Eradication of drug resistant Staphylococcus aureus by liposomal oleic acids

Biofilm Microenvironment-Sensitive Anti-Virulent and Immunomodulatory Nano-on-Nanodroplets to Combat Refractory Biofilm Infection Through Toxin Neutralization and Phagocytosis

Biofilm-associated wound infection is principally perceived as the bacterial defense mechanism that hinders antibiotic penetration, causes toxin impairment, and suppresses the immunological responses of the host immune system. Several antibiofilm agents have been developed, but the least of these agents can simultaneously cornerstone on the biofilm-associated immunosuppression and bacterial toxin-induced cellular dysfunction. Inspired by the fusogenic property of nanodroplets and immunomodulatory functions of metal nanoparticles, biofilm targeted anti-virulent immunomodulatory cationic nanoparticle shelled nanodroplets (C-AgND) is fabricated to completely disintegrate and eradicate the Staphylococcus aureus (S. aureus) biofilm. The specific binding of C-AgND neutralizes the negatively charged EPS layer, causing their destabilization followed by penetration of the nanoformulation into the biofilm matrix, killing the persister cells. Consequently, C-AgND eliminates the virulence property of the S. aureus biofilm through α-hemolysin neutralization. C-AgND promotes a strong immunomodulatory effect by polarizing macrophages into their M1 phenotype to induce phagocytosis of the disintegrated biofilm-released residual cells, rejuvenating the host's innate immune responses for the complete eradication of the biofilm. Moreover, the ex vivo skin wound infection model illustrates an excellent biofilm eradication efficacy of C-AgND in comparison to the commercial ones, rendering them to be a promising replacement of existing antibiofilm agents in clinical application.

Therapeutic Strategies to Combat Increasing Rates of Multidrug Resistant Pathogens

The emergence of antimicrobic-resistant infectious pathogens and the consequent rising in the incidence and prevalence of demises caused by or associated to infections which are not sensitive to drug treatments is one of today's major global health challenges. Antimicrobial resistance (AMR) can bring to therapeutic failure, infection's persistence and risk of serious illness, in particular in vulnerable populations such as the elderly, patients with neoplastic diseases or the immunocompromised. It is assessed that AMR will induce until 10 million deaths per year by 2050, becoming the leading cause of disease-related deaths. The World Health Organisation (WHO) and the United Nations General Assembly urgently call for new measures to combat the phenomenon. Research and development of new antimicrobial agents has decreased due to market failure. However, promising results are coming from new alternative therapeutic strategies such as monoclonal antibodies, microbiome modulators, nanomaterial-based therapeutics, vaccines, and phages. This narrative review aimed to analyse the benefits and weaknesses of alternative therapeutic strategies to antibiotics which treat multidrug-resistant bacterial infections.

Antibacterial and antibiofilm potentials of vancomycin-loaded niosomal drug delivery system against methicillin-resistant Staphylococcus aureus (MRSA) infections

The threat of methicillin-resistant Staphylococcus aureus (MRSA) is increasing worldwide, making it significantly necessary to discover a novel way of dealing with related infections. The quick spread of MRSA isolates among infected individuals has heightened public health concerns and significantly limited treatment options. Vancomycin (VAN) can be applied to treat severe MRSA infections, and the indiscriminate administration of this antimicrobial agent has caused several concerns in medical settings. Owing to several advantageous characteristics, a niosomal drug delivery system may increase the potential of loaded antimicrobial agents. This work aims to examine the antibacterial and anti-biofilm properties of VAN-niosome against MRSA clinical isolates with emphasis on cytotoxicity and stability studies. Furthermore, we aim to suggest an effective approach against MRSA infections by investigating the inhibitory effect of formulated niosome on the expression of the biofilm-associated gene (icaR). The thin-film hydration approach was used to prepare the niosome (Tween 60, Span 60, and cholesterol), and field emission scanning electron microscopy (FE-SEM), an in vitro drug release, dynamic light scattering (DLS), and entrapment efficiency (EE%) were used to investigate the physicochemical properties. The physical stability of VAN-niosome, including hydrodynamic size, polydispersity index (PDI), and EE%, was analyzed for a 30-day storage time at 4 °C and 25 °C. In addition, the human foreskin fibroblast (HFF) cell line was used to evaluate the cytotoxic effect of synthesized niosome. Moreover, minimum inhibitory and bactericidal concentrations (MICs/MBCs) were applied to assess the antibacterial properties of niosomal VAN formulation. Also, the antibiofilm potential of VAN-niosome was investigated by microtiter plate (MTP) and real-time PCR methods. The FE-SEM result revealed that synthesized VAN-niosome had a spherical morphology. The hydrodynamic size and PDI of VAN-niosome reported by the DLS method were 201.2 nm and 0.301, respectively. Also, the surface zeta charge of the prepared niosome was - 35.4 mV, and the EE% ranged between 58.9 and 62.5%. Moreover, in vitro release study revealed a sustained-release profile for synthesized niosomal formulation. Our study showed that VAN-niosome had acceptable stability during a 30-day storage time. Additionally, the VAN-niosome had stronger antibacterial and anti-biofilm properties against MRSA clinical isolates compared with free VAN. In conclusion, the result of our study demonstrated that niosomal VAN could be promising as a successful drug delivery system due to sustained drug release, negligible toxicity, and high encapsulation capacity. Also, the antibacterial and anti-biofilm studies showed the high capacity of VAN-niosome against MRSA clinical isolates. Furthermore, the results of real-time PCR exhibited that VAN-niosome could be proposed as a powerful strategy against MRSA biofilm via down-regulation of icaR gene expression.

The Effect of Nanoscale Modification of Nisin by Different Milk-Derived Proteins on Its Physicochemical Properties and Antibacterial Activity

Nisin is used as a natural food preservative because of its broad-spectrum antimicrobial activity against Gram-positive bacteria. However, free nisin is susceptible to various factors that reduce its antimicrobial activity. Milk protein, a protein derived from milk, has self-assembly properties and is a good carrier of bioactive substances. In this study, lactoferrin-nisin nanoparticles (L-N), bovine serum albumin-nisin nanoparticles (B-N), and casein-nisin nanoparticles (C-N) were successfully prepared by a self-assembly technique, and then their properties were investigated. The studies revealed that lactoferrin (LF) and nisin formed L-N mainly through hydrophobic interactions and hydrogen bonding, and L-N had the best performance. The small particle size (29.83 ± 2.42 nm), dense reticular structure, and good thermal stability, storage stability, and emulsification of L-N laid a certain foundation for its application in food. Further bacteriostatic studies showed that L-N enhanced the bacteriostatic activity of nisin, with prominent inhibitory properties against Listeria monocytogenes, Staphylococcus aureus, and Bacillus cereus, which mainly disrupted the cell membrane of the bacteria. The above results broaden our understanding of milk protein-nisin nanoparticles, while the excellent antibacterial activity of L-N makes it promising for application as a novel food preservative, which will help to improve the bioavailability of nisin in food systems.

A self-assembling graphene oxide coating for enhanced bactericidal and osteogenic properties of poly-ether-ether-ketone

Poly-ether-ether-ketone (PEEK) is a biomedical plastic that can be used for orthopedic implants, but it offers poor antibacterial properties and bioactivity. In this study, PEEK was sulfonated with the obtained porous structure adsorbing graphene oxide (GO). The surface microstructures and properties of the original PEEK, sulfonated PEEK (SPEEK), and GO-grafted PEEK (GO-SPEEK) were characterized. The results revealed that the GO-SPEEK surface is a 3D porous structure exhibiting superior hydrophilicity to the original PEEK. Although SPEEK was shown to possess antimicrobial properties against both Escherichia coli and Staphylococcus aureus, the bactericidal effect was even more significant for GO-SPEEK, at about 86% and 94%, respectively. In addition, the in vitro simulated-body-fluid immersion and cell experiments indicated that GO-SPEEK had much better hydroxyapatite (HA)-precipitation induction capacity and cell-material interactions (e.g., cell adhesion, proliferation, osteodifferentiation, and extracellular matrix mineralization. The tensile test revealed that the mechanical properties of PEEK were maintained after surface modification, as GO-SPEEK has comparable values of elastic modulus and tensile strength to PEEK. Our investigation sought a method to simultaneously endow PEEK with both good antimicrobial properties and bioactivity as well as mechanical properties, providing a theoretical basis for developing high-performance orthopedic implants in the clinic.

Unleashing the promise of emerging nanomaterials as a sustainable platform to mitigate antimicrobial resistance

The emergence and spread of antibiotic-resistant (AR) bacterial strains and biofilm-associated diseases have heightened concerns about exploring alternative bactericidal methods. The WHO estimates that at least 700 000 deaths yearly are attributable to antimicrobial resistance, and that number could increase to 10 million annual deaths by 2050 if appropriate measures are not taken. Therefore, the increasing threat of AR bacteria and biofilm-related infections has created an urgent demand for scientific research to identify novel antimicrobial therapies. Nanomaterials (NMs) have emerged as a promising alternative due to their unique physicochemical properties, and ongoing research holds great promise for developing effective NMs-based treatments for bacterial and viral infections. This review aims to provide an in-depth analysis of NMs based mechanisms combat bacterial infections, particularly those caused by acquired antibiotic resistance. Furthermore, this review examines NMs design features and attributes that can be optimized to enhance their efficacy as antimicrobial agents. In addition, plant-based NMs have emerged as promising alternatives to traditional antibiotics for treating multidrug-resistant bacterial infections due to their reduced toxicity compared to other NMs. The potential of plant mediated NMs for preventing AR is also discussed. Overall, this review emphasizes the importance of understanding the properties and mechanisms of NMs for the development of effective strategies against antibiotic-resistant bacteria.

A membrane targeted multifunctional cationic nanoparticle conjugated fusogenic nanoemulsion (CFusoN): induced membrane depolarization and lipid solubilization to accelerate the killing of Staphylococcus aureus

Bacterial infections caused by Staphylococcus aureus are one of the growing concerns for human health care management globally. Antibiotic-associated adverse effects and the emergence of bacterial resistant strains necessitate the development of an alternative yet effective approach. Nanoemulsion-based therapy has emerged as a potential therapeutic strategy to combat bacterial infestation. Herein, we designed a cationic metal nanoparticle-conjugated fusogenic nanoemulsion (CFusoN) as a lipid solubilizing nanovesicle for the effective treatment of S. aureus infection with a killing efficiency of 99.999%. The cationic nanoparticle-conjugated nanoemulsion (viz. NECNP) (24.4 ± 2.9 mV) electrostatically bound with the negatively charged bacterial cell membrane (-10.2 ± 3.7 mV) causing alteration of the bacterial surface charge. The fluorometric and flow cytometry studies confirmed the bacterial membrane depolarization and altered cell membrane permeability leading to cell death. The atomic force microscopic studies further demonstrated the damage of the cellular ultrastructure, while the transmission electron microscopic image and membrane lipid solubilization analysis depicted the solubilization of the bacterial membrane lipid bilayer along with the leakage of the intracellular contents. The cell membrane fatty acid analysis revealed that the methyl esters of palmitic acid, stearic acid and octadecadienoic acid isomers were solubilized after the treatment of S. aureus with CFusoN. The bactericidal killing efficiency of CFusoN is proposed to occur through the synergistic efficacy of the targeted attachment of CNP to the bacterial cells along with the lipid solubilization property of NE. Interestingly, NECNP didn't elicit any in vitro hemolytic activity or cytotoxicity against red blood cells (RBCs) and L929 fibroblast cells, respectively, at its bactericidal concentration. Furthermore, a porcine skin wound infection model exhibited the enhanced wound cleansing potency of CFusoN in comparison to the commercially available wound cleansers. The obtained antibacterial activity, biocompatibility and skin wound disinfection efficacy of the NECNP demonstrated the formulation of a cell targeted CFusoN as a promising translatable strategy to combat bacterial infection.

Enhancement of antimicrobial and antibiofilm activities of liposomal fatty acids

Microbial biofilms are protected surface-attached communities of bacteria or fungi with high drug tolerance that typically cause persistent infections. Smart drug carriers are being explored as a promising platform of antimicrobials to address their recalcitrance to antibiotic agents and minimize the side effects of current therapies. In this study, soy lecithin liposomes loaded with lauric acid (LA) and myristoleic acid (MA) were formulated using an emulsification method, and their antibiofilm properties were evaluated. The physio-chemical properties of the most potent liposome were characterized using a zeta sizer, transmission electron microscopy (TEM), fourier transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy. TEM and zeta sizer analysis of the liposome revealed a homogeneous spherical structure with an average size of 159.2 nm and zeta potential of - 5.4 mV. The unilamellar liposomes loaded with LA at 0.1-0.5 µg/mL achieved obvious antibiofilm efficiency against Staphylococcus aureus and Candida albicans and their dual biofilms. Also, LA-loaded liposome formulation efficiently disrupted preformed biofilms of S. aureus and C. albicans. Furthermore, formulated liposomal LA (0.1 µg/mL) exhibited 100-fold increased dual biofilm inhibition compared to LA alone. The single biofilms and dual biofilm formation on polystyrene were reduced as determined by 3D-bright field and scanning electron microscopy. Zeta potential measurements exhibited neutralized surface charge of S. aureus, and the liposomes inhibited hyphae formation in C. albicans. These findings demonstrated that the LA-incorporated liposomes have great potential to become a new, effective, and good antibiofilm agent for treating S. aureus and C. albicans infections.

Importance of microbial amphiphiles: interaction potential of biosurfactants, amyloids, and other exo-polymeric-substances

Microorganisms produce a diverse group of biomolecules having amphipathic nature (amphiphiles). Microbial amphiphiles, including amyloids, bio-surfactants, and other exo-polymeric substances, play a crucial role in various biological processes and have gained significant attention recently. Although diverse in biochemical composition, these amphiphiles have been reported for common microbial traits like biofilm formation and pathogenicity due to their ability to act as surface active agents with active interfacial properties essential for microbes to grow in various niches. This enables microbes to reduce surface tension, emulsification, dispersion, and attachment at the interface. In this report, the ecological importance and biotechnological usage of important amphiphiles have been discussed. The low molecular weight amphiphiles like biosurfactants, siderophores, and peptides showing helical and antimicrobial activities have been extensively reported for their ability to work as quorum-sensing mediators. While high molecular weight amphiphiles make up amyloid fibers, exopolysaccharides, liposomes, or magnetosomes have been shown to have a significant influence in deciding microbial physiology and survival. In this report, we have discussed the functional similarities and biochemical variations of several amphipathic biomolecules produced by microbes, and the present report shows these amphiphiles showing polyphyletic and ecophysiological groups of microorganisms and hence can `be replaced in biotechnological applications depending on the compatibility of the processes.

Impact of local drug delivery and natural agents as new target strategies against periodontitis: new challenges for personalized therapeutic approach

Periodontitis is a persistent inflammation of the soft tissue around the teeth that affects 60% of the population in the globe. The self-maintenance of the inflammatory process can cause periodontal damage from the alveolar bone resorption to tooth loss in order to contrast the effects of periodontitis, the main therapy used is scaling and root planing (SRP). At the same time, studying the physiopathology of periodontitis has shown the possibility of using a local drug delivery system as an adjunctive therapy. Using local drug delivery devices in conjunction with SRP therapy for periodontitis is a potential tool since it increases drug efficacy and minimizes negative effects by managing drug release. This review emphasized how the use of local drug delivery agents and natural agents could be promising adjuvants for the treatment of periodontitis patients affected or not by cardiovascular disease, diabetes, and other system problems. Moreover, the review evidences the current issues and new ideas that can inspire potential later study for both basic research and clinical practice for a tailored approach.

Bio-inspired peptide-conjugated liposomes for enhanced planktonic bacteria killing and biofilm eradication

Developing new antimicrobial agents has become an urgent task to address the increasing prevalence of multidrug-resistant pathogens and the emergence of biofilms. Cationic antimicrobial peptides (AMPs) have been regarded as promising candidates due to their unique non-specific membrane rupture mechanism. However, a series of problems with the peptides hindered their practical application due to their high toxicity and low bioactivity and stability. Here, inspired by broadening the application of cell-penetrating peptides (CPPs), we selected five different sequences of cationic peptides which are considered as both CPPs and AMPs, and developed a biomimetic strategy to construct cationic peptide-conjugated liposomes with the virus-like structure for both enhancements of antibacterial efficacy and biosafety. The correlation between available peptide density/peptide variety and antimicrobial capabilities was evaluated from quantitative perspectives. Computational simulation and experimental investigations assisted to identify the optimal peptide-conjugated liposomes and revealed that the designed system provides high charge density for enhanced anionic bacterial membrane binding capability without compromised cytotoxicity, being capable of enhanced antibacterial efficacy of bacteria/biofilm of clinically important pathogens. The bio-inspired design has shown enhanced therapeutic efficiency of peptides and may promote the development of next-generation antimicrobials.

Nanoparticles-based therapeutics for the management of bacterial infections: A special emphasis on FDA approved products and clinical trials

Microbial resistance has increased in recent decades as a result of the extensive and indiscriminate use of antibiotics. The World Health Organization listed antimicrobial resistance as one of ten major global public health threats in 2021. In particular, six major bacterial pathogens, including third-generation cephalosporin-resistant Escherichia coli, methicillin-resistant Staphylococcus aureus, carbapenem-resistant Acinetobacter baumannii, Klebsiella pneumoniae, Streptococcus pneumoniae, and Pseudomonas aeruginosa, were found to have the highest resistance-related death rates in 2019. To respond to this urgent call, the creation of new pharmaceutical technologies based on nanoscience and drug delivery systems appears to be the promising strategy against microbial resistance in light of recent advancements, particularly the new knowledge of medicinal biology. Nanomaterials are often defined as substances having sizes between 1 and 100 nm. If the material is used on a small scale; its properties significantly change. They come in a variety of sizes and forms to help provide distinguishing characteristics for a wide range of functions. The field of health sciences has demonstrated a strong interest in numerous nanotechnology applications. Therefore, in this review, prospective nanotechnology-based therapeutics for the management of bacterial infections with multiple medication resistance are critically examined. Recent developments in these innovative treatment techniques are described, with an emphasis on preclinical, clinical, and combinatorial approaches.

Exploring Nanotechnology as a Strategy to Circumvent Antimicrobial Resistance in Bone and Joint Infections

Bone and joint infections (BJIs) are difficult to treat, necessitating antimicrobial therapy at high doses for an extended period of time, in some cases different from our local guidelines. As a consequence of the rise in antimicrobial-resistant organisms, drugs that were previously reserved for last-line defense are now being used as first line treatment, and the pill burden and adverse effects on patients are leading to nonadherence, encouraging antimicrobial resistance (AMR) to these last-resort medicines. Nanodrug delivery is the field of pharmaceutical sciences and drug delivery which combines nanotechnology with chemotherapy and/or diagnostics to improve treatment and diagnostic outcomes by targeting specific cells or tissues affected. Delivery systems based on lipids, polymers, metals, and sugars have been used in an attempt to provide a way around AMR. This technology has the potential to improve drug delivery by targeting the site of infection and using the appropriate amount of antibiotics to treat BJIs caused by highly resistant organisms. This Review aims to provide an in-depth examination of various nanodrug delivery systems used to target the causative agents in BJI.

Insights into electrospun pullulan-carboxymethyl chitosan/PEO core-shell nanofibers loaded with nanogels for food antibacterial packaging

Nisin, a natural substance from Lactococcus lactis, displays a promising antibacterial ability against the gram-positive bacteria. However, it is susceptible to the external environment, i.e. temperature, pH, and food composition. In this study, a dual stabilization method, coaxial electrospinning, was applied to protect nisin in food packaging materials and the effect of nisin concentration on the properties of the nanofibers was investigated. The core-shell nanofibers with pullulan as a core layer and carboxymethyl chitosan (CMCS)/polyethylene oxide (PEO) as shell layer were prepared, and then the prepared CMCS-nisin nanogels (CNNGs) using a self-assembly method were loaded into the core layer of the nanofibers as antibacterial agents. The result revealed that the smooth surface can be observed on the nanofibers by microstructure characterization. The CNNGs-loaded nanofibers exhibited enhanced thermal stability and mechanical strength, as well as excellent antibacterial activity. Importantly, the as-formed nanofibers were applied to preserve bass fish and found that the shelf life of bass fish packed by CNNGSs with nisin at a concentration of 8 mg/mL was effectively extended from 9 days to 15 days. Taken together, the CNNGs can be well stabilized with the core-shell nanofibers, thus exerting significantly improved antimicrobial stability and bioactivity. This special structure exerts a great potential for application as food packaging materials to preserve aquatic products.

Controlled Delivery of Vancomycin from Collagen-tethered Peptide Vehicles for the Treatment of Wound Infections

Despite the great promise of antibiotic therapy in wound infections, antibiotic resistance stemming from frequent dosing diminishes drug efficacy and contributes to recurrent infection. To identify improvements in antibiotic therapies, new antibiotic delivery systems that maximize pharmacological activity and minimize side effects are needed. In this study, we developed elastin-like peptide and collagen-like peptide nanovesicles (ECnVs) tethered to collagen-containing matrices to control vancomycin delivery and provide extended antibacterial effects against methicillin-resistant Staphylococcus aureus (MRSA). We observed that ECnVs showed enhanced entrapment efficacy of vancomycin by 3-fold as compared to liposome formulations. Additionally, ECnVs enabled the controlled release of vancomycin at a constant rate with zero-order kinetics, whereas liposomes exhibited first-order release kinetics. Moreover, ECnVs could be retained on both collagen-fibrin (co-gel) matrices and collagen-only matrices, with differential retention on the two biomaterials resulting in different local concentrations of released vancomycin. Overall, the biphasic release profiles of vancomycin from ECnVs/co-gel and ECnVs/collagen more effectively inhibited the growth of MRSA for 18 and 24 h, respectively, even after repeated bacterial inoculation, as compared to matrices containing free vancomycin, which just delayed the growth of MRSA. Thus, this newly developed antibiotic delivery system exhibited distinct advantages for controlled vancomycin delivery and prolonged antibacterial activity relevant to the treatment of wound infections.

Recent nanotechnology-based strategies for interfering with the life cycle of bacterial biofilms

Biofilm formation plays an important role in the resistance development in bacteria to conventional antibiotics. Different properties of the bacterial strains within biofilms compared with their planktonic states and the protective effect of extracellular polymeric substances contribute to the insusceptibility of bacterial cells to conventional antimicrobials. Although great effort has been devoted to developing novel antibiotics or synthetic antibacterial compounds, their efficiency is overshadowed by the growth of drug resistance. Developments in nanotechnology have brought various feasible strategies to combat biofilms by interfering with the biofilm life cycle. In this review, recent nanotechnology-based strategies for interfering with the biofilm life cycle according to the requirements of different stages are summarized. Additionally, the importance of strategies that modulate the bacterial biofilm microenvironment is also illustrated with specific examples. Lastly, we discussed the remaining challenges and future perspectives on nanotechnology-based strategies for the treatment of bacterial infection.

Ahmed E, Battah B, Abd Ellah NH, Zanetti S, Donadu MG. Nanotechnology as a Promising Approach to Combat Multidrug Resistant Bacteria: A Comprehensive Review and Future Perspectives

The wide spread of antibiotic resistance has been alarming in recent years and poses a serious global hazard to public health as it leads to millions of deaths all over the world. The wide spread of resistance and sharing resistance genes between different types of bacteria led to emergence of multidrug resistant (MDR) microorganisms. This problem is exacerbated when microorganisms create biofilms, which can boost bacterial resistance by up to 1000-fold and increase the emergence of MDR infections. The absence of novel and potent antimicrobial compounds is linked to the rise of multidrug resistance. This has sparked international efforts to develop new and improved antimicrobial agents as well as innovative and efficient techniques for antibiotic administration and targeting. There is an evolution in nanotechnology in recent years in treatment and prevention of the biofilm formation and MDR infection. The development of nanomaterial-based therapeutics, which could overcome current pathways linked to acquired drug resistance, is a hopeful strategy for treating difficult-to-treat bacterial infections. Additionally, nanoparticles' distinct size and physical characteristics enable them to target biofilms and treat resistant pathogens. This review highlights the current advances in nanotechnology to combat MDR and biofilm infection. In addition, it provides insight on development and mechanisms of antibiotic resistance, spread of MDR and XDR infection, and development of nanoparticles and mechanisms of their antibacterial activity. Moreover, this review considers the difference between free antibiotics and nanoantibiotics, and the synergistic effect of nanoantibiotics to combat planktonic bacteria, intracellular bacteria and biofilm. Finally, we will discuss the strength and limitations of the application of nanotechnology against bacterial infection and future perspectives.

Application of Nanoliposomes Containing Nisin and Crocin in Milk

Purpose: This study aimed to investigate the effects of nanoliposomes containing crocin and nisin in milk samples as a food model. Therefore, three formulations were prepared and compared, including (1) milk samples containing free nisin and crocin, (2) samples with nanoliposomes containing nisin and crocin, and (3) nisin and crocin-loaded nanoliposomes coated with chitosan. Methods: In order to find the optimum amount of both bioactives within nanoliposomes, analyses of size, polydispersity index (PDI), zeta potential, and encapsulation efficiency were accomplished. Then, the best formulated nanoliposome was evaluated and compared with a solution containing free bioactives and nanoliposomes coated with chitosan using other experiments, including antioxidant and antibacterial activities, viscosity, colorimetric and bacterial growth. Results: The best nanoliposomal system based on the factors of size, PDI, zeta potential, and encapsulation efficiency was related for the nanocarrier with 4 mg crocin, 4.5 mg nisin, and 40 mg lecithin. Based on the results obtained, both nanoliposome (a*=5.41) and chitosancoated nanoliposome (a*=5.09) solutions could significantly (P<0.05) reduce the redness of milk induced by free bioactives (a*=12.32). However, viscosity of milk in chitosan-coated nanoliposome solution was found to be higher (3.42 cP) than other formulations (viscosity of samples with free bioactives was 1.65 cP and viscosity of samples containing nanoliposome was 1.71 cP). In addition, chitosan-coated nanoliposomes could inhibit the growth of Listeria monocytogenes stronger than other samples. Conclusion: Encapsulation of nisin and crocin in nanoliposomes showed promising results for preserving food safety and quality.

Physicochemical and Antioxidant Properties of Nanoliposomes Loaded with Rosemary Oleoresin and Their Oxidative Stability Application in Dried Oysters

Lipid and protein oxidation is a main problem related to the preservation of dried aquatic products. Rosemary oleoresin is widely used as an antioxidant, but its application is limited due to its instability and easy degradation. Nanoliposome encapsulation is a promising and rapidly emerging technology in which antioxidants are incorporated into the liposomes to provide the food high quality, safety and long shelf life. The objectives of this study were to prepare nanoliposome coatings of rosemary oleoresin to enhance the antioxidant stability, and to evaluate their potential application in inhibiting protein and lipid oxidation in dried oysters during storage. The nanoliposomes encapsulating rosemary oleoresin were applied with a thin-film evaporation method, and the optimal amount of encapsulated rosemary oleoresin was chosen based on changes in the dynamic light scattering, Zeta potential, and encapsulation efficiency of the nanoliposomes. The Fourier transform-infrared spectroscopy of rosemary oleoresin nanoliposomes showed no new characteristic peaks formed after rosemary oleoresin encapsulation, and the particle size of rosemary oleoresin nanoliposomes was 100-200 nm in transmission electron microscopy. The differential scanning calorimetry indicated that the nanoliposomes coated with rosemary oleoresin had better thermal stability. Rosemary oleoresin nanoliposomes presented good antioxidant stability, and still maintained 48% DPPH radical-scavenging activity and 45% ABTS radical-scavenging activity after 28 d of storage, which was 3.7 times and 2.8 times higher than that of empty nanoliposomes, respectively. Compared with the control, the dried oysters coated with rosemary oleoresin nanoliposomes showed significantly lower values of carbonyl, sulfhydryl content, thiobarbituric acid reactive substances, Peroxide value, and 4-Hydroxynonenal contents during 28 d of storage. The results provide a theoretical basis for developing an efficient and long-term antioxidant approach.

Nanoarchitectonics-based model membrane platforms for probing membrane-disruptive interactions of odd-chain antimicrobial lipids

The use of nanoscience tools to investigate how antimicrobial lipids disrupt phospholipid membranes has greatly advanced molecular-level biophysical understanding and opened the door to new application possibilities. Until now, relevant studies have focused on even-chain antimicrobial lipids while there remains an outstanding need to investigate the membrane-disruptive properties of odd-chain antimicrobial lipids that are known to be highly biologically active. Herein, using the quartz crystal microbalance-dissipation (QCM-D) and electrochemical impedance spectroscopy (EIS) techniques, we investigated how an 11-carbon, saturated fatty acid and its corresponding monoglyceride-termed undecanoic acid and monoundecanoin, respectively-disrupt membrane-mimicking phospholipid bilayers with different nanoarchitectures. QCM-D tracking revealed that undecanoic acid and monoundecanoin caused membrane tubulation and budding from supported lipid bilayers, respectively, and were only active above their experimentally determined critical micelle concentration (CMC) values. Monoundecanoin was more potent due to a lower CMC and electrochemical impedance spectroscopy (EIS) characterization demonstrated that monoundecanoin caused irreversible membrane disruption of a tethered lipid bilayer platform at sufficiently high compound concentrations, whereas undecanoic acid only induced transient membrane disruption. This integrated biophysical approach also led us to identify that the tested 11-carbon antimicrobial lipids cause more extensive membrane disruption than their respective 12-carbon analogues at 2 × CMC, which suggests that they could be promising molecular components within next-generation antimicrobial nanomedicine strategies.

Recent Advances in the Development of Lipid-, Metal-, Carbon-, and Polymer-Based Nanomaterials for Antibacterial Applications

Infections caused by multidrug-resistant (MDR) bacteria are becoming a serious threat to public health worldwide. With an ever-reducing pipeline of last-resort drugs further complicating the current dire situation arising due to antibiotic resistance, there has never been a greater urgency to attempt to discover potential new antibiotics. The use of nanotechnology, encompassing a broad range of organic and inorganic nanomaterials, offers promising solutions. Organic nanomaterials, including lipid-, polymer-, and carbon-based nanomaterials, have inherent antibacterial activity or can act as nanocarriers in delivering antibacterial agents. Nanocarriers, owing to the protection and enhanced bioavailability of the encapsulated drugs, have the ability to enable an increased concentration of a drug to be delivered to an infected site and reduce the associated toxicity elsewhere. On the other hand, inorganic metal-based nanomaterials exhibit multivalent antibacterial mechanisms that combat MDR bacteria effectively and reduce the occurrence of bacterial resistance. These nanomaterials have great potential for the prevention and treatment of MDR bacterial infection. Recent advances in the field of nanotechnology are enabling researchers to utilize nanomaterial building blocks in intriguing ways to create multi-functional nanocomposite materials. These nanocomposite materials, formed by lipid-, polymer-, carbon-, and metal-based nanomaterial building blocks, have opened a new avenue for researchers due to the unprecedented physiochemical properties and enhanced antibacterial activities being observed when compared to their mono-constituent parts. This review covers the latest advances of nanotechnologies used in the design and development of nano- and nanocomposite materials to fight MDR bacteria with different purposes. Our aim is to discuss and summarize these recently established nanomaterials and the respective nanocomposites, their current application, and challenges for use in applications treating MDR bacteria. In addition, we discuss the prospects for antimicrobial nanomaterials and look forward to further develop these materials, emphasizing their potential for clinical translation.

Valorization of Soy Lecithin by Enzyme Cascade Reactions Including a Phospholipase A2, a Fatty Acid Double-Bond Hydratase, and/or a Photoactivated Decarboxylase

A huge amount of phospholipids or lecithin is produced as a byproduct in the vegetable oil industry. However, most are just used as a feed additive. This study has focused on enzymatic valorization of lecithin. This was exploited by enzymatic transformation of soy lecithin into lysolecithin liposomes, including functional free fatty acids, hydroxy fatty acids, hydrocarbons, or secondary fatty alcohols. One of the representative examples was the preparation of lysolecithin liposomes containing secondary fatty alcohols [e.g., 9-Hydroxyheptadec-11-ene (9) and 9-heptadecanol (10)] by using a phospholipase A2 from Streptomyces violaceoruber, a fatty acid double-bond hydratase from Stenotrophomonas maltophilia, and a photoactivated decarboxylase from Chlorella variabilis NC64A. The engineered liposomes turned out to range ca. 144 nm in diameter by dynamic light scattering analysis. Thereby, this study will contribute to application of functional fatty acids and their derivatives as well as valorization of lecithin for the food and cosmetic industries.

Nanomaterial-Based Zinc Ion Interference Therapy to Combat Bacterial Infections

Pathogenic bacterial infections are the second highest cause of death worldwide and bring severe challenges to public healthcare. Antibiotic resistance makes it urgent to explore new antibacterial therapy. As an essential metal element in both humans and bacteria, zinc ions have various physiological and biochemical functions. They can stabilize the folded conformation of metalloproteins and participate in critical biochemical reactions, including DNA replication, transcription, translation, and signal transduction. Therefore, zinc deficiency would impair bacterial activity and inhibit the growth of bacteria. Interestingly, excess zinc ions also could cause oxidative stress to damage DNA, proteins, and lipids by inhibiting the function of respiratory enzymes to promote the formation of free radicals. Such dual characteristics endow zinc ions with unparalleled advantages in the direction of antibacterial therapy. Based on the fascinating features of zinc ions, nanomaterial-based zinc ion interference therapy emerges relying on the outstanding benefits of nanomaterials. Zinc ion interference therapy is divided into two classes: zinc overloading and zinc deprivation. In this review, we summarized the recent innovative zinc ion interference strategy for the treatment of bacterial infections and focused on analyzing the antibacterial mechanism of zinc overloading and zinc deprivation. Finally, we discuss the current limitations of zinc ion interference antibacterial therapy and put forward problems of clinical translation for zinc ion interference antibacterial therapy.

Linolenic Acid-Metronidazole: a Compound Relieving Drug Resistance and Inhibiting Helicobacter pylori

Metronidazole (Met) is the first choice for treating Helicobacter pylori (Hp). However, Hp is easy to resistant, making Met unable to be widely used. How to overcome Hp’s Met resistance is still an issue. In this study, Met was used as the primary raw material with linolenic acid to prepare a novel compound-linolenic acid-metronidazole (Lla-Met). The MIC, minimum bactericidal concentration (MBC), colonization amount of Hp in gastric mucosa, etc., were evaluated, respectively. Lla-Met was successfully prepared by the detection of nuclear magnetic resonance, etc., and its MIC and MBC to Hp were 2~4 μg/mL, 8~16 μg/mL. Moreover, in vivo experiments, Lla-Met significantly reduced the colonization of drug-resistant Hp in gastric mucosa. In the toxicity test, Lla-Met inhibited rate to GES-1 and BGC823 cells were 15% at 128 μg/mL; the mice were administered 10 times treatment Lla-Met treatment (240 mg/kg), have no difference significant injuries were found in their stomach, liver, spleen, kidney, and weight. In addition, Hp G27 continued for 18 days in vitro with sub-Lla-Met concentration, G27 did not show drug resistance to Lla-Met; Lla-Met did not exert an effect on non-Hp species with 128 μg/mL; Compared with a neutral environment, when the acid concentration is 3.0, Lla-Met is not decomposed and has better stability. Conclusion: Lla-Met, a newly prepared compound, has relatively well antibacterial of Met-resistant and sensitive Hp, with a capability of overcoming the metronidazole resistance of Hp.

Hesperidin-, Curcumin-, and Amphotericin B- Based Nano-Formulations as Potential Antibacterials

To combat the public health threat posed by multiple-drug-resistant (MDR) pathogens, new drugs with novel chemistry and modes of action are needed. In this study, several drugs including Hesperidin (HES), curcumin (CUR), and Amphotericin B (AmpB) drug-nanoparticle formulations were tested for antibacterial strength against MDR Gram-positive bacteria, including Bacillus cereus, Streptococcus pyogenes, Methicillin-resistant Staphylococcus aureus (MRSA), and Streptococcus pneumoniae, and Gram-negative bacteria, including Escherichia coli K1, Pseudomonas aeruginosa, Salmonella enterica, and Serratia marcescens. Nanoparticles were synthesized and subjected to Atomic force microscopy, Fourier transform-infrared spectroscopy, and Zetasizer for their detailed characterization. Antibacterial assays were performed to determine their bactericidal efficacy. Lactate dehydrogenase (LDH) assays were carried out to measure drugs' and drug-nanoparticles' cytotoxic effects on human cells. Spherical NPs ranging from 153 to 300 nm were successfully synthesized. Results from antibacterial assays revealed that drugs and drug-nanoparticle formulations exerted bactericidal activity against MDR bacteria. Hesperidin alone failed to exhibit antibacterial effects but, upon conjugation with cinnamic-acid-based magnetic nanoparticle, exerted significant bactericidal activity against both the Gram-positive and Gram-negative isolates. AmpB-LBA-MNPs produced consistent, potent antibacterial efficacy (100% kill) against all Gram-positive bacteria. AmpB-LBA-MNPs showed strong antibacterial activity against Gram-negative bacteria. Intriguingly, all the drugs and their conjugated counterpart except AmpB showed minimal cytotoxicity against human cells. In summary, these innovative nanoparticle formulations have the potential to be utilized as therapeutic agents against infections caused by MDR bacteria and represent a significant advancement in our effort to counter MDR bacterial infections.

pH-Responsive Antimicrobial Peptide with Selective Killing Activity for Bacterial Abscess Therapy

The unusual acidic pH of the abscess milieu is an adverse factor that decreases the therapeutic efficacy of traditional antibiotics. Moreover, avoiding both the undesired killing of commensal bacteria and the development of drug resistance remains difficult during abscess therapy. Hence, we synthesized a series of pH-responsive antimicrobial peptides equipped with efficient bacterial killing activity at pH 6.5 and inactivity at pH 7.4. Among the peptides, F5 exhibited outstanding pH-responsive antimicrobial activity and low toxicity. Fluorescence spectroscopy and electron microscopy illustrated that F5 killed bacteria via a membrane-disruptive mechanism at acidic pH values. Mouse cutaneous abscesses revealed that F5 was equipped with excellent therapeutic ability to reduce the bacterial load and cytokines without causing skin toxicity. In summary, this study reveals a strategy for selectively killing bacteria under the pathologic conditions of abscess sites while avoiding the elimination of commensal bacteria under normal physiological pH levels.

Nanoparticle, a promising therapeutic strategy for the treatment of infective endocarditis

Infective endocarditis (IE) has been recognized as a biofilm-related disease caused by pathogenic microorganisms, such as bacteria and fungi that invade and damage the heart valves and endocardium. There are many difficulties and challenges in the antimicrobial treatment of IE, including multi-drug resistant pathogens, large dose of drug administration with following side effects, and poor prognosis. For the past few years, the development of nanotechnology has promoted the use of nanoparticles as antimicrobial nano-pharmaceuticals or novel drug delivery systems (NDDS) in antimicrobial therapy for chronic infections and biofilm-related infectious disease as these molecules exhibit several advantages. Therefore, nanoparticles have a potential role to play in solving problems in the treatment of IE, including improving antimicrobial activity, increasing drug bioavailability, minimizing frequency of drug administration, and preventing side effects. In this article, we review the latest advances in nanoparticles against drug-resistant bacteria in biofilm and recommends nanoparticles as an alternative strategy to the antibiotic treatment of IE.

Nanoemulsion delivery systems for enhanced efficacy of antimicrobials and essential oils

The ever-growing threat of new and existing infectious diseases in combination with antimicrobial resistance requires the need for innovative and effective forms of drug delivery. Optimal drug delivery systems for existing and newly developed antimicrobials can enhance drug bioavailability, enable site-specific drug targeting, and overcome current limitations of drug formulations such as short elimination half-lives, poor drug solubility, and undesirable side effects. Nanoemulsions (NE) consist of nanometer-sized droplets stabilized by emulsifiers and are typically more stable and permeable due to their smaller particle sizes and higher surface area compared to conventional emulsions. NE have been identified as a promising means of antimicrobial delivery due to their intrinsic antimicrobial properties, ability to increase drug solubility, stability, bioavailability, organ and cellular targeting potentials, capability of targeting biofilms, and potential to overcome antimicrobial resistance. Herein, we discuss non-drug loaded essential oil-based NE that can confer antimicrobial actions through predominantly physical or biochemical mechanisms without drug payloads. We also describe drug-loaded NE for enhanced antimicrobial efficacy by augmenting the potency of existing antimicrobials. We highlight the versatility of NE to be administered through multiple different routes (oral, parenteral, dermal, transdermal, pulmonary, nasal, ocular, and rectal). We summarize recent advances in the clinical translation of antimicrobial NE and shed light on future development of effective antimicrobial therapy to combat infectious diseases.

Antibacterial Efficacy of Liposomal Formulations Containing Tobramycin and N-Acetylcysteine against Tobramycin-Resistant Escherichia coli, Klebsiella pneumoniae, and Acinetobacter baumannii

The antibacterial activity and biofilm reduction capability of liposome formulations encapsulating tobramycin (TL), and Tobramycin-N-acetylcysteine (TNL) were tested against tobramycin-resistant strains of E. coli, K. pneumoniae and A. baumannii in the presence of several resistant genes. All antibacterial activity were assessed against tobramycin-resistant bacterial clinical isolate strains, which were fully characterized by whole-genome sequencing (WGS). All isolates acquired one or more of AMEs genes, efflux pump genes, OMP genes, and biofilm formation genes. TL formulation inhibited the growth of EC_089 and KP_002 isolates from 64 mg/L and 1024 mg/L to 8 mg/L. TNL formulation reduced the MIC of the same isolates to 16 mg/L. TNL formulation was the only effective formulation against all A. baumannii strains compared with TL and conventional tobramycin (in the plektonic environment). Biofilm reduction was significantly observed when TL and TNL formulations were used against E. coli and K. pneumoniae strains. TNL formulation reduced biofilm formation at a low concentration of 16 mg/L compared with TL and conventional tobramycin. In conclusion, TL and TNL formulations particularly need to be tested on animal models, where they may pave the way to considering drug delivery for the treatment of serious infectious diseases.

Uptake Dynamics of Cubosome Nanocarriers at Bacterial Surfaces and the Routes for Cargo Internalization

Antibiotic-resistant bacteria pose a significant threat to humanity. Gram-negative strains have demonstrated resistance to last resort antibiotics, partially due to their outer membrane, which hinders transport of antimicrobials into the bacterium. Nanocarrier (NC)-mediated drug delivery is one proposed strategy for combating this emerging issue. Here, the uptake of self-assembled lipid nanocarriers of cubic symmetry (cubosomes) into bacteria revealed fundamental differences in the uptake mechanism between Gram-positive and Gram-negative bacteria. For Gram-positive bacteria, the NCs adhere to the outer peptidoglycan layers and slowly internalize to the bacterium. For Gram-negative bacteria, the NCs interact in two stages, fusion with the outer lipid membrane and then diffusion through the inner wall. The self-assembled nature of the cubosomes imparts a unique ability to transfer payloads via membrane fusion. Remarkably, the fusion uptake mechanism allowed rapid NC internalization by the Gram-negative bacteria, overcoming the outer membrane responsible for their heightened resilience. Here this is demonstrated by the marked reduction in the minimal inhibition concentration required for antibiotics against a pathogenic strain of Gram-negative bacteria, Escherichia coli. These results provide mechanistic insight for the development of lipid NCs as a new tool to combat bacteria.

Liposomal delivery systems and their applications against Staphylococcus aureus and Methicillin-resistant Staphylococcus aureus

Liposomal delivery systems have been widely explored for targeting superbugs such as S. aureus and MRSA, overcoming antimicrobial resistance associated with conventional dosage forms. They have the significant advantage of delivering hydrophilic and lipophilic antimicrobial agents, either singularly as monotherapy or in combination as combination therapy, due to their bilayers with action-site-specificity, resulting in improved targeting compared to conventional dosage forms. Herein, we present an extensive and critical review of the different liposomal delivery systems employed in the past two decades for the delivery of both antibiotics of different classes and non-antibiotic antibacterial agents, as monotherapy and combination therapy to eradicate infections caused by S. aureus and MRSA. The review also identifies future research and strategies potentiating the applications of liposomal delivery systems against S. aureus and MRSA. This review confirms the potential application of liposomal delivery systems for effective delivery and specific targeting of S. aureus and MRSA infections.

Virus-inspired surface-nanoengineered antimicrobial liposome: A potential system to simultaneously achieve high activity and selectivity

Enveloped viruses such as SARS-CoV-2 frequently have a highly infectious nature and are considered effective natural delivery systems exhibiting high efficiency and specificity. Since simultaneously enhancing the activity and selectivity of lipopeptides is a seemingly unsolvable problem for conventional chemistry and pharmaceutical approaches, we present a biomimetic strategy to construct lipopeptide-based mimics of viral architectures and infections to enhance their antimicrobial efficacy while avoiding side effects. Herein, a surface-nanoengineered antimicrobial liposome (SNAL) is developed with the morphological features of enveloped viruses, including a moderate size range, lipid-based membrane structure, and highly lipopeptide-enriched bilayer surface. The SNAL possesses virus-like infection to bacterial cells, which can mediate high-efficiency and high-selectivity bacteria binding, rapidly attack and invade bacteria via plasma membrane fusion pathway, and induce a local "burst" release of lipopeptide to produce irreversible damage of cell membrane. Remarkably, viral mimics are effective against multiple pathogens with low minimum inhibitory concentrations (1.6-6.3 μg mL-1), high bactericidal efficiency of >99% within 2 h, >10-fold enhanced selectivity over free lipopeptide, 99.8% reduction in skin MRSA load after a single treatment, and negligible toxicity. This bioinspired design has significant potential to enhance the therapeutic efficacy of lipopeptides and may create new opportunities for designing next-generation antimicrobials.

Lipid Nanoparticle Technology for Delivering Biologically Active Fatty Acids and Monoglycerides

There is enormous interest in utilizing biologically active fatty acids and monoglycerides to treat phospholipid membrane-related medical diseases, especially with the global health importance of membrane-enveloped viruses and bacteria. However, it is difficult to practically deliver lipophilic fatty acids and monoglycerides for therapeutic applications, which has led to the emergence of lipid nanoparticle platforms that support molecular encapsulation and functional presentation. Herein, we introduce various classes of lipid nanoparticle technology and critically examine the latest progress in utilizing lipid nanoparticles to deliver fatty acids and monoglycerides in order to treat medical diseases related to infectious pathogens, cancer, and inflammation. Particular emphasis is placed on understanding how nanoparticle structure is related to biological function in terms of mechanism, potency, selectivity, and targeting. We also discuss translational opportunities and regulatory needs for utilizing lipid nanoparticles to deliver fatty acids and monoglycerides, including unmet clinical opportunities.

Enhanced Antibacterial Activity of Echinacea angustifolia Extract against Multidrug-Resistant Klebsiella pneumoniae through Niosome Encapsulation

With the increased occurrence of antibiotic-resistant bacteria, alternatives to classical antibiotics are urgently needed for treatment of various infectious diseases. Medicinal plant extracts are among the promising candidates due to their bioactive components. The aim of this study was to prepare niosome-encapsulated Echinacea angustifolia extract and study its efficacy against multidrug-resistant Klebsiella pneumoniae strains. Encapsulation was first optimized by Design of Experiments, followed by the empirical study. The obtained niosomes were further characterized for the size and morphology using dynamic light scattering (DLS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Spherical niosomes had a diameter of 142.3 ± 5.1 nm, as measured by DLS. The entrapment efficiency (EE%) of E. angustifolia extract reached up to 77.1% ± 0.3%. The prepared niosomes showed a controlled drug release within the tested 72 h and a storage stability of at least 2 months at both 4 and 25 °C. The encapsulated E. angustifolia displayed up to 16-fold higher antibacterial activity against multidrug-resistant K.pneumoniae strains, compared to the free extract. Additionally, the niosome exhibited negligible cytotoxicity against human foreskin fibroblasts. We anticipate that the results presented herein could contribute to the preparation of other plant extracts with improved stability and antibacterial activity, and will help reduce the overuse of antibiotics by controlled release of natural-derived drugs.

Nanotechnology-based lipid systems applied to resistant bacterial control: A review of their use in the past two decades

The rate of infections caused by resistant bacteria to the antimicrobials available for human use grows exponentially every year, which generates major impacts on human health and the world economy. In the last two decades, human beings can witness the expressive increase in the Science and Technology worldwide, and areas such as Health Sciences have benefited from these advances in favor of human health, such as the advent of Pharmaceutical Nanotechnology as an important approach applied for bacterial infections treatment with resistance profile to available antibiotics. This review of the scientific literature brings the applicability of nanotechnology-based lipid systems as an innovative tool in the improvement of bacterial infections treatment. Important studies involving the use of liposomes, solid lipid nanoparticles, nanostructured lipid carriers, nanoemulsions, microemulsions and lipid nanocapsules were verified in the period from 2000 to 2020, where important scientific results were found and will serve as a basis for the use of these systems to remain in constant updating. This manuscript shows the use of these drug delivery systems as potential vehicles for antibacterial compounds, which opens a new hope in the complement of the antibacterial therapeutic arsenal. Important studies developed in the last 20 years are present in this review, and thus guarantees an update on the use of these drug delivery systems for researchers from different areas of Health Sciences.

Exploring the possible targeting strategies of liposomes against methicillin-resistant Staphylococcus aureus (MRSA)

Multi antibiotic-resistant bacterial infections are on the rise due to the overuse of antibiotics. Methicillin-resistant Staphylococcus aureus (MRSA) is one of the pathogens listed under the category of serious threats where vancomycin remains the mainstay treatment despite the availability of various antibacterial agents. Recently, decreased susceptibility to vancomycin from clinical isolates of MRSA has been reported and has drawn worldwide attention as it is often difficult to overcome and leads to increased medical costs, mortality, and longer hospital stays. Development of antibiotic delivery systems is often necessary to improve bioavailability and biodistribution, in order to reduce antibiotic resistance and increase the lifespan of antibiotics. Liposome entrapment has been used as a method to allow higher drug dosing apart from reducing toxicity associated with drugs. The surface of the liposomes can also be designed and enhanced with drug-release properties, active targeting, and stealth effects to prevent recognition by the mononuclear phagocyte system, thus enhancing its circulation time. The present review aimed to highlight the possible targeting strategies of liposomes against MRSA bacteremia systemically while investigating the magnitude of this effect on the minimum inhibitory concentration level.

Nanobiosystems for Antimicrobial Drug-Resistant Infections

The worldwide increased bacterial resistance toward antimicrobial therapeutics has led investigators to search for new therapeutic options. Some of the options currently exploited to treat drug-resistant infections include drug-associated nanosystems. Additionally, the use of bacteriophages alone or in combination with drugs has been recently revisited; some studies utilizing nanosystems for bacteriophage delivery have been already reported. In this review article, we focus on nine pathogens that are the leading antimicrobial drug-resistant organisms, causing difficult-to-treat infections. For each organism, the bacteriophages and nanosystems developed or used in the last 20 years as potential treatments of pathogen-related infections are discussed. Summarizing conclusions and future perspectives related with the potential of such nano-antimicrobials for the treatment of persistent infections are finally highlighted.

Nano-fats for bugs: the benefits of lipid nanoparticles for antimicrobial therapy

Bacterial infections are an imminent global healthcare threat evolving from rapidly advancing bacterial defence mechanisms that antibiotics fail to overcome. Antibiotics have been designed for systemic administration to target planktonic bacteria, leading to difficulties in reaching the site of localized bacterial infection and an inability to overcome the biological, chemical and physical barriers of bacteria, including biofilms, intracellular infections and antimicrobial resistance. The amphiphilic, biomimetic and antimicrobial properties of lipids provide a promising toolbox to innovate and advance antimicrobial therapies, overcoming the barriers presented by bacteria in order to directly and effectively treat recalcitrant infections. Nanoparticulate lipid-based drug delivery systems can enhance antibiotic permeation through the chemical and physical barriers of bacterial infections, as well as fuse with bacterial cell membranes, release antibiotics in response to bacteria and act synergistically with loaded antibiotics to enhance the total antimicrobial efficacy. This review explores the barriers presented by bacterial infections that pose bio-pharmaceutical challenges to antibiotics and how different structural and functional mechanisms of lipids can enhance antimicrobial therapies. Different nanoparticulate lipid-based systems are presented as valuable drug delivery systems to advance the efficacy of antibiotics, including liposomes, liquid crystalline nanoparticles, solid lipid nanoparticles, nanostructured lipid carriers and lipid nanocarriers. In summary, liquid crystalline nanoparticles are emerging with the greatest potential for clinical applications and commercial success as an "all-rounder" advanced lipid-based antimicrobial therapy that overcomes the multiple biological, chemical and physical barriers of bacteria.

Nanomaterial-based therapeutics for antibiotic-resistant bacterial infections

Antibiotic-resistant bacterial infections arising from acquired resistance and/or through biofilm formation necessitate the development of innovative 'outside of the box' therapeutics. Nanomaterial-based therapies are promising tools to combat bacterial infections that are difficult to treat, featuring the capacity to evade existing mechanisms associated with acquired drug resistance. In addition, the unique size and physical properties of nanomaterials give them the capability to target biofilms, overcoming recalcitrant infections. In this Review, we highlight the general mechanisms by which nanomaterials can be used to target bacterial infections associated with acquired antibiotic resistance and biofilms. We emphasize design elements and properties of nanomaterials that can be engineered to enhance potency. Lastly, we present recent progress and remaining challenges for widespread clinical implementation of nanomaterials as antimicrobial therapeutics.

Optimization, physicochemical characterization, and antimicrobial activity of a novel simvastatin nano-niosomal gel against E. coli and S. aureus

Niosomes, as a kind of drug delivery system, is widely used for the topical delivery of lipophilic drugs. Optimization of niosomes plays an essential role in enhancing their therapeutic efficiencies. This study aims to prepare an optimized niosomal formulation of simvastatin (nSIM), a lipophilic member of statins, through the experiment (Response Surface methodology). Optimized niosomes were characterized in size, polydispersity index (PDI), entrapment efficiency (EE), stability, releasing pattern, and antimicrobial activity. The different molar ratio of surfactant and cholesterol were applied to prepare various formulation of simvastatin loaded niosome. Mean particle size and size distribution were analyzed by dynamic light scattering. Antibacterial activity was determined by MIC and MBC tests against Staphylococcus aureus and Escherichia coli. The release rate of simvastatin from noisome nanoparticles was studied by the Franz diffusion cell method. The release pattern was studied through zero order, first order, Higuchi, Korsmeyer-Peppas, and Hixson-Crowell kinetics models. Optimized niosomes were obtained by span 80, drug to cholesterol ratio of 0.4 with 7 min sonication time. Mean particle size, PDI, zeta potential, and entrapment efficiency (EE%) of optimized nSIM were obtained about 168 nm, 0.34, -32.40, and 96 %, respectively. The niosomes significantly decreased the drug's releasing rate and enhanced antibacterial activity against S. aureus and E. Coli. It was found that the release pattern of drug followed the Higuchi kinetic model which means drug release is by diffusion. Overall, our findings indicated that the prepared simvastatin loaded niosomes showed good stability and biological properties than free drug. Our study suggests that niosomal formulation could be considered as a promising strategy for the delivery of poor water-soluble drugs that enhance antibacterial activity.

Oleosomes Encapsulating Sildenafil Citrate as Potential Topical Nanotherapy for Palmar Plantar Erythrodysesthesia with High Ex vivo Permeation and Deposition

Palmar plantar erythrodysesthesia (PPE) is a commonly reported skin toxicity of chemotherapeutic agents that significantly affects patients' quality of life. PPE is described as inflammation, swelling, and even cracks and ulcers in the skin of palms and soles of the feet. Conventional treatment includes topical creams, analgesics, or corticosteroids. However, serious cases are not responding to these medications. PPE has been reported to cause drug cessation or dose reduction if not properly treated. Sildenafil citrate (SC) has a well-documented activity in wound healing through improving blood supply to the affected area. However, SC has poor physicochemical properties limiting its transdermal permeation and deposition. This research endeavored to elaborate novel vesicular system with natural components, phospholipids and oleic acid, loaded with sildenafil citrate for topical management of PPE. Sildenafil-loaded oleosomes were prepared using modified ethanol injection method. Optimized oleosomes had nanometric particle size (157.6 nm), negative zeta potential (- 85.2 mv), and high entrapment efficiency (95.56%). Ex vivo studies on human skin revealed that oleosomes displayed 2.3-folds higher permeation and 4.5-folds more deposition through the human skin compared to drug suspension. Results endorsed SC oleosomes as suitable topical treatment of PPE providing ameliorated sildenafil permeability in addition to acting as a reservoir for gradual release of the drug. Graphical abstract.

Hybrid Antimicrobial Peptide Targeting Staphylococcus aureus and Displaying Anti-infective Activity in a Murine Model

Broad-spectrum antimicrobial peptides (AMPs) kill bacteria indiscriminately, increasing the possibility of an ecological imbalance in the microbiota. To solve this problem, new types of AMPs, which kill pathogenic bacteria without breaking the micro-ecological balance of the body, were proposed. Here, we successfully designed a targeting AMP, S2, which is a fusion peptide composed of a species-specific targeting domain and broad-spectrum AMP domain. In the current study, S2 showed specific killing activity against Staphylococcus aureus, and almost no resistance induced compared to penicillin. Mechanism studies indicated that S2 killed S. aureus by destroying the bacterial membrane. Meanwhile, S2 possessed excellent salt-tolerance properties and biocompatibility. Importantly, S2 exhibited perfect treatment efficacy against an S. aureus subcutaneous infection model and remained nontoxic. In conclusion, this study provides a promising strategy for designing specific AMPs against growing bacterial infections.

Recent Advances in Nanotechnology-Aided Materials in Combating Microbial Resistance and Functioning as Antibiotics Substitutes

The ongoing escalation of drug-resistant bacteria creates the leading challenges for human health. Current predictions show that deaths due to bacterial illness will be more in comparison to cancer in 2050. Irrational use of antibiotics, prolonged regimen and using as a prophylactic treatment for various infections are leading cause of microbial resistance. It is an emerging approach to introduce evolving nanomaterials (NMs) as a base of antibacterial therapy to overcome the bacterial resistance pattern. NMs can implement several bactericidal ways and turn into a challenge for bacteria to survive and develop resistance against NMs. All the pathways depend on the surface chemistry, shape, core material and size of NMs. Because of these reasons, NMs based stuff shows a critical role in advancing the treatment efficiency by interacting with the cellular system of bacteria and functioned as an antibiotic substitute. We divided this review into two sections. The first part highlights the development of microbial resistance to antibiotics and their mechanisms. The second section details the NMs mechanisms to combat antibiotic resistance. In short, we try to summarize the advances in NMs role to deal with microbial resistance and giving solution as antibiotics substitute.