Nanomaterials as Delivery Vehicles and Components of New Strategies to Combat Bacterial Infections: Advantages and Limitations

Nanomaterials with active targeting as advanced antimicrobials

With a growing health threat of bacterial resistance to antibiotics, the nanomaterials have been extensively studied as an alternative. It is assumed that antimicrobial nanomaterials can affect bacteria by several mechanisms simultaneously and thereby overcome antibiotic resistance. Another promising potential use is employing nanomaterials as nanocarriers for antibiotics in order to overcome bacterial defense mechanisms. The passive targeting of nanomaterials is the often used strategy for bacterial treatment, including intracellular infections of macrophages. Furthermore, the specific targeting enhances the efficacy of antimicrobials and reduces side effects. This review aims to discuss advantages, disadvantages, and challenges of nanomaterials in the context of the targeting strategies for antimicrobials as advanced tools for treatments of bacterial infections. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease.

Inhibitory effects of aptamer targeted teicoplanin encapsulated PLGA nanoparticles for Staphylococcus aureus strains

Emergence of resistance to traditional antibiotic treatments necessitates alternative delivery systems. Teicoplanin is a glycopeptide antibiotic used in the treatments of serious infections caused by Gram-positive bacteria, including Methicillin Resistant Staphylococcus aureus (MRSA). One strategy to keep up with antibiotic resistance development is to limit dose and amount during treatments. Targeted delivery systems of antibiotics have been suggested as a mechanism to slow-down the evolution of resistance and to increase efficiency of the antimicrobials on already resistant pathogens. In this study, we report teicoplanin delivery nanoparticles of Poly Lactic-co-Glycolic Acid (PLGA), which are functionalized with S. aureus specific aptamers. A 32-fold decrease in minimum inhibitory concentration (MIC) values of teicoplanin for S. aureus was demonstrated for susceptible strains and about 64-fold decline in MIC value was achieved for moderately resistant clinical isolates of MRSA upon teicoplanin treatment with aptamer-PLGA nanoparticles. Although teicoplanin delivery in PLGA nanoparticles without targeting demonstrated eightfold decrease in MIC of susceptible strains of S. aureus and S. epidermidis and twofold in MIC of resistant strains, the aptamer targeting specifically decreased MIC for S. aureus, but not for S. epidermidis. Therefore, aptamer-targeted PLGA delivery of antibiotic can be an attractive alternative to combat with some of the multi-drug resistant bacterial pathogens.

Easy One-Pot Low-Temperature Synthesized Ag-ZnO Nanoparticles and Their Activity Against Clinical Isolates of Methicillin-Resistant Staphylococcus aureus

Antimicrobial resistance (AMR) is widely acknowledged as a global health problem, yet the available solutions to this problem are limited. Nanomaterials can be used as potential nanoweapons to fight against this problem. In this study, we report an easy one-pot low-temperature synthesis of Ag-ZnO nanoparticles (AZO NPs) and their targeted antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) strains. The physical properties of the samples were characterized by X-ray diffractometry (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Furthermore, minimum inhibitory concentration (MIC), zone of inhibition (ZOI), and scanning electron microscopy (SEM) images for morphological characterization of bacteria were assessed to evaluate the antibacterial activity of AZO NPs against both Gram-negative [Escherichia coli (E. coli) and Acinetobacter baumannii (A. baumannii) standard and AMR strains] and Gram-positive (S. aureus, MRSA3, and MRSA6) bacteria. The AZO NPs showed comparatively better antibacterial activity against S. aureus and MRSA strains than Gram-negative bacterial strains. This cost-effective and simple synthesis strategy can be used for the development of other metal oxide nanoparticles, and the synthesized nanomaterials can be potentially used to fight against MRSA.

Antibacterial potential of Ni-doped zinc oxide nanostructure: comparatively more effective against Gram-negative bacteria including multi-drug resistant strains

Infections by multidrug-resistant (MDR) bacteria are one of the most threatening concerns for public health. For this purpose, nanomaterials have emerged with great potential for antibacterial activity. In this paper, we report the synthesis of new Ni²⁺-doped zinc oxide (Ni-ZnO or NZO) nanostructures as targeted antibacterial agents for Gram-negative bacteria. A one-pot low-temperature solution process was used with varying compositions containing 2 or 5% Ni²⁺ relative to Zn²⁺, resulting in 2NZO or 5NZO, respectively. X-ray diffractometry, transmission electron microscopy, and X-ray photoelectron spectroscopy were used for material characterization. Further, the antibacterial activity against both Gram-negative [Escherichia coli (E. coli) and Acinetobacter baumannii (A. baumannii) strains including standard, MDR, and clinical isolates associated with mcr-1 gene] and Gram-positive (Staphylococcus aureus and Staphylococcus epidermidis) bacteria were evaluated through analysis of zone of inhibition, minimum inhibitory concentration (MIC), and scanning electron microscopy images. Among the prepared nanostructures, the 5NZO sample showed excellent antibacterial activity against MDR strains of A. baumannii and E. coli. In addition, samples of NZO generated approximately 7 to 16 times more reactive oxygen species (ROS) in E. coli compared to ZnO. Our synthesized nanomaterials have the potential to fight MDR and colistin-resistant Gram-negative bacteria.

Synthesis of Ni²⁺-doped ZnO nanoparticles and their antibacterial activity.