Antibacterial biomimetic hybrid films

Abstract

In this work, we present a novel method to prepare a hybrid coating based on dextran grafted to a substrate and embedded with silver nanoparticles (Ag NPs). First, the Ag NPs are synthesized in situ in the presence of oxidized dextran in solution. Second, the oxidized dextran is exposed to an amine functionalized surface resulting in the simultaneous grafting of dextran and the trapping of Ag NPs within the layer. The NP loading is controlled by the concentration of silver nitrate, which is 2 mM (DEX-Ag2) and 5 mM (DEX-Ag5). The dried film thickness increases with silver nitrate concentration from 2 nm for dextran to 7 nm and 12 nm for DEX-Ag2 and DEX-Ag5, respectively. The grafted dextran film displays features with a diameter and height of ~ 50 nm and 2 nm, respectively. For the DEX-Ag2 and DEX-Ag5, the dextran features as well as individual Ag NPs (~ 5 nm) and aggregates of Ag NPs are observed. Larger and more irregular aggregates are observed for DEX-Ag5. Overall, the Ag NPs are embedded in the dextran film as suggested by AFM and UVO studies. In terms of its antimicrobial activity, DEX-Ag2 resists bacterial adhesion to a greater extent than DEX-Ag5, which in turn is better than dextran and silicon. Because these antibacterial hybrid coatings can be grafted to a variety of surfaces, many biomedical applications can be envisioned, ranging from coating implants to catheters.

A facile route to synthesize nanogels doped with silver nanoparticles

“…In previous work, we demonstrated that oxidized dextran, i.e., aldehyde and hydroxyl groups, could reduce silver cations and stabilize the resulting Ag NPs in aqueous solution (Ferrer, Hickok 2012). Another hydroxyl based polysaccharide, starch, has also been employed to reduce Ag NPs in solution (Vigneshwaran 2006).…”

Designing nanogel carriers for antibacterial applications

“…However, the comparison between different systems is not straightforward because the position, shape and intensity of the SPR depends on the dielectric constant of the particle and medium, the electronic interactions between the stabilizer and NPs, and the size, shape and the size dispersity [24]. For instance, Ag NPs (~ 5 nm) prepared in situ in dextran solution exhibit a SPR at 412 nm [7] whereas Ag NPs having similar size but prepared in situ in a NG1:1 solution exhibit a peak absorption at 430 nm. Furthermore, a blue shift of the SPR is expected as particle size decreases, whereas the results in Figure 3 showed a slight red shift.…”

“…The synthesis of NGs was carried out as previously described, via a Maillard heating reaction followed by heat-gelation at 80 °C [7]. This methodology leads to core-shell type NG with a lysozyme-rich core and a dextran-rich shell [11].…”

“…Biologically, Ag NPs show antimicrobial and anti-inflammatory properties [1-3], which are the subject of intense research aimed at using Ag NPs in disease diagnosis, treatment of infection and imaging, among many others [4, 5]. For instance, antibacterial, biocompatible coatings were developed by embedding Ag NPs (~ 5 nm) in dextran [6, 7] and Ag NPs (~ 20 nm) stabilized with egg white were used to enhance efficacy in radiotherapy for 231 tumor cells [8]. Moreover, surface enhanced Raman spectroscopy was used to detect strains of the respiratory syncytial virus using substrates composed of silver nanorods [9].…”

“…Recently, we developed a novel and simple synthesis route for creating nanosized silver particles (~5 nm) inside a relatively inert and biocompatible NG (~160 nm) [7, 11]. This NG consists of a lysozyme core and a dextran shell.…”