Molecular design of polymer with lymphocyte-activating ability

我们发现含有苯基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存在于淋巴细胞质膜表面的糖残基结合所致。在此背景下，苯基硼酸酯聚合物作为人工淋巴细胞有丝分裂原。已知苯基硼酸在水环境中处于三角型和四面体型的平衡状态。只有四面体的硼酸盐与糖形成稳定的络合物。然而，由于苯基硼酸的pKa相对较高，在生理条件下(pH 7.4)只有少量的四面体硼酸盐存在。为了提高在生理条件下的有丝分裂活性，本研究在含硼聚合物中引入氨基，以促进硼酸盐与质膜上的糖残基形成络合物，从而增强淋巴细胞的增殖能力。合成了N，N-二甲基丙烯酰胺、3-丙烯酰胺基苯基硼酸和N，N-二甲氨基丙基丙烯酰胺三元共聚物(DBA)。用~3H-胸腺嘧啶核苷掺入法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~(3 H)-胸腺嘧啶核苷的摄取显著增加。这种有丝分裂能力的提高似乎是由于DBA中的氨基与苯基硼酸部分配位，从而有效地形成了细胞膜上的硼酸盐和糖残基之间的络合物。从淋巴细胞增殖的角度来看，DBA共聚物中存在一个最佳的氨基含量，这表明DBA的氨基含量在淋巴细胞增殖中起着至关重要的作用。

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.