Drina Janković

Background/Objectives: Effective intratumoral radionuclide therapy requires nanocarriers that enable stable radionuclide coordination and prolonged tumor retention. Integrating these properties with efficient magnetic heating within a single nanoplatform remains challenging because optimization of one property may compromise another. This study investigated whether manganese substitution could improve the magnetic heating performance of 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP)-functionalized maghemite nanoparticles while preserving their suitability for radiopharmaceutical applications. Methods: Three Mn_xFe_2−xO₃ compositions (x = 0, 0.221, and 0.480) were evaluated in terms of their structural and physicochemical properties, colloidal stability, and magnetic heating performance. The most promising Mn-substituted formulation and the unsubstituted reference were evaluated by ¹⁷⁷Lu radiolabeling, in vitro radiochemical stability testing, whole-body imaging, ex vivo biodistribution analysis, and therapeutic efficacy assessment in 4T1 tumor-bearing mice. Results: Moderate Mn substitution (x = 0.221) provided the most favorable combination of magnetic heating performance (SAR = 360 W g⁻¹; ILP = 5.65 nH m² kg⁻¹) and colloidal stability. HEDP functionalization enabled direct radiolabeling with ¹⁷⁷Lu, with labeling yields of 86–92% and radiochemical stability exceeding 94% after 96 h in saline and human serum. Following intratumoral administration, qualitative whole-body imaging showed persistent tumor-associated radioactivity for both nanoparticle formulations on days 5 and 14. On day 14, tumor-associated activity was 91.68 ± 0.73%ID and 84.53 ± 2.26%ID for [¹⁷⁷Lu]Lu-NP1 and [¹⁷⁷Lu]Lu-NP2, respectively, compared with 17.49 ± 8.06%ID for free [¹⁷⁷Lu]LuCl₃. Both nanoparticle formulations inhibited tumor growth compared with saline, with a more pronounced response and partial tumor regression in animals bearing smaller tumors at treatment initiation. Conclusions: Moderate Mn substitution improved magnetic heating performance and colloidal stability while preserving the radiochemical stability, intratumoral retention, and therapeutic efficacy of the ¹⁷⁷Lu-labeled HEDP-functionalized nanocarriers. This nanoplatform warrants further investigation for intratumoral ¹⁷⁷Lu therapy and its potential integration with magnetic hyperthermia.

Background: Bone-seeking radiopharmaceuticals based on bisphosphonates enable targeted therapy of skeletal metastases. They are suitable carriers for therapeutic radionuclides such as terbium-161 (¹⁶¹Tb), a β⁻ emitter that additionally releases short-range conversion and Auger electrons, which may enhance radiation dose delivery to small lesions. This study explored the potential of the well-established DOTA conjugated bisphosphonate BPAMD (4-{[(bis(phosphonomethyl))carbamoyl]methyl}-7,10-bis(carboxymethyl)-1,4,7,10 tetraazacyclododec-1-yl)acetic acid) radiolabeled with ¹⁶¹Tb as a bone-targeted radiopharmaceutical, focusing on the theranostic and radiophysical advantages conferred by the radionuclide. Methods: BPAMD was radiolabeled with ¹⁶¹Tb and ¹⁷⁷Lu under mild conditions (pH 4.5, 95 °C, 30 min); subsequently, the radiochemical purity was assessed by radio-TLC. Physicochemical properties (charge, lipophilicity, protein binding), in vitro stability (saline and human serum, 48 h), and hydroxyapatite (HAP) binding were evaluated for [¹⁶¹Tb]Tb-BPAMD. Biodistribution was investigated in healthy Wistar rats (n = 3 per time point) at 2 h, 24 h, and 7 days post-injection. Computational density functional theory (DFT) analyses were performed to explore the coordination chemistry of Tb³⁺ and Lu³⁺ with BPAMD. Results: Both complexes achieved a radiochemical yield of greater than 98%. [¹⁶¹Tb]Tb-BPAMD exhibited negative charge, high hydrophilicity (logP = −3.92 ± 0.13), low protein binding (19.07 ± 1.01%), excellent radiochemical stability under simulated physiological conditions (>97% at 48 h), and strong hydroxyapatite affinity (>98% with ≥10 mg HAP). Biodistribution showed high, stable bone uptake (8.06% ID/g at 2 h; 6.70% ID/g at 24 h; 5.31% ID/g at 7 d) with rapid blood clearance (161Tb]Tb-BPAMD was compared with [¹⁷⁷Lu]Lu-BPAMD, which demonstrated similarly strong skeletal retention (8.74% ID/g at 2 h; 8.08% ID/g at 24 h; 5.25% ID/g at 7 d) but comparatively higher non-target organ uptake. DFT calculations indicate that both Tb³⁺ and Lu³⁺ favor octa-coordinated BPAMD complexes. Conclusions: [¹⁶¹Tb]Tb-BPAMD exhibits excellent radiochemical and pharmacokinetic properties, with enhanced biodistribution selectivity over [¹⁷⁷Lu]Lu-BPAMD. Combined with the radiobiological advantages of ¹⁶¹Tb, it represents a promising theranostic candidate for targeted therapy of bone metastases.

Background: Bone-seeking radiopharmaceuticals based on bisphosphonates enable targeted therapy of skeletal metastases. They are ideal carriers for therapeutic radionuclides such as Terbium-161 (¹⁶¹Tb), a β-emitter that additionally releases short-range conversion and Auger electrons, which may enhance radiation dose delivery to small lesions. This study aimed to investigate the potential of the specific DOTA conjugated bisphosphonate - BPAMD (4-{[(bis(phosphonomethyl))carbamoyl]methyl}-7,10-bis(carboxymethyl)-1,4,7,10 tetraazacyclododec-1-yl)acetic acid) radiolabeled with ¹⁶¹Tb as a next-generation of bone-targeted radiopharmaceutical. Methods: BPAMDwas radiolabeled with ¹⁶¹Tb and ¹⁷⁷Lu under mild conditions (pH 4.5, 95°C, 30min); subsequently the radiochemical purity was assessed by radio-TLC and radioelectrophoresis. Physicochemical properties (charge, lipophilicity, protein binding), in vitro stability (saline and human serum, 48h), and hydroxyapatite binding were evaluated for ¹⁶¹Tb-BPAMD. Biodistribution was studied in healthy Wistar rats (n=3 per time point) at 2h, 24h, and 7 days post-injection. Complementary DFT calculations explored the coordination chemistry of Tb³⁺ and Lu³⁺ with BPAMD. Results: Both complexes achieved >98% radiochemical yield. ¹⁶¹Tb-BPAMD exhibited negative charge, high hydrophilicity (logP = –3.92±0.13), low protein binding (19.07±1.01%), excellent radiochemical stability under simulated physiological conditions (>97% at 48h), and strong hydroxyapatite affinity (>98% with ≥10 mg HAP). Biodistribution showed high, stable bone uptake (8.06% ID/g at 2h; 6.70% ID/g at 24h; 5.31% ID/g at 7d) with rapid blood clearance (161Tb-BPAMD was compared with ¹⁷⁷Lu-BPAMD, which demonstrated similarly strong skeletal retention (8.74% ID/g at 2h; 8.08% ID/g at 24h; 5.25% ID/g at 7d) but comparatively higher non-target organ uptake. Complementary DFT calculations indicate that both Tb³⁺ and Lu³⁺ favor octa-coordinated BPAMD complexes. Conclusions: ¹⁶¹Tb-BPAMD exhibits excellent radiochemical and pharmacokinetic properties, with enhanced biodistribution selectivity over ¹⁷⁷Lu-BPAMD. Combined with the radiobiological advantages of ¹⁶¹Tb, it represents a promising theranostic candidate for targeted therapy of bone metastases.

Two diphosphonates, etidronic acid (HEDP) and zoledronic acid (ZOL), were radiolabelled with ¹⁶¹Tb and evaluated as potential bone-targeting radiopharmaceuticals. Radiolabeling was performed at pH 7, achieving high radiolabeling yields (greater than 98%) and demonstrating excellent in vitro stability in saline and human serum. Both radiolabeled complexes exhibited hydrophilic behavior, a strong binding affinity to hydroxyapatite, and moderate to high plasma protein binding. Biodistribution studies in healthy Wistar rats demonstrated that ¹⁶¹Tb-HEDP and ¹⁶¹Tb-ZOL achieve high and stable skeletal uptake with rapid blood clearance and minimal soft tissue accumulation. ¹⁶¹Tb-HEDP favored higher initial bone localization, while ¹⁶¹Tb-ZOL showed lower renal and hepatic accumulation, indicating higher safety and selectivity. Compared to unchelated ¹⁶¹TbCl₃, both diphosphonate complexes exhibited significantly higher bone-to-kidney and bone-to-liver ratios, resulting in superior targeting. Complementary experiments with non-radioactive terbium were performed to investigate the redox behavior and confirm complex formation, providing valuable insight into the stability and binding modes of the ligands. Both terbium and the ligands displayed well-defined redox behavior within the potential range of −1 to 1.7 V, with complex formation evidenced by shifts in the oxidation peaks. Density functional theory (DFT) calculations further supported these findings, showing that both phosphonate groups of a ligand coordinate to Tb³⁺, while the hydroxyl groups in HEDP enable intermolecular hydrogen bonding, contributing to additional structural stabilization. Results encourage further investigations of ¹⁶¹Tb-labeled diphosphonates as promising candidates for radionuclide therapy of bone metastases and other skeletal diseases.

Zeolitic imidazolate frameworks (ZIF-8) are promising radionuclide carriers due to their high stability and surface functionalization potential. In this study, ZIF-8 was synthesized using a two-step process. First, (Zn,Zn) hydroxy double salt (HDS) was prepared by mixing an aqueous ZnO suspension (1 M), Zn(CH₃CO₂)₂ aqueous solution (1 M), and DMF for 24 hours. The (Zn,Zn) HDS suspension was then added to a 2-methylimidazole (6 mmol) DMF solution under rapid magnetic stirring at room temperature for 10 minutes. The obtained product was filtered and air-dried [1]. The efficiency of ZIF-8 radiolabeling with lutetium-177 (¹⁷⁷Lu) was investigated under various experimental conditions. The results showed that the obtained samples exhibited a high radiolabeling yield (>94%), with the highest value of 98.8% recorded for samples treated at 70°C. In vitro testing under physiological conditions confirmed the high stability of the radiolabeled samples, with less than 9.2% of ¹⁷⁷Lu³⁺ released after 14 days of incubation in human serum. Theoretical analyses based on density functional theory (DFT) calculations identified key interactions responsible for the stable incorporation of ¹⁷⁷Lu within the ZIF-8 structure. Electrostatic potential mapping revealed regions with a high affinity for ¹⁷⁷Lu³⁺ adsorption, with primary binding mechanisms involving coordination with Zn-OH groups and N-H groups of imidazole. FTIR analysis confirmed the formation of coordination bonds between lutetium and ZIF-8 functional groups, with spectroscopic shifts indicating Zn-O-Lu and Lu-N interactions. The obtained results in this study and literature data [2] highlight the potential of ZIF-8 for the simultaneous integration of therapeutic (¹⁷⁷Lu) and diagnostic (⁹⁹ᵐTc) radionuclides, enabling its application in tumor theranostics. Additionally, radiolabeled ZIF-8 exhibits characteristics compatible with other metal-organic frameworks (MOFs), further confirming its versatility as a platform for radionuclide therapy.

Microbial contamination of food and alimentary toxoinfection/intoxication in humans are commonly caused by bacteria such as Salmonella spp., Escherichia coli, Yersinia spp., Campylobacter spp., Listeria monocytogenes, and fungi (Aspergillus, Fusarium). The addition of probiotic cultures (bacterial strains Lactobacillus and Bifidobacterium and the yeast Saccharomyces cerevisiae var. boulardii) to food contributes primarily to food enrichment and obtaining a functional product, but also to food preservation. Reducing the number of viable pathogenic microorganisms and eliminating or neutralizing their toxins in food is achieved by probiotic-produced antimicrobial substances such as organic acids (lactic acid, acetic acid, propionic acid, phenylacetic acid, and phenyllactic acid), fatty acids (linoleic acid, butyric acid, caproic acid, and caprylic acid), aromatic compounds (diacetyl, acetaldehyde, reuterin), hydrogen peroxide, cyclic dipeptides, bacteriocins, and salivabactin. This review summarizes the basic facts on microbial contamination and preservation of food and the potential of different probiotic strains and their metabolites (postbiotics), including the mechanisms of their antimicrobial action against various foodborne pathogens. Literature data on this topic over the last three decades was searched in the PubMed, Scopus, and Google Scholar databases, systematically presented, and critically discussed, with particular attention to the advantages and disadvantages of using probiotics and postbiotics as food biopreservatives.

To better understand the mechanism of action of the compounds in the ethanolic extracts of J. nigra leaves and green husks, their binding to CT-DNA was investigated. This study was conducted to elucidate the in vitro protective effect of extracts against chromosomal damage in mitogen-induced human lymphocytes and investigate the possible application of selec+ted extracts as a natural source of polyphenolic compounds. Using HPLC-MS analysis, 103 different compounds were identified as having a higher number of active species, which is consistent with their activity. The frequency of micronuclei (MN) was scored in binucleated cells, and the nuclear proliferation index was calculated. Cyclic voltammetry experiments demonstrate that the nature of the interaction between extracts and CT-DNA is a synergy of electrostatic and intercalative modes, where leaves extracts showed a higher ability to bind to DNA. Extracts showed excellent antioxidant activity. At a concentration of only 4 µg/mL, extract of J. nigra leaves and the green husks reduced the incidence of MN by 58.2% and 64.5%, respectively, compared to control cell cultures.

Combined radionuclide therapy with magnetic nanoparticles has been a research focus as a promising approach for tumor therapy. In this study, superparamagnetic iron oxide nanoparticles (SPIONs) were synthesized using the co-precipitation method and coated with meso-1,2- dimercaptosuccinic acid (DMSA). Structural investigations showed that DMSA-coated SPIONs had a particle size of 140.3±6.5 nm in diameter with a spherical morphology. With a zeta potential of −35.1 mV, functionalization with DMSA led to increase the stability of the nanoparticles in solution. DMSA-SPIONs were radiolabeled with 177Lu in high radiolabeling yield (86.6 ± 2.1%, and after separation by magnetic decantation >99%), showing high in vitro stability in saline and human serum up to 96 h. After intratumoral injection into mouse colorectal CT-26 or breast 4T1 subcutaneous tumors, the radiolabeled nanoparticles remained well localized at the injection site over a 14-day period, with limited leakage.

Metal complexes with BH4- ligands show peculiar structural and dynamic properties, and possess many important and applicable qualities (potent reducing agents and catalysts, materials for hydrogen storage). Electron paramagnetic resonance (EPR) is very important for the characterization of complex compounds, determination of their electronic configuration and geometry. Also, Density Functional Theory (DFT) can predict EPR parameters and explain them more profoundly. Hence, in this paper hyperfine coupling constants of d metal complexes with BH4- ligands have been determined by DFT calculations, and analyzed in detail.