双亲性无规光敏共聚物的疏水基元对其自组装胶束乳化性能的影响

设计合成了一系列具有不同化学组成的双亲性无规光敏共聚物,聚(7-对乙烯基苄氧基-4-甲基香豆素-r-丙烯酸)(P(VM-r-AA)),通过选择性溶剂法自组装获得纳米胶束,并将纳米胶束用作大分子颗粒乳化剂,研究其在甲苯-水界面的稳定性能。研究表明:聚合物疏水基元含量的增加使自组装胶束结构由溶胀的微凝胶状向刚性颗粒状转变;同时,胶束初始乳化效率增加,但油水界面吸附稳定性显著下降。此外,通过对疏水基元PVM的摩尔分数为12%的胶束进行辐照交联,并研究其在不同pH下的乳化性能,结果表明:胶束表面溶胀的双亲性链段对其乳化性能产生了重要的影响。未交联的胶束保持着良好的乳化性能;而交联的胶束形变能力变差、刚性增强,在碱性条件下,彻底失去乳化能力。     

Acrylic acid copolymer nanoparticles for drug delivery. Part II: Characterization of nanoparticles surface-modified by adsorption of ethoxylated surfactants

Copolymer nanoparticles of acrylic acid, acrylic amide, acrylic butylester, and methacrylic methylester with increasing content of acrylic acid were produced and surface-modified by adsorption of nonionic (Poloxamer 407, Poloxamine 908, Antarox CO 990) and ionic (Gafac RE 960) surfactants. The coated particles were characterized with regard to parameters relevant for the in vivo organ distribution: coating layer thickness, charge-reducing effect of the coating layer and surface hydrophobicity. Gafac was found to form highly charged surface layers leading to recognition by the reticuloendothelial system (RES). The hydrophobicity of the coating layers decreased with increasing thickness. The thickest coating layers were found on the most hydrophobic particles possessing least content of acrylic acid (1.9%). These particles coated with the nonionics were regarded as sufficiently hydrophilic to potentially reduce the uptake by the RES in vivo. The properties of coating layers can therefore be optimized by variation of the monomer ratios in copolymers.     

Copper(II) complexes of methylated glycine derivatives: Effect of methyl substituent on their DNA binding and nucleolytic property

A set of copper(II) complexes of glycine and methylated glycine derivatives, Cu(aa)₂, consisting of C-dimethylglycine, l-alanine, N-dimethylglycine and sarcosine, was investigated for their DNA binding and nucleolytic properties by means of EPR and visible spectroscopy, and electrophoresis. They bind weakly to DNA with apparent binding constants in the range 1.8–2.9 × 10³ M⁻¹ with very similar orientation. No DNA cleavage is observed in the absence of exogenous agents. Copper(II) complexes of N-methylated derivatives bind to DNA more stereo-specifically and less strongly, and their oxidative DNA cleavage is less efficient than those of the corresponding C-methylated derivatives in the presence of hydrogen peroxide (H₂O₂) alone, or sodium ascorbate (NaHA) alone or tandem H₂O₂–NaHA. The oxidative DNA cleavage mechanism in the three systems involves a common copper(I) species. Neocuproine can inhibit DNA cleavage by these complexes.