Penetration and Accumulation of Dendrons with Different Peripheral Composition in Pseudomonas aeruginosa Biofilms

Nanomaterials Regulate Bacterial Quorum Sensing: Applications, Mechanisms, and Optimization Strategies

Anti-virulence therapy that interferes with bacterial communication, known as "quorum sensing (QS)", is a promising strategy for circumventing bacterial resistance. Using nanomaterials to regulate bacterial QS in anti-virulence therapy has attracted much attention, which is mainly attributed to unique physicochemical properties and excellent designability of nanomaterials. However, bacterial QS is a dynamic and multistep process, and there are significant differences in the specific regulatory mechanisms and related influencing factors of nanomaterials in different steps of the QS process. An in-depth understanding of the specific regulatory mechanisms and related influencing factors of nanomaterials in each step can significantly optimize QS regulatory activity and enhance the development of novel nanomaterials with better comprehensive performance. Therefore, this review focuses on the mechanisms by which nanomaterials regulate bacterial QS in the signal supply (including signal synthesis, secretion, and accumulation) and signal transduction cascade (including signal perception and response) processes. Moreover, based on the two key influencing factors (i.e., the nanomaterial itself and the environment), optimization strategies to enhance the QS regulatory activity are comprehensively summarized. Collectively, applying nanomaterials to regulate bacterial QS is a promising strategy for anti-virulence therapy. This review provides reference and inspiration for further research on the anti-virulence application of nanomaterials.

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.

Anti-biofilm, drug delivery and cytotoxicity properties of dendrimers

Background and purpose

Treatments using antimicrobial agents have faced many difficulties as a result of biofilm formation by pathogenic microorganisms. The biofilm matrix formed by these microorganisms prevents antimicrobial agents from penetrating the interior where they can exact their activity effectively. Additionally, extracellular polymeric molecules associated with biofilm surfaces can absorb antimicrobial compounds, lowering their bioavailability. This problem has resulted in the quest for alternative treatment protocols, and the development of nanomaterials and devices through nanotechnology has recently been on the rise.

Research approach

The literature on dendrimers was searched for in databases such as Google Scholar, PubMed, and ScienceDirect.

Key results

As a nanomaterial, dendrimers have found useful applications as a drug delivery vehicle for antimicrobial agents against biofilm-mediated infections to circumvent these defense mechanisms. The distinctive properties of dendrimers, such as multi-valency, biocompatibility, high water solubility, non-immunogenicity, and biofilm matrix-/cell membrane fusogenicity (ability to merge with intracellular membrane or other proteins), significantly increase the efficacy of antimicrobial agents and reduce the likelihood of recurring infections.

Conclusion

This review outlines the current state of dendrimer carriers for biofilm treatments, provides examples of their real-world uses, and examines potential drawbacks.

Dendritic systems for bacterial outer membrane disruption as a method of overcoming bacterial multidrug resistance

The alarming rise of multi-drug resistant microorganisms has increased the need for new approaches through the development of innovative agents that are capable of attaching to the outer layers of bacteria and causing permanent damage by penetrating the bacterial outer membrane. The permeability (disruption) of the outer membrane of Gram-negative bacteria is now considered to be one of the main ways to overcome multidrug resistance in bacteria. Natural and synthetic permeabilizers such as AMPs and dendritic systems seem promising. However, due to their advantages in terms of biocompatibility, antimicrobial capacity, and wide possibilities for modification and synthesis, highly branched polymers and dendritic systems have gained much more interest in recent years. Various forms of arrangement, and structure of the skeleton, give dendritic systems versatile applications, especially the possibility of attaching other ligands to their surface. This review will focus on the mechanisms used by different types of dendritic polymers, and their complexes with macromolecules to enhance their antimicrobial effect, and to permeabilize the bacterial outer membrane. In addition, future challenges and potential prospects are illustrated in the hope of accelerating the advancement of nanomedicine in the fight against resistant pathogens.

Recent Advances of Degradation Technologies Based on PROTAC Mechanism

PROTAC (proteolysis-targeting chimeras), which selectively degrades target proteins, has become the most popular technology for drug development in recent years. Here, we introduce the history of PROTAC, and summarize the recent advances in novel types of degradation technologies based on the PROTAC mechanism, including TF-PROTAC, Light-controllable PROTAC, PhosphoTAC, LYTAC, AUTAC, ATTEC, CMA, RNA-PROTAC and RIBOTACs. In addition, the clinical progress, current challenges and future prospects of degradation technologies based on PROTAC mechanism are discussed.

Recent advances in mechanical force-responsive drug delivery systems

Mechanical force responsive drug delivery systems (in terms of mechanical force induced chemical bond breakage or physical structure destabilization) have been recently explored to exhibit a controllable pharmaceutical release behaviour at a molecular level. In comparison with chemical or biological stimulus triggers, mechanical force is not only an external but also an internal stimulus which is closely related to the physiological status of patients. However, although this mechanical force stimulus might be one of the most promising and feasible sources to achieve on-demand pharmaceutical release, current research in this field is still limited. Hence, this tutorial review aims to comprehensively evaluate the recent advances in mechanical force-responsive drug delivery systems based on different types of mechanical force, in terms of direct stimulation by compressive, tensile, and shear force, or indirect/remote stimulation by ultrasound and a magnetic field. Furthermore, the exciting developments and current challenges in this field will also be discussed to provide a blueprint for potential clinical translational research of mechanical force-responsive drug delivery systems.

Interaction between Engineered Pluronic Silica Nanoparticles and Bacterial Biofilms: Elucidating the Role of Nanoparticle Surface Chemistry and EPS Matrix

Nanoparticles (NPs) are considered a promising tool in the context of biofilm control. Many studies have shown that different types of NPs can interfere with the bacterial metabolism and cellular membranes, thus making them potential antibacterial agents; however, fundamental understanding is still lacking on the exact mechanisms involved in these actions. The development of NP-based approaches for effective biofilm control also requires a thorough understanding of how the chosen nanoparticles will interact with the biofilm itself, and in particular with the biofilm self-produced extracellular polymeric matrix (EPS). This work aims to provide advances in the understanding of the interaction between engineered fluorescent pluronic silica (PluS) nanoparticles and bacterial biofilms, with a main focus on the role of the EPS matrix in the accumulation and diffusion of the particles in the biofilm. It is demonstrated that particle surface chemistry has a key role in the different lateral distribution and specific affinity to the biofilm matrix components. The results presented in this study contribute to our understanding of biofilm-NP interactions and promote the principle of the rational design of smart nanoparticles as an important tool for antibiofilm technology.

Nanocarriers for combating biofilms: advantages and challenges

Bacterial biofilms are highly resistant to antibiotics and pose a great threat to human and animal health. The control and removal of bacterial biofilms have become an important topic in the field of bacterial infectious diseases. Nanocarriers show great anti-biofilm potential because of their small particle size and strong permeability. In this review, the advantages of nanocarriers for combating biofilms are analyzed. Nanocarriers can act on all stages of bacterial biofilm formation and diffusion. They can improve the scavenging effect of biofilm by targeting biofilm, destroying extracellular polymeric substances, and enhancing the biofilm permeability of antimicrobial substances. Nanocarriers can also improve the antibacterial ability of antimicrobial drugs against bacteria in biofilm by protecting the loaded drugs and controlling the release of antimicrobial substances. Additionally, we emphasize the challenges faced in using nanocarrier formulations and translating them from a preclinical level to the clinical setting.

Biofilms in Surgical Site Infections: Recent Advances and Novel Prevention and Eradication Strategies

Surgical site infections (SSIs) are common postoperative occurrences due to contamination of the surgical wound or implanted medical devices with community or hospital-acquired microorganisms, as well as other endogenous opportunistic microbes. Despite numerous rules and guidelines applied to prevent these infections, SSI rates are considerably high, constituting a threat to the healthcare system in terms of morbidity, prolonged hospitalization, and death. Approximately 80% of human SSIs, including chronic wound infections, are related to biofilm-forming bacteria. Biofilm-associated SSIs are extremely difficult to treat with conventional antibiotics due to several tolerance mechanisms provided by the multidrug-resistant bacteria, usually arranged as polymicrobial communities. In this review, novel strategies to control, i.e., prevent and eradicate, biofilms in SSIs are presented and discussed, focusing mainly on two attractive approaches: the use of nanotechnology-based composites and natural plant-based products. An overview of new therapeutic agents and strategic approaches to control epidemic multidrug-resistant pathogenic microorganisms, particularly when biofilms are present, is provided alongside other combinatorial approaches as attempts to obtain synergistic effects with conventional antibiotics and restore their efficacy to treat biofilm-mediated SSIs. Some detection and real-time monitoring systems to improve biofilm control strategies and diagnosis of human infections are also discussed.

The Two Weapons against Bacterial Biofilms: Detection and Treatment

Bacterial biofilms are defined as complex aggregates of bacteria that grow attached to surfaces or are associated with interfaces. Bacteria within biofilms are embedded in a self-produced extracellular matrix made of polysaccharides, nucleic acids, and proteins. It is recognized that bacterial biofilms are responsible for the majority of microbial infections that occur in the human body, and that biofilm-related infections are extremely difficult to treat. This is related with the fact that microbial cells in biofilms exhibit increased resistance levels to antibiotics in comparison with planktonic (free-floating) cells. In the last years, the introduction into the market of novel compounds that can overcome the resistance to antimicrobial agents associated with biofilm infection has slowed down. If this situation is not altered, millions of lives are at risk, and this will also strongly affect the world economy. As such, research into the identification and eradication of biofilms is important for the future of human health. In this sense, this article provides an overview of techniques developed to detect and imaging biofilms as well as recent strategies that can be applied to treat biofilms during the several biofilm formation steps.

Pharma-molecule Transport across Bacterial Membranes: Detection and Quantification Approaches by Electrochemistry and Bioanalytical Methods

Antibiotic resistance is a significant challenge encountered by healthcare systems on a global scale. Knowledge about membrane transport of antibiotics and other pharmacologically relevant molecules in bacteria is crucial towards understanding and overcoming antibiotic resistance, as drug resistance often depends on drug transport. This comprehensive literature review discusses the detection and quantification of membrane transport of pharma-molecules in bacteria and highlights the importance of molecule transport to antibiotic resistance. This review emphasizes electrochemical and electrophysiological methods of detection and quantification. The results of this literature review reveal a substantial diversity in methods and types of quantitative information collected.

MSNs-Based Nanocomposite for Biofilm Imaging and NIR-Activated Chem/Photothermal/Photodynamic Combination Therapy

Bacterial infections caused by biofilms are severe clinical problems, resulting in high drug resistance by limiting the penetration of antibiotics. Herein, a near-infrared (NIR)-activated chem/photodynamic/photothermal combined therapeutic agent is proposed by loading fluorescein isothiocyanate (FITC), ultrasmall copper sulfide nanoparticles (Cu_2-xSNPs), and ε-polylysine (PLL) onto mesoporous silica nanoparticles (MSNs) through a layer-by-layer self-assembly approach. FITC-doped MSNs are prepared to monitor the permeability and accumulation of nanocomposites into biofilms. MSNs can also act as hosts for the synthesis of ultrasmall Cu_2-xSNPs, which has effective photodynamic and photothermal ablation against bacteria under NIR light irradiation. Moreover, biodegradable PLL introduced can not only enhance adhesion toward the bacterial surface to increase the effectiveness of phototherapy but also damage bacteria through electrostatic interaction. As a result, the prepared nanocomposites could not only penetrate biofilms but also ablate biofilms through combined chem/photodynamic/photothermal effects under NIR light irradiation. Furthermore, the nanocomposites could treat bacterial infections in vivo with negligible tissue toxicity. Overall, the finely designed nanocomposites are anticipated to display promising applications in imaging-guided chem/photodynamic/photothermal combined therapy for bacterial infections.

Nontoxic Antimicrobial Cationic Peptide Nanoconstructs with Bacteria-Displaceable Polymeric Counteranions

Antimicrobial peptides that target the integrity of bacterial envelopes can eradicate pathogens with little development of resistance, but they often inflict nonselective toxicity toward mammalian cells. The prevailing approach to optimize the selectivity of cationic peptides has been to modify their composition. Instead, we invent a new generation of broad-spectrum antibacterial nanoconstructs with negligible mammalian cell toxicity through a competitive displacement of counter polyanions from the complementary polycations. The nanoconstruct, which has a highly cationic Au nanoparticles (NPs) core shielded by polymeric counterions, is inert in nonbacterial environments. When exposed to negatively charged bacterial envelopes, this construct sheds its polyanions, triggering a cationic Au NP/bacterial membrane interaction that rapidly kills Gram-positive and Gram-negative bacteria. The anionic charge and hydrophilicity of the polyanion provides charge neutralization for the peptide-decorated Au NP core, but it is also bacteria-displaceable. These results provide a foundation for the development of other cationic particles and polymeric counterion combinations with potent antimicrobial activity without toxicity.

Peptides and Dendrimers: How to Combat Viral and Bacterial Infections

The alarming growth of antimicrobial resistance and recent viral pandemic events have enhanced the need for novel approaches through innovative agents that are mainly able to attach to the external layers of bacteria and viruses, causing permanent damage. Antimicrobial molecules are potent broad-spectrum agents with a high potential as novel therapeutics. In this context, antimicrobial peptides, cell penetrating peptides, and antiviral peptides play a major role, and have been suggested as promising solutions. Furthermore, dendrimers are to be considered as suitable macromolecules for the development of advanced nanosystems that are able to complement the typical properties of dendrimers with those of peptides. This review focuses on the description of nanoplatforms constructed with peptides and dendrimers, and their applications.

Surface charge modulation of rifampicin-loaded PLA nanoparticles to improve antibiotic delivery in Staphylococcus aureus biofilms

Background

After the golden age of antibiotic discovery, bacterial infections still represent a major challenge for public health worldwide. The biofilm mode of growth is mostly responsible for chronic infections that current therapeutics fail to cure and it is well-established that novel strategies must be investigated. Particulate drug delivery systems are considered as a promising strategy to face issues related to antibiotic treatments in a biofilm context. Particularly, poly-lactic acid (PLA) nanoparticles present a great interest due to their ability to migrate into biofilms thanks to their submicronic size. However, questions still remain unresolved about their mode of action in biofilms depending on their surface properties. In the current study, we have investigated the impact of their surface charge, firstly on their behavior within a bacterial biofilm, and secondly on the antibiotic delivery and the treatment efficacy.

Results

Rifampicin-loaded PLA nanoparticles were synthetized by nanoprecipitation and characterized. A high and superficial loading of rifampicin, confirmed by an in silico simulation, enabled to deliver effective antibiotic doses with a two-phase release, appropriate for biofilm-associated treatments. These nanoparticles were functionalized with poly-l-lysine, a cationic peptide, by surface coating inducing charge reversal without altering the other physicochemical properties of these particles. Positively charged nanoparticles were able to interact stronger than negative ones with Staphylococcus aureus, under planktonic and biofilm modes of growth, leading to a slowed particle migration in the biofilm thickness and to an improved retention of these cationic particles in biofilms. While rifampicin was totally ineffective in biofilms after washing, the increased retention capacity of poly-l-lysine-coated rifampicin-loaded PLA nanoparticles has been associated with a better antibiotic efficacy than uncoated negatively charged ones.

Conclusions

Correlating the carrier retention capacity in biofilms with the treatment efficacy, positively charged rifampicin-loaded PLA nanoparticles are therefore proposed as an adapted and promising approach to improve antibiotic delivery in S. aureus biofilms.