Molecular design of polymer with lymphocyte-activating ability

我们已经发现，具有苯硼酸部分的水溶性聚合物具有诱导小鼠淋巴细胞增殖的能力。这可能是由于聚合物中的苯基硼酸残基与淋巴细胞质膜表面存在的糖残基结合所致。在这种情况下，苯基硼酸酯聚合物充当淋巴细胞的人工有丝分裂原。已知苯基硼酸在水环境中具有三角形和四面体硼酸盐形式之间的平衡。只有四面体硼酸盐与糖形成稳定的复合物。然而，由于苯基硼酸的相对较高的pKa，在生理条件下（pH 7.4）仅存在少量的四面体硼酸盐。为了增加在生理条件下的促有丝分裂活性，在本研究中将氨基引入含硼酸盐的聚合物中以促进硼酸盐与质膜上的糖残基形成复合物，从而实现增加的淋巴细胞增殖能力。合成了N，N-二甲基丙烯酰胺、3-丙烯酰胺基苯硼酸和N，N-二甲基氨丙基丙烯酰胺三元共聚物（DBA）。通过掺入^3H-胸苷来评价小鼠淋巴细胞的增殖反应。与不含氨基的DB相比，DBA培养的淋巴细胞对^3H-胸苷的摄取显著增加。这种促有丝分裂能力的增加似乎是由于硼酸酯和糖残基之间的复合物的有效形成，因为氨基的协调苯基硼酸部分在DBA.有观察到一个最佳的氨基含量在DBA共聚物中的淋巴细胞增殖方面，表明DBA的氨基含量在淋巴细胞增殖中的至关重要的作用。

We have found that water soluble polymer having phenylboronic acid moiety has ability to induce mouse lymphocytes proliferation. This might be due to the binding of phenylboronic acid residues in the polymer to sugar residues existing on the plasma membrane surface of lymphocytes. In this context, phenylboronate polymer serves as artificial mitogen of lymphocytes. phenylboronic acid is known to have an equilibrium between trigonal form and tetrahedral borate form in aqueous milieu. Only tetrahedral borate forms a stable complex with sugar. However, due to the relatively high pKa of phenylboronic acid, there exists only a small amount of tetrahedral boronate at physiological condition (pH7.4). To increase mitogenic activity under physiological condition, amino groups were introduced into the borate-containing polymer in this study to facilitate complex formation of boronate with sugar residues on the plasma membrane, allowing to achieve an increased ability to proliferate lymphocytes. Thus, ternary copolymer (DBA) of N,N-dimethylacrylamide, 3-acrylamidophenylboronic acid and N,N-dimethylaminopropylacrylamide (DMAPAA) was synthesized. Proliferative response of mouse lymphocytes was evaluated from incorporation of ^3H-thymidine. Remarkable increase in ^3H-thymidine uptake to lymphocytes was observed for lymphocytes cultured with DBA compared to that with DB which has no amino groups. This increase in mitogenic ability seems to be due to the effective formation of the complex between boronate and sugar residues on the cell membrane because of the coordination of amino groups to phenylboronic acid moieties in DBA.There was observed an optimum amino group content in the DBA copolymer in terms of lymphocyte proliferation, indicating a crucial role of amino group content of DBA in lymphocyte proliferation.