In this paper a label-free fluorescent sensor for probing the interaction between heparin and protein was reported.Heparin,the bioactive polyanions,formed supramolecular assemblies with cationic surfactant cetyltrimethyl ammonium bromide (CTAB).The environment-dependent dye pyrene,encapsulated in hydrophobic interiors of the supramolecular assemblies worked as the fluorescence probe.Once the heparin-binding protein was added,competing interactions of protein with heparin would weaken the interaction between CTAB and heparin.As a result,the noncovalently sequestered pyrene would be released upon disassembly and the fluorescence of the released pyrene was subsequently decreased.The binding events were exemplified by protamine and Tat peptide,these processes were also verified by DLS and TEM.Such a strategy is appealing as organic synthesis was traded off against supramolecular assembly.This label-free fluorescent system is simple,selective,convenient,and can serve as a good complement to other existing methods,also this method has the potential for preprimary drug screening.
Based on the noncovalent functionalization of ferrocene-grafted polyethylenimine （PEI-Fc） and carbon nanotubes （CNTs）, CNT bundles are exfoliated by PEI-Fc solution and thus form stable compounds PEI-Fc@CNTs, which is used to construct the PEI-Fc@CNTs/DNA multilayers through layer-by-layer assembly. The multilayers show a highly uniform and homogeneous characteristic, which significantly improve the electrical property of the multilayers. Upon the oxidation electrical potential, the ferrocene groups are switched from reduction state （[Fe（C5H5）2]） to oxidation state （[Fe（C5H5）2]^＋）, leading to change of microenvironments＇ charge density, resulting in swelling of the multilayers and a final degree of swelling of 37 % and the decrease of multilayer stiffness. We maintain that electrochemical control over the swelling behavior of multilayers could have important implications for responsive coatings of nanoscale devices, including mechanically tunable surfaces which are used to modulate cellular activities and control drug delivery.
