Antibacterial efficacy of photosensitizer functionalized biopolymeric nanoparticles in the presence of tissue inhibitors in root canal

The Effect of Photodynamic Therapy on Enterococcus spp. and Its Application in Dentistry: A Scoping Review

Enterococci spp. are Gram-positive bacteria that cause mild to severe infections, many associated with the oral cavity, such as periapical infections and healthcare-associated infections (HAIs). Many of these infections become serious diseases that are difficult to resolve, specifically when multidrug-resistant (MDR) strains cause them. In recent years, the number of MDR strains of Enterococcus spp. has increased significantly. This increased prevalence of MDR strains produces significant pressure to generate more antimicrobial therapies, but there is a decline in the production of new antibiotics, driving the development of complementary therapies, such as photodynamic therapy (PDT). PDT combines a photosensitizer agent (PS), light, and oxygen to cause photooxidative stress in bacterial cells. PDT can eradicate Enterococcus spp. contaminations, improve the classic cleaning processes, and eradicate the bacteria in dental pieces. PDT's effectiveness can be improved with nanoparticles that function as carriers. Our work aims to describe the advances in PDT against Enterococcus spp. as a complement to antibiotic therapy, focusing on infections by Enterococcus faecium and Enterococcus faecalis, dental hygiene, and using nanoparticles to improve the antimicrobial effect. A systematic bibliographic search without a meta-analysis was conducted on various databases, using inclusion and exclusion criteria to identify the most relevant research. Of the 193 non-redundant articles found, 65 were selected for a systematic review, from which a summary table was created and a manual description was made. Photodynamic therapy for treating E. faecium and E. faecalis is a widely studied area, with promising results concerning bactericidal effectiveness and reductions in biofilm formation, particularly in regard to dental hygiene. Because most of the studies were conducted in vitro or ex vivo, the results indicated that there were not sufficient data to initiate clinical trials for safety and efficacy studies on humans.

Nanoarchitectonics-Based Materials as a Promising Strategy in the Treatment of Endodontic Infections

Endodontic infections arise from the interactive activities of microbial communities colonizing in the intricate root canal system. The present study aims to update the latest knowledge of nanomaterials, their antimicrobial mechanisms, and their applications in endodontics. A detailed literature review of the current knowledge of nanomaterials used in endodontic applications was performed using the PubMed database. Antimicrobial nanomaterials with a small size, large specific surface area, and high chemical activity are introduced to act as irrigants, photosensitizer delivery systems, and medicaments, or to modify sealers. The application of nanomaterials in the endodontic field could enhance antimicrobial efficiency, increase dentin tubule penetration, and improve treatment outcomes. This study supports the potential of nanomaterials as a promising strategy in treating endodontic infections.

Antibacterial efficiency of adjuvant photodynamic therapy and high-power diode laser in the treatment of young permanent teeth with chronic periapical periodontitis. A prospective clinical study

BACKGROUND

The study aimed at determining antibacterial efficiency of adjuvant photodynamic therapy (PDT) and high-power diode laser (DL) in the treatment of chronic periapical periodontitis (CPP) in young permanent teeth.

METHODS

Forty-four young permanent teeth with CPP were randomly divided into three groups (PDT, DL and control). Each tooth underwent standard chemo-mechanical treatment, while within tested groups was additionally treated by PDT or DL. Bacterial identification and quantification were provided by MALDI-TOF spectrometry and plate counting assay, performed after accessing the canal, following chemo-mechanical preparation, and after PDT or DL procedure where applicable.

RESULTS

Thirty-nine young permanent teeth with CCP (patients age 9.77 ± 1.43) completed the study. Before the treatments, 202 isolates belonging to 13 genera/species, including Streptococcus (36), Actinomyces (34), Peptostreptococcus micros (27), Veillonella (25) and Enterococcus faecalis (22), were recovered. Chemo-mechanical treatment reduced CFU count in the all three groups (p < 0.001), but complete eradication was not observed for any of isolated species. Adjuvant PDT and DL completely eradicated isolates of 8 and 6 bacterial genera/species, resulting in complete bacterial elimination from 53.8% and 30.8% of root canals, respectively. In the rest canals, total Δlog CFUs were 4.71 and 4.58.

CONCLUSION

The results indicated that both PDT and DL could be performed as adjuvants to standard endodontic treatment of the young permanent teeth with CPP.

Nanomaterials Application in Endodontics

In recent years, nanomaterials have become increasingly present in medicine, especially in dentistry. Their characteristics are proving to be very useful in clinical cases. Due to the intense research in the field of biomaterials and nanotechnology, the efficacy and possibilities of dental procedures have immensely expanded over the years. The nano size of materials allows them to exhibit properties not present in their larger-in-scale counterparts. The medical procedures in endodontics are time-consuming and mostly require several visits to be able to achieve the proper result. In this field of dentistry, there are still major issues about the removal of the mostly bacterial infection from the dental root canals. It has been confirmed that nanoparticles are much more efficient than traditional materials and appear to have superior properties when it comes to surface chemistry and bonding. Their unique antibacterial properties are also promising features in every medical procedure, especially in endodontics. High versatility of use of nanomaterials makes them a powerful tool in dental clinics, in a plethora of endodontic procedures, including pulp regeneration, drug delivery, root repair, disinfection, obturation and canal filling. This study focuses on summing up the current knowledge about the utility of nanomaterials in endodontics, their characteristics, advantages, disadvantages, and provides a number of reasons why research in this field should be continued.

Functionalized Nanoparticles Activated by Photodynamic Therapy as an Antimicrobial Strategy in Endodontics: A Scoping Review

The eradication of endodontic pathogens continues to be the focus of the search for new root canal system (RCS) disinfection strategies. This scoping review provides a comprehensive synthesis of antimicrobial photodynamic therapy (aPDT) using nanoparticles (NPs) as an alternative to optimize RCS disinfection. A systematic search up to March 2021 was carried out using the MEDLINE, EMBASE, Scopus, Lilacs, Central Cochrane Library, and BBO databases. We included studies focused on evaluating the activation of NPs by aPDT in inoculated root canals of human or animal teeth or bacterial cultures in the laboratory. The selection process and data extraction were carried out by two researchers independently. A qualitative synthesis of the results was performed. A total of seventeen studies were included, of which twelve showed a substantial antibacterial efficacy, two assessed the substantivity of the disinfection effect, and three showed low cytotoxicity. No adverse effects were reported. The use of functionalized NPs with photosensitizer molecules in aPDT has been shown to be effective in reducing the bacteria count, making it a promising alternative in endodontic disinfection. Further studies are needed to assess the development of this therapy in in vivo conditions, with detailed information about the laser parameters used to allow the development of safe and standardized protocols.

Engineering Polymeric Nanosystems against Oral Diseases

Nanotechnology and nanoparticles (NPs) are at the forefront of modern research, particularly in the case of healthcare therapeutic applications. Polymeric NPs, specifically, hold high promise for these purposes, including towards oral diseases. Careful optimisation of the production of polymeric NPs, however, is required to generate a product which can be easily translated from a laboratory environment to the actual clinical usage. Indeed, considerations such as biocompatibility, biodistribution, and biodegradability are paramount. Moreover, a pre-clinical assessment in adequate in vitro, ex vivo or in vivo model is also required. Last but not least, considerations for the scale-up are also important, together with an appropriate clinical testing pathway. This review aims to eviscerate the above topics, sourcing at examples from the recent literature to put in context the current most burdening oral diseases and the most promising polymeric NPs which would be suitable against them.

The Potential Translational Applications of Nanoparticles in Endodontics

Nanotechnology has substantially progressed in the past decades, giving rise to numerous possible applications in different biomedical fields. In particular, the use of nanoparticles in endodontics has generated significant interest due to their unique characteristics. As a result of their nanoscale dimensions, nanoparticles possess several properties that may enhance the treatment of endodontic infections, such as heightened antibacterial activity, increased reactivity and the capacity to be functionalized with other reactive compounds. Effective disinfection and sealing of the root canal system are the hallmarks for successful endodontic treatment. However, the presence of bacterial biofilms and resistance to endodontic disinfectants pose a significant challenge to this goal. This has encouraged the investigation of antibacterial nanoparticle-based irrigants and intracanal medicaments, which may improve the elimination of endodontic infections. In addition, photosynthesizer-functionalized nanoparticles could also serve as a worthy adjunct to root canal disinfection strategies. Furthermore, despite the myriad of commercially available options for endodontic obturation, the "ideal" material has yet to be conceived. This has led to the development of various experimental nanoparticle-incorporated obturation materials and sealers that exhibit a range of favourable physicochemical properties including enhanced antibacterial efficacy and bioactivity. Nanoparticle applications also show promise in the field of regenerative endodontics, such as supporting the release of bioactive molecules and enhancing the biophysical properties of scaffolds. Given the constantly growing body of research in this field, this article aims to present an overview of the current evidence pertaining to the potential translational applications of nanoparticles in endodontics.

The Benefits of Smart Nanoparticles in Dental Applications

Dentistry, as a branch of medicine, has undergone continuous evolution over time. The scientific world has focused its attention on the development of new methods and materials with improved properties that meet the needs of patients. For this purpose, the replacement of so-called "passive" dental materials that do not interact with the oral environment with "smart/intelligent" materials that have the capability to change their shape, color, or size in response to an externally stimulus, such as the temperature, pH, light, moisture, stress, electric or magnetic fields, and chemical compounds, has received much attention in recent years. A strong trend in dental applications is to apply nanotechnology and smart nanomaterials such as nanoclays, nanofibers, nanocomposites, nanobubbles, nanocapsules, solid-lipid nanoparticles, nanospheres, metallic nanoparticles, nanotubes, and nanocrystals. Among the nanomaterials, the smart nanoparticles present several advantages compared to other materials, creating the possibility to use them in various dental applications, including preventive dentistry, endodontics, restoration, and periodontal diseases. This review is focused on the recent developments and dental applications (drug delivery systems and restoration materials) of smart nanoparticles.

Prospects on Nano-Based Platforms for Antimicrobial Photodynamic Therapy Against Oral Biofilms

Objective: This review clusters the growing field of nano-based platforms for antimicrobial photodynamic therapy (aPDT) targeting pathogenic oral biofilms and increase interactions between dental researchers and investigators in many related fields. Background data: Clinically relevant disinfection of dental tissues is difficult to achieve with aPDT alone. It has been found that limited penetrability into soft and hard dental tissues, diffusion of the photosensitizers, and the small light absorption coefficient are contributing factors. As a result, the effectiveness of aPDT is reduced in vivo applications. To overcome limitations, nanotechnology has been implied to enhance the penetration and delivery of photosensitizers to target microorganisms and increase the bactericidal effect. Materials and methods: The current literature was screened for the various platforms composed of photosensitizers functionalized with nanoparticles and their enhanced performance against oral pathogenic biofilms. Results: The evidence-based findings from the up-to-date literature were promising to control the onset and the progression of dental biofilm-triggered diseases such as dental caries, endodontic infections, and periodontal diseases. The antimicrobial effects of aPDT with nano-based platforms on oral bacterial disinfection will help to advance the design of combination strategies that increase the rate of complete and durable clinical response in oral infections. Conclusions: There is enthusiasm about the potential of nano-based platforms to treat currently out of the reach pathogenic oral biofilms. Much of the potential exists because these nano-based platforms use unique mechanisms of action that allow us to overcome the challenging of intra-oral and hard-tissue disinfection.

Novel nanomaterial-based antibacterial photodynamic therapies to combat oral bacterial biofilms and infectious diseases

Oral diseases such as tooth caries, periodontal diseases, endodontic infections, etc., are prevalent worldwide. The heavy burden of oral infectious diseases and their consequences on the patients' quality of life indicates a strong need for developing effective therapies. Advanced understandings of such oral diseases, e.g., inflammatory periodontal lesions, have raised the demand for antibacterial therapeutic strategies, because these diseases are caused by viruses and bacteria. The application of antimicrobial photodynamic therapy (aPDT) on oral infectious diseases has attracted tremendous interest in the past decade. However, aPDT had a minimal effect on the viability of organized biofilms due to the hydrophobic nature of the majority of the photosensitizers (PSs). Therefore, novel nanotechnologies were rapidly developed to target the delivery of hydrophobic PSs into microorganisms for the antimicrobial performance improvement of aPDT. This review focuses on the state-of-the-art of nanomaterials applications in aPDT against oral infectious diseases. The first part of this article focuses on the cutting-edge research on the synthesis, toxicity, and therapeutic effects of various forms of nanomaterials serving as PS carriers for aPDT applications. The second part discusses nanomaterials applications for aPDT in treatments of oral diseases. These novel bioactive nanomaterials have demonstrated great potential to serve as carriers for PSs to substantially enhance the PDT therapeutic effects. Furthermore, the novel aPDT applications not only have exciting therapeutic potential to inhibit bacterial plaque-initiated oral diseases, but also have a wide applicability to other biomedical and tissue engineering applications.

Photoinactivation of ESKAPE pathogens: overview of novel therapeutic strategy

The emergence of antimicrobial drug resistance requires development of alternative therapeutic options. Multidrug-resistant strains of Enterococcus spp., Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumanii, Pseudomonas aeruginosa and Enterobacter spp. are still the most commonly identified antimicrobial-resistant pathogens. These microorganisms are part of the so-called 'ESKAPE' pathogens to emphasize that they currently cause the majority of hospital acquired infections and effectively 'escape' the effects of antibacterial drugs. Thus, alternative, safer and more efficient antimicrobial strategies are urgently needed, especially against 'ESKAPE' superbugs. Antimicrobial photodynamic inactivation is a therapeutic option used in the treatment of infectious diseases. It is based on a combination of a photosensitizer, light and oxygen to remove highly metabolically active cells.

Revisiting Current Photoactive Materials for Antimicrobial Photodynamic Therapy

Microbial infection is a severe concern, requiring the use of significant amounts of antimicrobials/biocides, not only in the hospital setting, but also in other environments. The increasing use of antimicrobial drugs and the rapid adaptability of microorganisms to these agents, have contributed to a sharp increase of antimicrobial resistance. It is obvious that the development of new strategies to combat planktonic and biofilm-embedded microorganisms is required. Photodynamic inactivation (PDI) is being recognized as an effective method to inactivate a broad spectrum of microorganisms, including those resistant to conventional antimicrobials. In the last few years, the development and biological assessment of new photosensitizers for PDI were accompanied by their immobilization in different supports having in mind the extension of the photodynamic principle to new applications, such as the disinfection of blood, water, and surfaces. In this review, we intended to cover a significant amount of recent work considering a diversity of photosensitizers and supports to achieve an effective photoinactivation. Special attention is devoted to the chemistry behind the preparation of the photomaterials by recurring to extensive examples, illustrating the design strategies. Additionally, we highlighted the biological challenges of each formulation expecting that the compiled information could motivate the development of other effective photoactive materials.

Light Activated Disinfection in Root Canal Treatment-A Focused Review

Light activated disinfection (LAD) is a strategy for optimizing root canal disinfection by using a highly-selective, targeted killing of bacteria using a combination of photosensitizers and light. Over the past decade, numerous in vitro and clinical studies have been performed to demonstrate the effectiveness of this mode of root canal disinfection. While most studies offer an important understanding of the effectiveness of LAD on monospecies biofilms, few have offered credence to the fact that infections of the root canal system are mediated by polymicrobial biofilms. Hence, it is imperative to understand the effect of LAD on polymicrobial biofilms both in terms of microbial killing and the changes in the biofilm architecture. The aim of this review was to systematically review the literature to evaluate the effect of LAD on dual and multispecies biofilms and demonstrate the antibiofilm effect of LAD. Two databases (PubMed and Scopus) were searched to identify eligible studies using a combination of key words. These studies were reviewed to draw conclusions on the effect of LAD on dual and multi species biofilm and the antibiofilm effect of LAD. It was found that LAD alone may be unable to eradicate dual and multispecies biofilms, but it may enhance the effect of conventional canal debridement strategies. Novel formulations of photosensitizers with nanoparticles showed the potential to inhibit biofilm formation and/or disrupt the biofilm architecture.

Protoporphyrin-IX conjugated cellulose nanofibers that exhibit high antibacterial photodynamic inactivation efficacy

Towards the development of anti-infective nanoscale materials employing a photodynamic mechanism of action, we report the synthesis, physical properties (SEM, mechanical strength, water contact angle), spectroscopic characterization (infrared, Raman, DRUV), and evaluation of antibacterial efficacy of porphyrin-conjugated regenerated cellulose nanofibers, termed RC-TETA-PPIX-Zn. Cellulose acetate was electrospun to produce nanofibers, thermally treated to enhance mechanical strength, and finally hydrolyzed to produce regenerated cellulose (RC) nanofibers that possessed a high surface area and nanofibrous structure. Covalent grafting of a protoporphyrin IX (PPIX) photosensitizer using epichlorohydrin/triethylenetetramine (TETA), followed by zinc chelation, afforded RC-TETA-PPIX-Zn. The high surface area afforded by the nanofibers and efficient photosensitizer conjugation led to a very high loading of 412 nmol PPIX/mg material, corresponding to a degree of substitution of 0.1. Antibacterial efficacy was evaluated against Staphylococcus aureus (ATCC-6538) and Escherichia coli (ATCC-8099), with our best results achieving detection limit inactivation (99.999+%) of both bacteria after only 20 min illumination (Xe lamp, λ ≥ 420 nm). No statistically significant loss in antibacterial activity was observed when using nanofibers that had been 'photo-aged' with 5 h of pre-illumination to simulate the effects of photobleaching. Post aPDI, scanning electron microscopy revealed that the bacteria had undergone cell membrane leakage, consistent with oxidative damage caused by photo-generated reactive oxygen species. Taken together, the conjugation strategy employed here provides a scalable, facile and efficient route to creating nanofibrous materials from natural polymers with a high photosensitizer loading, enabling the use of commercially-available neutral porphyrin photosensitizers, such as PPIX, in the design and synthesis of potent anti-infective nanomaterials.

Biofilms in Endodontics-Current Status and Future Directions

Microbiota are found in highly organized and complex entities, known as biofilms, the characteristics of which are fundamentally different from microbes in planktonic suspensions. Root canal infections are biofilm mediated. The complexity and variability of the root canal system, together with the multi-species nature of biofilms, make disinfection of this system extremely challenging. Microbial persistence appears to be the most important factor for failure of root canal treatment and this could further have an impact on pain and quality of life. Biofilm removal is accomplished by a chemo-mechanical process, using specific instruments and disinfecting chemicals in the form of irrigants and/or intracanal medicaments. Endodontic research has focused on the characterization of root canal biofilms and the clinical methods to disrupt the biofilms in addition to achieving microbial killing. In this narrative review, we discuss the role of microbial biofilms in endodontics and review the literature on the role of root canal disinfectants and disinfectant-activating methods on biofilm removal.

Can microbial cells develop resistance to oxidative stress in antimicrobial photodynamic inactivation?

Infections have been a major cause of disease throughout the history of humans on earth. With the introduction of antibiotics, it was thought that infections had been conquered. However, bacteria have been able to develop resistance to antibiotics at an exponentially increasing rate. The growing threat from multi-drug resistant organisms calls for intensive action to prevent the emergence of totally resistant and untreatable infections. Novel, non-invasive, non-antibiotic strategies are needed that act more efficiently and faster than current antibiotics. One promising alternative is antimicrobial photodynamic inactivation (APDI), an approach that produces reactive oxygen species when dyes and light are combined. So far, it has been questionable if bacteria can develop resistance against APDI. This review paper gives an overview of recent studies concerning the susceptibility of bacteria towards oxidative stress, and suggests possible mechanisms of the development of APDI-resistance that should at least be addressed. Some ways to potentiate APDI and also to overcome future resistance are suggested.

Advanced drug delivery systems for local treatment of the oral cavity

Good oral health is of major importance for general health and well-being. Several innovative drug delivery systems have been developed for the local treatment and prevention of various diseases in the oral cavity. However, there are currently few optimal systems and many therapeutic challenges still remain, including low drug efficacy and retention at targeted site of action. The present review provides an insight into the latest drug delivery strategies for the local treatment and prevention of the four most common oral pathologies, namely, dental caries, periodontitis, oral mucosal infections and oral cancer. The potential of bioadhesive formulations, nanoparticulate platforms, multifunctional systems and photodynamic methodologies to improve therapy and prophylaxis in future local applications for the oral cavity will be discussed.

Nanoparticles for antimicrobial purposes in Endodontics: A systematic review of in vitro studies

INTRODUCTION

Antimicrobial nanoparticles with enhanced physiochemical properties have attracted attention as modern antimicrobials, especially in the complicated oral cavity environment. The goal of the present article is to review the current state of nanoparticles used for antimicrobial purposes in root canal infections.

METHODS

A review was conducted in electronic databases using MeSH keywords to identify relevant published literature in English. The analysis and eligibility criteria were documented according to the Preferred Reporting Items for Systematic Reviews and Meta Analysis (PRISMA-guidelines). No restrictions on publication date were imposed. Data regarding root canal disinfections, general antimicrobial mechanisms of nanoparticles, type of nanoparticles as antimicrobial agent and antimicrobial effect of nanoparticles in endodontics were collected and subjected to descriptive data analysis.

RESULTS

The literature search in electronic databases according to the inclusion criteria provided 83 titles and abstracts. Among them 15 papers were related to antimicrobial effect of nanoparticles in Endodontics. Silver nanoparticles with sustainable activity were the most studied agent for its antimicrobial behavior in root canal infection. Aided polymeric nanoparticles with photo or ultrasound, glass bioactive nanoparticles as well as Calcium derivative based nanoparticles, with improved activity in comparison with the non-nano counterparts, are of importance in infection control of dental root canal. Bioactive Non-organic nanoparticles with structural capabilities present enhanced antimicrobial activity in root canal infections.

DISCUSSION

All included studies showed an enhanced or at least equal effect of nanoparticulate systems to combat dental root canal infections compared to conventional antimicrobial procedures. However, it is crucial to understand their shortcomings and their probable cellular effects and toxicity as well as environmental effects.

Photoactivated polycationic bioactive chitosan nanoparticles inactivate bacterial endotoxins

INTRODUCTION

The current root canal disinfection protocols fail to markedly inactivate bacterial endotoxins from infected root dentin. This study aimed to evaluate the ability of antibacterial photodynamic therapy with chitosan-conjugated rose bengal nanoparticles (CSRBnps) to selectively inactivate endotoxins/lipopolysaccharides (LPSs).

METHODS

Antimicrobial agents such as calcium hydroxide (Ca[OH]2), chitosan nanoparticles (CSnps), CSRBnps, and methylene blue (MB) were assessed for their ability to neutralize LPSs obtained from Pseudomonas aeruginosa in a time-dependent interaction with/without photoactivation (20 and 40 J/cm(2)). The inflammatory potential of the treated/untreated LPSs was assessed on macrophage cells (RAW 267.4) using nitric oxide- and enzyme-linked immunosorbent assay (tumor necrosis factor α and interleukin-6 expression)-based analysis. These antimicrobials were tested directly on macrophage cells for cytotoxicity using the mitochondrial activity assay and light microscopy. The data were analyzed using 1-way analysis of variance and the Tukey test.

RESULTS

CSnps were least effective in LPS inactivation. Interluekin-6 expression was reduced only with CSRBnp treatment. CSnps and CSRBnps were completely nontoxic, and MB showed slight toxicity to macrophage cells. Ca(OH)2 was highly cytotoxic (P < .005) even at 30 minutes of exposure. CSRBnps and MB with/without photoactivation significantly inactivated LPSs with reduced nitric oxide and tumor necrosis factor α expression (P < .05). Cell death and detachment after Ca(OH)2 treatment resulted in complete absence of all 3 inflammatory markers.

CONCLUSIONS

Photodynamically activated CSRBnps caused significant inactivation of endotoxins and the subsequent reduction of all tested inflammatory markers from activated macrophages. Antimicrobial CSRBnps in combination with photodynamic therapy showed the potential to effectively inactivate bacterial endotoxins.

Antimicrobial photodynamic inactivation in nanomedicine: small light strides against bad bugs

The relentless advance of drug-resistance among pathogenic microbes, mandates a search for alternative approaches that will not cause resistance. Photodynamic inactivation (PDI) involves the combination of nontoxic dyes with harmless visible light to produce reactive oxygen species that can selectively kill microbial cells. PDI can be broad-spectrum in nature and can also destroy microbial cells in biofilms. Many different kinds of nanoparticles have been studied to potentiate antimicrobial PDI by improving photosensitizer solubility, photochemistry, photophysics and targeting. This review will cover photocatalytic disinfection with titania nanoparticles, carbon nanomaterials (fullerenes, carbon nanotubes and graphene), liposomes and polymeric nanoparticles. Natural polymers (chitosan and cellulose), gold and silver plasmonic nanoparticles, mesoporous silica, magnetic and upconverting nanoparticles have all been used for PDI.

Photodynamic therapy: An adjunct to conventional root canal disinfection strategies

Although chemical-based root canal disinfectants are important to reduce microbial loads and remove infected smear layer from root dentin, they have only a limited ability to eliminate biofilm bacteria, especially from root complexities. This paper explores the novel photodynamic therapy (PDT) for antimicrobial disinfection of root canals. The combination of an effective photosensitizer, the appropriate wavelength of light and ambient oxygen is the key factor in PDT. PDT uses a specific wavelength of light to activate a non-toxic dye (photosensitizer), leading to the formation of reactive oxygen species. These reactive oxygen molecules can damage bacterial proteins, membrane lipids and nucleic acids, which promote bacterial cell death. In, addition PDT may enhance cross-linking of collagen fibrils in the dentin matrix and thereby improving dentin stability. The concept of PDT is plausible and could foster new therapy concepts for endodontics. The available knowledge should enable and encourage steps forward into more clinical-oriented research and development. This article discusses PDT as related to root canal disinfection, including its components, mechanism of action, reviews the current endodontic literature and also highlights the shortcomings and advancements in PDT techniques.

Photosensitisers - the progression from photodynamic therapy to anti-infective surfaces

INTRODUCTION

The application of light as a stimulus in pharmaceutical systems and the associated ability to provide precise spatiotemporal control over location, wavelength and intensity, allowing ease of external control independent of environmental conditionals, has led to its increased use. Of particular note is the use of light with photosensitisers.

AREAS COVERED

Photosensitisers are widely used in photodynamic therapy to cause a cidal effect towards cells on irradiation due to the generation of reactive oxygen species. These cidal effects have also been used to treat infectious diseases. The effects and benefits of photosensitisers in the treatment of such conditions are still being developed and further realised, with the design of novel delivery strategies. This review provides an overview of the realisation of the pharmaceutically relevant uses of photosensitisers, both in the context of current research and in terms of current clinical application, and looks to the future direction of research.

EXPERT OPINION

Substantial advances have been and are being made in the use of photosensitisers. Of particular note are their antimicrobial applications, due to absence of resistance that is so frequently associated with conventional treatments. Their potency of action and the ability to immobilise to polymeric supports is opening a wide range of possibilities with great potential for use in healthcare infection prevention strategies.

Antibiofilm efficacy of photosensitizer-functionalized bioactive nanoparticles on multispecies biofilm

INTRODUCTION

Newer disinfection strategies based on antibacterial nanoparticles and photodynamic therapy (PDT) aim to eliminate residual biofilm bacteria during root canal treatment. The aim of the current study was to test the newly developed rose bengal-functionalized chitosan nanoparticles (CSRBnps) for their interaction/uptake with monospecies bacteria/biofilm and assess their antibiofilm efficacy on a multispecies biofilm model in vitro.

METHODS

The interaction of CSRBnps with bacterial cells was conducted using atomic force microscopy. Their membrane-damaging effect was determined by measuring the absorbance at 260 nm (OD260nm) using Enterococcus faecalis. The penetration of CSRBnps into E. faecalis biofilms was evaluated using confocal laser scanning microscopy (CLSM). Multispecies biofilms of Streptococcus oralis, Prevotella intermedia, and Actinomyces naeslundii were grown on dentin sections for 21 days to assess the antibiofilm efficacy. The biofilms were subjected to PDT (60 J/cm(2)) using CSRBnps and rose bengal. The treated/untreated biofilms were examined under scanning electron microscopy and CLSM.

RESULTS

The CSRBnps synthesized were 60 ± 20 nm and showed absorption spectra similar to rose bengal. Atomic force microscopy showed adherence of CSRBnps to bacteria, roughening of cell surface, and cell disruption after PDT. CSRBnp treatment resulted in significantly increased bacterial membrane damage (P < .05). CSRBnps exhibited deeper penetration into the biofilm structure. Scanning electron microscopy and CLSM confirmed the complete disruption of multispecies biofilm with a reduction in viable bacteria and biofilm thickness (P < .05).

CONCLUSIONS

These novel photosensitizer functionalized bioactive nanoparticles with increased affinity to bacterial cell membrane, higher penetration into biofilm structure, and enhanced ability to eliminate clinically relevant multispecies bacterial biofilm present a potential antibiofilm agent for root canal disinfection.