Challenges and solutions in polymer drug delivery for bacterial biofilm treatment: A tissue-by-tissue account

Devices to overcome the buccal mucosal barrier to administer therapeutic peptides

Peptide therapeutics are important in healthcare owing to their high target specificity, therapeutic efficacy, and relatively low side effect profile. Injections of these agents have improved thetreatment of chronic diseases including autoimmune, metabolic disorders, and cancer. However, their administration via injections can prove a barrier to patient acceptability of treatments. While oral delivery of these molecules is preferable, oral peptide formulations are associated with limited bioavailability due to degradation in the intestine and low epithelial permeability. Buccal administration of peptides is a potential alternative to injections and oral formulations. Similar to the oral route, the buccal route can promote better patient adherence to dosing regimens, along with the added advantages of not requiring restriction on food or drink consumption before and after administration, as well as avoidance of the liver first-pass metabolism. However, like oral, effective buccal absorption of peptides is still challenging due to the high epithelial permeability barrier. We present a multidisciplinary approach to understanding the buccal physiological barrier to macromolecule permeation and discuss how engineered devices may overcome it. Selected examples of buccal devices can facilitate fast and efficient macromolecule absorption through multiple mechanisms including physical disruption of epithelia, convection-based mass transfer, and a combination of physicochemical strategies. Importantly, minimally invasive devices can be self-applied and are associated with the maintenance of the barrier after exposure. We analysed the critical attributes that are required forthe clinical translation of buccal peptide administration devices. These include performance-driven device development, manufacturing features, patient acceptability, and commercial viability.

Engineered Bdellovibrio bacteriovorus enhances antibiotic penetration and biofilm eradication

Biofilms increase bacterial resistance to antibiotics, as conventional antibiotic doses are often ineffective at penetrating the biofilm matrix to eliminate bacteria. Recent research has shown that the Gram-negative predator bacterium Bdellovibrio bacteriovorus can penetrate Gram-positive bacterial biofilms during its predation phase and benefit from them without direct predation. Here, based on the penetration ability of B. bacteriovorus, we constructed antibiotic-loaded liposome-engineered B. bacteriovorus as a drug delivery strategy for biofilm-related diseases. As a "living antibiotic," B. bacteriovorus can prey on Gram-negative bacteria, penetrate biofilms, and disrupt their dense structure. During this process, the rapid movement of B. bacteriovorus enhances the delivery of antibiotic-loaded liposomes into the biofilm, promoting efficient antibiotic release and improving biofilm eradication. Our findings demonstrate that this engineered living antibiotic strategy significantly improves the control and removal of bacterial biofilms, accelerates the elimination of dental plaque, promotes wound healing, and holds promise as a novel platform for treating biofilm-related infections.

Versatile nanomaterials used in combatting biofilm infections

Microbial infections are a pressing global health issue, exacerbated by the rise of antibiotic-resistant bacteria due to widespread antibiotic overuse. This resistance diminishes the effectiveness of current treatments, intensifying the need for new antimicrobial agents and innovative drug delivery strategies. Nanotechnology presents promising solutions, leveraging the unique properties of nanomaterials such as tunable optical and electronic characteristics, nanoscale size, and high surface-to-volume ratios. These features enhance their effectiveness as innovative antimicrobial agents and versatile drug delivery systems. This minireview classifies antimicrobial nanomaterials into four categories based on their mechanisms of action: thermal generation, reactive oxygen species generation, gas generation, and nanocarrier systems such as liposomes, polymersomes, and metal-organic frameworks. Uniquely, this review integrates a comparative analysis of these mechanisms, highlighting their relative advantages, limitations, and applications across diverse microbial targets. Additionally, it identifies emerging trends in the field, providing a forward-looking perspective on how recent advancements in nanotechnology can be leveraged to address unmet clinical needs. Finally, this article discusses future directions and emerging opportunities in antimicrobial nanotechnology.

The antibacterial capabilities of alginate encapsulated lemon essential oil nanocapsules against multi-drug-resistant Acinetobacter baumannii

Controlling microbial pollutants is a significant public health concern as they cause several chronic microbial infections and illnesses. In recent years, essential oils (EOs) have become intriguing alternatives for synthetic antimicrobials due to their biodegradability, natural source extraction, and strong antibacterial properties. The bactericidal properties of alginate containing lemon essential oil were examined in this investigation. Following the screening of the MDR strains, the morphological properties of the produced nanoparticles were examined using SEM, DLS, and FTIR. Additionally, the durability, effectiveness, and drug dispersion of encapsulation were assessed. Bacterial virulence factor gene amounts were measured using Q-real-time PCR. Concurrently, the cytotoxic effect of the nanomaterials was evaluated using MTT techniques. Nanoparticles of lemon essential oil encapsulated in alginate, measuring 500 ± 19.32 nm in size, with entrapment efficiency of 77.73 ± 1.78% and were stable for 60 days at 4 °C. Alginate encapsulated with lemon essential oil nanoparticles (ALN) exhibited potent antibacterial qualities, according to the biological investigation. Their ability to decrease the transcription of bacterial virulence genes at least statistically significantly (P ≤ 0.05) served as evidence for this. Between 1.56 and 100 µg/mL (P ≤ 0.01), ALN exhibited lower cytotoxicity against CCD841CoN than free lemon essential oil. The findings show that ALN nanoparticles have the potential to be a breakthrough in the fight against highly resistant illnesses. ALN nanoparticles' potent antibacterial efficacy against MDR strains of Acinetobacter baumannii may inspire new directions in antibacterial research.

Limonene encapsulated alginate/collagen as antibiofilm drug against Acinetobacter baumannii

This work examined the antibacterial and antibiofilm properties of alginate/collagen nanoparticles containing limonene. The multi-drug resistant (MDR) strains were screened, and the morphological features of the produced nanoparticles were determined utilizing SEM, DLS, and FTIR. Additionally, the encapsulation effectiveness, stability, and drug release were assessed. The levels of OmpA and Bap biofilm genes were assessed using qRT-PCR. At the same time, the antibacterial and cytotoxic activities of the nanoparticles were evaluated using well diffusion and MTT techniques, respectively. LAC nanoparticles measuring 300 ± 9.6 nm in size, 83.64 ± 0.19% encapsulation efficiency, and 60-day stability at 4 °C were synthesized. The biological investigation demonstrated that LAC nanoparticles had potent antibacterial capabilities. This was shown by their ability to significantly decrease the transcription of OmpA and Bap biofilm genes at a statistically significant level of p ≤ 0.05. The nanoparticles exhibited reduced antibiotic resistance compared to free limonene and alginate/collagen. Compared to limonene, LAC nanoparticles exhibited negligible cytotoxicity against HEK-293 at doses ranging from 1.56 to 100 µg/mL (p ≤ 0.01). The findings underscore the potential of LAC nanoparticles as a breakthrough in the fight against highly resistant pathogens. The potent antibacterial effects of LAC nanoparticles versus Acinetobacter baumannii (A. baumannii) MDR strains, considered highly resistant pathogens of significant concern, could inspire new strategies in antibacterial research.

Mathematical modeling of vancomycin release from Poly-L-Lactic Acid-Coated implants

This study aimed to develop a mathematical model to predict the release profile and antibacterial efficacy of a vancomycin delivery system integrated with poly(L-lactic acid)-coated bone implants specifically designed for bone plates. Using Fickian diffusion principles within an ANSYS-CFX computational fluid dynamic model, we validated the model against our in vitro vancomycin release and agar diffusion studies, as well as previously published in vivo data, confirming the reliability of the model. The model predictions demonstrated the effectiveness of the system in inhibiting bacterial growth in surrounding tissue with no observed toxicity, with a peak vancomycin concentration of 0.95 mg/ml at 6 hours, followed by a decrease to levels that remained effective for antibacterial activity. Furthermore, a sensitivity analysis revealed that the model is particularly sensitive to the half-life of vancomycin, with a maximum sensitivity index of 0.8, indicating its greater impact on the prediction accuracy than the diffusion coefficient, which has a maximum sensitivity index of 0.5. Therefore, precise input of vancomycin's half-life is critical for accurate predictions. These findings offer substantial support for the efficacy of the local delivery system as a promising therapeutic approach against implant-associated infections.

Engineered macrophage-derived exosomes via click chemistry for the treatment of osteomyelitis

Osteomyelitis is a severe bone condition caused by bacterial infection that can lead to lifelong disabilities or fatal sepsis. Given that the infection is persistent and penetrates deep into the bone tissue, targeting and rapidly treating osteomyelitis remain a significant challenge. Herein, a triblock targeting peptide featuring ROS-cleavable linkage/antibacterial/bone-targeting unit was grafted onto the macrophage-derived exosomes (RAB-EXO). In vitro, the effective eradication of osteomyelitis pathogens MRSA/E. coli and induction of M2 macrophage differentiation were triggered by RAB-EXO. In vivo, after the intravenous administration of RAB-EXO, it can target the bone tissue and release antimicrobial peptides in the high ROS environment of osteomyelitis. The released antimicrobial peptides markedly inhibit bacterial growth at the infection sites. Moreover, M2 differentiation of the bone tissue macrophages are facilitated by EXO, thereby decreasing the inflammatory factors and achieving the anti-inflammatory effect. Finally, the complete healing of osteomyelitis without adverse effects associated with traditional treatments is achieved within 28 days in rat models. Our findings confirm that RAB-EXO, as a targeted treatment for osteomyelitis, offers promising directions for addressing other bacterial infection diseases, such as periodontitis and rheumatoid arthritis, through similar mechanisms.

Stimuli-Responsive Release-Active Dressing: A Promising Solution for Eradicating Biofilm-Mediated Wound Infections

Biofilm-mediated wound infections pose a significant challenge due to the limitations of conventional antibiotics, which often exhibit narrow-spectrum activity, fail to eliminate recurrent bacterial contamination, and are unable to penetrate the biofilm matrix. While the search for alternatives has explored the use of metal nanoparticles and synthetic biocides, these solutions often suffer from unintended toxicity to surrounding tissues and lack controlled administration and release. In this study, we engineered a pH-responsive release-active dressing film based on carboxymethyl cellulose, incorporating a synthetic antibacterial molecule (SAM-17). The dressing film exhibited optimal mechanical stability for easy application and demonstrated excellent fluid absorption properties, allowing for prolonged moisturization at the site of injury. The film exhibited pH-dependent release of cargo, with 78% release within 24 h at acidic pH, enabling targeted antibacterial drug delivery within the wound microenvironment. Furthermore, the release-active film effectively eliminated repeated challenges of bacterial contamination. Remarkably, the film demonstrated a minimal toxicity profile in both in vitro and in vivo models. The film eliminated preformed bacterial biofilms, achieving a reduction of 2.5 log against methicillin-resistant Staphylococcus aureus (MRSA) and 4.1 log against vancomycin-resistant S. aureus (VRSA). In a biofilm-mediated MRSA wound infection model, this release-active film eradicated the biofilm-embedded bacteria by over 99%, resulting in accelerated wound healing. These findings highlight the potential of this film as an effective candidate for tackling biofilm-associated wound infections.

The Efficacy of Local Antibiotic Delivery Systems Therapy in the Management of Diabetic Foot Osteomyelitis: A Systematic Review and Meta-Analysis

PURPOSE

We aim to evaluate the efficacy of local antibiotic delivery systems in patients with diabetic foot osteomyelitis (DFO).

METHODS

The Web of Science, PubMed, and Embase databases were searched for relevant publications until March 2024. All studies evaluating the efficacy of local antibiotic delivery systems in patients with DFO were included. We calculated pooled risk ratio (RR) with 95% CIs for binary outcomes and mean difference (MD) for continuous outcomes. The Cochrane's risk of bias tool and methodological index for non-randomized studies (MINORS) assessment were used to evaluate the quality of studies.

RESULTS

A total of 9 studies with 491 patients were included in this analysis. The overall healing rate in antibiotic group was 0.85 (95% CI: 0.67, 0.97). Healing rates were significantly higher in the antibiotic group compared to the control group (RR: 1.18, 95% CI: 1.01, 1.38). Furthermore, recurrence rates and amputation rates have no significantly difference between the antibiotic group and the control group (RR: 0.30, 95% CI: 0.04, 2.12 and RR: 0.22, 95% CI:0.03, 1.91), along with no significantly difference in healing time and hospital stays(MD: -7.87, 95% CI: -20.81, 5.07 and MD:-2.33, 95% CI:-5.17, 0.50). No obvious publication bias was observed in the funnel plot (Egger's test, P = .99).

CONCLUSIONS

Our meta-analysis found that diabetic foot osteomyelitis patients treated with local antibiotic delivery systems had better healing rates than the control group. However, no significant differences were found in healing time, recurrence, hospital stays, or amputation rates. Larger randomized controlled trials are necessary in the future.

Photocrosslinked gelatin/chondroitin sulfate/chitosan-based composites with tunable multifunctionality for bone tissue regeneration

Novel hydrogel-based multifunctional systems prepared utilizing photocrosslinking and freeze-drying processes (PhotoCross/Freeze-dried) dedicated for bone tissue regeneration are presented. Fabricated materials, composed of methacrylated gelatin, chitosan, and chondroitin sulfate, possess interesting features including bioactivity, biocompatibility, as well as antibacterial activity. Importantly, their degradation and swellability might be easily tuned by playing with the biopolymeric content in the photocrosllinked systems. To broaden the potential application and deliver the therapeutic features, mesoporous silica particles functionalized with methacrylate moieties decorated with hydroxyapatite and loaded with the antiosteoporotic drug, alendronate, (MSP-MA-HAp-ALN) were dispersed within the biopolymeric sol and photocrosslinked. It was demonstrated that the obtained composites are characterized by a significantly extended degradation time, ensuring optimal conditions for balancing hybrids removal with the deposition of fresh bone. We have shown that attachment of MSP-MA-HAp-ALN to the polymeric matrix minimizes the initial burst effect and provides a prolonged release of ALN (up to 22 days). Moreover, the biological evaluation in vitro suggested the capability of the resulted systems to promote bone remodeling. Developed materials might potentially serve as scaffolds that after implantation will fill up bone defects of various origin (osteoporosis, tumour resection, accidents) providing the favourable conditions for bone regeneration and supporting the infections' treatment.

Triblock copolymer micelles enhance solubility, permeability and activity of a quorum sensing inhibitor against Pseudomonas aeruginosa biofilms

Antimicrobial resistance is a threat to public health for which new treatments are urgently required. The capability of bacteria to form biofilms is of particular concern as it enables high bacterial tolerance to conventional therapies by reducing drug diffusion through the dense, exopolymeric biofilm matrix and the upregulation of antimicrobial resistance machinery. Quorum sensing (QS), a process where bacteria use diffusible chemical signals to coordinate group behaviour, has been shown to be closely interconnected with biofilm formation and bacterial virulence in many top priority pathogens including Pseudomonas aeruginosa. Inhibition of QS pathways therefore pose an attractive target for new therapeutics. We have recently reported a new series of pqs quorum sensing inhibitors (QSIs) that serve as potentiators for antibiotics in P. aeruginosa infections. The impact on biofilms of some reported QSIs was however hindered by their poor penetration through the bacterial biofilm, limiting the potential for clinical translation. In this study we developed a series of poly(β-amino ester) (PBAE) triblock copolymers and evaluated their ability to form micelles, encapsulate a QSI and enhance subsequent delivery to P. aeruginosa biofilms. We observed that the QSI could be released from polymer micelles, perturbing the pqs pathway in planktonic P. aeruginosa. In addition, one of the prepared polymer variants increased the QSIs efficacy, leading to an enhanced potentiation of ciprofloxacin (CIP) action and therefore improved reduction in biofilm viability, compared to the non-encapsulated QSI. Thus, we demonstrate QSI encapsulation in polymeric particles can enhance its efficacy through improved biofilm penetration.

Emerging polymeric materials for treatment of oral diseases: design strategy towards a unique oral environment

Oral diseases are prevalent but challenging diseases owing to the highly movable and wet, microbial and inflammatory environment. Polymeric materials are regarded as one of the most promising biomaterials due to their good compatibility, facile preparation, and flexible design to obtain multifunctionality. Therefore, a variety of strategies have been employed to develop materials with improved therapeutic efficacy by overcoming physicobiological barriers in oral diseases. In this review, we summarize the design strategies of polymeric biomaterials for the treatment of oral diseases. First, we present the unique oral environment including highly movable and wet, microbial and inflammatory environment, which hinders the effective treatment of oral diseases. Second, a series of strategies for designing polymeric materials towards such a unique oral environment are highlighted. For example, multifunctional polymeric materials are armed with wet-adhesive, antimicrobial, and anti-inflammatory functions through advanced chemistry and nanotechnology to effectively treat oral diseases. These are achieved by designing wet-adhesive polymers modified with hydroxy, amine, quinone, and aldehyde groups to provide strong wet-adhesion through hydrogen and covalent bonding, and electrostatic and hydrophobic interactions, by developing antimicrobial polymers including cationic polymers, antimicrobial peptides, and antibiotic-conjugated polymers, and by synthesizing anti-inflammatory polymers with phenolic hydroxy and cysteine groups that function as immunomodulators and electron donors to reactive oxygen species to reduce inflammation. Third, various delivery systems with strong wet-adhesion and enhanced mucosa and biofilm penetration capabilities, such as nanoparticles, hydrogels, patches, and microneedles, are constructed for delivery of antibiotics, immunomodulators, and antioxidants to achieve therapeutic efficacy. Finally, we provide insights into challenges and future development of polymeric materials for oral diseases with promise for clinical translation.

AMP-Coated TiO2 Doped ZnO Nanomaterials Enhanced Antimicrobial Activity and Efficacy in Otitis Media Treatment by Elevating Hydroxyl Radical Levels

Background

In the past decades, antimicrobial resistance (AMR) has been a major threat to global public health. Long-term, chronic otitis media is becoming more challenging to treat, thus the novel antibiotic alternative agents are much needed.

Methods

ZnO@TiO2@AMP (ATZ NPs) were synthesized through a solvothermal method and subjected to comprehensive characterization. The in vitro and in vivo antibacterial effect and biocompatibility of ATZ NPs were evaluated. For the antibacterial mechanism exploration, we utilized the Electron Paramagnetic Resonance (EPR) Spectrometer to detect and analyze the hydroxyl radicals produced by ATZ NPs.

Results

ATZ NPs exhibited a spherical structure of 99.85 nm, the drug-loading rate for ZnO was 20.73%, and AMP within ATZ NPs was 41.86%. Notably, the Minimum Inhibitory Concentration (MIC) value of ATZ NPs against Staphylococcus aureus (S. aureus), methicillin-resistant Staphylococcus aureus (MRSA), and Streptococcus pneumoniae (S. pneumoniae) were 10 μg/mL, and Minimum Bactericidal Concentration (MBC) value of ATZ NPs against S. aureus, and S. pneumoniae were 50 μg/mL. In comparison to the model group, the treatment of otitis media with ATZ NPs significantly reduces inflammatory exudation in the middle ear cavity, with no observable damage to the tympanic membrane. Both in vivo and in vitro toxicity tests indicating the good biocompatibility of ATZ NPs. Moreover, EPR spectroscopy results highlighted the superior ability of ATZ NPs to generate hydroxyl radicals (·OH) compared to ZnO NPs.

Conclusion

ATZ NPs exhibited remarkable antibacterial properties both in vivo and in vitro. This innovative application of advanced ATZ NPs, bringing great promise for the treatment of otitis media.

Ciprofloxacin Poly(β-amino ester) Conjugates Enhance Antibiofilm Activity and Slow the Development of Resistance

To tackle the emerging antibiotic resistance crisis, novel antimicrobial approaches are urgently needed. Bacterial biofilms are a particular concern in this context as they are responsible for over 80% of bacterial infections and are inherently more recalcitrant toward antimicrobial treatments. The high tolerance of biofilms to conventional antibiotics has been attributed to several factors, including reduced drug diffusion through the dense exopolymeric matrix and the upregulation of antimicrobial resistance machinery with successful biofilm eradication requiring prolonged high doses of multidrug treatments. A promising approach to tackle bacterial infections involves the use of polymer drug conjugates, shown to improve upon free drug toxicity and bioavailability, enhance drug penetration through the thick biofilm matrix, and evade common resistance mechanisms. In the following study, we conjugated the antibiotic ciprofloxacin (CIP) to a small library of biodegradable and biocompatible poly(β-amino ester) (PBAE) polymers with varying central amine functionality. The suitability of the polymers as antibiotic conjugates was then verified in a series of assays including testing of efficacy and resistance response in planktonic Gram-positive and Gram-negative bacteria and the reduction of viability in mono- and multispecies biofilm models. The most active polymer within the prepared PBAE-CIP library was shown to achieve an over 2-fold increase in the reduction of biofilm viability in a Pseudomonas aeruginosa monospecies biofilm and superior elimination of all the species present within the multispecies biofilm model. Hence, we demonstrate that CIP conjugation to PBAEs can be employed to achieve improved antibiotic efficacy against clinically relevant biofilm models.

Understanding the intricacies of microbial biofilm formation and its endurance in chronic infections: a key to advancing biofilm-targeted therapeutic strategies

Bacterial biofilms can adhere to various surfaces in the environment with human beings being no exception. Enclosed in a self-secreted matrix which contains extracellular polymeric substances, biofilms are intricate communities of bacteria that play a significant role across various sectors and raise concerns for public health, medicine and industries. These complex structures allow free-floating planktonic cells to adopt multicellular mode of growth which leads to persistent infections. This is of great concern as biofilms can withstand external attacks which include antibiotics and immune responses. A more comprehensive and innovative approach to therapy is needed in view of the increasing issue of bacterial resistance brought on by the overuse of conventional antimicrobial medications. Thus, to oppose the challenges posed by biofilm-related infections, innovative therapeutic strategies are being explored which include targeting extracellular polymeric substances, quorum sensing, and persister cells. Biofilm-responsive nanoparticles show promising results by improving drug delivery and reducing the side effects. This review comprehensively examines the factors influencing biofilm formation, host immune defence mechanisms, infections caused by biofilms, diagnostic approaches, and biofilm-targeted therapies.

Curcumin-loaded chitosan-based hydrogels accelerating S. aureus-infected wound healing

The damaged skin for some reasons is vulnerable to invasion by bacteria and other harmful microorganisms, leading to delay of the wound healing. In order to promote the infected wound healing, curcumin was loaded with chitosan-based hydrogel was formed through phenylborate ester bonding and its properties and effects on the S. aureus-infected wound healing was tested. It was found the hydrogel showed good antioxidation on the intracellular reactive oxygen species, inhibition on the growth of S. aureus, and acceleration the infected skin healing. The ablity of hydrogel due to its regulating inflammation, promoting angiogenesis and collagen synthesis in the wound site. This research work suggested that the developed multifunctional hydrogel might be a beneficial treatment for the infected wound healing.

A Mini-review on New Developments in Nanocarriers and Polymers for Ophthalmic Drug Delivery Strategies

The eye is an important and vital organ of the human body consisting of two segments - anterior and posterior segments and these segments are associated with many diseases. This review elaborates upon the various eye-related diseases with their medications and carriers used to deliver them. Delivery strategies include drugs encapsulated into liposomes, polymeric micelles of drugs, solid lipid nanoparticles, nanostructured lipid carriers, nano emulsions, and Nanosuspension used to improve penetrating properties, bioavailability, and residence time of the drugs as examples available in the literature. With regard to this, different forms of ocular drug delivery are classified and elaborated. Additionally, the possibility of addressing the physical and chemical complexities of ocular diseases and how they could be overcome with environmentally stable nanoformulations are briefly discussed. Enhanced drug delivery efficiency with various novel pharmaceuticals along with enhanced uptake by different routes/modes of drug administration. Current advancements in drug carrier systems, i.e., nanocarriers, have shown promise for improving the retention time, drug permeation and prolonging the duration of release of the drug in the ocular site. Bio-degradable polymers investigated for the preparation of nanocarriers for the entrapment of drugs and to enhance the efficacy through improved adherence of tissue in the eye, sustained release measures, enhanced bioavailability, lower toxicity, and targeted delivery is applicable. This review covers the introduction of various nanocarriers and polymers for ocular drug delivery with the purpose of enhancing the absorption, retention and bioavailability of medications in the eye.

Deep-penetration functionalized cuttlefish ink nanoparticles for combating wound infections with synergetic photothermal-immunologic therapy

The challenge of wound infections post-surgery and open trauma caused by multidrug-resistant bacteria poses a constant threat to clinical treatment. As a promising antimicrobial treatment, photothermal therapy can effectively resolve the problem of drug resistance in conventional antibiotic antimicrobial therapy. Here, we report a deep-penetration functionalized cuttlefish ink nanoparticle (CINP) for photothermal and immunological therapy of wound infections. CINP is decorated with zwitterionic polymer (ZP, namely sulfobetaine methacrylate-methacrylate copolymer) to form CINP@ZP nanoparticles. Natural CINP is found to not only exhibit photothermal destruction of methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli (E. coli), but also trigger macrophages-related innate immunity and enhance their antibacterial functions. The ZP coating on the surface of CINP enables nanoparticles to penetrate into deeply infected wound environment. In addition, CINP@ZP is further integrated into the thermosensitive Pluronic F127 gel (CINP@ZP-F127). After in situ spraying gel, CINP@ZP-F127 is also documented notable antibacterial effects in mice wound models infected with MRSA and E. coli. Collectively, this approach combining of photothermal therapy with immunotherapy can promote delivery efficiency of nanoparticles to the deep foci of infective wounds, and effectively eliminate wound infections.

Rational Designs of Biomaterials for Combating Oral Biofilm Infections

Oral biofilms, which are also known as dental plaque, are the culprit of a wide range of oral diseases and systemic diseases, thus contributing to serious health risks. The manner of how to achieve good control of oral biofilms has been an increasing public concern. Novel antimicrobial biomaterials with highly controllable fabrication and functionalization have been proven to be promising candidates. However, previous reviews have generally emphasized the physicochemical properties, action mode, and application effectiveness of those biomaterials, whereas insufficient attention has been given to the design rationales tailored to different infection types and application scenarios. To offer guidance for better diversification and functionalization of anti-oral-biofilm biomaterials, this review details the up-to-date design rationales in three aspects: the core strategies in combating oral biofilm, as well as the biomaterials with advanced antibiofilm capacity and multiple functions based on the improvement or combination of the abovementioned antimicrobial strategies. Thereafter, insights on the existing challenges and future improvement of biomaterial-assisted oral biofilm treatments are proposed, hoping to provide a theoretical basis and reference for the subsequent design and application of antibiofilm biomaterials.

Advances in Nanotechnology for Biofilm Inhibition

Biofilm-associated infections have emerged as a significant public health challenge due to their persistent nature and increased resistance to conventional treatment methods. The indiscriminate usage of antibiotics has made us susceptible to a range of multidrug-resistant pathogens. These pathogens show reduced susceptibility to antibiotics and increased intracellular survival. However, current methods for treating biofilms, such as smart materials and targeted drug delivery systems, have not been found effective in preventing biofilm formation. To address this challenge, nanotechnology has provided innovative solutions for preventing and treating biofilm formation by clinically relevant pathogens. Recent advances in nanotechnological strategies, including metallic nanoparticles, functionalized metallic nanoparticles, dendrimers, polymeric nanoparticles, cyclodextrin-based delivery, solid lipid nanoparticles, polymer drug conjugates, and liposomes, may provide valuable technological solutions against infectious diseases. Therefore, it is imperative to conduct a comprehensive review to summarize the recent advancements and limitations of advanced nanotechnologies. The present Review encompasses a summary of infectious agents, the mechanisms that lead to biofilm formation, and the impact of pathogens on human health. In a nutshell, this Review offers a comprehensive survey of the advanced nanotechnological solutions for managing infections. A detailed presentation has been made as to how these strategies may improve biofilm control and prevent infections. The key objective of this Review is to summarize the mechanisms, applications, and prospects of advanced nanotechnologies to provide a better understanding of their impact on biofilm formation by clinically relevant pathogens.

Design of Quorum Sensing Inhibitor-Polymer Conjugates to Penetrate Pseudomonas aeruginosa Biofilms

Antimicrobial resistance (AMR) is a global threat to public health with a forecast of a negative financial impact of one trillion dollars per annum, hence novel therapeutics are urgently needed. The resistance of many bacteria against current drugs is further augmented by the ability of these microbes to form biofilms where cells are encased in a slimy extracellular matrix and either adhered to a surface or forming cell aggregates. Biofilms form physiochemical barriers against the penetration of treatments such as small molecule antibacterials, rendering most treatments ineffective. Pseudomonas aeruginosa, a priority pathogen of immediate concern, controls biofilm formation through multiple layers of gene regulation pathways including quorum sensing (QS), a cell-to-cell signaling system. We have recently reported a series of inhibitors of the PqsR QS regulator from this organism that can potentiate the action of antibiotics. However, these QS inhibitors (QSIs) have shown modest effects on biofilms in contrast with planktonic cultures due to poor penetration through the biofilm matrix. To enhance the delivery of the inhibitors, a small library of polymers was designed as carriers of a specific QSI, with variations in the side chains to introduce either positively charged or neutral moieties to aid penetration into and through the P. aeruginosa biofilm. The synthesized polymers were evaluated in a series of assays to establish their effects on the inhibition of the Pqs QS system in P. aeruginosa, the levels of inhibitor release from polymers, and their impact on biofilm formation. A selected cationic polymer-QSI conjugate was found to penetrate effectively through biofilm layers and to release the QSI. When used in combination with ciprofloxacin, it enhanced the biofilm antimicrobial activity of this antibiotic compared to free QSI and ciprofloxacin under the same conditions.

Targeted Delivery of Zinc Ion Derived by Pseudopolyrotaxane Gel Polymer Electrolyte for Long-Life Zn Anode

Aqueous zinc ion battery is a potential alternative for a stationary energy storage system owing to the inherent properties of the Zn anode. However, the Zn anode suffers from serious Zn dendrite due to the uneven Zn plating. Thus, inspired by the nano-drug delivery to the target site of the tumor cell, it would be a promising strategy to introduce targeted delivery of zinc ion in the electrolyte for even Zn plating. Passive targeted transport plays an important role in nano-drug delivery, which presents the nano-drug would be released by the nano-drug carrier based on polymer to the particular target site. As a proof-of-concept, a pseudopolyrotaxane conducting the nano-drug carrier applied in targeted cancer therapy is employed as the gel polymer electrolyte (GPE) for long-life Zn anodes. The pseudopolyrotaxane is formed by the self-assembling of α-cyclodextrin (CD) and poly(ethylene oxide), where the zinc ion can be absorbed and delivered to the target site of the Zn anode benefiting from the hydrogen-bond. Impressively, even Zn plating can be induced by the hydroxyl groups of CD to inhibit Zn dendrite. Moreover, the hydrogen evolution reaction is suppressed by the GPE. Less produced H₂ is detected in the GPE, which is demonstrated by the online mass spectrometry. Thus, the Zn||Zn symmetrical cell based on the GPE exhibits a cycling life of 1370 h. Compared to the one based on aqueous electrolyte, Zn||MnO₂ battery based on the GPE shows a higher capacity retention. This work is expected to avail the development of the aqueous zinc ion battery.

Structurally diverse G-quadruplexes as the noncanonical nucleic acid drug target for live cell imaging and antibacterial study

The formation of G-quadruplex structures (G4s) in vitro from guanine (G)-rich nucleic acid sequences of DNA and RNA stabilized with monovalent cations, typically K⁺ and Na⁺, under physiological conditions, has been verified experimentally and some of them have high-resolution NMR or X-ray crystal structures; however, the biofunction of these special noncanonical secondary structures of nucleic acids has not been fully understood and their existence in vivo is still controversial at present. It is generally believed that the folding and unfolding of G4s in vivo is a transient process. Accumulating evidence has shown that G4s may play a role in the regulation of certain important cellular functions including telomere maintenance, replication, transcription and translation. Therefore, both DNA and RNA G4s of human cancer hallmark genes are recognized as the potential anticancer drug target for the investigation in cancer biology, chemical biology and drug discovery. The relationship between the sequence, structure and stability of G4s, the interaction of G4s with small molecules, and insights into the rational design of G4-selective binding ligands have been intensively studied over the decade. At present, some G4-ligands have achieved a new milestone and successfully entered the human clinical trials for anticancer therapy. Over the past few decades, numerous efforts have been devoted to anticancer therapy; however, G4s for molecular recognition and live cell imaging and for application as antibacterial agents and antibiofilms against antibiotic resistance have been obviously underexplored. The recent advances in G4-ligands in these areas are thus selected and discussed concentratedly in this article in order to shed light on the emerging role of G4s in chemical biology and therapeutic prospects against bacterial infections. In addition, the recently published molecular scaffolds for designing small ligands selectively targeting G4s in live cell imaging, bacterial biofilm imaging, and antibacterial studies are discussed. Furthermore, a number of underexplored G4-targets from the cytoplasmic membrane-associated DNA, the conserved promoter region of K. pneumoniae genomes, the RNA G4-sites in the transcriptome of E. coli and P. aeruginosa, and the mRNA G4-sites in the sequence for coding the vital bacterial FtsZ protein are highlighted to further explore in G4-drug development against human diseases.

Engineered organic nanoparticles to combat biofilms

Biofilms are colonies of microorganisms that are embedded in autocrine extracellular polymeric substances (EPS), imparting antibiotic resistance and recalcitrant bacterial infection. Nanoparticles (NPs) can enhance the biofilm inhibition and eradication of delivered antibiotics. This is mainly because of enhanced EPS penetration and a high local drug concentration. As we discuss here, novel strategies are being developed to further enhance the antibiofilm capacity of NPs, including size optimization, surface modification, stimuli-triggered release, and combined strategies. Thus, NPs represent an effective and promising approach to combat biofilms.

Self-Driven Electron Transfer Biomimetic Enzymatic Catalysis of Bismuth-Doped PCN-222 MOF for Rapid Therapy of Bacteria-Infected Wounds

In this work, a biomimetic nanozyme catalyst with rapid and efficient self-bacteria-killing and wound-healing performances was synthesized. Through an in situ reduction reaction, a PCN-222 metal organic framework (MOF) was doped with bismuth nanoparticles (Bi NPs) to form Bi-PCN-222, an interfacial Schottky heterojunction biomimetic nanozyme catalyst, which can kill 99.9% of Staphylococcus aureus (S. aureus). The underlying mechanism was that Bi NP doping can endow Bi-PCN-222 MOF with self-driven charge transfer through the Schottky interface and the capability of oxidase-like and peroxidase-like activity, because a large number of free electrons can be captured by surrounding oxygen species to produce radical oxygen species (ROS). Furthermore, once bacteria contact Bi-PCN-222 in a physiological environment, its appropriate redox potential can trigger electron transfer through the electron transport pathway in bacterial membranes and then the interior of the bacteria, which disturbs the bacterial respiration process and subsequent metabolism. Additionally, Bi-PCN-222 can also accelerate tissue regeneration by upregulating fibroblast proliferation and angiogenesis genes (bFGF, VEGF, and HIF-1α), thereby promoting wound healing. This biomimetic enzyme-catalyzed strategy will bring enlightenment to the design of self-bacterial agents for efficient disinfection and tissue reconstruction simultaneously.

Miniaturized Polymeric Systems for the Intravaginal Gene Therapies: Recent Update on Unconventional Delivery

The prevalence of vaginal infection is increasing among women, especially at reproductive age. For proper eradication of infection, the effective concentration of a drug is required at the infection site. Therefore, local delivery is recommended to exert a direct therapeutic effect at the site action that causes a reduction in dose and side effects. The main focus of vaginal drug delivery is to enhance retention time and patient compliance. The high recurrence rate of vaginal infection due to the lack of effective treatment strategies opens the door for new therapeutic approaches. To combat these setbacks, intravaginal gene therapies have been investigated. High attention has been gained by vaginal gene therapy, especially for sexually transmitted infection treatment. Despite much research, no product is available in the market, although in vitro and preclinical data support the vaginal route as an effective route for gene administration. The main focus of this review is to discuss the recent advancement in miniaturized polymeric systems for intravaginal gene therapies to treat local infections. An overview of different barriers to vaginal delivery and challenges of vaginal infection treatment are also summarised.

A drug delivery system constructed by a fusion peptide capturing exosomes targets to titanium implants accurately resulting the enhancement of osseointegration peri-implant

BACKGROUND

Exosomes derived from bone marrow mesenchymal stem cells (BMSC-exos) have been shown triggering osteogenic differentiation and mineralization of MSCs, but exosomes administered via bolus injections are rapidly sequestered and cleared. Therefore, we considered the implant as a new organ of patient's body and expected to find a method to treat implant with BMSC-exos in vivo directly.

METHODS

A fusion peptide (PEP), as a drug delivery system (DDS) which contained a titanium-binding peptide (TBP) possessing the ability to selectively bind to the titanium surface and another peptide CP05 being able to capture exosomes expertly, is constructed to modify the titanium surface.

RESULTS

Both in vitro and in vivo experiments prove PEP retains the ability to bind titanium and exosome simultaneously, and the DDS gain the ability to target exosomes to titanium implants surface following enhancing osseointegration post-implantation. Moreover, the DDS constructed by exosomes of diverse origins shows the similar combination rate and efficiency of therapy.

CONCLUSION

This drug delivery system demonstrates the concept that EXO-PEP system can offer an accurate and efficient therapy for treating implants with long-term effect.

Strategies and progresses for enhancing targeted antibiotic delivery

Antibiotic resistance is a global health issue and a potential risk for society. Antibiotics administered through conventional formulations are devoid of targeting effect and often spread to various undesired body sites, leading to sub-lethal concentrations at the site of action and thus resulting in emergence of resistance, as well as side effects. Moreover, we have a very slim antibiotic pipeline. Drug-delivery systems have been designed to control the rate, time, and site of drug release, and innovative approaches for antibiotic delivery provide a glint of hope for addressing these issues. This review elaborates different delivery strategies and approaches employed to overcome the limitations of conventional antibiotic therapy. These include antibiotic conjugates, prodrugs, and nanocarriers for local and targeted antibiotic release. In addition, a wide range of stimuli-responsive nanocarriers and biological carriers for targeted antibiotic delivery are discussed. The potential advantages and limitations of targeted antibiotic delivery strategies are described along with possible solutions to avoid these limitations. A number of antibiotics successfully delivered through these approaches with attained outcomes and potentials are reviewed.

Construction of multifunctional wound dressings with their application in chronic wound treatment

As the prevalence of diabetes increases year by year and the aging population continues to intensify in the world, chronic wounds such as diabetic foot ulcers and pressure ulcers have become serious problems that threaten people's health, and have brought an enormous burden to the world healthcare system. Conventional clinical treatment of chronic wounds relies on non-specific topical care (including debridement, infection/inflammation control, and frequent wound dressing changes), which can alleviate disease progression and reduce patient suffering to a certain extent, but the overall cure rate is less than 50% and the recurrence rate is high. Traditional wound dressings such as gauze, hydrocolloids, films and foams are single-function, acting as a physical barrier or absorbing exudates, and cannot meet all the needs of the entire chronic wound healing process. Recently, a large number of novel functional dressings have been reported for chronic wound repair. Based on the progress on wound dressings in recent years and the relevant research experience of our group, the review summarizes and discusses the progress on multifunctional wound dressings (such as microneedles, sponges and hydrogels) with anti-inflammatory, antioxidant, antibacterial, pro-angiogenic and tissue adhesive functions in detail. At the same time, the various responsive mechanisms (in vivo microenvironment or in vitro stimulation) of the smart multifunctional wound dressing are also analyzed in detail. It is expected that the review could provide some inspiration and suggestions for research on dressings for chronic wound treatment.

Mg-, Zn-, and Fe-Based Alloys With Antibacterial Properties as Orthopedic Implant Materials

Implant-associated infection (IAI) is one of the major challenges in orthopedic surgery. The development of implants with inherent antibacterial properties is an effective strategy to resolve this issue. In recent years, biodegradable alloy materials have received considerable attention because of their superior comprehensive performance in the field of orthopedic implants. Studies on biodegradable alloy orthopedic implants with antibacterial properties have gradually increased. This review summarizes the recent advances in biodegradable magnesium- (Mg-), iron- (Fe-), and zinc- (Zn-) based alloys with antibacterial properties as orthopedic implant materials. The antibacterial mechanisms of these alloy materials are also outlined, thus providing more basis and insights on the design and application of biodegradable alloys with antibacterial properties as orthopedic implants.

Persistent Luminescence-Based Theranostics for Real-Time Monitoring and Simultaneously Launching Photodynamic Therapy of Bacterial Infections

External light irradiation is usually required in bacterial infection theranostics; however, it is always accompanied by limited light penetration, imaging interference, and incomplete bacterial destruction. Herein, a feasible "image-launching therapy" strategy is developed to integrate real-time optical imaging and simultaneous photodynamic therapy (PDT) of bacterial infections into persistent luminescence (PL) nanoparticles (NPs). Mesoporous silica NPs are used as a substrate for in situ deposition of PL nanodots of ZnGa₂ O₄ :Cr³⁺ to obtain mPL NPs, followed by surface grafting with silicon phthalocyanine (Si-Pc) and electrostatic assembly of cyanine 7 (Cy7) to fabricate mPL@Pc-Cy NPs. The PL emission of light-activated mPL@Pc-Cy NPs is quenched by Cy7 assembly at physiological conditions through the fluorescence resonance energy transfer effect, but is rapidly restored after disassembly of Cy7 in response to bacterial infections. The self-illuminating capabilities of NPs avoid tissue autofluorescence under external light irradiation and achieve real-time colorimetric imaging of bacterial infections. In addition, the afterglow of mPL NPs can persistently excite Si-Pc photosensitizers to promote PDT efficacy for bacterial elimination and accelerate wound full recovery with normal histologic features. Thus, this study expands the theranostic strategy for precise imaging and simultaneous non-antibiotic treatment of bacterial infections without causing side effects to normal tissues.

Nanomaterials enabling clinical translation of antimicrobial photodynamic therapy

Antimicrobial photodynamic therapy (aPDT) has emerged as a promising approach to aid the fight against looming antibiotic resistance. aPDT harnesses the energy of light through photosenstizers to generate highly reactive oxygen species that can inactivate bacteria and fungi with no resistance. To date aPDT has shown great efficacy against microbes causing localized infections in the skin and the oral cavity. However, its wide application in clinical settings has been limited due to both physicochemical and biological challenges. Over the past decade nanomaterials have contributed to promoting photosensitizer performance and aPDT efficiency, yet further developments are required to establish accredited treatment options. In this review we discuss the challenges facing the clinical application of aPDT and the opportunities that nanotechnology may offer to promote the safety and efficiency of aPDT.

Facile Biofilm Penetration of Cationic Liposomes Loaded with DNase I/Proteinase K to Eradicate Cutibacterium acnes for Treating Cutaneous and Catheter Infections

Background

The biofilm produced by Cutibacterium acnes is a major infection threat for skin and implanted catheters. Nanoparticles provide a new approach to eradicate biofilms. The present study evaluated the capability of cationic liposomes loaded with DNase I (DNS) and proteinase K (PK) to remove preformed C. acnes biofilms.

Methods

DNS and PK were able to target and disassemble the biofilm by degrading extracellular polymer substances (EPS). Soyaethyl morpholinium ethosulfate (SME) was used to render a positive charge and enhance the antibacterial activity of the liposomes.

Results

The cationic liposomes containing enzymes yielded monodisperse nanovesicles ranging between 95 and 150 nm. The entrapment efficiency of the enzymes in the liposomes achieved a value of 67–83%. All liposomal formulations suppressed planktonic C. acnes growth at a minimum inhibitory concentration (MIC) equal to the free SME in the solution. The enzyme in the liposomal form inhibited biofilm growth much better than that in the free form, with the dual enzyme-loaded liposomes demonstrating the greatest inhibition of 54% based on a crystal violet assay. The biofilm-related virulence genes PA380 and PA1035 were downregulated by the combined enzymes in the liposomes but not the individual DNS or PK. Scanning electron microscopy (SEM) and confocal microscopy displayed reduced C. acnes aggregates and biofilm thickness by the liposomal system. The liposomes could penetrate through about 85% of the biofilm thickness. The in vitro pig skin permeation also showed a facile delivery of liposomes into the epidermis, deeper skin strata, and hair follicles. The liposomes exhibited potent activity to eliminate C. acnes colonization in mouse skin and catheters in vivo. The colony-forming units (CFUs) in the catheter treated with the liposomes were reduced by 2 logs compared to the untreated control.

Conclusion

The data suggested a safe application of the enzyme-loaded cationic liposomes as antibacterial and antibiofilm agents.