Radionuclide 131I labeled reduced graphene oxide for nuclear imaging guided combined radio- and photothermal therapy of cancer

Nano-graphene and its derivatives have attracted great attention in biomedicine, including their applications in cancer theranostics. In this work, we develop 131I labeled, polyethylene glycol (PEG) coated reduced nano-graphene oxide (RGO), obtaining 131I-RGO-PEG for nuclear imaging guided combined radiotherapy and photothermal therapy of cancer. Compared with free 131I, 131IRGO- PEG exhibits enhanced cellular uptake and thus improved radio-therapeutic efficacy against cancer cells. As revealed by gamma imaging, efficient tumor accumulation of 131I-RGO-PEG is observed after its intravenous injection. While RGO exhibits strong near-infrared (NIR) absorbance and could induce effective photothermal heating of tumor under NIR light irradiation, 131I is able to emit high-energy X-ray to induce cancer killing as the result of radio ionization effect. By utilizing the combined photothermal therapy and radiotherapy, both of which are delivered by a single agent 131IRGO- PEG, effective elimination of tumors is achieved in our animal tumor model experiments. Toxicology studies further indicate that 131I-RGO-PEG induces no appreciable toxicity to mice at the treatment dose. Our work demonstrates the great promise of combing nuclear medicine and photothermal therapy as a novel therapeutic strategy to realize synergistic efficacy in cancer treatment.     

The Alginate Layer for Improving Doxorubicin Release and Radiolabeling Stability of Chitosan Hydrogels

Purpose

Chitosan hydrogels (CSH) formed through ionic interaction with an anionic molecule are suitable as a drug carrier and a tissue engineering scaffold. However, the initial burst release of drugs from the CSH due to rapid swelling after immersing in a biofluid limits their wide application as a drug delivery carrier. In this study, alginate layering on the surface of the doxorubicin (Dox)-loaded and I-131-labeled CSH (DI-CSH) was performed. The effect of the alginate layering on drug release behavior and radiolabeling stability was investigated.

Methods

Chitosan was chemically modified using a chelator for I-131 labeling. After labeling of I-131 and mixing of Dox, the chitosan solution was dropped into tripolyphosphate (TPP) solution using an electrospinning system to prepare spherical microhydrogels. The DI-CSH were immersed into alginate solution for 30 min to form the crosslinking layer on their surface. The formation of alginate layer on the DI-CSH was confirmed by Fourier transform infrared spectroscopy (FT-IR) and zeta potential analysis. In order to investigate the effect of alginate layer, studies of in vitro Dox release from the hydrogels were performed in phosphate buffered in saline (PBS, pH 7.4) at 37 °C for 12 days. The radiolabeling stability of the hydrogels was evaluated using ITLC under different experimental condition (human serum, normal saline, and PBS) at 37 °C for 12 days.

Results

Formatting the alginate-crosslinked layer on the CSH surface did not change the spherical morphology and the mean diameter (150 ± 10 μm). FT-IR spectra and zeta potential values indicate that alginate layer was formed successfully on the surface of the DI-CSH. In in vitro Dox release studies, the total percentage of the released Dox from the DI-CSH for 12 days were 60.9 ± 0.8, 67.3 ± 1.4, and 71.8 ± 2.5 % for 0.25, 0.50, and 1.00 mg Dox used to load into the hydrogels, respectively. On the other hand, after formatting alginate layer, the percentage of the released Dox for 12 days was decreased to 47.6 ± 1.4, 51.1 ± 1.4, and 57.5 ± 1.6 % for 0.25, 0.50, and 1.00 mg Dox used, respectively. The radiolabeling stability of DI-CSH in human serum was improved by alginate layer.

Conclusions

The formation of alginate layer on the surface of the DI-CSH is useful for improving the drug release behavior and radiolabeling stability.     

SPECT/CT imaging of radiolabeled cubosomes and hexosomes for potential theranostic applications

We have developed a highly efficient method for the radiolabeling of phytantriol (PHYT)/oleic acid (OA)-based hexosomes based on the surface chelation of technetium-99m (^99mTc) to preformed hexosomes using the polyamine 1, 12-diamino-3, 6, 9-triazododecane (SpmTrien) as chelating agent. We also report on the unsuccessful labeling of cubosomes using the well-known chelating agent hexamethylpropyleneamine oxime (HMPAO). The ^99mTc-labeled SpmTrien-hexosomes (^99mTc-SpmTrien-hexosomes) were synthesized with good radiolabeling (84%) and high radiochemical purity (>90%). The effect of radiolabeling on the internal nanostructure and the overall size of these aqueous dispersions was investigated by using synchrotron small angle X-ray scattering (SAXS), dynamic light scattering (DLS), and transmission electron cryo microscopy (cryo-TEM). Further, we show the utility of ^99mTc-SpmTrien-hexosomes for the in vivo imaging of healthy mice using single photon emission computed tomography (SPECT) in combination with computed tomography (CT), i.e. SPECT/CT. SPECT/CT experiments of subcutaneously administered ^99mTc-SpmTrien-hexosomes to the flank of mice showed a high stability in vivo allowing imaging of the distribution of the radiolabeled hexosomes for up to 24 h. These injected ^99mTc-SpmTrien-hexosomes formed a deposit within the subcutaneous adipose tissue, displaying a high biodistribution of ∼343% injected dose/g tissue (%ID/g), with negligible uptake in other organs and tissues. The developed ^99mTc labeling method for PHYT/OA-based hexosomes could further serve as a useful tool for investigating and imaging the in vivo performance of cubosomal and hexosomal drug nanocarriers.     

45Ca标记复合钙化合物示踪钙生物动力学观察

目的用放射性核素^45Ca标记4种钙制剂化合物，并观察和示踪其生物利用度。方法用^45Ca标记葡萄糖酸钙、柠檬酸钙、碳酸钙和L-苏糖酸钙，测定大鼠心、肝、脾、肾、脑、胃、肠、血液、粪便和尿中钙离子吸收含量和生物利用度。结果①^45Ca标记的钙制剂具有较高的放射性活度、较稳定的组织标准曲线和回收率。②示踪4种化合物生物利用度变化显示，有机钙化合物较无机钙化合物更利于组织的吸收。结论^45Ca标记钙制剂生物示踪方法具有灵敏、客观、准确和稳定的特点。     

Anti-sense oligonucleotide labeled with technetium-99m using hydrazinonictinamide derivative and N-hydroxysuccinimidyl S-acetylmercaptoacetyltriglycline：A comparison of radiochemical behaviors and biological properties

AIM：To explore and compare the radiochemical behavior and biological property of anti-sense oligonuc-leotide （ASON） labeled with technetium-99m using N-hydroxysuccinimidyl S-acetylmercaptoacetyltriglycl ine （NHS-MAG3） and hydrazinonictinamide derivative （HYNIC）. METHODS：After HYNIC and NHS-MAG3 were synthesized, ASON was labeled with technetium-99m using HYNIC and NHS-MAG3 as a bifunctional chelator. The in vivo and in vitro stability, binding rates of labeled compounds to serum albumen, biodistribution of ^99mTc-MAG3-ASON and ^99mTc-HYNIC-ASON in BALB/C mouse and its HT29 tumor cellular uptake were compared. RESULTS：The labeling efficiency and stability of ^99mTc-MAG3-ASON were significantly higher than those of ^99mTc-HYNIC-ASON （P = 0.02, and P = 0.03, respectively）. ^99mTc-MAG3-ASON had a significantly lower rate of binding to serum albumen than ^99mTc-HYNIC-ASON （P 〈 0.05）. In contrast to ^99mTc-HYNIC-ASON, the biodistribution of ^99mTc-MAG3-ASON was significantly lower in blood, heart, liver and stomach （P 〈0.05）, slightly lower in intestines and spleen （P 〉 0.05） and significantly higher in lung and kidney （P 〈 0.05）. The HT29 tumor cellular uptake rate of ^99mTc-MAG3-ASON was significantly higher than that of ^99mTc-HYNIC-ASON （P 〈 0.05）. CONCLUSION：^99mTc-MAG3-ASON shows superior radiochemical behaviors and biological properties than ^99mTc-HYNIC-ASON. ^99mTc-MAG3-ASON is a potential radiopharmaceutical agent for in vivo application.     

Radiolabeling and dose fixation study of oral alpha-ketoglutarate as a cyanide antidote in healthy human volunteers

Context. Radiolabeling and dose fixation study of alpha-ketoglutarate (A-KG). Objective. A-KG is a potential oral antidote for cyanide poisoning. Its protective efficacy in animals was best exhibited at a dose of 2.0 g/kg body weight, which when extrapolated to human is very high. The objective of this study was to reduce the dose of A-KG in humans with concomitant increase in its bioavailability, employing pharmacoscintigraphic techniques to assess kinetics in man. Materials and methods. A-KG was radiolabeled with technetium-99m pertechnetate (Tc-99m) and its purity, labeling efficiency, and stability in vitro were determined by instant thin layer chromatography. Time-dependent bio-absorption of the drug in rats and rabbits was assessed by gamma scintigraphy after oral administration of a tracer dose of ^99mTc-A-KG mixed with nonradioactive A-KG at a concentration of 0.1–2.0 g/kg in the presence or absence of aqueous dilution. Furthermore, scintigraphy and radiometry studies were performed in healthy human volunteers using 5–20 g of A-KG, given in single or split doses followed by different quantity of water. Drug bioavailability was estimated periodically. Results. High radiolabeling (>97%) of A-KG with a stability of 24 h in vitro was obtained. Less than 1% absorption of the drug occurred within 20 min after A-KG was administered in animals at a concentration of 2.0 g/kg body weight. One-tenth reduction in dose increased the bioavailability to 15%. Significant improvement in gastric emptying of the drug was achieved when the drug was administered along with 1–5 mL of water. In humans, two doses of 10 g A-KG given at an interval of 10 min, followed by 300 mL of water, increased the drug bioavailability to 40% as compared to a single dose of 20 g. Discussion. Significant reduction in A-KG dose was achieved in humans as compared to the recommended dose in animals. Conclusion. Aqueous dilution improves the bioavailability of A-KG in humans.     

Electrochemical radiofluorination. Part 2. Anodic monofluorination of substituted benzenes using [F]fluoride

Electrochemical fluorination of various monosubstituted aromatic compounds was performed with [¹⁸F]fluoride using potentiostatic anodic oxidation on platinum electrodes in an undivided cell in acetonitrile with a mixture of Et₃N·3HF/Et₃N·HCl as electrolyte. Maximum radiochemical yields were obtained after a charge of 50 C passed the solution. The results showed a clear dependence of the radiochemical yields on the oxidation potentials E_1/2 of the substrates as a consequence of different substituents namely CH₃CO-, F-, Cl-, Br- and tert.-Butyl. With increasing E_1/2, the fluorination yields decreased from 7.9% (tert.-butylbenzene) to 1.5% (acetophenone). The ratio between F-for-X substitution and F-for-H substitution correlated with the bond energies of the C–X bond. With higher bond energies, less X-substitution was observed.     

A radiolabeled peptide ligand of the hERG channel, [125I]-BeKm-1

The wild-type scorpion toxin BeKm-1, which selectively blocks human ether-a-go-go related (hERG) channels, was radiolabeled with iodine at tyrosine 11. Both the mono- and di-iodinated derivatives were found to be biologically active. In electrophysiological patch-clamp recordings mono-[¹²⁷I]-BeKm-1 had a concentration of half-maximal inhibition (IC₅₀ value) of 27 nM, while wild-type BeKm-1 inhibited hERG channels with an IC₅₀ value of 7 nM. Mono-[¹²⁵I]-BeKm-1 was found to bind in a concentration-dependent manner and with picomolar affinity to hERG channel protein in purified membrane vesicles from transfected human embryonic kidney cells (HEK-293). Under optimized conditions the equilibrium dissociation constant (K_d) values from saturation and kinetic binding analysis were 13 and 14 pM, respectively. Both the association and dissociation of [¹²⁵I]-BeKm-1 were fast (association rate constant, k_on=3.6×10⁷ M^–1s^–1; dissociation rate constant, k_off=0.005 s^–1). Wild-type BeKm-1 displaced binding of [¹²⁵I]-BeKm-1 with half-maximal inhibitory concentrations of 44 pM. In contrast, competition experiments with a BeKm-1 mutant BeKm-1-K18A, in which the toxin interaction site is disrupted, resulted in a drop in affinity by more than 300-fold as compared to the wild-type toxin. Iberiotoxin and apamin, peptide inhibitors of Ca²⁺-activated K⁺-channels, had no effect on [¹²⁵I]-BeKm-1 binding. Adding the classical rapid delayed rectifier current (I_Kr) blocker E-4031 reduced binding of [¹²⁵I]-BeKm-1 to the hERG channel to an IC₅₀ of 7 nM. In autoradiographic studies on rat hearts, binding of [¹²⁵I]-BeKm-1 was dose-dependent and could partially be displaced by the addition of excess amounts of non-radioactive BeKm-1. The density of the radioactive signal was equally distributed in the myocardium of both the ventricle and atria indicating a homogenous expression of hERG channels throughout the heart.     

Spectrophotometric method for determination of bifunctional macrocyclic ligands in macrocyclic ligand-protein conjugates

A simple spectrophotometric assay for determination of bifunctional polyazacarboxylate-macrocyclic ligands of different sizes that are conjugated to proteins has been developed for: 12-membered macrocycle DOTA (2-[4-nitrobenzyl]-1, 4, 7, 10-tetraazacyclododecane-N,N′,N″,N-tetraacetic acid) and analogs, the 15-membered PEPA macrocycle (2-[4-nitrobenzyl]-1,4,7,10,13-pentaazacyclopentadecane-N,N′,N″,N,N-pentaacetic acid), and the large 18-membered macrocycle HEHA (1,4,7,10,13,16-hexaazacyclooctadecane-N,N′,N″,N,N,N′-hexaacetic acid). The method is based on titration of the blue-colored 1:1 Pb(II)-Arsenazo III (AAIII) complex with the polyazacarboxylate macrocyclic ligand in the concentration range of 0–2.5 μM, wherein color change occurring upon transchelation of the Pb(II) from the AAIII to the polyazamacrocyclic ligand is monitored at 656 nm. The assay is performed at ambient temperature within 20 min without any interfering interaction between the protein and Pb(II)–AA(III) complex. Thus, this method also provides a ligand-to-protein ratio (L/P ratio) that reflects the effective number of ligands per protein molecule available to radiolabeling. The method is not suitable for 14-membered TETA macrocycle (2-[4-nitrobenzyl]-1, 4, 8, 11-tetraazacyclotetradecane N,N′,N″,N-tetraacetic acid) because of low stability constant of Pb(II)-TETA complex. The method is rapid, simple and may be customized for other polyazacarboxylate macrocyclic ligands.