@article {1416,
	title = {Antimicrobial surfaces containing cationic nanoparticles: how immobilized, clustered, and protruding cationic charge presentation affects killing activity and kinetics.},
	journal = {Colloids Surf B Biointerfaces},
	volume = {125},
	year = {2015},
	month = {2015 Jan 1},
	pages = {255-63},
	abstract = {<p>This work examines how the antimicrobial (killing) activity of net-negative surfaces depends on the presentation of antimicrobial cationic functionality: distributed versus clustered, and flat clusters versus raised clusters. Specifically, the ability to kill Staphylococcus aureus by sparsely distributed 10 nm cationic nanoparticles, immobilized on a negative surface and backfilled with a PEG (polyethylene glycol) brush, was compared with that for a dense layer of the same immobilized nanoparticles. Additionally, sparsely distributed 10 nm poly-L-lysine (PLL) coils, adsorbed to a surface to produce flat cationic \&quot;patches\&quot; and backfilled with a PEG brush were compared to a saturated adsorbed layer of PLL. The latter resembled classical uniformly cationic antimicrobial surfaces. The protrusion of the cationic clusters substantially influenced killing but the surface concentration of the clusters had minor impact, as long as bacteria adhered. When surfaces were functionalized at the minimum nanoparticle and patch densities needed for bacterial adhesion, killing activity was substantial within 30 min and nearly complete within 2 h. Essentially identical killing was observed on more densely functionalized surfaces. Surfaces containing protruding (by about 8 nm) nanoparticles accomplished rapid killing (at 30 min) compared with surfaces containing similarly cationic but flat features (PLL patches). Importantly, the overall surface density of cationic functionality within the clusters was lower than reported thresholds for antimicrobial action. Also surprising, the nanoparticles were far more deadly when surface-immobilized compared with free in solution. These findings support a killing mechanism involving interfacial stress.</p>
},
	issn = {1873-4367},
	doi = {10.1016/j.colsurfb.2014.10.043},
	author = {Fang, Bing and Jiang, Ying and N{\"u}sslein, Klaus and Rotello, Vincent M and Santore, Maria M}
}
@article {1418,
	title = {Easy come easy go: surfaces containing immobilized nanoparticles or isolated polycation chains facilitate removal of captured Staphylococcus aureus by retarding bacterial bond maturation.},
	journal = {ACS Nano},
	volume = {8},
	year = {2014},
	month = {2014 Feb 25},
	pages = {1180-90},
	abstract = {<p>Adhesion of bacteria is a key step in the functioning of antimicrobial surfaces or certain types of on-line sensors. The subsequent removal of these bacteria, within a \&sim; 10-30 min time frame, is equally important but complicated by the tendency of bacterial adhesion to strengthen within minutes of initial capture. This study uses Staphylococcus aureus as a model bacterium to demonstrate the general strategy of clustering adhesive surface functionality (at length scales smaller than the bacteria themselves) on otherwise nonadhesive surfaces to capture and retain bacteria (easy come) while limiting the progressive strengthening of adhesion. The loose attachment facilitates bacteria removal by moderate shearing flow (easy go). This strategy is demonstrated using surfaces containing sparsely and randomly arranged immobilized amine-functionalized nanoparticles or poly-l-lysine chains, about 10 nm in size. The rest of the surface is backfilled with a nonadhesive polyethylene glycol (PEG) brush that, by itself, repels S. aureus. The nanoparticles or polymer chains cluster cationic functionality, providing small regions that attract negatively charged S. aureus cells. Compared with surfaces of nearly uniform cationic character where S. aureus adhesion quickly becomes strong (on a time scale less than 5 min), placement of cationic charge in small clusters retards or prevents processes that increase bacteria adhesion on a time scale of \&sim; 30 min, providing \&quot;easy go\&quot; surfaces.</p>
},
	keywords = {Nanoparticles, Polyamines, Staphylococcus aureus, Surface Properties},
	issn = {1936-086X},
	doi = {10.1021/nn405845y},
	author = {Fang, Bing and Jiang, Ying and Rotello, Vincent M and N{\"u}sslein, Klaus and Santore, Maria M}
}
