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Biomedical subjects

G Samuel

Publications and source records attributed to G Samuel.

At least 19 recordsLinked to original sources
PubMed2006

Surface modification of polystyrene using polyaniline nanostructures for biomolecule adhesion in radioimmunoassays.

The selection of an appropriate surface as a solid phase for coupling antibodies is a critical step in the development of solid-phase immunoassays. Availability of a new method of preactivating the surface of polystyrene tubes with a layer of another polymer for enhanced immobilization of antibodies seems to be promising. In this paper, we report the activation of a polystyrene surface using a layer of polyaniline and its effect on immobilizing antibodies for use as a solid phase in a T3 immunoassay. The modified surface on the polystyrene was characterized by optical absorption, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The modified tubes were coated with antibody and evaluated for their performance in the assay and validated for radioimmunoassay of T3. AFM images of the modified surface showed an enhancement in the surface roughness (Ra of 20.2 nm), as compared to an unmodified surface (Ra of 6 nm), allowing more adsorption of antibodies to the surface. XPS revealed the presence of N (binding energy approximately 400 eV) on the modified surface, which could help the antibody molecules to bind to these preactivated (modified) tubes. The modified tubes, when coated with antibody, not only showed an increase in the binding with the radioiodinated tracer but also improved the precision of coating the antibody. The present method of activating polystyrene surfaces is simple, does not involve severe chemical treatment, and may have wide applicability to functionalize other supports for immobilizing biomolecules.

Adhesiveness↗
PubMed2005

Development of coated tubes RIA for serum T3 (tri-iodothyronine) for production scale.

A coating procedure that could provide immobilization of antibodies, with increased binding capacity, that is cost effective, simple, robust, and appropriate for production scale application, is described. This coating approach of T3 antibodies to the polystyrene tubes has been systematically investigated to determine its utility for the development of coated tube Radioimmunoassay (RIA) for T3 in human serum. Further, the results obtained by the developed coating procedure are found to be comparable with those obtained by the "gold standard," the liquid phase RIA for T3. The coating procedure is completed in three major steps, each step involving an overnight incubation. The normal rabbit gamma-globulins are physically adsorbed onto the polystyrene tubes and incubated. After washing, a second antibody (goat anti-rabbit antiserum) is added and incubated. To this antigen specific antibody is added (T3 antibody produced in rabbit) and further incubated. Finally, the non-specific sites on the tubes are saturated by the blocking solution. The concentration of normal rabbit globulin, titers of second antibody and T3 antibody, and time required for coating are optimized to arrive at a suitable coating protocol. The coated tubes were evaluated for precision, reproducibility, and stability. Various parameters such as total reaction volume, incubation time and temperature, total number and volume of washings, concentration of 8-anilino-1-naphthalene sulfonic acid (ANS), and quantity of tracer per tube are optimized to arrive at a suitable standard curve. The optimized assay is validated for the quality control parameters such as intra- and inter-assay variations, recovery, and parallelism. The developed coated tubes assay had an assay range of 0.3-4.8 ng/mL with a sensitivity of 0.3 ng/mL at 90% B/B0. Batch to batch variation in coating was < 10%. The coated tubes were stable up to 1 year, which is adequate for production scale.

Animals↗
PubMed2002

177Lu labelled polyaminophosphonates as potential agents for bone pain palliation.

Polyphosphonate ligands labelled with radioisotopes decaying by moderate energy beta emission have shown utility as palliative agents for painful bone metastasis. 177Lu (T(1/2)=6.71 d, Ebetamax=497 keV) has radionuclidic properties suitable for use in palliative therapy of bone metastasis. 177Lu was produced at a high specific activity and excellent radionuclidic purity by thermal neutron bombardment of a target prepared from natural Lu. Three polyaminomethylene phosphonate ligands, abbreviated as EDTMP, DTPMP and TTHMP, were synthesized and radiolabelled with 177Lu. Complexation parameters were optimized to achieve maximum yields (97-99.5%). All the complexes were found to retain their stability at room temperature even 14 days after preparation. Biodistribution studies of the complexes were carried out in Wistar rats. All the complexes showed significant bone uptake (6-6.5%/g in tibia at 3 h post-injection (p.i.)) with rapid clearance from blood and minimum uptake in soft tissues. These studies reveal that 177Lu complexes with the synthesized ligands have a potential use in palliative treatment of painful bone metastasis.

Animals↗
PubMed2001

Tc-99m and Re-186 complexes of tetraphosphonate ligands and their biodistribution pattern in animal models.

The syntheses of four alpha-aminomethyl phosphonates and their complexation studies with (99m)Tc and (186/188)Re are reported. Complexation conditions were standardized to give maximum yields, which ranged from 90-97%. The yields of complexation were estimated by paper chromatography. The (99m)Tc complexes were stable for more than 4 h, while the (186/188)Re complexes were stable for 3-8 days when stored at 4 degrees C. Biodistribution of these complexes in Wistar rats were carried out, and the uptake in bone and other soft tissue are detailed. Bone uptake of the (99m)Tc complexes varied from 40-60% at 30 min postinjection depending on the ligands. The uptake in soft tissue was minimum with all the complexes. A comparison of the biodistribution studies of the (99m)Tc complexes with that of the well-established radiopharmaceutical (99m)Tc-MDP was carried out for the purpose of evaluating the efficacy of the radiopharmaceutical preparation with the complexes of these ligands. The bone uptake of the (186/188)Re complexes varied from 19-28% corresponding to 1.6-3% per g at 3 h postinjection. The residual activity in both (99m)Tc and (186/188)Re complexes showed renal clearance.

Animals↗
PubMed2001

Potential (166)Ho radiopharmaceuticals for intravascular radiation therapy (IVRT)-I: [(166)Ho] holmium labeled ethylene dicysteine.

The use of beta(-) emitting radionuclides in the control of restenosis in post angioplasty patients is currently under intense investigation at many leading cardiovascular research centers. (32)P coated metallic stents, (192)Ir wire source and balloons filled with an appropriate radionuclide solution such as of (188)Re, attached to catheter are being studied. (166)Ho has comparable radionuclidic properties to that of (188)Re, can be more easily produced and hence is an attractive alternative to (188)Re. Ethylene dicysteine complex of (166)Ho was prepared and its pharmacological behavior studied. Optimum conditions for the preparation of complex with respect to the reaction time, ligand concentration, pH of the reaction mixture as well as reaction temperature were standardized. The stability of the labeled complex at room temperature as well as at 4 degrees C was determined. Biodistribution pattern of the injected complex in Wistar rats was estimated at 10 min, 30 min and 3 h post injection. This study indicated that >90% of the injected (166)Ho-EC complex was excreted in urine within 3 h post injection, with insignificant retention in any major organ. These studies reveal that (166)Ho-EC could be a viable substitute for (188)Re compounds in radioactive liquid-filled balloon IVRT.

Animals↗
PubMed2001

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.

Analgesics↗
PubMed2001

A novel [186/188Re]-labelled porphyrin for targeted radiotherapy.

The concept of labelling a porphyrin, a tumour-avid agent, with a radionuclide to evaluate its potential as a therapeutic modality is reported. A novel water-soluble porphyrin, namely meso-tetrakis[3,4-bis(carboxymethyleneoxy)phenyl]porphyrin, with suitable dicarboxylic acid groups as aromatic substituents in the periphery, was synthesized and characterized. The labelling of this porphyrin with 186/188Re, a beta(-) emitter, was optimized by varying the reaction conditions. The complexation yield was >98% as estimated by paper chromatography in acetone and in saline. The radiochemical purity was found to remain at >98% when stored at 4 degrees C for 24 h. Biodistribution studies in Swiss mice bearing fibrosarcomas showed an uptake of approximately 3.5% per gram of tumour at 30 min post-injection. This uptake in the tumour was retained until 24 h post-injection with major activity showing renal clearance; no significant activity was present in other organs of interest. The tumour/blood and tumour/muscle ratios were observed to be 38 and 5, respectively, at 24 h post-injection, thereby indicating a possible therapeutic potential for tumours.

Animals↗
PubMed2000

Studies on the preparation and stability of samarium-153 propylene diamine tetramethylene phosphonate (PDTMP) complex as a bone seeker.

Propylene diamine tetra methylene phosphonate (PDTMP) was synthesised by modifying a method reported for the synthesis of EDTMP. Complexation of the synthesised phosphonate ligand with 153Sm was carried out by varying the experimental parameters and the complex was radiochemically characterized. Biodistribution studies showed that the uptake by bone in rats was 2% per g of bone, which was retained upto 48 h. The uptake by other organs was insignificant, except by the liver which showed a slightly higher absorption.

Animals↗
PubMed2000

[(186/188)Re] rhenium-ethylene dicysteine (Re-Ec): preparation and evaluation for possible use in endovascular brachytherapy.

188ReO(4)(-), (188)Re-MAG(3), and (188)Re-DTPA are currently under investigation as radiation sources in liquid-filled balloons for prevention of restenosis following coronary angioplasty. Because (99m)Tc-labeled ethylene dicysteine (EC) is a well-established agent for renal tubular function imaging, the use of [(188)Re] rhenium-labeled EC as a potential agent for prevention of restenosis after angioplasty is worth evaluation. In this article, the preparation and pharmacological behavior of [(188/186)Re]Re complex of EC are reported. The yield of the Re complex was optimized by varying the parameters of complexation. The complex prepared under the optimized conditions was found to be stable over a period of 7 days when stored at pH 2 and at 4 degrees C. The pharmacological behavior of [(188/186)Re]Re-EC confirms its similarity to (188)Re-MAG(3) and its superiority over (188)ReO(4)(-) for use in endovascular brachytherapy.

Animals↗
PubMed2000

188Re-ethylene dicysteine: a novel agent for possible use in endovascular radiation therapy.

Several agents, such as 188ReO4-, 188Re-MAG3 and 188Re-DTPA are currently under investigation as radiation sources in liquid-filled balloons for prevention of restenosis following coronary angioplasty. Bearing in mind the risk factor associated with leakage of radioactivity in the event of balloon rupture, the criteria sought in selecting suitable agents for endovascular radiation therapy (EVRT) are rapid clearance and low dose to vital organs. Since 99Tcm labelled ethylene dicysteine (EC) is a well established agent for renal tubular function imaging, the use of 186Re-ethylene dicysteine as a potential agent for prevention of restenosis after angioplasty has been evaluated previously. Therefore, it was of interest to evaluate the applicability of the more potential isotope of rhenium, 188Re, a high energy beta-emitter (Ebetamax = 2.12 MeV) with a suitable T 1/2 = 16.9 h, obtainable carrier-free from the 188W-188Re generator, as an attractive and alternative radionuclide for labelling with L,L-EC. In this paper, the preparation and pharmacological behaviour of the 188Re complex of ethylene dicysteine are reported. The complex can be prepared in high yields (99.5%) under optimized conditions of pH 2-3, at a ligand concentration of 15 mM, 50 microg (0.18 mM) carrier rhenium and using 2 mg x mL(-1) stannous chloride. On storage at 4 degrees C, the RC purity was more than 97% after 48 h when prepared under optimum conditions. Biodistribution studies in Wistar rats showed the desired characteristics of fast blood clearance and low retention of activity in the vital organs (< 2% in intestine, < 1% in stomach, < 0.5% in liver) with a high renal excretion (90.65+/-0.6%) at 3 h post-injection. These results confirm the advantages of using the 188Re-EC complex compared with perrhenate and other rhenium radiopharmaceuticals currently being used in balloons for EVRT.

Angioplasty, Balloon, Coronary↗
PubMed1999

Technetium-99m complexes of polydentate amine-pyrrole and amine-thiophene ligands.

Novel polydentate amine-pyrrole and amine-thiophene ligands were synthesized and characterized by 1H and 13C NMR spectroscopy. Radiochemical studies with 99mTc were carried out at 0.1-100 microM of technetium. Complexation yields were estimated from thin layer chromatography (TLC), paper electrophoresis, and solvent extraction studies. The 99mTc complexes formed were found to be neutral and lipophilic. Complexes with the corresponding imine-ligands were formed in lower yields. Biodistribution studies of the 99mTc complexes of these ligands showed no significant uptake in brain or heart, and the clearance was mainly through the hepatobiliary system.

Animals↗
PubMed1999

Radiochemical studies of 99mTc complexes of modified cysteine ligands and bifunctional chelating agents.

The synthesis of four novel ligands using the amino-acid cysteine and its ethyl carboxylate derivative is described. The synthetic method involves a two-step procedure, wherein the intermediate Schiff base formed by the condensation of the amino group of the cysteine substrate and salicylaldehyde is reduced to give the target ligands. The intermediates and the final products were characterized by high resolution nuclear magnetic resonance spectroscopy. Complexation studies of the ligands with 99mTc were optimized using stannous tartrate as the reducing agent under varying reaction conditions. The complexes were characterized using standard quality control techniques such as thin layer chromatography, paper electrophoresis, and paper chromatography. Lipophilicities of the complexes were estimated by solvent extraction into chloroform. Substantial changes in net charge and lipophilicity of the 99mTc complexes were observed on substituting the carboxylic acid functionality in ligands I and II with the ethyl carboxylate groups (ligands II and IV). All the ligands formed 99mTc complexes in high yield. Whereas the complexes with ligands I and II were observed to be hydrophilic in nature and not extractable into CHCl3, ligands III and IV resulted in neutral and lipophilic 99mTc complexes. The 99mTc complex with ligand II was not stable and on storage formed a hydrophilic and nonextractable species. The biodistribution of the complexes of ligands I and II showed that they cleared predominantly through the kidneys, whereas the complexes with ligands III and IV were excreted primarily through the hepatobiliary system. No significant brain uptake was observed with the 99mTc complexes with ligands III and IV despite their favorable properties of neutrality, lipophilicity, and conversion into a hydrophilic species. These ligands offer potential for use as bifunctional chelating agents.

Animals↗
PubMed1993

Rod photoreceptor cGMP-phosphodiesterase: analysis of alpha and beta subunits expressed in human kidney cells.

The bovine alpha and murine beta subunits of rod-photoreceptor cGMP-phosphodiesterase (PDE alpha and PDE beta) were expressed in adenovirus-transformed 293 human embryonic kidney cells. RNA blots from transfected cells showed transcripts of 3.0 and 2.8 kb corresponding to PDE alpha and PDE beta, respectively. Protein expression was analyzed by using affinity-purified antibodies against cGMP-PDE on immunoblots and by immunoprecipitation. PDE alpha and PDE beta exhibited the expected mobility (and thus apparent molecular size) and had cGMP hydrolytic activity. Reconstitution of the PDE alpha beta heterodimer with the expressed proteins increased by approximately 6-fold the activity of the individual alpha and beta subunits. Addition of expressed beta subunit to retinal extracts from 9- to 10-day-old rd/rd mice (which have only normal alpha and gamma subunits of rod cGMP-PDE and thus minimal activity) increased enzyme activity by approximately 3-fold. Our results therefore demonstrate that photoreceptor-specific cGMP-PDE can be synthesized in human kidney cells with consequent expression of enzymatic activity.

3',5'-Cyclic-GMP Phosphodiesterases↗