Current progress and prospects of organic nanoparticles against bacterial biofilm

Biofilm-mediated infections; novel therapeutic approaches and harnessing artificial intelligence for early detection and treatment of biofilm-associated infections

A biofilm is a group of bacteria that have self-produced a matrix and are grouped together in a dense population. By resisting the host's immune system's phagocytosis process and attacking with anti-microbial chemicals such as reactive oxygen and nitrogen species, a biofilm enables pathogenic bacteria to evade elimination. One of the major problems in managing chronic injuries is treating wounds colonized by biofilms. These days, a major issue is the biofilms, which exacerbate infection pathogenesis and severity. Numerous investigators have already discovered cutting-edge methods for biofilm manipulation. Using phytochemicals is a practical tactic to control and prevent the production of biofilms. Numerous studies conducted in the last few years have demonstrated the antibacterial and antibiofilm qualities of nanoparticles (NPs) against bacteria, fungi, and protozoa. Because hydrogel has antibiofilm properties, it has been employed extensively in wound care recently. It may be removed with ease and without causing trauma. Today, artificial intelligence (AI) is being used to improve these tactics by providing customized treatment alternatives and predictive analytics. Artificial intelligence (AI) algorithms have the capability to examine extensive datasets and detect trends in biofilm formation and resistance mechanisms. This can aid in the creation of more potent antimicrobial drugs. AI models analyze complex datasets, predict biofilm formation, and guide the design of personalized treatment strategies by identifying resistance mechanisms and therapeutic targets with exceptional precision. This review provides an integrative perspective on biofilm formation mechanisms and their role in infections, highlighting the innovative applications of AI in this domain. By integrating data from diverse biological systems, AI accelerates drug discovery, optimizes treatment regimens, and enables real-time monitoring of biofilm dynamics. From predictive analytics to personalized care, we explore how AI enhances biofilm diagnostics and introduces precision medicine in biofilm-associated infections. This approach not only addresses the limitations of traditional methods but also paves the way for revolutionary advancements in infection control, antimicrobial resistance management, and improved patient outcomes.

Dextran guanidinylated carbon dots with antibacterial and immunomodulatory activities as eye drops for the topical treatment of MRSA-induced infectious keratitis

Bacterial keratitis (BK) develops rapidly and can cause serious consequences, requiring timely and efficient treatment. As the main treatment strategy, antibiotic eye drops are still plagued by bacterial resistance by biofilms and failure to modulate immunity. Herein, dextran guanidinylated carbon dots (DG-CDs) with antimicrobial and immunomodulatory properties were developed. DG-CDs with the graphitized core-like structure with the ordered arrangement of carbon atoms and surface groups of CN, COC, and -OH were thoroughly characterized and modeled as a graphene-like sheet. DG-CDs exhibited strong antimicrobial and anti-biofilm activities with a minimum inhibitory concentration (MIC) of 5 μg/mL against methicillin-resistant Staphylococcus aureus (MRSA). Molecular docking based on well-characterized structures of DG-CDs revealed that DG-CDs had strong affinity for key bacterial proteins including FtsA, IcaA and ArgA, which were confirmed by corresponding RT-qPCR and transcriptomics. Furthermore, DG-CDs regulated macrophage polarization by inhibiting the M1 subtype and promoting the transition to the M2 subtype. In vivo experiments illustrated that DG-CDs used as eye drops significantly attenuated corneal infection, enhanced the expression of anti-inflammatory factors, and effectively promoted corneal repair in MRSA-infected BK. Overall, this study provides a promising antibacterial nanomaterial with clarified properties and acting mechanism for treating BK as eye drops. STATEMENT OF SIGNIFICANCE: Besides bacterial invasion, bacterial keratitis (BK) also suffers from immune imbalance, which further impairs corneal healing. Current antibiotic eye drops are plagued by bacterial resistance and their inability to modulate immunity. Herein, dextran guanidinylated carbon dots (DG-CDs) with dual functions of antimicrobial and immunomodulatory were developed for treating MRSA infected BK. DG-CDs, with clarified structure and surface groups, exhibited strong antimicrobial activity and no detectable resistance. Molecular docking, based on well-characterized structures of DG-CDs, was achieved to reveal the antibacterial mechanism, which was subsequently confirmed by RT-qPCR and transcriptomics. In addition, DG-CDs exhibited an effective healing ability in an MRSA-infected rat keratitis model by exerting antibacterial activity and regulating macrophage polarization from M1 type to M2 type. DG-CDs represent a promising antibacterial nanomedicine with clarified properties and acting mechanism for treating bacterial infection.

Multifunctional (Co3Fe)(S2)4-ion-microneedle patch: Synergistic antimicrobial, anti-inflammatory and cell proliferation for accelerating wound healing

Preventing bacterial infection and accelerating wound closure are critical for wound healing. Herein, a novel multifunctional polyvinyl alcohol-polyvinylpyrrolidone (PVA-PVP) microneedle (MN) patch embedded with enzyme-like activity (Co3Fe)(S2)4 (CFS) nanoparticles and metal ions (Co2+ and Fe3+) was systematically synthesized for the management of bacteria-infected wounds. CFS regulated redox homeostasis and achieved bacterial eradication while concomitantly alleviating oxidative damage. Specifically, CFS generated reactive oxygen species (ROS) to eliminate bacteria and concurrently attenuated cellular inflammation by scavenging ROS through their superoxide dismutase-like (SOD) activity. Meanwhile, the results of RNA transcriptome sequencing and quantitative real-time polymerase chain reaction (qRT-PCR) analyses indicated that Co2+ and Fe3+ can inhibit inflammatory responses in mice by modulating the IL-17 and NF-κB signaling pathways. Therefore, CFS-ion-MN significantly enhanced the healing of wounds infected with methicillin-resistant Staphylococcus aureus (MRSA) in mice model without eliciting systemic toxicity. Overall, this study offers an innovative methodology for the development of composite materials for the effective treatment of wounds.

Developing antibacterial HB43 peptide-loaded chitosan nanoparticles for biofilm treatment

Biofilm-associated infections on medical devices are challenging to treat. Therefore, innovative treatment approaches are needed to penetrate biofilms and eliminate bacteria. With this study, we developed chitosan nanoparticles (CNPs) encapsulating the antibacterial peptide HB43 at increasing CNP/peptide ratios (from 1 to 4 % for P1-CNP, P2-CNP, and P4-CNP, respectively) using the ion gelation method. Our goal was to enhance antibacterial drug delivery inside a methicillin-resistant Staphylococcus aureus (MRSA) biofilm. Our analysis showed a direct correlation between the encapsulation efficacy of HB43 and the physical properties of the CNPs, such as size and zeta potential. P1-CNP was identified as the optimal formulation, characterized by its small size, high encapsulation efficiency, and cationic surface charge. Release studies indicated that HB43 was released in a sustained manner particularly under acidic conditions, which enhanced therapeutic efficacy. We tested the P1-CNP in culture media with pH levels of 7.4 and 5.5 to assess the pH responsiveness of the CNPs and mimic the infection environment. Both conditions showed that the HB43 loaded-CNPs effectively reduced bacterial populations in a dose-dependent manner, with up to a 99.99 % reduction in bacterial load. This study offers a promising new strategy for managing biofilm-associated infections and addressing antibiotic resistance by using CNPs loaded with HB43.

The Effect of the Ratio of Butylene Succinate and Dilinoleic Diol in Their Copolyester (PBS-DLS) on the Physicochemical Properties and Biofilm Formation

Biofilm-forming microorganisms pose a severe threat in the food and medical industries, among others. In this paper, the research materials were poly(butylene succinate-dilinoleic succinate) (PBS-DLS) copolymers with variable hard and soft segment weight ratios (90:10, 70:30, and 50:50). Polymeric films were prepared by the solvent casting method. Selected physicochemical properties and the tendency to form biofilm on the polymer surface were investigated. As the amount of DLS soft segments in the polymer matrix increased, changes in the FTIR-ATR spectra (signal intensity), surface (SEM), and phase transition (DSC) were observed. The higher the content of the DLS segment, the lower the transition temperatures and the smoother the film's surface. These factors resulted in a significant reduction in the amount of biofilm formed on the material's surface and a decrease in the metabolic activity of microorganisms present in the biofilm and SEM micrographs. The obtained PBS-DLS films have great potential in the food and medical packaging industries.

Peroxidase-like copper-doped carbon-dots embedded in hydrogels for stimuli-responsive bacterial biofilm elimination and wound healing

Bacterial biofilms and their microenvironment are significant challenges that must be faced in the design of antibacterial drugs. Microenvironment-responsive mimetic peroxidases (POD) have been demonstrated to be an efficient solution to eliminating bacterial biofilms. However, they inevitably require additional H2O2 and/or acid due to the poor permeabilities towards biofilms. Herein, we report POD-like copper-doped carbon dots (named CuCD1) synthesized through a facile microwave-assisted carbonization manner. The characteristics of ultrasmall size (< 5 nm) and positive charge enabled it to possess good penetrability toward bacterial biofilm. As expected, CuCD1 showed great damage to bacteria due to the generation of hydroxyl radicals (•OH), which originated from the catalytic decomposition of endogenous H2O2 under a weak acid bacterial biofilm microenvironment. This highly increased oxidative stress resulted in the alteration of cell membrane permeability, subsequent cell death, and the final eradication of bacterial biofilm and the exposed bacteria. Moreover, to verify the practicality in vivo, CuCD1 was introduced to a routine hydrogel that was crosslinked by carboxymethyl chitosan (CMCS) and oxidized dextran (ODEX). In comparison with the control groups, the composite hydrogel, i.e., CuCD1-CMCS-ODEX revealed better antibacterial performance and thus accelerated wound healing and collagen disposition. This work would open opportunities to design CDs-based biofilm microenvironment-responsive antibacterial nanoagents. STATEMENT OF SIGNIFICANCE: (1) Ultrasmall size, positively charged, peroxidase (POD)-like CuCD1 were designed and harvested by a facile microwave-assisted carbonization method. (2) CuCD1 revealed a competitive in vitro antibacterial performance, good penetrability, and microenvironment-responsive clearing capacity towards bacterial biofilm. (3) By composing with CMCS-ODEX hydrogel, the composite hydrogel could continuously eliminate bacteria, promote wound healing, as well as collagen disposition. (4) This work would provide a new strategy in the design of CDs-based biofilm microenvironment-responsive antibacterial nano-agents.

Tea tree oil nanoemulsion targets AgrA protein potentiates amoxicillin efficacy against methicillin-resistant Staphylococcus aureus

The excessive utilization of antibiotics gives rise to the development of bacterial resistance, the deterioration of animal immune functions, the increase in mortality rates, and the undermining of human immunity. Therefore, there is an urgent necessity to explore new antimicrobial agents or alternatives to tackle bacterial resistance. We investigated tea tree oil (TTO), a pure natural plant essential oil extracted from Melaleuca leaves, which exerted efficient antibacterial activities. However, the poor solubility and high volatility of TTO limited the clinical application. Therefore, tea tree oil and Tween 80 were formulated into a stable nanoemulsion (Nano TTO). We attested that Nano TTO, as an antibiotic adjuvant, enhanced the antibacterial activity of amoxicillin (AMX) against methicillin-resistant Staphylococcus aureus (MRSA) and inhibited the formation of biofilms. Mechanistic studies proved that the Nano TTO potentiation effect on AMX was primarily the result of inhibition of the Agr expression by targeting the accessory regulator AgrA. Furthermore, Nano TTO effectively boosts the efficacy of amoxicillin in the mouse septicaemia model and mouse skin wound infection model. Overall, these results revealed the potential of Nano TTO as an adjuvant to evade multidrug-resistant bacterial pathogens and improve treatment outcomes for drug-resistant infections.

Synergistic anti-biofilm strategy based on essential oils and its application in the food industry

The microbial biofilm can induce a variety of food safety problems, and cause huge economic losses. Essential oils (EOs) not only have broad-spectrum antibacterial activity but also have a good ability to inhibit biofilm. However, the addition dose of EOs in practical application usually exceeds their flavor threshold, resulting in the appearance of undesired flavor. Therefore, synergistic antimicrobial may be a potential strategy to improve the antibacterial activity of EOs and to reduce their dosage. This paper focuses on the analysis of the synergistic anti-biofilm strategies based on EOs. Based on these, the action mechanism of EOs against biofilm and other commonly used anti-biofilm strategies in the food industry are summarized. The anti-biofilm mechanism of EOs is mainly related to inhibiting the synthesis of extracellular polysaccharides and proteins, destroying biofilm structure, inhibiting the metabolic activity of biofilm, inhibiting quorum sensing (QS) and regulating the formation of biofilm and the expression of toxicity-related genes. At present, the commonly used anti-biofilm strategies in the food industry mainly include physical strategies, chemical strategies and biological strategies, among which the combined application of different strategies is the future development trend. In particular, the synergistic anti-biofilm strategy based on EOs has shown great application value in the food industry. To sum up, some new information in this paper will give guidance and provide more reference for the development of efficient biofilm regulation strategies in future.

Design of acidic activation-responsive charge-switchable carbon dots and validation of their antimicrobial activity

Bacterial biofilms play a crucial role in the emergence of antibiotic resistance and the persistence of chronic infections. The challenge of effectively eradicating bacterial biofilms while ensuring minimal toxicity to normal cells persists. Carbon-based artificial nanoenzymes have attracted considerable attention as emerging nanotheranostic agents, owing to their biocompatibility, cost-effectiveness, and straightforward synthesis. In this study, we have developed a multifunctional carbon dots (CDs) system, specifically CDs functionalized with 1-(3-aminopropyl) imidazole (API), termed CDs-API. This system demonstrates acid-activated antibiofilm activity. The CDs-API were synthesized from chlorogenic acid (ChA), a bioactive compound naturally occurring in coffee, and subsequently functionalized with API to achieve charge-switchable properties under acidic conditions. This distinctive feature enables CDs-API to efficiently penetrate bacterial biofilms and selectively target the colonized bacteria. The enzyme-like activity of CDs-API effectively consumes high levels of glutathione (GSH) within the biofilm, leading to the accumulation of reactive oxygen species (ROS). Consequently, this process degrades the extracellular polymeric substance (EPS) matrix, damages bacterial DNA and protein structures, and disrupts the redox balance, ultimately leading to bacterial cell death. Experimental results demonstrated that CDs-API effectively inhibited the growth of methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (PAE) while promoting wound healing with minimal damage to healthy tissues. The acid-activated charge-switchable capability of CDs-API provides superior antibacterial efficacy compared to traditional antibiotics, rendering it a promising candidate for the treatment of bacterial biofilm infections.

Helicobacter pylori: Routes of Infection, Antimicrobial Resistance, and Alternative Therapies as a Means to Develop Infection Control

Helicobacter pylori (H. pylori) is a Gram-negative, spiral-shaped bacterium that colonizes the gastric epithelium and is associated with a range of gastrointestinal disorders, exhibiting a global prevalence of approximately 50%. Despite the availability of treatment options, H. pylori frequently reemerges and demonstrates increasing antibiotic resistance, which diminishes the efficacy of conventional therapies. Consequently, it is imperative to explore non-antibiotic treatment alternatives to mitigate the inappropriate use of antibiotics. This review examines H. pylori infection, encompassing transmission pathways, treatment modalities, antibiotic resistance, and eradication strategies. Additionally, it discusses alternative therapeutic approaches such as probiotics, anti-biofilm agents, phytotherapy, phototherapy, phage therapy, lactoferrin therapy, and vaccine development. These strategies aim to reduce antimicrobial resistance and enhance treatment outcomes for H. pylori infections. While alternative therapies can maintain low bacterial levels, they do not achieve complete eradication of H. pylori. These therapies are designed to bolster the immune response, minimize side effects, and provide gastroprotective benefits, rendering them suitable for adjunctive use alongside conventional treatments. Probiotics may serve as adjunctive therapy for H. pylori; however, their effectiveness as a monotherapy is limited. Photodynamic and phage therapies exhibit potential in targeting H. pylori infections, including those caused by drug-resistant strains, without the use of antibiotics. The development of a reliable vaccine is also critical for the eradication of H. pylori. This review identifies candidate antigens such as VacA, CagA, and HspA, along with various vaccine formulations, including vector-based and subunit vaccines. Some vaccines have demonstrated efficacy in clinical trials, while others have shown robust immune protection in preclinical studies. Nevertheless, each of the aforementioned alternative therapies requires thorough preclinical and clinical evaluation to ascertain their efficacy, side effects, cost-effectiveness, and patient compliance.

Antibiotic biocompatibility assay and anti-biofilm strategies for Pseudomonas aeruginosa infection in bioengineered artificial skin substitutes

OBJECTIVES

Bioengineered artificial skin substitutes (BASS) are an advanced therapy for treating extensively burned patients. Pseudomonas aeruginosa (P. aeruginosa) infections represent a major challenge in these patients as formation of biofilms impede wound healing and perpetuate a chronic inflammatory state. Here we assessed antibiotics (alone or in combination) with respect to cytotoxicity, as well as antimicrobial efficacy in P. aeruginosa biofilm formed on infection of BASS.

METHODS

Cell viability, structure and functionality were evaluated using microscopy and trans-epidermal water loss analyses, respectively. BASS were established and infected for 24 h to allow P. aeruginosa biofilm formation, after which two antimicrobial approaches, treatment and prevention, were tested. In the latter, antibiotics were added to BASS before infection. The antimicrobial effect was determined using real-time calorimetry.

RESULTS

In dose-response experiments, 1.25 mg/mL amikacin, 0.02 mg/mL ciprofloxacin, 0.051 mg/mL colistin, 1 mg/mL meropenem and colistin in combination with either amikacin, ciprofloxacin and meropenem did not affect BASS' viability, structure and functionality. All antibiotics, except colistin, showed effective antimicrobial activity at these non-cytotoxic concentrations. For concentrations below the highest non-cytotoxic ones, successive treatments resulted in higher bacterial metabolic rates. Only the combinations managed to eradicate the infection with repeated treatments. With respect to prevention of infection, all antibiotics at the highest non-cytotoxic concentrations and the combinations were effective. This preventive capacity was maintained for at least 5 days.

CONCLUSION

The findings highlight the potential for developing BASS with antimicrobial properties that can prevent infections during wound healing in burn patients.

Edible thermosensitive chitosan/hydroxypropyl β-cyclodextrin hydrogel with natural licoricidin for enhancing oral health: Biofilm disruption and demineralization prevention

Dental caries, a widespread and significantly detrimental health condition, is characterized by demineralization, pain, compromised tooth functionality, and various other adverse effects. Licoricidin (LC), a natural isoflavonoid, demonstrates potent antimicrobial properties for maintaining oral health. However, its practical application is significantly hindered by its limited water solubility and susceptibility to removal within the oral environment. To tackle this issue, we developed a delivery oral system by an edible thermosensitive chitosan- disodium beta-glycerol phosphate pentahydrate (CS/β-GP) hydrogel to load LC/Hydroxypropyl beta-cyclodextrin (HP-β-CD) inclusion complexes. These hydrogels (LC/HP-β-CD/CS/β-GP) could solidify rapidly at oral temperature and sustainably release LC, thereby preventing its rapid clearance from the oral cavity. We confirmed the significant antibacterial activity of this hydrogel against Streptococcus mutans and Staphylococcus aureus. Additionally, the HP-β-CD combination enhanced LC to penetrate bacterial biofilms and inhibit biofilm growth, leading to leakage of cellular proteins and DNA. Additionally, we studied the effect of LC/HP-β-CD/CS/β-GP on intracellular ROS levels and MMP, comprehensively exploring its antimicrobial mechanism. Furthermore, LC/HP-β-CD/CS/β-GP exhibited the ability to inhibit demineralization and demonstrated excellent biocompatibility. In summary, this study presented a safer approach to oral delivering bioactive substances, offering a promising strategy for enhanced oral health and safety.

Therapeutic efficacy of chitosan-based hybrid nanomaterials to treat microbial biofilms and their infections - A review

Antimicrobial resistance, the biggest issue facing the global healthcare sector, quickly emerged and spread due to the frequent use of antibiotics in regular treatments. The investigation of polymer-based nanomaterials as possible antibiofilm treatment agents is prompted by the growing ineffectiveness of conventional therapeutic techniques against these resistant bacteria species. So far, several articles have been published on microbial biofilm eradication using various polymer-based nanomaterials due to their therapeutic efficacy and biocompatibility nature. Despite their potential, a comprehensive review of the chitosan-based hybrid nanomaterials to treat microbial biofilms and their infections is lacking. This review provides a comprehensive investigation of the current state of therapeutic efficacy, various nanoformulations, advantages, limitations, and regulations of chitosan-based hybrid nanomaterials for biofilm treatment. Special attention is given to the application of chitosan-based nanomaterials in wound care, urinary tract infections, and dental biofilms are discussed, highlighting their role in managing biofilm-associated complications. Researchers will be better able to comprehend and develop unique, marketable chitosan-based nanomaterials with increased activity to treat biofilm infections in near future with the aid of this review.

Antibiotic Nanoparticles-Loaded Wound Dressings Against Pseudomonas aeruginosa's Skin Infection: A Systematic Review

Pseudomonas aeruginosa (P. aeruginosa) is a common nosocomial pathogen that can cause severe infections in critically ill patients. Due to its resistance to multiple drugs, it is challenging to treat, which can result in serious illness and death. Conventional treatments for infected wounds often involve the topical or systemic application of antibiotics, which can lead to systemic toxicity and the development of drug resistance. The combination of wound dressings that promote wound healing with nanoparticles (NPs) represents a revolutionary strategy for optimizing the safety and efficacy of antibiotics. This review assesses a systematic search to identify the latest approaches where the evaluation of wound dressings loaded with antibiotic NPs is conducted. The properties of NPs, the features of wound dressings, the antimicrobial activity and biocompatibility of the different strategies are analyzed. The results indicate that most research in this field is focused on dressings loaded with silver NPs (57.1%) or other inorganic materials (22.4%). Wound dressings loaded with polymeric NPs and carbon-based NPs represent 14.3% and 6.1% of the evaluated studies, respectively. Nevertheless, there are no clinical trials that have evaluated the efficacy of NPs-loaded wound dressings in patients. Further research is required to ensure the safety of these treatments and to translate the findings from the bench to the bedside.

Application of biofilm dispersion-based nanoparticles in cutting off reinfection

Bacterial biofilms commonly cause chronic and persistent infections in humans. Bacterial biofilms consist of an inner layer of bacteria and an autocrine extracellular polymeric substance (EPS). Biofilm dispersants (abbreviated as dispersants) have proven effective in removing the bacterial physical protection barrier EPS. Dispersants are generally weak or have no bactericidal effect. Bacteria dispersed from within biofilms (abbreviated as dispersed bacteria) may be more invasive, adhesive, and motile than planktonic bacteria, characteristics that increase the probability that dispersed bacteria will recolonize and cause reinfection. The dispersants should be combined with antimicrobials to avoid the risk of severe reinfection. Dispersant-based nanoparticles have the advantage of specific release and intense penetration, providing the prerequisite for further antibacterial agent efficacy and achieving the eradication of biofilms. Dispersant-based nanoparticles delivered antimicrobial agents for the treatment of diseases associated with bacterial biofilm infections are expected to be an effective measure to prevent reinfection caused by dispersed bacteria. KEY POINTS: • Dispersed bacteria harm and the dispersant's dispersion mechanisms are discussed. • The advantages of dispersant-based nanoparticles in bacteria biofilms are discussed. • Dispersant-based nanoparticles for cutting off reinfection in vivo are highlighted.

The combination of allicin with domiphen is effective against microbial biofilm formation

Background

Microorganisms in biofilms are particularly difficult to control because of their increased survival and antibiotic resistance. Allicin and domiphen were employed to inhibit the microbial growth and biofilm formation of Staphylococcus aureus, Escherichia coli, and Candida albicans strains.

Methods

Broth microdilution method and checkerboard assay were conducted to determine the efficacy of allicin combined with domiphen against S. aureus, E. coli, and C. albicans. Microbial biofilm formation was measured using the crystal violet staining method and fluorescence microscopy. And the total viable count of the biofilm cells on material surface after the treatment with antimicrobial reagents was calculated with the plate count technique.

Results

The two drugs showed synergistic effects against the pathogens with a fractional bactericidal concentration of less than 0.38. The combination of 64 μg/mL allicin with 1 μg/mL domiphen dispersed over 50% of the biofilm mass of S. aureus, E. coli, and C. albicans. In addition, the drug combination reduced the total viable counts of E. coli and C. albicans biofilm cells on stainless steel and polyethylene surfaces by more than 102 CFU/mL.

Conclusion

The combination of allicin and domiphen is an effective strategy for efficiently decreasing biofilms formation on various industrial materials surfaces.

Nanotechnology-driven strategies to enhance the treatment of drug-resistant bacterial infections

The misuse of antibiotics has led to increased bacterial resistance, posing a global public health crisis and seriously endangering lives. Currently, antibiotic therapy remains the most common approach for treating bacterial infections, but its effectiveness against multidrug-resistant bacteria is diminishing due to the slow development of new antibiotics and the increase of bacterial drug resistance. Consequently, developing new a\ntimicrobial strategies and improving antibiotic efficacy to combat bacterial infection has become an urgent priority. The emergence of nanotechnology has revolutionized the traditional antibiotic treatment, presenting new opportunities for refractory bacterial infection. Here we comprehensively review the research progress in nanotechnology-based antimicrobial drug delivery and highlight diverse platforms designed to target different bacterial resistance mechanisms. We also outline the use of nanotechnology in combining antibiotic therapy with other therapeutic modalities to enhance the therapeutic effectiveness of drug-resistant bacterial infections. These innovative therapeutic strategies have the potential to enhance bacterial susceptibility and overcome bacterial resistance. Finally, the challenges and prospects for the application of nanomaterial-based antimicrobial strategies in combating bacterial resistance are discussed. This article is categorized under: Biology-Inspired Nanomaterials > Nucleic Acid-Based Structures Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease.

Exosomes as Promising Therapeutic Tools for Regenerative Endodontic Therapy

Pulpitis is a common and frequent disease in dental clinics. Although vital pulp therapy and root canal treatment can stop the progression of inflammation, they do not allow for genuine structural regeneration and functional reconstruction of the pulp-dentin complex. In recent years, with the development of tissue engineering and regenerative medicine, research on stem cell-based regenerative endodontic therapy (RET) has achieved satisfactory preliminary results, significantly enhancing its clinical translational prospects. As one of the crucial paracrine effectors, the roles and functions of exosomes in pulp-dentin complex regeneration have gained considerable attention. Due to their advantages of cost-effectiveness, extensive sources, favorable biocompatibility, and high safety, exosomes are considered promising therapeutic tools to promote dental pulp regeneration. Accordingly, in this article, we first focus on the biological properties of exosomes, including their biogenesis, uptake, isolation, and characterization. Then, from the perspectives of cell proliferation, migration, odontogenesis, angiogenesis, and neurogenesis, we aim to reveal the roles and mechanisms of exosomes involved in regenerative endodontics. Lastly, immense efforts are made to illustrate the clinical strategies and influencing factors of exosomes applied in dental pulp regeneration, such as types of parental cells, culture conditions of parent cells, exosome concentrations, and scaffold materials, in an attempt to lay a solid foundation for exploring and facilitating the therapeutic strategy of exosome-based regenerative endodontic procedures.

Addressing Antimicrobial Properties in Guided Tissue/Bone Regeneration Membrane: Enhancing Effectiveness in Periodontitis Treatment

Guided tissue regeneration (GTR) and guided bone regeneration (GBR) are the two surgical techniques generally used for periodontitis disease treatment. These techniques are based on a barrier membrane to direct the growth of new bone and gingival tissue at sites with insufficient volumes or dimensions of bone or gingiva for proper function, esthetics, or prosthetic restoration. Numerous studies have highlighted biocompatibility, space-creation, cell-blocking, bioactivity, and proper handling as essential characteristics of a membrane's performance. Given that bacterial infection is the primary cause of periodontitis, we strongly believe that addressing the antimicrobial properties of these membranes is of utmost importance. Indeed, the absence of effective inhibition of periodontal pathogens has been recognized as a primary factor contributing to the failure of GTR/GBR membranes. Therefore, we suggest considering antimicrobial properties as one of the key factors in the design of GTR/GBR membranes. Antibiotics are potent medications frequently administered systemically to combat microbes and mitigate bacterial infections. Nevertheless, the excessive use of antibiotics has resulted in a surge in bacterial resistance. To overcome this challenge, alternative antibacterial substances have been developed. In this review, we explore the utilization of alternative substances with antimicrobial properties for topical application in membranes. The use of antibacterial nanoparticles, phytochemical compounds, and antimicrobial peptides in this context was investigated. By carefully selecting and integrating antimicrobial agents into GTR/GBR membranes, we can significantly enhance their effectiveness in combating periodontitis. These antibacterial substances not only act as barriers against pathogenic bacteria but also promote the process of periodontal healing.

Nanotechnology's frontier in combatting infectious and inflammatory diseases: prevention and treatment

Inflammation-associated diseases encompass a range of infectious diseases and non-infectious inflammatory diseases, which continuously pose one of the most serious threats to human health, attributed to factors such as the emergence of new pathogens, increasing drug resistance, changes in living environments and lifestyles, and the aging population. Despite rapid advancements in mechanistic research and drug development for these diseases, current treatments often have limited efficacy and notable side effects, necessitating the development of more effective and targeted anti-inflammatory therapies. In recent years, the rapid development of nanotechnology has provided crucial technological support for the prevention, treatment, and detection of inflammation-associated diseases. Various types of nanoparticles (NPs) play significant roles, serving as vaccine vehicles to enhance immunogenicity and as drug carriers to improve targeting and bioavailability. NPs can also directly combat pathogens and inflammation. In addition, nanotechnology has facilitated the development of biosensors for pathogen detection and imaging techniques for inflammatory diseases. This review categorizes and characterizes different types of NPs, summarizes their applications in the prevention, treatment, and detection of infectious and inflammatory diseases. It also discusses the challenges associated with clinical translation in this field and explores the latest developments and prospects. In conclusion, nanotechnology opens up new possibilities for the comprehensive management of infectious and inflammatory diseases.

Antimicrobial Activity of Citrate-Coated Cerium Oxide Nanoparticles

The purpose of this study was to investigate the antimicrobial activity of citrate-stabilized sols of cerium oxide nanoparticles at different concentrations via different microbiological methods and to compare the effect with the peroxidase activity of nanoceria for the subsequent development of a regeneration-stimulating medical and/or veterinary wound-healing product providing new types of antimicrobial action. The object of this study was cerium oxide nanoparticles synthesized from aqueous solutions of cerium (III) nitrate hexahydrate and citric acid (the size of the nanoparticles was 3-5 nm, and their aggregates were 60-130 nm). Nanoceria oxide sols with a wide range of concentrations (10-1-10-6 M) as well as powder (the dry substance) were used. Both bacterial and fungal strains (Bacillus subtilis, Bacillus cereus, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Proteus vulgaris, Candida albicans, Aspergillus brasielensis) were used for the microbiological studies. The antimicrobial activity of nanoceria was investigated across a wide range of concentrations using three methods sequentially; the antimicrobial activity was studied by examining diffusion into agar, the serial dilution method was used to detect the minimum inhibitory and bactericidal concentrations, and, finally, gas chromatography with mass-selective detection was performed to study the inhibition of E. coli's growth. To study the redox activity of different concentrations of nanocerium, we studied the intensity of chemiluminescence in the oxidation reaction of luminol in the presence of hydrogen peroxide. As a result of this study's use of the agar diffusion and serial dilution methods followed by sowing, no significant evidence of antimicrobial activity was found. At the same time, in the current study of antimicrobial activity against E. coli strains using gas chromatography with mass spectrometry, the ability of nanoceria to significantly inhibit the growth and reproduction of microorganisms after 24 h and, in particular, after 48 h of incubation at a wide range of concentrations, 10-2-10-5 M (48-95% reduction in the number of microbes with a significant dose-dependent effect) was determined as the optimum concentration. A reliable redox activity of nanoceria coated with citrate was established, increasing in proportion to the concentration, confirming the oxidative mechanism of the action of nanoceria. Thus, nanoceria have a dose-dependent bacteriostatic effect, which is most pronounced at concentrations of 10-2-10-3 M. Unlike the effects of classical antiseptics, the effect was manifested from 2 days and increased during the observation. To study the antimicrobial activity of nanomaterials, it is advisable not to use classical qualitative and semi-quantitative methods; rather, the employment of more accurate quantitative methods is advised, in particular, gas chromatography-mass spectrometry, during several days of incubation.

Drug-loaded lipid nanoparticles improve the removal rates of the Staphylococcus aureus biofilm

Biofilms of the foodborne pathogen Staphylococcus aureus show improved resistance to antibiotics and are difficult to eliminate. To enhance antibacteria and biofilm dispersion via extracellular matrix diffusion, a new lipid nanoparticle was prepared, which employed a mixture of phospholipids and a 0.8% surfactin shell. In the lipid nanoparticle, 31.56 μg mL-1 of erythromycin was encapsulated. The lipid nanoparticle size was approximately 52 nm and the zeta-potential was -67 mV, which was measured using a Marvin laser particle size analyzer. In addition, lipid nanoparticles significantly dispersed the biofilms of S. aureus W1, CICC22942, and CICC 10788 on the surface of stainless steel, reducing the total viable count of bacteria in the biofilms by 103 CFU mL-1 . In addition, the lipid nanoparticle can remove polysaccharides and protein components from the biofilm matrix. The results of laser confocal microscopy showed that the lipid nanoparticles effectively killed residual bacteria in the biofilms. Thus, to thoroughly eliminate biofilms on material surfaces in food factories to avoid repeated contamination, drug-lipid nanoparticles present a suitable method to achieve this.

Quorum Sensing Interference Assisted Therapy-Based Magnetic Hyperthermia Amplifier for Synergistic Biofilm Treatment

Biofilms offer bacteria a physical and metabolic barrier, enhancing their tolerance to external stress. Consequently, these biofilms limit the effectiveness of conventional antimicrobial treatment. Recently, quorum sensing (QS) has been linked to biofilm's stress response to thermal, oxidative, and osmotic stress. Herein, a multiple synergistic therapeutic strategy that couples quorum sensing interference assisted therapy (QSIAT)-mediated enhanced thermal therapy with bacteria-triggered immunomodulation in a single nanoplatform, is presented. First, as magnetic hyperthermia amplifier, hyaluronic acid-coated ferrite (HA@MnFe2 O4 ) attenuates the stress response of biofilm by down-regulating QS-related genes, including agrA, agrC, and hld. Next, the sensitized bacteria are eliminated with magnetic heat. QS interference and heat also destruct the biofilm, and provide channels for further penetration of nanoparticles. Moreover, triggered by bacterial hyaluronidase, the wrapped hyaluronic acid (HA) decomposes into disaccharides at the site of infection and exerts healing effect. Thus, by reversing the bacterial tissue invasion mechanism for antimicrobial purpose, tissue regeneration following pathogen invasion and thermal therapy is successfully attained. RNA-sequencing demonstrates the QS-mediated stress response impairment. In vitro and in vivo experiments reveal the excellent antibiofilm and anti-inflammatory effects of HA@MnFe2 O4 . Overall, QSIAT provides a universal enhancement strategy for amplifying the bactericidal effects of conventional therapy via stress response interference.

Nanomedicine against biofilm infections: A roadmap of challenges and limitations

Microbial biofilms are complex three-dimensional structures where sessile microbes are embedded in a polymeric extracellular matrix. Their resistance toward the host immune system as well as to a diverse range of antimicrobial treatments poses a serious health and development threat, being in the top 10 global public health threats declared by the World Health Organization. In an effort to combat biofilm-related microbial infections, several strategies have been developed to independently eliminate biofilms or to complement conventional antibiotic therapies. However, their limitations leave room for other treatment alternatives, where the application of nanotechnology to biofilm eradication has gained significant relevance in recent years. Their small size, penetration efficiency, and the design flexibility that they present makes them a promising alternative for biofilm infection treatment, although they also present set-backs. This review aims to describe the main possibilities and limitations of nanomedicine against biofilms, while covering the main aspects of biofilm formation and study, and the current therapies for biofilm treatment. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials Toxicology and Regulatory Issues in Nanomedicine > Regulatory and Policy Issues in Nanomedicine.

Mechanisms of antibiotic resistance in Pseudomonas aeruginosa biofilms

Pseudomonas aeruginosa is a major cause of life-threatening acute infections and life-long lasting chronic infections. The characteristic biofilm mode of life in P. aeruginosa chronic infections severely limits the efficacy of antimicrobial therapies, as it leads to intrinsic tolerance, involving physical and physiological factors in addition to biofilm-specific genes that can confer a transient protection against antibiotics promoting the development of resistance. Indeed, a striking feature of this pathogen is the extraordinary capacity to develop resistance to nearly all available antibiotics through the selection of chromosomal mutations, evidenced by its outstanding and versatile mutational resistome. This threat is dramatically amplified in chronic infections, driven by the frequent emergence of mutator variants with enhanced spontaneous mutation rates. Thus, this mini review is focused on describing the complex interplay of antibiotic resistance mechanisms in P. aeruginosa biofilms, to provide potentially useful information for the design of effective therapeutic strategies.

Overview of the effects and mechanisms of NO and its donors on biofilms

Microbial biofilm is undoubtedly a challenging problem in the food industry. It is closely associated with human health and life, being difficult to remove and antibiotic resistance. Therefore, an alternate method to solve these problems is needed. Nitric oxide (NO) as an antimicrobial agent, has shown great potential to disrupt biofilms. However, the extremely short half-life of NO in vivo (2 s) has facilitated the development of relatively more stable NO donors. Recent studies reported that NO could permeate biofilms, causing damage to cellular biomacromolecules, inducing biofilm dispersion by quorum sensing (QS) pathway and reducing intracellular bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP) levels, and significantly improving the bactericidal effect without drug resistance. In this review, biofilm hazards and formation processes are presented, and the characteristics and inhibitory effects of NO donors are carefully discussed, with an emphasis on the possible mechanisms of NO resistance to biofilms and some advanced approaches concerning the remediation of NO donor deficiencies. Moreover, the future perspectives, challenges, and limitations of NO donors were summarized comprehensively. On the whole, this review aims to provide the application prospects of NO and its donors in the food industry and to make reliable choices based on these available research results.

Recent Advances of Composite Nanomaterials for Antibiofilm Application

A biofilm is a microbial community formed by bacteria that adsorb on the surface of tissues or materials and is wrapped in extracellular polymeric substances (EPS) such as polysaccharides, proteins and nucleic acids. As a protective barrier, the EPS can not only prevent the penetration of antibiotics and other antibacterial agents into the biofilm, but also protect the bacteria in the biofilm from the attacks of the human immune system, making it difficult to eradicate biofilm-related infections and posing a serious threat to public health. Therefore, there is an urgent need to develop new and efficient antibiofilm drugs. Although natural enzymes (lysozyme, peroxidase, etc.) and antimicrobial peptides have excellent bactericidal activity, their low stability in the physiological environment and poor permeability in biofilms limit their application in antibiofilms. With the development of materials science, more and more nanomaterials are being designed to be utilized for antimicrobial and antibiofilm applications. Nanomaterials have great application prospects in antibiofilm because of their good biocompati-bility, unique physical and chemical properties, adjustable nanostructure, high permeability and non-proneness to induce bacterial resistance. In this review, with the application of composite nanomaterials in antibiofilms as the theme, we summarize the research progress of three types of composite nanomaterials, including organic composite materials, inorganic materials and organic-inorganic hybrid materials, used as antibiofilms with non-phototherapy and phototherapy modes of action. At the same time, the challenges and development directions of these composite nanomaterials in antibiofilm therapy are also discussed. It is expected we will provide new ideas for the design of safe and efficient antibiofilm materials.

Biodegradation of polyurethanes by Serratia liquefaciens L135 and its polyurethanase: In silico and in vitro analyses

Polyurethanes (PUs) are found in many everyday products and their disposal leads to environmental accumulation. Therefore, there is an urgent need to develop ecologically sustainable techniques to biodegrade and recycle this recalcitrant polymer and replace traditional methods that form harmful by-products. Serratia liquefaciens L135 secretes a polyurethanase with lipase activity, and this study explores the biodegradation of PUs by this bacterium and its enzyme through in silico and in vitro analyses. PUs monomers and tetramers were constructed in silico and tested with modeled and validated structure of the polyurethanase from S. liquefaciens. The molecular docking showed that all PUs monomers presented favorable interactions with polyurethanase (values of binding energy between -84.75 and -121.71 kcal mol-1), including PU poly[4,4'-methylenebis (phenyl isocyanate)-alt-1,4-butanediol/di (propylene glycol)/polycaprolactone] (PCLMDI). Due to repulsive steric interactions, tetramers showed less favorable interactions (values between 24.26 and -45.50 kcal mol-1). In vitro analyses evaluated the biodegradation of PUs: Impranil® and PCLMDI; this latter showed high binding energy with this polyurethanase in silico. The biodegradation of Impranil® by S. liquefaciens and its partially purified polyurethanase was confirmed in agar by forming a transparent halo. Impranil® disks inoculated with S. liquefaciens and incubated at 30 °C for six days showed rupture of the PU structure, possibly due to the formation of cracks visualized by scanning electron microscopy (SEM). PCLMDI films were also biodegraded by S. liquefaciens after 60 days of incubation, with the formation of pores and cracks visualized by SEM. The biodegradation may have occurred due to the action of polyurethanase produced by this bacterium. This work provides essential information on the potential of S. liquefaciens to biodegrade PUs through in silico analyses combined with in vitro analyses.

A Sustained-Release Nanosystem with MRSA Biofilm-Dispersing and -Eradicating Abilities Accelerates Diabetic Ulcer Healing

Introduction

Drug-resistant bacterial infections and biofilm formation play important roles in the pathogenesis of diabetic refractory wounds. Tea tree oil (TTO) exhibits antimicrobial, antimycotic, and antiviral activities, especially against common clinically resistant strains, such as methicillin-resistant Staphylococcus aureus (MRSA), making it a potential natural antimicrobial for the treatment of acute and chronic wounds. However, TTO is insoluble in water, volatile, light-sensitive, and cytotoxic. While previous macroscopic studies have focused on sterilization with TTO, none have sought to alter its structure or combine it with other materials to achieve sustained release.

Methods

Electrospun TTO nanoliposomes (TTO-NLs), arranged linearly via high-pressure homogenization, could stabilize the structure and performance of TTO to achieve slow drug release. Herein, we established a composite nano-sustained release system, TTO-NL/polyvinyl alcohol/chitosan (TTO-NL@PCS), using high-voltage electrospinning.

Results

Compared with the control, TTO-NL@PCS exhibits higher concentrations of the active TTO drug components, terpinen-4-ol and 1,8-cineole. Owing to its increased stability and slow release, early exposure to TTO-NL@PCS increases the abundance of reactive oxygen species in vitro, ultimately causing the biofilm to disperse and completely killing MRSA without inducing cytotoxic effects to the host. Moreover, in BKS-Leprem2Cd479/Gpt mice with a whole-layer skin infection, untargeted metabolomics analysis of wound exudates reveals upregulated PGF2α/FP receptor signaling and interleukin (IL)-1β and IL-6 expression following application of the composite system. The composite also ameliorates the chemotaxis disorder in early treatment and attenuates the wound inflammatory response during the repair stage of diabetic inflammatory wounds, and upregulates VEGF expression in the wound bed.

Conclusion

TTO-NL@PCS demonstrates the remarkable potential for accelerating diabetic and MRSA-infected wound healing.

Targeting and arginine-driven synergizing photodynamic therapy with nutritional immunotherapy nanosystems for combating MRSA biofilms

The resistance and immune escape of methicillin-resistant Staphylococcus aureus (MRSA) biofilms cause recalcitrant infections. Here, we design a targeting and synergizing cascade PDT with nutritional immunotherapy nanosystems (Arg-PCN@Gel) containing PCN-224 as PDT platform for providing reactive oxygen species (ROS), incorporating arginine (Arg) as nitric oxide (NO) donor to cascade with ROS to produce more lethal ONOO- and promote immune response, and coating with gelatin as targeting agent and persistent Arg provider. The nanosystems adhered to the autolysin of MRSA and inhibited Arg metabolism by down-regulating icdA and icaA. It suppressed polysaccharide intercellular adhesin and extracellular DNA synthesis to prevent biofilm formation. The NO broke mature biofilms and helped ROS and ONOO- penetrate into biofilms to inactivate internal MRSA. Arg-PCN@Gel drove Arg to enhance immunity via inducible NO synthase/NO axis and arginase/polyamine axis and achieve efficient target treatment in MRSA biofilm infections. The targeting and cascading PDT synergized with nutritional immunotherapy provide an effective promising strategy for biofilm-associated infections.

Rapid separation and detection of Listeria monocytogenes with the combination of phage tail fiber protein and vancomycin-magnetic nanozyme

In this work, a lateral flow assay for Listeria monocytogenes was developed based on phage tail fiber protein (TFP) and triple-functional nanozyme probes with capture-separation-catalytic activity. Inspired by interaction between phage and bacteria, TFP of L. monocytogenes phage was immobilized on test line as capture molecule, which replaced traditional antibody and aptamer. After Gram-positive bacteria was captured and separated from samples by nanozyme probes modified with vancomycin (Van), TFP specifically recognized L. monocytogenes and overcame non-specific binding of Van. Special color reaction between Coomassie Brilliant Blue and bovine serum albumin which was an amplification carrier on probe was simply utilized as control zone to replace traditional control line. Relying on enzyme-like catalytic activity of nanozyme, this biosensor realized improved sensitivity and colorimetric quantitative detection with a detection limit of 10 CFU mL^-1. Analytic performance results suggested this TFP-based biosensor provided a portable, sensitive and specific strategy to detect pathogen.

Capsular polysaccharide-amikacin nanoparticles for improved antibacterial and antibiofilm performance

Natural nanoscale polysaccharide and its application have attracted much attention in recent years. In this study, we report for the first time that a novel naturally occurring capsular polysaccharide (CPS-605) from Lactobacillus plantarum LCC-605, which can self-assemble into spherical nanoparticles with an average diameter of 65.7 nm. To endow CPS-605 with more functionalities, we develop amikacin-functionalized capsular polysaccharide (CPS) nanoparticles (termed CPS-AM NPs) with improved antibacterial and antibiofilm activities against both Escherichia coli and Pseudomonas aeruginosa. They also exhibit faster bactericidal activity than AM alone. The high local positive charge density of CPS-AM NPs facilitates the interaction between the NPs and bacteria, leading to extraordinary bactericidal efficiencies (99.9 % and 100 % for E. coli and P. aeruginosa, respectively, within 30 min) by damaging the cell wall. Very interestingly, CPS-AM NPs exhibit an unconventional antibacterial mechanism against P. aeruginosa, that is, they can induce plasmolysis, along with bacterial cell surface disruption, cell inclusion release and cell death. In addition, CPS-AM NPs exhibit low cytotoxicity and negligible hemolytic activity, showing excellent biocompatibility. The CPS-AM NPs provide a new strategy for the design of next-generation antimicrobial agents that can reduce the working concentration of antibiotics to fight against bacterial resistance.

Understanding bacterial biofilms: From definition to treatment strategies

Bacterial biofilms are complex microbial communities encased in extracellular polymeric substances. Their formation is a multi-step process. Biofilms are a significant problem in treating bacterial infections and are one of the main reasons for the persistence of infections. They can exhibit increased resistance to classical antibiotics and cause disease through device-related and non-device (tissue) -associated infections, posing a severe threat to global health issues. Therefore, early detection and search for new and alternative treatments are essential for treating and suppressing biofilm-associated infections. In this paper, we systematically reviewed the formation of bacterial biofilms, associated infections, detection methods, and potential treatment strategies, aiming to provide researchers with the latest progress in the detection and treatment of bacterial biofilms.

Targeted pH-responsive chitosan nanogels with Tanshinone IIA for enhancing the antibacterial/anti-biofilm efficacy

Persistent bacterial infection caused by biofilms is one of the most serious problems that threatened human health. The development of antibacterial agents remains a challenge to penetrate biofilm and effectively treat the underlying bacterial infection. In the current study, chitosan-based nanogels were developed for encapsulating the Tanshinone IIA (TA) to enhance the antibacterial and anti-biofilm efficacy against Streptococcus mutans (S. mutans). The as-prepared nanogels (TA@CS) displayed excellent encapsulation efficiency (91.41 ± 0.11 %), uniform particle sizes (393.97 ± 13.92 nm), and enhanced positive potential (42.27 ± 1.25 mV). After being coated with CS, the stability of TA under light and other harsh environments was greatly improved. In addition, TA@CS displayed pH responsiveness, allowing it to selectively release more TA in acidic conditions. Furthermore, the positively charged TA@CS were equipped to target negatively charged biofilm surfaces and efficiently penetrate through biofilm barriers, making it promising for remarkable anti-biofilm activity. More importantly, when TA was encapsulated into CS nanogels, the antibacterial activity of TA was enhanced at least 4-fold. Meanwhile, TA@CS inhibited 72 % of biofilm formation at 500 μg/mL. The results demonstrated that the nanogels constituted CS and TA had antibacterial/anti-biofilm properties with synergistic enhanced effects, which will benefit pharmaceutical, food, and other fields.

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.

Emodin Combined with Multiple-Low-Frequency, Low-Intensity Ultrasound To Relieve Osteomyelitis through Sonoantimicrobial Chemotherapy

Treatment of osteomyelitis is still challenging, as conventional antibiotic therapy is limited by the emergence of resistant strains and the formation of biofilms. Sonoantimicrobial chemotherapy (SACT) is a novel therapy of low-frequency and low-intensity ultrasound (LFLIU) combined with a sonosensitizer. Therefore, in our study, a sonosensitizer named emodin (EM) was proposed to be combined with LFLIU to relieve acute osteomyelitis caused by methicillin-resistant Staphylococcus aureus (MRSA) through antibacterial and antibiofilm effects. The efficiencies of different intensities of ultrasound, including single (S-LFLIU, 15 min) and multiple ultrasound (M-LFLIU, 3 times for 5 min at 4-h intervals), against bacteria and biofilms were compared, contributing to developing the best treatment regimen. Our results demonstrated that EM plus S-LFLIU or M-LFLIU (EM+S-LFLIU or EM+M-LFLIU) had significant combined bactericidal and antibiofilm effects, with EM+M-LFLIU in particular exhibiting superior antibiofilm performance. Furthermore, it was suggested that EM+M-LFLIU could produce a large amount of reactive oxygen species (ROS), destroy the integrity of the bacterial membrane and cell wall, and downregulate the expression of genes involved in oxidative stress, membrane wall synthesis, and bacterial virulence, as well as that of other related genes (agrB, pbp3, sgtB, gmk, zwf, and msrA). In vivo studies, micro-computed tomography (micro-CT), hematoxylin and eosin (H&E) staining, enzyme-linked immunosorbent assay (ELISA), and bacterial quantification of bone tissue indicated that EM+M-LFLIU could also relieve osteomyelitis due to MRSA infection. Our work proffers an original approach to bacterial osteomyelitis treatment that weakens drug-resistant bacteria and suppresses and degrades biofilm formation through SACT, which may provide new prospects for clinical treatment. IMPORTANCE Antibiotic therapy is the first choice for clinical treatment of osteomyelitis, but the formation of bacterial biofilms and the emergence of many drug-resistant strains also create an urgent need to find an alternative treatment to effectively eliminate the infection. Recently, LFLIU has come to be considered a safe and promising method of debridement and antibacterial therapy. In this study, we found that ultrasound and EM have a significant combined antibacterial effect in vivo and in vitro, which may play an antibacterial role by stimulating the production of ROS, destroying the bacterial cell wall, and inhibiting the expression of related genes. Our study expands the body of knowledge on the antibacterial effect of drugs-specifically emodin (EM)-through combined physiotherapy. If successfully integrated into clinical practice, these methods may reduce the burden of high concentrations of drugs needed to treat bacterial biofilms and avoid the growing resistance of bacteria to antibiotics.

Ultrasound-Activatable Phase-Shift Nanoparticle as a Targeting Antibacterial Agent for Efficient Eradication of Pseudomonas aeruginosa Biofilms

Biofilms are physical barriers composed of extracellular polymeric substances (EPS) that enable planktonic bacteria to resist host responses and antibacterial treatments, complicating efforts to clear bacteria such as Pseudomonas aeruginosa (P. aeruginosa) and thereby contributing to persistently chronic infections. As such, it is critical to develop a robust antimicrobial strategy capable of effectively eradicating P. aeruginosa biofilms and to further address aggressive clinical infection. In this study, ultrasound-activatable targeted nanoparticles were designed by using poly(lactic-co-glycolic acid) (PLGA) nanoparticles to encapsulate phase-transformable perfluoropentane (PFP) and the antibiotic meropenem via a double emulsion approach, followed by conjugation with anti-P. aeruginosa antibodies. In this strategy, ultrasound exposure can trigger PFP to produce microbubbles, inducing ultrasonic cavitation effects that can disrupt EPS components and allow nanoparticles to release meropenem to kill P. aeruginosa directly and accelerate the associated wound healing. These nanoparticles eradicated biofilms effectively and cleared bacteria in vitro as well as exhibited potent anti-infective activity in vivo. In summary, this study demonstrates the efficacy of a sonobactericidal strategy as a means of effectively and reliably eliminating biofilms.

Advancements in antimicrobial nanoscale materials and self-assembling systems

Antimicrobial resistance is directly responsible for more deaths per year than either HIV/AIDS or malaria and is predicted to incur a cumulative societal financial burden of at least $100 trillion between 2014 and 2050. Already heralded as one of the greatest threats to human health, the onset of the coronavirus pandemic has accelerated the prevalence of antimicrobial resistant bacterial infections due to factors including increased global antibiotic/antimicrobial use. Thus an urgent need for novel therapeutics to combat what some have termed the 'silent pandemic' is evident. This review acts as a repository of research and an overview of the novel therapeutic strategies being developed to overcome antimicrobial resistance, with a focus on self-assembling systems and nanoscale materials. The fundamental mechanisms of action, as well as the key advantages and disadvantages of each system are discussed, and attention is drawn to key examples within each field. As a result, this review provides a guide to the further design and development of antimicrobial systems, and outlines the interdisciplinary techniques required to translate this fundamental research towards the clinic.

Metal and Metal Oxide Nanomaterials for Fighting Planktonic Bacteria and Biofilms: A Review Emphasizing on Mechanistic Aspects

The misuse and mismanagement of antibiotics have made the treatment of bacterial infections a challenge. This challenge is magnified when bacteria form biofilms, which can increase bacterial resistance up to 1000 times. It is desirable to develop anti-infective materials with antibacterial activity and no resistance to drugs. With the rapid development of nanotechnology, anti-infective strategies based on metal and metal oxide nanomaterials have been widely used in antibacterial and antibiofilm treatments. Here, this review expounds on the state-of-the-art applications of metal and metal oxide nanomaterials in bacterial infective diseases. A specific attention is given to the antibacterial mechanisms of metal and metal oxide nanomaterials, including disrupting cell membranes, damaging proteins, and nucleic acid. Moreover, a practical antibiofilm mechanism employing these metal and metal oxide nanomaterials is also introduced based on the composition of biofilm, including extracellular polymeric substance, quorum sensing, and bacteria. Finally, current challenges and future perspectives of metal and metal oxide nanomaterials in the anti-infective field are presented to facilitate their development and use.

Progress and prospects of nanomaterials against resistant bacteria

Drug-resistant bacterial infections are increasingly heightening, which lead to more severe illness, higher cost of treatment and increased risk of death. Nanomaterials-based therapy, an "outrider", serving as a kind of innovative antimicrobial therapeutics, showing promise in replacing antimicrobial agents and enhancing the activity of antibiotics, generally bases on the various inorganic and/or organic materials. When the size of those materials is below to a certain nano-level and the content of nanomaterials is above a certain amount, they are lethal to the resistant bacteria, which bypass the traditional bacterial resistance mechanisms. This review highlights the effect of nanomaterials in combating extracellular/intracellular bacteria and eradicating biofilms. Based on the studies searched on the Web of Science through relevant keywords, this review article starts with analyzing the current situation, resistance mechanisms, and treatment difficulties of bacteria resistance. Then, the efficacy of nanomaterials against resistant bacteria and their mechanisms (e.g., physical impairment, biofilm lysis, regulating bacterial metabolism, protein and DNA replication as well as enhancing the antibiotics concentration in infected cells) are collected. Lastly, the factors affecting the antibacterial efficacy are argued from the side of nanomatrials and bacterium, which followed by the emerging challenges and recent perspectives of achieving higher targeting released nanomaterials as antibacterial therapeutics.

Cosmetic-Derived Mannosylerythritol Lipid-B-Phospholipid Nanoliposome: An Acid-Stabilized Carrier for Efficient Gastromucosal Delivery of Amoxicillin for In Vivo Treatment of Helicobacter pylori

Helicobacter pylori infection is a leading cause of gastritis and peptic ulcer. Current treatments for H. pylori are limited by the increase in antibiotic-resistant strains and low drug delivery to the infection site, indicating the need for effective delivery systems of antibiotics. Although liposomes are the most successful drug delivery carriers that have already been applied commercially, their acidic stability still stands as a problem. Herein, we developed a novel nanoliposome using cosmetic raw materials of mannosylerythritol lipid-B (MEL-B), soy bean lecithin, and cholesterol, namely, LipoSC-MELB. LipoSC-MELB exhibited enhanced stability under the simulated gastric-acid condition, owing to its strong intermolecular hydrogen-bond interactions caused by the incorporation of MEL-B. Moreover, amoxicillin-loaded LipoSC-MELB (LipoSC-MELB/AMX) had a particle size of approximately 100 nm and exhibited sustained drug release under varying pH conditions (pH 3-7). Besides, LipoSC-MELB/AMX exhibited significantly higher anti-H. pylori and anti-H. pylori biofilm activity as compared with free AMX. Furthermore, LipoSC-MELB was able to carry AMX across the barriers of gastric mucus and H. pylori biofilms. Remarkably, in vivo assays indicated that LipoSC-MELB/AMX was effective in treating H. pylori infection and its associated gastritis and gastric ulcers. Overall, the findings of this study showed that LipoSC-MELB was effective for gastromucosal delivery of amoxicillin to improve its bioavailability for the treatment of H. pylori infection.

Novel nano-encapsulated probiotic agents: Encapsulate materials, delivery, and encapsulation systems

Gut microbes are closely associated with most human health. When ingested orally, probiotics can effectively regulate the composition and quantity of human intestinal microorganisms, which is beneficial to human health. However, probiotics will be affected by the harsh environment of the digestive tract during the in vivo transportation process, and ensuring the viability of probiotics is a great challenge. Probiotic encapsulating technology provides an effective solution to this problem. The introduction of extreme temperatures, large probiotic microcapsule sizes and the difficulty in controlling probiotic microcapsule particle sizes mean that traditional microcapsule encapsulation methods have some limitations. From traditional microcapsule technology to the bulk encapsulation of probiotics with nanofibers and nanoparticles to the recent ability to wear nano "armor" for a single probiotic through biofilm, biological membrane and nanocoating. Emerging probiotic nanoagents provides a new conceptual and development direction for the field of probiotic encapsulation. In this review, we presented the characteristics of encapsulated probiotic carrier materials and digestive tract transport systems, we focused on the encapsulation systems of probiotic nanoagents, we analyzed the shortcomings and advantages of the current agent encapsulation systems, and we stated the developmental direction and challenges for these agents for the future.

Penetration and photodynamic ablation of drug-resistant biofilm by cationic Iron oxide nanoparticles

As we step into the post-antibiotic era, the accelerated emergence of antibiotic-resistant pathogenic bacteria poses an increasingly serious threat to public health. The formation of antibiotic-resistant biofilms further challenges currently available drugs and treatment options, calling for novel strategies for effective ablation of such biofilm with minimal concern on safety and development of resistance. Herein, we report a novel type of photodynamic nanoagent, composed of chlorin e6 (Ce6)-loaded water-soluble chitosan-coated iron oxide nanoparticles (named Ce6@WCS-IONP), for drug-resistant bacteria killing and biofilm eradication. The fabricated Ce6@WCS-IONP has negligible toxicity to mammalian cells and exhibited equivalent singlet oxygen generation capacity to free Ce6; however, its association with methicillin-resistant Staphylococcus aureus (MRSA) was greatly enhanced, as evidenced by flow cytometry analysis and transmission electron microscope. In vitro studies verified that Ce6@WCS-IONP has superior photodynamic bactericidal effect against planktonic MRSA. Furthermore, with the aid of the cationic nature and small size, Ce6@WCS-IONP could effectively penetrate into MRSA biofilm, revealed by 3D fluorescence imaging. Both biomass analysis and viable bacteria counting demonstrated that Ce6@WCS-IONP showed potent biofilm ablation efficacy, averagely 7.1 log unit lower than that in free Ce6 group upon identical light irradiation. In addition, local treatment of MRSA-infected mice with Ce6@WCS-IONP plus light irradiation resulted in significant antibacterial and wound healing effect, accompanied by good biocompatibility in vivo. Collectively, photosensitizer-loaded cationic IONP with effective biofilm penetration and photodynamic eradication potential might be a promising nano platform in fighting against antibiotic-resistant microbial pathogen and biofilm.

Membrane-cloaked polydopamine modified mesoporous silica nanoparticles for cancer therapy

To improve the shortcomings of narrow therapeutic range and low bioavailability of traditional preparations, a composite drug carrier that combines the advantages of biological carriers and synthetic carriers was prepared in this project. The biomimetic nano-delivery system outer membrane vesicles-polydopamine-mesoporous silica nanoparticle (OMVs-PDA-MSN-DOX) for oral administration is composed of OMVs ofEscherichia colias shell and doxorubicin-loaded MSN modified by PDA as core. Several characterization techniques thoroughly examined the nano-drug delivery system to confirm its surface morphology and chemical property. OMVs-PDA-MSN-DOX with a particle size of 150 nm showed significant cell selectivity and safety. We demonstrated that OMVs are capable of protecting pH-sensitive nanostructure from the oral route of administration in the short term. Importantly, OMVs-PDA-MSN-DOX could facilitate intestinal adhesion and improve DOX bioavailability. Overall, the OMVs-cloaked nanocarrier provides an efficient delivery platform for the oral targeting treatment of cancer with pH-sensitive nano-formulations.

Advances in Nanostructures for Antimicrobial Therapy

Microbial infections caused by a variety of drug-resistant microorganisms are more common, but there are fewer and fewer approved new antimicrobial chemotherapeutics for systemic administration capable of acting against these resistant infectious pathogens. Formulation innovations of existing drugs are gaining prominence, while the application of nanotechnologies is a useful alternative for improving/increasing the effect of existing antimicrobial drugs. Nanomaterials represent one of the possible strategies to address this unfortunate situation. This review aims to summarize the most current results of nanoformulations of antibiotics and antibacterial active nanomaterials. Nanoformulations of antimicrobial peptides, synergistic combinations of antimicrobial-active agents with nitric oxide donors or combinations of small organic molecules or polymers with metals, metal oxides or metalloids are discussed as well. The mechanisms of actions of selected nanoformulations, including systems with magnetic, photothermal or photodynamic effects, are briefly described.