Amphiphilic dendrimers against antibiotic resistance: light at the end of the tunnel?

Amphiphilic Dendrimer as Potent Antibacterial against Drug-Resistant Bacteria in Mouse Models of Human Infectious Diseases

Modern medicine continues to struggle against antibiotic-resistant bacterial pathogens. Among the pathogens of critical concerns are the multidrug-resistant (MDR) Pseudomonas aeruginosa, Staphylococcus aureus, and Klebsiella pneumoniae. These pathogens are major causes of nosocomial infections among immunocompromised individuals, involving major organs such as lung, skin, spleen, kidney, liver, and bloodstream. Therefore, novel approaches are direly needed. Recently, we developed an amphiphilic dendrimer DDC18-8A exhibiting high antibacterial and antibiofilm efficacy in vitro. DDC18-8A is composed of a long hydrophobic alkyl chain and a small hydrophilic poly(amidoamine) dendron bearing amine terminals, exerting its antibacterial activity by attaching and inserting itself into bacterial membranes to trigger cell lysis. Here, we examined the pharmacokinetics and in vivo toxicity as well as the antibacterial efficacy of DDC18-8A in mouse models of human infectious diseases. Remarkably, DDC18-8A significantly reduced the bacterial burden in mouse models of acute pneumonia and bacteremia by P. aeruginosa, methicillin-resistant S. aureus (MRSA), and carbapenem-resistant K. pneumoniae and neutropenic soft tissue infection by P. aeruginosa and MRSA. Most importantly, DDC18-8A outperformed pathogen-specific antibiotics against all three pathogens by achieving a similar bacterial clearance at 10-fold lower therapeutic concentrations. In addition, it showed superior stability and biodistribution in vivo, with excellent safety profiles yet without any observable abnormalities in histopathological analysis of major organs, blood serum biochemistry, and hematology. Collectively, we provide strong evidence that DDC18-8A is a promising alternative to the currently prescribed antibiotics in addressing challenges associated with nosocomial infections by MDR pathogens.

Anti-quorum sensing activity of poly-amidoamine dendrimer generation 5 dendrimer loaded kinase inhibitor peptide against methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is a significant concern in both healthcare and community settings, as it causes numerous infections worldwide with high morbidity and mortality rates. One promising strategy is to target the quorum sensing (QS) system of MRSA using a dendrimer loaded with kinase inhibitor peptide. The present investigation has formulated a poly-amidoamine dendrimer (PAMAM) G5 dendrimer that is loaded with Quorum Quencher (QQ) peptide, which functions as a histidine kinase inhibitor. The particle average size of the formulated G5-QQ3 complex was determined to be 276 nm, and polydispersity index values of 0.33. The MIC50 for the formulated nanoparticles was 18 μM as demonstrated by a growth assay. Furthermore, the G5-QQ3 complex was able to inhibit the hemolysis activity of the MRSA with a concentration of 10 μM, and for Staphylococcus aureus was 3 μM. The G5-QQ3 complex possesses the ability to inhibit, penetrate, and eradicate biofilm in MRSA, Staphylococcus aureus, and different agr mutants with inhibition percentages ranging from 60 to 72%. Furthermore, live/dead viability assay confirmed the ability of the formulated nanoparticles to effectively kill all strains within the biofilm structure as evidenced by a confocal microscope, and the cytotoxicity of the G5-QQ3 complex was dose-dependent (p < 0.05). against RAW 264.7 cells. In general, the study confirmed that encapsulating QQ3 peptide within PAMAM G5 dendrimer results in a potent anti-virulence and anti-bacterial action and suggests a synergistic effect. The findings of this study have significant implications for the development of new treatments for MRSA infections, which are a major public health concern.

Research Status of Dendrimer Micelles in Tumor Therapy for Drug Delivery

Dendrimers are a family of polymers with highly branched structure, well-defined composition, and extensive functional groups, which have attracted great attention in biomedical applications. Micelles formed by dendrimers are ideal nanocarriers for delivering anticancer agents due to the explicit study of their characteristics of particle size, charge, and biological properties such as toxicity, blood circulation time, biodistribution, and cellular internalization. Here, the classification, preparation, and structure of dendrimer micelles are reviewed, and the specific functional groups modified on the surface of dendrimers for tumor active targeting, stimuli-responsive drug release, reduced toxicity, and prolonged blood circulation time are discussed. In addition, their applications are summarized as various platforms for biomedical applications related to cancer therapy including drug delivery, gene transfection, nano-contrast for imaging, and combined therapy. Other applications such as tissue engineering and biosensor are also involved. Finally, the possible challenges and perspectives of dendrimer micelles for their further applications are discussed.

Low-Generation Cationic Phosphorus Dendrimers: Novel Approach to Tackle Drug-Resistant S. aureus In Vitro and In Vivo

The incessant, global increase in antimicrobial resistance (AMR) is a very big challenge for healthcare systems. AMR is predicted to grow at an alarming pace, with a dramatic increase in morbidity, mortality, and a 100 trillion US$ loss to the global economy by 2050. The mortality rate caused by methicillin-resistant S. aureus (MRSA) is much higher as compared to infections caused by drug-susceptible S. aureus. Additionally, there is a big paucity of therapeutics available for treatment of serious infections caused by MRSA. Thus, the discovery and development of novel therapies is an urgent, unmet medical need. In this context, we synthesized AE4G0, a low-generation cationic-phosphorus dendrimer expressing potent antimicrobial activity against S. aureus and Enterococcus sp., and demonstrating a broad selectivity index against eukaryotic cells. AE4G0 exhibits concentration-dependent, bactericidal activity and synergizes with gentamicin, especially against gentamicin-resistant MRSA NRS119. Fluorescence and scanning electron microscopy demonstrate that treatment with AE4G0 led to the utter destruction of S. aureus ATCC 29213 without inducing resistance, despite repeated exposure. When tested in vivo, AE4G0 demonstrates significant efficacy against S. aureus ATCC 29213, alone and in combination with gentamicin against gentamicin-resistant S. aureus NRS119 in the murine skin model of infection. Taken together, AE4G0 demonstrates the potential to be translated as a novel therapeutic option for the treatment of topical, drug-resistant S. aureus infections.