Improved labelling of DTPA- and DOTA-conjugated peptides and antibodies with 111In in HEPES and MES buffer.
Improved labelling of DTPA- and DOTA-conjugated peptides and antibodies with 111In in HEPES and MES buffer.
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DOI：
10.1186/2191-219x-2-4
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发表时间：
2012-01-27
期刊：
影响因子：
3.2
通讯作者：
Boerman OC
中科院分区：
文献类型：
--
作者：
Brom M;Joosten L;Oyen WJ;Gotthardt M;Boerman OC
在单光子发射计算机断层扫描[SPECT]中，111 In标记示踪剂的高比活度将允许给予少量示踪剂，以防止受体饱和和/或副作用。为了增加比活性，我们研究了标记过程中使用的缓冲液的影响：NaAc、NH 4Ac、HEPES和MES缓冲液。老化的111 InCl 3股票和镉污染的影响，111 In的衰变产物，也在这些缓冲区进行了检查。将递增量的111 InCl 3加入到1 μg二亚乙基三胺五乙酸[DTPA]-和1，4，7，10-四氮杂环十二烷-1，4，7，10-四乙酸[DOTA]-缀合的化合物（毒蜥外泌肽-3、奥曲肽和抗碳酸酐酶IX [CAIX]抗体）中。加入5体积的2-（N-吗啉代）乙磺酸[MES]、4-（2-羟乙基）-1-哌嗪乙磺酸[HEPES]、NH 4Ac或NaAc（0.1M，pH 5.5）。在20°C（DTPA缀合的化合物）、95°C（DOTA-毒蜥外泌肽-3和DOTA-奥曲肽）或45°C（DOTA-抗CAIX抗体）下20分钟后，通过即时薄层色谱法测定标记效率。老化的111 InCl 3股票上的DTPA-exendin-3的标记效率的效果，以及增加浓度的Cd 2+（111 In的衰变产物）的效果也进行了检查。在MES和HEPES缓冲液中，DTPA-奥曲肽和DOTA-抗CAIX抗体的比活性高5倍。DTPA-exendin-3、DOTA-exendin-3和DTPA-抗CAIX抗体在MES和HEPES缓冲液中的放射性标记导致比在NaAc和NH 4Ac中高两倍的比活性。在111 InCl 3生产日期后第11天，NaAc和NH 4Ac的DTPA-exendin-3标记分别下降了66%和73%，而MES和HEPES的比活性在第11天的最大下降分别为10%和4%。在NaAc和NH 4Ac中DTPA-毒蜥外泌肽-3的标记混合物中存在1 pM Cd 2+显著降低了标记效率，而在MES和HEPES缓冲液中Cd 2+浓度高达0.1 nM时不影响标记效率。我们显示了在HEPES和MES缓冲液中用111 In标记DTPA-和DOTA-缀合化合物的改进。增强的标记效率似乎是由于镉的竞争性螯合减少。增强的标记效率将允许用SPECT对生物标志物进行更灵敏的成像。
In single photon emission computed tomography [SPECT], high specific activity of 111In-labelled tracers will allow administration of low amounts of tracer to prevent receptor saturation and/or side effects. To increase the specific activity, we studied the effect of the buffer used during the labelling procedure: NaAc, NH4Ac, HEPES and MES buffer. The effect of the ageing of the 111InCl3 stock and cadmium contamination, the decay product of 111In, was also examined in these buffers. Escalating amounts of 111InCl3 were added to 1 μg of the diethylene triamine pentaacetic acid [DTPA]- and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid [DOTA]-conjugated compounds (exendin-3, octreotide and anti-carbonic anhydrase IX [CAIX] antibody). Five volumes of 2-(N-morpholino)ethanesulfonic acid [MES], 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid [HEPES], NH4Ac or NaAc (0.1 M, pH 5.5) were added. After 20 min at 20°C (DTPA-conjugated compounds), at 95°C (DOTA-exendin-3 and DOTA-octreotide) or at 45°C (DOTA-anti-CAIX antibody), the labelling efficiency was determined by instant thin layer chromatography. The effect of the ageing of the 111InCl3 stock on the labelling efficiency of DTPA-exendin-3 as well as the effect of increasing concentrations of Cd2+ (the decay product of 111In) were also examined. Specific activities obtained for DTPA-octreotide and DOTA-anti-CAIX antibody were five times higher in MES and HEPES buffer. Radiolabelling of DTPA-exendin-3, DOTA-exendin-3 and DTPA-anti-CAIX antibody in MES and HEPES buffer resulted in twofold higher specific activities than that in NaAc and NH4Ac. Labelling of DTPA-exendin-3 decreased with 66% and 73% for NaAc and NH4Ac, respectively, at day 11 after the production date of 111InCl3, while for MES and HEPES, the maximal decrease in the specific activity was 10% and 4% at day 11, respectively. The presence of 1 pM Cd2+ in the labelling mixture of DTPA-exendin-3 in NaAc and NH4Ac markedly reduced the labelling efficiency, whereas Cd2+ concentrations up to 0.1 nM did not affect the labelling efficiency in MES and HEPES buffer. We showed improved labelling of DTPA- and DOTA-conjugated compounds with 111In in HEPES and MES buffer. The enhanced labelling efficiency appears to be due to the reduced competitive chelation of cadmium. The enhanced labelling efficiency will allow more sensitive imaging of the biomarkers with SPECT.