Biomolecule-corona formation confers resistance of bacteria to nanoparticle-induced killing: Implications for the design of improved nanoantibiotics

ROS-Responsive Poly(α-l-lysine)-Based Nanoparticles Loaded with Doxycycline Combat Oxidative Stress and Bacterial Infection

Bacterial pneumonia is one of the major threats in clinical practice, and the reactive oxygen species (ROS) generated at the infection site can exacerbate the damage. Currently, conventional antibiotic therapies have low utilization, and their excessive use can result in substantial toxicity. Nanocarrier systems provide an ideal approach for treating bacterial infection by facilitating more efficient utilization of antibiotics. In this study, the ROS-responsive amphiphilic nanoparticles (NPs) are developed and used to encapsulate the antibiotic doxycycline (DOXY) to achieve antibacterial and antioxidant functionalities. The NPs are prepared from poly(α-l-lysine) (α-PLL) and phenylboronic acid pinacol ester simultaneously conjugated carbonyldiimidazole (abbreviated as CDIPB). The phenylboronic acid ester groups on CDIPB could react with excessive ROS to suppress oxidative damage at the infection site. The ROS-responsive degradation of CDIPB also facilitates the rapid release of internal DOXY, effectively killing the accumulated bacteria. Additionally, in vitro cell experiments demonstrate the good biocompatibility of the NPs. These results suggest that the ROS-responsive amphiphilic nanoparticles can serve as a novel nanoplatform for the treatment of bacterial pneumonia.

Mechanisms of bacterial resistance to environmental silver and antimicrobial strategies for silver: A review

The good antimicrobial properties of silver make it widely used in food, medicine, and environmental applications. However, the release and accumulation of silver-based antimicrobial agents in the environment is increasing with the extensive use of silver-based antimicrobials, and the prevalence of silver-resistant bacteria is increasing. To prevent the emergence of superbugs, it is necessary to exercise rational and strict control over drug use. The mechanism of bacterial resistance to silver has not been fully elucidated, and this article provides a review of the progress of research on the mechanism of bacterial resistance to silver. The results indicate that bacterial resistance to silver can occur through inducing silver particles aggregation and Ag+ reduction, inhibiting silver contact with and entry into cells, efflux of silver particles and Ag+ in cells, and activation of damage repair mechanisms. We propose that the bacterial mechanism of silver resistance involves a combination of interrelated systems. Finally, we discuss how this information can be used to develop the next generation of silver-based antimicrobials and antimicrobial therapies. And some antimicrobial strategies are proposed such as the "Trojan Horse" - camouflage, using efflux pump inhibitors to reduce silver efflux, working with "minesweeper", immobilization of silver particles.

Bioactive silver nanoparticles fabricated using Lasiurus scindicus and Panicum turgidum seed extracts: anticancer and antibacterial efficiency

Applying extracts from plants is considered a safe approach in biomedicine and bio-nanotechnology. The present report is considered the first study that evaluated the seeds of Lasiurus scindicus and Panicum turgidum as biogenic agents in the synthesis of silver nanoparticles (AgNPs) which had bioactivity against cancer cells and bacteria. Assessment of NPs activity against varied cell lines (colorectal cancer HCT116 and breast cancer MDA MBA 231 and MCF 10A used as control) was performed beside the antibacterial efficiency. Different techniques (DLS, TEM, EDX and FTIR) were applied to characterize the biosynthesized AgNPs. The phytochemicals from both L. scindicus and Panicum turgidum were identified by GC-MS analysis. Spherical monodisperse NPs at average diameters of 149.6 and 100.4 nm were obtained from seed extract of L. scindicus (L-AgNPs) and P. turgidum, (P-AgNPs) respectively. A strong absorption peak at 3 keV is observed by the EDX spectrum in the tested NPs. Our study provided effective NPs in mitigating the tested cell lines and the lowest IC50 were 7.8 and 10.30 for MDA MB231 treated by L-AgNPs and P-AgNPs, respectively. Both fabricated NPs might differentially target the MDA MB231 cells compared to HCT116 and MCF10A. Ultrastructural changes and damage for the NPs-treated MDA MB231 cells were studied using TEM and LSM analysis. Antibacterial activity was also observed. About 200 compounds were identified in L. scindicus and P. turgidum by GC-MS analysis might be responsible for the NPs reduction and capping abilities. Efficient NPs against cancer cells and microbes were obtained, however large-scale screening is needed to validate our findings.

The biomolecular gastrointestinal corona in oral drug delivery

The formation of a biomolecular corona on exogenous particles in plasma is well studied and is known to dictate the biodistribution and cellular interactions of nanomedicine formulations. In contrast, while the oral route is the most favorable administration method for pharmaceuticals, little is known about the formation and composition of the corona formed by biomolecules on particles within the gastrointestinal tract. This work reviews the current literature understanding of (1) the formation of drug particles after oral administration, (2) the formation of a biomolecular corona within the gastrointestinal tract ("the gastrointestinal corona"), and (3) the possible implications of the formation of a gastrointestinal corona on the interactions of drug particles with their biological environment. In doing so, this work aims to establish the significance of the formation of a gastrointestinal corona in oral drug delivery to ultimately arrive at new avenues to control the behavior of orally administered pharmaceuticals.

Acmella oleracea induced nanostructured Ca2Fe2O5 for evaluation of photo catalytic degradation of cardiovascular drugs and bio toxicity

Biosynthesis of nanoparticles is increasingly becoming popular due to the demand for sustainable technologies worldwide. In the present investigation, Acmella oleracea plant extract fuelled combustion technique followed by calcination at 600 °C was adopted to prepare nanocrystalline Ca₂Fe₂O₅. The prepared nano compound was characterised using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Ultra Violet (UV) spectroscopy, Infrared (IR) spectroscopy and its role was assessed for photocatalytic pollutant degradation along with bactericidal action in the concentration range of 1 μg/mL to 320 μg/mL. The photocatalytic degradation efficiency of pollutant drugs Clopidogrel Bisulphate and Asprin used for cardiovascular disorders is around 80% with 10 mg/L photocatalyst. The results showed that the photocatalytic activity increased with rising pH from 4, to 10, along with a significant antibacterial action against Enterococcus faecalis bacteria and a slight cytotoxic effect at high concentrations. The antibacterial property was reinforced by Minimum inhibitory concentrations (MIC) and Minimum bactericidal concentrations (MBC) studies with an average value of 0.103 at 600 nm which was further proved by significant anti-biofilm activeness. Adhesion tests in conjunction with cryogenic-scanning electron microscopy displayed a morphological change through agglomeration that caused an expansion in nano particles from 181 nm to 223.6 nm due to internalization followed by inactivation of bacteria. In addition, the non-toxicity of nano Ca₂Fe₂O₅ was confirmed by subtle cytological changes in microscopic images of Allium Cepa root cells in the concentration range 0.01-100 μg/mL and a slight inhibition in HeLa cell proliferation indicated by IC₅₀ value of 170.94 μg/mL. In total, the current investigation for the first time reveals the application of bio based synthesis of Nano Ca₂Fe₂O₅ to new possibilities in bioremediation namely degrading cardiovascular pharmaceutical pollutants, endodontic antibacterial action and cytological activity.

An efficient metal-organic framework-based drug delivery platform for synergistic antibacterial activity and osteogenesis

Bone implants for clinical application should be endowed with antibacterial activity, biocompatibility, and even osteogenesis-promoting properties. In this work, metal-organic framework (MOF) based drug delivery platform was used to modify titanium implants for improved clinical applicability. Methyl Vanillate@Zeolitic Imidazolate Framework-8 (MV@ZIF-8) was immobilized on the polydopamine (PDA) modified titanium. The sustainable release of the Zn²⁺ and MV causes substantial oxidative damage to Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The increased reactive oxygen species (ROS) significantly up-regulates the expression of oxidative stress and DNA damage response genes. Meanwhile, the structural disruption of lipid membranes caused by the ROS, the damage caused by Zinc active sites and the damage accelerated by the MV are both involved in inhibiting bacterial proliferation. The up-regulated expression of the osteogenic-related genes and proteins indicated that the MV@ZIF-8 could effectively promote the osteogenic differentiation of the human bone mesenchymal stem cells (hBMSCs). RNA sequencing and Western blotting analysis revealed that the MV@ZIF-8 coating activates the canonical Wnt/β-catenin signaling pathway through the regulation of tumor necrosis factor (TNF) pathway, thereby promoting the osteogenic differentiation of the hBMSCs. This work demonstrates a promising application of the MOF-based drug delivery platform in bone tissue engineering.

Biogenic Selenium Nanoparticles in Biomedical Sciences: Properties, Current Trends, Novel Opportunities and Emerging Challenges in Theranostic Nanomedicine

Selenium is an important dietary supplement and an essential trace element incorporated into selenoproteins with growth-modulating properties and cytotoxic mechanisms of action. However, different compounds of selenium usually possess a narrow nutritional or therapeutic window with a low degree of absorption and delicate safety margins, depending on the dose and the chemical form in which they are provided to the organism. Hence, selenium nanoparticles (SeNPs) are emerging as a novel therapeutic and diagnostic platform with decreased toxicity and the capacity to enhance the biological properties of Se-based compounds. Consistent with the exciting possibilities offered by nanotechnology in the diagnosis, treatment, and prevention of diseases, SeNPs are useful tools in current biomedical research with exceptional benefits as potential therapeutics, with enhanced bioavailability, improved targeting, and effectiveness against oxidative stress and inflammation-mediated disorders. In view of the need for developing eco-friendly, inexpensive, simple, and high-throughput biomedical agents that can also ally with theranostic purposes and exhibit negligible side effects, biogenic SeNPs are receiving special attention. The present manuscript aims to be a reference in its kind by providing the readership with a thorough and comprehensive review that emphasizes the current, yet expanding, possibilities offered by biogenic SeNPs in the biomedical field and the promise they hold among selenium-derived products to, eventually, elicit future developments. First, the present review recalls the physiological importance of selenium as an oligo-element and introduces the unique biological, physicochemical, optoelectronic, and catalytic properties of Se nanomaterials. Then, it addresses the significance of nanosizing on pharmacological activity (pharmacokinetics and pharmacodynamics) and cellular interactions of SeNPs. Importantly, it discusses in detail the role of biosynthesized SeNPs as innovative theranostic agents for personalized nanomedicine-based therapies. Finally, this review explores the role of biogenic SeNPs in the ongoing context of the SARS-CoV-2 pandemic and presents key prospects in translational nanomedicine.

"Self-Defensive" Antifouling Zwitterionic Hydrogel Coatings on Polymeric Substrates

In biomedicine fields, biofouling can easily occur on devices such as sensors and catheters, causing some iatrogenic infections, which menace the lives and health of patients greatly. Therefore, it is of great significance to solve the problems of bacterial infection on the surfaces of medical devices. In this paper, "self-defensive" and antifouling zwitterionic hydrogel coatings were prepared by network interpenetration of the hydrogel and the polymeric substrates. The zwitterionic polysulfobetaine methacrylate (PSBMA) hydrogel coatings resisted most of the bacteria to adhere on the substrates. When a few bacteria were lucky to escape the antifouling defense and adhered to the coatings, gentamicin sulfate (GS) would be released under the trigger of a weakly acidic environment caused by bacterial metabolism to kill these bacteria. Simultaneously, the coatings of the bacteria-adhering sites would be degraded by hyaluronidase secreted by these bacteria and peeled off to remove the bacteria and renew the antifouling surfaces. The antifouling properties and mechanism of the self-defensive behavior of the hydrogel coatings on polymeric substrates were investigated. Furthermore, the in vitro and in vivo antibacterial performances, as well as the biocompatibility of the coatings, were demonstrated. The results suggested that the self-defensive antifouling zwitterionic hydrogel coatings hold great potential to be used on the surfaces of polymeric medical devices.

Nanobiotics against antimicrobial resistance: harnessing the power of nanoscale materials and technologies

Given the spasmodic increment in antimicrobial resistance (AMR), world is on the verge of “post-antibiotic era”. It is anticipated that current SARS-CoV2 pandemic would worsen the situation in future, mainly due to the lack of new/next generation of antimicrobials. In this context, nanoscale materials with antimicrobial potential have a great promise to treat deadly pathogens. These functional materials are uniquely positioned to effectively interfere with the bacterial systems and augment biofilm penetration. Most importantly, the core substance, surface chemistry, shape, and size of nanomaterials define their efficacy while avoiding the development of AMR. Here, we review the mechanisms of AMR and emerging applications of nanoscale functional materials as an excellent substitute for conventional antibiotics. We discuss the potential, promises, challenges and prospects of nanobiotics to combat AMR.

Biological Impacts of Reduced Graphene Oxide Affected by Protein Corona Formation

Applications of reduced graphene oxide (rGO) in many different areas have been gradually increasing owing to its unique physicochemical characteristics, demanding more understanding of their biological impacts. Herein, we assessed the toxicological effects of rGO in mammary epithelial cells. Because the as-synthesized rGO was dissolved in sodium cholate to maintain a stable aqueous dispersion, we hypothesize that changing the cholate concentration in the dispersion may alter the surface property of rGO and subsequently affect its cellular toxicity. Thus, four types of rGO were prepared and compared: rGO dispersed in 4 and 2 mg/mL sodium cholate, labeled as rGO and concentrated-rGO (c-rGO), respectively, and rGO and c-rGO coated with a protein corona through 1 h incubation in culture media, correspondingly named pro-rGO and pro-c-rGO. Notably, c-rGO and pro-c-rGO exhibited higher toxicity than rGO and pro-rGO and also caused higher reactive oxygen species production, more lipid membrane peroxidation, and more significant disruption of mitochondrial-based ATP synthesis. In all toxicological assessments, pro-c-rGO induced more severe adverse impacts than c-rGO. Further examination of the material surface, protein adsorption, and cellular uptake showed that the surface of c-rGO was coated with a lower content of surfactant and adsorbed more proteins, which may result in the higher cellular uptake observed with pro-c-rGO than pro-rGO. Several proteins involved in cellular redox mediation were also more enriched in pro-c-rGO. These results support the strong correlation between dispersant coating and corona formation and their subsequent cellular impacts. Future studies in this direction could reveal a deeper understanding of the correlation and the specific cellular pathways involved and help gain knowledge on how the toxicity of rGO could be modulated through surface modification, guiding the sustainable applications of rGO.

Antibacterial and Antibiofilm Activity of Mercaptophenol Functionalized-Gold Nanorods Against a Clinical Isolate of Methicillin-Resistant Staphylococcus aureus

Gold nanorods (AuNRs) were synthesized by the seed-mediated wet chemical method using a binary surfactant system. AuNRs were stabilized with polyethylene glycol, then functionalized with 4-mercaptophenol (4-MPH) ligand by surface ligand exchange. The surface-functionalized AuNRs (4-MPH-AuNRs) exhibited a typical UV–vis spectrum of AuNRs with a slightly shifted longitudinal peak. Furthermore, 4-MPH-AuNRs demonstrated a similar Fourier-Transformed Infrared spectrum to 4-MPH and a fading of the thiol band, which suggests a successful functionalization through thiol-gold binding. The antibacterial and antibiofilm activities of 4-MPH-AuNRs were evaluated against a clinical isolate of Methicillin-Resistant Staphylococcus aureus (MRSA). The results indicate that 4-MPH-AuNRs exhibit a bactericidal activity with a minimum inhibitory concentration (MIC) of ~ 6.25 $$\upmu$$ μ g/mL against a planktonic suspension of MRSA. Furthermore, 4-MPH-AuNRs resulted in a 1.8–2.9 log-cycle reduction of MRSA biofilm viable count over a concentration range of 100–6.0 $$\upmu$$ μ g/mL. The bacterial uptake of the surface-modified nanorods was investigated by inductively coupled plasma-optical emission spectroscopy (ICP-OES) and scanning electron microscopy (SEM) imaging; the results reveal that the nanorods were internalized into the bacterial cells after 6 h (h) of exposure. SEM imaging revealed a significant accumulation of the nanorods at the bacterial cell wall and a possible cellular internalization. Thus, 4-MPH-AuNRs can be considered a potential antibacterial agent, particularly against MRSA strain biofilms.

Antibacterial approaches in tissue engineering using metal ions and nanoparticles: From mechanisms to applications

Bacterial infection of implanted scaffolds may have fatal consequences and, in combination with the emergence of multidrug bacterial resistance, the development of advanced antibacterial biomaterials and constructs is of great interest. Since decades ago, metals and their ions had been used to minimize bacterial infection risk and, more recently, metal-based nanomaterials, with improved antimicrobial properties, have been advocated as a novel and tunable alternative. A comprehensive review is provided on how metal ions and ion nanoparticles have the potential to decrease or eliminate unwanted bacteria. Antibacterial mechanisms such as oxidative stress induction, ion release and disruption of biomolecules are currently well accepted. However, the exact antimicrobial mechanisms of the discussed metal compounds remain poorly understood. The combination of different metal ions and surface decorations of nanoparticles will lead to synergistic effects and improved microbial killing, and allow to mitigate potential side effects to the host. Starting with a general overview of antibacterial mechanisms, we subsequently focus on specific metal ions such as silver, zinc, copper, iron and gold, and outline their distinct modes of action. Finally, we discuss the use of these metal ions and nanoparticles in tissue engineering to prevent implant failure.

IsoMAG-An Automated System for the Immunomagnetic Isolation of Squamous Cell Carcinoma-Derived Circulating Tumor Cells

BACKGROUND

detailed information about circulating tumor cells (CTCs) as an indicator of therapy response and cancer metastasis is crucial not only for basic research but also for diagnostics and therapeutic approaches. Here, we showcase a newly developed IsoMAG IMS system with an optimized protocol for fully automated immunomagnetic enrichment of CTCs, also revealing rare CTC subpopulations.

METHODS

using different squamous cell carcinoma cell lines, we developed an isolation protocol exploiting highly efficient EpCAM-targeting magnetic beads for automated CTC enrichment by the IsoMAG IMS system. By FACS analysis, we analyzed white blood contamination usually preventing further downstream analysis of enriched cells.

RESULTS

1 µm magnetic beads with tosyl-activated hydrophobic surface properties were found to be optimal for automated CTC enrichment. More than 86.5% and 95% of spiked cancer cells were recovered from both cell culture media or human blood employing our developed protocol. In addition, contamination with white blood cells was minimized to about 1200 cells starting from 7.5 mL blood. Finally, we showed that the system is applicable for HNSCC patient samples and characterized isolated CTCs by immunostaining using a panel of tumor markers.

CONCLUSION

Herein, we demonstrate that the IsoMAG system allows the detection and isolation of CTCs from HNSCC patient blood for disease monitoring in a fully-automated process with a significant leukocyte count reduction. Future developments seek to integrate the IsoMAG IMS system into an automated microfluidic-based isolation workflow to further facilitate single CTC detection also in clinical routine.

Spectroscopic Analysis and Microbicidal Effect of Ag/TiO2-SiO2 Bionanocatalysts

Silver, especially nanostructured silver, has been found to exhibit antimicrobial properties by disrupting the function of bacterial cell walls. Nonetheless, strains of bacteria have been reported to resist silver nanoparticles. The highly efficient mutational mechanisms of bacteria, capable of overcoming modern antimicrobial compounds, make it critical to develop new materials that target genetic material, regardless of nucleotide sequence or protein structure, without being toxic to the patient. This work evaluates the microbicidal properties of a catalytic, nanostructured, organically functionalized, titanosilicate matrix (bionanocatalysts) impregnated with silver. The bionanocatalysts were synthesized by the sol-gel method using silver acetate as the silver precursor. The effect of the bionanocatalysts against clinically important strains of bacteria and yeasts was evaluated. In addition, the physicochemical composition and in vitro reactivity on DNA were studied. The antibiogram analysis revealed that the compound could inhibit the growth (inhibition halos of up to 15 ± 0.9 mm) of all the strains studied (bacteria and yeasts) at low concentrations of silver, thus reducing the toxicity associated with platinum. In this work, by adding silver in the catalytic TiO2-SiO2 matrix, the intrinsic microbicidal properties of the metal were enhanced: the results provided a valuable compound exhibiting reduced toxicity and antimicrobial effects that could potentially be used as a potent disinfectant against drug-resistant strains, as found in hospitals, for instance.

Identification of cytokeratin24 as a tumor suppressor for the management of head and neck cancer

To improve management of head and neck squamous cell carcinoma patients, we need to increase our understanding of carcinogenesis, to identify biomarkers, and drug targets. This study aimed to identify novel biomarkers by providing transcriptomics profiles of matched primary tumors, lymph node metastasis, and non-malignant tissue of 20 HNSCC patients as well as by bioinformatic analyses of a TCGA HNSCC cohort, comprising 554 patients. We provide cancer cell signaling networks differentially expressed in tumors versus metastases, such as mesenchymal-epithelial transition, and structural integrity networks. As a proof of principle study, we exploited the data sets and performed functional analyses of a novel cytokeratin, cytokeratin24 (cKRT24), which had not been described as biomarker for tumors before. Survival analysis revealed that low cKRT24 expression correlated with poor overall survival in HNSCC. Experimentally, downregulation of cKRT24 in primary tumors, metastases, and HNSCC cell lines was verified on mRNA and protein level. Cloning and ectopic overexpression of cKRT24 not only affected viability and growth of HNSSC cell lines, but also inhibited tumor growth in murine xenograft studies. We conclude that cKRT24 functions as a tumor suppressor in HNSCC, and may serve as an additional prognostic biomarker and novel target to support current HNSCC treatments.

Biological Potential of Silver Nanoparticles Mediated by Leucophyllum frutescens and Russelia equisetiformis Extracts

Awareness about environmental concerns is increasing, specially the pollution resulting from nanoparticles (NPs) production, which has led to great interest in the usage of biogenic agents for their fabrication. The current investigation used eco-friendly organic phytomolecules from Leucophyllum frutescens and Russelia equisetiformis leaves extract for the first time in the fabrication of silver NPs from silver ions and further an assessment of their biological activities was performed. The leaves extract from both plant sources were used as capping and reducing agents and added to AgNO₃. The mixtures were observed for colour changes, and after a stable dark brown colour was obtained, the NPs were separated and further investigated using dynamic light scattering, transmission electron microscopy and energy-dispersive X-ray spectroscopy. The Fourier transform infrared spectroscopy technique was employed to determine the active organic ingredients in the plant extracts. The prepared NPs were tested against three cell lines (two cancer ones and one normal control) and the effects observed using TEM and confocal laser scanning microscopy (LSM). Antibacterial activity against two Gram positive and two Gram negative species was examined and the synergistic effect of the ampicillin-NPs conjugate was studied. Findings showed successful conversion of Ag ions into L-AgNPs and R-AgNPs achieved using L.frutescens and R. equisetiformis extracts, respectively. A mean size of 112.9 nm for L-AgNPs and 151.7 nm for R-AgNPs and negative zeta potentials were noted. TEM analysis showed spherical NPs and EDS indicated Ag at 3 keV. Reduction in cancer cell viability with low half-maximal inhibitory concentrations was noted for both tested NPs. Structural changes and apoptotic features in the treated cancer cell lines were noted by TEM and cell death was confirmed by LSM. Furthermore, higher antibacterial activity was noticed against Gram positive compared with Gram negative bacteria as well as high synergistic effect was noted for the Amp-NPs conjugate, specially against Gram positive bacteria. The current investigation has thus developed an eco-friendly NPs synthesis route by applying plant extracts to efficiently produce NPs endowed with potential cytotoxic and antibacterial capacity, which therefore could be recommended as new approaches to overcome human diseases with minimal environmental impact.

Enhanced Antibacterial and Anti-Biofilm Activities of Antimicrobial Peptides Modified Silver Nanoparticles

Background

The biofilms could protect bacteria from antibiotics and promote the production of drug-resistant strains, making the bacteria more difficult to be eradicated. Thus, we developed an AMP@PDA@AgNPs nanocomposite, which is formed by modifying silver nanoparticles (AgNPs) with antimicrobial peptides (AMP) modified nanocomposite to destroy biofilm in this study.

Methods

The AMP@PDA@AgNPs nanocomposite was prepared with polymerization method and characterized by using ultraviolet-visible (UV-vis) spectroscopy, dynamic light scattering (DLS), Fourier transform-infrared spectroscopy (FT-IR), and transmission electron microscope (TEM). The antibacterial effects of the nanocomposite were investigated by using agar diffusion method and minimum inhibitory concentration (MIC) test. The quantitative analysis of the biofilm formation by the nanocomposite was conducted using crystal violet staining and confocal laser scanning microscope (CLSM).

Results

The DLS and TEM analysis showed it was a spherical nanocomposite with 200 nm size and well dispersed . The results of UV-vis and FT-IR confirmed the presence of AMP and AgNPs. The nanocomposite had an excellent biocompatibility at 100 μg/mL. And the AMP@PDA@AgNPs nanocomposite showed superior antimicrobial activity against both Gram-negative (E. coli, P. aeruginosa) and Gram-positive (S. aureus) bacteria than AgNPs or AMP. Importantly, the mRNA expression of biofilm-related genes were decreased under the action of the nanocomposites.

Conclusion

An AMP@PDA@AgNPs nanocomposite with good biocompatibility was successfully prepared. The nanocomposite could destruct bacterial biofilms by inhibiting the expression of biofilm-related genes. The synergistic strategy of AMPs and AgNPs could provide a new perspective for the treatment of bacterial infection.

Nanoparticles as therapeutic options for treating multidrug-resistant bacteria: research progress, challenges, and prospects

Resistance to antimicrobial agents has been alarming in recent years and poses a huge public health threat globally according to the WHO. The increase in morbidity and mortality resulting from microbial infections has been attributed to the emergence of multidrug-resistant microbes. Associated with the increase in multidrug resistance is the lack of new and effective antimicrobials. This has led to global initiatives to identify novel and more effective antimicrobial agents in addition to discovering novel and effective drug delivery and targeting methods. The use of nanoparticles as novel biomaterials to fully achieve this feat is currently gaining global attention. Nanoparticles could become an indispensable viable therapeutic option for treating drug-resistant infections. Of all the nanoparticles, the metals and metal oxide nanoparticles appear to offer the most promise and have attracted tremendous interest from many researchers. Moreover, the use of nanomaterials in photothermal therapy has received considerable attention over the years. This review provides current insight on antimicrobial resistance as well as the mechanisms of nanoparticle antibacterial activity. It offers an in-depth review of all the recent findings in the use of nanomaterials as agents against multi-resistant pathogenic bacteria. Also, nanomaterials that can respond to light stimuli (photothermal therapy) to kill microbes and facilitate enhanced drug delivery and release are discussed. Moreover, the synergistic interactions of nanoparticles with antibiotics and other nanomaterials, microbial adaptation strategies to nanoparticles, current challenges, and future prospects were extensively discussed.

Resistance and Adaptation of Bacteria to Non-Antibiotic Antibacterial Agents: Physical Stressors, Nanoparticles, and Bacteriophages

Antimicrobial resistance is a significant threat to human health worldwide, forcing scientists to explore non-traditional antibacterial agents to support rapid interventions and combat the emergence and spread of drug resistant bacteria. Many new antibiotic-free approaches are being developed while the old ones are being revised, resulting in creating unique solutions that arise at the interface of physics, nanotechnology, and microbiology. Specifically, physical factors (e.g., pressure, temperature, UV light) are increasingly used for industrial sterilization. Nanoparticles (unmodified or in combination with toxic compounds) are also applied to circumvent in vivo drug resistance mechanisms in bacteria. Recently, bacteriophage-based treatments are also gaining momentum due to their high bactericidal activity and specificity. Although the number of novel approaches for tackling the antimicrobial resistance crisis is snowballing, it is still unclear if any proposed solutions would provide a long-term remedy. This review aims to provide a detailed overview of how bacteria acquire resistance against these non-antibiotic factors. We also discuss innate bacterial defense systems and how bacteriophages have evolved to tackle them.

Combined Toxicity of Gas Plasma Treatment and Nanoparticles Exposure in Melanoma Cells In Vitro

Despite continuous advances in therapy, cancer remains a deadly disease. Over the past years, gas plasma technology emerged as a novel tool to target tumors, especially skin. Another promising anticancer approach are nanoparticles. Since combination therapies are becoming increasingly relevant in oncology, both gas plasma treatment and nanoparticle exposure were combined. A series of nanoparticles were investigated in parallel, namely, silica, silver, iron oxide, cerium oxide, titanium oxide, and iron-doped titanium oxide. For gas plasma treatment, the atmospheric pressure argon plasma jet kINPen was utilized. Using three melanoma cell lines, the two murine non-metastatic B16F0 and metastatic B16F10 cells and the human metastatic B-Raf mutant cell line SK-MEL-28, the combined cytotoxicity of both approaches was identified. The combined cytotoxicity of gas plasma treatment and nanoparticle exposure was consistent across all three cell lines for silica, silver, iron oxide, and cerium oxide. In contrast, for titanium oxide and iron-doped titanium oxide, significantly combined cytotoxicity was only observed in B16F10 cells.

Exploring the Toxicity, Lung Distribution, and Cellular Uptake of Rifampicin and Ascorbic Acid-Loaded Alginate Nanoparticles as Therapeutic Treatment of Lung Intracellular Infections

Nanotechnology is a very promising technological tool to combat health problems associated with the loss of effectiveness of currently used antibiotics. Previously, we developed a formulation consisting of a chitosan and tween 80-decorated alginate nanocarrier that encapsulates rifampicin and the antioxidant ascorbic acid (RIF/ASC), intended for the treatment of respiratory intracellular infections. Here, we investigated the effects of RIF/ASC-loaded NPs on the respiratory mucus and the pulmonary surfactant. In addition, we evaluated their cytotoxicity for lung cells in vitro, and their biodistribution on rat lungs in vivo after their intratracheal administration. Findings herein demonstrated that RIF/ASC-loaded NPs display a favorable lung biocompatibility profile and a uniform distribution throughout lung lobules. RIF/ASC-loaded NPs were mainly uptaken by lung macrophages, their primary target. In summary, findings show that our novel designed RIF/ASC NPs could be a suitable system for antibiotic lung administration with promising perspectives for the treatment of pulmonary intracellular infections.

Biofabricated Fatty Acids-Capped Silver Nanoparticles as Potential Antibacterial, Antifungal, Antibiofilm and Anticancer Agents

The current study demonstrates the synthesis of fatty acids (FAs) capped silver nanoparticles (AgNPs) using aqueous poly-herbal drug Liv52 extract (PLE) as a reducing, dispersing and stabilizing agent. The NPs were characterized by various techniques and used to investigate their potent antibacterial, antibiofilm, antifungal and anticancer activities. GC-MS analysis of PLE shows a total of 37 peaks for a variety of bio-actives compounds. Amongst them, n-hexadecanoic acid (21.95%), linoleic acid (20.45%), oleic acid (18.01%) and stearic acid (13.99%) were found predominately and most likely acted as reducing, stabilizing and encapsulation FAs in LIV-AgNPs formation. FTIR analysis of LIV-AgNPs shows some other functional bio-actives like proteins, sugars and alkenes in the soft PLE corona. The zone of inhibition was 10.0 ± 2.2-18.5 ± 1.0 mm, 10.5 ± 2.5-22.5 ± 1.5 mm and 13.7 ± 1.0-16.5 ± 1.2 against P. aeruginosa, S. aureus and C. albicans, respectively. LIV-AgNPs inhibit biofilm formation in a dose-dependent manner i.e., 54.4% ± 3.1%-10.12% ± 2.3% (S. aureus), 72.7% ± 2.2%-23.3% ± 5.2% (P. aeruginosa) and 85.4% ± 3.3%-25.6% ± 2.2% (C. albicans), and SEM analysis of treated planktonic cells and their biofilm biomass validated the fitness of LIV-AgNPs in future nanoantibiotics. In addition, as prepared FAs rich PLE capped AgNPs have also exhibited significant (p < 0.05 *) antiproliferative activity against cultured HCT-116 cells. Overall, this is a very first demonstration on employment of FAs rich PLE for the synthesis of highly dispersible, stable and uniform sized AgNPs and their antibacterial, antifungal, antibiofilm and anticancer efficacy.

Transformation and Cytotoxicity of Surface-Modified Silver Nanoparticles Undergoing Long-Term Aging

Silver nanoparticles (AgNPs) are constituents of many consumer products, but the future of their production depends on ensuring safety. The stability of AgNPs in various physiological solutions and aging in storage may affect the accuracy of predicted nanoparticle toxicity. The goal of this study was to simulate the transformation of AgNPs in different media representatives to the life cycle in the environment and to identify their toxicity to Hepa1c1c7 cells in a long-term aging process. AgNPs coated with citrate, polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), and branched polyethyleneimine (BPEI) were studied. Our results show that the exposure media had a significant impact on the transformation of AgNPs. Citrate-coated AgNPs showed significant aggregation in phosphate-buffered saline. The aging of AgNPs in optimal storage showed that the charge-stabilized particles (citrate) were more unstable, with significant aggregation and shape changes, than sterically stabilized particles (PEG AgNPs, PVP AgNPs). The BPEI AgNPs showed the highest dissolution of AgNPs, which induced significantly increased toxicity to Hepa1c1c7 cells. Overall, our findings showed that storage and media of AgNPs influenced the transformation of AgNPs and that the resulting changes in the AgNPs’ physicochemical properties influenced their toxicity. Our study contributes to the understanding of AgNPs’ transformations under realistic exposure scenarios and increasing the predictability of risk assessments.

Poly-tetrahydropyrimidine Antibacterial Hydrogel with Injectability and Self-Healing Ability for Curing the Purulent Subcutaneous Infection

Infections caused by pathogenic microorganisms have always been the Achilles heel in the clinic. In this work, to overcome this conundrum, we proposed an injectable multifunctional hydrogel material with outstanding antibacterial properties and self-healing properties and no adverse effects on health. The cross-linked hydrogel with three-dimensional (3D) networks was quickly formed via the dynamic Schiff base between amino-modified poly-tetrahydropyrimidine (PTHP-NH₂) and multiple vanillin polymer P(DMA-VA) in 30 s. This hydrogel composite presents effective defense against both Gram-positive and Gram-negative bacteria, especially for the pyogenic Staphylococcus aureus. Moreover, the hydrogel showed almost no hemolysis and cytotoxicity. In vivo investigations indicated that hydrogels effectively killed S. aureus and protected against deterioration of inflammation. Besides, bioimaging of mice demonstrated that the hydrogel could be completely metabolized within 16 h. In a nutshell, given its outstanding antibacterial property and biocompatibility, the novel hydrogel could be an ideal candidate for the subcutaneous infection application.

Boosting nanotoxicity to combat multidrug-resistant bacteria in pathophysiological environments

Nanomaterials are promising novel antibiotics, but often ineffective. We found that nanomaterial-bacteria complex formation occurred with various nanomaterials. The bactericidal activity of NMs strongly depends on their physical binding to (multidrug-resistant) bacteria. Nanomaterials' binding and antibiotic effect was reduced by various pathophysiological biomolecule coronas strongly inhibiting their antibiotic effects. We show from analytical to in vitro to in vivo that nanomaterial-based killing could be restored by acidic pH treatments. Here, complex formation of negatively-charged, plasma corona-covered, nanomaterials with bacteria was electrostatically enhanced by reducing bacteria's negative surface charge. Employing in vivo skin infection models, acidic pH-induced complex formation was critical to counteract Staphylococcus aureus infections by silver nanomaterials. We explain why nano-antibiotics show reduced activity and provide a clinically practical solution.

Bactericidal Antibacterial Mechanism of Plant Synthesized Silver, Gold and Bimetallic Nanoparticles

As the field of nanomedicine develops and tackles the recent surge in antibiotic resistance, there is a need to have an in-depth understanding and a synergistic view of research on the effectiveness of a metal nanoparticle (NP) as an antibacterial agent especially their mechanisms of action. The constant development of bacterial resistance has led scientists to develop novel antibiotic agents. Silver, gold and its bimetallic combination are one of the most promising metal NPs because they show strong antibacterial activity. In this review we discuss the mode of synthesis and the proposed mechanism of biocidal antibacterial activity of metal NPs. These mechanisms include DNA degradation, protein oxidation, generation of reactive oxygen species, lipid peroxidation, ATP depletion, damage of biomolecules and membrane interaction.

Interactions of Gold and Silver Nanoparticles with Bacterial Biofilms: Molecular Interactions behind Inhibition and Resistance

Many bacteria have the capability to form a three-dimensional, strongly adherent network called 'biofilm'. Biofilms provide adherence, resourcing nutrients and offer protection to bacterial cells. They are involved in pathogenesis, disease progression and resistance to almost all classical antibiotics. The need for new antimicrobial therapies has led to exploring applications of gold and silver nanoparticles against bacterial biofilms. These nanoparticles and their respective ions exert antimicrobial action by damaging the biofilm structure, biofilm components and hampering bacterial metabolism via various mechanisms. While exerting the antimicrobial activity, these nanoparticles approach the biofilm, penetrate it, migrate internally and interact with key components of biofilm such as polysaccharides, proteins, nucleic acids and lipids via electrostatic, hydrophobic, hydrogen-bonding, Van der Waals and ionic interactions. Few bacterial biofilms also show resistance to these nanoparticles through similar interactions. The nature of these interactions and overall antimicrobial effect depend on the physicochemical properties of biofilm and nanoparticles. Hence, study of these interactions and participating molecular players is of prime importance, with which one can modulate properties of nanoparticles to get maximal antibacterial effects against a wide spectrum of bacterial pathogens. This article provides a comprehensive review of research specifically directed to understand the molecular interactions of gold and silver nanoparticles with various bacterial biofilms.

Mechanisms of nanotoxicity - biomolecule coronas protect pathological fungi against nanoparticle-based eradication

Whereas nanotoxicity is intensely studied in mammalian systems, our knowledge of desired or unwanted nano-based effects for microbes is still limited. Fungal infections are global socio-economic health and agricultural problems, and current chemical antifungals may induce adverse side-effects in humans and ecosystems. Thus, nanoparticles are discussed as potential novel and sustainable antifungals via the desired nanotoxicity but often fail in practical applications. In our study, we found that nanoparticles' toxicity strongly depends on their binding to fungal spores, including the clinically relevant pathogen Aspergillus fumigatus as well as common plant pests, such as Botrytis cinerea or Penicillum expansum. Employing a selection of the model and antimicrobial nanoparticles, we found that nanoparticle-spore complex formation is influenced by the NM's physicochemical properties, such as size, identified as a key determinant for our silica model particles. Biomolecule coronas acquired in pathophysiologically and ecologically relevant environments, protected fungi against nanoparticle-induced toxicity as shown by employing antimicrobial ZnO, Ag, or CuO nanoparticles as well as dissolution-resistant quantum dots. Mechanistically, dose-dependent corona-mediated resistance was conferred via reducing the physical adsorption of nanoparticles to fungi. The inhibitory effect of biomolecules on nano-based toxicity of Ag NPs was further verified in vivo, using the invertebrate Galleria mellonella as an alternative non-mammalian infection model. We provide the first evidence that biomolecule coronas are not only relevant in mammalian systems but also for nanomaterial designs as future antifungals for human health, biotechnology, and agriculture.

Reactive Oxygen Species-Related Nanoparticle Toxicity in the Biomedical Field

The unique physicochemical characteristics of nanoparticles have recently gained increasing attention in a diverse set of applications, particularly in the biomedical field. However, concerns about the potential toxicological effects of nanoparticles remain, as they have a higher tendency to generate excessive amounts of reactive oxygen species (ROS). Due to the strong oxidation potential, the excess ROS induced by nanoparticles can result in the damage of biomolecules and organelle structures and lead to protein oxidative carbonylation, lipid peroxidation, DNA/RNA breakage, and membrane structure destruction, which further cause necrosis, apoptosis, or even mutagenesis. This review aims to give a summary of the mechanisms and responsible for ROS generation by nanoparticles at the cellular level and provide insights into the mechanics of ROS-mediated biotoxicity. We summarize the literature on nanoparticle toxicity and suggest strategies to optimize nanoparticles for biomedical applications.

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.

Pseudobactins bounded iron nanoparticles for control of an antibiotic-resistant Pseudomonas aeruginosa ryn32

Among 50 strains of Pseudomonas aeruginosa tested for the resistance to antibiotics, strain ryn32 was selected for this study based on its resistance level. It showed complete resistance toward aztreonam and almost complete resistance (96%) against kanamycin. Iron nanoparticles (FeNPs) were then prepared and found with diameters 30-50 nm. The threshold level of FeNPs for pyoverdines (PVDs) production by P. aeruginosa ryn32 was found at 25 μM concentration. PVDs production was optimal with pH 7.5, 35°C, succinate as carbon source, ammonium sulfate as nitrogen source at 60 hr fermentation time. Interestingly, when used the PVDs as conjugates with FeNPs they showed antibacterial action against the producing strain and some other gram-negative bacteria. This suggests that the conjugates enter the bacterial cell via the ferriPVDs uptake pathway, which triggers the accumulation of FeNPs inside the cell, which is crucial on bacterial viability. Growth stimulation with the same concentrations of FeNPs and PVDs in separate treatments supported this view.

Prospects for the Use of New Technologies to Combat Multidrug-Resistant Bacteria

The increasing use of antibiotics is being driven by factors such as the aging of the population, increased occurrence of infections, and greater prevalence of chronic diseases that require antimicrobial treatment. The excessive and unnecessary use of antibiotics in humans has led to the emergence of bacteria resistant to the antibiotics currently available, as well as to the selective development of other microorganisms, hence contributing to the widespread dissemination of resistance genes at the environmental level. Due to this, attempts are being made to develop new techniques to combat resistant bacteria, among them the use of strictly lytic bacteriophage particles, CRISPR-Cas, and nanotechnology. The use of these technologies, alone or in combination, is promising for solving a problem that humanity faces today and that could lead to human extinction: the domination of pathogenic bacteria resistant to artificial drugs. This prospective paper discusses the potential of bacteriophage particles, CRISPR-Cas, and nanotechnology for use in combating human (bacterial) infections.

Molecular Mechanisms of Bacterial Resistance to Metal and Metal Oxide Nanoparticles

The increase in bacterial resistance to one or several antibiotics has become a global health problem. Recently, nanomaterials have become a tool against multidrug-resistant bacteria. The metal and metal oxide nanoparticles are one of the most studied nanomaterials against multidrug-resistant bacteria. Several in vitro studies report that metal nanoparticles have antimicrobial properties against a broad spectrum of bacterial species. However, until recently, the bacterial resistance mechanisms to the bactericidal action of the nanoparticles had not been investigated. Some of the recently reported resistance mechanisms include electrostatic repulsion, ion efflux pumps, expression of extracellular matrices, and the adaptation of biofilms and mutations. The objective of this review is to summarize the recent findings regarding the mechanisms used by bacteria to counteract the antimicrobial effects of nanoparticles.