Silver-Coated Engineered Magnetic Nanoparticles Are Promising for the Success in the Fight against Antibacterial Resistance Threat

The combination of patients with poor immune system, prolonged exposure to anti-infective drugs, and cross-infection has given rise to nosocomial infections with highly resistant pathogens, which is going to be a growing threat so termed “antibiotic resistance”. Due to their significant antimicrobial activity, silver nanoparticles are recognized as a promising candidate to fight against resistant pathogens; however, there are two major shortcomings with these nanoparticles. First, the silver nanoparticles are highly toxic to the healthy cells; second, due to the protection offered by the biofilm mode of growth, the silver nanoparticles cannot eradicate bacterial biofilms. In order to overcome these limitations, this study introduces a new class of engineered multimodal nanoparticles comprising a magnetic core and a silver ring with a ligand gap. The results indicated promising capability of the designed multimodal nanoparticles for high-yield antibacterial effects and eradication of bacterial biofilms, while the particles were completely compatible with the cells. Utilizing a gold ring as an intermediate coating on the produced nanoparticles may exploit new opportunities for theranosis applications. This will require special consideration in future works

Improved Methodology for Evaluating Nanomedicine Antibacterial Properties in Biological Fluids

Accurate assessment of nanomedicines’ antibacterial properties is pivotal for their effective use in both in vitro and in vivo settings. Conventional antibacterial activity assessment methods, involving bacterial coculture with compounds on agar plates, may not fully suit nanomedicines due to their susceptibility to alterations in physicochemical properties induced by biological fluids. Furthermore, these biological fluids might even enhance the bacterial growth. This study introduces a novel, rigorous, and reproducible methodology for evaluating nanomedicine antibacterial properties using cell culture media (i.e., DMEM-FBS10%). To assess the antibacterial activity of the nanoparticles in cell culture media, superparamagnetic iron oxide nanoparticles (SPIONs) were chosen as the model nanomedicine due to their clinical significance. A comparative analysis between the traditional and our proposed methods yielded contrasting outcomes, shedding light on the significant impact of biological fluids on nanoparticle antibacterial activities. While the conventional approach suggested the antibacterial effectiveness of SPIONs against Staphylococcus aureus, our innovative method unveiled a substantial increase in bacterial growth in the presence of biological fluids. More specifically, we found a significant increase in bacterial growth when exposed to bare SPIONs at various concentrations, while the formation of a protein corona on SPION surfaces could markedly reduce the observed bacterial growth compared to the control group. These findings underscore the necessity for more refined evaluation techniques that can better replicate the in vivo environment when studying the nanomedicine’s antibacterial capabilities

Identification of Nanoparticles with a Colorimetric Sensor Array

A simple colorimetric sensor array technique was developed for the detection of various different nanoparticles (NPs) in aqueous solutions. The sensor array consists of five different cross-reactive chemoresponsive dyes, whose visible absorbances change in response to their interactions with NPs. Although no single dye is specific for any one NP, the pattern of color changes for all dyes provides a unique molecular fingerprint for each type of NP studied. Based on the responses of various dyes, a semiquantitative determination of concentration of each type of NP could also be accomplished with excellent sensitivity (<100 ng/mL). A variety of chemically distinct NPs were unambiguously identified using a standard chemometric approaches, including gold nanospheres (2 through 40 nm diameter), gold nanorods (2.4 and 3.5 aspect ratios), and multifunctional carbon nanospheres without errors in 112 trials. This colorimetric approach may pave the way for a fast, reliable, and inexpensive method to detect nanopollution and to characterize the physiochemical properties of NPs

Comparison of the different SPIONs used in this research. Sizes and zeta potentials are presented as mean ± SD (n = 4).

<p>Comparison of the different SPIONs used in this research. Sizes and zeta potentials are presented as mean ± SD (n = 4).</p

Figure 1

<p>(a) TEM image of monodisperse iron oxide nanocrystals; Inset at the top left illustrates the selected area diffraction pattern of the SPIONs. (b) FTIR spectra of bare and coated-SPIONs with various polymers; and cell viabilities of the conventional (c) MTT- and XTT-assay and (d) modified MTT- and XTT-methods after treatment with various concentrations of CES-grafted SPIONs. Differences between obtained cell viabilities confirm the importance of toxicity method modifications of conventional methods for NPs.</p

Induced lysosomes in (a) Capan-2, (b) Panc-1, (c) HeLa, and (d) Jurkat cells were obtained upon interaction with CES-coated SPIONs.

<p>In live lysosomes assay, the lysosomes and nuclei are seen as red and blue fluorescence, respectively. Induced ROS level in (e) Capan-2, (f) Panc-1, (g) HeLa, and (h) Jurkat cells were obtained upon interaction with SPIONs. In intracellular ROS assay, the ROS level and nuclei are seen as green and blue fluorescence, respectively; (i) fluorescence intensities of induced lysosomes and ROS for all cell lines.</p

Time course variations of the hydrodynamic size of various NPs (400 µL with concentrations of 2 mM), while interacting with cell medium (1 mL of DMEM+FBS 10%).

<p>Time course variations of the hydrodynamic size of various NPs (400 µL with concentrations of 2 mM), while interacting with cell medium (1 mL of DMEM+FBS 10%).</p

(a) and (b) fluorescence intensities of induced lysosomes and ROS for all cell lines after treatment with PEG- and APTES-coated SPIONs.

<p>(a) and (b) fluorescence intensities of induced lysosomes and ROS for all cell lines after treatment with PEG- and APTES-coated SPIONs.</p

Induced lysosomes and ROS level in various cell lines upon interaction with (a) PEG- and (b) APTES-coated SPIONs.

<p>Induced lysosomes and ROS level in various cell lines upon interaction with (a) PEG- and (b) APTES-coated SPIONs.</p

Description of the cell lines used in MTT and XTT studies (DMEM: Dulbecco's modified Eagle's medium; Ham's: Nutrient Mixture F-10; FBS: fetal bovine serum; RPMI-1640 (Roswell Park Memorial Institute)).

<p>Description of the cell lines used in MTT and XTT studies (DMEM: Dulbecco's modified Eagle's medium; Ham's: Nutrient Mixture F-10; FBS: fetal bovine serum; RPMI-1640 (Roswell Park Memorial Institute)).</p