% to 50% of prostate cancer (PCa) patients leave the surgery room with positive tumour margins. The intraoperative combination of fluorescence guided surgery (FGS) and photodynamic ...therapy (PDT) may be very helpful for improving tumour margin delineation and cancer therapy. PSMA is a transmembrane protein overexpressed in 90−100% of PCa cells. The goal of this work is the development of a PSMA-targeted Near InfraRed Fluorescent probe to offer the surgeon a valuable intraoperative tool for allowing a complete tumour removal, implemented with the possibility of using PDT to kill the eventual not resected cancer cells. PSMA-617 binding motif was conjugated to IRDye700DX-NHS and the conjugation did not affect the photophysical characteristics of the fluorophore. The affinity of IRDye700DX-PSMA-617 towards PCa cells followed the order of their PSMA expression, i.e., PC3-PIP > LNCaP > PC3, PC3-FLU. NIRF imaging showed a significant PC3-PIP tumour uptake after the injection of 1 or 5 nmol with a maximum tumour-to-muscle ratio (ca. 60) observed for both doses 24 h post-injection. Importantly, urine, healthy prostate, and the bladder were not fluorescent at 24 h post-injection. Flow cytometry and confocal images highlighted a co-localization of PSMA+ cells with IRDye700DX-PSMA uptake. Very interestingly, ex vivo analysis on a tumour specimen highlighted a significant PSMA expression by tumour-associated macrophages, likely attributable to extracellular vesicles secreted by the PSMA(+) tumour cells. FGS proved that IRDye700DX-PSMA was able to easily delineate tumour margins. PDT experiments showed a concentration-dependent decrease in cell viability (from 75% at 10 nM to 12% at 500 nM), whereas controls did not show any cytotoxicity. PC3-PIP tumour-bearing mice subjected to photodynamic therapy showed a delayed tumour growth. In conclusion, a novel PSMA-targeted NIRF dye with dual imaging-PDT capabilities was synthesized and displayed superior specificity compared to other small PSMA targeted molecules.
Purpose
Prostate cancer (PCa) is the most widespread tumor affecting males in Western countries. We propose a novel MRI molecular tetrameric probe based on the heptadentate gadolinium (Gd)‐AAZTA ...(6‐amino‐6‐methylperhydro‐1,4‐diazepinetetraacetic acid) that is able to in vivo detect PCa through the recognition of the fibrin–fibronectin (FB–FN) complex.
Methods
The peptide CREKA (Cys‐Arg‐Glu‐Lys‐Ala), targeting the FB–FN complex in the reactive stroma of the tumor, was synthesized by solid phase peptide synthesis (SPPS) and conjugated to the tetramer dL‐(Gd‐AAZTA)4. The resulting probe was characterized by 1H relaxometry, tested in vitro on FB clots and in vivo on an orthotopic mouse model of PCa.
Results
CREKA‐dL‐(Gd‐AAZTA)4 showed a remarkable relaxivity of 18.2 mMGd-1s−1 (0.47 T, 25°C) because of the presence of 2 water molecules (q = 2) in the inner coordination sphere of each Gd3+ ion, whose rotational motion (τR) is lengthened as the result of the relatively high molecular weight. The probe displayed a detectable affinity for plasma‐derived FB clots. On intravenous injection of the probe in an orthotopic mouse model of PCa, a significant increase in the prostate T1 contrast (~40%) was observed. The MRI signal appears statistically higher either with respect to the one observed for the control probes and to the one detected when CREKA‐dL‐(Gd‐AAZTA)4 was administered to healthy animals.
Conclusions
This study demonstrated the ability of the CREKA‐dL‐(Gd‐AAZTA)4 probe to specifically localize in prostate tumor after injection. The high relaxivity of the probe allows the reduction of the injected dose to 20 µmolGd/kg, yielding a good in vivo contrast enhancement in the region of prostate tumor.
Herein, the synthesis and an extensive characterization of two novel Gd(AAZTA) (AAZTA=6‐amino‐6‐methylperhydro‐1,4‐diazepine tetra acetic acid) derivatives functionalized with short (C2 and C4) ...n‐alkyl acid functions are reported. The carboxylate functionality is the site for further conjugations for the design of more specific contrast agents (CAs). Interestingly, it has been found that the synthesized complexes display enhanced properties for use as MRI contrast agents on their own. The stability constants determined by using potentiometric titration and UV/Vis spectrophotometry were slightly higher than the one reported for the parent Gd(AAZTA) complex. This observation might be accounted for by the larger sigma‐electron donation of the acyl substituents with respect to the one provided by the methyl group in the parent complex. As far as concerns the kinetic stability, transmetallation experiments with endogenous ions (e.g. Cu2+) implied that the Gd3+ ions present in these Gd(AAZTA) derivatives show somewhat smaller susceptibility to chemical exchange towards these ions at 25 °C, close to the physiological condition. The 1H NMR spectra of the complexes with EuIII and YbIII displayed a set of signals consistent with half the number of methylene protons present on each ligand. The number of resonances was invariant over a large range of temperatures, suggesting the occurrence of a fast interconversion between structural isomers. The relaxivity values (298 K, 20 MHz) were consistent with q=2 being equal to 8.8 mm−1 s−1 for the C2 derivative and 9.4 mm−1 s−1 for the C4 one, that is, sensibly larger than the one reported for Gd(AAZTA) (7.1 mm−1 s−1). Variable‐temperature (VT)‐T2 17O NMR measurements showed, for both complexes, the presence of two populations of coordinated water molecules, one in fast and one in slow exchange with the bulk water. As the high‐resolution 1H NMR spectra of the analogs with EuIII and YbIII did not show the occurrence of distinct isomers (as frequently observed in other macrocyclic lanthanide(III)‐containing complexes), we surmised the presence of two fast‐interconverting isomers in solution. The analysis of the 17O NMR VT‐T2 profiles versus temperature allowed their relative molar fraction to be established as 35 % for the isomer with the fast exchanging water and 65 % for the isomer with the water molecules in slower exchange. Finally, 1H NMRD profiles over an extended range of applied magnetic field strengths have been satisfactory fitted on the basis of the occurrence of the two interconverting species.
The good properties of Gd(AAZTA) (AAZTA=6‐amino‐6‐methylperhydro‐1,4‐diazepine tetra acetic acid) as a MRI contrast agent are further improved by simply attaching a short n‐alkyl function on the ligand's surface. The variable temperature (VT)‐T2 measurements of the 17OH2 resonance suggest the occurrence of two interconverting isomers in solution characterized by very different exchange rates of the coordinated water molecules.
The N-capping region of an α-helix is a short N-terminal amino acid stretch that contributes to nucleate and stabilize the helical structure. In the VEGF mimetic helical peptide QK, the N-capping ...region was previously demonstrated to be a key factor of QK helical folding. In this paper, we explored the effect of the chiral inversion of the N-capping sequence on QK folding, performing conformational analysis in solution by circular dichroism and NMR spectroscopy. The effect of such a modification on QK stability in serum and the proliferative effect were also evaluated.
Leukemia is a type of hematopoietic stem/progenitor cell malignancy characterized by the accumulation of immature cells in the blood and bone marrow. Treatment strategies mainly rely on the ...administration of chemotherapeutic agents, which, unfortunately, are known for their high toxicity and side effects. The concept of targeted therapy as magic bullet was introduced by Paul Erlich about 100 years ago, to inspire new therapies able to tackle the disadvantages of chemotherapeutic agents. Currently, nanoparticles are considered viable options in the treatment of different types of cancer, including leukemia. The main advantages associated with the use of these nanocarriers summarized as follows: i) they may be designed to target leukemic cells selectively; ii) they invariably enhance bioavailability and blood circulation half-life; iii) their mode of action is expected to reduce side effects. FDA approval of many nanocarriers for treatment of relapsed or refractory leukemia and the desired results extend their application in clinics. In the present review, different types of nanocarriers, their capability in targeting leukemic cells, and the latest preclinical and clinical data are discussed.
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