Luminescent Polyelectrolytes for use in Biosensors

发光聚电解质具有很大的Stern-Volmer猝灭常数，表现出增强的荧光猝灭(“超猝灭”)。超猝灭是两种效应共同作用的结果。首先，已经证明了单一受体(作为光诱导电子转移的受体)可以猝灭整个大分子在水溶液中的荧光发射。第二，在水溶液中，这种发光聚电解质带电。结果，带正电荷的受体和阴离子聚合物形成弱结合络合物，从而使静态超猝灭成为可能。光致发光的超猝灭可用于生物分子的检测，具有较高的灵敏度和特异性。因此，测定和控制聚合物/猝灭剂络合物的库仑结合能的大小对于发光聚电解质在生物传感器中的应用尤为重要。如果连接到猝灭剂的配体和分析物之间的结合小于猝灭剂和聚合物之间的结合，则不能有效地将猝灭剂/配体从发光聚合物中拉出。此外，聚合物的光致发光(PL)量子效率对聚合物在溶液中的构象很敏感。众所周知，聚电解质可以与带相反电荷的两亲分子(表面活性剂)形成稳定的络合物。实验表明，在含有发光聚电解质的溶液中加入表面活性剂可以显著提高发光效率。因此，研究发光聚电解质的链构象具有明显的科学意义和重要意义。%本项目旨在确定发光聚电解液的链构象和聚合物的库仑结合能的大小：猝灭剂络合物。要研究的发光聚电解质包括水溶性PPV衍生物和新型多赖氨酸聚合物(以J-聚集型菁染料为侧链的多肽链)。已开发出一系列不同装药量的淬火剂，并可用于这些研究。通过改变缓冲水溶液中的离子浓度、改变受体的浓度和改变温度来研究PL的猝灭。发光聚电解质的链构象将通过光散射和中子散射作为德拜屏蔽长度(离子浓度)的函数和分子量的函数来确定(有或没有猝灭剂、表面活性剂等)。

Luminescent polyelectrolytes exhibit enhanced fluorescence quenching ("superquenching") with very large Stern-Volmer quenching constants. The superquenching arises from a combination of two effects. First, it has been demonstrated that a single acceptor (functioning as an acceptor for photoinduced electron transfer) can quench the fluorescence emission from an entire macromolecule in aqueous solution. Second, in aqueous solution, such luminescent polyelectrolytes are charged. As a result, the positively charged acceptor and the anionic polymer form a weakly bound complex thereby enabling static superquenching. The superquenching of the photoluminescence (PL) can be used for sensing biomolecules with specificity and with high sensitivity. Thus, determining and controlling the magnitude of the Coulomb binding energy of the polymer/quencher complex is of particular importance to the use of luminescent polyelectrolytes in biosensor applications. If the binding between the ligand tethered to the quencher and the analyte is smaller than that between the quencher and the polymer, the quencher/ligand cannot be effectively pulled away from the luminescent polymer. In addition, the photoluminescence (PL) quantum efficiency is sensitive to the conformation of the polymer in solution. It is known that polyelectrolytes can form stable complexes with oppositely charged amphiphilc molecules (surfactants). Experiments have shown that addition of sufactant to solutions containing luminescent polyelectrolytes significantly increases the PL efficiency. Thus, studies of the chain conformation of luminescent polyelectrolytes is of clear scientific relevance and importance.%%% This project is directed toward determining the chain conformation of luminescent polyelectrolytes and the magnitude of the Coulomb binding energy of the polymer: quencher complexes. The luminescent polyelectrolytes to be studied include water soluble PPV derivatives and novel poly-lysine polymers (polypeptide chains with cyanine dyes in J-aggregate configuration attached as side-chains). A series of quenchers with different charges have been developed and are available for these studies. Quenching of PL will be studied by changing the ion concentration in buffered aqueous solutions, by changing the concentration of acceptors, and by varying the temperature. The chain conformation of the luminescent polyelectrolytes will be determined (with and without quencher, surfactant etc), as a function of the Debye screening length (ion concentration) and as a function of molecular weight using light scattering and neutron scattering.