Liposomal mupirocin holds promise for systemic treatment of invasive Staphylococcus aureus infections

Three-dimensional printed polyelectrolyte construct containing mupirocin-loaded quaternized chitosan nanoparticles for skin repair

Despite substantial advancements in wound dressing development, effective skin repair remains a significant challenge, largely due to the persistent issue of recurrent infections. Three-dimensional printed constructs that integrate bioactive and antibacterial agents hold significant potential to address this challenge. In this study, a 3D-printed hydrogel scaffold composed of polyallylamine hydrochloride (PAH) and pectin (Pc), incorporated with mupirocin (Mp)-loaded quaternized chitosan nanoparticles (QC NPs) was fabricated. The primary objective of this study was to facilitate a controlled and sustained release of Mp via the QC NPs. The average size of QC-Mp nanoparticles was measured to be 66.05 nm and the average strand diameter and pore size of the 3D-printed construct were measured as 147.22 ± 5.83 and 388.44 ± 14.50 μm, respectively. The hemolysis rate of all scaffolds was below 2 %, indicating that they can be classified as non-hemolytic materials with sufficient blood compatibility. The PAH-Pc/QC-Mp scaffold exhibited significant antibacterial activity, enhanced cell viability in HaCat cells, sustained Mp release until day 7 (⁓60 %), and in-vivo wound healing promotion by stimulation of human keratinocytes. In conclusion, the proposed biocompatible construct demonstrates significant potential for the treatment of chronic and infected wounds by preventing infection and promoting accelerated wound healing.

Nano-mupirocin as tumor-targeted antibiotic: Physicochemical, immunotoxicological and pharmacokinetic characterization, and effect on gut microbiome

Nano-mupirocin is a PEGylated nano-liposomal formulation of the antibiotic mupirocin, undergoing evaluation for treating infectious diseases and intratumor bacteria. Intratumoral microbiota play an important role in the regulation of tumor progression and therapeutic efficacy. However, antibiotic use to target intratumoral bacteria should be performed in a way that will not affect the gut microbiota, found to enable the efficacy of cancer treatments. Nano-mupirocin may offer such a selective treatment. Herein, we demonstrate the ability of Nano-mupirocin to successfully target tumor-residing Fusobacterium nucleatum without an immediate effect on the gut microbiome. In-depth characterization of this novel formulation was performed, and the main findings include: (i). the pharmacokinetic analysis of mupirocin administered as Nano-mupirocin vs mupirocin lithium (free drug) demonstrated that most of the Nano-mupirocin in plasma is liposome associated; (ii). microbiome analysis of rat feces showed no significant short-term difference between Nano-mupirocin, mupirocin lithium and controls; (iii). Nano-mupirocin was active against intratumoral F. nucleatum, a tumor promoting bacteria that accumulates in tumors of the AT3 mice model of breast cancer. These data suggest the ability of Nano-mupirocin to target tumor residing and promoting bacteria.

Developments and Trends of Nanotechnology Application in Sepsis: A Comprehensive Review Based on Knowledge Visualization Analysis

Sepsis, a common life-threatening clinical condition, continues to have high morbidity and mortality rates, despite advancements in management. In response, significant research efforts have been directed toward developing effective strategies. Within this scope, nanotechnology has emerged as a particularly promising field, attracting significant interest for its potential to enhance disease diagnosis and treatment. While several reviews have highlighted the use of nanoparticles in sepsis, comprehensive studies that summarize and analyze the hotspots and research trends are lacking. To identify and further promote the development of nanotechnology in sepsis, a bibliometric analysis was conducted on the relevant literature, assessing research trends and hotspots in the application of nanomaterials for sepsis. Next, a comprehensive review of the subjectively recognized research hotspots in sepsis, including nanotechnology-enhanced biosensors and nanoscale imaging for sepsis diagnostics, and nanoplatforms designed for antimicrobial, immunomodulatory, and detoxification strategies in sepsis therapy, is elucidated, while the potential side effects and toxicity risks of these nanomaterials were discussed. Particular attention is given to biomimetic nanoparticles, which mimic the biological functions of source cells like erythrocytes, immune cells, and platelets to evade immune responses and effectively deliver therapeutic agents, demonstrating substantial translational potential. Finally, current challenges and future perspectives of nanotechnology applications in sepsis with a view to maximizing their great potential in the research of translational medicine are also discussed.

Mupirocin loaded core-shell pluronic-pectin-keratin nanofibers improve human keratinocytes behavior, angiogenic activity and wound healing

In the current study, a core-shell nanofibrous wound dressing based on Pluronic-F127 (F127) containing 2 wt% mupirocin (Mup) core and pectin (Pec)-keratin (Kr) shell was fabricated through coaxial electrospinning technique, and the blended nanofibers were also fabricated from the same materials. The fiber diameter and specific surface area of the blended nanofibers were about 101.56 nm and 20.16 m2/g, while for core-shell nanofibers they were about 97.32 nm and 25.26 m2/g, respectively. The resultant blended and core-shell nanofibers experienced a degradation of 27.65 % and 32.28 % during 7 days, respectively. The drug release profile of core-shell nanofibers revealed a sustained release of Mup over 7 days (87.66 %), while the blended F127-Pec-Kr-Mup nanofibers had a burst release within the first few hours (89.38 % up to 48 h) and a cumulative release of 91.36 % after 7 days. Due to the controlled release of Mup, the core-shell structure significantly improved the human keratinocytes behavior, angiogenic potential and wound healing in a rat model compared to the blended structure. In conclusion, the F127-Mup/Pec-Kr core-shell nanofibrous wound dressing appears to be a promising candidate for the prevention of infection, and can potentially accelerate the recovery and healing of chronic and ischemic wounds.

Combinatorial treatment of mupirocin nanomicelle in insulin-based gel for wound healing in diabetic rats

Background:

Diabetic wounds remain an important clinical challenge over the past few decades. Nanodrug delivery systems play a crucial role in the treatment of chronic infections and wound healing.

Objectives:

To evaluate the wound healing potential of newly synthesized and characterized mupirocin (MP) nanomicelle (NM) in insulin (I)-based gel (MP-NM-I), utilizing alloxan-induced diabetic rat model.

Materials and Methods:

MP-NM-I was prepared by solvent evaporation technique, 96 male rats were assigned randomly into eight groups (n = 12): one group is healthy, and the remaining seven groups were diabetic and wounded receiving treatments of gel base, tween 80, I, MP, MP-I, MP-NM, and MP-NM-I, respectively. Rats were sacrificed after 7 and 14 days of wounding. Blood samples were collected for glucose and insulin concentration measurement. Skin biopsies were examined by histological and immunohistochemical analyses.

Results:

Diabetes was confirmed after a significant increase in blood glucose and a decrease in serum insulin concentrations (P ≤ 0.001). MP-NM– and MP-NM-I–treated groups presented a rapid wound closure (100 ± 0, P ≤ 0.001), and the bacterial growth in these samples was relatively low (P ≤ 0.001). Histological examination established a significant decrease in inflammatory cells (P ≤ 0.001) with a significant elevation in tissue re-epithelialization, fibroblasts, angiogenesis, and collagen fibers (P ≤ 0.001). Immunohistochemical investigation presented a significant decrease in tumor necrosis factor-α, increase in vascular endothelial growth factors, and interleukin-10 scores (P ≤ 0.001).

Conclusion:

The developed formula of MP-NM with or without insulin is more effective than MP alone for diabetic wound healing in rats, because it accelerated wound closure. Accordingly, the formula might serve as an innovative tool for diabetic wound healing.

Development of a Nanoemulgel for the Topical Application of Mupirocin

Mupirocin (MUP) is an effective topical antibiotic with poor skin permeability; however, its skin permeability can be improved by a nanoemulsion formulation based on eucalyptus oil or eucalyptol. Despite this improvement, the nanoemulsion has limitations, such as low viscosity, low spreadability, and poor retention on the skin. To overcome these limitations, the aim of this study was to develop a nanoemulgel formulation that would enhance its rheological behaviour and physicochemical properties. The MUP nanoemulgel was prepared by incorporating a preprepared MUP nanoemulsion into Carbopol gel at a concentration of 0.75% in a 1:1 ratio. The nanoemulgel formulations were characterised and evaluated for their physicochemical and mechanical strength properties, rheological behaviour, and in vitro skin permeation and deposition, as well as antibacterial studies. Both nanoemulgels exhibited stability at temperatures of 4 and 25 °C for a period of 3 months. They had a smooth, homogenous, and consistent appearance and displayed non-Newtonian pseudoplastic behaviour, with differences in their viscosity and spreadability. However, both nanoemulgels exhibited lower skin permeability compared to the marketed control. The local accumulation efficiency of MUP from nanoemulgel after 8 h was significantly higher than that of the control, although there was no significant difference after 24 h. Micro-CT scan imaging allowed visualisation of these findings and interpretation of the deposited drug spots within the layers of treated skin. While there were no significant differences in the antibacterial activities between the nanoemulgels and the control, the nanoemulgels demonstrated superiority over the control due to their lower content of MUP. These findings support the potential use of the nanoemulgel for targeting skin lesions where high skin deposition and low permeability are required, such as in the case of topical antibacterial agents.

Photodynamic Cationic Ultrasmall Copper Oxide Nanoparticles-Loaded Liposomes for Alleviation of MRSA Biofilms

Introduction

As we enter the post-antibiotic era, the rise of antibiotic-resistant pathogenic bacteria is becoming a serious threat to public health. This problem is further complicated by antibiotic-resistant biofilms, for which current treatment options are limited.

Methods

To tackle this challenge, we propose a novel approach that involves the use of photodynamic cationic pH-sensitive liposomes loaded with ultra-small copper oxide (Ce6@Lipo/UCONs) to effectively eliminate drug-resistant bacteria and eradicate biofilms while minimizing safety concerns and the risk of resistance development.

Results

Our study demonstrates that Ce6@Lipo/UCONs have minimal toxicity to mammalian cells and can significantly enhance the association affinity with methicillin-resistant Staphylococcus aureus (MRSA) as confirmed by fluorescent microscope and flow cytometry, thereby greatly improving the bactericidal effect against planktonic MRSA. The cationic nature of Ce6@Lipo/UCONs also enables them to penetrate MRSA biofilms and respond to the acidic microenvironment within the biofilm, effectively releasing the loaded UCONs. Our results indicate that Ce6@Lipo/UCONs could effectively eliminate biofilms under light irradiation conditions, as evidenced by both biomass analysis and scanning electron microscopy observations. In addition, significant antibacterial effects and abscess healing were observed in MRSA-infected mice treated with Ce6@Lipo/UCONs upon light irradiation, while good biocompatibility was achieved in vivo.

Conclusion

Taken together, our findings suggest that photodynamic cationic ultrasmall copper oxide nanoparticles-loaded liposomes are a highly promising nano platform for combating antibiotic-resistant microbial pathogens and biofilms. The effective biofilm penetration and synergistic effect between photodynamic inactivation and metal sterilization make them a valuable tool for overcoming the challenges posed by antibiotic resistance.

Advances of liposomal mediated nanocarriers for the treatment of dermatophyte infections

Due to the adverse effects associated with long-term administration of antifungal drugs used for treating dermatophytic lesions like tinea unguium, there is a critical need for novel antifungal therapies that exhibit improved absorption and minimal adverse effects. Nanoformulations offer a promising solution in this regard. Topical formulations may penetrate the upper layers of the skin, such as the stratum corneum, and release an appropriate amount of drugs in therapeutic quantities. Liposomes, particularly nanosized ones, used as topical medication delivery systems for the skin, may have various roles depending on their size, lipid and cholesterol content, ingredient percentage, lamellarity, and surface charge. Liposomes can enhance permeability through the stratum corneum, minimize systemic effects due to their localizing properties, and overcome various challenges in cutaneous drug delivery. Antifungal medications encapsulated in liposomes, including fluconazole, ketoconazole, croconazole, econazole, terbinafine hydrochloride, tolnaftate, and miconazole, have demonstrated improved skin penetration and localization. This review discusses the traditional treatment of dermatophytes and liposomal formulations. Additionally, promising liposomal formulations that may soon be available in the market are introduced. The objective of this review is to provide a comprehensive understanding of dermatophyte infections and the role of liposomes in enhancing treatment.

Endocytosis-mediated redistribution of antibiotics targets intracellular bacteria

The increasing emergence and dissemination of antibiotic resistance pose a severe threat to overwhelming healthcare practices worldwide. The lack of new antibacterial drugs urgently calls for alternative therapeutic strategies to combat multidrug-resistant (MDR) bacterial pathogens, especially those that survive and replicate in host cells, causing relapse and recurrence of infections. Intracellular drug delivery is a direct efficient strategy to combat invasive pathogens by increasing the accumulation of antibiotics. However, the increased accumulation of antibiotics in the infected host cells does not mean high efficacy. The difficulty of treatment lies in the efficient intracellular delivery of antibiotics to the pathogen-containing compartments. Here, we first briefly review the survival mechanisms of intracellular bacteria to facilitate the exploration of potential antibacterial targets for precise delivery. Furthermore, we provide an overview of endocytosis-mediated drug delivery systems, including the biomedical and physicochemical properties modulating the endocytosis and intracellular redistribution of antibiotics. Lastly, we summarize the targets and payloads of recently described intracellular delivery systems and their modes of action against diverse pathogenic bacteria-associated infections. This overview of endocytosis-mediated redistribution of antibiotics sheds light on the development of novel delivery platforms and alternative strategies to combat intracellular bacterial pathogens.

Development of Nanoemulsions for Topical Application of Mupirocin

Mupirocin (MUP) is a topical antibacterial agent used to treat superficial skin infections but has limited application due to in vivo inactivation and plasma protein binding. A nanoemulsion formulation has the potential to enhance the delivery of mupirocin into the skin. MUP-loaded nanoemulsions were prepared using eucalyptus oil (EO) or eucalyptol (EU), Tween^® 80 (T80) and Span^® 80 (S80) as oil phase (O), surfactant (S) and cosurfactant (CoS). The nanoemulsions were characterised and their potential to enhance delivery was assessed using an in vitro skin model. Optimised nanoemulsion formulations were prepared based on EO (MUP-NE EO) and EU (MUP-NE EU) separately. MUP-NE EO had a smaller size with mean droplet diameter of 35.89 ± 0.68 nm and narrower particle size index (PDI) 0.10 ± 0.02 nm compared to MUP-NE EU. Both nanoemulsion formulations were stable at 25 °C for three months with the ability to enhance the transdermal permeation of MUP as compared to the control, Bactroban^® cream. Inclusion of EU led to a two-fold increase in permeation of MUP compared to the control, while EO increased the percentage by 48% compared to the control. Additionally, more MUP was detected in the skin after 8 h following MUP-NE EU application, although MUP deposition from MUP-NE EO was higher after 24 h. It may be possible, through choice of essential oil to design nanoformulations for both acute and prophylactic management of topical infections.

Localized Delivery of Bioactives using Structured Liposomal Gels

Liposomes have gained a lot of interest for drug delivery applications, and some of these preparations have been commercialized. These are formulated with biocompatible components and can be used for delivering a wide range of payloads differing in aqueous solubility and molecular weight. Liposome-based delivery approaches are limited mainly by two factors: (a) poor dispersion stability, and (b) pre-mature leakage of payloads. In this review, we have discussed the stabilization of liposomal vesicles by their entrapment in hydrogels. Studies reveal that such hydrogels can maintain the structural integrity of liposomes. Release of liposomes from the hydrogel network can be modulated through careful screening of matrix former and degree of its cross-linking. Accordingly, we have reviewed the approaches of stabilizing liposomal vesicles through entrapment in hydrogels. Application of liposome-embedded hydrogels has been reviewed in context of localized drug delivery. Our discussion is focussed on the delivery of bioactives to the skin. Such an approach appears alluring from the standpoint of minimizing the undesirable distribution of payload(s) the systemic circulation and off-target sites.

Optimization, Characterization and In Vivo Evaluation of Mupirocin Nanocrystals for Topical Administration

Treatment of infectious skin conditions resulting from wounds and burns with topical antibiotics is challenging, particularly those caused by methicillin-resistant Staphylococcus aureus bacteria (MRSA). This is due to the formation of bacterial biofilms characterized by antimicrobial resistance. Mupirocin (MP), a widely used topical antibiotic, is active against gram-positive bacteria including MRSA. However, MP suffers from sub-optimal therapeutic efficacy due to its poor water-solubility and the significant rise in MP-resistant S. aureus. In this study, the physico-chemical characteristics of MP were modified through nanocrystallization to improve its therapeutic efficacy for the treatment of skin infections. Mupirocin-nanocrystals (MP-NC) were prepared using a nanoprecipitation technique and optimized using a D-optimal response surface design. The optimization of MP-NC produced ultra-small monodisperse spherical particles with a mean diameter of 70 nm and a polydispersity index of 0.2. The design resulted in two optimal MP-NC formulations that were evaluated by performing series of in vitro, ex vivo, microbiological, and in vivo studies. In-vitro results showed a 10-fold increase in the saturation solubility and a 9-fold increase in the dissolution rate of MP-NC. Ex vivo permeation studies, using pig ears skin, showed a 2-fold increase in the dermal deposition of MP-NC with the highest drug deposition occurring at 500-µm skin depth. Moreover, the optimal MP-NC formulations were lyophilized and incorporated into a 2% w/w cream. Microbiological studies revealed a 16-fold decrease in the minimum inhibitory concentration and the minimum bactericidal concentration of MP-NC. In vivo studies, using a rat excision burn wound model, demonstrated rapid and complete healing of infected burn wounds in rats treated with MP-NC cream in comparison to marketed Avoban ointment. Our results suggest that nanocrystallization of MP may provide an avenue through which higher levels of a topically applied MP can be permeated into the skin to reach relevant infectious areas and exert potential local antibacterial effects.

Antibiotic-loaded lipid-based nanocarrier: a promising strategy to overcome bacterial infection

According to the World Health Organization (WHO) and Centers for Disease Control and Prevention (CDC), bacterial infections are one of the greatest threats to global health, food production, and life expectancy. In this sense, the development of innovative formulations aiming at greater therapeutic efficacy, safety, and shorter treatment duration compared to conventional products is urgently needed. Lipid-based nanocarriers (LBNs) have demonstrated the potential to enhance the effectiveness of available antibiotics. Among them, liposome, nanoemulsion, solid lipid nanoparticle (SLN), and nanostructured lipid carrier (NLC) are the most promising due to their solid technical background for laboratory and industrial production. This review describes recent advances in developing antibiotic-loaded LBNs against susceptible and resistant bacterial strains and biofilm. LBNs revealed to be a promising alternative to deliver antibiotics due to their superior characteristics compared to conventional preparations, including their modified drug release, improved bioavailability, drug protection against chemical or enzymatic degradation, greater drug loading capacity, and biocompatibility. Antibiotic-loaded LBNs can improve current clinical drug therapy, bring innovative products and rescue discarded antibiotics. Thus, antibiotic-loaded LBNs have potential to open a window of opportunities to continue saving millions of lives and prevent the devastating impact of bacterial infection.

Application of Nanomaterials in the Prevention, Detection, and Treatment of Methicillin-Resistant Staphylococcus aureus (MRSA)

Due to differences in geographic surveillance systems, chemical sanitization practices, and antibiotic stewardship (AS) implementation employed during the COVID-19 pandemic, many experts have expressed concerns regarding a future surge in global antimicrobial resistance (AMR). A potential beneficiary of these differences is the Gram-positive bacteria MRSA. MRSA is a bacterial pathogen with a high potential for mutational resistance, allowing it to engage various AMR mechanisms circumventing conventional antibiotic therapies and the host’s immune response. Coupled with a lack of novel FDA-approved antibiotics reaching the clinic, the onus is on researchers to develop alternative treatment tools to mitigate against an increase in pathogenic resistance. Mitigation strategies can take the form of synthetic or biomimetic nanomaterials/vesicles employed in vaccines, rapid diagnostics, antibiotic delivery, and nanotherapeutics. This review seeks to discuss the current potential of the aforementioned nanomaterials in detecting and treating MRSA.

Synthesis And Evaluation of Polyethylene Glycol-4000-Co-Poly (AMPS) Based Hydrogel Membranes for Controlled Release of Mupirocin for Efficient Wound Healing

BACKGROUND

Chronic wound healing is a major challenge for health care system around the globe. Current study was conducted to develop and characterize chemically cross-linked polyethylene glycol-co-poly (AMPS) hydrogel membranes to enhanced the wound healing efficiency of antibiotic mupirocin (MP).

METHODS

Free radical polymerization technique was used for the development of hydrogel membranes. In aqueous medium, polymer PEG-4000 cross-linked with the monomer 2-acrylamido-2-methylpropane sulfonic acid (AMPS) in the presence of initiators ammonium peroxide sulfate (APS) and sodium hydrogen sulfite (SHS). N, N-Methylenebisacrylamide (MBA) was used as cross-linker in the preparation of hydrogel membranes. Developed membranes were spherical, transparent, and elastic. FTIR, TGA/DSC, and SEM were used to characterize the polymeric system. Swelling behavior, drug loading, and its release pattern at pH of 5.5 and 7.4, irritation study, ex vivo drug permeation, and deposition study was also evaluated.

RESULTS

Formed membranes were spherical, transparent and elastic. The formation of a stable polymeric network was confirmed by structural and thermal analysis. Permeation of the drug its deposition in the skin showed good permeation and retention. No irritancy to the skin was observed.

CONCLUSION

On the basis of results obtained, the present study concluded that it may be an ideal network for the delivery of mupirocin in skin infections.

Bioactivity of Mupirocin Nanoparticle-Loaded Hydrogel against Methicillin-Resistant Staphylococcus aureus (MRSA)

This novel study investigated the loading of mupirocin nanoparticles into a hydrogel which was expected to enhance the antibacterial activity of mupirocin. The inhibition of isoleucyl-tRNA synthetase and global gene expression in methicillin-resistant Staphylococcus aureus (MRSA) by the mupirocin nanoparticle-loaded hydrogel (MLH) and by pure mupirocin was compared. MLH and mupirocin rapidly inhibited the growth of bacterial populations after 1 h of treatment. At 12 h, mupirocin and MLH inhibited isoleucyl-tRNA synthetase in MRSA. Transcriptome profiles of MRSA showed that gene expression alterations after treatment with mupirocin were similar to those after treatment with MLH at MICs. These alterations included changes to DNA transcription, translation, and replication pathways, and the fold changes in these genes decreased more rapidly with MLH than with mupirocin only after 1 h of treatment. MLH released the mupirocin from the nanoparticles and hydrogel systems and then the drug permeated the cell wall and bound to bacterial isoleucyl-tRNA synthetase. The research also showed that MLH could be further developed for use in clinics for infected wounds.

Mupirocin-Loaded Chitosan Microspheres Embedded in Piper betle Extract Containing Collagen Scaffold Accelerate Wound Healing Activity

This study reports the formulation of mupirocin-loaded chitosan microspheres embedded in Piper betle extract containing collagen scaffold as combinational drug delivery for improved wound healing. Selection of chitosan type (molecular weight and degree of deacetylation) was carried out based on their antibacterial efficacy. The low molecular weight chitosan was selected owing to the highest antibacterial action against gram-positive as well as gram-negative bacteria. Low molecular weight chitosan-microspheres showed spherical shape with largely smooth surface morphology, 11.81% of mupirocin loading, and its controlled release profile. The XRD, DSC thermograms, and FT-IR spectral analysis revealed the mupirocin loaded in molecularly dispersed or in amorphous form, and having no chemical interactions with the chitosan matrix, respectively. The in vivo study indicates potential effect of the mupirocin, Piper betle, and chitosan in the collagen scaffold in the wound healing efficiency with approximately 90% wound healing observed at the end of 15 days of study for combinational drug-loaded chitosan microspheres-collagen scaffold-treated group. The histopathology examination further revealed tissue lined by stratified squamous epithelium, collagen deposition, fibroblastic proliferation, and absence of inflammation indicating relatively efficient wound healing once treated with combinational drug-loaded chitosan microspheres containing scaffold.

Therapeutic Potential of Injectable Nano-Mupirocin Liposomes for Infections Involving Multidrug-Resistant Bacteria

Antibiotic resistance is a global health threat. There are a few antibiotics under development, and even fewer with new modes of action and no cross-resistance to established antibiotics. Accordingly, reformulation of old antibiotics to overcome resistance is attractive. Nano-mupirocin is a PEGylated nano-liposomal formulation of mupirocin, potentially enabling parenteral use in deep infections, as previously demonstrated in several animal models. Here, we describe extensive in vitro profiling of mupirocin and Nano-mupirocin and correlate the resulting MIC data with the pharmacokinetic profiles seen for Nano-mupirocin in a rat model. Nano-mupirocin showed no cross-resistance with other antibiotics and retained full activity against vancomycin-, daptomycin-, linezolid- and methicillin- resistant Staphylococcus aureus, against vancomycin-resistant Enterococcus faecium, and cephalosporin-resistant Neisseria gonorrhoeae. Following Nano-mupirocin injection to rats, plasma levels greatly exceeded relevant MICs for >24 h, and a biodistribution study in mice showed that mupirocin concentrations in vaginal secretions greatly exceeded the MIC₉₀ for N. gonorrhoeae (0.03 µg/mL) for >24 h. In summary, Nano-mupirocin has excellent potential for treatment of several infection types involving multiresistant bacteria. It has the concomitant benefits from utilizing an established antibiotic and liposomes of the same size and lipid composition as Doxil^®, an anticancer drug product now used for the treatment of over 700,000 patients globally.

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.

Bioinspired drug delivery strategies for repurposing conventional antibiotics against intracellular infections

Bacteria have developed a wealth of strategies to avoid and resist the action of antibiotics, one of which involves pathogens invading and forming reservoirs within host cells. Due to the poor cell membrane permeability, stability and retention of conventional antibiotics, this renders current treatments largely ineffective, since achieving a therapeutically relevant antibiotic concentration at the site of intracellular infection is not possible. To overcome such challenges, current antibiotics are 'repurposed' via reformulation using micro- or nano-carrier systems that effectively encapsulate and deliver therapeutics across cellular membranes of infected cells. Bioinspired materials that imitate the uptake of biological particulates and release antibiotics in response to natural stimuli are recently explored to improve the targeting and specificity of this 'nanoantibiotic' approach. In this review, the mechanisms of internalization and survival of intracellular bacteria are elucidated, effectively accentuating the current treatment challenges for intracellular infections and the implications for repurposing conventional antibiotics. Key case studies of nanoantibiotics that have drawn inspiration from natural biological particles and cellular uptake pathways to effectively eradicate intracellular pathogens are detailed, clearly highlighting the rational for harnessing bioinspired drug delivery strategies.

Direct interactions between cationic liposomes and bacterial cells ameliorate the systemic treatment of invasive multidrug-resistant Staphylococcus aureus infections

Invasive infections caused by antibiotic-resistant Staphylococcus aureus have posed a great threat to human health. To tackle this problem, a cationic liposomal Curcumin (C-LS/Cur) was developed and its effect against antibiotic-resistant S. aureus was investigated in this study. As expected, C-LS/Cur exhibited greater bactericidal capacity compared with its counterparts, probably because the negatively charged S. aureus favors electrostatic interactions rather than intercalation with cationic liposomal vesicles at the beginning of endocytic process, thereby effectively delivering Cur to its targets. We confirmed this hypothesis by monitoring zeta potential variation, collecting visual evidences through CLSM, FCM and TEM, and determining binding kinetics by BLI. Moreover, an excellent therapeutic efficacy of C-LS/Cur against invasive murine infection was also observed, which was due to the enhanced accumulation and retention in the targets. Therefore, cationic liposomes have great potential for the clinical application in the treatment of invasive antibiotic-resistant S. aureus infections.

(p)ppGpp/GTP and Malonyl-CoA Modulate Staphylococcus aureus Adaptation to FASII Antibiotics and Provide a Basis for Synergistic Bi-Therapy

Staphylococcus aureus is a major human bacterial pathogen for which new inhibitors are urgently needed. Antibiotic development has centered on the fatty acid synthesis (FASII) pathway, which provides the building blocks for bacterial membrane phospholipids.

Fatty acid biosynthesis (FASII) enzymes are considered valid targets for antimicrobial drug development against the human pathogen Staphylococcus aureus. However, incorporation of host fatty acids confers FASII antibiotic adaptation that compromises prospective treatments. S. aureus adapts to FASII inhibitors by first entering a nonreplicative latency period, followed by outgrowth. Here, we used transcriptional fusions and direct metabolite measurements to investigate the factors that dictate the duration of latency prior to outgrowth. We show that stringent response induction leads to repression of FASII and phospholipid synthesis genes. (p)ppGpp induction inhibits synthesis of malonyl-CoA, a molecule that derepresses FapR, a key regulator of FASII and phospholipid synthesis. Anti-FASII treatment also triggers transient expression of (p)ppGpp-regulated genes during the anti-FASII latency phase, with concomitant repression of FapR regulon expression. These effects are reversed upon outgrowth. GTP depletion, a known consequence of the stringent response, also occurs during FASII latency, and is proposed as the common signal linking these responses. We next showed that anti-FASII treatment shifts malonyl-CoA distribution between its interactants FapR and FabD, toward FapR, increasing expression of the phospholipid synthesis genes plsX and plsC during outgrowth. We conclude that components of the stringent response dictate malonyl-CoA availability in S. aureus FASII regulation, and contribute to latency prior to anti-FASII-adapted outgrowth. A combinatory approach, coupling a (p)ppGpp inducer and an anti-FASII, blocks S. aureus outgrowth, opening perspectives for bi-therapy treatment.

Endoplasmic reticulum-targeted glutathione and pH dual responsive vitamin lipid nanovesicles for tocopheryl DM1 delivery and cancer therapy

The major drawbacks of the cytotoxin like DM1 are the off-target effects. Here, the targeting nanovesicles were developed by synthesizing tocopherol-SS-DM1 and conjugating a pH low insertion peptide (pHLIP) to PEGylated phospholipids, in which tocopherol-SS-DM1 improves the drug loading and is glutathione responsive in the cytoplasm, meanwhile, the pH insertion peptide targets the acidic microenvironment of cancer cells. Besides, these nanovesicles can accumulate at the endoplasmic reticulum and show increased cancer therapeutic effects both in vitro and in vivo. These targeting nanovesicles provide a novel formulation for subcellular organelle targeting, a platform for precisely delivery of cytotoxic DM1 to cancer cells, and an alternative strategy for antibody-drug conjugates (ADCs).

Programmable antibiotic delivery to combat methicillin-resistant Staphylococcus aureus through precision therapy

The rapid dissemination of life-threatening multidrug-resistant bacterial pathogens calls for the development of new antibacterial agents and alternative strategies. The virulence factor secreted by bacteria plays a crucial role in the sophisticated processes during infections. Inspired by the unique capacity of many bacteria inducing clotting of plasma to initiate colonization, we propose a programmable antibiotic delivery system for precision therapy using methicillin-resistant S. aureus (MRSA) as a model. Coagulase utilized by MRSA to directly cleave fibrinogen into fibrin, is an ideal target not only for tracking bacterial status but for triggering the collapse of fibrinogen functionalized porous microspheres. Subsequently, staphylokinase, another virulence factor of MRSA, catalyzed hydrolysis of fibrin to further release the encapsulated antibiotics from microspheres. Our sequential triggered-release system exhibits high selectivity to distinguish live or dead MRSA from other pathogenic bacteria. Furthermore, such programmable microspheres clear 99% MRSA in 4 h, and show increased efficiency in a wound healing model in rats. Our study provides a programmable drug delivery system to precisely target bacterial pathogens using their intrinsic enzymatic cascades. This programmable platform with reduced selective stress of antibiotics on microbiota sheds light on the potential therapy for future clinical applications.

Opportunities and challenges in commercial pharmaceutical liposome applications

In the 1980s, the center of entrepreneurial activity for the application of liposome science to medicine took the form of a company called Vestar Inc. (which became NeXstar Pharmaceuticals Inc., and eventually a division of Gilead Sciences, with merger and acquisition activity). This company was formed from science initially developed at the California Institute of Technology and the City of Hope, and involving several other local academic and treatment centers. This company eventually produced two commercial liposomal therapeutics, and created a particular paradigm of formulation goals, formulation development, characterization, and production unique among the set of companies that emerged around the same time. A number of clinical candidates were also developed, but failed to achieve commercialization. Nevertheless, several of these provide still relevant lessons and guidance for the field. Key adaptations of this technology to lower cost applications have also been carried out and are examined.