Evaluating the potential of kit-based 68Ga-ubiquicidin formulation in diagnosis of infection: a pilot study68Ga.

OBJECTIVE: The aim was to evaluate the diagnostic potential of Ga-ubiquicidin positron-emission tomography/computed tomography (PET/CT) in imaging patients with infection. MATERIALS AND METHODS: Ga-NOTA-ubiquicidin (Ga-UBI) was prepared by addition of freshly eluted Ga-chloride from Ge/Ga generator into the NOTA-ubiquicidin vial and incubated at room for 15 min at 90°C. After compounding of the radiopharmaceutical, quality control using instant thin-layer chromatography, culture and endotoxin estimation was performed. Patients with suspected infection associated with diabetic foot, cellulitis and fracture were selected for the pilot study investigation to evaluate the ability of the tracer Ga-UBI in localization at infection sites. The PET/CT findings were compared with other diagnosis like microbial culture reports and bone scintigraphy to evaluate true positives or negatives in the study. RESULTS: The current study demonstrated the potential of kit-based Ga-UBI in localization of infection sites in most of the patients proven positive for infection on culture tests and bone scintigraphy. The kit could offer radiolabeling yield more than 95% in 15 min incubation at 90°C. Quality control rendered the kit as a clinical grade preparation with endotoxin content less than 10 EU/ml and sterility up to 14 days of culture incubation. Eight of 10 patients underwent culture test and showed positive results. Two patients had undergone three-phase bone scan as an indirect sign of active infection. Ga-UBI PET/CT showed tracer localization in four of eight culture-positive patients. Tracer localization was observed in one of two patients whose culture reports were not available. Ga-UBI failed to identify infection in four patients with culture-positive results. CONCLUSION: The present study concluded that Ga-UBI prepared using NOTA-UBI kit is a potential agent in targeting infections associated with disease conditions including diabetic foot, cellulitis and fracture. The patient selection holds significance in accurate diagnosis using Ga-UBI PET/CT.

68Ga-NOTA-ubiquicidin fragment for PET imaging of infection: From bench to bedside.

This study explores the possibility of formulation of a cold kit for fast and easy preparation of a PET radiopharmaceutical, 68Ga-NOTA-UBI (29-41) for clinical translation. In this study, Circular dichroism (CD) spectroscopy to study conformation of NOTA-UBI (29-41) and its comparison with conformation of UBI (29-41) was done. Pharmaceutical grade cold kits of NOTA-UBI (29-41) were formulated for radiolabeling with 68Ga and necessary quality control tests were carried out. 68Ga-NOTA-UBI (29-41) could be prepared in >90% radiochemical yield and radiochemical purity using cold kits of NOTA-UBI (29-41). In vitro and in vivo evaluation of 68Ga-NOTA-UBI (29-41) was done to demonstrate specificity of the agent for imaging infection. Kits were utilized for preparation of patient dose of 68Ga-NOTA-UBI (29-41). Simple instant thin layer chromatography (ITLC) method for estimating radiolabeling yield of 68Ga-NOTA-UBI (29-41) at hospital radiopharmacy was demonstrated. Clinical evaluation was done in patients with suspected infection. 148-185 MBq of 68Ga-NOTA-UBI (29-41) was injected intravenously in three patients. 68Ga-NOTA-UBI (29-41) uptake could clearly delineate infection foci from non target normal tissues. This is the first report on formulation of a cold kit of NOTA-UBI (29-41) for preparation of 68Ga labeled NOTA-UBI(29-41) at hospital radiopharmacy for infection imaging. Initial clinical evaluation reveal it to be a prospective agent for imaging infection.

Gallium-68 labeled Ubiquicidin derived octapeptide as a potential infection imaging agent.

INTRODUCTION: Gallium-68 based infection imaging agents are in demand to detect infection foci with high spatial resolution and sensitivity. In this study, Ubiquicidin derived octapeptide, UBI (31-38) conjugated with macrocyclic chelator NOTA was radiolabeled with 68Ga to develop infection imaging agent. METHODS: Circular dichroism (CD) spectroscopy was performed to study conformational changes in UBI (31-38) and its NOTA conjugate in a "membrane like environment". Radiolabeling of NOTA-UBI (31-38) with 68Ga was optimized and quality control analysis was done by chromatography techniques. In vitro evaluation of 68Ga-NOTA-UBI (31-38) in S. aureus and preliminary biological evaluation in animal model of infection was studied. Initial clinical evaluation in three patients with suspected infection was carried out. RESULTS: 68Ga-NOTA-UBI (31-38) was prepared in high radiochemical yields and high radiochemical purity. In vitro evaluation of 68Ga-NOTA-UBI (31-38) complex in S. aureus confirmed specificity of the agent for bacteria. Biodistribution studies with 68Ga-NOTA-UBI (31-38) revealed specific uptake of the complex in infected muscle compared to inflamed muscle with T/NT ratio of 3.24 ±â€¯0.7 at 1 h post-injection. Initial clinical evaluation in two patients with histopathologically confirmed infective foci conducted after intravenous injection of 130-185 MBq of 68Ga-NOTA-UBI (31-38) and imaging at 45-60 min post-injection revealed specific uptake at the sites of infection and clearance from vital organs. No uptake of tracer was observed in suspected infection foci in one patient, which was proven to be aseptic and served as negative control. CONCLUSION: This is the first report on 68Ga labeled NOTA-UBI (31-38) fragment for prospective infection imaging.

Clinical utility of 99mTc-ubiquicidin (29-41) as an adjunct to bone scan in differentiating infected versus noninfected loosening of prosthesis before revision surgery.

PURPOSE: The aim of this study was to evaluate the utility of Tc-ubiquicidin (Tc-UBI) (29-41) as an adjunct to an methylene diphosphonate (MDP) bone scan in differentiating septic versus aseptic loosening in patients with painful prosthesis posted for revision surgery. PATIENTS AND METHODS: A two-vial cold kit of UBI (29-41) was prepared and utilized for the preparation of patient dose of Tc-UBI (29-41). Twenty two patients with painful hip or knee prosthesis and scheduled for revision surgery were included in the study. Overall, 370-555 MBq of Tc-UBI (29-41) was injected intravenously in all the patients. A blood pool image at 20 min after injection was followed by spot views of the suspected region of infection (target) and a corresponding normal area (nontarget) at 60 min. All patients underwent a routine Tc-MDP three-phase whole-body bone scan, followed by single-photon emission computed tomography/computed tomography of the prosthesis within a week of the Tc-UBI (29-41) study. For Tc-UBI scans, a visual score (0-3) was used to categorize studies as positive or negative, with scores of 0 (minimal or no uptake; less than soft tissue or contralateral extremity) and 1 (mild; equivalent to soft tissue or contralateral extremity) being considered negative and scores of 2 (moderate; uptake greater than soft tissue or contralateral extremity, but less than the liver) or 3 (intense; uptake greater than soft tissue or contralateral extremity and equivalent to the liver) being considered positive. The final correlation was on the basis of bacterial culture as the major criterion and the results of clinical tests, radiography, fluorine-18-fluorodeoxyglucose PET-CT, and three-phase bone scanning as the minor criteria. RESULTS: In all, 22 studies were carried out with Tc-UBI (29-41). Of these, 16 scans were considered positive and six were negative for infection foci. All negative scans were subsequently confirmed to be true negative. Adverse reactions were not observed during image acquisition and within 5 days after the study. The overall sensitivity, specificity, and positive and negative predictive values were 100, 85.7, 93.75, and 100%, respectively. A combination of an MDP bone scan and UBI scans was considered to yield maximum confidence toward reporting for the presence of infection. CONCLUSION: Patient dose of Tc-UBI (29-41) was prepared successfully and a simple quality control method to check radiolabeling yield was used at the hospital radiopharmacy. Tc-UBI (29-41) showed promise in localizing foci of infection, with optimal visualization at 20-60 min, for the evaluation of prosthesis loosening.

Radiolabeling and Preliminary Evaluation of Ga-68 Labeled NODAGA-Ubiquicidin Fragments for Prospective Infection Imaging.

PURPOSE: The present work was aimed at the development of prospective positron emission tomography (PET) agents for infection imaging. Towards this aim, ubiquicidin (UBI) fragments conjugated with the macrocyclic NODAGA chelator were radiolabeled with Ga-68 and evaluated. PROCEDURES: Conformations of custom synthesized NODAGA-UBI (29-41) and NODAGA-UBI (31-38) conjugates were compared with UBI (29-41) by circular dichroism (CD) spectroscopy. Optimization of labeling of NODAGA conjugates of UBI peptides with Ga-68 was performed and quality control analysis was carried out by chromatography techniques. In vitro uptake of [68Ga] NODAGA-UBI (29-41) and [68Ga]NODAGA-UBI (31-38) was studied in Staphylococcus aureus cells. In vivo distribution of [68Ga]GaCl3 and [68Ga]NODAGA-UBI complexes was performed in normal Swiss mice. RESULTS: Conformations of NODAGA-UBI (29-41) and NODAGA-UBI (31-38) conjugates were found to be similar to UBI (29-41). NODAGA-UBI conjugates could be consistently labeled with Ga-68 in high radiochemical yields (>95 %) with high radiochemical purity (>95 %). [68Ga]NODAGA-UBI (29-41) and [68Ga]NODAGA-UBI (31-38) complexes showed retention time of 14 and 14.5 min, respectively, by HPLC radiochromatogram. Specific uptake of [68Ga]NODAGA-UBI fragments was observed in S.aureus cells. Greater than 64 % of the injected dose was cleared via the renal route at 1 h post injection, and no significant uptake in vital organs of mice was observed with both the agents. CONCLUSION: This is the first report on Ga-68 labeled NODAGA-UBI fragments for infection imaging and the agents hold tremendous prospect in PET imaging.

Synthesis and evaluation of a (68)Ga labeled folic acid derivative for targeting folate receptors.

Present work evaluates the potential of a newly synthesized (68)Ga-NOTA-folic acid conjugate for PET imaging of tumors over-expressing folate receptors (FRs). NOTA-folic acid conjugate was synthesized and characterized. It was radiolabeled with (68)Ga in ≥ 95% radiolabeling yields. In vitro cell binding studies showed a maximum cell uptake of 1.7±0.4% per million KB cells which was completely blocked on addition of cold folic acid showing specificity towards the FRs. However, further studies in tumor xenografts are warranted in order to assess the potential of (68)Ga-folic acid complex for imaging tumors over-expressing FRs.

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).