RGD多肽修饰同种异体骨表面密度的放射性示踪研究

Calculation of the surface density of the RGD-containing peptide on allogenic bone using isotopic tracing technique

目的探讨应用^125I标记RGD多肽的放射性示踪方法测定RGD多肽在同种异体骨片表面的枝接密度的可行性。探寻RGD多肽反应浓度对表面密度的影响，获得RGD表面密度与反应浓度的关系曲线。方法用放射性^125I对人工合成的含RGD八肽（EPRGDNYR）进行标记反应，并测算比放射性。将标记后的省I-RGD作为放射性探针加入设计浓度分别为0．01mg／ml、0．10rag／ml、0．50mg／ml、1．00mg／ml、2．00mg／ml、4．00mg／ml的RGD反应液。以1-乙基-3-（3-二甲基氨丙基）碳二亚胺为交联剂，将预制的同种异体骨片置于不同设计浓度的RGD反应液中进行枝接反应。通过测定反应后的异体骨片的放射性和表面积，计算异体骨片表面RGD多肽的枝接密度，评价RGD多肽反应浓度对表面密度的影响并绘制二者的关系曲线。结果通过放射密度1-计数器的测定发现，^125I能够成功标记于RGD多肽。以含有^125I-RGD的不同设计浓度的RGD反应液与预制的同种异体骨片进行枝接反应后，发现同种异体骨片具有放射性，说明RGD多肽已经成功枝接于异体骨片。经分析发现RGD多肽的表面密度随反应浓度的增加而增加。结论RGD多肽的表面密度与其反应浓度间定量相关，随反应浓度的增长，表面密度逐渐趋于饱和值。

Objective To investigate the feasibility of determining the surface density of RGD-con- taining peptide on allogenie bone by isotopic tracing technique using RGD peptide labelled with 1~I, and the impact of the input concentration of RGD-containing peptide on the surface density, and to obtain the history between the surface density and the input concentration of RGD-eontaining peptide. Methods The syn- thetic RGD-containing peptide was labelled with 125I, and the specific radioactivity was calculated. The reac- tive solutions of RGD-containing peptide with the radioactive 125I-RGD as a probe were prepared at the input concentrations of 0.01 mg/ml, 0.10 mg/ml, 0.50 mg/ml, t.00 mg/ml, 2.00 mg/ml, 4.00 mg/ml. Using EDC as the cross-linking agent, the reaction was carried out by placing the allogenic bone pieces into the reactive solutions of RGD-containing peptide with different input concentrations. After the reaction, the surface den- sity of RGD-containing peptide grafted onto the allogenic bone pieces was calculated by evaluating the ra- dioactivity and the surface area of the bone pieces. The impact of the input concentration of RGD-containing peptide on the surface density was measured and the curve was ascertained. Results After measuring in the radiodensity ~/-counter, the result showed the RGD peptides have been marked with t25I successfully. The al- logenic bone pieces were radioactive after the reaction, which demonstrated that the RGD-containing peptide had been grafted onto the surface of bone pieces successfully. It was also found that with the increasing of input concentration, the surface density raised. Conclusion The surface density of RGD-containing peptide is related to its input concentration. With the increasing of input concentration, the surface density raises to the saturation value gradually.