(111)Indium Labelling of Recombinant Activated Coagulation Factor VII: In Vitro and Preliminary In Vivo Studies in Healthy Rats.

The aim of this study is to investigate whether (111)Indium-labelled recombinant FVIIa (rFVIIa) could be a potential radiopharmaceutical for localization of bleeding sources. DTPA-conjugated rFVIIa was radiolabelled with (111)In chloride. In vitro binding efficiency of (111)In-DTPA-rFVIIa to F1A2-Mab-sepharose was 99% in buffer, while it was 88-82% in serum. The binding efficiency of (111)In-DTPA-rFVIIa to TF (1-209)-sepharose was 48% in buffer whereas 39%-36% in serum, respectively. In vivo experiment was conducted in healthy rats, and gamma camera images were taken immediately after iv. administration of 1.6-1.8 MBq (111)In-DTPA-rFVIIa up to 120-130 min. Five min after administration of (111)In-DTPA-rFVIIa, percentage of (111)In activity was 6.0% in the cardiac region and 24.5% in the liver region. After 2 hours activity was decreased to 3.3% in heart while it had increased to 42.0% in the liver. The (111)In-DTPA-rFVIIa might be a potential radiopharmaceutical for visualisation of tissues with significant TF expression such as acute bleeding lesions in the gastrointestinal tract.

Easy and efficient (111)indium labeling of long-term stored DTPA conjugated protein.

UNLABELLED: The labelling efficiency of long-term stored DTPA-conjugates has not been reported previously even though DTPA has been in extensive use as metal chelator in the development of radiopharmaceuticals and contrast agents. DTPA is often used as a bifunctional chelating agent conjugated to tumor targeting vehicles such as monoclonal antibodies and receptor directed peptides. The purpose of this study was to monitor the labelling efficiency of a DTPA-conjugate on long-term storage using 111In-chloride at two different temperatures and incubation times for the In-labelling. METHOD: Cyclic-diethylene-triamine-pentaacetic acid (cDTAP) was conjugated to a polyclonal immunoglobulin-G (IgG) in borate buffer, pH 8.2 at +4?C for 4 hours. Then the DTPA-conjugate was dialyzed against 50 mmol/l sodium citrate buffer saline, pH 6.0 and stored at -80° C in aliquots of 1 mg/0.5 ml. The DTPA-conjugate was labeled with 111In-chloride in citrate buffer, pH 6. The labelling reaction was incubated at room temperature (RT) for 30 min and at +4?C for 90 min. Determination of labelling efficiency was performed using ITLC and an instant chromatography scanner equipped with a NaI crystal. The labelling efficiency of the DTPA-conjugate was monitored every third month for 12 months. RESULTS: The median labelling efficiencies varied between 92 and 96% during the whole period. The two combinations of incubation times and temperatures (30 min at RT and 90 min at +4°C) had no affect on labelling efficiency of the DTPA-conjugate, stored for 12 months. CONCLUSION: Our study shows that 111In-labelling can easily be performed within 30 min at RT for thermo-stable proteins like polyclonal, DTPA-conjugated IgG stored long-term at -80°C with a high 111In-labelling efficiency.

Radiographic absorptiometry for pre-screening of osteoporosis in patients with low energy fractures.

Dual energy X-ray absorptiometry (DEXA) is the most accurate method and thus the method of choice for diagnosing osteoporosis. Due to the limited access to DEXA-scanners, screening of patients with low energy fractures (LEF) for osteoporosis is not routinely performed in Denmark. Pre-screening with a simple, less expensive device might be able to exclude patients with normal bone mineral density (BMD) from further DEXA-scans. We aimed to determine the frequency of osteoporosis in patients with LEF, and evaluate the diagnostic impact of a radiographic absorptiometry (RA) scanner in the casualty department of a major Danish county hospital. In a 5-month period, 136 adult patients with LEF were invited for BMD measurements. In 74 (54%) patients DEXA-scans (spine and femoral neck) and phalangeal RA-scans were performed. A total of 86% of the patients were female and 39% were suffering from osteoporosis (T-scores < or = -2.5) according to the DEXA results. RA-BMD and T-scores differed significantly between the two groups, with and without osteoporosis (p < 0.001). Comparing T-scores from RA with the lowest T-scores from DEXA, a highly significant correlation was found for women (R = 0.7, p < 0.001). Using a RA cut-off value (T-score < -1) for women ensuring 100% sensitivity for identifying women with osteoporosis, the positive predictive value was 46%. Up to 19% of DEXA-scans could be avoided in this setting. In our population the simple RA-BMD-method was cost-effective as a pre-screening tool for osteoporosis in women. However, the final diagnosis still relies on results from DEXA-scans.