99mTc-roxifiban: a potential molecular imaging agent for the detection and localization of acute venous thrombosis

TrisOxine abiotic siderophores for technetium complexation: radiolabeling and biodistribution studies

BACKGROUND

Despite the development of positron emission tomography (PET), single photon emission computed tomography (SPECT) still accounts for around 80% of all examinations performed in nuclear medicine departments. The search for new radiotracers or chelating agents for Technetium-99m is therefore still ongoing. O-TRENSOX and O-TRENOX two synthetic siderophores would be good candidates for this purpose as they are hexadentate ligands based on the very versatile and efficient 8-hydroxyquinoline chelating subunit. First, the radiolabeling of O-TRENOX and O-TRENSOX with 99mTc was investigated. Different parameters such as the quantity of chelating agent, type of reducing agent, pH and temperature of the reaction mixture were adjusted in order to find the best radiolabeling conditions. Then an assessment of the partition coefficient by measuring the distribution of each radiosynthesized complex between octanol and phosphate-buffered saline was realized. The complex's charge was evaluated on three different celluloses (neutral, negatively charged P81 and positively charged DE81), and finally in vivo studies with biodistribution and SPECT imaging of [99mTc]Tc-O-TRENOX and [99mTc]Tc-O-TRENSOX were performed.

RESULTS

The radiolabeling studies showed a rapid and efficient complexation of 99mTc with both chelating agents. Using tin pyrophosphate as the reducing agent and a minimum of 100 nmol of ligand, we obtained the [99mTc]Tc-O-TRENOX complex with a radiochemical purity of more than 98% and the [99mTc]Tc-O-TRENSOX complex with one above 97% at room temperature within 5 min. [99mTc]Tc-O-TRENOX complex was lipophilic and neutral, leading to a hepatobiliary elimination in mice. On the contrary, the [99mTc]Tc-O-TRENSOX complex was found to be hydrophilic and negatively charged. This was confirmed by a predominantly renal elimination in mice.

CONCLUSIONS

These encouraging results allow us to consider the O-TRENOX/99mTc and O-TRENSOX/99mTc complexes as serious candidates for SPECT imaging chelators. This study should be continued by conjugating these tris-oxine ligands to peptides or antibodies and comparing them with the other bifunctional agents used with Tc.

99mTc-linezolid as a radiotracer for brain abscess: Labeling, in silico docking, and biodistribution studies

Brain abscess is a life-threatening condition that requires a timely and accurate diagnosis. In this study, linezolid, an oxazolidinone antibiotic, was labeled with technetium-99m according to the stannous chloride method. The labeling reaction factors were studied and optimized to achieve a high yield (97.4 ± 2.3%). The 99mTc-linezolid was radio- and physico-chemically characterized to assess its suitability as a radiopharmaceutical for the brain. In-silico docking to target peptidyltransferase showed an optimal binding fit (energy = -66.6 Kcal/mol). The complex was biologically evaluated in-vitro using binding assays in alive and heat-killed bacteria and in-vivo in an MRSA brain infection model. All results suggested that the labeled complex could potentially be a new nuclear imaging agent to diagnose and localize brain abscesses specifically.

Preparation and evaluation of radiolabeled gliclazide parenteral nanoemulsion as a new tracer for pancreatic β-cells mass

PURPOSE

The present investigation aims to develop and evaluate a radiopharmaceutical for targeting and assessing β-cells mass based on gliclazide, an antidiabetic drug that specifically binds the sulfonylurea receptor unique to the β-cells of the pancreas.

METHODS

Conditions were optimized to radiolabel gliclazide with radioiodine via electrophilic substitution reaction. Then, it was formulated as a nanoemulsion system using olive oil and egg lecithin by hot homogenization followed by ultrasonication. The system was assessed for its suitability for parenteral administration and drug release. Then, the tracer was evaluated in silico and in vivo in normal and diabetic rats.

RESULTS AND CONCLUSIONS

The labeled compound was obtained with a high radiochemical yield (99.3 ± 1.1%) and good stability (>48 h). The radiolabeled nanoemulsion showed an average droplet size of 24.7 nm, a polydispersity index of 0.21, a zeta potential of -45.3 mV, pH 7.4, an osmolality of 285.3 mOsm/kg, and viscosity of 1.24 mPa.s, indicating suitability for parenteral administration. In silico assessment suggested that the labeling did not affect the biological activity of gliclazide. The suggestion was further supported by the in vivo blocking study. Following intravenous administration of nanoemulsion, the pancreas uptake was highest in normal rats (19.57 ± 1.16 and 12 ± 0.13% ID) compared to diabetic rats (8.51 ± 0.16 and 5 ± 0.13% ID) at 1 and 4 h post-injection, respectively. All results supported the feasibility of radioiodinated gliclazide nanoemulsion as a tracer for pancreatic β-cells.

Radioiodination, nasal nanoformulation and preliminary evaluation of isovanillin: A new potential brain cancer-targeting agent

Brain cancer is a challenging disease to treat using conventional approaches. The present investigation aimed to develop a radiopharmaceutical targeting brain cancer based on natural isovanillin. Different parameters were optimized, resulting in high radiolabeling efficiency (97.3 ± 1.2%) and good stability (<48 h). The tracer was formulated for intranasal delivery in a chitosan nanoparticles system with a mean particle size of 141 ± 2 nm, a polydispersity index of 0.23 ± 0.02, and a zeta potential of -17.4 ± 0.3 mV to enhance nasal uptake and surmount the blood-brain barrier. The system was characterized and assessed in-vitro for suitability and specificity and evaluated in-vivo in normal and tumorized mice. The biodistribution profile in brain tumor showed 20.5 ± 0.4 %ID/g localization and cancer cell targeting within 60 min. Improvement in brain tumor uptake resulted from both the nanoformulation and nasal administration of iodoisovanillin. Overall, the reported results encourage the potential use of the nanoformulated labeled compound as an anticancer agent.

Preparation and evaluation of radioiodinated avanafil: A novel potential radiopharmaceutical for the diagnostic evaluation of erectile dysfunction

Avanafil, a selective second-generation phosphodiesterase-5 inhibitor, was successfully labeled with iodine-125 via electrophilic and different factors affecting the labeling efficiency were studied. The labeled compound exhibited in-vitro stability of more than 24 h with a maximum labeling yield of up to 98.4 ± 1.9 %. Molecular modeling and in-vitro assessment of tracer inhibitory activity were performed to ensure that radiolabeling did not affect its binding ability to the target. Biodistribution studies were performed in normal rats and models of erectile dysfunction. The tracer specifically accumulated in the penis, and the clearance appeared to take place via the hepatobiliary route. Results suggested the usefulness of radiolabeled avanafil as a promising tracer for erectile dysfunction.

Preparation and preliminary evaluation study of [131I]iodocolchicine-gallic-AuNPs: a potential scintigraphic agent for inflammation detection

BACKGROUND

Nanomedicine offers great potential for scintigraphic diagnostic imaging with lower risk and higher quality compared to other traditional techniques.

OBJECTIVES

This work aimed to develop and evaluate gold nanoparticles combined with gallic acid (gallic-AuNPs) and [¹³¹I]iodocolchicine as a scintigraphic probe for inflammation.

METHODS

[¹³¹I]iodocolchicine-gallic-AuNPs were synthesized via chemical reduction method where gallic acid was used as reducing agent and [¹³¹I]iodocolchicine was used as stabilizing agent. Then a characteristic profile for the synthesized nano-platform was performed including size analysis, zeta potential, radiochemical yield and in-vivo biodistribution in inflammation bearing mice.

RESULTS AND CONCLUSION

This platform was successfully synthesized with good stability, appropriate particle size (10 nm diameter for AuNPs), and high radiochemical purity for [¹³¹I]iodocolchicine (96.79%). The in-vivo study indicated that [¹³¹I]iodocolchicine-gallic-AuNPs accumulated with a high target to non-target ratio in intravenous injection and high retention value in intra-inflammation injection in inflammation model. The obtained data supported the usefulness of the new platform ([¹³¹I]iodocolchicine-gallic-AuNPs) as a tracer for the detection and localization of inflammation.

Radiolabeling, characterization and preclinical evaluation of plazomicin: a potential tracer for bacterial infection

In this study, ^99m Tc-plazomicin, a new radio-antibiotic complex, was prepared specifically for bacterial infection localization and monitoring. Factors affecting the labeling reaction were studied and optimized to obtain a high yield (98.8 ± 0.2%). In-silico, radiochemical and physicochemical characterization and biodistribution were performed to assess the complex aptness as a radiopharmaceutical. The complex was biologically evaluated in-vitro using bacteria and in-vivo using different inflammation models (sterile, bacterial, and fungal). Uptake in the bacterial model was highest (7.8 ± 0.3%). Results indicated that the technetium label did not alter the antibiotic biological behavior and backed the usefulness of ^99m Tc-plazomicin as a potential tracer.