Combining functionalities-nanoarchitectonics for combatting bacterial infection

New antimicrobial and anti-inflammatory therapeutics are needed because of antibiotic resistance development and resulting complications such as inflammation, ultimately leading to septic shock. The antimicrobial effects of various nanoparticles (NPs) are currently attracting intensive research interest. Although various NPs display potent antimicrobial effects against strains resistant to conventional antibiotics, the therapeutic use of such materials is restricted by poor selectivity between bacteria and human cells, leading to adverse side effects. As a result, increasing research efforts during the last few years have focused on targeting NPs against bacteria and other components in the infection micro-environment. Examples of approaches explored include peptide-, protein- and nucleic acid-based NP coatings for bacterial membrane recognition, as well as NP conjugation with enzyme substrates or other moieties that respond to bacterial or other enzymes present in the infection micro-environment. In general, this study aims to add to the literature on the antimicrobial effects of nanomaterials by discussing surface modification strategies for targeting bacterial membranes and membrane components, as well as how such surface modifications can improve the antimicrobial effects of nanomaterials and simultaneously decrease toxicity towards human cells and tissues. In doing so, the biological effects observed are related throughout to the physico-chemical modes of action underlying such effects.

Rapid Membrane-Penetrating Hybrid Peptides Achieve Efficient Dual Antimicrobial and Antibiofilm Activity through a Triple Bactericidal Mechanism

Antimicrobial peptides (AMPs) are a type of biomaterial used against multidrug resistant (MDR) bacteria. This study reports the design of a peptide family rich in tryptophan and lysine obtained by optimizing a natural AMP using single factor modification and pheromone hybridization to expedite the penetration and improve the antimicrobial activity of AMPs. S-4, L-4, and P-4 showed α-helical structures, exhibited extremely fast membrane penetration rates in vitro, and could kill MDR bacteria efficiently within 30 min. Intracellular fluorescence localization suggested rapid membrane-penetrating of AMPs within 1 min, making it more difficult for bacteria to develop resistance. Furthermore, they could effectively inhibit and destroy bacterial biofilms with dual antimicrobial and antibiofilm activity. In the treatment of skin infections caused by MDR-Acinetobacter baumannii in vivo , AMPs could effectively alleviate inflammation without toxic side effects. Additionally, the triple antimicrobial damage of AMPs was described in detail. AMPs rapidly penetrate the cell membrane, inducing cell membrane damage, triggering oxidative damage with a storm of reactive oxygen species and leading to bacterial death through leakage of cellular contents by complexing with DNA. The multiple damage is an important means by which AMPs can prevent bacterial resistance adequately.

Chensinin-1b Alleviates DSS-Induced Inflammatory Bowel Disease by Inducing Macrophage Switching from the M1 to the M2 Phenotype

Inflammatory bowel disease (IBD) is a chronic relapsing inflammatory disorder with an increasing prevalence worldwide. Macrophage polarization is involved in the pathogenesis of IBD. Repolarization of macrophage has thus emerged as a novel therapeutic approach for managing IBD. Chensinin-1b, derived from the skin of Rana chensinensis, is a derivative of a native antimicrobial peptide (AMP). It shows anti-inflammatory effects in sepsis models and can potentially modulate macrophage polarization. The objective of this research was to study the role of chensinin-1b in macrophage polarization and dextran sulfate sodium (DSS)-induced colitis. RAW264.7 macrophages were polarized to the M1 phenotype using lipopolysaccharide (LPS) and simultaneously administered chensinin-1b at various concentrations. The ability of chenisnin-1b to reorient macrophage polarization was assessed by ELISA, qRT-PCR, and flow cytometry analysis. The addition of chensinin-1b significantly restrained the expression of M1-associated proinflammatory cytokines and surface markers, including TNF-α, IL-6, NO, and CD86, and exaggerated the expression of M2-associated anti-inflammatory cytokines and surface markers, including IL-10, TGF-β1, Arg-1, Fizz1, Chil3, and CD206. Mechanistically, via Western Blotting, we revealed that chensinin-1b induces macrophage polarization from the M1 to the M2 phenotype by inhibiting the phosphorylation of nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinase (MAPK). In mouse models of colitis, intraperitoneal administration of chensinin-1b alleviated symptoms induced by DSS, including weight loss, elevated disease activity index (DAI) scores, colon shortening, colonic tissue damage, and splenomegaly. Consistent with our in vitro data, chensinin-1b induced significant decreases in the expression of M1 phenotype biomarkers and increases in the expression of M2 phenotype biomarkers in the mouse colitis model. Furthermore, chensinin-1b treatment repressesed NF-κB phosphorylation in vivo. Overall, our data showed that chensinin-1b attenuates IBD by repolarizing macrophages from the M1 to the M2 phenotype, suggesting its potential as a therapeutic candidate for IBD.

Bioinformatics-Led Identification of Potential Biomarkers and Inflammatory Infiltrates in Burn Injury

Burn injury is a life-threatening disease with a poor prognosis. The immune change and underlying mechanisms remain largely unknown. Thus, this study aims to find potential biomarkers and analyze the immune infiltrates after burn injury. Gene expression data of burn patients were obtained from the Gene Expression Omnibus database. Key immune-related genes (IRGs) were screened by differential and least absolute shrinkage and selection operator (LASSO) regression analysis. Based on key IRGs, patients were divided into two clusters by consensus cluster analysis. Immune infiltration was analyzed by the single sample gene set enrichment analysis (GSEA) method and the immune score was calculated by the principal component analysis method. A nomogram model was constructed based on the calculated immune score and clinical features. Finally, the expression of screened key genes was validated by an external cohort and quantitative polymerase chain reaction experiment. Fifty-nine IRGs were differently expressed in burn patients. After LASSO regression analysis, 12 key genes remained, namely AZU1, OLR1, RNASE2, FGF13, NR1D2, NR2E1, TLR5, CAMP, DEFA4, PGLYRP1, CTSG, and CCR3. Then, patients were divided into two clusters. Immune infiltration analysis revealed that more immune cells were infiltrated and more pathways were activated in cluster A, in which patients showed high immune scores. Finally, a nomogram model was constructed and showed high accuracy and reliability. The expression pattern of 12 key genes in an external cohort and clinical samples was in accordance with the theoretical analysis results. In conclusion, this research elucidated the key role of immune response in burns and could be used as a guide for burn treatment.

Advances of Antimicrobial Peptide-Based Biomaterials for the Treatment of Bacterial Infections

Owing to the increase in multidrug-resistant bacterial isolates in hospitals globally and the lack of truly effective antimicrobial agents, antibiotic resistant bacterial infections have increased substantially. There is thus an urgent need to develop new antimicrobial drugs and their related formulations. In recent years, natural antimicrobial peptides (AMPs), AMP optimization, self-assembled AMPs, AMP hydrogels, and biomaterial-assisted delivery of AMPs have shown great potential in the treatment of bacterial infections. In this review, it is focused on the development prospects and shortcomings of various AMP-based biomaterials for treating animal model infections, such as abdominal, skin, and eye infections. It is hoped that this review will inspire further innovations in the design of AMP-based biomaterials for the treatment of bacterial infections and accelerate their commercialization.

Pharmaceutical nanotechnology: Antimicrobial peptides as potential new drugs against WHO list of critical, high, and medium priority bacteria

Nanobiotechnology is a relatively unexplored area that has, nevertheless, shown relevant results in the fight against some diseases. Antimicrobial peptides (AMPs) are biomacromolecules with potential activity against multi/extensively drug-resistant bacteria, with a lower risk of generating bacterial resistance. They can be considered an excellent biotechnological alternative to conventional drugs. However, the application of several AMPs to biological systems is hampered by their poor stability and lifetime, inactivating them completely. Therefore, nanotechnology plays an important role in the development of new AMP-based drugs, protecting and carrying the bioactive to the target. This is the first review article on the different reported nanosystems using AMPs against bacteria listed on the WHO priority list. The current shortage of information implies a nanobiotechnological potential to obtain new drugs or repurpose drugs based on the AMP-drug synergistic effect.

Liposomes encapsulating novel antimicrobial peptide Omiganan: Characterization and its pharmacodynamic evaluation in atopic dermatitis and psoriasis mice model

Omiganan is a novel 12 amino acid synthetic cationic peptide from the cathelicidin family. Omiganan possesses antimicrobial action against a wide range of microbes, including gram-positive and gram-negative bacteria and fungi. Omiganan mainly acts by depolarizing the cytoplasmic membrane, resulting in cellular disruption and death. Apart from its antimicrobial effect, Omiganan also has anti-inflammatory activity. The present investigation aimed to evaluate and compare the efficacy of Omiganan liposomal gel with conventional formulations (Omiganan gel and lotion) in atopic dermatitis (AD) and psoriasis mice animal models. Liposomes encapsulating Omiganan were prepared using the reverse-phase evaporation technique and incorporated into Carbopol 934P gel. The optimized Omiganan liposomes were then characterized for various physicochemical parameters such as vesicle size, shape and surface morphology, zeta-potential, rheological parameters, in-vitro drug release, ex-vivo skin permeation/deposition, in-vitro antimicrobial activity, proteolytic stability, and cellular toxicity and uptake studies. Liposomes exhibited 72 % encapsulation with 7.8 % loading efficacy, a vesicle size, and zeta potential of 120 nm and - 17.2 mv, respectively. Moreover, Omiganan liposomal gel demonstrated controlled release and a better permeation profile than conventional formulations. A substantial reduction in levels of pro-inflammatory cytokines and improvement in AD and psoriatic lesions were achieved by Omiganan liposomal gel compared to Omiganan gel and lotion-based formulations. The present study confirms that Omiganan liposomal formulation can be an effective, safe, and novel alternative treatment approach in atopic dermatitis and psoriasis.

Atomic-Resolution Structures and Mode of Action of Clinically Relevant Antimicrobial Peptides

Global rise of infections and deaths caused by drug-resistant bacterial pathogens are among the unmet medical needs. In an age of drying pipeline of novel antibiotics to treat bacterial infections, antimicrobial peptides (AMPs) are proven to be valid therapeutics modalities. Direct in vivo applications of many AMPs could be challenging; however, works are demonstrating encouraging results for some of them. In this review article, we discussed 3-D structures of potent AMPs e.g., polymyxin, thanatin, MSI, protegrin, OMPTA in complex with bacterial targets and their mode of actions. Studies on human peptide LL37 and de novo-designed peptides are also discussed. We have focused on AMPs which are effective against drug-resistant Gram-negative bacteria. Since treatment options for the infections caused by super bugs of Gram-negative bacteria are now extremely limited. We also summarize some of the pertinent challenges in the field of clinical trials of AMPs.

Amphibian-derived peptide homodimer promotes regeneration of skin wounds

Despite the increasing treatments in skin wound repair, existing therapeutic drugs cannot meet current needs. As such, skin wound repair remains a considerable clinical challenge, and thus the discovery of new pro-healing agents is crucial. Here, we identified the first naturally occurring peptide homodimer named as OA-GP11 dimer (OA-GP11d) from Odorrana andersonii (odorous frog) through the combinational methods of peptidomics and genomics. OA-GP11d was linked by the intramolecular disulfide formed by the 10^th cysteine residues from the monomer of peptide with sequence of GPLSGINAECM, which effectively promoted the repair of full-thickness and burn wounds in mice. The underlying molecular mechanisms revealed that OA-GP11d not only accelerated the migration and cell-scratch healing of mouse keratinocytes, but also activated the mitogen-activated protein kinases (MAPKs) signaling pathway (phosphorylation of p38 and ERK subgroups) in immortalized human keratinocytes (HaCaT). Besides, OA-GP11d reduced the phosphorylation of nuclear factor-κB (NF-κB) and inhibitor of NF-κB (I-κB) induced by lipopolysaccharide stimulation in mouse macrophages, and inhibited the release of associated inflammatory factors tumor necrosis factor (TNF)-α and interleukin (IL)-6. OA-GP11d is the first identified naturally occurring peptide dimer with significant pro-healing potency. Our results highlight the importance of amphibians as a source of novel pro-healing agents and suggest OA-GP11d as a potential new pro-regenerative drug candidate.

Therapeutic Effect of Darkling Beetle (Zophobas morio) Hemolymph on Skin Thermal Injury in Mice Infected by Staphylococcus haemolyticus

Staphylococci are the most common pathogens isolated from skin infections in livestock or companion animals. Antibiotic therapy is the best treatment for infections, but local or systemic use of antimicrobials increases the risk of bacterial resistance. Insects are rich in antimicrobial peptides, which can reduce bacterial resistance and can be used to treat bacterial infections after skin burns. We propose that the use of the darkling beetle (Z. morio) hemolymph to treat skin infections in mice by Staphylococcus haemolyticus is one of the alternatives. Z. morio hemolymph alleviated the increase in wound area temperature in mice with a skin infection, reduced the bacterial load of the wound, and accelerated the wound healing speed significantly. Pathological sections showed that Z. morio hemolymph can significantly reduce inflammatory cell infiltration, and promote skin tissue repair. Real-time fluorescent quantitative polymerase chain reaction (PCR) revealed that the Z. morio hemolymph can significantly reduce the levels of pro-inflammatory cytokines, including interleukin-1 beta (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and chemokine interleukin-8 (IL-8). Our findings suggest that Z. morio antibacterial hemolymph can promote wound contraction, relieve local inflammatory responses and promote wound healing in mice infected with a heat injury, which has a positive therapeutic effect and enormous potential for skin thermal injury.

Alternative Therapeutic Interventions: Antimicrobial Peptides and Small Molecules to Treat Microbial Keratitis

Microbial keratitis is a leading cause of blindness worldwide and results in unilateral vision loss in an estimated 2 million people per year. Bacteria and fungus are two main etiological agents that cause corneal ulcers. Although antibiotics and antifungals are commonly used to treat corneal infections, a clear trend with increasing resistance to these antimicrobials is emerging at rapid pace. Extensive research has been carried out to determine alternative therapeutic interventions, and antimicrobial peptides (AMPs) are increasingly recognized for their clinical potential in treating infections. Small molecules targeted against virulence factors of the pathogens and natural compounds are also explored to meet the challenges and growing demand for therapeutic agents. Here we review the potential of AMPs, small molecules, and natural compounds as alternative therapeutic interventions for the treatment of corneal infections to combat antimicrobial resistance. Additionally, we have also discussed about the different formats of drug delivery systems for optimal administration of drugs to treat microbial keratitis.

Nisin loaded carbopol gel against Pseudomonas aeruginosa infected third-degree burns: A therapeutic intervention

The emergence of multidrug resistant strains of Pseudomonas aeruginosa necessitates the exploration of novel therapeutic intervention (s). The present study aimed to develop a nisin loaded carbopol gel formulation (NLCG) and explore its therapeutic efficacy against P. aeruginosa infected burn wounds. The formulation was prepared using Carbopol 940 as a polymer and characterized in terms of its appearance, stability, pH, rheology, spreadability, release, and permeation profiles. Disc diffusion assay and field emission scanning electron microscopy were carried out to establish in vitro antibacterial activity while the in vitro cytotoxicity was evaluated by hemolytic and trypan blue exclusion assay. Furthermore, in vivo efficacy was investigated by developing P. aeruginosa infected third-degree murine burn wound model followed by evaluation of parameters like bacterial loads, skin restoration, histopathological architecture, levels of hydroxyproline, myeloperoxidase and cytokines. Our studies yielded a stable formulation with pH, viscosity and drug release flux values as 6.5 ± 0.02, 382.4 p and 160.55 ± 3.64 μg h^-1  cm^-2 , respectively. Approximately, 84.02 ± 1.63% of nisin was found to permeate into murine skin, further, affirmed by confocal microscopic observations. Interestingly, no in vitro cytotoxicity of NLCG (to erythrocytes and/or to peritoneal macrophages) could be observed. The log units decrease (s) in CFUs of Pseudomonas in skin were found to be 1.5137, 4.2257, 6.456 after 12, 24 and 72 h of topical gel therapy, respectively. Percentage wound closure, tensile strength, histological, and scanning electron microscopic studies further provided a healing evidence with skin showing restoration of the epithelium. The gel therapy also led to a significant modulation (p ≤ 0.05) in hydroxyproline content, myeloperoxidase levels, and serum levels of IL-1, IL-10, and TNF-α. Our formulation revealed anti-Pseudomonas, wound healing, and immunomodulatory efficacy of NLCG. Further investigations are warranted to determine the underlying mechanism (s) of these displayed antibacterial and immunomodulatory effects.

Formulation Development of Topical Preparation Containing Nanoparticles of Povidone-Iodine for Wound Healing

Povidone-iodine (PVI) is an antiseptic drug that is used for wound healing or for repair of the damaged tissue. Studies on solid lipid nanoparticles (SLNs) indicate that this system could potentially be used as a delivery system with improved drug entrapment efficiency and controlled drug release for hydrophilic actives. This study focuses on developing a topical gel containing SLNs of PVI for wound healing. SLNs were prepared by using the solvent emulsification diffusion method. Lipids such as glycerol monostearate, palmitic acid, and stearic acid, and surfactants such as polysorbate 80, soyalecithin, and Pluronic F-68 were used for the preparation of SLN. These were screened out based on particle size and entrapment efficiency of SLN. Gel was prepared by using Carbopol 940 (1% w/w) and propylene glycol (10% w/w). Formulated SLNs were evaluated by various in vitro and in vivo techniques. Based on the results, the drug-to-lipid ratio (1:3) and 2% polysorbate 80 (surfactant) along with stirring rate (3,000 rpm) produced the desired particle size (285.4 nm) with good stability. 22.85% drug loading and 88.83% drug entrapment efficiency were found in the optimized formulation. In vitro drug release shows that it follows the Korsmeyer-Peppas model. The animal study shows that the period of epithelization produced by the test group was 17.14 ± 1.35 days, which was near to that of the standard group (16.25 ± 1.24 days). Clinical Trial Registration number: 1044/PO/Re/S/07/CPCSEA.

A New Era of Antibiotics: The Clinical Potential of Antimicrobial Peptides

Antimicrobial resistance is a multifaceted crisis, imposing a serious threat to global health. The traditional antibiotic pipeline has been exhausted, prompting research into alternate antimicrobial strategies. Inspired by nature, antimicrobial peptides are rapidly gaining attention for their clinical potential as they present distinct advantages over traditional antibiotics. Antimicrobial peptides are found in all forms of life and demonstrate a pivotal role in the innate immune system. Many antimicrobial peptides are evolutionarily conserved, with limited propensity for resistance. Additionally, chemical modifications to the peptide backbone can be used to improve biological activity and stability and reduce toxicity. This review details the therapeutic potential of peptide-based antimicrobials, as well as the challenges needed to overcome in order for clinical translation. We explore the proposed mechanisms of activity, design of synthetic biomimics, and how this novel class of antimicrobial compound may address the need for effective antibiotics. Finally, we discuss commercially available peptide-based antimicrobials and antimicrobial peptides in clinical trials.

Innate Inspiration: Antifungal Peptides and Other Immunotherapeutics From the Host Immune Response

The purpose of this review is to describe antifungal therapeutic candidates in preclinical and clinical development derived from, or directly influenced by, the immune system, with a specific focus on antimicrobial peptides (AMP). Although the focus of this review is AMP with direct antimicrobial effects on fungi, we will also discuss compounds with direct antifungal activity, including monoclonal antibodies (mAb), as well as immunomodulatory molecules that can enhance the immune response to fungal infection, including immunomodulatory AMP, vaccines, checkpoint inhibitors, interferon and colony stimulating factors as well as immune cell therapies. The focus of this manuscript will be a non-exhaustive review of antifungal compounds in preclinical and clinical development that are based on the principles of immunology and the authors acknowledge the incredible amount of in vitro and in vivo work that has been conducted to develop such therapeutic candidates.

Antimicrobial peptides: a promising strategy for lung cancer drug discovery?

INTRODUCTION

Antimicrobial peptides (AMPs), also called host defense peptides (HDPs), are identified in almost any form of life, which play an important role in innate immune systems. They have a broad spectrum of antifungal, antiviral, antibacterial, and anticancer activities. Lung cancer remains the leading cause of global cancer-related death. Unfortunately, lung cancer chemotherapy is accompanied by serious side effects, nonspecific toxicity, and multidrug resistance. Hence, to overcome these drawbacks, anticancer peptides (ACPs) derived from AMPs may represent a potential promising synergistic treatment strategy for lung cancer.

AREAS COVERED

In this review, the authors provide the recent advancements in the use of AMPs for the treatment of lung cancer. Furthermore, the anti-lung cancer modes of action of these peptides have been fully reviewed. Importantly, various strategies for increasing the efficiency and safety of AMPs have been discussed.

EXPERT OPINION

The combination of AMPs and other cancer treatment approaches such as chemotherapy, nanoparticle-based delivery systems, and photodynamic therapy can be used as a promising revolutionary strategy for the treatment of lung cancer. The most significant limitations of this strategy that need to be focused on are low efficiency and off-target events.

Novel Therapeutics for the Treatment of Burn Infection

Background: Burn injury continues to be a significant cause of morbidity and death, with infectious complications being the primary cause of death. Patients are susceptible to overwhelming infection secondary to both the physical breakdown of the skin and mucosal barrier and the immune dysfunction that accompanies the inflammatory response to a major burn. With resistance to traditional antibiosis looming as a serious threat to patient outcome, advancement in the treatment of burn infections is imperative. Methods: Between February 15 and March 15, 2020, a search of Pubmed and clinicaltrials.gov was performed using search terms such as "burn immunotherapy," "therapeutic microorganisms in burn," "burn infection clinical trials," and applicable variations. Results: Topical antimicrobial drugs continue to be standard of care for burn wound injuries, but personalized and molecular treatments that rely on immune manipulation of the host show great promise. We discuss novel therapeutics for the treatment of burn infection: Probiotics and therapeutic microorganisms, immune modulators, tailored monoclonal antibodies, and extracellular vesicles and proteins. Conclusions: The treatment strategies discussed employ manipulation of structure and function in host immune cells and pathogen virulence for improved outcomes in burn infection.

Mini Review on Antimicrobial Peptides, Sources, Mechanism and Recent Applications

Antimicrobial peptides in recent years have gained increased interest among scientists, health professionals and the pharmaceutical companies owing to their therapeutic potential. These are low molecular weight proteins with broad range antimicrobial and immuno modulatory activities against infectious bacteria (Gram positive and Gram negative), viruses and fungi. Inability of micro-organisms to develop resistance against most of the antimicrobial peptide has made them as an efficient product which can greatly impact the new era of antimicrobials. In addition to this these peptides also demonstrates increased efficacy, high specificity, decreased drug interaction, low toxicity, biological diversity and direct attacking properties. Pharmaceutical industries are therefore conducting appropriate clinical trials to develop these peptides as potential therapeutic drugs. More than 60 peptide drugs have already reached the market and several hundreds of novel therapeutic peptides are in preclinical and clinical development. Rational designing can be used further to modify the chemical and physical properties of existing peptides. This mini review will discuss the sources, mechanism and recent therapeutic applications of antimicrobial peptides in treatment of infectious diseases.