Inhibition of multi-drug resistant Klebsiella pneumoniae: Nanoparticles induced photoinactivation in presence of efflux pump inhibitor

New Advances in Periodontal Functional Materials Based on Antibacterial, Anti-Inflammatory, and Tissue Regeneration Strategies

With the global population aging, awareness of oral health is rising. Periodontitis, a widespread bacterial infectious disease, is gaining attention. Current novel biomaterials address key clinical issues like bacterial infection, gum inflammation, tooth loosening, and loss, focusing on antibacterial, anti-inflammatory, and tissue regeneration properties. However, strategies that integrate the advantages of these biomaterials to achieve synergistic therapeutic effects by clearing oral biofilms, inhibiting inflammation activation, and restoring periodontal soft and hard tissue functions remain very limited. Recent studies highlight the link between periodontitis and systemic diseases, underscoring the complexity of the periodontal disease. There is an urgent need to find comprehensive treatment plans that address clinical requirements. Whether by integrating new biomaterials to enhance existing periodontal treatments or by developing novel approaches to replace traditional therapies, these efforts will drive advancements in periodontitis treatment. Therefore, this review compares novel biomaterials with traditional treatments. It highlights the design concepts and mechanisms of these functional materials, focusing on their antibacterial, anti-inflammatory, and tissue regeneration properties, and discusses the importance of developing comprehensive treatment strategies. This review aims to provide guidance for emerging periodontitis research and to promote the development of precise and efficient treatment strategies.

The dual role of photodynamic therapy to treat cancer and microbial infection

Photodynamic therapy (PDT) is a minimally invasive treatment showing promise against cancer and microbial infections. PDT targets tumor cells while sparing healthy tissue, reducing side effects. It induces immunogenic cell death, potentially stimulating antitumor immune responses and reducing cancer recurrence. In microbial treatment, PDT effectively combats bacteria, fungi and viruses. Combining PDT with chemotherapy, radiotherapy and immunotherapy enhances its efficacy. However, challenges such as tumor hypoxia, limited tissue penetration and phototoxicity necessitate ongoing research efforts to optimize PDT protocols and overcome limitations. Overall, PDT is versatile and continually advancing with refined protocols to improve its clinical utility against cancer and microbial infections.

Facile fabrication of linezolid/strontium coated hydroxyapatite/graphene oxide nanocomposite for osteoporotic bone defect

Hydroxyapatite (HAp) coatings currently have limited therapeutic applications because they lack anti-infection, osteoinductivity, and poor mechanical characteristics. On the titanium substrate, electrochemical deposition (ECD) was used to construct the strontium (Sr)-featuring hydroxyapatite (HAp)/graphene oxides (GO)/linezolid (LZ) nanomaterial coated with antibacterial and drug delivery properties. The newly fabricated nanomaterials were confirmed by X-ray diffraction analysis (XRD), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) analysis and morphological features were examined by scanning electron microscope (SEM) analysis. The results reveal multiple nucleation sites for SrHAp/GO/LZ composite coatings due to oxygen-comprising moieties on the 2D surface of GO. It was shown to be favorable for osteoblast proliferation and differentiation. The elastic modulus and hardness of LZ nanocomposite with SrHAp/GO/LZ coatings were increased by 67 % and 121 %, respectively. An initial 5 h burst of LZ release from the SrHAp/GO/LZ coating was followed by 14 h of gradual release, owing to LZ's physical and chemical adsorption. The SrHAp/GO/LZ coating effectively inhibited both S. epidermidis and S. aureus, and the inhibition lasted for three days, as demonstrated by the inhibition zone and colony count assays. When MG-63 cells are coated with SrHAp/GO/LZ composite coating, their adhesion, proliferation, and differentiation greatly improve when coated with pure titanium. A novel surface engineering nanomaterial for treating and preventing osteoporotic bone defects, SrHAp/GO/LZ, was shown to have high mechanical characteristics, superior antibacterial abilities, and osteoinductivity.

Photochemical Strategies toward Precision Targeting against Multidrug-Resistant Bacterial Infections

Infectious diseases pose a serious threat and a substantial economic burden on global human and public health security, especially with the frequent emergence of multidrug-resistant (MDR) bacteria in clinical settings. In response to this urgent need, various photobased anti-infectious therapies have been reported lately. This Review explores and discusses several photochemical targeted antibacterial therapeutic strategies for addressing bacterial infections regardless of their antibiotic susceptibility. In contrast to conventional photobased therapies, these approaches facilitate precise targeting of pathogenic bacteria and/or infectious microenvironments, effectively minimizing toxicity to mammalian cells and surrounding healthy tissues. The highlighted therapies include photodynamic therapy, photocatalytic therapy, photothermal therapy, endogenous pigments-based photobleaching therapy, and polyphenols-based photo-oxidation therapy. This comprehensive exploration aims to offer updated information to facilitate the development of effective, convenient, safe, and alternative strategies to counter the growing threat of MDR bacteria in the future.

The role of efflux pump inhibitor in enhancing antimicrobial efficiency of Ag NPs and MB as an effective photodynamic therapy agent

Efflux pumps are active transporters, which allow the cell to remove toxic substances from within the cell including antibiotics and photosensitizer complexes. Efflux pump inhibitors (EPIs), chemicals that prevent the passage of molecules through efflux pumps, play a crucial role in antimicrobial effectiveness against pathogen. In this work, we studied the effect of EPI, namely, reserpine, on photodeactivation rate of pathogens when used with Ag NPs and methylene blue (MB). Our results show that using reserpine led to a higher deactivation rate than Ag NPs and MB alone. The mechanism of this observation was investigated with singlet oxygen generation amount. Additionally, different sizes of Ag NPs were tested with reserpine. Molecular docking calculation shows that reserpine had higher affinity toward AcrB than MB. The improvement in bacterial deactivation rate is attributed to blockage of the AcrAB-TolC efflux pump preventing the removal of MB rather than enhanced singlet oxygen production. These results suggest that using reserpine with nanoparticles and photosynthesize is a promising approach in photodynamic therapy.

Metal nanoparticles against multi-drug-resistance bacteria

Antimicrobial-resistant (AMR) bacterial infections remain a significant public health concern. The situation is exacerbated by the rapid development of bacterial resistance to currently available antimicrobials. Metal nanoparticles represent a new perspective in treating AMR due to their unique mechanisms, such as disrupting bacterial cell membrane potential and integrity, biofilm inhibition, reactive oxygen species (ROS) formation, enhancing host immune responses, and inhibiting RNA and protein synthesis by inducing intracellular processes. Metal nanoparticles (MNPs) properties such as size, shape, surface functionalization, surface charges, and co-encapsulated drug delivery capability all play a role in determining their potential against multidrug-resistant bacterial infections. Silver, gold, zinc oxide, selenium, copper, cobalt, and iron oxide nanoparticles have recently been studied extensively against multidrug-resistant bacterial infections. This review aims to provide insight into the size, shape, surface properties, and co-encapsulation of various MNPs in managing multidrug-resistant bacterial infections.

Emerging nanotechnologies for targeting antimicrobial resistance

Antimicrobial resistance is a leading cause of mortality worldwide. Without newly approved antibiotics and antifungals being brought to the market, resistance is being developed to the ones currently available to clinicians. The reason is the applied evolutionary pressure to bacterial and fungal species due to the wide overuse of common antibiotics and antifungals in clinical practice and agriculture. Biofilms harbour antimicrobial-resistant subpopulations, which make their antimicrobial treatment even more challenging. Nanoparticle-based technologies have recently been shown to successfully overcome antimicrobial resistance in both planktonic and biofilms phenotypes. This results from the combination of novel nanomaterial research and classic antimicrobial therapies which promise to deliver a whole new generation of high-performance active nanocarrier systems. This review discusses the latest developments of promising nanotechnologies with applications against resistant pathogens and evaluates their potential and feasibility for use in novel antimicrobial therapies.

Bacterial microenvironment-responsive dual-channel smart imaging guided on-demand self-regulated photodynamic/chemodynamic synergistic sterilization and wound healing

Bacterial infections pose a serious threat to public health. The integration of photodynamic therapy (PDT) and chemodynamic therapy (CDT) has emerged as a promising means to combat bacterial infection. However,...

Antimicrobial Photodynamic Therapy: Latest Developments with a Focus on Combinatory Strategies

Antimicrobial photodynamic therapy (aPDT) has become a fundamental tool in modern therapeutics, notably due to the expanding versatility of photosensitizers (PSs) and the numerous possibilities to combine aPDT with other antimicrobial treatments to combat localized infections. After revisiting the basic principles of aPDT, this review first highlights the current state of the art of curative or preventive aPDT applications with relevant clinical trials. In addition, the most recent developments in photochemistry and photophysics as well as advanced carrier systems in the context of aPDT are provided, with a focus on the latest generations of efficient and versatile PSs and the progress towards hybrid-multicomponent systems. In particular, deeper insight into combinatory aPDT approaches is afforded, involving non-radiative or other light-based modalities. Selected aPDT perspectives are outlined, pointing out new strategies to target and treat microorganisms. Finally, the review works out the evolution of the conceptually simple PDT methodology towards a much more sophisticated, integrated, and innovative technology as an important element of potent antimicrobial strategies.

Combating Drug-Resistant Bacteria Using Photothermally Active Nanomaterials: A Perspective Review

Injudicious use of antibiotics has been the main driver of severe bacterial non-susceptibility to commonly available antibiotics (known as drug resistance or antimicrobial resistance), a global threat to human health and healthcare. There is an increase in the incidence and levels of resistance to antibacterial drugs not only in nosocomial settings but also in community ones. The drying pipeline of new and effective antibiotics has further worsened the situation and is leading to a potentially "post-antibiotic era." This requires novel and effective therapies and therapeutic agents for combating drug-resistant pathogenic microbes. Nanomaterials are emerging as potent antimicrobial agents with both bactericidal and potentiating effects reported against drug-resistant microbes. Among them, the photothermally active nanomaterials (PANs) are gaining attention for their broad-spectrum antibacterial potencies driven mainly by the photothermal effect, which is characterized by the conversion of absorbed photon energy into heat energy by the PANs. The current review capitalizes on the importance of using PANs as an effective approach for overcoming bacterial resistance to drugs. Various PANs leveraging broad-spectrum therapeutic antibacterial (both bactericidal and synergistic) potentials against drug-resistant pathogens have been discussed. The review also provides deeper mechanistic insights into the mechanisms of the action of PANs against a variety of drug-resistant pathogens with a critical evaluation of efflux pumps, cell membrane permeability, biofilm, and quorum sensing inhibition. We also discuss the use of PANs as drug carriers. This review also discusses possible cytotoxicities related to the therapeutic use of PANs and effective strategies to overcome this. Recent developments, success stories, challenges, and prospects are also presented.

Photodynamic disinfection and its role in controlling infectious diseases

Photodynamic therapy is witnessing a revival of its origins as a response to the rise of multi-drug resistant infections and the shortage of new classes of antibiotics. Photodynamic disinfection (PDDI) of microorganisms is making progresses in preclinical models and in clinical cases, and the perception of its role in the clinical armamentarium for the management of infectious diseases is changing. We review the positioning of PDDI from the perspective of its ability to respond to clinical needs. Emphasis is placed on the pipeline of photosensitizers that proved effective to inactivate biofilms, showed efficacy in animal models of infectious diseases or reached clinical trials. Novel opportunities resulting from the COVID-19 pandemic are briefly discussed. The molecular features of promising photosensitizers are emphasized and contrasted with those of photosensitizers used in the treatment of solid tumors. The development of photosensitizers has been accompanied by the fabrication of a variety of affordable and customizable light sources. We critically discuss the combination between photosensitizer and light source properties that may leverage PDDI and expand its applications to wider markets. The success of PDDI in the management of infectious diseases will ultimately depend on the efficacy of photosensitizers, affordability of the light sources, simplicity of the procedures, and availability of fast and efficient treatments.

Antimicrobial photodynamic therapy (aPDT) against vancomycin resistant Staphylococcus aureus (VRSA) biofilm disruption: A putative role of phagocytosis in infection control

Biofilm mediated infections have major clinical impact. Staphylococcus aureus is a pathogen that frequently causes biofilm forming infections, such as those associated with medical devices and persistent wounds. Microorganisms embedded in biofilm are impervious to antibiotics and other antimicrobial agents, thus they are difficult to eliminate. The upsurge of multi-drug resistant strains makes treating such illnesses even more difficult. Therefore, new strategies are required to combat such type of infections. In this work, we have proposed an alternative therapeutic option to eradicate preformed biofilm of vancomycin resistant Staphylococcus aureus (VRSA) and enhanced phagocytosis by neutrophils in fresh human blood using curcumin mediated antimicrobial photodynamic therapy (aPDT).At sub-MIC of curcumin, different anti-biofilm assays and microscopic examinations were performed, followed by 20 J/cm² of blue laser light irradiation which corresponds to 52 s only. The result showed significant disruption of VRSA biofilm. Moreover, when curcumin-aPDT treated VRSA biofilm was exposed to whole blood from healthy donors, it was nearly completely eradicated. The present study suggests that curcumin-aPDT enhanced phagocytosis may be a useful strategy for inactivating VRSA biofilms adhering to medical implant surfaces.

A systematic review of photodynamic therapy as an antiviral treatment: Potential guidance for dealing with SARS-CoV-2

BACKGROUND

SARS-CoV-2, which causes the coronavirus disease (COVID-19), presents high rates of morbidity and mortality around the world. The search to eliminate SARS-CoV-2 is ongoing and urgent. This systematic review seeks to assess whether photodynamic therapy (PDT) could be effective in SARS-CoV-2 inactivation.

METHODS

The focus question was: Can photodynamic therapy be used as potential guidance for dealing with SARS-CoV-2?". A literature search, according to PRISMA statements, was conducted in the electronic databases PubMed, EMBASE, SCOPUS, Web of Science, LILACS, and Google Scholar. Studies published from January 2004 to June 2020 were analyzed. In vitro and in vivo studies were included that evaluated the effect of PDT mediated by several photosensitizers on RNA and DNA enveloped and non-enveloped viruses.

RESULTS

From 27 selected manuscripts, 26 publications used in vitro studies, 24 were exclusively in vitro, and two had in vitro/in vivo parts. Only one analyzed publication was exclusively in vivo. Meta-analysis studies were unfeasible due to heterogeneity of the data. The risk of bias was analyzed in all studies.

CONCLUSION

The in vitro and in vivo studies selected in this systematic review indicated that PDT is capable of photoinactivating enveloped and non-enveloped DNA and RNA viruses, suggesting that PDT can potentially photoinactivate SARS-CoV-2.

Reversing Bacterial Resistance to Gold Nanoparticles by Size Modulation

One major frustration in developing antibiotics is that bacteria can quickly develop resistance that would require an entirely new cycle of research and clinical testing to overcome. Although plenty of bactericidal nanomaterials have been developed against increasingly severe superbugs, few reports have studied the resistance to these nanomaterials. Herein, we show that antibacterial 4,6-diamino-2-pyrimidine thiol (DAPT)-capped gold nanoparticles (AuDAPTs) can induce a 16-fold increased minimum inhibitory concentration (MIC) of E. coli only after very long term exposure (183 days), without developing cross-resistance to commercialized antibiotics. Strikingly, we recovered the bactericidal activities of AuDAPTs to the resistant strain by tuning the sizes of AuDAPTs without employing new chemicals. Such slow, easy-to-handle resistance induced by AuDAPTs is unprecedented compared to traditional antibiotics or other nanomaterials. In addition to the novel antibacterial activities and biocompatibilities, our approach will accelerate the development of gold nanomaterial-based therapeutics against multi-drug-resistant (MDR) bacterial infections.

Impact of the Peptide WMR-K on Dual-Species Biofilm Candida albicans/Klebsiella pneumoniae and on the Untargeted Metabolomic Profile

In recent years, the scientific community has focused on the development of new antibiotics to address the difficulties linked to biofilm-forming microorganisms and drug-resistant infections. In this respect, synthetic antimicrobial peptides (AMPs) are particularly regarded for their therapeutic potential against a broad spectrum of pathogens. In this work, the antimicrobial and antibiofilm activities of the peptide WMR-K towards single and dual species cultures of Candida albicans and Klebsiella pneumoniae were investigated. We found minimum inhibitory concentration (MIC) values for WMR-K of 10 µM for K. pneumoniae and of 200 µM for C. albicans. Furthermore, sub-MIC concentrations of peptide showed an in vitro inhibition of biofilm formation of mono and polymicrobial systems and also a good biofilm eradication even if higher concentrations of it are needed. In order to provide additional evidence for the effect of the examined peptide, a study of changes in extracellular metabolites excreted and/or uptaken from the culture medium (metabolomic footprinting) in the poly-microbial association of C. albicans and K. pneumoniae in presence and absence of WMR-K was performed. Comparing to the untreated dual species biofilm culture, the metabolomic profile of the WMR-K treated culture appears significantly altered. The differentially expressed compounds are mainly related to the primary metabolic pathways, including amino acids, trehalose, pyruvic acid, glycerol and vitamin B6.

Antimicrobial and antibiofilm photodynamic therapy against vancomycin resistant Staphylococcus aureus (VRSA) induced infection in vitro and in vivo

Biofilm mediated infection caused by multi-drug resistant bacteria are difficult to treat since it protects the microorganisms by host defense system, making them resistant to antibiotics and other antimicrobial agents. Combating such type of nosocomial infection, especially in immunocompromised patients, is an urgent need and foremost challenge faced by clinicians. Therefore, antimicrobial photodynamic therapy (aPDT) has been intensely pursued as an alternative therapy for bacterial infections. aPDT leads to the generation of reactive oxygen species (ROS) that destroy bacterial cells in the presence of a photosensitizer, visible light and oxygen. Here, we elucidated a possibility of its clinical application by reducing the treatment time and exposing curcumin to 20 J/cm² of blue laser light, which corresponds to only 52 s to counteract vancomycin resistant Staphylococcus aureus (VRSA) both in vitro and in vivo. To understand the mechanism of action, the generation of total reactive oxygen species (ROS) was quantified by 2'-7'-dichlorofluorescein diacetate (DCFH-DA) and the type of phototoxicity was confirmed by fluorescence spectroscopic analysis. The data showed more production of singlet oxygen, indicating type-II phototoxicity. Different anti-biofilm assays (crystal violet and congo red assays) and microscopic studies were performed at sub-MIC concentration of curcumin followed by treatment with laser light against preformed biofilm of VRSA. The result showed significant reduction in the preformed biofilm formation. Finally, its therapeutic potential was validated in skin abrasion wistar rat model. The result showed significant inhibition of bacterial growth. Furthermore, immunomodulatory analysis with rat serum was performed. A significant reduction in expression of proinflammatory cytokines TNF-α and IL-6 were observed. Hence, we conclude that curcumin mediated aPDT with 20 J/cm² of blue laser treatment (for 52 s) could be used against multi-drug resistant bacterial infections and preformed biofilm formation as a potential therapeutic approach.

A Multifunctional Nanosystem Based on Bacterial Cell-Penetrating Photosensitizer for Fighting Periodontitis Via Combining Photodynamic and Antibiotic Therapies

Photodynamic therapy (PDT), an emerging approach that involves photosensitizers, light, and molecular oxygen, has shown promise for fighting periodontitis. However, PDT does not always acquire the desired therapeutic outcomes since some photosensitizers have strong hydrophobic properties and are difficult to absorb efficiently by periodontal pathogenic bacteria. Here, a hydrophobic photosensitizer chlorin e6 (Ce6) was hydrophilically modified via conjugation with TAT peptide, a cationic cell-penetrating peptide, to improve its solubility and enhance its bacterial adsorption by promoting its interaction with the negatively charged cell walls and penetration through the cell membranes. The obtained TAT-Ce6 conjugate (TAT-Ce6) was used to prepare self-assembled nanoparticles (NPs) for loading tinidazole (TDZ), a clinically used antibiotic agent, thus hoping to achieve synergistic antiperiodontitis effects through combining PDT and antibiotic therapy. Compared to free Ce6, TAT-Ce6 nanoparticles (TAT-Ce6 NPs) had greatly enhanced adsorption and penetration abilities for periodontal pathogen bacteria and also exhibited significantly increased PDT efficiencies in both periodontal pathogen bacteria and monocyte macrophages. Upon 635 nm laser irradiation, TDZ-loaded TAT-Ce6 (TAT-Ce6/TDZ) NPs exerted remarkable synergistic antiperiodontitis effects of PDT and antibiotic therapy, reflecting in the effective killing of periodontal pathogenic bacteria in vitro and the reduced adsorption of alveolar bone in the Sprague-Dawley rat model of periodontitis. Altogether, this study develops a novel photosensitizer that can be efficiently absorbed by the periodontal pathogenic bacteria and also provides a potent combination strategy of PDT with antibiotic therapy for clinical periodontitis treatment.