Tobramycin-loaded complexes to prevent and disrupt Pseudomonas aeruginosa biofilms

Nanomedicines as disruptors or inhibitors of biofilms: Opportunities in addressing antimicrobial resistance

The problem of antimicrobial resistance (AMR) has caused global concern due to its great threat to human health. Evidences are emerging for a critical role of biofilms, one of the natural protective mechanisms developed by bacteria during growth, in resisting commonly used clinical antibiotics. Advances in nanomedicines with tunable physicochemical properties and unique anti-biofilm mechanisms provide opportunities for solving AMR risks more effectively. In this review, we summarize the five "A" stages (adhesion, amplification, alienation, aging and allocation) of biofilm formation and mechanisms through which they protect the internal bacteria. Aimed at the characteristics of biofilms, we emphasize the design "THAT" principles (targeting, hacking, adhering and transport) of nanomedicines in their interactions with biofilms and internal bacteria. Furthermore, recent progresses in multimodal antibacterial nanomedicines, including biofilms disruption and bactericidal activity, and the types of currently available antibiofilm nanomedicines contained organic and inorganic nanomedicines are outlined and highlighted their potential applications in the development of preclinical research. Last but not least, we offer a perspective for the effectiveness of nanomedicines designed to address AMR and challenges associated with their clinical translation.

Mechanism and nanotechnological-based therapeutics for tolerance and resistance of bacterial biofilms

Bacterial biofilms are one of the most relevant drivers of chronic and recurrent infections and a significant healthcare problem. Biofilms were formed by cross-linking of hydrophobic extracellular polymeric substances (EPS), such as proteins, polysaccharides, and eDNA, which were synthesized by bacteria themselves after adhesion and colonization on biological surfaces. They had the characteristics of dense structure and low drug permeability, leading to tolerance and resistance of biofilms to antibiotics and to host responses. Within a biofilm, microbial cells show increased tolerance to both immune system defense mechanisms and antimicrobials than the same cells in the planktonic state. It is one of the key reasons for the failure of traditional clinical drug to treat infectious diseases. Currently, no drugs are available to attack bacterial biofilms in the clinical setting. The development of novel preventive and therapeutic strategies is urgently needed to allow an effective management of biofilm-associated infections. Based on the properties of nanomaterials and biocompatibility, nanotechnology had the advantages of specific targeting, intelligent delivery and low toxicity, which could realize efficient intervention and precise treatment of biofilm-associated infections. In this paper, the mechanisms of bacterial biofilm resistance to antibiotics and host response tolerance were elaborated. Meanwhile, This paper highlighted multiple strategies of biofilms eradication based on nanotechnology. Nanotechnology can interfere with biofilm formation by destroying mature biofilm, modulating biofilm heterogeneity, inhibiting bacterial metabolism, playing antimicrobial properties, activating immunity and enhancing biofilm penetration, which is an important new anti-biofilm preparation. In addition, we presented the key challenges still faced by nanotechnology in combating bacterial biofilm infections. Utilization of nanotechnology safely and effectively should be further strengthened to confirm the safety aspects of their clinical application.

Inovirus-Encoded Peptides Induce Specific Toxicity in Pseudomonas aeruginosa

Pseudomonas aeruginosa is a common opportunistic pathogen associated with nosocomial infections. The primary treatment for infections typically involves antibiotics, which can lead to the emergence of multidrug-resistant strains. Therefore, there is a pressing need for safe and effective alternative methods. Phage therapy stands out as a promising approach. However, filamentous prophages (Pfs) commonly found in P. aeruginosa encode genes with phage defense activity, thereby reducing the efficacy of phage therapy. Through a genomic analysis of the Pf4 prophage, we identified a 102 bp gene co-transcribed with the upstream gene responsible for phage release (zot gene), giving rise to a 33-amino-acid polypeptide that we have named Pf4-encoded toxic polypeptide (PftP4). The overexpression of PftP4 demonstrated cellular toxicity in P. aeruginosa, with subcellular localization indicating its presence in the cell membrane and a subsequent increase in membrane permeability. Notably, PftP4 homologues are found in multiple Pf phages and exhibit specificity in their toxicity towards P. aeruginosa among the tested bacterial strains. Our study reveals that the novel Pf-encoded polypeptide PftP4 has the potential to selectively target and eradicate P. aeruginosa, offering valuable insights for combating P. aeruginosa infections.

Insights on Pseudomonas aeruginosa Carbohydrate Binding from Profiles of Cystic Fibrosis Isolates Using Multivalent Fluorescent Glycopolymers Bearing Pendant Monosaccharides

Pseudomonas aeruginosa contributes to frequent, persistent, and, often, polymicrobial respiratory tract infections for individuals with cystic fibrosis (CF). Chronic CF infections lead to bronchiectasis and a shortened lifespan. P. aeruginosa expresses numerous adhesins, including lectins known to bind the epithelial cell and mucin glycoconjugates. Blocking carbohydrate-mediated host-pathogen and intra-biofilm interactions critical to the initiation and perpetuation of colonization offer promise as anti-infective treatment strategies. To inform anti-adhesion therapies, we profiled the monosaccharide binding of P. aeruginosa from CF and non-CF sources, and assessed whether specific bacterial phenotypic characteristics affected carbohydrate-binding patterns. Focusing at the cellular level, microscopic and spectrofluorometric tools permitted the solution-phase analysis of P. aeruginosa binding to a panel of fluorescent glycopolymers possessing distinct pendant monosaccharides. All P. aeruginosa demonstrated significant binding to glycopolymers specific for α-D-galactose, β-D-N-acetylgalactosamine, and β-D-galactose-3-sulfate. In each culture, a small subpopulation accounted for the binding. The carbohydrate anomeric configuration and sulfate ester presence markedly influenced binding. While this opportunistic pathogen from CF hosts presented with various colony morphologies and physiological activities, no phenotypic, physiological, or structural feature predicted enhanced or diminished monosaccharide binding. Important to anti-adhesive therapeutic strategies, these findings suggest that, regardless of phenotype or clinical source, P. aeruginosa maintain a small subpopulation that may readily associate with specific configurations of specific monosaccharides. This report provides insights into whole-cell P. aeruginosa carbohydrate-binding profiles and into the context within which successful anti-adhesive and/or anti-virulence anti-infective agents for CF must contend.

Strategies to Promote the Journey of Nanoparticles Against Biofilm-Associated Infections

Biofilm-associated infections are one of the most challenging healthcare threats for humans, accounting for 80% of bacterial infections, leading to persistent and chronic infections. The conventional antibiotics still face their dilemma of poor therapeutic effects due to the high tolerance and resistance led by bacterial biofilm barriers. Nanotechnology-based antimicrobials, nanoparticles (NPs), are paid attention extensively and considered as promising alternative. This review focuses on the whole journey of NPs against biofilm-associated infections, and to clarify it clearly, the journey is divided into four processes in sequence as 1) Targeting biofilms, 2) Penetrating biofilm barrier, 3) Attaching to bacterial cells, and 4) Translocating through bacterial cell envelope. Through outlining the compositions and properties of biofilms and bacteria cells, recent advances and present the strategies of each process are comprehensively discussed to combat biofilm-associated infections, as well as the combined strategies against these infections with drug resistance, aiming to guide the rational design and facilitate wide application of NPs in biofilm-associated infections.

Fighting Pseudomonas aeruginosa Infections: Antibacterial and Antibiofilm Activity of D-Q53 CecB, a Synthetic Analog of a Silkworm Natural Cecropin B Variant

Pseudomonas aeruginosa is an opportunistic Gram-negative bacterium responsible for severe nosocomial infections and is considered a critical pulmonary pathogen for both immunocompromised and cystic fibrosis patients. Planktonic cells of P. aeruginosa possess intrinsic and acquired resistances, inactivating several classes of conventional antibiotics. Additionally, this bacterium can grow, forming biofilms, and complex structures, further hampering the action of multiple antibiotics. Here, we report the biological properties of D-Q53 CecB, an all-D enantiomer of the silkworm natural peptide Q53 CecB. Compared to the L-variant, D-Q53 CecB was resistant to in vitro degradation by humans and P. aeruginosa elastases and showed an enhanced bactericidal activity against P. aeruginosa planktonic bacteria. D-Q53 CecB was thermostable and maintained its antimicrobial activity at high salt concentrations and in the presence of divalent cations or fetal-bovine serum, although at reduced levels. Against different types of human cells, D-Q53 CecB showed cytotoxic phenomena at concentrations several folds higher compared to those active against P. aeruginosa. When L- and D-Q53 CecB were compared for their antibiofilm properties, both peptides were active in inhibiting biofilm formation. However, the D-enantiomer was extremely effective in inducing biofilm degradation, suggesting this peptide as a favorable candidate in an anti-Pseudomonas therapy.

Glycopolymers against pathogen infection

Pathogens including viruses, bacteria, fungi, and parasites continue to shape our lives in profound ways every day. As we have learned to live in parallel with pathogens, we have gained a better understanding of the rules of engagement for how they bind, adhere, and invade host cells. One such mechanism involves the exploitation of host cell surface glycans for attachment/adhesion, one of the first steps of infection. This knowledge has led to the development of glycan-based diagnostics and therapeutics for the treatment and prevention of infection. One class of compounds that has become increasingly important are the glycopolymers. Glycopolymers are macromolecules composed of a synthetic scaffold presenting carbohydrates as side chain motifs. Glycopolymers are particularly attractive because their properties can be tuned by careful choice of the scaffold, carbohydrate/glycan, and overall presentation. In this review, we highlight studies over the past ten years that have examined the role of glycopolymers in pathogen adhesion and host cell infection, biofilm formation and removal, and drug delivery with the aim of examining the direct effects of these macromolecules on pathogen engagement. In addition, we also examine the role of glycopolymers as diagnostics for the detection and monitoring of pathogens.

Iminated aminoglycosides in self-emulsifying drug delivery systems: Dual approach to break down the microbial defense

HYPOTHESIS

Aminoglycosides are well known, cationic antimicrobial drugs. However, biofilm-based antibiotic resistance significantly limits their efficacy. Masking the polycationic character of these drugs, followed by incorporation into self-emulsifying drug delivery systems (SEDDS) can improve biofilm eradication.

EXPERIMENTS

Imine derivatives were synthesized via coupling with trans-cinnamaldehyde and characterized regarding degree of substitution, logP, cytotoxicity and antimicrobial efficacy on the opportunistic human pathogens Escherichia coli, Staphylococcus aureus and Candida albicans. Imines were loaded into newly developed SEDDS formulations and the antimicrobial efficacy was assessed on these pathogens in planktonic state and after biofilm formation.

FINDINGS

Successful synthesis of imine derivatives with almost entirely masked amine groups was confirmed by NMR, FT-IR, TLC and MS. Imines exhibited a marked elevation in logP value of 8 units for kanamycin and 7.7 units for tobramycin. They showed low toxicity profiles while fully preserving antimicrobial efficacy on all tested pathogens. Incorporation into SEDDS resulted in nanoemulsions, which exhibited equal antimicrobial efficacy on the model germs compared to the corresponding aminoglycosides. Moreover, the biofilm eradication assay revealed superior anti-biofilm properties of the nanoemulsions. Native aminoglycosides were largely prone to reduced microbial susceptibility due to biofilm formation, while the combination of SEDDS with iminated aminoglycosides provided overall enhanced biofilm eradication.

Mannosylated Polycations Target CD206+ Antigen-Presenting Cells and Mediate T-Cell-Specific Activation in Cancer Vaccination

Immunotherapy is deemed one of the most powerful therapeutic approaches to treat cancer. However, limited response and tumor specificity are still major challenges to address. Herein, mannosylated polycations targeting mannose receptor- are developed as vectors for plasmid DNA (pDNA)-based vaccines to improve selective delivery of genetic material to antigen-presenting cells and enhance immune cell activation. Three diblock glycopolycations (M₁₅A₁₂, M₂₉A₂₅, and M₅₈A₄₅) and two triblock copolymers (M₂₉A₂₉B₉ and M₆₂A₅₂B₃₂) are generated by using mannose (M), agmatine (A), and butyl (B) derivatives to target CD206, complex nucleic acids, and favor the endosomal escape, respectively. All glycopolycations efficiently complex pDNA at N/P ratios <5, protecting the pDNA from degradation in a physiological milieu. M₅₈A₄₅ and M₆₂A₅₂B₃₂ complexed with plasmid encoding for antigenic ovalbumin (pOVA) trigger the immune activation of cultured dendritic cells, which present the SIINFEKL antigenic peptide via specific major histocompatibility complex-I. Importantly, administration of M₅₈A₄₅/pOVA elicits SIINFEKL-specific T-cell response in C56BL/6 mice bearing the melanoma tumor model B16-OVA, well in line with a reduction in tumor growth. These results qualify mannosylation as an efficient strategy to target immune cells in cancer vaccination and emphasize the potential of these glycopolycations as effective delivery vehicles for nucleic acids.

Tobramycin Nanoantibiotics and Their Advantages: A Minireview

Nowadays, antimicrobial resistance (AMR) represents a challenge for antibiotic therapy, mostly involving Gram-negative bacteria. Among the strategies activated to overcome AMR, the repurposing of already available antimicrobial molecules by encapsulating them in drug delivery systems, such as nanoparticles (NPs) and also engineered NPs, seems to be promising. Tobramycin is a powerful and effective aminoglycoside, approved for complicated infections and reinfections and indicated mainly against Gram-negative bacteria, such as Pseudomonas aeruginosa, Escherichia coli, Proteus, Klebsiella, Enterobacter, Serratia, Providencia, and Citrobacter species. However, the drug presents several side effects, mostly due to dose frequency, and for this reason, it is a good candidate for nanomedicine formulation. This review paper is focused on what has been conducted in the last 20 years for the development of Tobramycin nanosized delivery systems (nanoantibiotics), with critical discussion and comparison. Tobramycin was selected as the antimicrobial drug because it is a wide-spectrum antibiotic that is effective against both Gram-positive and Gram-negative aerobic bacteria, and it is characterized by a fast bactericidal effect, even against multidrug-resistant microorganisms (MDR).