Nanoapatites Doped and Co-Doped with Noble Metal Ions as Modern Antibiofilm Materials for Biomedical Applications against Drug-Resistant Clinical Strains of Enterococcus faecalis VRE and Staphylococcus aureus MRSA

Effect of silver ion and silicate group on the antibacterial and antifungal properties of nanosized hydroxyapatite

Hydroxyapatite is one of the most widely used materials in biomedical applications in reparative and regenerative medicine. Doping of nanosized hydroxyapatite improves its bioactive properties, and thus, the synthesis of different types of nanohydroxyapatite with antimicrobial activity is a perspective route of modern materials science. In this study, undoped hydroxyapatite (HAp), hydroxyapatite doped with silver (HAp with 0.1, 0.5 and 1 mol% Ag+ ions), and silicate-substituted hydroxyapatite doped with silver (Si-HAp with 0.1, 0.5 and 1 mol% Ag+ ions) nanoparticles (NPs) were synthesized by microwave-assisted hydrothermal technique and sintered at 450 °C. The structural properties and composition of obtained hydroxyapatite NPs were investigated using X-ray powder diffraction (XRPD), Fourier-transformed infrared spectroscopy (FT-IR), and Energy-dispersive X-ray spectroscopy (EDS). The morphology of synthesized nanosized powders was detected using the high-resolution transmission electron microscopy (HRTEM) technique. The results of XRPD for all synthesized nanosized powders confirmed the presence of hydroxyapatite crystal structure. The FT-IR spectra confirmed the presence of functional groups characteristic of the hydroxyapatite structure. The EDS analysis of obtained materials has shown the presence of Ca, P, O, Si, and Ag elements. Significant differences in size and morphology of the obtained particles were found using HRTEM. The particles have an elongated, rod-like shape with subtle differences. Moreover, HAp doped with 1 mol% Ag+ ions and Si-HAp doped with 1 mol% Ag+ ions nanosized powders showed antibacterial activity in comparison to pure hydroxyapatite both against gram-positive and gram-negative bacterial strains (Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus epidermidis, Staphylococcus aureus, Enterococcus faecalis). These two types of hydroxyapatite NPs also demonstrated antifungal activity against reference strains of Candida albicans, Candida kruzei, and Candida tropicalis, with stronger activity observed for Si-HAp doped with silver.

Modern Microbiological Methods to Detect Biofilm Formation in Orthopedy and Suggestions for Antibiotic Therapy, with Particular Emphasis on Prosthetic Joint Infection (PJI)

Biofilm formation is a serious problem that relatively often causes complications in orthopedic surgery. Biofilm-forming pathogens invade implanted foreign bodies and surrounding tissues. Such a condition, if not limited at the appropriate time, often requires reoperation. This can be partially prevented by selecting an appropriate prosthesis material that prevents the development of biofilm. There are many modern techniques available to detect the formed biofilm. By applying them we can identify and visualize biofilm-forming microorganisms. The most common etiological factors associated with biofilms in orthopedics are: Staphylococcus aureus, coagulase-negative Staphylococci (CoNS), and Enterococcus spp., whereas Gram-negative bacilli and Candida spp. also deserve attention. It seems crucial, for therapeutic success, to eradicate the microorganisms able to form biofilm after the implantation of endoprostheses. Planning the effective targeted antimicrobial treatment of postoperative infections requires accurate identification of the microorganism responsible for the complications of the procedure. The modern microbiological testing techniques described in this article show the diagnostic options that can be followed to enable the implementation of effective treatment.

A Combination of β-Aescin and Newly Synthesized Alkylamidobetaines as Modern Components Eradicating the Biofilms of Multidrug-Resistant Clinical Strains of Candida glabrata

The current trend in microbiological research aimed at limiting the development of biofilms of multidrug-resistant microorganisms is increasingly towards the search for possible synergistic effects between various compounds. This work presents a combination of a naturally occurring compound, β-aescin, newly synthesized alkylamidobetaines (AABs) with a general structure-CnTMDAB, and antifungal drugs. The research we conducted consists of several stages. The first stage concerns determining biological activity (antifungal) against selected multidrug-resistant strains of Candida glabrata (C. glabrata) with the highest ability to form biofilms. The second stage of this study determined the activity of β-aescin combinations with antifungal compounds and alkylamidobetaines. In the next stage of this study, the ability to eradicate a biofilm on the polystyrene surface of the combination of β-aescin with alkylamidobetaines was examined. It has been shown that the combination of β-aescin and alkylamidobetaine can firmly remove biofilms and reduce their viability. The last stage of this research was to determine the safety regarding the cytotoxicity of both β-aescin and alkylamidobetaines. Previous studies on the fibroblast cell line have shown that C9 alkylamidobetaine can be safely used as a component of anti-biofilm compounds. This research increases the level of knowledge about the practical possibilities of using anti-biofilm compounds in combined therapies against C. glabrata.

Photothermal Conversion Efficiency of Silver and Gold Incorporated Nanosized Apatites for Biomedical Applications

The aim of this research was to investigate the photothermal ability of nanocrystalline hydroxyapatite (nHAp) incorporated with silver and gold. It was studied by using a recently developed technique evaluating the photothermal conversion efficiency. The heating performance of aqueous dispersions was examined under 445 and 532 nm excitation. The largest increase in temperature was found for the 2% Ag-nHAp and reached above 2 °C per mg/mL of sample (445 nm) under 90 mW laser continuous irradiation and an external light-to-heat conversion efficiency of 0.11 L/g cm. The obtained results have shown a new functionality of nanosized apatites that has not been considered before. The studied materials have also been characterized by XRPD, TEM, BET, and UV-Vis techniques. Finally, in this work, a new idea for their application was proposed: photothermal therapy.

Mechanism of Action and Efficiency of Ag3PO4-Based Photocatalysts for the Control of Hazardous Gram-Positive Pathogens

Silver phosphate and its composites have been attracting extensive interest as photocatalysts potentially effective against pathogenic microorganisms. The purpose of the present study was to investigate the mechanism of bactericidal action on cells of opportunistic pathogens. The Ag3PO4/P25 (AGP/P25) and Ag3PO4/HA (HA/AGP) powders were prepared via a co-precipitation method. Thereafter, their antimicrobial properties against Enterococcus faecalis, Staphylococcus epidermidis, and Staphylococcus aureus (clinical and reference strains) were analyzed in the dark and after exposure to visible light (VIS). The mechanism leading to cell death was investigated by the leakage of metabolites and potassium ions, oxidative stress, and ROS production. Morphological changes of the bacterial cells were visualized by transmission electron microscopy (TEM) and scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy (SEM EDS) analysis. It has been shown that Ag3PO4-based composites are highly effective agents that can eradicate 100% of bacterial populations during the 60 min photocatalytic inactivation. Their action is mainly due to the production of hydroxyl radicals and photogenerated holes which lead to oxidative stress in cells. The strong affinity to the bacterial cell wall, as well as the well-known biocidal properties of silver itself, increase undoubtedly the antimicrobial potential of the Ag3PO4-based composites.

Biofilm Formation and Genetic Diversity of Microbial Communities in Anaerobic Batch Reactor with Polylactide (PLA) Addition

In this paper, an anaerobic digestion (AD) study was conducted on confectionery waste with granular polylactide (PLA) as a cell carrier. Digested sewage sludge (SS) served as the inoculum and buffering agent of systems. This article shows the results of the analyses of the key experimental properties of PLA, i.e., morphological characteristics of the microstructure, chemical composition and thermal stability of the biopolymer. The evaluation of quantitative and qualitative changes in the genetic diversity of bacterial communities, performed using the state-of-the-art next generation sequencing (NGS) technique, revealed that the material significantly enhanced bacterial proliferation; however, it does not change microbiome biodiversity, as also confirmed via statistical analysis. More intense microbial proliferation (compared to the control sample, without PLA and not digested, CW-control, CW-confectionery waste) may be indicative of the dual role of the biopolymer-support and medium. Actinobacteria (34.87%) were the most abundant cluster in the CW-control, while the most dominant cluster in digested samples was firmicutes: in the sample without the addition of the carrier (CW-dig.) it was 68.27%, and in the sample with the addition of the carrier (CW + PLA) it was only 26.45%, comparable to the control sample (CW-control)-19.45%. Interestingly, the number of proteobacteria decreased in the CW-dig. sample (17.47%), but increased in the CW + PLA sample (39.82%) compared to the CW-control sample (32.70%). The analysis of biofilm formation dynamics using the BioFlux microfluidic system shows a significantly faster growth of the biofilm surface area for the CW + PLA sample. This information was complemented by observations of the morphological characteristics of the microorganisms using fluorescence microscopy. The images of the CW + PLA sample showed carrier sections covered with microbial consortia.

Magnesium Hydroxide Nanoparticles Inhibit the Biofilm Formation of Cariogenic Microorganisms

Although various caries-preventive agents have been developed, dental caries is still a leading global disease, mostly caused by biological factors such as mutans streptococci. Magnesium hydroxide nanoparticles have been reported to exhibit antibacterial effects; however, they are rarely used in oral care practical applications. In this study, we examined the inhibitory effect of magnesium hydroxide nanoparticles on biofilm formation by Streptococcus mutans and Streptococcus sobrinus-two typical caries-causing bacteria. Three different sizes of magnesium hydroxide nanoparticles (NM80, NM300, and NM700) were studied, all of which inhibited biofilm formation. The results showed that the nanoparticles were important for the inhibitory effect, which was not influenced by pH or the presence of magnesium ions. We also determined that the inhibition process was mainly contact inhibition and that medium (NM300) and large (NM700) sizes were particularly effective in this regard. The findings of our study demonstrate the potential applications of magnesium hydroxide nanoparticles as caries-preventive agents.

A Metal-Containing NP Approach to Treat Methicillin-Resistant Staphylococcus aureus (MRSA): Prospects and Challenges

Methicillin-resistant Staphylococcus aureus (MRSA) is an important cause of pneumonia in humans, and it is associated with high morbidity and mortality rates, especially in immunocompromised patients. Its high rate of multidrug resistance led to an exploration of novel antimicrobials. Metal nanoparticles have shown potent antibacterial activity, thus instigating their application in MRSA. This review summarizes current insights of Metal-Containing NPs in treating MRSA. This review also provides an in-depth appraisal of opportunities and challenges in utilizing metal-NPs to treat MRSA.

Quantitative and Qualitative Changes in the Genetic Diversity of Bacterial Communities in Anaerobic Bioreactors with the Diatomaceous Earth/Peat Cell Carrier

This paper analyses the impact of the diatomaceous earth/peat (DEP; 3:1) microbial carrier on changes in the bacterial microbiome and the development of biofilm in the anaerobic digestion (AD) of confectionery waste, combined with digested sewage sludge as inoculum. The physicochemical properties of the carrier material are presented, with particular focus on its morphological and dispersion characteristics, as well as adsorption and thermal properties. In this respect, the DEP system was found to be a suitable carrier for both mesophilic and thermophilic AD. The evaluation of quantitative and qualitative changes in the genetic diversity of bacterial communities, carried out using next-generation sequencing (NGS), showed that the material has a modifying effect on the bacterial microbiome. While Actinobacteria was the most abundant cluster in the WF-control sample (WF—waste wafers), Firmicutes was the dominant cluster in the digested samples without the carrier (WF-dig.; dig.—digested) and with the carrier (WF + DEP). The same was true for the count of Proteobacteria, which decreased twofold during biodegradation in favor of Synergistetes. The Syntrophomonas cluster was identified as the most abundant genus in the two samples, particularly in WF + DEP. This information was supplemented by observations of morphological features of microorganisms carried out using fluorescence microscopy. The biodegradation process itself had a significant impact on changes in the microbiome of samples taken from anaerobic bioreactors, reducing its biodiversity. As demonstrated by the results of this innovative method, namely the BioFlux microfluidic flow system, the decrease in the number of taxa in the digested samples and the addition of DEP contributed to the microbial adhesion in the microfluidic system and the formation of a stable biofilm.

In Silico Contact Pressure of Metal-on-Metal Total Hip Implant with Different Materials Subjected to Gait Loading

The use of material for implant bearing has a vital role in minimizing failures that endanger implant recipients. Evaluation of contact pressure of bearing material can be the basis for material selection and have correlations with wear that contribute to the need of revision operations. The current paper aims to investigate three different metallic materials, namely cobalt chromium molybdenum (CoCrMo), stainless steel 316L (SS 316L), and titanium alloy (Ti6Al4V) for application in metal-on-metal bearing of total hip implant in terms of contact pressure. In silico model based on finite element simulation has been considered to predict contact pressure of metal-on-metal bearings under normal walking conditions. It is found that the use of Ti6Al-4V-on-Ti6Al4V is superior in its ability to reduce contact pressure by more than 35% compared to the other studied metal-on-metal couple bearings.

Morphological Changes, Antibacterial Activity, and Cytotoxicity Characterization of Hydrothermally Synthesized Metal Ions-Incorporated Nanoapatites for Biomedical Application

The objective of this study was to prepare hydroxyapatite (HA) with potential antibacterial activity against gram-negative and gram-positive bacteria by incorporating different atomic ratios of Cu²⁺ (0.1–1.0%), Mg²⁺ (1.0–7.0%), and Zn²⁺ (1.0–7.0%) to theoretically replace Ca²⁺ ions during the hydrothermal synthesis of grown precipitated HA nanorods. This study highlights the role of comparing different metal ions on synthetic nanoapatite in regulating the antibacterial properties and toxicity. The comparisons between infrared spectra and between diffractograms have confirmed that metal ions do not affect the formation of HA phases. The results show that after doped Cu²⁺, Mg²⁺, and Zn²⁺ ions replace Ca²⁺, the ionic radius is almost the same, but significantly smaller than that of the original Ca²⁺ ions, and the substitution effect causes the lattice distance to change, resulting in crystal structure distortion and reducing crystallinity. The reduction in the length of the nanopatites after the incorporation of Cu²⁺, Mg²⁺, and Zn²⁺ ions confirmed that the metal ions were mainly substituted during the growth of the rod-shape nanoapatite Ca²⁺ distributed along the longitudinal site. The antibacterial results show that nanoapatite containing Cu²⁺ (0.1%), Mg²⁺ (3%), and Zn²⁺ (5–7%) has obvious and higher antibacterial activity against gram-positive bacteria Staphylococcus aureus within 2 days. The antibacterial effect against the gram-negative bacillus Escherichia coli is not as pronounced as against Staphylococcus aureus. The antibacterial effect of Cu²⁺ substituted Ca²⁺ with an atomic ratio of 0.1~1.0% is even better than that of Mg²⁺- and Zn²⁺- doped with 1~7% groups. In terms of cytotoxicity, nanoapatites with Cu²⁺ (~0.2%) exhibit cytotoxicity, whereas Mg²⁺- (1–5%) and Zn²⁺- (~1%) doped nanoapatites are biocompatible at low concentrations but become cytotoxic as ionic concentration increases. The results show that the hydrothermally synthesized nanoapatite combined with Cu²⁺ (0.2%), Mg²⁺ (3%), and Zn²⁺ (3%) exhibits low toxicity and high antibacterial activity, which provides a good prospect for bypassing antibiotics for future biomedical applications.