Wu Xi, Wei Pei-Hsun, Zhu Xiao, Wirth Mary J, Bhunia Arun, Narsimhan Ganesan
Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, IN 47907, United States.
Department of Chemistry, Purdue University, West Lafayette, IN 47907, United States.
Colloids Surf B Biointerfaces. 2017 Aug 1;156:305-312. doi: 10.1016/j.colsurfb.2017.05.047. Epub 2017 May 17.
Antimicrobial peptides (AMPs) have the ability to penetrate the cell membrane, form pores which eventually lead to cell death. Immobilization of AMP on nanoparticles can play a major role in antimicrobial materials, biosensors for pathogen detection and in food safety. The minimum inhibitory concentration (MIC) of free Cecropin P1 (CP1, sequence SWLSTAKKLENSAKKRLSEGIAIAIQGGPR) and adsorbed on silica nanoparticle against E. coli O157:H7 EDL933 were 0.78μg/ml. This was found to be consistent with preservation of α-helical secondary structure of CP1 upon adsorption as indicated by circular dichroism (CD). Cysteine-terminus modified Cecropin P1 (CP1C, sequence SWLSTAKKLENSAKKRLSEGIAIAIQGGPRC) was chemically immobilized onto silica nanoparticles with maleimide-PEG-NHS ester cross-linkers of different PEG chain lengths. The antimicrobial activity of CP1C in solution and adsorbed on silica nanoparticles against E. coli O157:H7 EDL933 were found to be the same as those for CP1. However, tethered CP1C exhibited much higher MIC of 24.38, 37.55 and 109.82μg/ml for (PEG), (PEG) and (PEG) linkers respectively. The antimicrobial activity of CP1C tethered to silica nanoparticles with (PEG) linker was found to be lower for lower surface coverage with MIC values being 86.06, 36.89, 24.38 and 17.84μg/ml for surface coverage of 12.3%, 24.4%, 52.8% and 83.8% respectively. All atom MD simulation of 1:3 DOPG/DOPC mixed membrane interacting with free and PEGlyated CP1C indicated that presence of PEG linker prevented CP1C from interacting with the bilayer which may explain the loss of antimicrobial activity of tethered CP1C.
抗菌肽（AMPs）能够穿透细胞膜，形成最终导致细胞死亡的孔。将抗菌肽固定在纳米颗粒上在抗菌材料、用于病原体检测的生物传感器以及食品安全方面可发挥重要作用。游离的天蚕素P1（CP1，序列为SWLSTAKKLENSAKKRLSEGIAIAIQGGPR）及其吸附在二氧化硅纳米颗粒上的形式对大肠杆菌O157:H7 EDL933的最低抑菌浓度（MIC）均为0.78μg/ml。圆二色性（CD）表明，这与CP1吸附后α-螺旋二级结构的保留一致。用不同聚乙二醇（PEG）链长的马来酰亚胺-PEG-活性酯交联剂将半胱氨酸末端修饰的天蚕素P1（CP1C，序列为SWLSTAKKLENSAKKRLSEGIAIAIQGGPRC）化学固定在二氧化硅纳米颗粒上。发现溶液中的CP1C及其吸附在二氧化硅纳米颗粒上时对大肠杆菌O157:H7 EDL933的抗菌活性与CP1相同。然而，连接的CP1C对（PEG）、（PEG）和（PEG）连接剂的最低抑菌浓度分别高达24.38、37.55和109.82μg/ml。对于表面覆盖率较低的情况，发现用（PEG）连接剂连接到二氧化硅纳米颗粒上的CP1C的抗菌活性较低，表面覆盖率为12.3%、24.4%、52.8%和83.8%时，最低抑菌浓度分别为86.06、36.89、24.38和17.84μg/ml。对1:3的二油酰磷脂酰甘油/二油酰磷脂酰胆碱（DOPG/DOPC）混合膜与游离和聚乙二醇化CP1C相互作用的全原子分子动力学（MD）模拟表明，PEG连接剂的存在阻止了CP1C与双层膜相互作用，这可能解释了连接的CP1C抗菌活性丧失的原因。
