Preparation of 153Sm-chitosan complex for radiation synovectomy

Development of 186/188Re-Chitosan as an Effective Therapeutic Agent for Rheumatoid Arthritis

BACKGROUND

Rheumatoid arthritis (RA) is an inflammatory chronic disease characterized by inflammation, pain, swelling and disability, and radiosynovectomy is one of the disease treatment lines. In this study, the possibility of providing rhenium-186/rhenium-188 chitosan radiopharmaceuticals, optimization of conditions for their production and bio-distribution are reported.

OBJECTIVE

In order to build perrhenic acid for labeling, natural rhenium was exposed to radiation. Radionuclidic and radiochemical purities of (186/188Re)-NaReO4 were examined by gamma spectroscopy and paper chromatography methods, respectively.

METHODS

Labeling of chitosan with rhenium was done in different acidic situations. The radiochemical purity 186/188Re-chitosan was applied by radio thin layer chromatography (RTLC). Lastly, the bio-distribution of the radiolabeled chitosan was studied in various organs after intra articular injection of the complex to lab rats. Gamma spectrometry confirmed the high rhenium radionuclidic purity. Chromatography results showed that perrhenic acid was produced with purity greater than 97% and rhenium chitosan labeling was done over 98% in pH = 3. Dissection results showed a high bio-distribution of 186/188Re-chitosan after injection into the joint with no leakage to surrounding organs.

CONCLUSION

According to the results, there is a possibility of labeling rhenium with chitosan in very high radiochemical purity. Regarding the high retention of these radiopharmaceuticals in joints with no leakage to surrounding organs, 186/188Re-chitosan can be applied as new radiosynovectomy drugs for rheumatoid arthritis treatment.

A kit based methodology for convenient formulation of 166Ho-Chitosan complex for treatment of liver cancer

The effectiveness of ¹⁶⁶Ho-chitosan complex as a radiopharmaceutical for trans-arterial radiation therapy of liver cancer has been established in clinical trials. We have developed a simple kit-bade strategy for convenient formulation of therapeutically relevant doses of ¹⁶⁶Ho-chitosan complex in a hospital radiopharmacy in order to facilitate its widespread utilization. Quality control studies established the suitability of the radiopharmaceutical formulated using the developed strategy for in vivo administration. Biodistribution studies in normal Wistar rats showed excellent retention of the radiopharmaceutical in the liver, thus, paving the way towards utility of this approach in clinical context.

Fabrication of Gd/Eu-codoped SmPO4 nanorods for dual-modal magnetic resonance and bio-optical imaging

Ln-based complexes can be used as T1-enhanced contrast agents of magnetic resonance (MR) imaging in clinical field. Herein, we present a facile and feasible biomineralization process to fabricate Gd/Eu-codoped SmPO4 nanorods (NRs) with silk fibroin (SF) peptides (codoped SF-NRs) as T1-enhanced contrast agents, which possess paramagnetic property, photoluminescence (PL), better cyto-/tissue-compatibility and longer half-life in blood due to SF coating on their surface. Their bio-distributions in TB-N mice via tail-vein injection indicated that, although SF-NRs could be safely cleared away through renal and fecal excretion, SF-NRs easily permeated and aggregated in tumors. The results of in vitro MR imaging demonstrate that the longitudinal relaxivity r1 value of codoped SF-NRs (0.31 Sm-Gd mM(-1) s(-1)) is not only significantly higher than those of Gd-doped and Eu-doped SmPO4 SF-NRs, but also higher than those of codoped pure NRs. The tests of in vivo T1 weighted MR imaging via intro-tumor injection and tail-vein injection confirm that, compared to the pure NRs, the codoped SF-NRs exhibited higher positive signal-enhancement ability. Furthermore, the better luminescence imaging of living cells under the fluorescence microscope (94% stronger than that of the NRs without SF). A formation mechanism of codoped SF-NRs is proposed, to explain the synergistic effect of Gd/Eu codoping and SF coating on their enhanced bio-compatibility, half-life in blood, T1-weighted MR imaging and PL imaging.

Synthesis and characterization of folic acid modified water-soluble chitosan derivatives for folate-receptor-mediated targeting

Three chemical modification methods of carboxymethylation, quaternization and hydroxypropylation were used to synthesize water-soluble chitosan derivatives. In order to study the feasibility of these chitosan derivatives as backbones of nuclear imaging agents, folic acid (FA) and Technetium-99m were introduced onto the water-soluble chitosan chains. The bifunctional chelating agent 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) was conjugated to the folate grafted chitosan derivatives for chelating with radionuclides such as (64)Cu and (68)Ga. The structures of these new ligands were characterized with multiple methods. The solubility and stability of the (99m)Tc-complexes were both favorable. Further study of their radiochemical and biological properties will be performed to evaluate the usefulness of these water-soluble chitosan derivatives for nuclear imaging agent design.

Radiolanthanides in endoradiotherapy: an overview

Endoradiotherapy (targeted radionuclide therapy) is a systemic approach, involving a radiolabeled targeting vector with a well characterized biochemical strategy to selectively deliver a cytotoxic level of radiation to a disease site on a cellular/molecular level. The group of radiolanthanides has been considered both for imaging and therapy over many years. Some radiolanthanides have been and are increasingly applied for therapeutic purposes.

However, the clinical use of endoradiotherapeuticals containing radiolanthanides requires a complex and interdisciplinary approach. It involves, among other factors, the choice of the most suitable lanthanide radionuclide (in terms of nuclear decay parameters such as type and energy of the particles emitted, half-life, decay products etc.); the identification of the most promising production route; the determination of the relevant production parameters such as excitation functions, nuclear reaction yields, radionuclidic purities, specific activities etc.; the chemical isolation of the radiolanthanide produced from the target material (except the (n, γ) production route); the synthesis of the labelling precursor, and labelling of the precursor and the chemical purification and isolation of the labelled radiotherapeutical, ready for i.v. injection; and finally the investigation of pharmacological targeting parameters of the labelled radiotherapeutical in vitro and in vivo (animal experiments).

Role of radiosynovectomy in the treatment of rheumatoid arthritis and hemophilic arthropathies

Radiosynovectomy is a novel method of treatment for several acute and chronic inflammatory joint disorders. A small amount of a beta-emitting radionuclide is injected into the affected joint delivering a radiation dose of 70 to 100 Gy to the synovia. The proliferative tissue is destroyed, secretion of fluid and accumulation of inflammation causing cellular compounds stops and the joint surfaces become fibrosed, providing long term symptom relief. The radionuclides are injected in colloidal form so that they remain in the synovium and are not transported by lymphatic vessels causing radiation exposure to other organs. Complete reduction of knee joint swelling has been seen in above 40% and pain relief in 88% of patients. Wrist, elbow, shoulder, ankle and hip joints showed significant improvement in 50-60% and restoration of normal function and long term pain relief has been achieved in about 70% of small finger joints. In hemophilic arthropathies complete cessation of bleeding in about 60% and improved mobility in 75% of patients has been reported.

Localized internal radiotherapy with 90Y particles embedded in a new thermosetting alginate gel: A feasibility study in pigs

BACKGROUND

Internal radiotherapy requires the localization of the radionuclide to the site of action. A new injectable alginate gel formulation intended to undergo immediate gelation in tissues and capable of encapsulating radioactive particles containing 90Y was investigated.

METHODS

The formulation was injected intramuscularly, into the bone marrow compartment of the femur and intravenously, respectively, in pigs. The distribution of radioactivity in various tissues was determined.

RESULTS

Following intramuscular injection, more than 90% of the radioactivity was found at the site of injection. Following injection into bone marrow, 30-40% of the radioactivity was retained at the site of injection, but a considerable amount of radioactivity was also detected in the lungs (35-45%) and the liver (5-18%). Following intravenous injection, 80-90% of the radioactivity was found in the lungs.

CONCLUSION

The present formulation appears suitable for localized radiotherapy in organs and tissues having low perfusion.