Dual antibacterial behavior of a curcumin–upconversion photodynamic nanosystem for efficient eradication of drug-resistant bacteria in a deep joint infection

Biomaterials science and surface engineering strategies for dental peri-implantitis management

Peri-implantitis is a bacterial infection that causes soft tissue inflammatory lesions and alveolar bone resorption, ultimately resulting in implant failure. Dental implants for clinical use barely have antibacterial properties, and bacterial colonization and biofilm formation on the dental implants are major causes of peri-implantitis. Treatment strategies such as mechanical debridement and antibiotic therapy have been used to remove dental plaque. However, it is particularly important to prevent the occurrence of peri-implantitis rather than treatment. Therefore, the current research spot has focused on improving the antibacterial properties of dental implants, such as the construction of specific micro-nano surface texture, the introduction of diverse functional coatings, or the application of materials with intrinsic antibacterial properties. The aforementioned antibacterial surfaces can be incorporated with bioactive molecules, metallic nanoparticles, or other functional components to further enhance the osteogenic properties and accelerate the healing process. In this review, we summarize the recent developments in biomaterial science and the modification strategies applied to dental implants to inhibit biofilm formation and facilitate bone-implant integration. Furthermore, we summarized the obstacles existing in the process of laboratory research to reach the clinic products, and propose corresponding directions for future developments and research perspectives, so that to provide insights into the rational design and construction of dental implants with the aim to balance antibacterial efficacy, biological safety, and osteogenic property.

Nanomaterial-based drug-delivery system as an aid to antimicrobial photodynamic therapy in treating oral biofilm

Diverse microorganisms live as biofilm in the mouth accounts for oral diseases and treatment failure. For decades, the prevention and treatment of oral biofilm is a global challenge. Antimicrobial photodynamic therapy (aPDT) holds promise for oral biofilm elimination due to its several traits, including broad-spectrum antimicrobial capacity, lower possibility of resistance and low cytotoxicity. However, the physicochemical properties of photosensitizers and the biological barrier of oral biofilm have limited the efficiency of aPDT. Nanomaterials has been used to fabricate nanocarriers to improve photosensitizer properties and thus enhance antimicrobial effect. In this review, we have discussed the challenges of aPDT used in dentistry, categorized the nanomaterial-delivery system and listed the possible mechanisms involved in nanomaterials when enhancing aPDT effect.

Near-infrared-driven upconversion nanoparticles with photocatalysts through water-splitting towards cancer treatment

Water splitting is promising, especially for energy and environmental applications; however, there are limited studies on the link between water splitting and cancer treatment. Upconversion nanoparticles (UCNPs) can be used to convert near-infrared (NIR) light to ultraviolet (UV) or visible (Vis) light and have great potential for biomedical applications because of their profound penetration ability, theranostic approaches, low self-fluorescence background, reduced damage to biological tissue, and low toxicity. UCNPs with photocatalytic materials can enhance the photocatalytic activities that generate a shorter wavelength to increase the tissue penetration depth in the biological microenvironment under NIR light irradiation. Moreover, UCNPs with a photosensitizer can absorb NIR light and convert it into UV/vis light and emit upconverted photons, which excite the photoinitiator to create H2, O2, and/or OH˙ via water splitting processes when exposed to NIR irradiation. Therefore, combining UCNPs with intensified photocatalytic and photoinitiator materials may be a promising therapeutic approach for cancer treatment. This review provides a novel strategy for explaining the principles and mechanisms of UCNPs and NIR-driven UCNPs with photocatalytic materials through water splitting to achieve therapeutic outcomes for clinical applications. Moreover, the challenges and future perspectives of UCNP-based photocatalytic materials for water splitting for cancer treatment are discussed in this review.

Impact of PVC microplastics in photodynamic inactivation of Staphylococcus aureus and MRSA

Photodynamic processes have found widespread application in therapies. These processes involve photosensitizers (PSs) that, when excited by specific light wavelengths and in the presence of molecular oxygen, generate reactive oxygen species (ROS), that target cells leading to inactivation. Photodynamic action has gained notable attention in environmental applications, particularly against pathogens and antibiotic-resistant bacteria (ARB) that pose a significant challenge to public health. However, environmental matrices frequently encompass additional contaminants and interferents, including microplastics (MPs), which are pollutants of current concern. Their presence in water and effluents has been extensively documented, highlighting their impact on conventional treatment methods, but this information remains scarce in the context of photodynamic inactivation (PDI) setups. Here, we described the effects of polyvinyl chloride (PVC) microparticles in PDI targeting Staphylococcus aureus and its methicillin-resistant strain (MRSA), using curcumin as a PS under blue light. The presence of PVC microparticles does not hinder ROS formation; however, depending on its concentration, it can impact bacterial inactivation. Our results underscore that PDI remains a potent method for reducing bacterial concentrations in water and wastewater containing ARB, even in highly contaminated scenarios with MPs.

The effects of antimicrobial photodynamic therapy (aPDT) with nanotechnology-applied curcumin and 450nm blue led irradiation on multi-species biofilms in root canals

This study aimed to evaluate the effectiveness of antimicrobial photodynamic therapy (aPDT) utilizing nanotechnology-applied curcumin activated by blue LED (450 nm) on the elimination of microorganisms arranged in multispecies biofilms inside the root canals of extracted human teeth. Forty single-rooted human teeth were used; these were randomized into four experimental groups, each comprising 10 teeth: control group, no treatment; photosensitizer (PS) group, nanotechnology-applied curcumin alone; light group, blue LED used separately; and aPDT group, nanotechnology-applied curcumin activated by blue LED. To carry out the tests, the interiors of the root canals were inoculated with species of Candida albicans (ATCC 90029), Enterococcus faecalis (ATCC 29212), Escherichia coli (ATCC 25922), and methicillin-resistant Staphylococcus aureus (MRSA) (ATCC 43300), using a multispecies biofilm. After the incubation period, the canals were treated according to the experimental groups, with no treatment given in the control group. Studied inasmuch as the antimicrobial effectiveness of aPDT was concerned, it was observed that the greatest reduction in microbial counts using aPDTs was achieved against MRSA (mean reduction = 2.48 Log10 CFU/mL), followed by Escherichia coli (mean reduction = 1.72), and Enterococcus faecalis (mean reduction = 1.65); a reduction greater than 1.5 Log10 CFU/mL showed relevant effectiveness of aPDT against these microorganisms. Of note, aPDT has also shown considerable effectiveness against Candida albicans (mean reduction = 0.71), with a statistical difference in the reduction between the groups. aPDT was effective in reducing all microorganisms examined. The average reduction was greater than 1.5 Log10 in all microorganisms except for Candida albicans. HIGHLIGHTS: • aPDT was a viable treatment for root canals; • Nanotechnological curcumin aPDT was effective in reducing multispecies biofilm microorganisms; • aPDT technique showed efficacy under the worst microbiological conditions , such as mature multispecies biofilm; • Nanotechnological curcumin aPDT was able to reduce Gram positive, negative bacterial and yeasts in root canals.

Photo-responsive polymeric micelles for the light-triggered release of curcumin targeting antimicrobial activity

Nanocarriers have been successfully used to solubilize, deliver, and increase the bioavailability of curcumin (CUR), but slow CUR release rates hinder its use as a topical photosensitizer in antimicrobial photodynamic therapy. A photo-responsive polymer (PRP) was designed for the light-triggered release of CUR with an effective light activation-dependent antimicrobial response. The characterization of the PRP was compared with non-responsive micelles comprising Pluronics™ P123 and F127. According to the findings, the PRP formed photo-responsive micelles in the nanometric scale (< 100 nm) with a lower critical micelle concentration (3.74 × 10^-4 M^-1, 5.8 × 10^-4 M^-1, and 7.2 × 10^-6 M^-1 for PRP, F127, P123, respectively, at 25°C) and higher entrapment efficiency of CUR (88.7, 77.2, and 72.3% for PRP, F127, and P123 micelles, respectively) than the pluronics evaluated. The PRP provided enhanced protection of CUR compared to P123 micelles, as demonstrated in fluorescence quenching studies. The light-triggered release of CUR from PRP occurred with UV light irradiation (at 355 nm and 25 mW cm^-2) and a cumulative release of 88.34% of CUR within 1 h compared to 80% from pluronics after 36 h. In vitro studies showed that CUR-loaded PRP was non-toxic to mammal cell, showed inactivation of the pathogenic microorganisms Candida albicans, Pseudomonas aeruginosa, and methicillin-resistant Staphylococcus aureus, and decreased biofilm biomass when associated with blue light (455  nm, 33.84 J/cm²). The findings show that the CUR-loaded PRP micelle is a viable option for antimicrobial activity.

Upconversion nanoparticles and its based photodynamic therapy for antibacterial applications: A state-of-the-art review

Major medical advances in antibiotics for infectious diseases have dramatically improved the quality of life and greatly increased life expectancy. Nevertheless, the widespread and inappropriate exploitation of antibacterial agents has resulted in the emergence of multi-drug-resistant bacteria (MDR). Consequently, the study of new drugs for the treatment of diseases associated with multi-drug-resistant bacteria and the development of new treatments are urgently needed. Inspiringly, due to the advantages of a wide antimicrobial spectrum, fast sterilization, low resistance, and little damage to host tissues and normal flora, antibacterial photodynamic therapy (APDT), which is based on the interaction between light and a nontoxic photosensitizer (PS) concentrated at the lesion site to generate reactive oxygen species (ROS), has become one of the most promising antibacterial strategies. Recently, a burgeoning APDT based on a variety of upconversion nanoparticles (UCNPs) such as PS and near-infrared (NIR) light has been fully integrated in antibacterial applications and achieved excellent performances. Meanwhile, conjugated nanoparticles have been frequently reported in UCNP design, including surface-modified PS conjugates, antibiotic-PS conjugates, and dual or multiple antibacterial modal PS conjugates. This article provides an overview of the state-of-the-art design and bactericidal effects of UCNPs and their based APDTs. The first part discusses the design and mechanisms for UCNPs currently implemented in biomedicine. The second part focuses on the applications and antimicrobial effects of diverse APDT based on UCNPs in antibacterial-related infectious diseases.

Orange-red to NIR emissive carbon dots for antimicrobial, bioimaging and bacteria diagnosis

Antimicrobial photodynamic therapy (aPDT) has become a popular technology for the treatment of bacterial infections. The development of antimicrobial agents combining diagnosis and treatment remains a major challenge. Herein, curcumin carbon quantum dots (Cur-NRCQDs) with antibacterial and imaging effects were synthesized using a hydrothermal method. The fluorescence absorption range of the Cur-NRCQDs in aqueous solution was 555 to 850 nm, showing orange-red to near infrared (NIR) fluorescence, and its maximum emission wavelength was 635 nm. At the same time, Cur-NRCQDs improved the efficiency of Cur as the photosensitizer (PS), showed good storage and light stability, and enhanced the efficiency of reactive oxygen (ROS) generation and antibacterial activity. Under the irradiation of a xenon lamp, Cur-NRCQDs inactivated 100% Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) at concentrations of 10 and 15 μM, respectively. The possible reason for this was that under PDT, the ROS produced by the Cur-NRCQDs destroyed the integrity of the cell membrane, resulting in leakage of the contents. In addition, the Cur-NRCQDs showed good cell compatibility, as they can also enter bacteria and cells for imaging, so they can be employed for the detection of bacteria and cell tissues. Therefore, Cur-NRCQDs are an ideal candidate material for aPDT treatment and fluorescent bioimaging.

NIR-Responsive TiO2 Biometasurfaces: Toward In Situ Photodynamic Antibacterial Therapy for Biomedical Implants

Implant-related microbial infection is a challenging clinical problem, and its treatment requires efficient eradication of the biofilm from the implant surface. Near-infrared (NIR)-responsive strategies are proposed as an emerging efficient antibacterial therapy. However, the utilization of photosensitizers or photocatalytic/photothermal nanomaterials in the available approach likely induces high potential risks of interfacial deterioration and biosafety compromise. Herein, a TiO₂ /TiO_{2- x} metasurface with potent NIR-responsive antibacterial activity is produced on a Ti alloy implant by a newly invented topochemical conversion-based alkaline-acid bidirectional hydrothermal method (aaBH). Electromagnetic simulations prove that NIR absorption and near-field distribution of the metasurface can be tuned by the dimension and arrangement of the nanostructural unit. Promising antibacterial efficacy is proved by both in vitro and in vivo tests, with low-power NIR irradiation for 10 min. Besides, the designed nanostructure in the metasurface itself also shows excellence in enhancing the adhesion-related gene expression of human gingival fibroblasts that are exposed to 10 min of NIR irradiation, proving the potent nanostructure-induced biological effects. This work provides a biosafe and upscalable metasurfacing approach with extraordinary capacity of manipulating light adsorption, photocatalysis, and biological properties.

808 nm NIR-triggered Camellia sapogein/curcumin based antibacterial upconversion nanoparticles for synergistic photodynamic-chemical combined therapy

Antibacterial upconversion nanoparticles (UCNP) based photodynamic-chemical combined therapy (UCNP-aPCCT) provides an ideal method to solve the antibiotic-resistant bacteria in deep-tissue infection. Saponin is a kind natural product exhibiting promising antibacterial...

Organic Photo-antimicrobials: Principles, Molecule Design, and Applications

The emergence of multi-drug-resistant pathogens threatens the healthcare systems world-wide. Recent advances in phototherapy (PT) approaches mediated by photo-antimicrobials (PAMs) provide new opportunities for the current serious antibiotic resistance. During the PT treatment, reactive oxygen species or heat produced by PAMs would react with the cell membrane, consequently leaking cytoplasm components and effectively eradicating different pathogens like bacteria, fungi, viruses, and even parasites. This Perspective will concentrate on the development of different organic photo-antimicrobials (OPAMs) and their application as practical therapeutic agents into therapy for local infections, wound dressings, and removal of biofilms from medical devices. We also discuss how to design highly efficient OPAMs by modifying the chemical structure or conjugating with a targeting component. Moreover, this Perspective provides a discussion of the general challenges and direction for OPAMs and what further needs to be done. It is hoped that through this overview, OPAMs can prosper and will be more widely used for microbial infections in the future, especially at a time when the global COVID-19 epidemic is getting more serious.

Synergistic Lysozyme-Photodynamic Therapy Against Resistant Bacteria based on an Intelligent Upconversion Nanoplatform

The rapid emergence of drug-resistant bacteria has raised a great social concern together with the impetus for exploring advanced antibacterial ways. NIR-triggered antimicrobial photodynamic therapy (PDT) by lanthanide-doped upconversion nanoparticles (UCNP) as energy donor exhibits the advantages of high tissue penetration, broad antibacterial spectrum and less acquired resistance, but is still limited by its low efficacy. Now we designed a bio-inorganic nanohybrid and combined lysozyme (LYZ) with UCNP-PDT system to enhance the efficiency against resistant bacteria. Benefiting from the rapid adhesion to bacteria, intelligently bacteria-responsive LYZ release and synergistic LYZ-PDT effect, the nanoplatform achieves an exceptionally strong bactericidal capacity and conspicuous bacteriostasis on methicillin-resistant S. aureus. These findings pave the way for designing efficiently antibacterial nanomaterials and provide a new strategy for combating deep-tissue bacterial infection.

Current Trends in Drug Delivery System of Curcumin and its Therapeutic Applications

Curcumin is a poly phenolic compound extracted from turmeric. Over the past years, it has acquired significant interest among researchers due to its numerous pharmacological activities like anti- cancer, anti-alzheimer, anti-diabetic, anti-bacterial, anti-inflammatory and so on. However, the clinical use of curcumin is still obstructed due to tremendously poor bioavailability, rapid metabolism, lower gastrointestinal absorption, and low permeability through cell that makes its pharmacology thrilling. These issues have led to enormous surge of investigation to develop curcumin nano formulations which can overcome these restrictive causes. The scientists all across the universe are working on designing several drug delivery systems viz. liposomes, micelles, magnetic nano carriers, etc. for curcumin and its composites which not only improve its physiochemical properties but also enhanced its therapeutic applications. The review aims to systematically examine the treasure of information about the medicinal use of curcumin. This article delivers a general idea of the current study piloted to overwhelm the complications with the bioavailability of curcumin which have exhibited an enhanced biological activity than curcumin. This article explains the latest and detailed study of curcumin and its conjugates, its phytochemistry and biological perspectives and also proved curcumin as an efficient drug candidate for the treatment of numerous diseases. Recent advancements and futuristic viewpoints are also deliberated, which shall help researchers and foster commercial translations of improved nanosized curcumin combination for the treatment of various diseases.

Phototherapy-based combination strategies for bacterial infection treatment

The development of nanomedicine is expected to provide an innovative direction for addressing challenges associated with multidrug-resistant (MDR) bacteria. In the past decades, although nanotechnology-based phototherapy has been developed for antimicrobial treatment since it rarely causes bacterial resistance, the clinical application of single-mode phototherapy has been limited due to poor tissue penetration of light sources. Therefore, combinatorial strategies are being developed. In this review, we first summarized the current phototherapy agents, which were classified into two functional categories: organic phototherapy agents (e.g., small molecule photosensitizers, small molecule photosensitizer-loaded nanoparticles and polymer-based photosensitizers) and inorganic phototherapy agents (e.g., carbo-based nanomaterials, metal-based nanomaterials, composite nanomaterials and quantum dots). Then the development of emerging phototherapy-based combinatorial strategies, including combination with chemotherapy, combination with chemodynamic therapy, combination with gas therapy, and multiple combination therapy, are presented and future directions are further discussed. The purpose of this review is to highlight the potential of phototherapy to deal with bacterial infections and to propose that the combination therapy strategy is an effective way to solve the challenges of single-mode phototherapy.

NIR light-assisted phototherapies for bone-related diseases and bone tissue regeneration: A systematic review

Recently, the rapid development of biomaterials has induced great interest in the precisely targeted treatment of bone-related diseases, including bone cancers, infections, and inflammation. Realizing noninvasive therapeutic effects, as well as improving bone tissue regeneration, is essential for the success of bone‑related disease therapies. In recent years, researchers have focused on the development of stimuli-responsive strategies to treat bone-related diseases and to realize bone regeneration. Among the various external stimuli for targeted therapy, near infrared (NIR) light has attracted considerable interests due to its high tissue penetration capacity, minimal damage toward normal tissues, and easy remote control properties. The main objective of this systematic review was to reveal the current applications of NIR light-assisted phototherapy for bone-related disease treatment and bone tissue regeneration. Database collection was completed by June 1, 2020, and a total of 81 relevant studies were finally included. We outlined the various therapeutic applications of photothermal, photodynamic and photobiomodulation effects under NIR light irradiation for bone‑related disease treatment and bone regeneration, based on the retrieved literatures. In addition, the advantages and promising applications of NIR light-responsive drug delivery systems for spatiotemporal-controlled therapy were summarized. These findings have revealed that NIR light-assisted phototherapy plays an important role in bone-related disease treatment and bone tissue regeneration, with significant promise for further biomedical and clinical applications.

Near-infrared-excited upconversion photodynamic therapy of extensively drug-resistant Acinetobacter baumannii based on lanthanide nanoparticles

Extensively drug-resistant Acinetobacter baumannii (XDR-AB) has raised considerable concerns due to its mortal damage to humans and its high transmission rate of infections in hospitals. However, current antibiotics not only show poor anti-infection effects in vivo but also frequently cause high nephrotoxicity and neurotoxicity. Herein, we report a near-infrared (NIR) light-initiated antimicrobial photodynamic therapy (aPDT) to effectively treat in vivo XDR-AB infections based on photosensitizer (PS) loaded upconversion nanoparticles (UCNPs, LiYF₄:Yb/Er). Such nanoagents feature robust NIR triggered UC luminescence and high-efficiency energy transfer from UCNPs to the loaded PS, thereby allowing NIR-triggered generation of reactive oxygen species (ROS) for destroying the bacterial cell membrane. This strategy permits a high antibacterial activity against XDR-AB, resulting in a decline of 4.72 log₁₀ in viability at a dose of 50 μg mL^-1 UCNPs-PVP-RB with 980 nm laser irradiation (1 W cm^-2). More significantly, we can achieve excellent therapeutic efficacy against deep-tissue (about 5 mm) XDR-AB infections without causing any side effects in the murine model. In brief, such NIR-activated aPDT may open up new avenues for treating various deep-tissue intractable infections.

Poly(selenoviologen)-Assembled Upconversion Nanoparticles for Low-Power Single-NIR Light-Triggered Synergistic Photodynamic and Photothermal Antibacterial Therapy

The development of a highly effective photosensitizer (PS) that can be activated with a low-power single light is a pressing issue. Herein, we report a PS for synergistic photodynamic and photothermal therapy constructed through self-assembly of poly(selenoviologen) on the surface of core-shell NaYF₄:Yb/Tm@NaYF₄ upconversion nanoparticles. The hybrid UCNPs/PSeV PS showed strong ROS generation ability and high photothermal conversion efficiency (∼52.5%) under the mildest reported-to-date irradiation conditions (λ = 980 nm, 150 mW/cm², 4 min), leading to a high efficiency in killing methicillin-resistant Staphylococcus aureus (MRSA) both in vitro and in vivo. Remarkably, after intravenous injection, the reported PS accumulated preferentially in deep MRSA-infected tissues and achieved an excellent therapeutic index. This PS design realizes a low-power single-NIR light-triggered synergistic phototherapy and provides a simple and versatile strategy to develop safe clinically translatable agents for efficient treatment of deep tissue bacterial inflammations.

Anti-microbial activity of curcumin nanoformulations: New trends and future perspectives

Curcumin has been used in numerous anti-microbial research because of its low side effects and extensive traditional applications. Despite having a wide range of effects, the intrinsic physicochemical characteristics such as low bioavailability, poor water solubility, photodegradation, chemical instability, short half-life and fast metabolism of curcumin derivatives limit their pharmaceutical importance. To overcome these drawbacks and improve the therapeutic ability of curcuminoids, novel approaches have been attempted recently. Nanoparticulate drug delivery systems can increase the efficiency of curcumin in several diseases, especially infectious diseases. These innovative strategies include polymeric nanoparticles, hydrogels, nanoemulsion, nanocomposite, nanofibers, liposome, nanostructured lipid carriers (NLCs), polymeric micelles, quantum dots, polymeric blend films and nanomaterial-based combination of curcumin with other anti-bacterial agents. Integration of curcumin in these delivery systems has displayed to improve their solubility, bioavailability, transmembrane permeability, prolong plasma half-life, long-term stability, target-specific delivery and upgraded the therapeutic effects. In this review paper, a range of in vitro and in vivo studies have been critically discussed to explore the therapeutic viability and pharmaceutical significance of the nano-formulated delivery systems to elevate the anti-bacterial activities of curcumin and its derivatives.

Role of Cholesterol Conjugation in the Antibacterial Photodynamic Therapy of Branched Polyethylenimine-Containing Nanoagents

Photodynamic therapy is a promising approach for fighting bacterial infections because it can induce few side effects, develop no drug resistance, and realize precise treatment. However, most photosensitizers (PSs) have the disadvantages of poor water-solubility, severe self-quenching, and potential toxicity. Here, the cationic polymer polyethyleneimine (PEI) was used to prepare a cholesterol- and chlorin e6 (Ce6, a common PS)-conjugated compound via the carboxyl-amine reaction or the acyl chloride-amine reaction (abbreviated as Chol-PEI-Ce6). The as-prepared Chol-PEI-Ce6 molecules can self-assemble into close-to-spherical nanoparticles (NPs) with an average diameter of ∼15 nm and can bind to the bacterial surfaces via the synergistic hydrophobic insertion of the cholesterol moieties and electrostatic interaction between the cationic amine groups of PEI and the bacterial surfaces. Upon light irradiation, the NPs can effectively inactivate both Gram-positive and Gram-negative bacteria. Besides, the interaction between Chol-PEI-Ce6 NPs and bacteria markedly enhances the production of intracellular reactive oxygen species after light irradiation, which may account for the excellent antibacterial performance of the NPs. More importantly, the NPs possess negligible dark cytotoxicity and good hemocompatibility. Therefore, the present work may have strong implications for developing novel antibacterial agents to fight against bacterial infections.

Anti-Biofilm Property of Bioactive Upconversion Nanocomposites Containing Chlorin e6 against Periodontal Pathogens

Photodynamic therapy (PDT) based periodontal disease treatment has received extensive attention. However, the deep tissue location of periodontal plaque makes the conventional PDT encounter a bottleneck. Herein, upconversion fluorescent nanomaterial with near-infrared light excitation was introduced into the treatment of periodontal disease, overcoming the limited tissue penetration depth of visible light in PDT. Photosensitizer Ce6 molecules were combined with upconversion nanoparticles (UCNPs) NaYF4:Yb,Er with a novel strategy. The hydrophobic UCNPs were modified with amphiphilic silane, utilizing the hydrophobic chain of the silane to bind to the hydrophobic groups of the UCNPs through a hydrophobic-hydrophobic interaction, and the Ce6 molecules were loaded in this hydrophobic layer. This achieves both the conversion of the hydrophobic to the hydrophilic surface and the loading of the oily photosensitizer molecules. Because the excitation position of the Ce6 molecule is in the red region, Mn ions were doped to enhance red light, and thus the improved PDT function. This Ce6 loaded UCNPs composites with efficient red upconversion luminescence show remarkable bacteriological therapeutic effect on Porphyromonas gingivalis, Prevotella intermedia and Fusobacterium nucleatum and the corresponding biofilms under 980 nm irradiation, indicating a high application prospect in the treatment of periodontal diseases.

Chitosan-Based Drug Delivery Systems for Optimization of Photodynamic Therapy: a Review

Drug delivery systems (DDS) can be designed to enrich the pharmacological and therapeutic properties of several drugs. Many of the initial obstacles that impeded the clinical applications of conventional DDS have been overcome with nanotechnology-based DDS, especially those formed by chitosan (CS). CS is a linear polysaccharide obtained by the deacetylation of chitin, which has potential properties such as biocompatibility, hydrophilicity, biodegradability, non-toxicity, high bioavailability, simplicity of modification, aqueous solubility, and excellent chemical resistance. Furthermore, CS can prepare several DDS as films, gels, nanoparticles, and microparticles to improve delivery of drugs, such as photosensitizers (PS). Thus, CS-based DDS are broadly investigated for photodynamic therapy (PDT) of cancer and fungal and bacterial diseases. In PDT, a PS is activated by light of a specific wavelength, which provokes selective damage to the target tissue and its surrounding vasculature, but most PS have low water solubility and cutaneous photosensitivity impairing the clinical use of PDT. Based on this, the application of nanotechnology using chitosan-based DDS in PDT may offer great possibilities in the treatment of diseases. Therefore, this review presents numerous applications of chitosan-based DDS in order to improve the PDT for cancer and fungal and bacterial diseases.