Marx Kenneth A, Zhou Tiean, Long Dang
Center for Intelligent Biomaterials,Department of Chemistry, University of Massachusetts, Lowell, Massachusetts 01854, USA.
Biomacromolecules. 2005 May-Jun;6(3):1698-706. doi: 10.1021/bm049189n.
Using the electrochemical quartz crystal microbalance (EQCM), we compared thin films formed on Pt by electropolymerization of l-tyrosine to that of the amphiphilic monomers, decyl esters of d- and l-tyrosine (DEDT and DELT). Mass build-up and film properties were determined as a function of monomer concentration via frequency, f, motional resistance, R, and charge passage, Q, measurements. Films were found to occur by a combination of monomer electropolymerization and adsorption for DEDT and DELT, but only by electropolymerization for l-tyrosine. This difference in film formation process for the monomers is reflected in the net mass build-up for each film, as represented by calculated df/dQ values. For the adsorbing monomers DEDT and DELT, films possessed concentration dependent df/dQ values, more than 100-fold greater than that for l-tyrosine film formation under equivalent electropolymerization conditions. During the entire film growth process, all three films exhibited no significant energy dissipation properties (DeltaR invariant). Concentration dependent adsorption of significant levels of unpolymerized but self-assembled DEDT and DELT monomers account for the subsequent time dependent mass loss observed from the films maintained in buffer in the absence of monomer. Contact angle measurements demonstrated a pH dependent increase in the surface hydrophilicity of films electropolymerized from the DEDT, DELT, and l-tyrosine monomers but not films formed from phenol and 3-nitrophenol monomers. This behavior is consistent with the monomers' known changes in titration/charge state properties with increasing pH. This study provided insight into the film formation, stability, and surface hydrophilicity resulting from electropolymerization of these related tyrosine based monomers. This information is critical to assessing the utility these films may have in the development of new biomaterials and as biological macromolecule or cell immobilization strategies in biosensors.
我们使用电化学石英晶体微天平（EQCM），将通过L-酪氨酸电聚合在铂上形成的薄膜与两亲性单体D-酪氨酸和L-酪氨酸的癸酯（DEDT和DELT）形成的薄膜进行了比较。通过频率f、运动电阻R和电荷通过量Q的测量，确定了质量积累和薄膜性质与单体浓度的函数关系。发现DEDT和DELT的薄膜是通过单体电聚合和吸附的组合形成的，而L-酪氨酸的薄膜仅通过电聚合形成。单体成膜过程的这种差异反映在各薄膜的净质量积累上，以计算出的df/dQ值表示。对于吸附性单体DEDT和DELT，薄膜具有浓度依赖性的df/dQ值，比在等效电聚合条件下L-酪氨酸成膜的df/dQ值大100多倍。在整个薄膜生长过程中，所有三种薄膜均未表现出明显的能量耗散特性（ΔR不变）。大量未聚合但自组装的DEDT和DELT单体的浓度依赖性吸附，解释了在没有单体的情况下，保持在缓冲液中的薄膜随后出现的随时间的质量损失。接触角测量表明，由DEDT、DELT和L-酪氨酸单体电聚合形成的薄膜的表面亲水性随pH值增加，而由苯酚和3-硝基苯酚单体形成的薄膜则不然。这种行为与单体已知的随着pH值增加滴定/电荷状态性质的变化一致。本研究深入了解了这些相关酪氨酸基单体电聚合产生的成膜、稳定性和表面亲水性。这些信息对于评估这些薄膜在新型生物材料开发以及作为生物传感器中生物大分子或细胞固定策略方面的实用性至关重要。
