Effect of plasma coating on antibacterial activity of silver nanoparticles

Sil­ver nanopar­ti­cles (NPs) are known to pro­vide an­timi­cro­bial prop­er­ties for sur­faces. How­ever, there are en­vi­ron­men­tal con­cerns due to re­ports of tox­i­c­ity af­ter ex­po­sure to the en­vi­ron­ment dur­ing or af­ter end-use. Im­mo­bi­liz­ing sil­ver NPs to the sur­face of sub­strates could en­sure that par­ti­cles are read­ily avail­able for an­tibac­te­r­ial ac­tiv­ity with lim­ited en­vi­ron­men­tal ex­po­sure. A plasma coat­ing on top of sil­ver NPs could im­prove the ad­he­sion of NPs to a sub­strate, but it could also im­pede the re­lease of sil­ver NPs com­pletely. Fur­ther­more, sil­ver has been shown to re­quire di­rect con­tact to demon­strate an­tibac­te­r­ial ac­tiv­ity. This study demon­strates im­mo­bi­liza­tion of sil­ver NPs with plasma coat­ing onto a sur­face while main­tain­ing its an­tibac­te­r­ial prop­er­ties. Sil­ver NPs are si­mul­ta­ne­ously syn­the­sized and de­posited onto a sur­face with liq­uid flame spray aerosol tech­nique fol­lowed by hexa­m­ethyl­d­is­ilox­ane plasma coat­ing to im­mo­bi­lize the NPs. Atomic force mi­cro­scope scratch test­ing is used to demon­strate im­proved nanopar­ti­cle ad­he­sion. An­tibac­te­r­ial ac­tiv­ity against gram-neg­a­tive Es­cherichia coli is main­tained even for plasma coat­ing thick­nesses of 195 nm. NP ad­he­sion to the sur­face is sig­nif­i­cantly im­proved. Gram-pos­i­tive Staphy­lo­coc­cus au­reus was found be re­sis­tant to all the plasma-coated sam­ples. The re­sults show promise of us­ing plasma coat­ing tech­nol­ogy for lim­it­ing NP ex­po­sure to en­vi­ron­ment.