Pradip Chaudhari

177Lu-EDTMP: A Viable Bone Pain Palliative in Skeletal Metastasis

Designing ideal radiopharmaceuticals for use as bone pain palliatives require the use of a moderate energy beta() emitter as a radionuclide and a suitable polyaminophosphonic acid as a carrier molecule. Owing to its suitable decay characteristics [T(1/2) = 6.73 d, E((max)) = 497 keV, E() = 113 keV (6.4%), 208 keV (11%)] as well as the feasibility of large-scale production in adequate specific activity and radionuclidic purity using a moderate flux reactor, 177Lu could be considered as a promising radionuclide for palliative care in painful bone metastasis. The present study was therefore, oriented toward the preparation and biologic evaluation of 177Lu complex of ethylenediaminetetramethylene phosphonic acid (EDTMP) in various animal models, with an aim to prepare a viable radiopharmaceutical for bone pain palliation. 177Lu was produced with a specific activity of approximately 12 GBq/mg (approximately 324 mCi/mg) and radionuclidic purity of 99.98% by irradiation of natural Lu2O3 targeted at a thermal neutron flux of approximately 6 x 10(13) n/cm(2).s for 21 days. 177Lu-EDTMP complex was prepared in high-yield and excellent radiochemical purity (>99%), using EDTMP synthesized and characterized in-house. The complex exhibited excellent in vitro stability at room temperature. Biodistribution studies in Wistar rats showed a rapid skeletal accumulation of injected activity [(1.74 +/- 0.30)% per gram in femur at 3 hours postinjection] with a fast clearance from blood and minimal uptake in any of the major organs. Scintigraphic imaging studies carried out in normal Wistar rats, New Zealand white rabbits, as well as in Beagle dogs also demonstrated significant accumulation of the agent in the skeleton and almost no retention of activity in any other vital organs.

Preparation and bioevaluation of 166Ho labelled hydroxyapatite (HA) particles for radiosynovectomy

The preparation of 166Ho labeled hydroxy apatite (HA) particles for radiosynovectomy applications is described in this paper. 166Ho was prepared by the irradiation of Ho2O3 at a flux of 1.8 x 10(13) neutrons/cm2/s for about 7 days. The irradiation resulted in the production of approximately 17 GBq of 166Ho activity at the end of six hours post end of bombardment and the corresponding specific activity was approximately 3-4 GBq/mg of Ho. The irradiated target was dissolved in 0.1 N HCl solution. Radionuclidic purity was ascertained by high resolution gamma ray spectrometry. HA particles were synthesized and characterized by X-ray diffractometry. Labeling studies were carried out with and without citric acid as a transchelating agent. Radiochemical yield and purity of the 166Ho-HA particles were ascertained by paper chromatography and by paper electrophoresis techniques. Labeling yield of >98% could be achieved at pH 7, with 40 mg of HA particles and 8.6 microg of Ho. 166Ho-HA particles prepared were stable for 72 h. Bio-evaluation of the 166Ho -HA particles were carried out by injecting approximately 74 MBq dose in 200 microL (approximately 8 mg of 166Ho-HA particles) directly into the arthritis induced knee joints as well as into the healthy knee joints of white New Zealand rabbits. Images of the injected joints of the animals recorded using a gamma camera at regular intervals showed good retention. Blood samples were collected from the animals and activity assayed in a scintillation detector. Experiments were also carried out under identical conditions in normal rabbits. In both the cases, it was observed that there was no significant extra articular leakage of the injected activity over the study period of 96 h post injection.

Preparation and biological evaluation of 153Sm-DOTMP as a potential agent for bone pain palliation.

BackgroundDesigning ideal radiopharmaceuticals for use as bone pain palliative agents requires the use of a moderate energy &bgr;− emitter as the radionuclide and a polyaminophosphonic acid as the carrier molecule. Cyclic polyaminophosphonic acid ligands are known for endowing higher thermodynamic stability and kinetic inertness of the radiolabelled agent when complexed with radiolanthanides. AimTo use 153Sm (T1/2=46.27 h, E&bgr;,max=0.81 MeV, E&ggr;=103 keV) as the radioisotope, obtainable at an adequate specific activity and high radionuclidic purity by irradiation of a natural 152Sm2O3 target, and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethylene phosphonic acid (DOTMP) as the carrier ligand. ResultsThe radiolabelling yields under optimized conditions were near quantitative with the additional merit of using a relatively low ligand:metal ratio of 2:1 unlike the 250-fold excess of ligands used in the case of the established agent, 153Sm-EDTMP. Radiochemical purity was retained with insignificant dissociation on storage up to 10 d at room temperature. Biodistribution studies in Wistar rats demonstrated selective skeletal uptake (4.52%±0.49% of injected activity per gram in tibia at 30 min post-injection) with rapid blood clearance and minimal uptake in any of the major organs. No leaching of skeletal activity was observed up to 48 h post-injection. Scintigraphic studies carried out in rabbits also showed significant skeletal accumulation and almost no retention of activity in other vital organs/tissues.

186Re-1,4,8,11-tetraaza cyclotetradecyl-1,4,8,11-tetramethylene phosphonic acid : a novel agent for possible use in metastatic bone-pain palliation

In connection with our work on the development of 186Re-tetra-phosphonates with optimum properties for use in bone pain palliation, a novel cyclic tetraphosphonate derivative, has been synthesized, complexed with 186Re and evaluated with promising results. The ligand, which consists of a cyclic array of tetra-aminomethylphosphonate groups, was synthesized using orthophosphorus acid, 1,4,8,11-tetraazacyclotetradecane and formaldehyde. The labeling conditions with 186Re have been standardized under varying reaction conditions to give maximum yield. In a reaction volume of 1 mL, maximum complexation yield of 98% was observed at pH 2 using 0.1 mg Re (37-370 MBq) for a ligand concentration at 9 x 10(-2) M/L, under heating at 100 degrees C for 30 min with 2 mg of stannous chloride. The complex was found to be stable for 6 days with RC purity remaining approximately 97%. The complex was characterized by paper chromatography in saline and acetone, wherein the R(f) exhibited were 0.9 and 0, respectively. Biodistribution studies of the complex were performed in male Wistar rats. Activity in femur which was observed to be 1.8%/g (equivalent to about 23% of the injected activity in skeleton) at 3 h post injection remained almost constant up to 48 h. Minimum activity was observed in blood and other soft tissues. The complex showed major renal clearance. Scintigraphic images in rabbits after injecting 70-100 MBq of 186Re-CTMP and using a dual head gamma camera were observed to be superior to 186Re-HEDP, prepared by a procedure standardized by us. Insignificant activity was observed in other vital organs. The results suggest the suitability of the complex for further evaluation in higher animals for bone pain palliation.

Development of 68Ga‐labeled fatty acids for their potential use in cardiac metabolic imaging

While [(11)C]palmitate continues to be a promising tracer for cardiovascular Positron Emission Tomography (PET) imaging, unfavourable logistics due to the short half-life of (11)C (20 min) and cumbersome labeling methodologies are the major impediments that limit its widespread use. In order to circumvent such limitations, an attempt has been made to explore the potential of (68)Ga-labeled fatty acid analogs for metabolic imaging owing to the availability of (68)Ga through a (68)Ge/(68)Ga generator on an on-demand basis. In this study, two fatty acid conjugates were synthesized by conjugation of p-SCN-benzyl NOTA with the ω-amino group of 11-amino undecanoic acid and 12-amino dodecanoic acid, respectively, under alkaline conditions. Both derivatives were radiolabeled in high yields with (68)Ga obtained from an in-house (68)Ge/(68)Ga generator. Biodistribution studies in Swiss mice showed reasonable myocardial uptake at 2 min for both derivatives (7.4 ± 2.8% ID/g for 11-carbon fatty acid-NOTA conjugate and 6.4 ± 2.1% ID/g for 12-carbon fatty acid-NOTA conjugate), which cleared rapidly over 30 min. However, significant activity was found in blood for both tracers, with heart/blood ratios observed to be below 0.5 at all time points, diminishing the potential of the synthesized complexes for cardiac imaging.

Studies on batch formulation of a kit for the preparation of the 99mTc-Ubiquicidin (29-41): An infection imaging agent.

The aim of this study was to formulate an indigenous cold kit of Ubiquicidin, UBI (29-41), for easy preparation of (99m)Tc-UBI (29-41) to be used as an infection imaging agent. A two component kit with the peptide and SnCl2 as vial 1 and optimum amount of NaOH as vial 2 was successfully formulated as seen from the consistent radiochemical and pharmaceutical purity of the product over six consecutive batches of kits. The utility of the kit could be demonstrated through in-vitro and in vivo specificity of (99m)Tc-UBI (29-41).

Syntheses and biological evaluation of 99mTc-HYNIC-fatty acid complexes for myocardial imaging

The aim of the present study is to identify a 99mTc-labeled fatty acid tracer which could be a possible substitute of the widely used 123I-labeled fatty acids in studying myocardial metabolism and in detection of myocardial abnormalities in high-risk patients. The relevance of the study stems from the fact that in terms of wider applicability, a 99mTc-tracer is expected to be more advantageous compared to that of a 123I-based one. Two fatty acid (FA)-hydrazinopyridine-3-carboxylic acid (HYNIC) conjugates (11C-FA-HYNIC and 12C-FA-HYNIC) were synthesized and radiolabeled with 99mTc using two different co-ligands system viz. tricine/ethylenediamine diacetic acid (EDDA), and tricine/trisodium triphenylphosphine-3,3′,3′′-trisulfonate (TPPTS), to yield four radiolabeled complexes. While all four 99mTc-HYNIC-complexes showed uptake in the myocardium, 12C-FA-HYNIC-99mTc-EDDA complex showed higher uptake and retention in myocardium compared to other complexes. In general, uptake of the 99mTc-complexes in non-target organs was lower than that of 125I-iodophenyl pentadecanoic acid (IPPA). The 12C-FA-HYNIC-99mTc-EDDA complex, additionally exhibited lower liver accumulation compared to that of 125I-IPPA. Though these features were favorable for cardiac imaging, the heart-to-blood ratio of the complexes were low (<1). Nevertheless, a dynamic SPECT image of 12C-FA-HYNIC-99mTc-EDDA complex in Swiss mouse showed delineation of its myocardium from proximal non-target organs. The results merit further screening of synthetically modified 99mTc-HYNIC fatty acids for myocardial imaging.

Preliminary evaluation of indigenous 90 Y-labelled microspheres for therapy of hepatocellular carcinoma

Background & objectives: Yttrium-90 (90Y)-based radioembolization has been employed to treat hepatocellular carcinoma (HCC) as commercial radioactive glass and polymeric resin microspheres. However, in India and other Asian countries, these preparations must be imported and are expensive, validating the need for development of indigenous alternatives. This work was aimed to develop an economically and logistically favourable indigenous alternative to imported radioembolizing agents for HCC therapy. Methods: The preparation of 90Y-labelled Biorex 70 microspheres was optimized and in vitro stability was assessed. Hepatic tumour model was generated in Sprague-Dawley rats by orthotopic implantation of N1S1 rat HCC cell line. In vivo localization and retention of the 90Y-labelled Biorex 70 microspheres was assessed for seven days, and impact on N1S1 tumour growth was studied by histological examination and biochemical assays. Results: Under optimal conditions, >95% 90Y-labelling yield of Biorex70 resin microspheres was obtained, and these showed excellent in vitro stability of labelling (>95%) at seven days. In animal studies, 90Y-labelled Biorex 70 microspheres were retained (87.72±1.56% retained in liver at 7 days). Rats administered with 90Y-labelled Biorex 70 microspheres exhibited lower tumour to liver weight ratio, reduced serum alpha-foetoprotein level and greater damage to tumour tissue as compared to controls. Interpretation & conclusions: 90Y-labelled Biorex 70 microspheres showed stable retention in the liver and therapeutic effect on tumour tissue, indicating the potential for further study towards clinical use.

Osteogenic Nanofibrous Coated Titanium Implant Results in Enhanced Osseointegration: In Vivo Preliminary Study in a Rabbit Model

A titanium implant surface when coated with biodegradable, highly porous, osteogenic nanofibrous coating has shown enhanced intrinsic osteoinductive and osteoconductive properties. This coating mimics extracellular matrix resulting in differentiation of stem cells present in the peri-implant niche to osteoblast and hence results in enhanced osseointegration of the implant. The osteogenic nanofibrous coating (ONFC) consists of poly-caprolactone, gelatin, nano-sized hydroxyapatite, dexamethasone, ascorbic acid and beta-glycerophosphate. ONFC exhibits optimum mechanical properties to support mesenchymal stem cells and steer their osteogenic differentiation. ONFC was subjected to various characterization tests like scanning electron microscopy, Fourier-transform infrared spectroscopy, x-ray diffractometry, thermal degradation, biomineralization, mechanical properties, wettability and proliferation assay. In pre-clinical animal trials, the coated implant showed enhanced new bone formation when placed in the tibia of rabbit. This novel approach toward implant bone integration holds significant promise for its easy and economical coating thus marking the beginning of new era of electrospun osteogenic nanofibrous coated bone implants.

Comparative bone regeneration study of hardystonite and hydroxyapatite as filler in critical-sized defect of rat calvaria

There is a very significant and well-known clinical need for the development of new osteoinductive materials and the establishment of alternative therapies for the treatment of bone tissue loss or failure resulting from injury or disease as the transplantation of tissues in patients with these injury or disease is severely limited by donor scarcity and is highly associated to the risk of immune rejection and disease transfer. Herein, we studied in vivo bone response by quantifying efficacy and safety of three scaffold variations: (1) nanofibrous polycaprolactone (PCL), (2) PCL–hydroxyapatite (HA), and (3) PCL–hardystonite (HS) against SHAM as the control. Diffraction pattern from TEM showed that native HA and HS were polycrystalline and they leached higher ppm of calcium, phosphorus and zinc as compared to PCL–HA and PCL–HS in which HA, HS were incorporated in PCL nanofibers. The study was performed on 8 mm critical-sized rat calvarial defects analyzed at two timepoints, 6 and 12 weeks. The bone regenerated by PCL–HS promoted higher growth than that by SHAM and PCL alone at 12 weeks with comparable bone mineral density in all groups at both time points. PCL–HS showed potential for bone growth similar to that for PCL–HA. Histology data showed dense bone interface being formed at the site in both the PCL–HS and PCL–HA groups. Therefore, HS was found to have comparable functionality with commercial HA. No significant differences were noted in any of the blood parameters but there were differences in serum biochemistry parameters of triglyceride and creatine levels among groups, which are indirectly related to bone forming potential and directly to safety of kidney function, while the other parameters were unchanged and within the normal range. Thus, we conclude that the HS material can be a suitable substitute for bone tissue engineering.