Chemical properties
La-135 is a radio-lanthanide, which is valued as a medical radionuclide for targeted Auger electron therapy and SPECT imaging. In aqueous solutions it exists in trivalent state. La3+ can be chelated e.g. with DTPA or DOTA. The ionic radius of La3+ is 103 pm, i.e. the largest among the lanthanides and close to that of Ac3+ which is 112 pm. It might thus serve as close surrogate for Ac-225 labelling studies.
Nuclear properties
La-135 decays by electron capture decay with a half-life of 18.9 hours REF to stable Ba-135. It has also a tiny β+ decay branch with positron emission of only 0.007%.
La-135 emits X-rays, notably Kα at ≈32 keV (61.3(10)%) and Kβ at ≈37 keV (13.4(19) %). These energies make La-135 suitable for SPECT imaging with low-energy detectors. La-135 emits only few γ-rays, namely at 480.5 keV (1.52%).
The mean photon energy per decay is 35 keV and the mean electron energy emitted per decay is 5 keV REF. Most electrons are short-range Auger electrons with <0.6 µm and <13 µm respectively REF. La-135 has therefore been proposed as therapeutic Auger electron emitter.
Production
La-135 is produced by proton irradiation of enriched Ba-135 carbonate targets via the ¹³⁵Ba(p,n)¹³⁵La reaction at Hevesy Laboratory (DTU) and Institute of Radiopharmaceutical Cancer Research (HZDR). After decay of short-lived co-produced activities, a La/Ba separation is performed by multi-step ion exchange or extraction chromatography.
Distribution
Activity will be shipped from Hevesy Laboratory (DTU, Risø, Denmark) and Institute of Radiopharmaceutical Cancer Research (HZDR, Dresden, Germany) to the users in form of La3+ solution.
Examples of use
| Parameter | Specifications |
|---|---|
| Production route | Ba-135(p,n)La-135 or Ba-136(p,2n)La-135 |
| Daughter | Decays to stable Ba-135: 99.993% EC, 0.007% β+ |
| Half-life | 18.9 h |
| Processing | Precipitation and extraction chromatography or multi-step ion exchange chromatography |
| Primary Container | 2.5 mL borosilicate glass V-vial with silicon rubber screw cap / plastic vial |
| Product Grade | n.c.a. |
| Physical Form | Liquid |
| Chemical Form | La3+ ion in 0.1 M HCl solution (1-2 ml) |
| Radioactive Concentration (gamma spectrometry) | n.a. |
| Appearance | Clear colourless solution |
| Radionuclide identification (gamma spectrometry) | 481 keV and 875 keV gamma lines present |
| Radionuclidic Purity (gamma spectrometry) | >99% |
| Chemical purity (ICP-OES) | Metal impurities determined by ICP-OES for each batch. Typical 25 nmol Al, 5 nmol Ba, 1-2 nmol Fe, Zn per batch (subject to revision) |
| Molar activity (ICP-OES) | Typical 1000 GBq/µmol La at End Of Chemistry (>15% of theoretical maximum) |
| Apparent Molar Activity | >50 GBq/μmol with macropa |
| Microbiological quality | Bioburden and endotoxin burden can be analysed post release, upon request. |
| Bacterial endotoxin | Bioburden and endotoxin burden can be analysed post release, upon request. |
| pH (pH strips) | 1 |
| Additional information | |
| Activity available | < 1 GBq upon request |
| Activity limit for UN2910 (excepted package) shipment | 20 MBq in dry state or 2 MBq in liquid form |
| Other information | - |
