Multi-functional Liposomes Enhancing Target and Antibacterial Immunity for Antimicrobial and Anti-Biofilm Against Methicillin-Resistant Staphylococcus aureus

Liposomal drug delivery strategies to eradicate bacterial biofilms: Challenges, recent advances, and future perspectives

Typical antibiotic treatments are often ineffectual against biofilm-related infections since bacteria residing within biofilms have developed various mechanisms to resist antibiotics. To overcome these limitations, antimicrobial-loaded liposomal nanoparticles are a promising anti-biofilm strategy as they have demonstrated improved antibiotic delivery and eradication of bacteria residing in biofilms. Antibiotic-loaded liposomal nanoparticles revealed remarkably higher antibacterial and anti-biofilm activities than free drugs in experimental settings. Moreover, liposomal nanoparticles can be used efficaciously for the combinational delivery of antibiotics and other antimicrobial compounds/peptide which facilitate, for instance, significant breakdown of the biofilm matrix, increased bacterial elimination from biofilms and depletion of metabolic activity of various pathogens. Drug-loaded liposomes have mitigated recurrent infections and are considered a promising tool to address challenges associated to antibiotic resistance. Furthermore, it has been demonstrated that surface charge and polyethylene glycol modification of liposomes have a notable impact on their antibacterial biofilm activity. Future investigations should tackle the persistent hurdles associated with development of safe and effective liposomes for clinical application and investigate novel antibacterial treatments, including CRISPR-Cas gene editing, natural compounds, phages, and nano-mediated approaches. Herein, we emphasize the significance of liposomes in inhibition and eradication of various bacterial biofilms, their challenges, recent advances, and future perspectives.

Poly(amino acid)-based drug delivery nanoparticles eliminate Methicillin resistant Staphylococcus aureus via tunable release of antibiotic

Bacterial infections threaten public health, and novel therapeutic strategies critically demand to be explored. Herein, poly(amino acid) (PAA)-based drug delivery nanoparticles (NPs) were designed for eliminating Methicillin resistant Staphylococcus aureus (MRSA) via tunable release of antibiotic. Using N-acryloyl amino acids (valine, valine methyl ester, aspartic acid, serine) as monomers, four kinds of amphiphilic PAAs were synthesized via photoinduced electron/energy transfer-reversible addition fragmentation chain-transfer (PET-RAFT) polymerization and were further assembled into nano-sized delivery systems. Their assemble behavior was drove mainly by hydrophobic/hydrophilic interaction, which determined the particle size, efficacy of drug loading and release; but numerous hydrogen bonding (HB) interaction also played an important role in regulating morphologies of the NPs and enriching drug-binding capacity. By changing the HB- and hydrophobic-interaction of the PAAs, the particle sizes (240.7 nm-302.7 nm), the drug loading efficiency (9.57%-19.76%), and the Rifampicin (Rif) release rate (49.6%-69.7%) of the PAA-based NPs could be tunable. Specially, the antimicrobial properties of the Rif-loaded NPs are found to be related to the release of Rif, which was determined by its hydrophobic interaction with hydrophobic blocks and HB interaction with hydrophilic blocks. These studies provide a new outlook for the design of delivery systems for the therapy of bacterial infection.

Functionalized lipid-based drug delivery nanosystems for the treatment of human infectious diseases

Infectious diseases are still public health problems. Microorganisms such as fungi, bacteria, viruses, and parasites are the main causing agents related to these diseases. In this context, the search for new effective strategies in prevention and/or treatment is considered essential, since current drugs often have side effects or end up, causing microbial resistance, making it a serious health problem. As an alternative to these limitations, nanotechnology has been widely used. The use of lipid-based drug delivery nanosystems (DDNs) has some advantages, such as biocompatibility, low toxicity, controlled release, the ability to carry both hydrophilic and lipophilic drugs, in addition to be easel scalable. Besides, as an improvement, studies involving the conjugation of signalling molecules on the surfaces of these nanocarriers can allow the target of certain tissues or cells. Thus, this review summarizes the performance of functionalized lipid-based DDNs for the treatment of infectious diseases caused by viruses, including SARS-CoV-2, bacteria, fungi, and parasites.

Nanomaterials targeting macrophages in sepsis: A promising approach for sepsis management

Sepsis is a life-threatening organ dysfunction resulting from dysregulated host responses to infection. Macrophages play significant roles in host against pathogens and the immunopathogenesis of sepsis, such as phagocytosis of pathogens, secretion of cytokines, and phenotype reprogramming. However, the rapid progression of sepsis impairs macrophage function, and conventional antimicrobial and supportive treatment are not sufficient to restore dysregulated macrophages roles. Nanoparticles own unique physicochemical properties, surface functions, localized surface plasmon resonance phenomenon, passive targeting in vivo, good biocompatibility and biodegradability, are accessible for biomedical applications. Once into the body, NPs are recognized by host immune system. Macrophages are phagocytes in innate immunity dedicated to the recognition of foreign substances, including nanoparticles, with which an immune response subsequently occurs. Various design strategies, such as surface functionalization, have been implemented to manipulate the recognition of nanoparticles by monocytes/macrophages, and engulfed by them to regulate their function in sepsis, compensating for the shortcomings of sepsis traditional methods. The review summarizes the mechanism of nanomaterials targeting macrophages and recent advances in nanomedicine targeting macrophages in sepsis, which provides good insight for exploring macrophage-based nano-management in sepsis.

Development of a Novel Lipid-Based Nanosystem Functionalized with WGA for Enhanced Intracellular Drug Delivery

Despite a considerable number of new antibiotics under going clinical trials, treatment of intracellular pathogens still represents a major pharmaceutical challenge. The use of lipid nanocarriers provides several advantages such as protection from compound degradation, increased bioavailability, and controlled and targeted drug release. Wheat germ agglutinin (WGA) is known to have its receptors on the alveolar epithelium and increase phagocytosis. The present study aimed to produce nanostructured lipid carriers with novel glycosylated amphiphilic employed to attach WGA on the surface of the nanocarriers to improve intracellular drug delivery. High-pressure homogenization was employed to prepare the lipid nanocarriers. In vitro, high-content analysis and flow cytometry assay was employed to study the increased uptake by macrophages when the nanocarriers were grafted with WGA. A lipid nanocarrier with surface-functionalized WGA protein (~200 nm, PDI > 0.3) was successfully produced and characterized. The system was loaded with a lipophilic model compound (quercetin; QU), demonstrating the ability to encapsulate a high amount of compound and release it in a controlled manner. The nanocarrier surface functionalization with the WGA protein increased the phagocytosis by macrophages. The system proposed here has characteristics to be further explored to treat intracellular pathogens.

Nanocarriers for combating biofilms: advantages and challenges

Bacterial biofilms are highly resistant to antibiotics and pose a great threat to human and animal health. The control and removal of bacterial biofilms have become an important topic in the field of bacterial infectious diseases. Nanocarriers show great anti-biofilm potential because of their small particle size and strong permeability. In this review, the advantages of nanocarriers for combating biofilms are analyzed. Nanocarriers can act on all stages of bacterial biofilm formation and diffusion. They can improve the scavenging effect of biofilm by targeting biofilm, destroying extracellular polymeric substances, and enhancing the biofilm permeability of antimicrobial substances. Nanocarriers can also improve the antibacterial ability of antimicrobial drugs against bacteria in biofilm by protecting the loaded drugs and controlling the release of antimicrobial substances. Additionally, we emphasize the challenges faced in using nanocarrier formulations and translating them from a preclinical level to the clinical setting.

Delivering macrolide antibiotics to heal a broken heart - And other inflammatory conditions

Drug carriers to deliver macrolide antibiotics, such as azithromycin, show promise as antibacterial agents. Macrolide drug carriers have largely focused on improving the drug stability and pharmacokinetics, while reducing adverse reactions and improving antibacterial activity. Recently, macrolides have shown promise in treating inflammatory conditions by promoting a reparative effect and limiting detrimental pro-inflammatory responses, which shifts the immunologic setpoint from suppression to balance. While macrolide drug carriers have only recently been investigated for their ability to modulate immune responses, the previous strategies that deliver macrolides for antibacterial therapy provide a roadmap for repurposing the macrolide drug carriers for therapeutic interventions targeting inflammatory conditions. This review describes the antibacterial and immunomodulatory activity of macrolides, while assessing the past in vivo evaluation of drug carriers used to deliver macrolides with the intention of presenting a case for increased effort to translate macrolide drug carriers into the clinic.

Aptamer-Targeted Drug Delivery for Staphylococcus aureus Biofilm

Treatment of Staphylococcus aureus biofilm infections using conventional antibiotic therapy is challenging as only doses that are sublethal to the biofilm can be administered safely to patients. A potential solution to this challenge is targeted drug delivery. In this study, we tailored an aptamer-targeted liposomal drug delivery system for accumulation and delivery of antibiotics locally in S. aureus biofilm. In our search for a suitable targeting ligand, we identified six DNA aptamers that bound to S. aureus cells in biofilms, and we demonstrated that one of these aptamers could facilitate accumulation of liposomes around S. aureus cells inside the biofilm. Aptamer-targeted liposomes encapsulating a combination of vancomycin and rifampicin were able to eradicate S. aureus biofilm upon 24 h of treatment in vitro. Our results point to that aptamer-targeted drug delivery of antibiotics is a potential new strategy for treatment of S. aureus biofilm infections.

Infection microenvironment-related antibacterial nanotherapeutic strategies

The emergence and spread of antibiotic resistance is one of the biggest challenges in public health. There is an urgent need to discover novel agents against the occurrence of multidrug-resistant bacteria, such as methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci. The drug-resistant pathogens are able to grow and persist in infected sites, including biofilms, phagosomes, or phagolysosomes, which are more difficult to eradicate than planktonic ones and also foster the development of drug resistance. For years, various nano-antibacterial agents have been developed in the forms of antibiotic nanocarriers. Inorganic nanoparticles with intrinsic antibacterial activity and inert nanoparticles assisted by external stimuli, including heat, photon, magnetism, or sound, have also been discovered. Many of these strategies are designed to target the unique microenvironment of bacterial infections, which have shown potent antibacterial effects in vitro and in vivo. This review summarizes ongoing efforts on antibacterial nanotherapeutic strategies related to bacterial infection microenvironments, including targeted antibacterial therapy and responsive antibiotic delivery systems. Several grand challenges and future directions for the development and translation of effective nano-antibacterial agents are also discussed. The development of innovative nano-antibacterial agents could provide powerful weapons against drug-resistant bacteria in systemic or local bacterial infections in the foreseeable future.

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.

Lipoplexes to Deliver Oligonucleotides in Gram-Positive and Gram-Negative Bacteria: Towards Treatment of Blood Infections

Bacterial resistance to antibiotics threatens the ability to treat life-threatening bloodstream infections. Oligonucleotides (ONs) composed of nucleic acid mimics (NAMs) able to inhibit essential genes can become an alternative to traditional antibiotics, as long as they are safely transported in human serum upon intravenous administration and they are carried across the multilayered bacterial envelopes, impermeable to ONs. In this study, fusogenic liposomes were considered to transport the ONs and promote their internalization in clinically relevant bacteria. Locked nucleic acids and 2′-OMethyl RNA were evaluated as model NAMs and formulated into DOTAP–DOPE liposomes followed by post-PEGylation. Our data showed a complexation stability between the post-PEGylated liposomes and the ONs of over 82%, during 24 h in native human serum, as determined by fluorescence correlation spectroscopy. Quantification by a lipid-mixing assay showed that liposomes, with and without post-PEGylation, fused with all bacteria tested. Such fusion promoted the delivery of a fraction of the ONs into the bacterial cytosol, as observed by fluorescence in situ hybridization and bacterial fractionation. In short, we demonstrated for the first time that liposomes can safely transport ONs in human serum and intracellularly deliver them in both Gram-negative and -positive bacteria, which holds promise towards the treatment of bloodstream infections.

Pulmonary biofilm-based chronic infections and inhaled treatment strategies

Certain pulmonary diseases, such as cystic fibrosis (CF), non-CF bronchiectasis, chronic obstructive pulmonary disease, and ventilator-associated pneumonia, are usually accompanied by respiratory tract infections due to the physiological alteration of the lung immunological defenses. Recurrent infections may lead to chronic infection through the formation of biofilms. Chronic biofilm-based infections are challenging to treat using antimicrobial agents. Therefore, effective ways to eradicate biofilms and thus relieve respiratory tract infection require the development of efficacious agents for biofilm destruction, the design of delivery carriers with biofilm-targeting and/or penetrating abilities for these agents, and the direct delivery of them into the lung. This review provides an in-depth description of biofilm-based infections caused by pulmonary diseases and focuses on current existing agents that are administered by inhalation into the lung to treat biofilm, which include i) inhalable antimicrobial agents and their combinations, ii) non-antimicrobial adjuvants such as matrix-targeting enzymes, mannitol, glutathione, cyclosporin A, and iii) liposomal formulations of anti-biofilm agents. Finally, novel agents that have shown promise against pulmonary biofilms as well as traditional and new devices for pulmonary delivery of anti-biofilm agents into the lung are also discussed.

Chemical Composition, Antimicrobial and Insecticidal Activities of Essential Oils of Discarded Perfume Lemon and Leaves (Citrus Limon (L.) Burm. F.) as Possible Sources of Functional Botanical Agents

Two essential oils were isolated from discarded perfume lemon and leaves (Citrus limon (L.) Burm. F.) by hydro-distillation with good yield (0.044% for perfume lemon and 0.338% for leaves). Their biological activities were evaluated against five selected bacterial strains and Aedes albopictus (Ae. albopictus, Diptera: Culicidae). Chemical composition indicated that both essential oils were rich in essential phytochemicals including hydrocarbons, monoterpenes and sesquiterpene. These constituents revealed some variability among the oils displaying interesting chemotypes (R)-(+)-limonene (12.29–49.63%), citronellal (5.37–78.70%) and citronellol (2.98–7.18%). The biological assessments proved that the two essential oils had similar effect against bacterial (inhibition zones diameter ranging from 7.27 ± 0.06 to 10.37 ± 0.15 mm; MICs and MBCs ranging from 1.6 to 6.4 mg/mL); against Ae. albopictus larvae (LC₅₀ ranging from 384.81 to 395.09 ppm) and adult mosquito (LD₅₀ ranging from 133.059 to 218.962 μg/cm²); the activity of the two chemotypes ((R)-(+)-limonene and citronellal): larvae (LC₅₀ ranging from 267.08 to 295.28 ppm), which were all presented in dose-dependent manners. Through this work, we have showcased that recycling and reusing of agriculture by-products, such as discarded perfume lemon and leaves can produce eco-friendly alternatives in bacterial disinfectants and mosquito control product.

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.

Liposome as a delivery system for the treatment of biofilm-mediated infections

Biofilm formation by pathogenic microorganisms has been a tremendous challenge for antimicrobial therapies due to various factors. The biofilm matrix sequesters bacterial cells from the exterior environment and therefore prevents antimicrobial agents from reaching the interior. In addition, biofilm surface extracellular polymeric substances can absorb antimicrobial agents and thus reduce their bioavailability. To conquer these protection mechanisms, liposomes have been developed into a drug delivery system for antimicrobial agents against biofilm-mediated infections. The unique characteristics of liposomes, including versatility for cargoes, target-specificity, nonimmunogenicity, low toxicity, and biofilm matrix-/cell membrane-fusogenicity, remarkably improve the effectiveness of antimicrobial agents and minimize recurrence of infections. This review summarizes current development of liposomal carriers for biofilm therapeutics, presents evidence in their practical applications and discusses their potential limitations.

Synthesis and biological evaluation of pentacyclic triterpenoid derivatives as potential novel antibacterial agents

A series of ursolic acid (UA), oleanolic acid (OA) and 18β-glycyrrhetinic acid (GA) derivatives were synthesized by introducing a range of substituted aromatic side-chains at the C-2 position after the hydroxyl group at C-3 position was oxidized. Their antibacterial activities were evaluated in vitro against a panel of four Staphylococcus spp. The results revealed that the introduction of aromatic side-chains at the C-2 position of GA led to the discovery of potent triterpenoid derivatives for inhibition of both drug sensitive and resistant S. aureus, while the other two series derivatives of UA and OA showed no significant antibacterial activity even at high concentrations. In particular, GA derivative 33 showed good potency against all four Staphylococcus spp. (MIC = 1.25-5 μmol/L) with acceptable pharmacokinetics properties and low cytotoxicity in vitro. Molecular docking was also performed using S. aureus DNA gyrase to rationalize the observed antibacterial activity. This series of GA derivatives has strong potential for the development of a new type of triterpenoid antibacterial agent.

Nanotechnological strategies for systemic microbial infections treatment: A review

Systemic infections is one of the major causes of mortality worldwide, and a shortage of drug approaches applied for the rapid and necessary treatment contribute to increase the levels of death in affected patients. Several drug delivery systems based in nanotechnology such as metallic nanoparticles, liposomes, nanoemulsion, microemulsion, polymeric nanoparticles, solid lipid nanoparticles, dendrimers, hydrogels and liquid crystals can contribute in the biological performance of active substances for the treatment of microbial diseases triggered by fungi, bacteria, virus and parasites. In the presentation of these statements, this review article present and demonstrate the effectiveness of these drug delivery systems for the treatment of systemic diseases caused by several microorganisms, through a review of studies on scientific literature worldwide that contributes to better information for the most diverse professionals from the areas of health sciences. The studies demonstrated that the drug delivery systems described can contribute to the therapeutic scenario of these diseases, being classified as safe, active platforms and with therapeutic versatility.

Impact of nanosystems in Staphylococcus aureus biofilms treatment

Staphylococcus aureus (S. aureus) is considered by the World Health Organization as a high priority pathogen for which new therapies are needed. This is particularly important for biofilm implant-associated infections once the only available treatment option implies a surgical procedure combined with antibiotic therapy. Consequently, these infections represent an economic burden for Healthcare Systems. A new strategy has emerged to tackle this problem: for small bugs, small particles. Here, we describe how nanotechnology-based systems have been studied to treat S. aureus biofilms. Their features, drawbacks and potentialities to impact the treatment of these infections are highlighted. Furthermore, we also outline biofilm models and assays required for preclinical validation of those nanosystems to smooth the process of clinical translation.

Lipid-Based Antimicrobial Delivery-Systems for the Treatment of Bacterial Infections

Many nanotechnology-based antimicrobials and antimicrobial-delivery-systems have been developed over the past decades with the aim to provide alternatives to antibiotic treatment of infectious-biofilms across the human body. Antimicrobials can be loaded into nanocarriers to protect them against de-activation, and to reduce their toxicity and potential, harmful side-effects. Moreover, antimicrobial nanocarriers such as micelles, can be equipped with stealth and pH-responsive features that allow self-targeting and accumulation in infectious-biofilms at high concentrations. Micellar and liposomal nanocarriers differ in hydrophilicity of their outer-surface and inner-core. Micelles are self-assembled, spherical core-shell structures composed of single layers of surfactants, with hydrophilic head-groups and hydrophobic tail-groups pointing to the micellar core. Liposomes are composed of lipids, self-assembled into bilayers. The hydrophilic head of the lipids determines the surface properties of liposomes, while the hydrophobic tail, internal to the bilayer, determines the fluidity of liposomal-membranes. Therefore, whereas micelles can only be loaded with hydrophobic antimicrobials, hydrophilic antimicrobials can be encapsulated in the hydrophilic, aqueous core of liposomes and hydrophobic or amphiphilic antimicrobials can be inserted in the phospholipid bilayer. Nanotechnology-derived liposomes can be prepared with diameters <100-200 nm, required to prevent reticulo-endothelial rejection and allow penetration into infectious-biofilms. However, surface-functionalization of liposomes is considerably more difficult than of micelles, which explains while self-targeting, pH-responsive liposomes that find their way through the blood circulation toward infectious-biofilms are still challenging to prepare. Equally, development of liposomes that penetrate over the entire thickness of biofilms to provide deep killing of biofilm inhabitants still provides a challenge. The liposomal phospholipid bilayer easily fuses with bacterial cell membranes to release high antimicrobial-doses directly inside bacteria. Arguably, protection against de-activation of antibiotics in liposomal nanocarriers and their fusogenicity constitute the biggest advantage of liposomal antimicrobial carriers over antimicrobials free in solution. Many Gram-negative and Gram-positive bacterial strains, resistant to specific antibiotics, have been demonstrated to be susceptible to these antibiotics when encapsulated in liposomal nanocarriers. Recently, also progress has been made concerning large-scale production and long-term storage of liposomes. Therewith, the remaining challenges to develop self-targeting liposomes that penetrate, accumulate and kill deeply in infectious-biofilms remain worthwhile to pursue.

Alkyl rhamnosides, a series of amphiphilic materials exerting broad-spectrum anti-biofilm activity against pathogenic bacteria via multiple mechanisms

As novel amphiphilic materials, six uncharged alkyl rhamnosides incorporating various alkyl chain and one rhamnose amine quaternary ammonium salt were successfully synthesized in this study. Their amphiphilic properties (HLB and CMC), antimicrobial and anti-biofilm activity against S. aureus and P. aeruginosa were investigated. Differentially regulated proteins and pathways were identified by comparative proteomics research to first give a sight on how alkyl rhamnosides performed the anti-biofilm activity at protein and pathway levels. Among the uncharged alkyl rhamnosides, dodecyl rhamnoside and octyl rhamnoside showed the best antimicrobial and anti-biofilm ability against S. aureus and against P. aeruginosa, respectively. Interestingly, the relationships between amphiphilic properties or MIC with anti-biofilm activity were first established. Uncharged alkyl rhamnoside with an optimized HLB value of 5.0 had both the strongest antibacterial and anti-biofilm activity against S. aureus, and MIC was the maximum biofilm inhibitory concentration for all alkyl rhamnosides. Alkyl rhamnosides have a significant overall regulatory effect on the proteomics and pathways of bacterial biofilms, including energy production, substrates transportation, signal transduction, key molecules balance, and so on. These amphiphilic materials have a great potential to be used as additives in pharmaceutic, cosmetic, food industry, hospital and in other non-medical fields.

Lipid-Based Antimicrobial Delivery-Systems for the Treatment of Bacterial Infections

Many nanotechnology-based antimicrobials and antimicrobial-delivery-systems have been developed over the past decades with the aim to provide alternatives to antibiotic treatment of infectious-biofilms across the human body. Antimicrobials can be loaded into nanocarriers to protect them against de-activation, and to reduce their toxicity and potential, harmful side-effects. Moreover, antimicrobial nanocarriers such as micelles, can be equipped with stealth and pH-responsive features that allow self-targeting and accumulation in infectious-biofilms at high concentrations. Micellar and liposomal nanocarriers differ in hydrophilicity of their outer-surface and inner-core. Micelles are self-assembled, spherical core-shell structures composed of single layers of surfactants, with hydrophilic head-groups and hydrophobic tail-groups pointing to the micellar core. Liposomes are composed of lipids, self-assembled into bilayers. The hydrophilic head of the lipids determines the surface properties of liposomes, while the hydrophobic tail, internal to the bilayer, determines the fluidity of liposomal-membranes. Therefore, whereas micelles can only be loaded with hydrophobic antimicrobials, hydrophilic antimicrobials can be encapsulated in the hydrophilic, aqueous core of liposomes and hydrophobic or amphiphilic antimicrobials can be inserted in the phospholipid bilayer. Nanotechnology-derived liposomes can be prepared with diameters <100-200 nm, required to prevent reticulo-endothelial rejection and allow penetration into infectious-biofilms. However, surface-functionalization of liposomes is considerably more difficult than of micelles, which explains while self-targeting, pH-responsive liposomes that find their way through the blood circulation toward infectious-biofilms are still challenging to prepare. Equally, development of liposomes that penetrate over the entire thickness of biofilms to provide deep killing of biofilm inhabitants still provides a challenge. The liposomal phospholipid bilayer easily fuses with bacterial cell membranes to release high antimicrobial-doses directly inside bacteria. Arguably, protection against de-activation of antibiotics in liposomal nanocarriers and their fusogenicity constitute the biggest advantage of liposomal antimicrobial carriers over antimicrobials free in solution. Many Gram-negative and Gram-positive bacterial strains, resistant to specific antibiotics, have been demonstrated to be susceptible to these antibiotics when encapsulated in liposomal nanocarriers. Recently, also progress has been made concerning large-scale production and long-term storage of liposomes. Therewith, the remaining challenges to develop self-targeting liposomes that penetrate, accumulate and kill deeply in infectious-biofilms remain worthwhile to pursue.

The biological evaluation of fusidic acid and its hydrogenation derivative as antimicrobial and anti-inflammatory agents

Background

Fusidic acid (FA) (WU-FA-00) is the only commercially available antimicrobial from the fusidane family that has a narrow spectrum of activity against Gram-positive bacteria.

Methods

Herein, the hydrogenation derivative (WU-FA-01) of FA was prepared and both compounds were examined against a panel of six bacterial strains. In addition, their anti-inflammatory properties were evaluated using a 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced mouse ear edema model.

Results

The results of the antimicrobial assay revealed that both WU-FA-00 and WU-FA-01 displayed a high level of antimicrobial activity against Gram-positive strains. Moreover, killing kinetic studies were performed and the results were in accordance with the minimum inhibitory concentration and minimum bactericidal concentration results. We also demonstrated that the topical application of WU-FA-00 and WU-FA-01 effectively decreased TPA-induced ear edema in a dose-dependent manner. This inhibitory effect was associated with the inhibition of TPA-induced upregulation of proinflammatory cytokines IL-1β, TNF-α, and COX-2. WU-FA-01 significantly suppressed the expression levels of p65, IκB-α, and p-IκB-α in the TPA-induced mouse ear model.

Conclusion

Overall, our results showed that WU-FA-00 and WU-FA-01 not only had effective antimicrobial activities in vitro, especially to the Gram-positive bacteria, but also possessed strong anti-inflammatory effects in vivo. These results provide a scientific basis for developing FA derivatives as antimicrobial and anti-inflammatory agents.

Current Therapeutic Strategies in Clinical Urology

The field of urology encompasses all benign and malignant disorders of the urinary tract and the male genital tract. Urological disorders convey a huge economic and patient quality-of-life burden. Hospital acquired urinary tract infections, in particular, are under scrutiny as a measure of hospital quality. Given the prevalence of these pathologies, there is much progress still to be made in available therapeutic options in order to minimize side effects and provide effective care. Current drug delivery mechanisms in urological malignancy and the benign urological conditions of overactive bladder (OAB), interstitial cystitis/bladder pain syndrome (IC/BPS), and urinary tract infection (UTI) will be reviewed herein. Both systemic and local therapies will be discussed including sustained release formulations, nanocarriers, hydrogels and other reservoir systems, as well as gene and immunotherapy. The primary focus of this review is on agents which have passed the preclinical stages of development.

Local drug delivery in the urinary tract: current challenges and opportunities

Drug delivery is an important consideration in disease treatment. There are many opportunities for novel methods and technologies to hold promising roles in overcoming traditional obstacles. Delivery systems functionalised to boast synergistic antimicrobial effects, specific targeting, and enhanced bioavailability allow for improved therapeutic potential and better patient outcomes. Many of these delivery modalities find clinical practicality in the field of urology, specifically in the treatment of urinary tract infections (UTIs) and offer advantages over conventional methods. The aim of this review article is to discuss the current modalities of treatment for UTIs and the recent technological advancements for optimising drug delivery. We focus on challenges that persist in drug delivery during UTIs including barriers to antimicrobial penetration, drug resistance, biofilm formation and specific targeting limitations. With a discussion on how emerging methods combat these concerns, we present an overview of potential therapies with special emphasis on nanoparticle-based applications.

Wheat germ agglutinin-induced paraptosis-like cell death and protective autophagy is mediated by autophagy-linked FYVE inhibition

Wheat germ agglutinin (WGA) is a lectin that specifically binds cell surface glycoproteins and disrupts nuclear pore complex function through its interaction with POM121. Our data indicate WGA induces paraptosis-like cell death without caspase activation. We observed the main features of paraptosis, including cytoplasmic vacuolation, endoplasmic reticulum dilation and increased ER stress, and the unfolded protein response in WGA-treated cervical carcinoma cells. Conversion of microtubule-associated protein I light chain 3 (LC3-I) into LC3-II and punctuate formation suggestive of autophagy were observed in WGA-treated cells. WGA-induced autophagy antagonized paraptosis in HeLa and CaSKi cells, which expressed autophagy-linked FYVE (Alfy) protein, but not in SiHa cells that did not express Alfy. Alfy knockdown in HeLa cells induced paraptosis-like cell death. These data indicate that WGA-induced cell death occurs through paraptosis and that autophagy may exert a protective effect. WGA treatment and Alfy inhibition could be an effective therapeutic strategy for apoptosis-resistant cervical cancer cells.

Pathogenic features and characteristics of food borne pathogens biofilm: Biomass, viability and matrix

Biofilm is a ubiquitous growth pattern of bacterial species survival but is notorious for its threat on public health and food contamination. Extensive studies of the biofilm structure, formation, quantification, quorum sensing system and underlying control strategies have been reported during the past decades. Insightful elucidation of the pathogenic features and characteristic of bacterial biofilm can facilitate in devising appropriate control strategies for biofilm eradication. Therefore, this review mainly summarized the pathogenic features of biofilms from food borne microorganisms, including the biomass (which could be quantified using crystal violet and fluorogenic dye Syto9 assays), viability (which could be determined by tetrazolium salts, fluorescein diacetate, resazurin staining and alamar blue assays) and matrix (which are commonly detected by dimethyl methylene blue and wheat germ agglutinin assays). In addition, three features were further compared with its particular benefits in specific application.

Effects of nanobubble collapse on cell membrane integrity

Recent studies have shown that ultrasound is used to open drug-carrying liposomes to release their payloads; however, a shockwave energetic enough to rupture lipid membranes can cause collateral damage to surrounding cells. Similarly, a destructive shockwave, which may be used to rupture a cell membrane in order to lyse the cell (e.g., as in cancer treatments) may also impair or destroy nearby healthy tissue. To address this problem, we use dissipative particle dynamic (DPD) simulation to investigate the addition of a cavitation bubble between the shockwave and the model cell membrane to alter the shockwave front, allowing low-velocity shockwaves to specifically damage an intended target. We focus specifically on a spherical lipid bilayer model, and note the effect of shockwave velocity, bubble size, and orientation on the damage to the model cell. We show that a cavitation bubble greatly decreases the necessary shockwave velocity required to damage the lipid bilayer and rupture the model cell. The cavitation bubble focuses the kinetic energy of the shockwave front into a smaller area, inducing penetration at the edge of the model cell. With this work, we provide a comprehensive approach to the intricacies of model cell destruction via shockwave impact, and hope to offer a guideline for initiating targeted cellular destruction using induced cavitation bubbles and low-velocity shockwaves.

Erythrocyte membrane-coated nanogel for combinatorial antivirulence and responsive antimicrobial delivery against Staphylococcus aureus infection

We reported an erythrocyte membrane-coated nanogel (RBC-nanogel) system with combinatorial antivirulence and responsive antibiotic delivery for the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infection. RBC membrane was coated onto the nanogel via a membrane vesicle templated in situ gelation process, whereas the redox-responsiveness was achieved by using a disulfide bond-based crosslinker. We demonstrated that the RBC-nanogels effectively neutralized MRSA-associated toxins in extracellular environment and the toxin neutralization in turn promoted bacterial uptake by macrophages. In intracellular reducing environment, the RBC-nanogels showed an accelerated drug release profile, which resulted in more effective bacterial inhibition. When added to the macrophages infected with intracellular MRSA bacteria, the RBC-nanogels significantly inhibited bacterial growth compared to free antibiotics and non-responsive nanogel counterparts. These results indicate the great potential of the RBC-nanogel system as a new and effective antimicrobial agent against MRSA infection.

Nanoparticles Suitable for BCAA Isolation Can Serve for Use in Magnetic Lipoplex-Based Delivery System for L, I, V, or R-rich Antimicrobial Peptides

This paper investigates the synthesis of paramagnetic nanoparticles, which are able to bind branched chain amino acids (BCAAs)—leucine, valine, and isoleucine and, thus, serve as a tool for their isolation. Further, by this, we present an approach for encapsulation of nanoparticles into a liposome cavity resulting in a delivery system. Analyses of valine and leucine in entire complex show that 31.3% and 32.6% recoveries are reached for those amino acids. Evaluation of results shows that the success rate of delivery in Escherichia coli (E. coli) is higher in the case of BCAAs on nanoparticles entrapped in liposomes (28.7% and 34.7% for valine and leucine, respectively) when compared to nanoparticles with no liposomal envelope (18.3% and 13.7% for valine and leucine, respectively). The nanoparticles with no liposomal envelope exhibit the negative zeta potential (−9.1 ± 0.3 mV); however, their encapsulation results in a shift into positive values (range of 28.9 ± 0.4 to 33.1 ± 0.5 mV). Thus, electrostatic interactions with negatively-charged cell membranes (approx. −50 mV in the case of E. coli) leads to a better uptake of cargo. Our delivery system was finally tested with the leucine-rich antimicrobial peptide (FALALKALKKALKKLKKALKKAL) and it is shown that hemocompatibility (7.5%) and antimicrobial activity of the entire complex against E. coli, Staphylococcus aureus (S. aureus), and methicilin-resistant S. aureus (MRSA) is comparable or better than conventional penicillin antibiotics.