Antimicrobial Peptides against Bacterial Pathogens: Innovative Delivery Nanosystems for Pharmaceutical Applications

Enhancing Implantable Medical Devices: Surface Functionalization of Titanium with Quaternary Ammonium Salts for Antibacterial Adhesion Properties

Bacterial colonization of titanium-based materials used in implantable medical devices represents a significant challenge in the dental and orthopedic fields, often leading to infections and implant failure. This study reports the surface modification of titanium discs with ammonium salts containing carbon atom chains of different lengths (from 6 to 12) to provide antibacterial properties to the modified metal surfaces while maintaining their biocompatibility. The chemically modified samples have been characterized by ATR-FTIR and SEM-EDX analyses and evaluated for roughness and hydrophilic behavior. This surface modification not only provides hydrophobic properties to titanium surfaces but also introduces a hindering environment for bacterial adhesion. Antibacterial tests performed against methicillin-sensitive and methicillin-resistant Staphylococcus aureus strains demonstrated a proportional increase in antibacterial activity with increasing carbon chain length. The best antibacterial performance is reported for the sample containing 12 carbon atoms (Ti-ADTEAB), which showed inhibition values of 87.5 and 86.6% for the sensitive and resistant strains, respectively. The results suggest that this surface modification could lead to a new generation of implantable medical devices with improved patient outcomes by reducing the risk of postoperative infections.

Biocompatible Black Phosphorus Nanosheets-Antimicrobial Peptide Nanocomposites for Enhanced Anti-Infection Therapy

Bacterial infections are one of the major problems affecting human health, which is exacerbated by increasing antibiotic resistance. Antimicrobial peptides (AMPs) are an ideal alternative to antibiotics, but their instability and toxicity to mammalian cells need to be addressed. Here, black phosphorus nanosheets (BPs) were successfully decorated with melittin (Mel), a kind of AMP, through electrostatic interaction. The size impacts of BPs on the antibacterial ability and biocompatibility of BPs/Mel nanocomposites were studied systematically. Results showed that the nanocomposites made from middle-sized BPs (BPs/Mel-7) have strong antibacterial ability as well as good biocompatibility. Moreover, BPs/Mel-7 could accelerate skin wound healing infected by Staphylococcus aureus. This study provides a facile strategy to expand the application of AMPs.

A chionodracine-derived peptide, KHS-Cnd, as an anti-virulence agent against multidrug-resistant Acinetobacter baumannii clinical strains

About 71% of healthcare-associated infections are due to antibiotic-resistant bacteria, such as carbapenem-resistant A. baumannii, classified by World Health Organization into a critical priority group of pathogens. The antimicrobial resistance profile of A. baumannii relies on its ability to produce several virulence factors, including biofilm formation. Its ability to adhere and persist on surfaces as biofilm has contributed to its pathogenicity and drug resistance. In this study, the ability of an antimicrobial peptide (a chionodracine-derived peptide named KHS-Cnd) to inhibit or reduce biofilm formation was investigated as an example of a potential strategy to counteract infections caused by biofilm-forming pathogens. To this aim, the antimicrobial profiles were first analyzed in selected A. baumannii strains, two reference and six clinical strains, all biofilm-forming with different capability, regardless of whether they are drug resistant or sensitive. Successively, we investigated the bactericidal activity of the peptide that showed MIC values ranging from 5 to 10 µM and a significative antibiofilm activity on all tested strains at sub-inhibitory concentrations. In fact, KHS-Cnd can hinder biofilm A. baumannii strains formation with an inhibition percentage ranging between 65% and 10%. Also a statistically significant reduction of mature biofilm ranging from 20% to 50% was observed in four out of eight tested A. baumannii strains. KHS-Cnd impacts various stages of biofilm formation, including the inhibition of surface-associated and twitching motilities depending on the different strain. In particular, our results showed that only two strains possessed surface-associated motility that was strongly impaired by KHS-Cnd treatment; three clinical strains, instead, showed twitching motility, whose inhibition for two of them was evident after 24 h of incubation with peptide. Moreover, the invasion of pulmonary cells by A. baumannii was significantly impaired with a reduction of about 32% after treatment with 1.25 µM KHS-Cnd. Finally, when the peptide was used together with ceftazidime/avibactam against resistant A. baumannii strains, it was able to reduce the minimal inhibitory concentration of antibiotics needed to inhibit the microorganism growth.

Decoding the Role of Antimicrobial Peptides in the Fight against Mycobacterium tuberculosis

Tuberculosis (TB), a leading infectious disease caused by the pathogen Mycobacterium tuberculosis, poses a significant treatment challenge due to its unique characteristics and resistance to existing drugs. The conventional treatment regimens, which are lengthy and involve multiple drugs, often result in poor patient adherence and subsequent drug resistance, particularly with multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains. This highlights the urgent need for novel anti-TB therapies and new drug targets. Antimicrobial peptides (AMPs), which are natural host defense molecules present in all living organisms, offer a promising alternative to traditional small-molecule drugs. AMPs have several advantages, including their broad-spectrum activity and the potential to circumvent existing resistance mechanisms. However, their clinical application faces challenges such as stability, delivery, and potential toxicity. This review aims to provide essential information on AMPs, including their sources, classification, mode of action, induction within the host under stress, efficacy against M. tuberculosis, clinical status and hurdles to their use. It also highlights future research directions to address these challenges and advance the development of AMP-based therapies for TB.

Nanostructures for Delivery of Flavonoids with Antibacterial Potential against Klebsiella pneumoniae

Flavonoids are secondary metabolites that exhibit remarkable biological activities, including antimicrobial properties against Klebsiella pneumoniae, a pathogen responsible for several serious nosocomial infections. However, oral administration of these compounds faces considerable challenges, such as low bioavailability and chemical instability. Thus, the encapsulation of flavonoids in nanosystems emerges as a promising strategy to mitigate these limitations, offering protection against degradation; greater solubility; and, in some cases, controlled and targeted release. Different types of nanocarriers, such as polymeric nanoparticles, liposomes, and polymeric micelles, among others, have shown potential to increase the antimicrobial efficacy of flavonoids by reducing the therapeutic dose required and minimizing side effects. In addition, advances in nanotechnology enable co-encapsulation with other therapeutic agents and the development of systems responsive to more specific stimuli, optimizing treatment. In this context, the present article provides an updated review of the literature on flavonoids and the main nanocarriers used for delivering flavonoids with antibacterial properties against Klebsiella pneumoniae.

Looking back, moving forward: protein corona of lipid nanoparticles

Lipid nanoparticles (LNPs) are commonly employed for drug delivery owing to their considerable drug-loading capacity, low toxicity, and excellent biocompatibility. Nevertheless, the formation of protein corona (PC) on their surfaces significantly influences the drug's in vivo fate (such as absorption, distribution, metabolism, and elimination) upon administration. PC denotes the phenomenon wherein one or multiple strata of proteins adhere to the external interface of nanoparticles (NPs) or microparticles within the biological milieu, encompassing ex vivo fluids (e.g., serum-containing culture media) and in vivo fluids (such as blood and tissue fluids). Hence, it is essential to claim the PC formation behaviors and mechanisms on the surface of LNPs. This overview provided a comprehensive examination of crucial aspects related to such issues, encompassing time evolution, controllability, and their subsequent impacts on LNPs. Classical studies of PC generation on the surface of LNPs were additionally integrated, and its decisive role in shaping the in vivo fate of LNPs was explored. The mechanisms underlying PC formation, including the adsorption theory and alteration theory, were introduced to delve into the formation process. Subsequently, the existing experimental outcomes were synthesized to offer insights into the research and application facets of PC, and it was concluded that the manipulation of PC held substantial promise in the realm of targeted delivery.

A Fluorous Peptide Amphiphile with Potent Antimicrobial Activity for the Treatment of MRSA-induced Sepsis and Chronic Wound Infection

The rising prevalence of global antibiotic resistance evokes the urgent need for novel antimicrobial candidates. Cationic lipopeptides have attracted much attention due to their strong antimicrobial activity, broad-spectrum and low resistance tendency. Herein, a library of fluoro-lipopeptide amphiphiles was synthesized by tagging a series of cationic oligopeptides with a fluoroalkyl tail via a disulfide spacer. Among the lipopeptide candidates, R6F bearing six arginine moieties and a fluorous tag shows the highest antibacterial activity, and it exhibits an interesting fluorine effect as compared to the non-fluorinated lipopeptides. The high antibacterial activity of R6F is attributed to its excellent bacterial membrane permeability, which further disrupts the respiratory chain redox stress and cell wall biosynthesis of the bacteria. By co-assembling with lipid nanoparticles, R6F showed high therapeutic efficacy and minimal adverse effects in the treatment of MRSA-induced sepsis and chronic wound infection. This work provides a novel strategy to design highly potent antibacterial peptide amphiphiles for the treatment of drug-resistant bacterial infections.

Antimicrobial peptides in bone regeneration: mechanism and potential

INTRODUCTION

Antimicrobial peptides (AMPs) are small-molecule peptides with a unique antimicrobial mechanism. Other notable biological activities of AMPs, including anti-inflammatory, angiogenesis, and bone formation effects, have recently received widespread attention. These remarkable bioactivities, combined with the unique antimicrobial mechanism of action of AMPs, have led to their increasingly important role in bone regeneration.

AREAS COVERED

In this review, on the one hand, we aimed to summarize information about the AMPs that are currently used for bone regeneration by reviewing published literature in the PubMed database. On the other hand, we also highlight some AMPs with potential roles in bone regeneration and their possible mechanisms of action.

EXPERT OPINION

The translation of AMPs to the clinic still faces many problems, but their unique antimicrobial mechanisms and other conspicuous biological activities suggest great potential. An in-depth understanding of the structure and mechanism of action of AMPs will help us to subsequently combine AMPs with different carrier systems and perform structural modifications to reduce toxicity and achieve stable release, which may be a key strategy for facilitating the translation of AMPs to the clinic.

Peptidome Profiling of Bubalus bubalis Urine and Assessment of Its Antimicrobial Activity against Mastitis-Causing Pathogens

Urinary proteins have been studied quite exhaustively in the past, however, the small sized peptides have remained neglected for a long time in dairy cattle. These peptides are the products of systemic protein turnover, which are excreted out of the body and hence can serve as an important biomarker for various pathophysiologies. These peptides in other species of bovine have been reported to possess several bioactive properties. To investigate the urinary peptides in buffalo and simultaneously their bioactivities, we generated a peptidome profile from the urine of Murrah Buffaloes (n = 10). Urine samples were processed using <10 kDa MWCO filter and filtrate obtained was used for peptide extraction using Solid Phase Extraction (SPE). The nLC-MS/MS of the aqueous phase from ten animals resulted in the identification of 8165 peptides originating from 6041 parent proteins. We further analyzed these peptide sequences to identify bioactive peptides and classify them into anti-cancerous, anti-hypertensive, anti-microbial, and anti-inflammatory groups with a special emphasis on antimicrobial properties. With this in mind, we simultaneously conducted experiments to evaluate the antimicrobial properties of urinary aqueous extract on three pathogenic bacterial strains: S. aureus, E. coli, and S. agalactiae. The urinary peptides observed in the study are the result of the activity of possibly 76 proteases. The GO of these proteases showed the significant enrichment of the antibacterial peptide production. The total urinary peptide showed antimicrobial activity against the aforementioned pathogenic bacterial strains with no significant inhibitory effects against a buffalo mammary epithelial cell line. Just like our previous study in cows, the present study suggests the prime role of the antimicrobial peptides in the maintenance of the sterility of the urinary tract in buffalo by virtue of their amino acid composition.

DP1, a multifaceted synthetic peptide: Mechanism of action, activity and clinical potential

AIMS

Microbial infections remain a leading cause of mortality worldwide, with Staphylococcus aureus (S. aureus) being a prominent etiological agent, responsible for causing persistent bacterial infections in humans. It is a nosocomial, opportunistic pathogen, capable to propagate within the bloodstream and withstand therapeutic interventions. In the current study, a novel, indigenously designed synthetic antimicrobial peptide (sAMP) has been evaluated for its antimicrobial potential to inhibit the growth and proliferation of S. aureus.

MAIN METHODS

The sAMP, designed peptide (DP1) was evaluated for its minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against a panel of pathogenic bacterial strains. Membrane mechanistic studies were performed by measuring membrane conductivity via dielectric spectroscopy and visualizing changes in bacterial membrane structure through field emission scanning electron microscopy (FE-SEM). Further, DP1 was tested for its in vivo antimicrobial potential in an S. aureus-induced systemic infection model.

KEY FINDINGS

The results indicated that DP1 has the potential to inhibit the growth and proliferation of a broad spectrum of Gram-positive, Gram-negative and multidrug-resistant (MDR) bacterial strains. Strong bactericidal effect attributed to change in electrical conductivity of the bacterial cells leading to membrane disruption was observed through dielectric spectroscopy and FE-SEM micrographs. Further, in the in vivo murine systemic infection study, 50 % reduction in S. aureus bioburden was observed within 1 day of the administration of DP1.

SIGNIFICANCE

The results indicate that DP1 is a multifaceted peptide with potent bactericidal, antioxidant and therapeutic properties. It holds significance as a novel drug candidate to effectively combat S. aureus-mediated systemic infections.

Polylactic Glycolic Acid-Mediated Delivery of Plectasin Derivative NZ2114 in Staphylococcus epidermidis Biofilms

Antimicrobial peptides (AMPs) are antibiotic candidates; however, their instability and protease susceptibility limit clinical applications. In this study, the polylactic acid-glycolic acid (PLGA)-polyvinyl alcohol (PVA) drug delivery system was screened by orthogonal design using the double emulsion-solvent evaporation method. NZ2114 nanoparticles (NZ2114-NPs) displayed favorable physicochemical properties with a particle size of 178.11 ± 5.23 nm, polydispersity index (PDI) of 0.108 ± 0.10, ζ potential of 4.78 ± 0.67 mV, actual drug-loading rate of 4.07 ± 0.37%, encapsulation rate of 81.46 ± 7.42% and cumulative release rate of 67.75% (120 h) in PBS. The results showed that PLGA encapsulation increased HaCaT cell viability by 20%, peptide retention in 50% serum by 24.12%, and trypsin tolerance by 4.24-fold. Meanwhile, in vitro antimicrobial assays showed that NZ2114-NPs had high inhibitory activity against Staphylococcus epidermidis (S. epidermidis) (4-8 μg/mL). Colony counting and confocal laser scanning microscopy (CLSM) confirmed that NZ2114-NPs were effective in reducing the biofilm thickness and bacterial population of S. epidermidis G4 with a 99% bactericidal rate of persister bacteria, which was significantly better than that of free NZ2114. In conclusion, the results demonstrated that PLGA nanoparticles can be used as a reliable NZ2114 delivery system for the treatment of biofilm infections caused by S. epidermidis.

Surface Functionalized Lipid Nanoparticles in Promoting Therapeutic Outcomes: An Insight View of the Dynamic Drug Delivery System

Compared to the conventional approach, nanoparticles (NPs) facilitate a non-hazardous, non-toxic, non-interactive, and biocompatible system, rendering them incredibly promising for improving drug delivery to target cells. When that comes to accomplishing specific therapeutic agents like drugs, peptides, nucleotides, etc., lipidic nanoparticulate systems have emerged as even more robust. They have asserted impressive ability in bypassing physiological and cellular barriers, evading lysosomal capture and the proton sponge effect, optimizing bioavailability, and compliance, lowering doses, and boosting therapeutic efficacy. However, the lack of selectivity at the cellular level hinders its ability to accomplish its potential to the fullest. The inclusion of surface functionalization to the lipidic NPs might certainly assist them in adapting to the basic biological demands of a specific pathological condition. Several ligands, including peptides, enzymes, polymers, saccharides, antibodies, etc., can be functionalized onto the surface of lipidic NPs to achieve cellular selectivity and avoid bioactivity challenges. This review provides a comprehensive outline for functionalizing lipid-based NPs systems in prominence over target selectivity. Emphasis has been put upon the strategies for reinforcing the therapeutic performance of lipidic nano carriers' using a variety of ligands alongside instances of relevant commercial formulations.

Identification of novel bacteriocin against Staphylococcus and Bacillus species

Objectives

Due to the continues emergence of antimicrobial resistance, discovery of novel compounds are urgently required. Thus, this study is focused to identify a novel antimicrobial peptide (bacteriocin) targeting multidrug-resistant pathogenic bacteria.

Methods

About 80 environmental isolates were recovered and screened for anti-bacterial activity using simultaneous antagonism assays. Produced peptide (AB3) was purified using Strata-XL-C and Sep-Pack columns. Matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) analysis and MIC were conducted on the AB3 peptide to determine its molecular weight and spectrum of activity. Extraction and amplification for the 16S rRNA gene of the producing strain was accomplished using QIAamp DNA Mini Kit and GeneAmp PCR system thermocycler, respectively. Novelty of the compound was assessed based on all obtained genomic and proteomic data using Basic Local Alignment Search Tool search and Unni-Prot and Bactibase, respectively.

Results

About 5% of screened isolates showed antagonistic activity toward tested indicators. Obtained compound showed narrow spectrum of activity toward certain Gram-positive species including, methicillin-sensitive Staphylococcus aureus (MSSA), methicillin-resistant Staphylococcus aureus (MRSA) and Bacillus species. MALDI-TOF analysis revealed the flowing molecular masses: 1288.207 Da, 1304.536 Da, 1326.529 Da, 1403.591 Da, and 1472.792 Da. The extensive genomic and proteomic analysis have indicated the discovery of novel bacteriocin produced by Bacillus malacitensis.

Conclusion

A novel bacteriocin (AB3) was identified from B. malacitensis, which has showed promising in vitro bactericidal activity toward MSSA, MRSA, and Bacillus subtilis. This compound holds great potential to replace or used in combination with currently used antibiotics to treat serious untreatable bacterial infections. However, further investigations to determine its suitability for therapeutic use in human health are needed.

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

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

Targeted delivery of a short antimicrobial peptide (CM11) against Helicobacter pylori gastric infection using concanavalin A-coated chitosan nanoparticles

Helicobacter pylori is the cause of most cases of stomach ulcers and also causes some digestive cancers. The emergence and spread of antibiotic-resistant strains of H. pylori is one of the most important challenges in the treatment of its infections. The present study aims to develop a concanavalin A (ConA) coated chitosan (CS) nanocarrier-based drug delivery for the targeted release of peptides to the site of H. pylori infection. Accordingly, chitosan was used as an encapsulating agent for CM11 peptide delivery by applying ionotropic gelation method. Con-A was used for coating CS nanoparticles to target H. pylori. The CS NPs and ConA-CS NPs were characterized by FTIR, dynamic light scattering (DLS), and scanning electron microscopy (SEM). The MIC of CM11-loaded ConA-CS NPs against H. pylori SS1 strain was analyzed in vitro. In order to evaluate the treatment efficiency in vivo, a gastric infection model of H. pylori SS1 strain was established in mice and histopathological studies and IL-1β cytokine assay were performed. Based on the results, the size frequency for CS NPs and ConA-CS NPs was about 200 and 350 nm, respectively. The prepared CM11-loaded ConA-CS NPs exhibited antibacterial activity against H. pylori SS1 strain with a concentration of 32 µg/ml. The highest healing process was observed in synthesized CM11-loaded ConA-CS NPs treatments and a significant decrease in IL-1β was observed. Our findings highlight the potential of chitosan nanoparticles as a drug delivery vehicle in the treatment of gastric infection model of H. pylori SS1 strain.

Short Antimicrobial Peptides: Therapeutic Potential and Recent Advancements

There has been a lot of interest in antimicrobial peptides (AMPs) as potential next-generation antibiotics. They are components of the innate immune system. AMPs have broad-spectrum action and are less prone to resistance development. They show potential applications in various fields, including medicine, agriculture, and the food industry. However, despite the good activity and safety profiles, AMPs have had difficulty finding success in the clinic due to their various limitations, such as production cost, proteolytic susceptibility, and oral bioavailability. To overcome these flaws, a number of solutions have been devised, one of which is developing short antimicrobial peptides. Short antimicrobial peptides do have an advantage over longer peptides as they are more stable and do not collapse during absorption. They have generated a lot of interest because of their evolutionary success and advantageous properties, such as low molecular weight, selective targets, cell or organelles with minimal toxicity, and enormous therapeutic potential. This article provides an overview of the development of short antimicrobial peptides with an emphasis on those with ≤ 30 amino acid residues as a potential therapeutic agent to fight drug-resistant microorganisms. It also emphasizes their applications in many fields and discusses their current state in clinical trials.