In situ synthesis of silver nanoparticles on the surface of PDMS with high antibacterial activity and biosafety toward an implantable medical device

Abstract

We developed a straightforward method to fabricate antibacterial silicon films via the in situ synthesis of silver nanoparticles (AgNPs) on a polydimethylsiloxane (PDMS) film. To grow AgNPs attached on the film, AgNP seeds were synthesized through the reduction of silver ions electrostatically bound to hydroxyl groups formed on the surface of the film after treatment with air plasma. In the growth reaction, silver ions were reduced on the seeds of AgNPs by sodium citrate in a solution of AgNO₃, which allowed for the formation of AgNPs with sizes of up to ~ 500 nm, which The formed AgNPs on the films were characterized using UV-vis spectrophotometer, scattering electron microscope and induced coupled mass spectrometer. The amount of AgNPs was estimated to be less than 0.05% of the total film weight. Even though it was coated with a small amount of AgNPs, the PDMS film exhibited reduction of E. coli and S. aureus with values of log₁₀ 4.8 and log₁₀ 5.7, respectively. The biosafety of the AgNP-attached PDMS film was examined by contact of cells with the film or film eluent. Counting of viable cells revealed no significant cytotoxicity of the in situ-fabricated AgNPs on the PDMS film.

Keywords: Antibacterial medical device; Catheter; Oxygen plasma; Silicone; Silver nanoparticles.

Fig. 1

Schematic illustration of the in situ synthesis of AgNPs on PDMS film

Fig. 2

Absorption spectra of AgNP seed-fabricated PDMS films subjected to various times of plasma treatment

Fig. 3

Effect of organic solvent residues and plasmon treatment time on the antibacterial activity of PDMS films. a Uncleaned and b cleaned PDMS films before the AgNP fabrication. c Plasma untreated and d treated PDMS films with AgNP seeds on the film

Fig. 4

Time-dependence of the AgNP growing reaction on PDMS film in a solution that contained AgNPs at 80 °C after the addition of sodium citrate. a 1 min, b 5 min, c 10 min, d 15 min, e 25 min, and f 35 min

Fig. 5

Absorption spectra of PDMS films depending on the number of rounds of the additional AgNP-growth reaction

Fig. 6

Electron microscopic analysis of the AgNP-grown PDMS films subjected to various rounds of reactions. From a to c; one, two and three rounds of reaction, respectively. d Ion mapping image and inset of d corresponding electron microscopic images of AgNP-grown PDMS films after three rounds of the AgNP growing reaction. Insets in b and c are enlarged images of the figures. 500 nm scale bar in each SEM image

Fig. 7

Photographic images of an AgNP grown PDMS film at 36 h after inoculation of S. aureus on the surface. a Control PDMS was prepared without the AgNP growing reaction. From b to d, AgNP-grown PDMS films subjected to one, two, or three rounds of reactions, respectively. Inset in each figure is an enlarged image of the figure

Fig. 8

Colony formations on Mueller–Hinton agar inoculated with diluted solution of the collected elution from the bacterial inoculum on the AgNP-grown PDMS films. a, b E. coli inoculum of 1 × 10⁵ dilution of the control and 1 × 10³ dilution of AgNP-grown PDMS film o the agar, respectively. c, d S. aureus inoculum of 1 × 10⁴ dilution of the control and 1 × dilution of AgNP-grown PDMS films, respectively

Fig. 9

Cytotoxicity tested with a eluent and b direct contact of the AgNP-grown PDMS film. Microscopic images of the tested cells grown in direct contact with c control PDMS film and d AgNP-grown PDMS films. Inset of c and d is enlarged image of each figure

Fig. 10

Photographic image of an in situ AgNP fabricated catheter for use in a pre-clinical test