Ruthenium complexes/polypeptide self-assembled nanoparticles for identification of bacterial infection and targeted antibacterial research

A review of the antimicrobial potential of precious metal derived nanoparticle constructs

The field of nanotechnology is rapidly growing. The promise of pharmacotherapeutics emerging from this vast field has drawn the attention of many researchers. However, with the increase in the prevalence of antibiotic resistant microorganisms, the manifestations of these promises are needed now more than ever. Many have postulated the antimicrobial potential of nanoparticle constructs derived from precious metals/noble metals nanoparticles (NMNPs), such as silver nanoparticles that show activity against multidrug resistant bacteria. In this review we will evaluate the current studies and explore the data to obtain a clear picture of the potential of these particles and the validity of the claims of drug resistant treatments with NMNPs.

Enzyme-Responsive Mesoporous Ruthenium for Combined Chemo-Photothermal Therapy of Drug-Resistant Bacteria

The rapid mutation of drug-resistant bacteria and the serious lag of development of new antibiotics necessitate research on novel antibacterial agents. Nanomaterials with unique size effect and antibacterial mechanism could serve as an alternative for antibiotics, since they showed low possibility to develop drug-resistant bacteria. Here, an enzyme-responsive nanosystem, AA@Ru@HA-MoS₂, with a synergistic chemo-photothermal therapy function is proposed to treat bacterial infections. Mesoporous ruthenium nanoparticles (Ru NPs) were used as nanocarriers, loading prodrug ascorbic acid (AA) and encapsulated by hyaluronic acid (HA). Then, molybdenum disulfide (MoS₂) precoated with ciprofloxacin was used as a catalyst with targeting effect binding to the outer surface. When the nanosystem gathered at the infection site, Hyal secreted by bacteria could degrade the HA capping and trigger the release of AA and then generated hydroxyl radicals (^•OH) in situ by the catalysis of MoS₂. In addition, taking advantage of the good photothermal property of Ru NPs, combined chemo-photothermal antibacterial therapy could be achieved. The nanosystem exhibited potent bactericidal activity against drug-resistant Gram-positive and Gram-negative bacteria. Furthermore, it could break down the biofilm, inhibit the contained bacteria, and prevent the formation of a new biofilm. The in vivo bacterium-infected model also proved accelerated wound healing. The study showed a high potential of AA@Ru@HA-MoS₂ as a novel enzyme-responsive nanosystem for combating drug-resistant bacterial infection.

Recent advances in antibacterial applications of metal nanoparticles (MNPs) and metal nanocomposites (MNCs) against multidrug-resistant (MDR) bacteria

Introduction: In recent years, multidrug resistance (MDR) in bacteria has drastically increased and has posed a great threat to the human health. This problem has generated an urgent need to search alternatives for the treatment of MDR bacteria. It has been proved that metal nanoparticles (MNPs) and metal nanocomposites (MNCs) possess remarkable antimicrobial potential, and hence can be used in alternative therapy. Areas covered: This review is aimed to discuss recent reports on antibacterial activities of MNPs and MNCs against MDR bacteria. Expert opinion: Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae, Serratia marcescens, Streptococcus pneumoniae, and Staphylococcus epidermidis are important pathogenic bacteria which have shown MDR against a wide range of conventional antibiotics. In this context, effects of MNPs and MNCs on these pathogens have demonstrated considerable efficacy. Several mechanisms concerning activity of MNPs and MNCs against pathogenic bacteria which are mainly dependent on type of their precursors and treated bacterium have been investigated. In addition, many studies have been made on antibacterial activities of these nanomaterials with similar and different results.

A New Antimicrobial Agent: Poly (3-hydroxybutyric acid) Oligomer

In this work, it is first reported that the poly (3-hydroxybutyric acid) (PHB) oligomer with a few degrees of polymerization possesses effective antibacterial and antifungal properties. Two preparation methods for the PHB oligomer are described, namely, one-step ring-opening polymerization of β-butyrolactone and extraction from the fermented PHB polymer. An appropriate amount of the synthesized PHB oligomer shows no physiological toxicity to the skin and major organs of mice. Topological application of the synthesized PHB oligomer imparts antimicrobial ability to non-antibacterial fabrics with washing resistance. The synthesized PHB oligomer offers effective sterilization and promotes wound healing in infected nude mice. Most importantly, the PHB oligomer is also reactive to drug-resistant bacteria. These results suggest that the PHB oligomer is not only a great candidate for antimicrobial modification but also a promising one for biomedical applications. Finally, the antimicrobial mechanisms of the PHB oligomer are revealed, and these include disruption of biofilm and the bacterial wall/membrane, leakage of the intracellular content, inhibition of protein activity, and change in the transmembrane potential.

A photothermal-triggered nitric oxide nanogenerator combined with siRNA for precise therapy of osteoarthritis by suppressing macrophage inflammation

Although nitric oxide (NO) can be used to treat osteoarthritis (OA) by inhibiting inflammation, a method for the accurately controlled release of NO in inflammatory cells is still elusive. Herein, photothermal-triggered NO nanogenerators NO-Hb@siRNA@PLGA-PEG (NHsPP) were constructed by assembling photothermal-agents and NO molecules within nanoparticles. In the NHsPP nanoparticles the hemoglobin (Hb) nanoparticles can act as a NO carrier which can absorb near-infrared light at 650 nm (0.5 W cm-2) and convert it into heat to trigger the release of NO. Moreover, after loading Notch1-siRNA, precise treatment can be achieved. Furthermore, using the synergistic effect of photothermal therapy, the NHsPP nanoparticles achieved simultaneous treatment with NO, siRNA and PTT. Through this combination therapy, the therapeutic effect of the NHsPP nanoparticles was significantly enhanced compared to the treatment groups using only NO, siRNA or PTT. This combination therapy inhibits the inflammatory response effectively by reducing the level of pro-inflammatory cytokines and the macrophage response. Subsequently, guided by dual-modal imaging, the NHsPP nanoparticles can not only accumulate effectively in OA mice, but can also reduce the inflammatory response and efficiently prevent cartilage erosion, without causing toxic side effects in the major organs. Therefore, this novel photothermal nanoparticle-based NO-releasing system is expected to be a potential alternative for clinical inflammatory disease therapy and may provide image guidance when combined with other nanotherapy systems.

Pathogen-Specific Polymeric Antimicrobials with Significant Membrane Disruption and Enhanced Photodynamic Damage To Inhibit Highly Opportunistic Bacteria

Highly pathogenic Gram-negative bacteria and their drug resistance are a severe public health threat with high mortality. Gram-negative bacteria are hard to kill due to the complex cell envelopes with low permeability and extra defense mechanisms. It is challenging to treat them with current strategies, mainly including antibiotics, peptides, polymers, and some hybrid materials, which still face the issue of drug resistance, limited antibacterial selectivity, and severe side effects. Together with precise bacteria targeting, synergistic therapeutic modalities, including physical membrane damage and photodynamic eradication, are promising to combat Gram-negative bacteria. Herein, pathogen-specific polymeric antimicrobials were formulated from amphiphilic block copolymers, poly(butyl methacrylate)- b-poly(2-(dimethylamino) ethyl methacrylate- co-eosin)- b-ubiquicidin, PBMA- b-P(DMAEMA- co-EoS)-UBI, in which pathogen-targeting peptide ubiquicidin (UBI) was tethered in the hydrophilic chain terminal, and Eosin-Y was copolymerized in the hydrophilic block. The micelles could selectively adhere to bacteria instead of mammalian cells, inserting into the bacteria membrane to induce physical membrane damage and out-diffusion of intracellular milieu. Furthermore, significant in situ generation of reactive oxygen species was observed upon light irradiation, achieving further photodynamic eradication. Broad-spectrum bacterial inhibition was demonstrated for the polymeric antimicrobials, especially highly opportunistic Gram-negative bacteria, such as Pseudomona aeruginosa ( P. aeruginosa) based on the synergy of physical destruction and photodynamic therapy, without detectable resistance. In vivo P. aeruginosa-infected knife injury model and burn model both proved good potency of bacteria eradication and promoted wound healing, which was comparable with commercial antibiotics, yet no risk of drug resistance. It is promising to hurdle the infection and resistance suffered from highly opportunistic bacteria.

Supramolecular Antibacterial Materials for Combatting Antibiotic Resistance

Antibiotic-resistant bacteria have emerged as a severe threat to human health. As effective antibacterial therapies, supramolecular materials display unprecedented advantages because of the flexible and tunable nature of their noncovalent interactions with biomolecules and the ability to incorporate various active agents in their platforms. Herein, supramolecular antibacterial materials are discussed using a format that focuses on their fundamental active elements and on recent advances including material selection, fabrication methods, structural characterization, and activity performance.

Photosensitizer-Loaded Multifunctional Chitosan Nanoparticles for Simultaneous in Situ Imaging, Highly Efficient Bacterial Biofilm Eradication, and Tumor Ablation

In recent decades, bacterial and viral infections and chronic inflammatory response have emerged as important causes of cancer. Also, infections remain a significant cause of morbidity and mortality in cancer patients. In this work, carboxymethyl chitosan nanoparticles (CMC NPs) were synthesized in a facile and green way and further combined with ammonium methylbenzene blue (MB) as a cross-linking agent as well as a fluorescent molecule and a photosensitizer for self-imaging photodynamic therapy (PDT). The obtained CMC-MB NPs exhibited an apparent pH-responsive release behavior of MB, which was released for a prolonged period in a simulated physiological environment (pH 7.4) for more than 15 days and the time reduced to only 3.5 h in acidic conditions (pH 5.5). When irradiated by a 650 nm laser at 202 mW/cm² for 5 min, the CMC-MB NPs showed efficient bactericidal and biofilm eradication properties as well as suppression of tumor cell growth in a similar acidified microenvironment. Furthermore, in an in vivo rabbit wound bacterial infection model, the rapid sterilization of CMC-MB NPs played a crucial role in bacterial infections, inflammation inhibition, and wound healing. As a PDT treatment against cancer, the CMC-MB NPs also exhibited an efficient antitumor therapeutic effect in a subcutaneous tumor mice model.

Highly fluorescent carbon dots as an efficient nanoprobe for detection of clomifene citrate

Highly fluorescent carbon dots (CDs) were synthesized through facile hydrothermal carbonization and ethylenediamine passivation of an easily available prawn shell precursor. The as-prepared CDs exhibit high water solubility, wavelength-tunable fluorescence with quantum yield up to 68.9%, high photostability and resistance against biomolecules, thus enabling the application as viable fluorescent nanoprobes for detection of guest quenchers. The fluorescence of the CDs can be effectively quenched by clomifene citrate (CC, a common drug for infertility) through static quenching, and therefore can serve as a simple and efficient fluorescent nanoprobe for determination of CC with wide linear range (0.25–10 μg mL⁻¹) and low detection limit (0.2 μg mL⁻¹). The CDs also showed low cytotoxicity, which enables the safe and accurate fluorescent detection of spiked CC in human serum, demonstrating their potential as a credible fluorescent CC nanoprobe in clinical examination.

Highly fluorescent carbon dots (CDs) were synthesized through facile hydrothermal carbonization and ethylenediamine passivation of an easily available prawn shell precursor.

Targeted hexagonal Pd nanosheet combination therapy for rheumatoid arthritis via the photothermal controlled release of MTX

Methotrexate (MTX) is a drug that is used for the clinical treatment of rheumatoid arthritis (RA), a stubborn disease caused by over-immunization.

Emerging vistas in theranostic medicine

Recent years have witnessed a paradigm shift in the focus of healthcare towards development of customized therapies which cater to the unmet needs in a myriad of disease areas such as cancer, infections, cardiovascular diseases, neurodegenerative disorders and inflammatory disorders. The term 'theranostic' refers to such multifunctional systems which combine the features of diagnosis and treatment in a single platform for superior control of the disease. Theranostic systems enable detection of disease, treatment and real time monitoring of the diseased tissue. Theranostic nanocarriers endowed with multiple features of imaging, targeting, and providing on-demand delivery of therapeutic agents have been designed for enhancement of therapeutic outcomes. Fabrication of theranostics involves utilization of materials having distinct properties for imaging, targeting, and programming drug release spatially and temporally. Although the field of theranostics has been widely researched and explored so far for treatment of different types of cancer, there have been considerable efforts in the past few years to extend its scope to other areas such as infections, neurodegenerative disorders and cardiovascular diseases. This review showcases the potential applications of theranostics in disease areas other than cancer. It also highlights the cardinal issues which need to be addressed for successful clinical translation of these theranostic tools.

Progressive release of mesoporous nano-selenium delivery system for the multi-channel synergistic treatment of Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disease with a complex pathogenesis. Controlled release, target ability, and multi-channel synergistic treatment are key factors associated with the success of AD drugs. Herein, we report a novel mesoporous nano-selenium (MSe) release delivery system (MSe-Res/Fc-β-CD/Bor) based on the borneol (Bor) target, β-cyclodextrin nanovalves (Fc-β-CD) with loaded resveratrol (Res). Previous experiments have shown that MSe-Res/Fc-β-CD/Bor first releases Bor by interacting with blood or intracellular esterases, allowing the nanosystem to pass through the blood-brain barrier (BBB). Subsequently, the Fc-β-CD is opened by the redox (H₂O₂) response to the release of Res at the lesion site. We demonstrated that MSe-Res/Fc-β-CD/Bor inhibited aggregation of β-amyloid proteins (Aβ), mitigated oxidative stress, and suppressed tau hyperphosphorylation, while protecting nerve cells and successfully improving memory impairment in APP/PS1 mice. Interestingly, compared with rivastigmine (Riv) positive drugs alone, the MSe/Fc-β-CD/Bor loaded with Riv had a better pharmacokinetic index. These results indicate that MSe-Res/Fc-β-CD/Bor could be a prospective drug for treating AD.

Pretreated Macrophage-Membrane-Coated Gold Nanocages for Precise Drug Delivery for Treatment of Bacterial Infections

Pathogenic bacterial infections and drug resistance make it urgent to develop new antibacterial agents with targeted delivery. Here, a new targeting delivery nanosystem is designed based on the potential interaction between bacterial recognizing receptors on macrophage membranes and distinct pathogen-associated molecular patterns in bacteria. Interestingly, the expression of recognizing receptors on macrophage membranes increases significantly when cultured with specific bacteria. Therefore, by coating pretreated macrophage membrane onto the surface of a gold-silver nanocage (GSNC), the nanosystem targets bacteria more efficiently. Previously, it has been shown that GSNC alone can serve as an effective antibacterial agent owing to its photothermal effect under near-infrared (NIR) laser irradiation. Furthermore, the nanocage can be utilized as a delivery vehicle for antibacterial drugs since the gold-silver nanocage presents a hollow interior and porous wall structure. With significantly improved bacterial adherence, the Sa-M-GSNC nanosystem, developed within this study, is effectively delivered and retained at the infection site both via local or systemic injections; the system also shows greatly prolonged blood circulation time and excellent biocompatibility. The present work described here is the first to utilize bacterial pretreated macrophage membrane receptors in a nanosystem to achieve specific bacterial-targeted delivery, and provides inspiration for future therapy based on this concept.

Self-Assembled Antimicrobial Nanomaterials

Nanotechnology came to stay improving the quality of human life by reducing environmental contamination of earth and water with pathogens. This review discusses how self-assembled antimicrobial nanomaterials can contribute to maintain humans, their water and their environment inside safe boundaries to human life even though some of these nanomaterials display an overt toxicity. At the core of their strategic use, the self-assembled antimicrobial nanomaterials exhibit optimal and biomimetic organization leading to activity at low doses of their toxic components. Antimicrobial bilayer fragments, bilayer-covered or multilayered nanoparticles, functionalized inorganic or organic polymeric materials, coatings and hydrogels disclose their potential for environmental and public health applications in this review.

Nano-Strategies to Fight Multidrug Resistant Bacteria-"A Battle of the Titans"

Infectious diseases remain one of the leading causes of morbidity and mortality worldwide. The WHO and CDC have expressed serious concern regarding the continued increase in the development of multidrug resistance among bacteria. Therefore, the antibiotic resistance crisis is one of the most pressing issues in global public health. Associated with the rise in antibiotic resistance is the lack of new antimicrobials. This has triggered initiatives worldwide to develop novel and more effective antimicrobial compounds as well as to develop novel delivery and targeting strategies. Bacteria have developed many ways by which they become resistant to antimicrobials. Among those are enzyme inactivation, decreased cell permeability, target protection, target overproduction, altered target site/enzyme, increased efflux due to over-expression of efflux pumps, among others. Other more complex phenotypes, such as biofilm formation and quorum sensing do not appear as a result of the exposure of bacteria to antibiotics although, it is known that biofilm formation can be induced by antibiotics. These phenotypes are related to tolerance to antibiotics in bacteria. Different strategies, such as the use of nanostructured materials, are being developed to overcome these and other types of resistance. Nanostructured materials can be used to convey antimicrobials, to assist in the delivery of novel drugs or ultimately, possess antimicrobial activity by themselves. Additionally, nanoparticles (e.g., metallic, organic, carbon nanotubes, etc.) may circumvent drug resistance mechanisms in bacteria and, associated with their antimicrobial potential, inhibit biofilm formation or other important processes. Other strategies, including the combined use of plant-based antimicrobials and nanoparticles to overcome toxicity issues, are also being investigated. Coupling nanoparticles and natural-based antimicrobials (or other repurposed compounds) to inhibit the activity of bacterial efflux pumps; formation of biofilms; interference of quorum sensing; and possibly plasmid curing, are just some of the strategies to combat multidrug resistant bacteria. However, the use of nanoparticles still presents a challenge to therapy and much more research is needed in order to overcome this. In this review, we will summarize the current research on nanoparticles and other nanomaterials and how these are or can be applied in the future to fight multidrug resistant bacteria.