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

Nanomedicine Fight against Antibacterial Resistance: An Overview of the Recent Pharmaceutical Innovations

Based on the recent reports of World Health Organization, increased antibiotic resistance prevalence among bacteria represents the greatest challenge to human health. In addition, the poor solubility, stability, and side effects that lead to inefficiency of the current antibacterial therapy prompted the researchers to explore new innovative strategies to overcome such resilient microbes. Hence, novel antibiotic delivery systems are in high demand. Nanotechnology has attracted considerable interest due to their favored physicochemical properties, drug targeting efficiency, enhanced uptake, and biodistribution. The present review focuses on the recent applications of organic (liposomes, lipid-based nanoparticles, polymeric micelles, and polymeric nanoparticles), and inorganic (silver, silica, magnetic, zinc oxide (ZnO), cobalt, selenium, and cadmium) nanosystems in the domain of antibacterial delivery. We provide a concise description of the characteristics of each system that render it suitable as an antibacterial delivery agent. We also highlight the recent promising innovations used to overcome antibacterial resistance, including the use of lipid polymer nanoparticles, nonlamellar liquid crystalline nanoparticles, anti-microbial oligonucleotides, smart responsive materials, cationic peptides, and natural compounds. We further discuss the applications of antimicrobial photodynamic therapy, combination drug therapy, nano antibiotic strategy, and phage therapy, and their impact on evading antibacterial resistance. Finally, we report on the formulations that made their way towards clinical application.

Bacterial anti-microbial peptides and nano-sized drug delivery systems: The state of the art toward improved bacteriocins

Antimicrobial peptides (AMP) are molecules consisting of 12-100 amino acids synthesized by certain microbes and released extracellularly to inhibit the growth of other microbes. Among the AMP molecules, bacteriocins are produced by both gram-positive and gram-negative bacterial species and are used to kill or inhibit other prokaryotes in the environment. Due to their broad-spectrum antimicrobial activity, some bacteriocins have the potential of becoming the next generation of antibiotics for use in the crisis of multi antibiotic-resistant bacteria. Recently, bacteriocins have even been used to treat cancer. However, bacteriocins present a few drawbacks, such as sensitivity to proteases, immunogenicity issues, and the development of bacteriocin resistance by pathogenic bacteria. In this regard, nanoscale drug delivery systems (Nano-DDS) have led to the expectation that they will eventually improve the treatment of many diseases by addressing these limitations and improving bacteriocin pharmacokinetics and pharmacodynamics. Thus, combining bacteriocins with nano-DDS may be useful in overcoming these drawbacks and thereby reveal the full potential of bacteriocins. In this review article, we highlight the importance of tailoring nano-DDS to address bacteriocin limitations, the successes and failures of this technology thus far, the challenges that this technology still has to overcome before reaching the market, and future perspectives. Therefore, the purpose of this review is to highlight, categorize, compare and contrast the different nano-DDS described in the literature so far, and compare their effectiveness in order to improve the next generation of bacteriocin nano-sized drug delivery systems (Nano-DDS).

Antibiotic Drug Nanocarriers for Probing of Multidrug ABC Membrane Transporter of Bacillus subtilis

Multidrug membrane transporters can extrude a wide range of substrates, which cause multidrug resistance and ineffective treatment of diseases. In this study, we used three different sized antibiotic drug nanocarriers to study their size-dependent inhibitory effects against Bacillus subtilis. We functionalized 2.4 ± 0.7, 13.0 ± 3.1, and 92.6 ± 4.4 nm silver nanoparticles (Ag NPs) with a monolayer of 11-amino-1-undecanethiol and covalently linked them with antibiotics (ofloxacin, Oflx). The labeling ratios of antibiotics with NPs are 8.6 × 10², 9.4 × 10³, and 6.5 × 10⁵ Oflx molecules per NP, respectively. We designed cell culture medium in which both BmrA and ΔBmrA cells grew and functioned normally while ensuring the stabilities of nanocarriers (nonaggregation). These approaches allow us to quantitatively study the dependence of their inhibitory effect against two isogenic strains of B. subtilis, WT (normal expression of BmrA) and ΔBmrA (deletion of bmrA), upon the NP size, antibiotic dose, and BmrA expression. Our results show that the inhibitory effects of nanocarriers highly depend on NP size and antibiotic dose. The same amount of Oflx on 2.4 ± 0.7, 13.0 ± 3.1, and 92.6 ± 4.4 nm nanocarriers shows the 3× lower, nearly the same, and 10× higher inhibitory effects than that of free Oflx, against both WT and ΔBmrA, respectively. Control experiments of the respective sized AgMUNH₂ NPs (absence of Oflx) show insignificant inhibitory effects toward both strains. Taken together, the results show multiple factors, such as labeling ratios, multivalent effects, and pharmacodynamics (Oflx localization and distribution), which might play the roles in the size-dependent inhibitory effects on the growth of both WT and ΔBmrA strains. Interestingly, the inhibitory effects of nanocarriers are independent of the expression of BmrA, which could be attributed to the higher efflux of nanocarriers by other membrane transporters in both strains.

Topical Therapeutic Efficacy of Ebselen Against Multidrug-Resistant Staphylococcus aureus LT-1 Targeting Thioredoxin Reductase

As a thiol-dependent enzyme, thioredoxin reductase (TrxR) is a promising antibacterial drug target. Ebselen, an organo-selenium with well-characterized toxicology and pharmacology, was recently reported to have potent antibacterial activity against Staphylococcus aureus. In this paper, we demonstrated that ebselen has strong bactericidal activity against multidrug-resistant (MDR) S. aureus based on taking TrxR as a major target and disruption of the redox microenvironment. Further, the topical therapeutic efficacy of ebselen for staphylococcal skin infections was assessed in a rat model. Treatment with ebselen significantly reduced the bacterial load and the expression of pro-inflammatory cytokines tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interleukin-1 beta (IL-1β) in S. aureus skin lesions; further, wound healing and pathological changes were obvious improved in ebselen-treated rats compare to controls. Finally, ebselen was found to sensitize S. aureus to curcumin, which may be due to their synergistic effects in inhibiting bacterial TrxR. Altogether, ebselen is an effective topical antibacterial agent in animal model of MDR S. aureus LT-1 skin infection. This may lay the foundation for further analysis and development of ebselen as an antibacterial agent for topical treatment of MDR staphylococcal infections.

Cytotoxicity, Antioxidant, Antibacterial, and Photocatalytic Activities of ZnO-CdS Powders

In this work, ZnO–CdS composite powders synthesized by a simple chemical precipitation method were thoroughly characterized. The morphological, structural, compositional, photocatalytical, and biological properties of the prepared composites were investigated in comparison with those of the pristine components and correlated with the CdS concentration. ZnO–CdS composites contain flower-like structures, their size being tuned by the CdS amount added during the chemical synthesis. The photocatalytic activity of the composites was analyzed under UV irradiation using powders impregnated with methylene blue; the tests confirming that the presence of CdS along the ZnO in composites can improve the dye discoloration. The biological properties such as antioxidant capacity, antibacterial activity, and cytotoxicity of the ZnO, CdS, and ZnO–CdS composites were evaluated. Thus, the obtained composites presented medium antioxidant effect, biocidal activity against Escherichia coli, and no toxicity (at concentrations less than 0.05 mg/mL for composites with a low CdS amount) for human fibroblast cells. Based on these results, such composites can be used as photocatalytic and/or biocidal additives for photoactive coatings, paints, or epoxy floors, which in their turn can provide a cleaner and healthier environment.

Therapeutic lipid-coated hybrid nanoparticles against bacterial infections

One of the most important health concerns in society is the development of pathogen-causing nosocomial infections. Since the first discovery of antibiotics, bacterial infections have been highly treatable. However, with evolution and the nondiscretionary usage of antibiotics, pathogens have also found new ways to survive the onslaught of antibiotics by surviving intracellularly or through the formation of obstinate biofilms, and through these, the outcomes of regular antibiotic treatments may now be unsatisfactory. Lipid-coated hybrid nanoparticles (LCHNPs) are the next-generation core–shell structured nanodelivery system, where an inorganic or organic core, loaded with antimicrobials, is enveloped by lipid layers. This core–shell structure, with multifarious decorations, not only improves the loading capabilities of therapeutics but also has the potential to improve therapeutic delivery, especially for targeting biofilm-based and intracellular bacterial infections. Although there has been significant interest in the development of LCHNPs, they have yet to be widely exploited for bacterial infections. In this review, we will provide an overview on the latest development of LCHNPs and the various approaches in synthesizing this nano-delivery system. In addition, a discussion on future perspectives of LCHNPs, in combination with other novel anti-bacterial technologies, will be provided towards the end of this review.

Lipid-coated hybrid nanoparticles are next-generation core–shell structured nanodelivery systems, which improve the loading capabilities of therapeutics and can improve therapeutic delivery, especially for targeting biofilm-based and intracellular bacterial infections.

Emerging antibacterial nanomedicine for enhanced antibiotic therapy

This review highlights the different mechanisms of current nano-antibiotic systems for combatting serious antibiotic resistance of bacteria.

MoS2 decorated nanocomposite: Fe2O3@MoS2 inhibits the conjugative transfer of antibiotic resistance genes

Nanomaterials of Al₂O₃ and TiO₂ have been proved to promote the spread of antibiotic resistance genes (ARGs) by horizontal gene transfer. In this work, we found that Fe₂O₃@MoS₂ nanocomposite inhibited the horizontal gene transfer (HGT) by inhibiting the conjugative transfer mediated by RP4-7 plasmid. To discover the mechanism of Fe₂O₃@MoS₂ inhibiting HGT, the bacterial cells were collected under the optimal mating conditions. The collected bacterial cells were used for analyzing the expression levels of genes unique to the plasmid and the bacterial chromosome in the conjugation system by qPCR. The results of genes expression demonstrated that the mechanism of Fe₂O₃@MoS₂ inhibited conjugation by promoting the expression of global regulatory gene (trbA) and inhibiting the expression of conjugative transfer genes involved in mating pair formation (traF, trbB) and DNA replication (trfA). The risk assessment of Fe₂O₃@MoS₂ showed that it had very low toxicity to organisms. The findings of this paper showed that Fe₂O₃@MoS₂, as an inhibitor of horizontal gene transfer, is an environment-friendly material.

Antidiabetic Activity of Gold Nanoparticles Synthesized Using Wedelolactone in RIN-5F Cell Line

We synthesized the gold nanoparticles (AuNPs) using wedelolactone (WDL) and characterized them using UV-visible spectroscopy, fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopic (SEM), transmission electron microscopic (TEM), energy dispersive X-ray diffraction, and atomic force microscopic (AFM) studies. The electronic spectrum exhibited an absorption peak at 535 nm. The FT-IR results proved that WDL was stabilized on the surface of AuNPs by acting as a capping or reducing agent. The crystalline structure was affirmed by XRD pattern and the spherical shape of WDL-AuNPs was evidenced by SEM, TEM, and AFM. The synthesized WDL-AuNPS were evaluated for anti-diabetic activity in pancreatic RIN-5F cell lines. In vitro results showed that WDL-AuNPs did not only improve the insulin secretion affected by di-(2-ethylhexyl) phthalate (DEHP), but also the cell viability in RIN5F cells. WDL-AuNPs treatment modulates the pro-apoptotic proteins and anti-apoptotic proteins expression to prevent the cells undergoing apoptosis in DEHP-exposed RIN-5F cells. The exposure of DEHP causes an increase in ROS production and lipid peroxidation levels. The free radical scavenging and antioxidant properties of WDL-AuNPs increase the deleterious effect caused by DEHP. On the other side, WDL-AuNPs increase mRNA expressions of insulin-signaling proteins in RIN-5F cells. This study concludes that WDL-AuNPs can be successfully used to regulate the expression of Bcl-2 family proteins, reduce lipid peroxidation, and to improve the secretion of antioxidants and insulin through the GLUT2 pathway in RIN-5F cell lines.

Phage-mimicking antibacterial core-shell nanoparticles

The increasing frequency of nosocomial infections caused by antibiotic-resistant microorganisms concurrent with the stagnant discovery of new classes of antibiotics has made the development of new antibacterial agents a critical priority. Our approach is an antibiotic-free strategy drawing inspiration from bacteriophages to combat antibiotic-resistant bacteria. We developed a nanoparticle-based antibacterial system that structurally mimics the protein-turret distribution on the head structure of certain bacteriophages and explored a combination of different materials arranged hierarchically to inhibit bacterial growth and ultimately kill pathogenic bacteria. Here, we describe the synthesis of phage-mimicking antibacterial nanoparticles (ANPs) consisting of silver-coated gold nanospheres distributed randomly on a silica core. The silver-coating was deposited in an anisotropic fashion on the gold nanospheres. Structurally, our nanoparticles mimicked the bacteriophages of the family Microviridae by up to 88%. These phage-mimicking ANPs were tested for bactericidal efficacy against four clinically relevant nosocomial pathogens (Staphylococcus aureus USA300, Pseudomonas aeruginosa FRD1, Enterococcus faecalis, and Corynebacterium striatum) and for biocompatibility with skin cells. Bacterial growth of all four bacteria was inhibited (21% to 90%) as well as delayed (by up to 5 h). The Gram-positive organisms were shown to be more sensitive to the nanoparticle treatment. Importantly, the phage-mimicking ANPs did not show any significant cytotoxic effects against human skin keratinocytes. Our results indicate the potential for phage-mimicking antimicrobial nanoparticles as a highly effective, alternative antibacterial agent, which may be suitable for co-administration with existing available formulations.

Antibacterial Activity of Fusidic Acid and Sodium Fusidate Nanoparticles Incorporated in Pine Oil Nanoemulgel

Purpose

Fusidic acid (FA) and sodium fusidate (SF) have problems in their skin penetration and stability resulting in a reduction in their potency; therefore, the objective of this study was to develop FA and SF nanoemulgels to improve the antibacterial activity of the drugs.

Methods

FA and SF nanoemulgel formulations were prepared by the incorporation of FA and SF nanoemulsions with Carbopol hydrogel. First, the drugs were screened for their solubility in different oils and surfactants to choose the suitable oil and surfactants for the drugs, and then the drug nanoemulsion formulations were prepared by a self-nanoemulsifying technique using Tween 80, Span 20 and pine oil. The drug nanoemulgels were evaluated for their particle size, polydispersity index (PDI), rheological behaviour, drug release and anti-microbial activity.

Results

Based on the solubility test, pine oil was the best solubilising oil for both drugs, Tween 80 and Span 20 showed the highest solubilising ability for both the drugs among the surfactants; therefore, they were chosen as surfactant and co-surfactant, respectively. The optimum self-nanoemulsifying formulations showed a particle size for fusidic acid and Sodium fusidate of 140.58 nm and 151.86 nm respectively, and both showed a low PDI below 0.3. After incorporating both drug SNEDDS formulations with Carbopol at different concentrations, the results of the drugs particle size and PDI showed no significant difference. The zeta potential results for both drugs nanoemulgels showed a negative potential with more than 30 mV. All nanoemulgel formulations showed pseudo-plastic behaviour with the highest release pattern at 0.4% Carbopol. The antibacterial activity of both drug nanoemulgel formulations showed superiority over the market product.

Conclusion

Nanoemulgel is a promising delivery system for FA and SF that helps in improving the stability and antibacterial activities of the drugs.

Nanomaterials as a new opportunity for protecting workers from biological risk

Healthcare-Associated Infections (HAIs) represent a frequent complication for hospitalized patients and more rarely for workers. In recent years, substantial scientific evidence has been reached regarding the role played by the inanimate surfaces, especially those touched in patient-care areas, in the transmission of nosocomial pathogens. Therefore, it is essential to find new collective protective measures to minimize microbial contamination in healthcare facilities, thereby preventing the spread of multi-drug resistant bacteria. We present an overview of the major nano-enabled AntiMicrobial Coatings (AMCs) which may be used as collective protective measures in healthcare setting, discussing also some aspects related to their effectiveness and safety. AMCs may be classified within three groups on base of their mechanism of action: surfaces releasing active compound, contact-killing surfaces and anti-adhesive surfaces. To date, little information is available on the effectiveness of AMCs to reduce the risk of HAIs since the most of studies do not reach conclusive results on their beneficial effects. Moreover, the lack of standard protocols for assessing antimicrobial efficacy and poor data about the interaction between AMCs and disinfectants prevent their placing on the market. Further studies are needed for assessing risks and benefits of AMCs as collective protective measures in healthcare setting.

Recent advances in nanoparticulate biomimetic catalysts for combating bacteria and biofilms

Due to the abuse of antibiotics and the tendency of bacteria to form protective biofilms, the design and development of new efficient agents that can eliminate bacteria and biofilms are still highly desired but remain a great challenge; on the other hand, natural enzymes with unique catalytic characteristics can cause an irreversible damage to the bacteria without inducing drug-resistance in the bacteria. However, the intrinsic drawbacks, such as insufficient stability and high purification cost, of enzymes significantly limit their antimicrobial applications. Therefore, significant research efforts have been devoted towards the development of quality-equivalent or even superior enzyme substitutes with low cost and high stability. In this regard, nanomaterials with extraordinary enzyme-mimetic catalytic activities (termed as nanozymes) are considered as suitable candidates. To date, nanozymes have been proved to be promising materials for combating bacteria and biofilms under mild conditions. In this review, we have summarized the recent progress of nanozymes in this highly active field. The antibacterial mechanisms of nanozymes and the roles of their sizes, morphologies, compositions, surface modifications and microenvironment on their overall performance have been discussed. Moreover, the current challenges and prospects in this research area have been discussed. We believe that nanozymes with unique features and functions can provide a wealth of opportunities via their clinical and industrial applications.

Antimicrobial Peptides as Anti-Infective Agents in Pre-Post-Antibiotic Era?

Resistance to antibiotics is one of the main current threats to human health and every year multi-drug resistant bacteria are infecting millions of people worldwide, with many dying as a result. Ever since their discovery, some 40 years ago, the antimicrobial peptides (AMPs) of innate defense have been hailed as a potential alternative to conventional antibiotics due to their relatively low potential to elicit resistance. Despite continued effort by both academia and start-ups, currently there are still no antibiotics based on AMPs in use. In this study, we discuss what we know and what we do not know about these agents, and what we need to know to successfully translate discovery to application. Understanding the complex mechanics of action of these peptides is the main prerequisite for identifying and/or designing or redesigning novel molecules with potent biological activity. However, other aspects also need to be well elucidated, i.e., the (bio)synthetic processes, physiological and pathological contexts of their activity, and a quantitative understanding of how physico-chemical properties affect activity. Research groups worldwide are using biological, biophysical, and algorithmic techniques to develop models aimed at designing molecules with the necessary blend of antimicrobial potency and low toxicity. Shedding light on some open questions may contribute toward improving this process.

Copper-functionalized nanostructured silica-based systems: Study of the antimicrobial applications and ROS generation against gram positive and gram negative bacteria

A series of copper-functionalized SBA-15 (Santa Barbara Amorphous) materials containing the ligands triethoxysilylpropylmaleamic acid (maleamic) or triethoxy-3-(2-imidazolin-1-yl)propylsilane (imidazoline) have been prepared. The nanostructured silica-based systems SBA-maleamic, SBA-imidazoline, SBA-maleamic-Cu and SBA-imidazoline-Cu were characterized by several methods observing that the functionalization took place mainly inside the pores of the mesoporous system. The antimicrobial behaviour of the synthesized materials against Staphylococcus aureus and Escherichia coli was tested observing a very potent activity of the copper-functionalized systems (minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values for SBA-maleamic-Cu of ca. 31.25 μg/mL, which correspond with ca. 1.13 μg/mL of Cu). A study of the oxidative stress promoted by the synthesized materials showed that the SBA-maleamic-Cu and the SBA-imidazoline-Cu were able to increase the reactive oxygen species (ROS) production in S. aureus by 427% and 373%, respectively, while this increase was slightly lower in E. coli (387 and 324%, respectively). Furthermore, an electrochemical study was carried out in order to determine if these materials interact with lysine or alanine to validate a potential antimicrobial mechanism based on the inhibition of the synthesis of the peptidoglycan of the bacterial wall. Finally, these studies were also performed to determine the potential interaction of the copper-containing materials with glutathione in order to assess if they are able to perturb the metabolism of this tripeptide.

Investigation of the antibacterial activity of Ag-NPs conjugated with a specific antibody against Staphylococcus aureus after photoactivation

AIM

This work reports a new method for the use of lasers for the selective killing of bacteria targeted using light-absorbing Silver nanoparticles (Ag-NPs) conjugated with a specific antibody against the Gram-positive bacterium Staphylococcus aureus (S. aureus).

METHODS AND RESULTS

Ag-NPs were synthesized using a chemical reduction method and characterized with respect to their surface plasmon resonance, surface morphology via transmission electron microscopy (TEM) and dynamic light scattering (DLS). The bacterial surface was targeted using 20 nm Ag-NPs conjugated with an anti-protein A antibody. Labelled bacteria were irradiated with blue visible laser at 2·04 W/cm² . The antibacterial activity of functionalized Ag-NPs was investigated by fluorescence microscopy after irradiation, and morphological changes in S. aureus after laser treatment were assessed using scanning electron microscopy (SEM). The laser-irradiated, functionalized Ag-NPs exhibited significant bactericidal activity, and laser-induced bacterial damage was observed after 10 min of laser irradiation against S. aureus. The fluorescence microscopic analysis results supported that bacterial cell death occurred in the presence of the functionalized Ag-NPs.

CONCLUSIONS

The results of this study suggest that a novel method for the preparation of functionalized nanoparticles has potential as a potent antibacterial agent for the selective killing of resistant disease-causing bacteria.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study shows that Ag-NPs functionalized with a specific antibody, could be used in combination with laser radiation as a novel treatment to target resistant bacterial and fungal pathogens with minimal impact on normal microflora.

Surface Modification by Media Organics Reduces the Bacterio-toxicity of Cupric Oxide Nanoparticle against Escherichia coli

Prevalence of antibiotic-resistant bacteria demands alternatives to antibiotics. Copper-based nanoparticles with a high antibacterial property may be a solution to the problem. It is, therefore, important to understand the mode of antibacterial action of the nanoparticles (NPs). Despite reports on induction of reactive oxygen species (ROS) in bacteria by copper and copper-oxide nanoparticles and involvement of such ROS in cell killing, it is still unclear (a) if surface modification of the nanoparticles by media organics has any role on their antibacterial potency and (b) whether the bactericidal effects of these NPs are 'particle-specific' or 'ion-specific' in nature. We address these issues for cupric oxide nanoparticle (CuO-NP) in this study. Instead of nutrient medium, when E. coli bacterial cells were suspended in saline (0.9% NaCl), CuO-NP had a more anti-bacterial effect, with MBC (minimum bactericidal concentration) value of 6 µg/mL, than in nutrient medium with MBC value of 160 µg/mL. Moreover, the lysine-modified CuO-NP in saline had MBC at 130 µg/mL. Thus, unmodified CuO-NP was more efficient killer than modified one. Our finding further revealed that in saline;CuO-NP had 'particle-specific' antibacterial effect through generation of ROS and consequent oxidative damage by lipid peroxidation, protein oxidation and DNA degradation in cells.

Synthesis, Characterisation and Biological Evaluation of Ampicillin-Chitosan-Polyanion Nanoparticles Produced by Ionic Gelation and Polyelectrolyte Complexation Assisted by High-Intensity Sonication

Recently, one of the promising strategies to fight sensitive and resistant bacteria, and decrease the morbidity and mortality rates due to non-nosocomial infections, is to use antibiotic-loaded nanoparticles. In this study, ampicillin-loaded chitosan-polyanion nanoparticles were produced through the techniques of ionic gelation and polyelectrolyte complexation assisted by high-intensity sonication, using several crosslinking agents, including phytic acid (non-polymeric polyanion), sodium and potassium salts of poly(maleic acid-alt-ethylene) and poly(maleic acid-alt-octadecene) (polymeric polyanions). These nanoparticles were analysed and characterised in terms of particle size, polydispersity index, zeta potential and encapsulation efficiency. The stability of these nanosystems was carried out at temperatures of 4 and 40 °C, and the antimicrobial effect was determined by the broth microdilution method using sensitive and resistant Staphylococcus aureus strains. The results reveal that most of the nanosystems have sizes <220 nm, positive zeta potential values and a monodisperse population, except for the nanoparticles crosslinked with PAM-18 polyanions. The nanometric systems exhibited adequate stability preventing aggregation and revealed a two-fold increase in antimicrobial activity when compared with free ampicillin. This study demonstrates the potential application of synthesised nanoparticles in the field of medicine, especially for treating infections caused by pathogenic S. aureus strains.

Nanoparticles in the Treatment of Infections Caused by Multidrug-Resistant Organisms

Nanotechnology using nanoscale materials is increasingly being utilized for clinical applications, especially as a new paradigm for infectious diseases. Infections caused by multidrug-resistant organisms (MDROs) are emerging as causes of morbidity and mortality worldwide. Antibiotic options for infections caused by MDROs are often limited. These clinical challenges highlight the critical demand for alternative and effective antimicrobial strategies. Nanoparticles (NPs) can penetrate the cell membrane of pathogenic microorganisms and interfere with important molecular pathways, formulating unique antimicrobial mechanisms. In combination with optimal antibiotics, NPs have demonstrated synergy and may aid in limiting the global crisis of emerging bacterial resistance. In this review, we summarized current research on the broad classification of the NPs that have shown in vitro antimicrobial activity against MDROs, including the ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species). The pharmacokinetics and pharmacodynamic characteristics of NPs and bacteria-resistant mechanisms to NPs were also discussed.

Nanocarriers for effective delivery of benznidazole and nifurtimox in the treatment of chagas disease: A review

Neglected tropical diseases (NTDs) constitute a group of infectious diseases prevalent in countries with tropical and subtropical climate that affect the poorest individuals and produce high chronic disability associated with serious problems for the health system and socioeconomic development. Chagas disease or American trypanosomiasis is included on the NTDs list. However, even though this disease affects more than 10 million people, mostly in Latin America, causing the death of over 10,000 people every year, only two drugs are approved for its treatment, benznidazole and nifurtimox. These antiparasitic agents were developed almost half a century ago and present several biopharmaceutical disadvantages such as low aqueous solubility and permeability limiting their bioavailability. In addition, both therapeutic agents are available only as tablets and a liquid pediatric formulation is still lacking. Therefore, novel pharmaceutical strategies to optimize the pharmacotherapy of Chagas disease are urgently required. In this regard, nanotechnological approaches may be a crucial alternative for the delivery of both drugs ensuring an effective pharmacotherapy although the successful bench-to-bedside translation remains a major challenge. The present work reviews in detail the formulation and in-vitro/in-vivo analysis of different nanoformulations of nifurtimox and benznidazole in order to enhance their solubility, dissolution, bioavailability and trypanocidal activity.

Concanavalin A-targeted mesoporous silica nanoparticles for infection treatment

The ability of bacteria to form biofilms hinders any conventional treatment for chronic infections and has serious socio-economic implications. For this purpose, a nanocarrier capable of overcoming the barrier of the mucopolysaccharide matrix of the biofilm and releasing its loaded-antibiotic within this matrix would be desirable. Herein, we developed a new nanosystem based on levofloxacin (LEVO)-loaded mesoporous silica nanoparticles (MSN) decorated with the lectin concanavalin A (ConA). The presence of ConA promotes the internalization of this nanosystem into the biofilm matrix, which increases the antimicrobial efficacy of the antibiotic hosted within the mesopores. This nanodevice is envisioned as a promising alternative to conventional treatments for infection by improving the antimicrobial efficacy and reducing side effects. STATEMENT OF SIGNIFICANCE: The present study is focused on finding an adequate therapeutic solution for the treatment of bone infection using nanocarriers that are capable of overcoming the biofilm barrier by increasing the therapeutic efficacy of the loaded antibiotic. For this purpose, we present a nanoantibiotic that increases the effectiveness of levofloxacin to destroy the biofilm formed by the model bacterium E. coli. This work opens new lines of research in the treatment of chronic infections based on nanomedicines.

One-pot synthesis of a new generation of hybrid bisphosphonate polyoxometalate gold nanoparticles as antibiofilm agents

A reduced polyoxovanadate functionalized with bisphosphonate molecules was synthesized and used to prepare in one step hybrid organic-inorganic polyoxometalate decorated gold nanoparticles. These new composites were shown to strongly inhibit P. aeruginosa and S. epidermidis biofilm growth, with the three components constituting the nanoparticles (Au0 core, vanadium and alendronate) acting synergistically.

Nanomaterials as Promising Alternative in the Infection Treatment

Both the prevalence of antibiotic resistance and the increased biofilm-associated infections are boosting the demand for new advanced and more effective treatment for such infections. In this sense, nanotechnology offers a ground-breaking platform for addressing this challenge. This review shows the current progress in the field of antimicrobial inorganic-based nanomaterials and their activity against bacteria and bacterial biofilm. Herein, nanomaterials preventing the bacteria adhesion and nanomaterials treating the infection once formed are presented through a classification based on their functionality. To fight infection, nanoparticles with inherent antibacterial activity and nanoparticles acting as nanovehicles are described, emphasizing the design of the carrier nanosystems with properties targeting the bacteria and the biofilm.

Gene expression is influenced due to 'nano' and 'ionic' copper in pre-formed Pseudomonas aeruginosa biofilms

Today, researchers across the globe suggest the use of antimicrobial coatings containing copper nanoparticles (CuNPs) complementing the traditional protocols to prevent hospital-acquired infections (HAIs). Since Pseudomonas aeruginosa is one of the commonest opportunistic pathogens, we assessed the anti-biofilm activity of CuNPs in P. aeruginosa MTCC 3541 and compared it with Cu²⁺ (copper sulphate) since the latter continues to be used as an antimicrobial-of-choice in food industries, agriculture and water treatment. In this study, we synthesized and characterized stable poly-acrylic acid (PAA) coated CuNPs with a size of 66-150 nm and zeta potential -13 mV. Pseudomonas aeruginosa MTCC 3541 biofilms were highly resistant to both CuNPs and Cu²⁺ (minimum biofilm inhibitory concentration, MBIC 300 and >600 μg/mL respectively). Scanning electron microscopy revealed alterations in cell morphology upon treatment with CuNPs. A closer analysis of the biofilm-specific gene expression (qRT-PCR) revealed that CuNPs downregulated the genes involved in biofilm matrix formation, motility, efflux, membrane lipoprotein synthesis and DNA replication. Both, CuNPs and Cu²⁺ up regulated copper resistance and biofilm dispersion genes. Copper did not affect the bacterial communication system as evidenced by downregulation of the negative regulator of quorum sensing. The gene expression analysis reveals multiple cellular targets for CuNPs and ionic Cu. The present study highlights the fact that CuNPs affect the membrane functions adversely damaging the cell surface. In pre-formed biofilms, CuNPs were more toxic and displayed distinct responses attributable due to 'nano' and 'ionic' copper. Our findings thus support the use of CuNPs for curbing HAIs.

Montmorillonite-norfloxacin nanocomposite intended for healing of infected wounds

Background: Chronic cutaneous wounds represent a major issue in medical care and are often prone to infections. Purpose: The aim of this study was the design of a clay mineral-drug nanocomposite based on montmorillonite and norfloxacin (NF, antimicrobial drug) as a powder for cutaneous application, to enhance wound healing in infected skin lesions. Methods: The nanocomposite has been prepared by means of an intercalation solution procedure. Adsorption isotherm, solid-state characterization of the nanocomposite, drug loading capacity and its release have been performed. Moreover, cytocompatibility, in vitro fibroblast proliferation and antimicrobial activity against Pseudomonas aeruginosa and Staphylococcus aureus were assessed. Results: The clay drug adsorption isotherm demonstrates that the mechanism of NF intercalation into montmorillonite galleries is the adsorption as one single process, due to the charge-charge interaction between protonated NF and negatively charged montmorillonite edges in the interlayer space. Nanocomposite is biocompatible and it is characterized by antimicrobial activity greater than the free drug: this is due to its nanostructure and controlled drug release properties. Conclusion: Considering the results obtained, NF-montmorillonite nanocomposite seems a promising tool to treat infected skin lesions or skin wounds prone to infection, as chronic ulcers (diabetic foot, venous leg ulcers) and burns.

Susceptibility of microbial cells to the modified PIP2-binding sequence of gelsolin anchored on the surface of magnetic nanoparticles

BACKGROUND

Magnetic nanoparticles (MNPs) are characterized by unique physicochemical and biological properties that allow their employment as highly biocompatible drug carriers. Gelsolin (GSN) is a multifunctional actin-binding protein involved in cytoskeleton remodeling and free circulating actin sequestering. It was reported that a gelsolin derived phosphoinositide binding domain GSN 160-169, (PBP10 peptide) coupled with rhodamine B, exerts strong bactericidal activity.

RESULTS

In this study, we synthesized a new antibacterial and antifungal nanosystem composed of MNPs and a PBP10 peptide attached to the surface. The physicochemical properties of these nanosystems were analyzed by spectroscopy, calorimetry, electron microscopy, and X-ray studies. Using luminescence based techniques and a standard killing assay against representative strains of Gram-positive (Staphylococcus aureus MRSA Xen 30) and Gram-negative (Pseudomonas aeruginosa Xen 5) bacteria and against fungal cells (Candida spp.) we demonstrated that magnetic nanoparticles significantly enhance the effect of PBP10 peptides through a membrane-based mode of action, involving attachment and interaction with cell wall components, disruption of microbial membrane and increased uptake of peptide. Our results also indicate that treatment of both planktonic and biofilm forms of pathogens by PBP10-based nanosystems is more effective than therapy with either of these agents alone.

CONCLUSIONS

The results show that magnetic nanoparticles enhance the antimicrobial activity of the phosphoinositide-binding domain of gelsolin, modulate its mode of action and strengthen the idea of its employment for developing the new treatment methods of infections.

Nanoparticles for Oral Biofilm Treatments

Pathogenic oral biofilms are universal, chronic, and costly. Despite advances in understanding the mechanisms of biofilm formation and persistence, novel and effective treatment options remain scarce. Nanoparticle-mediated eradication of the biofilm matrix and resident bacteria holds great potential. In particular, nanoparticles that target specific microbial and biofilm features utilizing nontoxic materials are well-suited for clinical translation. However, much work remains to characterize the local and systemic effects of therapeutic agents that are topically applied to chronic biofilms, such as those that cause dental caries. In this Perspective, we summarize the pathogenesis of oral biofilms, describe current and future nanoparticle-mediated treatment approaches, and highlight outstanding questions that are paramount to answer for effectively targeting and treating oral biofilms.

Interaction between Copper Oxide Nanoparticles and Amino Acids: Influence on the Antibacterial Activity

The increasing concern about antibiotic-resistance has led to the search for alternative antimicrobial agents. In this effort, different metal oxide nanomaterials are currently under investigation, in order to assess their effectiveness, safety and mode of action. This study focused on CuO nanoparticles (CuO NPs) and was aimed at evaluating how the properties and the antimicrobial activity of these nanomaterials may be affected by the interaction with ligands present in biological and environmental media. Ligands can attach to the surface of particles and/or contribute to their dissolution through ligand-assisted ion release and the formation of complexes with copper ions. Eight natural amino acids (L-Arg, L-Asp, L-Glu, L-Cys, L-Val, L-Leu, L-Phe, L-Tyr) were chosen as model molecules to investigate these interactions and the toxicity of the obtained materials against the Gram-positive bacterium Staphylococcus epidermidis ATCC 35984. A different behavior from pristine CuO NPs was observed, depending on the aminoacidic side chain. These results were supported by physico-chemical and colloidal characterization carried out by means of Fourier-Transform Infrared spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and Thermo-Gravimetric Analysis (TGA), Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and light scattering techniques (Dynamic Light Scattering (DLS), Electrophoretic Light Scattering (ELS) and Centrifugal Separation Analysis (CSA).

Bactericidal and Cytotoxic Properties of Silver Nanoparticles

Silver nanoparticles (AgNPs) can be synthesized from a variety of techniques including physical, chemical and biological routes. They have been widely used as nanomaterials for manufacturing cosmetic and healthcare products, antimicrobial textiles, wound dressings, antitumor drug carriers, etc. due to their excellent antimicrobial properties. Accordingly, AgNPs have gained access into our daily life, and the inevitable human exposure to these nanoparticles has raised concerns about their potential hazards to the environment, health, and safety in recent years. From in vitro cell cultivation tests, AgNPs have been reported to be toxic to several human cell lines including human bronchial epithelial cells, human umbilical vein endothelial cells, red blood cells, human peripheral blood mononuclear cells, immortal human keratinocytes, liver cells, etc. AgNPs induce a dose-, size- and time-dependent cytotoxicity, particularly for those with sizes ≤10 nm. Furthermore, AgNPs can cross the brain blood barrier of mice through the circulation system on the basis of in vivo animal tests. AgNPs tend to accumulate in mice organs such as liver, spleen, kidney and brain following intravenous, intraperitoneal, and intratracheal routes of administration. In this respect, AgNPs are considered a double-edged sword that can eliminate microorganisms but induce cytotoxicity in mammalian cells. This article provides a state-of-the-art review on the synthesis of AgNPs, and their applications in antimicrobial textile fabrics, food packaging films, and wound dressings. Particular attention is paid to the bactericidal activity and cytotoxic effect in mammalian cells.

Recent advances in the treatment of pathogenic infections using antibiotics and nano-drug delivery vehicles

The worldwide misuse of antibiotics and the subsequent rise of multidrug-resistant pathogenic bacteria have prompted a paradigm shift in the established view of antibiotic and bacterial-human relations. The clinical failures of conventional antibiotic therapies are associated with lengthy detection methods, poor penetration at infection sites, disruption of indigenous microflora and high potential for mutational resistance. One of the most promising strategies to improve the efficacy of antibiotics is to complex them with micro or nano delivery materials. Such materials/vehicles can shield antibiotics from enzyme deactivation, increasing the therapeutic effectiveness of the drug. Alternatively, drug-free nanomaterials that do not kill the pathogen but target virulent factors such as adhesins, toxins, or secretory systems can be used to minimize resistance and infection severity. The main objective of this review is to examine the potential of the aforementioned materials in the detection and treatment of antibiotic-resistant pathogenic organisms.

Novel hollow titanium dioxide nanospheres with antimicrobial activity against resistant bacteria

The search for and synthesis of new antimicrobial nanostructures is important to reduce microbial incidence that induces infectious diseases and to aid in the antibiotic resistance crisis, which are two of the most pressing issues in global public health. In this work, novel, hollow, calcined titanium dioxide nanospheres (CSTiO₂) were successfully synthesized for the first time through the combination of electrospinning and atomic layer deposition techniques. Poly(vinylpyrrolidone) (PVP) electrosprayed spherical particles were double-coated with alumina and titanium dioxide, and after a calcination process, hollow nanospheres were obtained with a radius of approximately 345 nm and shell thickness of 17 nm. The structural characterization was performed using electron microscopy, and X-ray diffraction and small-angle X-ray diffraction evidenced an anatase titanium dioxide crystalline structure. Thermogravimetric analysis and Fourier-transform infrared spectroscopy studies demonstrated the absence of polymer residue after the calcination process. The antimicrobial properties of the developed CSTiO₂ hollow nanospheres were evaluated against different bacteria, including resistant E. coli and S. aureus strains, and when compared to commercial TiO₂ nanoparticles, CSTiO₂ nanospheres exhibited superior performance. In addition, the positive effect of UV irradiation on the antimicrobial activity was demonstrated.

Drug Delivery and Bone Infection

Bone infection represents greatest challenge in public health care with serious social and economic implications. The efforts of the scientific community are focused in the development of innovative and advanced biomaterials with anti-infective properties related to their non-fouling, bactericidal and/or antibiofilm capabilities. This chapter aims at thoroughly surveying the different approaches based on silica mesoporous materials (SMMs) for bone infection management. Bacteria repelling surfaces by zwitterionization process, bactericidal effect by implantable devices with antimicrobial local delivery agents and antibiofilm effect by more sophisticated systems based on targeted nanocarriers will be considered.

Electrospun Nanomaterials Implementing Antibacterial Inorganic Nanophases

Electrospinning is a versatile, simple, and low cost process for the controlled production of fibers. In recent years, its application to the development of multifunctional materials has encountered increasing success. In this paper, we briefly overview the general aspects of electrospinning and then we focus on the implementation of inorganic nanoantimicrobials, e.g., nanosized antimicrobial agents in electrospun fibers. The most relevant characteristics sought in nanoantimicrobials supported on (or dispersed into) polymeric materials are concisely discussed as well. The interesting literature issued in the last decade in the field of antimicrobial electrospun nanomaterials is critically described. A classification of the most relevant studies as a function of the different approaches chosen for incorporating nanoantimicrobials in the final material is also provided.

Propolis potentiates the effect of cranberry (Vaccinium macrocarpon) in reducing the motility and the biofilm formation of uropathogenic Escherichia coli

One strategy to prevent urinary tract infections is the use of natural products such as cranberry (Vaccinium macrocarpon) and propolis. The objective of this study was to evaluate the impact of these products alone and combined on the motility and biofilm formation of a collection of representative uropathogenic Escherichia coli (UPEC). Motility was evaluated by the swarming and swimming capacity of the isolates in presence/absence of cranberry ± propolis. Early and late biofilm formation was observed with the Biofilm Ring test (BioFilm Control) and the crystal violet method. Cranberry alone was seen to have a variable effect on motility and biofilm formation unrelated to bacterial characteristics, but a reduced motility and biofilm formation was observed for all the isolates in the presence of cranberry + propolis. These results suggest that cranberry alone doesn’t work on all the E. coli strains and propolis potentiates the effect of cranberry on UPEC, representing a new strategy to prevent recurrent urinary tract infections.