Razatos A, Ong Y L, Sharma M M, Georgiou G
Department of Chemical Engineering, University of Texas, Austin 78712, USA.
J Biomater Sci Polym Ed. 1998;9(12):1361-73. doi: 10.1163/156856298x00442.
Bacterial infection of biomaterials represents one of the most important reasons for the failure of transdermal or implanted medical devices. The first and least understood step in biomaterial-associated infections is the initial interaction between bacteria and a surface. This initial interaction can be either attractive or repulsive depending on the physiochemical nature of the biological and synthetic surfaces, as well as the properties of the interstitial fluid. We have shown that atomic force microscopy (AFM) can be employed as an exquisitely sensitive and versatile tool for quantifying the interaction between bacteria and surfaces in physiological solutions. The forces of interaction between an AFM cantilever tip and a uniform lawn of bacteria immobilized on glass were determined. By comparing the interactions of cantilever tips with lawns of isogenic E. coli strains carrying genetic lesions that alter their cell surface composition, it was possible to evaluate the effect of macromolecules such as lipopolysaccharide and capsular polysaccharide on the adhesion process. Mutations that result in the synthesis of truncated lipopolysaccharide or in the overproduction of the negatively charged capsular polysaccharide colanic acid render the interaction of the bacteria with the AFM tip unfavorable due to increased electrostatic repulsion. Furthermore, AFM could be used to evaluate the adhesion of bacteria onto commercially relevant biomaterials. In one approach, micron-size polystyrene beads were attached to AFM tips which were then used to measure forces. Unfortunately, this approach is limited by the meager number of materials manufactured as beads of a size suitable for AFM measurements. As an alternative approach, AFM cantilever tips were coated with a confluent layer of bacteria and used to probe planar surfaces. In this configuration, AFM could be employed to measure the force of interaction between virtually any bacterium and surface of interest.
生物材料的细菌感染是经皮或植入式医疗设备失效的最重要原因之一。生物材料相关感染的第一步也是最不为人所理解的一步，是细菌与表面之间的初始相互作用。这种初始相互作用可能是吸引性的，也可能是排斥性的，这取决于生物和合成表面的物理化学性质以及组织液的特性。我们已经表明，原子力显微镜（AFM）可以用作一种极其灵敏且通用的工具，用于量化生理溶液中细菌与表面之间的相互作用。测定了AFM悬臂尖端与固定在玻璃上的均匀细菌菌苔之间的相互作用力。通过比较悬臂尖端与携带改变其细胞表面组成的遗传损伤基因的同基因大肠杆菌菌株菌苔之间的相互作用，可以评估诸如脂多糖和荚膜多糖等大分子对粘附过程的影响。导致截短脂多糖合成或带负电荷的荚膜多糖柯氏酸过量产生的突变，由于静电排斥增加，使得细菌与AFM尖端的相互作用变得不利。此外，AFM可用于评估细菌在商业相关生物材料上粘附情况。在一种方法中，将微米级聚苯乙烯珠附着到AFM尖端，然后用于测量力。不幸的是，这种方法受到制造适合AFM测量尺寸珠子的材料数量稀少的限制。作为一种替代方法，AFM悬臂尖端涂覆有一层融合的细菌层，并用于探测平面表面。在这种配置下，AFM可用于测量几乎任何细菌与感兴趣表面之间的相互作用力。
