Metal Nanoparticles for Diagnosis and Therapy of Bacterial Infection

A Convenient Colorimetric Bacteria Detection Method Utilizing Chitosan-Coated Magnetic Nanoparticles

An effective novel strategy to detect bacteria is promising because it may improve human health by allowing early diagnosis and timely treatment of bacterial infections. Here, we report a simple, reliable, and economical colorimetric assay using the peroxidase-like activity of chitosan-coated iron oxide magnetic nanoparticles (CS-MNPs). When CS-MNPs are incubated with a sample containing bacterial cells such as the gram-negative Escherichia coli or the gram-positive Staphylococcus aureus, the negatively-charged bacterial membrane interacts with positively-charged chitosan on the surface of CS-MNPs, thus resulting in significant reduction of their peroxidase-like activity presumably by a hindrance in the accessibility of the negatively charged substrate, 2-2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) to the positively-charged CS-MNPs. This simple colorimetric strategy allowed the rapid detection of bacterial cells down to 104 CFU mL-1 by the naked eye and 102 CFU mL-1 by spectrophotometry within 10 min. Based on the results, we anticipate that the CS-MNPs-based assay has great potential for the on-site diagnosis of bacterial infections in facility-limited or point-of-care testing (POCT) environments.

Cell membrane-engineered hybrid soft nanocomposites for biomedical applications

An overview of various cell membrane-engineered hybrid soft nanocomposites for medical applications.

Physiological response to silver toxicity in the extremely halophilic archaeon Halomicrobium mukohataei

Adaptive strategies responsible for heavy metal tolerance were explored in the extremely halophilic archaeon Halomicrobium mukohataei DSM 12286. The tested strain was seemingly able to overcome silver-induced oxidative stress (assessed by malondialdehyde quantification, catalase assay and total antioxidant capacity measurement) mainly through non-enzymatic antioxidants. Energy dispersive spectrometry analysis illustrated the presence of colloidal silver in Hmc. mukohataei cultures exposed to AgNO3. Bright-field and transmission electron microscopy images, as well as dynamic light scattering analysis, demonstrated the presence of intracellular nanoparticles, mostly spherical, within a size range of 20–100 nm. As determined by the zeta potential measurement, the biosynthesized nanoparticles were highly stable, with a negative surface charge. Our research is a first attempt in the systematic study of the oxidative stress and intracellular silver nanoparticle accumulation, generated by exposure to silver ions, in members of Halobacteria class, thus broadening our knowledge on mechanisms supporting heavy metal tolerance of microbial cells living under saline conditions.

Magnetic Particles for Advanced Molecular Diagnosis

Molecular diagnosis is the field that aims to develop nucleic-acid-based analytical methods for biological markers and gene expression assessments by combining laboratory medicine and molecular genetics. As it gradually becomes a clinical reality, molecular diagnosis could benefit from improvements resulting from thorough studies that could enhance the accuracy of these methods. The application of magnetic particles in molecular diagnosis tools has led to tremendous breakthroughs in terms of specificity, sensitivity, and discrimination in bioassays. Therefore, the aim of this review is to highlight the principles involved in the implementation of magnetic particles for sample preparation and targeted analyte isolation, purification, and extraction. Furthermore, the most recent advancements in the area of cancer and infectious disease diagnosis are presented, with an emphasis on screening and early stage detection.

Applications of Iron Oxide-Based Magnetic Nanoparticles in the Diagnosis and Treatment of Bacterial Infections

Diseases caused by bacterial infections, especially drug-resistant bacteria have seriously threatened human health throughout the world. It has been predicted that antimicrobial resistance alone will cause 10 million deaths per year and that early diagnosis and therapy will efficiently decrease the mortality rate caused by bacterial infections. Considering this severity, it is urgent to develop effective methods for the early detection, prevention and treatment of these infections. Until now, numerous efforts based on nanoparticles have been made to detect and kill pathogenic bacteria. Iron oxide-based magnetic nanoparticles (MNPs), as potential platforms for bacteria detection and therapy, have drawn great attention owing to their magnetic property. These MNPs have also been broadly used as bioimaging contrast agents and drug delivery and magnetic hyperthermia agents to diagnose and treat bacterial infections. This review therefore overviews the recent progress on MNPs for bacterial detection and therapy, including bacterial separation and enrichment in vitro, bacterial infection imaging in vivo, and their therapeutic activities on pathogenic bacteria. Furthermore, some bacterial-specific targeting agents, used to selectively target the pathogenic bacteria, are also introduced. In addition, the challenges and future perspective of MNPs for bacterial diagnosis and therapy are given at the end of this review. It is expected that this review will provide a better understanding toward the applications of MNPs in the detection and therapy of bacterial infections.

Self-grafting copper oxide nanoparticles show a strong enhancement of their anti-algal and anti-yeast action

We have developed and tested copper oxide nanoparticles (CuONPs) grafted with (3-glycidyloxypropyl)trimethoxysilane (GLYMO) and coupled with 4-hydroxyphenylboronic acid (4-HPBA), which provides a very strong boost of their action as anti-algal and anti-yeast agents. The boronic acid terminal groups on the surface of the CuONPs/GLYMO/4-HPBA can form reversible covalent bonds with the diol groups of glycoproteins and carbohydrates expressed on the cell surface where they bind and accumulate, which is not based on electrostatic adhesion. Results showed that, the impact of the 4-HPBA grafted CuONPs on microalgae (C. reinhardtii) and yeast (S. cerevisiae) is several hundred percent higher than that of bare CuONPs and CuONPs/GLYMO at the same particle concentration. SEM and TEM imaging revealed that 4-HPBA-functionalized CuONPs nanoparticles can accumulate more on the cell walls than non-functionalized CuONPs. We found a marked increase of the 4-HPBA functionalized CuONPs action on these microorganisms at shorter incubation times compared with the bare CuONPs at the same conditions. We also showed that the anti-algal action of CuONPs/GLYMO/4-HPBA can be controlled by the concentration of glucose in the media and that the effect is reversible as glucose competes with the diol residues on the algal cell walls for the HPBA groups on the CuONPs. Our experiments with human cell lines incubated with CuONPs/GLYMO/4-HPBA indicated a lack of measurable loss of cell viability at particle concentrations which are effective as anti-algal agents. CuONPs/GLYMO/4-HPBA can be used to drastically reduce the overall CuO concentration in anti-algal and anti-yeast formulations while strongly increasing their efficiency.

Strongly Enhanced Antibacterial Action of Copper Oxide Nanoparticles with Boronic Acid Surface Functionality

Copper oxide nanoparticles (CuONPs) have been widely recognized as good antimicrobial agents but are heavily regulated due to environmental concerns of their postuse. In this work, we have developed and tested a novel type of formulation for copper oxide (CuONPs) which have been functionalized with (3-glycidyloxypropyl)trimethoxysilane (GLYMO) to allow further covalent coupling of 4-hydroxyphenylboronic acid (4-HPBA). As the boronic acid (BA) groups on the surface of CuONPs/GLYMO/4-HPBA can form reversible covalent bonds with the diol groups of glycoproteins on the bacterial cell surface, they can strongly bind to the cells walls resulting in a very strong enhancement of their antibacterial action which is not based on electrostatic adhesion. Scanning electron microscopy and transmission electron microscopy imaging revealed that 4-HPBA-functionalized CuO nanoparticles could accumulate more on the cell surface than nonfunctionalized ones. We demonstrate that the CuONPs with boronic acid surface functionality are far superior antibacterial agents compared to bare CuONPs. Our results showed that the antibacterial impact of the 4-HPBA-functionalized CuONPs on Rhodococcus rhodochrous and Escherichia coli is 1 order of magnitude higher than that of bare CuONPs or CuONPs/GLYMO. We also observed a marked increase of the 4-HPBA-functionalized CuONPs antibacterial action on these microorganisms at shorter incubation times compared with the bare CuONPs at the same conditions. Significantly, we show that the cytotoxicity of CuONPs functionalized with 4-HPBA as an outer layer can be controlled by the concentration of glucose in the media, and that the effect is reversible as glucose competes with the sugar residues on the bacterial cell walls for the BA-groups on the CuONPs. Our experiments with human keratinocyte cell line exposure to CuONPs/GLYMO/4-HPBA indicated lack of measurable cytotoxicity at particle concentration which are effective as an antibacterial agent for both R. rhodochrous and E. coli. We envisage that formulations of CuONPs/GLYMO/4-HPBA can be used to drastically reduce the overall CuO concentration in antimicrobial formulations while strongly increasing their efficiency.

Responsive and Synergistic Antibacterial Coatings: Fighting against Bacteria in a Smart and Effective Way

Antibacterial coatings that eliminate initial bacterial attachment and prevent subsequent biofilm formation are essential in a number of applications, especially implanted medical devices. Although various approaches, including bacteria-repelling and bacteria-killing mechanisms, have been developed, none of them have been entirely successful due to their inherent drawbacks. In recent years, antibacterial coatings that are responsive to the bacterial microenvironment, that possess two or more killing mechanisms, or that have triggered-cleaning capability have emerged as promising solutions for bacterial infection and contamination problems. This review focuses on recent progress on three types of such responsive and synergistic antibacterial coatings, including i) self-defensive antibacterial coatings, which can "turn on" biocidal activity in response to a bacteria-containing microenvironment; ii) synergistic antibacterial coatings, which possess two or more killing mechanisms that interact synergistically to reinforce each other; and iii) smart "kill-and-release" antibacterial coatings, which can switch functionality between bacteria killing and bacteria releasing under a proper stimulus. The design principles and potential applications of these coatings are discussed and a brief perspective on remaining challenges and future research directions is presented.

A synergistic antibacterial effect between terbium ions and reduced graphene oxide in a poly(vinyl alcohol)–alginate hydrogel for treating infected chronic wounds

A graphene and rare earth ion-containing hydrogel was developed to effectively promote the healing of infected chronic wounds without using antibiotics.

Mesoporous Silica Materials as Drug Delivery: "The Nightmare" of Bacterial Infection

Mesoporous silica materials (MSM) have a great surface area and a high pore volume, meaning that they consequently have a large loading capacity, and have been demonstrated to be unique candidates for the treatment of different pathologies, including bacterial infection. In this text, we review the multiple ways of action in which MSM can be used to fight bacterial infection, including early detection, drug release, targeting bacteria or biofilm, antifouling surfaces, and adjuvant capacity. This review focus mainly on those that act as a drug delivery system, and therefore that have an essential characteristic, which is their great loading capacity. Since MSM have advantages in all stages of combatting bacterial infection; its prevention, detection and finally in its treatment, we can venture to talk about them as the "nightmare of bacteria".