TAT-modified self-assembled cationic peptide nanoparticles as an efficient antibacterial agent

AMP-Coated TiO2 Doped ZnO Nanomaterials Enhanced Antimicrobial Activity and Efficacy in Otitis Media Treatment by Elevating Hydroxyl Radical Levels

Background

In the past decades, antimicrobial resistance (AMR) has been a major threat to global public health. Long-term, chronic otitis media is becoming more challenging to treat, thus the novel antibiotic alternative agents are much needed.

Methods

ZnO@TiO2@AMP (ATZ NPs) were synthesized through a solvothermal method and subjected to comprehensive characterization. The in vitro and in vivo antibacterial effect and biocompatibility of ATZ NPs were evaluated. For the antibacterial mechanism exploration, we utilized the Electron Paramagnetic Resonance (EPR) Spectrometer to detect and analyze the hydroxyl radicals produced by ATZ NPs.

Results

ATZ NPs exhibited a spherical structure of 99.85 nm, the drug-loading rate for ZnO was 20.73%, and AMP within ATZ NPs was 41.86%. Notably, the Minimum Inhibitory Concentration (MIC) value of ATZ NPs against Staphylococcus aureus (S. aureus), methicillin-resistant Staphylococcus aureus (MRSA), and Streptococcus pneumoniae (S. pneumoniae) were 10 μg/mL, and Minimum Bactericidal Concentration (MBC) value of ATZ NPs against S. aureus, and S. pneumoniae were 50 μg/mL. In comparison to the model group, the treatment of otitis media with ATZ NPs significantly reduces inflammatory exudation in the middle ear cavity, with no observable damage to the tympanic membrane. Both in vivo and in vitro toxicity tests indicating the good biocompatibility of ATZ NPs. Moreover, EPR spectroscopy results highlighted the superior ability of ATZ NPs to generate hydroxyl radicals (·OH) compared to ZnO NPs.

Conclusion

ATZ NPs exhibited remarkable antibacterial properties both in vivo and in vitro. This innovative application of advanced ATZ NPs, bringing great promise for the treatment of otitis media.

An Overview of Supramolecular Platforms Boosting Drug Delivery

Numerous supramolecular platforms inspired by natural self-assembly are exploited as drug delivery systems. The spontaneous arrangement of single building blocks into inorganic and organic structures is determined and controlled by noncovalent forces such as electrostatic interactions, π-π interactions, hydrogen bonds, and van der Waals interactions. This review describes the main structures and characteristics of several building blocks used to obtain stable, self-assembling nanostructures tailored for numerous biological applications. Owing to their versatility, biocompatibility, and controllability, these nanostructures find application in diverse fields ranging from drug/gene delivery, theranostics, tissue engineering, and nanoelectronics. Herein, we described the different approaches used to design and functionalize these nanomaterials to obtain selective drug delivery in a specific disease. In particular, the review highlights the efficiency of these supramolecular structures in applications related to infectious diseases and cancer.

Mechanism and antibacterial synergies of poly(Dabco-BBAC) nanoparticles against multi-drug resistant Pseudomonas aeruginosa isolates from human burns

Multi-drug resistant bacteria are a major problem in the treatment of infectious diseases, such as pneumonia, meningitis, or even coronavirus disease 2019 (COVID-19). Cationic nanopolymers are a new type of antimicrobial agent with high efficiency. We synthesized and characterized cationic polymer based on 1,4-diazabicyclo [2.2.2] octane (DABCO) and Bis (bromoacetyl)cystamine (BBAC), named poly (DABCO-BBAC) nanoparticles(NPs), and produced 150 nm diameter NPs. The antibacterial activity of poly (DABCO-BBAC) against eight multi drug resistant (MDR) Pseudomonas aeruginosa isolates from human burns, its possible synergistic effect with gentamicin, and the mechanism of action were examined. Poly(DABCO-BBAC) could effectively inhibit and kill bacterial strains at a very low concentration calculated by minimum inhibitory concentration (MIC) assay. Nevertheless, its synergism index with gentamicin showed an indifferent effect. Moreover, transmission electron microscopy and lipid peroxidation assays showed that poly (DABCO-BBAC) distorted and damaged the bacterial cell wall. These results suggest that the poly (DABCO-BBAC) could be an effective antibacterial agent for MDR clinical pathogens.

Adaptive Responses of a Peroxidase-like Polyoxometalate-Based Tri-Assembly to Bacterial Microenvironment (BME) Significantly Improved the Anti-Bacterial Effects

The present study presents the tertiary assembly of a POM, peptide, and biogenic amine, which is a concept to construct new hybrid bio-inorganic materials for antibacterial applications and will help to promote the development of antivirus agents in the future. To achieve this, a Eu-containing polyoxometalate (EuW₁₀) was first co-assembled with a biogenic amine of spermine (Spm), which improved both the luminescence and antibacterial effect of EuW₁₀. Further introduction of a basic peptide from HPV E6, GL-22, induced more extensive enhancements, both of them being attributed to the cooperation and synergistic effects between the constituents, particularly the adaptive responses of assembly to the bacterial microenvironment (BME). Further intrinsic mechanism investigations revealed in detail that the encapsulation of EuW₁₀ in Spm and further GL-22 enhanced the uptake abilities of EuW₁₀ in bacteria, which further improved the ROS generation in BME via the abundant H₂O₂ involved there and significantly promoted the antibacterial effects.

Recent Nanotechnologies to Overcome the Bacterial Biofilm Matrix Barriers

Bacterial biofilm-related infectious diseases severely influence human health. Under typical situations, pathogens can colonize inert or biological surfaces and form biofilms. Biofilms are functional aggregates that coat bacteria with extracellular polymeric substances (EPS). The main reason for the failure of biofilm infection treatment is the low permeability and enrichment of therapeutic agents within the biofilm, which results from the particular features of biofilm matrix barriers such as negatively charged biofilm components and highly viscous compact EPS structures. Hence, developing novel therapeutic strategies with enhanced biofilm penetrability is crucial. Herein, the current progress of nanotechnology methods to improve therapeutic agents' penetrability against biofilm matrix, such as regulating material morphology and surface properties, utilizing the physical penetration of nano/micromotors or microneedle patches, and equipping nanoparticles with EPS degradation enzymes or signal molecules, is first summarized. Finally, the challenges, perspectives, and future implementations of engineered delivery systems to manage biofilm infections are presented in detail.

Degradable Selenium-Containing Polymers for Low Cytotoxic Antibacterial Materials

Developing biodegradable cationic polymers with high antibacterial efficiency and low cytotoxicity is of great significance in biological applications. Selenium is an essential trace element for the human body, and selenium-containing compounds are promising in various health-related applications. To combine selenium with biodegradability, selenide-functionalized polycaprolactones (PCL) with different hydrophobic substituents were synthesized followed by selenoniumization. The optimal polyselenonium salt showed excellent antibacterial activity with an MBC of 2 μg mL^-1 and an MIC of 1 μg mL^-1 and exhibited good biocompatibility before and after degradation. In addition, the obtained selenium polymer can be well blended with commercial PCL by electrospinning, and films with good antibacterial activity were prepared. This work enriches the knowledge of selenium derivatives and lays a foundation for follow-up research on selenium cationic polymers in the antimicrobial field.

Self-Assembled Cationic Nanoparticles Combined with Curcumin against Multidrug-Resistant Bacteria

The overuse of antibiotics exacerbates the development of antibiotic-resistant bacteria, threatening global public health, while most traditional antibiotics act on specific targets and sterilize through chemical modes. Therefore, it is a desperate need to design novel therapeutics or extraordinary strategies to overcome resistant bacteria. Herein, we report a positively charged nanocomposite PNs-Cur with a hydrodynamic diameter of 289.6 nm, which was fabricated by ring-opening polymerization of ε-caprolactone and Z-Lys-N-carboxyanhydrides (NCAs), and then natural curcumin was loaded onto the PCL core of PNs with a nanostructure through self-assembly, identified through UV-vis, and characterized by scanning electron microscopy (SEM) and dynamic light scattering (DLS). Especially, the self-assembly dynamics of PNs was simulated through molecular modeling to confirm the formation of a core-shell nanostructure. Biological assays revealed that PNs-Cur possessed broad-spectrum and efficient antibacterial activities against both Gram-positive and Gram-negative bacteria, including drug-resistant clinical bacteria and fungus, with MIC values in the range of 8-32 μg/mL. Also, in vivo evaluation showed that PNs-Cur exhibited strong antibacterial activities in infected mice. Importantly, the nanocomposite did not indeed induce the emergence of drug-resistant bacterial strains even after 21 passages, especially showing low toxicity regardless of in vivo or in vitro. The study of the antibacterial mechanism indicated that PNs-Cur could indeed destruct membrane potential, change the membrane potential, and cause the leakage of the cytoplasm. Concurrently, the released curcumin further plays a bactericidal role, eventually leading to bacterial irreversible apoptosis. This unique bacterial mode that PNs-Cur possesses may be the reason why it is not easy to make the bacteria susceptible to easily produce drug resistance. Overall, the constructed PNs-Cur is a promising antibacterial material, which provides a novel strategy to develop efficient antibacterial materials and combat increasingly prevalent bacterial infections.

Staphylococcus aureus-targeting peptide/surfactant assemblies for antibacterial therapy

To address the challenge from microbial resistance, this work developed a surfactant with 18-carbon single hydrocarbon chain and multi-amine head groups (C18N3). After assembling with Staphylococcus aureus-targeting peptide (CARG), the obtained C18N3/CARG assemblies exhibited excellent antimicrobial activities against Staphylococcus aureus and methicillin-resistant Staphylococcus aureus in vitro and in vivo, in which the targeting peptide CARG bonded specifically to Staphylococcus aureus and C18N3 killed bacteria with a mechanism of membrane disruption. Importantly, C18N3 could also work as a β-lactamase inhibitor to overcome the bacterial resistance to β-lactam antibiotics through noncompetitive inhibition. The combination of β-lactam antibiotic and C18N3/CARG assemblies more effectively suppressed methicillin-resistant Staphylococcus aureus in vitro and in vivo relative to equivalent dose of free antibiotic or C18N3. Thus, the antibacterial platform of antibiotic-carrying surfactant assemblies bearing bacteria-targeted peptides, in which C18N3 performed dual function, antibacterial agent and β-lactamase inhibitor, may help fight against the difficult-to-treat infections.

Strategies to Improve the Activity and Biocompatibility: Modification of Peptide Antibiotics

As host defense peptides, peptide antibiotics exist in almost all organisms. Many of their activities come from their inactivation of bacteria, yeast, fungi, and even cancer cells. However, natural peptide antibiotics are relatively poor in stability and penetration, and have high hemolytic properties, which makes them difficult to directly apply. Therefore, natural peptide antibiotics can be modified to enhance their activity and biocompatibility. Based on the characteristics of amino acids, amino acid substitutions can be performed to study the effect of amino acid types on the activity of peptide antibiotics. The design of ultrashort peptides, cyclic peptides, and self-assembling peptides is also a way to improve the activity of peptide antibiotics. In addition, antibacterial peptides can also be conjugated with antibiotics, lipids, or metal ions to prepare antibacterial peptides with special activities. This review introduces several methods for modifying peptide antibiotics and their specific applications, providing a theoretical basis for the further application of peptide antibiotics.

Cyclic peptides nanospheres: A '2-in-1' self-assembled delivery system for targeting nucleus and cytoplasm

Vascular endothelial growth factor (VEGF) is considered as one of the vital growth factors for angiogenesis, which is primarily responsible for the progress and maintenance of new vascular network in tumor. Numerous studies report that inhibition of VEGF-induced angiogenesis is a potent technique for cancer suppression. Recently, RNA interference, especially small interfering RNA (siRNA) signified a promising approach to suppress the gene expression. However, the clinical implementation of biological macromolecules such as siRNA is significantly limited because of stability and bioavailability issues. Herein, self-assembled peptide nanospheres have been generated from L,L-cyclic peptides using hydrophobic (Trp), positively charged (Arg) and cysteine (Cys) amino acid residues and demonstrated as vehicles for intracellular delivery of VEGF siRNA and VEGF antisense oligonucleotide. Formation of peptide nanostructures is confirmed by HR-TEM, AFM, SEM and DLS analysis. Possible mechanism of self-assembly of the cyclic peptides and their binding with macromolecules are demonstrated by in-silico analysis. Gel electrophoresis reveals that the newly generated peptide based organic materials exhibit strong binding affinity toward siRNAs / antisense oligonucleotides (ASOs) at optimum concentration. Flow cytometry and confocal microscopy results confirm the efficiency of the new biomaterials toward the intracellular delivery of fluorescent labeled siRNA / ASOs. Furthermore, VEGF expression evaluated by western blot and RT-PCR upon the delivery of functional VEGF siRNA/ASOs suggests that very low concentrations of VEGF siRNA/ASOs cause significant gene knockdown at protein and mRNA levels, respectively.

Antimicrobial peptide-based materials: opportunities and challenges

The multifunctional properties of antimicrobial peptides (AMPs) make them attractive candidates for the treatment of various diseases. AMPs are considered alternatives to antibiotics due to the rising number of multidrug-resistant...

Antibacterial, antibiofilm, anti-inflammatory, and wound healing effects of nanoscale multifunctional cationic alternating copolymers

Infectious diseases caused by new or unknown bacteria and viruses, such as anthrax, cholera, tuberculosis and even COVID-19, are a major threat to humanity. Thus, the development of new synthetic compounds with efficient antimicrobial activity is a necessity. Herein, rationally designed novel multifunctional cationic alternating copolymers were directly synthesized through a step-growth polymerization reaction using a bivalent electrophilic cross-linker containing disulfide bonds and a diamine heterocyclic ring. To optimize the activity of these alternating copolymers, several different diamines and cross-linkers were explored to find the highest antibacterial effects. The synthesized nanopolymers not only displayed good to excellent antibacterial activity as judged by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa, and Escherichia coli, but also reduced the number of biofilm cells even at low concentrations, without killing mammalian cells. Furthermore, in vivo experiments using infected burn wounds in mice demonstrated good antibacterial activity and stimulated wound healing, without causing systemic inflammation. These findings suggest that the multifunctional cationic nanopolymers have potential as a novel antibacterial agent for eradication of multidrug resistant bacterial infections.

Water-soluble PANI:PSS designed for spontaneous non-disruptive membrane penetration and direct intracellular photothermal damage on bacteria

The major challenge in the field of antibacterial agents is to overcome the low-permeability of bacteria cell membranes that protects the cells against diverse drugs. In this work, water-soluble polyaniline (PANI)-poly (p-styrenesulfonic acid) (PSS) (PANI:PSS) is found to spontaneously penetrate bacteria cellular membranes in a non-disruptive way, leaving no evidence of membrane poration/disturbance or cell death, thus avoiding side effects caused by cationic ammonia groups in traditional ammonia-containing antibacterial agents. For aqueous synthesis, which is important for biocompatibility, the polymer is synthesized via an enzyme-mimetic route relying on the catalysis of a nanozyme. Owing to its fluorescent properties, the localization of as-prepared PANI:PSS is determined by the confocal microscope, and the results confirm its rapid entry into bacteria. Under 808 nm near-infrared (NIR) irradiation, the internalized PANI:PSS generates local hyperthermia and destroys bacteria highly efficiently from inside the cells due to its excellent photothermal effects. Staphylococcus aureus (S. aureus), M ethicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli (E. coli) could be effectively eliminated as well as the corresponding bacterial biofilms. Results of in vivo antibacterial experiments demonstrate excellent antibacterial activities of the water-soluble PANI:PSS without side effects. Therefore, the prepared water-soluble polymer in this study has great potential in the treatment of various bacterial infections.

Comparative study of an antimicrobial peptide and a neuropeptide conjugated with gold nanorods for the targeted photothermal killing of bacteria

There are certain disadvantages in treating bacterial infections through conventional methods. For this reason, the current study does focus on combating bacterial wound infections by photothermal therapy assisted by gold nanorod-peptide conjugates (GNR-peptide conjugates). Two peptides, the cationic antimicrobial peptide LL-37 and neuropeptide ANGIOPEP-2 both with specificity for targeted bacterial binding, were conjugated with GNR surface through electrostatic interactions. The GNR-peptide conjugates showed good biocompatibility, sufficient stability, enhanced targeting, potential photothermal killing of bacteria, and possible acceleration of wound healing. The photo-biomodulation properties of NIR improved the wound closure rates through enhanced cell migration. The multifunctional LL37-conjugated GNRs significantly enhanced photothermal therapeutic outcomes based on bacterial targeting with promising wound healing properties.

Membrane-disruptive peptides/peptidomimetics-based therapeutics: Promising systems to combat bacteria and cancer in the drug-resistant era

Membrane-disruptive peptides/peptidomimetics (MDPs) are antimicrobials or anticarcinogens that present a general killing mechanism through the physical disruption of cell membranes, in contrast to conventional chemotherapeutic drugs, which act on precise targets such as DNA or specific enzymes. Owing to their rapid action, broad-spectrum activity, and mechanisms of action that potentially hinder the development of resistance, MDPs have been increasingly considered as future therapeutics in the drug-resistant era. Recently, growing experimental evidence has demonstrated that MDPs can also be utilized as adjuvants to enhance the therapeutic effects of other agents. In this review, we evaluate the literature around the broad-spectrum antimicrobial properties and anticancer activity of MDPs, and summarize the current development and mechanisms of MDPs alone or in combination with other agents. Notably, this review highlights recent advances in the design of various MDP-based drug delivery systems that can improve the therapeutic effect of MDPs, minimize side effects, and promote the co-delivery of multiple chemotherapeutics, for more efficient antimicrobial and anticancer therapy.

Nanostructured Antimicrobial Peptides: Crucial Steps of Overcoming the Bottleneck for Clinics

The security issue of human health is faced with dispiriting threats from multidrug-resistant bacteria infections induced by the abuse and misuse of antibiotics. Over decades, the antimicrobial peptides (AMPs) hold great promise as a viable alternative to treatment with antibiotics due to their peculiar antimicrobial mechanisms of action, broad-spectrum antimicrobial activity, lower drug residue, and ease of synthesis and modification. However, they universally express a series of disadvantages that hinder their potential application in the biomedical field (e.g., low bioavailability, poor protease resistance, and high cytotoxicity) and extremely waste the abundant resources of AMP database discovered over the decades. For all these reasons, the nanostructured antimicrobial peptides (Ns-AMPs), based on a variety of nanosystem modification, have made up for the deficiencies and pushed the development of novel AMP-based antimicrobial therapies. In this review, we provide an overview of the advantages of Ns-AMPs in improving therapeutic efficacy and biological stability, reducing side effects, and gaining the effect of organic targeting and drug controlled release. Then the different material categories of Ns-AMPs are described, including inorganic material nanosystems containing AMPs, organic material nanosystems containing AMPs, and self-assembled AMPs. Additionally, this review focuses on the Ns-AMPs for the effect of biological activities, with emphasis on antimicrobial activity, biosecurity, and biological stability. The "state-of-the-art" antimicrobial modes of Ns-AMPs, including controlled release of AMPs under a specific environment or intrinsic antimicrobial properties of Ns-AMPs, are also explicated. Finally, the perspectives and conclusions of the current research in this field are also summarized.

Nanoparticles and nanoformulated drugs as promising delivery system in treatment of microbial-induced CNS infection: a systematic review of literature

Central nervous system (CNS) infection is a global health problem with high rate of mortality and associated morbidities. Viruses, bacteria, fungi, and protozoa parasites are the main cause of CNS infection. Various medications are currently used for treatment of brain infections, but most of them do not have enough efficiency because the majority of conventional drugs cannot pass the blood-brain barrier (BBB) to combat the pathogens. Nanotechnology has provided promising approaches to solve this issue, since nanoparticles (NPs) can facilitate the drugs entrance through the BBB. Herein, we systematically reviewed all available literature to provide evidences for practicality of NPs in treatment of CNS infection. A systematic literature search was performed on January 29, 2021, in Web of Science, PubMed, Scopus, Science Direct, Embase, Ovid, and Google Scholar using "CNS infections" and "NPs/nanoformulation" including all their equivalent terms as keyword. Due to lack of human studies, no strict inclusion criteria were defined, and all relevant documents were included. After several steps of article selection, a total of 29 documents were collected and used for data synthesis. The results showed that drug-loaded NPs is fairly safe and can be a promising approach in developing anti-infective agents for treatment of CNS infection, since nanoformulated drugs could act up to tenfold more efficient that drug alone. Findings of this review indicate the importance of NPs and nanoformulation of drugs to enhance the efficiency of treatment and warrant the safety of treatment in human studies; however, clinical trials are required to confirm such efficiency and safety in clinical practice.

Physiological and Pathological Factors Affecting Drug Delivery to the Brain by Nanoparticles

The prevalence of neurological/neurodegenerative diseases, such as Alzheimer's disease is known to be increasing due to an aging population and is anticipated to further grow in the decades ahead. The treatment of brain diseases is challenging partly due to the inaccessibility of therapeutic agents to the brain. An increasingly important observation is that the physiology of the brain alters during many brain diseases, and aging adds even more to the complexity of the disease. There is a notion that the permeability of the blood-brain barrier (BBB) increases with aging or disease, however, the body has a defense mechanism that still retains the separation of the brain from harmful chemicals in the blood. This makes drug delivery to the diseased brain, even more challenging and complex task. Here, the physiological changes to the diseased brain and aged brain are covered in the context of drug delivery to the brain using nanoparticles. Also, recent and novel approaches are discussed for the delivery of therapeutic agents to the diseased brain using nanoparticle based or magnetic resonance imaging guided systems. Furthermore, the complement activation, toxicity, and immunogenicity of brain targeting nanoparticles as well as novel in vitro BBB models are discussed.

The Effects of Luminescent CdSe Quantum Dot-Functionalized Antimicrobial Peptides Nanoparticles on Antibacterial Activity and Molecular Mechanism

BACKGROUND

With the development of bacterial resistance, the range of effective antibiotics is increasingly becoming more limited. The effective use of nanoscale antimicrobial peptides (AP) in therapeutic and diagnostic methods is a strategy for new antibiotics.

METHODS

Combining both AP and cadmium selenide (CdSe) into a composite material may result in a reagent with novel properties, such as enhanced antibacterial activity, fluorescence and favorable stability in aqueous solution.

RESULTS

AP-loaded CdSe NPs (AP-CdSe NPs) showed strong antibacterial activity against multidrug-resistant (MDR) Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in vitro and in vivo. Colony-forming unit (CFU) and minimum inhibitory concentration (MIC) assays showed that AP-CdSe NPs have highly effective antibacterial activity. The quantitative analysis of apoptosis by flow cytometry analysis further confirmed that MDR E. coli and S. aureus treated with AP-CdSe NPs had death rates of 98.76% and 99.13%, respectively. Also, AP-CdSe NPs was found to inhibit bacterial activity in an in vivo bacteremia model in mice infected with S. aureus. In addition, the antibacterial mechanism of AP-CdSe NPs was determined by RNA sequencing analysis. Gene ontology (GO) analysis and Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis revealed the molecular mechanism of the antibacterial effect of AP-CdSe NPs. Importantly, histopathology analysis, and hematological toxicity analysis indicated that AP-CdSe NPs had few side effects.

CONCLUSION

These results demonstrate that AP loaded on CdSe NPs had a higher water solubility, bioavailability and antibacterial effect compared with raw AP. This study reports findings that are helpful for the design and development of antibacterial treatment strategies based on AP.

Conjugating Peptides onto 1D Rodlike Bionanoparticles for Enhanced Activity against Gram-Negative Bacteria

Gram-negative bacteria, which possess an impermeable outer membrane, are responsible for many untreatable infections. The lack of development of new relevant antibiotics for over 50 years has increased threats. Peptides are regarded as the most promising alternatives to antibiotics. However, since the activities of existing peptides are not yet comparable to those of current antibiotics, there is an urgent need to improve their antibacterial efficiencies. Herein, we conjugate peptides onto one-dimensional rod-like tobacco mosaic virus (TMV). The peptides on the obtained nanoparticles (peptide-TMV) are hundreds of times superior to free peptides in combating Gram-negative bacteria. Through morphology and gene detection of Escherichia coli, it was revealed that following peptide-TMV application, the high osmotic pressure related to membrane damage and the generated reactive oxygen species cause Escherichia coli's death. In addition, peptide-TMV causes a downregulation of biofilm-related genes, inhibiting biofilm formation. This work paves the way to combat Gram-negative bacteria-related infection.

A Review of Bioactive Peptides: Chemical Modification, Structural Characterization and Therapeutic Applications

In recent years, the development and applications of protein drugs have attracted extensive attention from researchers. However, the shortcomings of protein drugs also limit their further development. Therefore, bioactive peptides isolated or simulated from protein polymers have broad application prospects in food, medicine, biotechnology, and other industries. Such peptides have a molecular weight distribution between 180 and 1000 Da. As a small molecule substance, bioactive peptide is usually degraded by various enzymes in the organism and have a short half-life. At the same time, such substances have poor stability and are difficult to produce and store. Therefore, these active peptides may be modified through phosphorylation, glycosylation, and acylation. Compared with other protein drugs, the modified active peptides are more easily absorbed by the body, have longer half-life, stronger targeting, and fewer side effects in addition to higher bioavailability. In the light of their functions, bioactive peptide can be divided into antimicrobial, anti-tumour, anti-angiogenic, antioxidant, anti-fatigue, and anti-hypertensive peptides. This article mainly focuses on the introduction of several promising biologically active peptides functioning as antimicrobial, anti-tumour, antiangiogenic, and antioxidant peptides from the three aspects modification, structural characteristics and mechanism of action.

Combating drug-resistant bacterial infection using biodegradable nanoparticles assembled from comb-like polycarbonates grafted with amphiphilic polyquaternium

Bacterial infection is a serious clinical threat. The misuse of antibiotics has already resulted in the emergence of antibiotic-resistant strains of pathogenic bacteria. Efficient membrane-destructive antibacterial agents are considered as an alternative, promising solution against bacterial infection. Herein, we prepared a new type of comb-like cationic, polyethylene glycol (PEG) block polycarbonates with polyquaternium arms (G-CgQAs). The amphiphilic G-CgQAs could self-assemble into about 60 nm sized nanoparticles (NPs) with positive charges (20~30 mV). G-CgQA-3 NPs with an appropriate hydrophobic-hydrophilic balance in the polyquaternium arms showed antibacterial activity against Gram-negative, Gram-positive, and drug-resistant strains at low concentrations (MIC 64-128 μg mL-1) and low hemolysis (HC50 > 2000 μg mL-1). In vivo anti-infection tests indicated G-CgQA-3 NPs could highly inhibit the growth of vancomycin-resistant bacteria by spraying on wounds. Collectively, G-CgQA NPs hold great promise for the prevention of infection, serving as new antibacterial agents. This study also highlights the significance of a hydrophobic block in positive polyquaternium arms to facilitate the antibacterial activity of cationic, quaternized polymers. The design of comb-like amphiphilic cationic polycarbonates provides a new method for manufacturing antibacterial nano-agents.

The Use of Nanobiotechnology in Immunology and Vaccination

Nanotechnology uses the unique properties of nanostructures with a size of 1 to 200 nanometers. Different nanoparticles have shown great promise for the production of new vaccines and drugs. Nanostructures can be used to deliver immunological compounds more effectively than microstructures to target sites. Different nanostructures can be applied to form a new generation of vaccines, adjuvants, and immune system drugs. The goal of nanotechnology is to better respond to a wide range of infectious and non-infectious diseases.

Combining Antimicrobial Peptides with Nanotechnology: An Emerging Field in Theranostics

The emergence of multidrug-resistant pathogens and their rapid adaptation against new antibiotics is a major challenge for scientists and medical professionals. Different approaches have been taken to combat this problem, which includes rationally designed potent antimicrobial peptides (AMPs) and several nanoparticles and quantum dots. AMPs are considered as a new generation of super antibiotics that hold enormous potential to fight against bacterial resistance by the rapidly killing planktonic as well as their biofilm form while keeping low toxicity profile against eukaryotic cells. Various nanoparticles and quantum dots have proved their effectiveness against a vast array of infections and diseases. Conjugation and functionalization of nanoparticles with potentially active antimicrobial peptides have added advantages that widen their applications in the field of drug discovery as well as delivery system including imaging and diagnostics. This article reviews the current progress and implementation of different nanoparticles and quantum dots conjugated antimicrobial peptides in terms of bio-stability, drug delivery, and therapeutic applications.

Progress in the Application of Nanoparticles and Graphene as Drug Carriers and on the Diagnosis of Brain Infections

The blood–brain barrier (BBB) is the protective sheath around the brain that protects the sensitive microenvironments of the brain. However, certain pathogens, viruses, and bacteria disrupt the endothelial barrier and cause infection and hence inflammation in meninges. Macromolecular therapeutics are unable to cross the tight junctions, thereby limiting their bioavailability in the brain. Recently, nanotechnology has brought a revolution in the field of drug delivery in brain infections. The nanostructures have high targeting accuracy and specificity to the receptors in the case of active targeting, which have made them the ideal cargoes to permeate across the BBB. In addition, nanomaterials with biomimetic functions have been introduced to efficiently cross the BBB to be engulfed by the pathogens. This review focuses on the nanotechnology-based drug delivery approaches for exploration in brain infections, including meningitis. Viruses, bacteria, fungi, or, rarely, protozoa or parasites may be the cause of brain infections. Moreover, inflammation of the meninges, called meningitis, is presently diagnosed using laboratory and imaging tests. Despite attempts to improve diagnostic instruments for brain infections and meningitis, due to its complicated and multidimensional nature and lack of successful diagnosis, meningitis appears almost untreatable. Potential for overcoming the difficulties and limitations related to conventional diagnostics has been shown by nanoparticles (NPs). Nanomedicine now offers new methods and perspectives to improve our knowledge of meningitis and can potentially give meningitis patients new hope. Here, we review traditional diagnosis tools and key nanoparticles (Au-NPs, graphene, carbon nanotubes (CNTs), QDs, etc.) for early diagnosis of brain infections and meningitis.

The Inclusion of a Matrix Metalloproteinase-9 Responsive Sequence in Self-assembled Peptide-based Brain-Targeting Nanoparticles Improves the Efficiency of Nanoparticles Crossing the Blood-Brain Barrier at Elevated MMP-9 Levels

This study investigated whether the inclusion of a matrix metalloproteinase-9 (MMP-9) responsive sequence in self-assembled peptide-based brain-targeting nanoparticles (NPs) would enhance the blood-brain barrier (BBB) penetration when MMP-9 levels are elevated both in the brain and blood circulation. Brain-targeting peptides were conjugated at the N-terminus to MMP-9-responsive peptides, and these were conjugated at the N-terminus to lipid moiety (cholesteryl chloroformate or palmitic acid). Two constructs did not have MMP-9-responsive peptides. NPs were characterised for size, charge, critical micelle concentration, toxicity, blood compatibility, neural cell uptake, release profiles, and in vitro BBB permeability simulating normal or elevated MMP-9 levels. The inclusion of MMP-9-sensitive sequences did not improve the release of a model drug in the presence of active MMP-9 from NPs compared to distilled water. ¹⁹F NMR studies suggested the burial of MMP-9-sensitive sequences inside the NPs making them inaccessible to MMP-9. Only cholesterol-GGGCKAPETALC (responsive to MMP-9) NPs showed <5% haemolysis, <1 pg/mL release of IL-1β at 500 μg/mL from THP1 cells, with 70.75 ± 5.78% of NPs crossing the BBB at 24 h in presence of active MMP-9. In conclusion, brain-targeting NPs showed higher transport across the BBB model when MMP-9 levels were elevated and the brain-targeting ligand was responsive to MMP-9.

The cell structure damage and embden-meyerhof-parnas pathway inhibition of Listeria monocytogenes induced by glycinin basic peptide

Glycinin basic peptide (GBP) is a natural antibacterial peptide. This study aimed to explore the antibacterial characteristics of GBP against Listeria monocytogenes (L. monocytogenes) by measuring the membrane potential, membrane permeability, cell damage, morphological changes, respiration metabolism inhibition and DNA content. GBP increased the surface zeta potential and decreased the trans-membrane potential of L. monocytogenes in a dose-dependent manner. Compared with the control, the electrical conductivities of GBP-treated bacterial suspensions were significantly increased. The percentages of bacteria with damaged membrane increased from 6.40% to 70.90% with GBP from 0 to 0.8 mg/mL. Obvious rupture and deform of bacterial cells with GBP were observed by transmission electron microscope (TEM), showing the destructive effect of GBP on L. monocytogenes. GBP also inhibited the embden-meyerhof-parnas pathway of the bacterial respiration metabolism and reduced the activities of its key regulator enzymes. Besides, the content of DNA in GBP-treated L. monocytogenes was lower than that in control.

Self-assembled peptide nanoparticles for efficient delivery of methotrexate into cancer cells

The low cellular uptake of Methotrexate (MTX), a commonly used anticancer drug, is a big challenge for efficient cancer therapy. Self-assembled peptide nanoparticles (SAPNs) are one of the major classes of peptide vectors that have gained much attention toward novel drug delivery systems. In the present study, different sequences of cell-penetrating peptides including R2W4R2 and W3R4W3 and their SAPNs (R2W4R2-E12 and W3R4W3-E12) were designed for efficient delivery of MTX into MCF7 breast cancer cells. Based on electron microscopy results, the obtained SAPNs were in nano scale with spherical shape. There was a positive relationship between the free energy of water to octanol transferring and cellular penetration of designed nanostructures. The R2W4R2 possessed proper free energy and ability to form a spherical structure and hydrophobic-hydrophobic interactions, therefore, exhibited more cellular penetration than W3R4W3. The cellular uptake of obtained nanoparticles was examined by flow cytometry and fluorescence microscopy, in which, R2W4R2 and R2W4R2-E12 showed more appropriate penetration into MCF7 cells than W3R4W3 and W3R4W3-E12. The cytotoxicity of MTX-loaded peptides and SAPNs was examined by MTT assay. As a result, at higher concentrations, the R2W4R2 and R2W4R2-E12 showed higher cytotoxic behavior than their counterparts. Despite their enhanced cellular internalization, the cytotoxic behavior of MTX-loaded SAPNs at lower concentrations was relatively less than free MTX, which could be ascribed to the gradual nature of drug detachment from these conjugates. Therefore, R2W4R2 could be considered as an efficient choice to enhance the therapeutic efficiency of MTX in cancer treatments.

Preparation And Antibacterial Effects Of Carboxymethyl Chitosan-Modified Photo-Responsive Camellia Sapogenin Derivative Cationic Liposomes

BACKGROUND

Bacterial resistance to antibiotics is a persistent and intractable problem. The sapogenin isolated from the seeds of Camellia oleifera can inhibit antibiotic-resistant bacteria after structural modification.

PURPOSE

This study aims to improve sapogenin's antibacterial activity and avoid bacterial resistance based on nano-preparation with photo responsiveness.

METHODS

The liposome shell material of carboxymethyl chitosan-phosphatidyl ethanolamine (CMC-PE) was prepared using amidation reaction, and photo-responsive cationic (PCC) liposomes containing Camellia sapogenin derivative (CSD) and photosensitizer pheophorbide-a were prepared by film dispersion method. Encapsulation efficiency, drug loading, zeta potential, particle size distribution, morphology and stability of the PCC liposomes were determined by HPLC, particle size analyzer, transmission electron microscopy (TEM) and fluorescence microscopy. Photo-responsive release of CSD in the PCC liposomes was determined by laser (0.5 mW/cm2) at 665 nm. Antibacterial activity of the PCC liposomes with or without irradiation was analyzed by MIC50, MBC, MBIC50, and bacterial morphology to evaluate the antibacterial effects on amoxicillin resistant Escherichia coli and Staphylococcus aureus.

RESULTS

Size distribution, zeta potential, encapsulation efficiency and drug loading of the PCC liposomes were 189.23 ± 2.12 nm, 18.80 ± 1.57 mV, 83.52 ± 1.53% and 2.83 ± 0.05%, respectively. The PCC liposomes had higher storage stability and gastrointestinal stability, and no obvious hemolytic toxicity to rabbit red blood cells and no cytotoxicity after incubation with Hela cells. The photosensitizer pheophorbide-a was uniformly dispersed in the phospholipid layer of the PCC liposomes and increased the CSD release after irradiation. The PCC liposomes could bind to bacteria and impaired their morphology and structure, and had significant bactericidal effect on amoxicillin resistant E. coli and S. aureus.

CONCLUSION

The photo-responsive PCC liposomes are efficient antibacterial agents for avoidance of bacterial resistance against antibiotics.

Doxorubicin combined with betulinic acid or lonidamine in RGD ligand-targeted pH-sensitive micellar system for ovarian cancer treatment

Synergistic combination therapy involving the integration of chemotherapeutics and chemosensitizers into micelles has demonstrated great potential for tumor-specific location release. Here, the natural product betulinic acid (BA) and chemical drug lonidamine (LN) were used as chemosensitizers in combination with doxorubicin (DOX) for ovarian cancer treatment. We designed pH-sensitive peptide derivatives and constructed an all-in-one multifunctional multidrug pH-sensitive targeting delivery system for the synergistic co-delivery of DOX and BA (or LN). The combination of DOX and BA was found to elicit better therapeutic effects and lower cardiotoxicity than the DOX and LN combination in Skvo3 cells. Further, loading DOX/BA into the present micellar systems enabled burst release at the tumor location, leading to enhanced anti-tumor effects and reduced off-target effects. More importantly, DOX/BA micelles elicited fewer adverse effects on cardiac function and leukocyte counts in Skvo3 subcutaneous xenograft models. These features suggest that the designed micelles represent a promising multifunctional strategy for the efficient treatment of ovarian cancer.

Self-Assembled Nanoparticles of Symmetrical Cationic Peptide Against Citrus Pathogenic Bacteria

The increasing drug resistance of phytopathogenic bacteria to conventional bactericides has driven the necessity for exploring new alternatives with a lower tendency to develop bacterial resistance. Here, we report a novel cationic symmetrical peptide P₅VP₅ (Ac- R+ LI R+ K+ V K+ R+ IL R+ -NH₂ that enables self-assembly to form nanoparticles with excellent thermal stability. An in vitro assay showed that P₅VP₅ nanoparticles exhibited excellent antibacterial activity against Xanthomonas axonopodis pv citri with a MIC value of 20 μM. Meanwhile, under an in planta condition, treatment with peptide nanoparticles demonstrated the highest ability to reduce the development of citrus canker lesions in leaves. Moreover, the nanoparticles could destroy the biofilm formation, damage the cell membranes, and affect the cell membrane permeability, ultimately leading to the death of bacteria. Taken together, these nanoparticles are a promising antibacterial agent that can be used to control citrus canker and other plant diseases caused by bacteria.

A New Hope: Self-Assembling Peptides with Antimicrobial Activity

Peptide drugs hold great promise for the treatment of infectious diseases thanks to their novel mechanisms of action, low toxicity, high specificity, and ease of synthesis and modification. Naturally developing self-assembly in nature has inspired remarkable interest in self-assembly of peptides to functional nanomaterials. As a matter of fact, their structural, mechanical, and functional advantages, plus their high bio-compatibility and bio-degradability make them excellent candidates for facilitating biomedical applications. This review focuses on the self-assembly of peptides for the fabrication of antibacterial nanomaterials holding great interest for substituting antibiotics, with emphasis on strategies to achieve nano-architectures of self-assembly. The antibacterial activities achieved by these nanomaterials are also described.

Construction, mechanism, and antibacterial resistance insight into polypeptide-based nanoparticles

Demonstration of the bactericidal mechanism of self-assembled nanoparticles.

Designing dual-functionalized carbon nanotubes with high blood–brain-barrier permeability for precise orthotopic glioma therapy

Herein we synthesize a cell penetrating peptide- and cancer-targeted molecule-functionalized multi-walled carbon nanotube for precise orthotopic glioma therapy.

Self-Assembled Antimicrobial Nanomaterials

Nanotechnology came to stay improving the quality of human life by reducing environmental contamination of earth and water with pathogens. This review discusses how self-assembled antimicrobial nanomaterials can contribute to maintain humans, their water and their environment inside safe boundaries to human life even though some of these nanomaterials display an overt toxicity. At the core of their strategic use, the self-assembled antimicrobial nanomaterials exhibit optimal and biomimetic organization leading to activity at low doses of their toxic components. Antimicrobial bilayer fragments, bilayer-covered or multilayered nanoparticles, functionalized inorganic or organic polymeric materials, coatings and hydrogels disclose their potential for environmental and public health applications in this review.

Emerging Nanomedicine Therapies to Counter the Rise of Methicillin-Resistant Staphylococcus aureus

In a recent report, the World Health Organisation (WHO) classified antibiotic resistance as one of the greatest threats to global health, food security, and development. Methicillin-resistant Staphylococcus aureus (MRSA) remains at the core of this threat, with persistent and resilient strains detectable in up to 90% of S. aureus infections. Unfortunately, there is a lack of novel antibiotics reaching the clinic to address the significant morbidity and mortality that MRSA is responsible for. Recently, nanomedicine strategies have emerged as a promising therapy to combat the rise of MRSA. However, these approaches have been wide-ranging in design, with few attempts to compare studies across scientific and clinical disciplines. This review seeks to reconcile this discrepancy in the literature, with specific focus on the mechanisms of MRSA infection and how they can be exploited by bioactive molecules that are delivered by nanomedicines, in addition to utilisation of the nanomaterials themselves as antibacterial agents. Finally, we discuss targeting MRSA biofilms using nano-patterning technologies and comment on future opportunities and challenges for MRSA treatment using nanomedicine.