Combination of silver nanoparticles and Drosera binata extract as a possible alternative for antibiotic treatment of burn wound infections caused by resistant Staphylococcus aureus.

Staphylococcus aureus is the most common infectious agent involved in the development of skin infections that are associated with antibiotic resistance, such as burn wounds. As drug resistance is a growing problem it is essential to establish novel antimicrobials. Currently, antibiotic resistance in bacteria is successfully controlled by multi-drug therapies. Here we demonstrate that secondary metabolites present in the extract obtained from Drosera binata in vitro cultures are effective antibacterial agents against S. aureus grown in planktonic culture and in biofilm. Moreover, this is the first report demonstrating the synergistic interaction between the D. binata extract and silver nanoparticles (AgNPs), which results in the spectacular enhancement of the observed bactericidal activity, while having no cytotoxic effects on human keratinocytes. Simultaneous use of these two agents in significantly reduced quantities produces the same effect, i.e. by killing 99.9% of bacteria in inoculum or eradicating the staphylococcal biofilm, as higher amounts of the agents used individually. Our data indicates that combining AgNPs with either the D. binata extract or with its pure compound (3-chloroplumbagin) may provide a safe and highly effective alternative to commonly used antibiotics, which are ineffective towards the antibiotic-resistant S. aureus

An isobologram depicting the bactericidal interaction between silver nanoparticles and pure 3-chloroplumbagin towards the planktonic culture of the <i>S. aureus</i> strain ATCC 13420.

<p>The Minimum Bactericidal Concentration was the measured effect.</p

Eradication of <i>S. aureus</i> biofilm by A) the <i>D. binata</i> extract and by B) AgNPs.

<p>The experiment was conducted using the ATCC 13420 strain. The MBEC (Minimum Biofilm Eradication Concentration) obtained from the recovery plates after 24 h of incubation at 37°C is defined as the absorbance at 600 nm below the value of 0.1. DW – dry weight.</p

An isobologram depicting the bactericidal interaction between silver nanoparticles and either the extract derived from <i>D. binata</i> or pure 3-chloroplumbagin towards planktonic cultures of <i>S. aureus</i> strains.

<p>The Minimum Bactericidal Concentration was the measured effect.</p

The structure of A) plumbagin, droserone, 3-chloroplumbagin and B) 3,3′-di-<i>O</i>-methylellagic acid.

<p>The structure of A) plumbagin, droserone, 3-chloroplumbagin and B) 3,3′-di-<i>O</i>-methylellagic acid.</p

Cytotoxic effect of A) AgNPs, the <i>D. binata</i> extract and various secondary metabolites present in <i>D. binata</i> tissues applied individually on human keratinocytes [n = 3. Data were analyzed by one-way ANOVA with Tukey's post hoc tests; p≤0.05 (*) indicates differences between the control and 1-treated cells] and B) combinations of AgNPs with either the <i>D. binata</i> extract or with pure 3-chloroplumbagin towards human dermal keratinocytes.

<p>Toxicity was assessed after 24 h of incubation at 37°C in the dark. Each point is the mean of three experiments ± s.d. DR – droserone (32 µg/ml); AgNPs – silver nanoparticles (6.15 µg/ml); DEA – 3,3′-di-O-methylellagic acid (32 µg/ml); Dbin – chloroform extract from tissues of <i>D. binata</i> (16 µg DW/ml); ChPL – 3-chloroplumbagin (32 µg/ml); PL- plumbagin (16 µg/ml); Combinations: ChPL + AgNPs – 1 µg/ml+1.54 µg/ml, respectively; Dbin + AgNPs (A) – 0.5 µg DW/ml+3.075 µg/ml, respectively; Dbin + AgNPs (B) – 8 µg DW/ml+0.2 µg/ml, respectively [n = 3. Data were analyzed by one-way ANOVA with Tukey's post hoc tests, p≤0.05 (*)].</p

Antimicrobial activity of two different types of silver nanoparticles against wide range of pathogenic bacteria

The emergence of antibiotic-resistant bacteria, particularly the most hazardous pathogens, namely Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp. (ESKAPE)-pathogens pose a significant threat to global health. Current antimicrobial therapies, including those targeting biofilms, have shown limited effectiveness against these superbugs. Nanoparticles, specifically silver nanoparticles (AgNPs), have emerged as a promising alternative for combating bacterial infections. In this study, two types of AgNPs with different physic-chemical properties were evaluated for their antimicrobial and antibiofilm activities against clinical ESKAPE strains. Two types of silver nanoparticles were assessed: spherical silver nanoparticles (AgNPs-1) and cubic-shaped silver nanoparticles (AgNPs-2). AgNPs-2, characterized by a cubic shape and higher surface-area-to-volume ratio, exhibited superior antimicrobial activity compared to spherical AgNPs-1. Both types of AgNPs demonstrated the ability to inhibit biofilm formation and disrupt established biofilms, leading to membrane damage and reduced viability of the bacteria. These findings highlight the potential of AgNPs as effective antibacterial agents against ESKAPE pathogens, emphasizing the importance of nanoparticle characteristics in determining their antimicrobial properties. Further research is warranted to explore the underlying mechanisms and optimize nanoparticle-based therapies for the management of infections caused by antibiotic-resistant bacteria

In Vitro Biological Characterization of Silver-Doped Anodic Oxide Coating on Titanium

Despite the high biocompatibility and clinical effectiveness of Ti-based implants, surface functionalization (with complex osteointegrative/antibacterial strategies) is still required. To enhance the dental implant surface and to provide additional osteoinductive and antibacterial properties, plasma electrolytic oxidation of a pure Ti was performed using a nitrilotriacetic acid (NTA)-based Ag nanoparticles (AgNP)-loaded calcium&ndash;phosphate solution. Chemical and structural properties of the surface-modified titanium were assessed using scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) and contact angle measurement. A bacterial adhesion test and cell culture biocompatibility with collagen production were performed to evaluate biological effectiveness of the Ti after the plasma electrolytic process. The NTA-based calcium&ndash;phosphate solution with Ag nanoparticles (AgNPs) can provide formation of a thick, porous plasma electrolytic oxidation (PEO) layer enriched in silver oxide. Voltage elevation leads to increased porosity and a hydrophilic nature of the newly formed ceramic coating. The silver-enriched PEO layer exhibits an effective antibacterial effect with high biocompatibility and increased collagen production that could be an effective complex strategy for dental and orthopedic implant development