Department of Pediatrics, Children's Hospital of Michigan, Wayne State University, Detroit, MI 48201, United States.
Int J Pharm. 2010 Aug 16;395(1-2):298-308. doi: 10.1016/j.ijpharm.2010.05.030. Epub 2010 May 24.
Dendrimers have emerged as topical microbicides to treat vaginal infections. This study explores the in vitro, in vivo antimicrobial activity of PAMAM dendrimers, and the associated mechanism. Interestingly, topical cervical application of 500 microg of generation-4 neutral dendrimer (G(4)-PAMAM-OH) showed potential to treat the Escherichia coli induced ascending uterine infection in guinea pig model of chorioamnionitis. Amniotic fluid collected from different gestational sacs of infected guinea pigs posttreatment showed absence of E. coli growth in the cultures plated with it. The cytokine level [tumor necrosis factor (TNFalpha) and interleukin (IL-6 and IL-1beta)] in placenta of the G(4)-PAMAM-OH treated animals were comparable to those in healthy animals while these were notably high in infected animals. Since, antibacterial activity of amine-terminated PAMAM dendrimers is known, the activity of hydroxyl and carboxylic acid terminated PAMAM dendrimers was compared with it. Though the G(4)-PAMAM-NH(2) shows superior antibacterial activity, it was found to be cytotoxic to human cervical epithelial cell line above 10 microg/mL, while the G(4)-PAMAM-OH was non-cytotoxic up to 1mg/mL concentration. Cell integrity, outer (OM) and inner (IM) membrane permeabilization assays showed that G(4)-PAMAM-OH dendrimer efficiently changed the OM permeability, while G(4)-PAMAM-NH(2) and G(3.5)-PAMAM-COOH damaged both OM and IM causing the bacterial lysis. The possible antibacterial mechanism are G(4)-PAMAM-NH(2) acts as polycation binding to the polyanionic lipopolysaccharide in E. coli, the G(4)-PAMAM-OH forms hydrogen bonds with the hydrophilic O-antigens in E. coli membrane and the G(3.5)-PAMAM-COOH acts as a polyanion, chelating the divalent ions in outer cell membrane of E. coli. This is the first study which shows that G(4)-PAMAM-OH dendrimer acts as an antibacterial agent.
树状聚合物已成为治疗阴道感染的局部杀菌剂。本研究探索了 PAMAM 树状聚合物的体外、体内抗菌活性及其相关机制。有趣的是，局部宫颈应用 500μg 第四代中性树状聚合物（G(4)-PAMAM-OH）可有效治疗豚鼠绒毛膜羊膜炎模型中大肠杆菌引起的上行性子宫感染。治疗后从感染豚鼠的不同妊娠囊收集的羊水在接种时未显示大肠杆菌生长。用 G(4)-PAMAM-OH 处理的动物胎盘的细胞因子水平[肿瘤坏死因子（TNFalpha）和白细胞介素（IL-6 和 IL-1beta）]与健康动物相当，而在感染动物中则明显升高。由于胺端 PAMAM 树状聚合物具有抗菌活性，因此比较了羟基和羧酸端 PAMAM 树状聚合物的活性。尽管 G(4)-PAMAM-NH(2)显示出优越的抗菌活性，但发现其对人宫颈上皮细胞系的细胞毒性超过 10μg/ml，而 G(4)-PAMAM-OH 在 1mg/ml 浓度下是非细胞毒性的。细胞完整性、外膜（OM）和内膜（IM）通透性测定表明，G(4)-PAMAM-OH 树状聚合物可有效改变 OM 通透性，而 G(4)-PAMAM-NH(2)和 G(3.5)-PAMAM-COOH 则破坏 OM 和 IM，导致细菌裂解。可能的抗菌机制是 G(4)-PAMAM-NH(2)作为聚阳离子与大肠杆菌中的聚阴离子脂多糖结合，G(4)-PAMAM-OH 与大肠杆菌膜中的亲水性 O-抗原形成氢键，G(3.5)-PAMAM-COOH 作为聚阴离子，螯合大肠杆菌外细胞膜中的二价离子。这是第一项表明 G(4)-PAMAM-OH 树状聚合物作为抗菌剂发挥作用的研究。
