Development of super nanoantimicrobials combining AgCl, tetracycline and benzalkonium chloride

Abstract

In this work, we demonstrate that a simple argentometric titration is a scalable, fast, green and robust approach for producing AgCl/antibiotic hybrid antimicrobial materials. We titrated AgNO₃ into tetracycline hydrochloride (TCH) aqueous solution, thus forming AgCl/TCH in a one-step procedure. Furthermore, we investigated the one-pot synthesis of triply synergistic super-nanoantimicrobials, combining an inorganic source of Ag⁺ ions (AgCl), a disinfecting agent (benzyl-dimethyl-hexadecyl-ammonium chloride, BAC) and a molecular antibiotic (tetracycline hydrochloride, TCH). Conventional antimicrobial tests, industrial biofilm detection protocols, and in situ IR-ATR microbial biofilm monitoring, have been adapted to understand the performance of the synthesized super-nanoantimicrobial. The resulting hybrid AgCl/BAC/TCH nanoantimicrobials are found to be synergistically active in eradicating Salmonella enterica and Lentilactobacillus parabuchneri bacteria and biofilms. This study paves the way for the development of a new class of super-efficient nanoantimicrobials that combine relatively low amounts of multiple active species into a single (nano)formulation, thus preventing the development of antimicrobial resistance towards a single active principle.

Keywords: AgCl; Antibiotic; Bioactive surfactant; Biofilm; Nanoparticles; Synergistic antimicrobials.

Fig. 1

a–c TEM images and d Histogram of 1mM AgCl/TCH. e–g TEM images and h Histogram of 10mM AgCl/BAC/TCH

Fig. 2

Positive MALDI MS spectra of a AgCl/TCH and b AgCl/BAC/TCH by using CHCA as a matrix. Interfering matrix-related peaks are labelled with an asterisk

Fig. 3

Antimicrobial susceptibility well diffusion assay: a 10 mM AgCl/BAC/TCH and 10 mM AgCl/NaCl/TCH; b 10 mM AgCl/BAC and 10 mM AgCl/NaCl, and c 10 mM TCH and 1 mM TCH against S. enterica on tryptic soy Agar (TSA)

Fig. 4

HDPE coupons into S. enterica bacterial suspension: biofilm formation (a), biofilm eradication by 10 mM AgCl/BAC/TCH (b), and 10 mM TCH (c)

Fig. 5

Temporal evolution of relevant IR bands for L. parabuchneri biofilm inhibition on the waveguide modified by AgCl/BAC/TCH coating in inactive sensing regions. Infrared ATR spectra of 8 h of biofilm inhibition (black lines); 16 h of biofilm inhibition (green lines); and 24 h (blue line) of L. parabuchneri. Signal attributions are highlighted by arrows

Fig. 6

Integrated peak values (IPVs) as a function of time for L. parabuchneri biofilm formation for 24 h of monitoring a on bare crystal and L. parabuchneri biofilm growth inhibition for 24 h of monitoring b on top of the modified crystal. The arrow indicates a decrease in the IR bands associated with the EPS content