Preliminary evaluation of technetium-99m-labeled ceftriaxone: infection imaging agent for the clinical diagnosis of orthopedic infection.

OBJECTIVE: In this study we sought to assess the efficacy of a technetium-99m (Tc-99m)-labeled third-generation cephalosporin as an infection imaging agent in the accurate detection of the sites of bacterial infection in vivo. DESIGN: Ceftriaxone (CRO) was formulated into a ready-to-use single-vial cold kit with a shelf-life of over 6 months and was successfully labeled with technetium. The radiolabeled drug, Tc-99m-CRO, was subjected to the following preclinical evaluations: radiochemical purity, in vitro and in vivo stability, bacterial binding assay, and pharmacokinetic studies in animals and in human patients. RESULTS: The kit formulation exhibited excellent radiolabeling efficiency (∼99%) and high in vitro and in vivo stability. The radiolabeled drug exhibited slow blood clearance (12% at 4 h), and the high protein binding and excretion pattern of the labeled formulation mimics the reported pharmacokinetic profile of the drug alone. In the animal model, scintigraphy scans showed higher uptake of the radiopharmaceutical in infectious lesions, even at 1 h post-administration, in comparison to inflammatory lesions. The clinical evaluation of Tc-99m-labeled CRO showed a diagnostic accuracy of 83.3%, and a sensitivity and specificity of 85.2% and 77.8%, respectively. CONCLUSIONS: This kit formulation has the potential for imaging bacterial infections with much higher sensitivity and specificity as compared to other Tc-99m-labeled antibiotics available as convenient ready-to-use kits in routine clinical practice.

Designed peptides as model self-assembling nanosystems: characterization and potential biomedical applications.

Synthesis of nanomaterials via 'molecular self-assembly' allows one to define the properties of the nanomaterial by rational design of the individual constituents. Use of peptides for self-assembly offers the ease of design and synthesis, and provides higher biofunctionality and biocompatibility to nanomaterials. Our work focused on the synthesis, characterization and potential biomedical applications of small self-assembled peptide-based nanosystems. We demonstrated that dipeptides containing the conformational restricting residue alpha,beta-dehydrophenylalanine, self-assembled into nanovesicular and nanotubular structures. The nanosystems could encapsulate and release anticancer drugs, showed enhanced stability to proteinase K degradation, a property crucial for them to have a high in vivo half-life, and exhibited no cytotoxicity towards cultured mammalian cells. The dipeptide nanostructures were easily taken up by cells and could evade uptake by reticuloendothelial systems when injected into healthy laboratory animals. Thus, small self-assembling peptides may offer novel scaffolds for the future design of nanostructures with potential applications in the field of drug delivery.

Evaluation of ISCOM matrices clearance from rabbit nasal cavity by γ scintigraphy.

Immune stimulating complexes and/or ISCOM matrices (adjuvant nanoparticles without antigen as a structural component) found potential applications as nasal vaccine adjuvant/delivery system owing to virus like particulate structure and saponin as potent Th1 adjuvant. One of important limiting factor for nasal vaccine delivery is the limited time available for absorption within the nasal cavity due to mucociliary clearance. In this report the clearance rate of ISCOM matrices from nasal cavity of rabbit was determined by gamma scintigraphy. ISCOM matrices were radiolabelled with (99m)Tc by direct labelling method using stannous chloride as a reducing agent. (99m)Tc labelled ISCOM matrices were administered into the nostril of female New Zealand rabbits and 1 min static views were repeated each 15 min until 4h. Clearance rate of ISCOM matrices from nasal cavity was calculated after applying the physical decay corrections. The mean labelling efficiency for ISCOM matrices were calculated as approximately 58.4%. ISCOM matrices showed slower clearance rate compared to sodium pertechnetate control solution (p<0.005) from nasal cavity that may be due to particulate and hydrophobic characters of ISCOM particles even though it was also cleared within 4h from nasal cavity. Mucoadhesive ISCOM formulations that retain in nasal cavity for longer duration of time may reduce the dose/frequency of vaccine for nasal immunization.

Formulation and development of hydrodynamically balanced system for metformin: in vitro and in vivo evaluation.

The objective of the present study was to develop a hydrodynamically balanced system of metformin as a single unit floating capsule. Various grades of low-density polymers were used for the formulation of this system. They were prepared by physical blending of metformin and the polymers in varying ratios. The formulation was optimized on the basis of in vitro buoyancy and in vitro release in simulated fed state gastric fluid (citrate phosphate buffer pH 3.0). Effect of various release modifiers was studied to ensure the delivery of drug from the HBS capsules over a prolonged period. Capsules prepared with HPMC K4M and ethyl cellulose gave the best in vitro percentage release and were taken as the optimized formulation. By fitting the data into zero order, first order and Higuchi model it was concluded that the release followed zero order release, as the correlation coefficient (R(2) value) was higher for zero order release. It was concluded from R(2) values for Higuchi model that drug release followed fickian diffusion mechanism. In vivo studies were carried out in rabbits to assess the buoyancy, as well as the pharmacokinetic parameters of the formulation using gamma scintigraphy. The formulation remained buoyant during 5h of study in rabbits. The comparative pharmacokinetic study was performed by administration of the optimized HBS capsules and immediate release capsules, both with radiolabeled metformin, using gamma counter. There was an increase in AUC in optimized HBS capsules of metformin when compared with immediate release formulation.

Formulation and development of floating capsules of celecoxib: in vitro and in vivo evaluation.

The objective of the present study was to develop a hydrodynamically balanced system for celecoxib as single-unit floating capsules. Various grades of low-density polymers were used for formulation of these capsules. The capsules were prepared by physical blending of celecoxib and the polymer in varying ratios. The formulation was optimized on the basis of in vitro buoyancy and in vitro release in citrate phosphate buffer pH 3.0 (with 1% sodium lauryl sulfate). Capsules prepared with polyethylene oxide 60K and Eudragit RL100 gave the best in vitro percentage release and were used as the optimized formulation. By fitting the data into zero-order, first-order, and Higuchi models, we concluded that the release followed zero-order kinetics, as the correlation coefficient (R value) was higher for zero-order release. For gamma scintigraphy studies, celecoxib was radiolabeled with technetium-99m by the stannous reduction method. To achieve the maximum labeling efficiency the process was optimized by studying the reaction at various pH conditions and stannous concentration levels. The radiolabeled complex was added to the optimized capsule, and dissolution studies were performed to ensure that there was no leaching of radioactivity from the capsules. Gamma imaging was performed in rabbits to assess the buoyancy of the optimized formulation. The optimized formulation remained buoyant during 5 hours of gamma scintigraphic studies in rabbits.

Delivery of hydrophobised 5-fluorouracil derivative to brain tissue through intravenous route using surface modified nanogels.

Random copolymeric micelles composed of N-isopropylacrylamide (NIPAAM) and N-vinylpyrrolidone (VP) cross-linked with N,N'-methylenebisacrylamide (MBA) have been used as nanogel carriers to encapsulate N-hexylcarbamoyl-5-fluorouracil (HCFU), a prodrug of 5-FU, and have been targeted to brain tissue across blood-brain barrier (BBB) after coating with polysorbate 80. Accumulation of nanogel particles in the brain and other tissues of "strain A" mice had been monitored by radiolabeling of nanogels with (99m)Tc. Gamma Scintigraphic technique was also performed to see the distribution of (99m)Tc labeled nanogels in the brain. The retention time in blood appeared to be slightly longer for coated nanogels than that of uncoated nanogels though the accumulation of coated nanogels in the RES was more or less same as that of uncoated nanogels. The blood however had almost double accumulation of polysorbate 80 coated nanogels in the initial 5 min compared to that shown by uncoated nanogels. We speculate that coating of nanogels with polysorbate 80 alters the surface properties of nanogels, which results in relatively higher uptake in the brain tissue. The studies revealed that a large portion of (99m)Tc labeled HCFU loaded nanogels are accumulated in the RES (lung, liver and spleen). The accumulation of the labeled nanogels in the brain, however, is much less compared to RES and it has been found that while an amount of uncoated labeled nanogels was found to be 0.18% of the injected dose, it increased to 0.52% on coating with polysorbate 80. The optimal amount of polysorbate 80 added to nanogels for the maximum delivery of particles to brain was found to be 1% w/w. These results were further supported by the gamma scintigrams of New Zealand rabbits. Thus, the present nanogel system has opened a new avenue for poorly soluble drugs to be targeted to brain by coating the particles with polysorbate 80.