Zinc(II), Palladium(II), and Metal-Free Phthalocyanines Bearing Nipagin-Functionalized Substituents against Candida auris and Selected Multidrug-Resistant Microbes

Multicationic ruthenium phthalocyanines as photosensitizers for photodynamic inactivation of multiresistant microbes

Four photosensitizers PS1a-PS4a consisting in multicationic ruthenium(II) phthalocyanines (RuPcs) have been evaluated in photodynamic inactivation (PDI) of multiresistant microorganisms. The RuPcs, bearing from 4 to 12 terminal ammonium salts, have been designed to target the microorganisms cytoplasmic cell membrane and display high singlet oxygen quantum yields. In addition, PS3a and PS4a were conceived to exhibit multi-target localization by endowing them with amphiphilic character, using two different structural approaches. Under low light regimes, the two hydrophilic PS1a and PS2a, as well as the amphiphilic PS3a show much stronger response against Gram-positive MRSA than that observed for the typical phthalocyanines designed for PDI, namely zinc(II) and palladium(II) complexes, as well as free-base Pcs. Besides, PS1a, PS2a and PS3a show remarkably high activity against the Gram-negative E. coli, although weak fungicidal character against fluconazole-resistant C. albicans. Contrasting, the structurally different, amphiphilic PS4a shows only slight activity for Gram-positive bacteria, despite its ability to cross cell membrane and reach internal organelles. Still, PS4a shows a positive synergistic effect against MRSA when combined with doxycycline, exhibiting an increased activity from about 1.5 to about 4.9 log reduction under the light dose of 30 J/cm2 and the 0.125 mg/L subinhibitory dose of doxycycline.

NIR-activated multifunctional agents for the combined application in cancer imaging and therapy

Anticancer therapies that combine both diagnostic and therapeutic capabilities hold significant promise for enhancing treatment efficacy and patient outcomes. Among these, agents responsive to near-infrared (NIR) photons are of particular interest due to their negligible toxicity and multifunctionality. These compounds are not only effective in photodynamic therapy (PDT), but also serve as contrast agents in various imaging modalities, including fluorescence and photoacoustic imaging. In this review, we explore the photophysical and photochemical properties of NIR-activated porphyrin, cyanine, and phthalocyanines derivatives as well as aggregation-induced emission compounds, highlighting their application in synergistic detection, diagnosis, and therapy. Special attention is given to the design and optimization of these agents to achieve high photostability, efficient NIR absorption, and significant yields of fluorescence, heat, or reactive oxygen species (ROS) generation depending on the application. Additionally, we discuss the incorporation of these compounds into nanocarriers to enhance their solubility, stability, and target specificity. Such nanoparticle-based systems exhibit improved pharmacokinetics and pharmacodynamics, facilitating more effective tumor targeting and broadening the application range to photoacoustic imaging and photothermal therapy. Furthermore, we summarize the application of these NIR-responsive agents in multimodal imaging techniques, which combine the advantages of fluorescence and photoacoustic imaging to provide comprehensive diagnostic information. Finally, we address the current challenges and limitations of photodiagnosis and phototherapy and highlight some critical barriers to their clinical implementation. These include issues related to their phototoxicity, limited tissue penetration, and potential off-target effects. The review concludes by highlighting future research directions aimed at overcoming these obstacles, with a focus on the development of next-generation agents and platforms that offer enhanced therapeutic efficacy and imaging capabilities in the field of cancer treatment.

New strategies to enhance antimicrobial photo-sonodynamic therapy based on nanosensitizers against bacterial infections

The rapid evolution and spread of multidrug resistance among bacterial pathogens has significantly outpaced the development of new antibiotics, underscoring the urgent need for alternative therapies. Antimicrobial photodynamic therapy and antimicrobial sonodynamic therapy have emerged as promising treatments. Antimicrobial photodynamic therapy relies on the interaction between light and a photosensitizer to produce reactive oxygen species, which are highly cytotoxic to microorganisms, leading to their destruction without fostering resistance. Antimicrobial sonodynamic therapy, a novel variation, substitutes ultrasound for light to activate the sonosensitizers, expanding the therapeutic reach. To increase the efficiency of antimicrobial photodynamic therapy and antimicrobial sonodynamic therapy, the combination of these two methods, known as antimicrobial photo-sonodynamic therapy, is currently being explored and considered a promising approach. Recent advances, particularly in the application of nanomaterials, have further enhanced the efficacy of these therapies. Nanosensitizers, due to their improved reactive oxygen species generation and targeted delivery, offer significant advantages in overcoming the limitations of conventional sensitizers. These breakthroughs provide new avenues for treating bacterial infections, especially multidrug-resistant strains and biofilm-associated infections. Continued research, including comprehensive clinical studies, is crucial to optimizing nanomaterial-based antimicrobial photo-sonodynamic therapy for clinical use, ensuring their effectiveness in real-world applications.

Non-peripheral octasubstituted zinc(II) phthalocyanines bearing pyridinepropoxy substituents - Antibacterial, anticancer photodynamic and sonodynamic activity

The novel non-peripheral octa-substituted zinc(II) phthalocyanines with 3- and 4-pyridinepropoxy substituents were synthesized via cyclization of substituted phthalonitriles and further characterized. Their photodynamic and sonodynamic activity were then assessed toward bacteria and cancer cells. Additionally, inhibition activity against common human enzymes was evaluated. The singlet oxygen generation (with 1,3-diphenylisobenzofuran - DPBF as an unspecific chemical quencher of singlet oxygen) were measured under light irradiation, whereas under ultrasounds (1 MHz, 3 W) the stability of DPBF in the presence of sensitizer was evaluated. Both phthalocyanines revealed high photostability in DMSO and moderate in DMF, whereas the sonostability in DMF was moderate. Calculated light-induced singlet oxygen generation quantum yields were similar for both compounds and oscillated around 0.33 in DMF and 0.67 in DMSO. Sonodynamic manner revealed moderately high DPBF decomposition upon 1 MHz. Significant bacterial reduction was noted in both photodynamic and sonodynamic manner, reaching >3 log reduction against MRSA and S. epidermidis. Both compounds showed ca. 50 % viability reduction toward hypopharyngeal tumor (FaDu). Moreover, up to 60 % viability reduction was observed in squamous cell carcinoma (SCC-25). In summary, this molecular building of the efficient phthalocyanine-based sensitizer is a potential therapeutic for photodynamic and sonodynamic applications.

Liposomal Formulations of Novel BODIPY Dimers as Promising Photosensitizers for Antibacterial and Anticancer Treatment

Synthesis, photochemical properties, liposomal encapsulation, and in vitro photodynamic activity studies of novel BODIPY dimer connected at meso-meso positions and its brominated and iodinated analogs were described. UV-Vis measurements indicated that the dimeric structure of obtained BODIPYs did not significantly influence the positions of the absorption maxima. Emission properties and singlet oxygen generation studies revealed a strong heavy atom effect of brominated and iodinated BODIPY dimers, manifested by fluorescence intensity reduction and increased singlet oxygen generation ability compared to analog without halogen atoms. For the in vitro photodynamic activity studies, dimers were incorporated into two different types of liposomes: positively charged DOTAP:POPC and negatively charged POPG:POPC. The photoinactivation studies revealed high activity of brominated and iodinated dimers incorporated into DOTAP:POPC liposomes on both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. Anticancer studies on human breast adenocarcinoma MDA-MB-231 and human ovarian carcinoma A2780 cells revealed that DOTAP:POPC liposomes containing brominated and iodinated dimers were active even at low nanomolar concentrations. In addition, they were more active against MDA-MB-231 cells than A2780 cells, which is particularly important since the MDA-MB-231 cell line represents triple-negative breast cancer, which has limited therapeutic options.

Advances and perspectives in use of semisolid formulations for photodynamic methods

Although nearly 30 years have passed since the introduction of the first clinically approved photosensitizer for photodynamic therapy, progress in developing new pharmaceutical formulations remains unsatisfactory. This review highlights that despite years of research, many recurring challenges and issues remain unresolved. The paper includes an analysis of selected essential studies involving aminolevulinic acid and its derivatives, as well as other photosensitizers with potential for development as medical products. Among various possible vehicles, special attention is given to gelatin, alginates, poly(ethylene oxide), polyacrylic acid, and chitosan. The focus is particularly on infectious and cancerous diseases. Key aspects of developing new semi-solid drug forms should prioritize the creation of easily manufacturable and biocompatible preparations for clinical use. At the same time, new formulations should preserve the primary function of photosensitizers, which is the generation of reactive oxygen species capable of destroying pathogenic cells or tumors. Additionally, the use of adjuvant properties of carriers, which can enhance the effectiveness of macrocycles, is emphasized, especially in chitosan-based antibacterial formulations. Current research indicates that many promising dyes and macrocyclic compounds with high potential as photosensitizers in photodynamic therapy remain unexplored in formulation and development work. This review outlines potential new and previously explored pathways for advancing photosensitizers as active pharmaceutical ingredients (APIs).

Novel thiazolinyl-picolinamide-based palladium(II) complex extenuates the virulence and biofilms of vulvovaginal candidiasis (VVC) causing Candida

Candida infections are growing all over the world as a result of their resistance to anti-fungal drugs. This raises concerns about public health, particularly in cases of vulvovaginal candidiasis (VVC). Therefore, the need for effective treatment options for Candida infections has become crucial. The main goal of the study is to evaluate the efficacy of novel palladium metal complexes against fluconazole-resistant Candida spp., particularly C. albicans and C. auris. The process begins with identifying the minimum inhibitory concentration (MIC), followed by growth curve assays, colony morphology analysis, characterization, and gene expression analysis. The investigation revealed that sub-MIC of Pd(II) complex B (250 μg/mL) inhibited Candida spp. more effectively than amphotericin B (500 μg/mL). Further, Pd(II) complex B drastically reduced the growth of Candida spp. biofilms by 70-80% for nascent biofilms and 70-75% for mature biofilms. Additionally, the yeast-to-hyphal switch and SEM studies revealed that Pd(II) complex B effectively hinders the growth of drug-resistant Candida cells. The gene expression investigation also evidenced that Pd(II) complex B downregulated virulence genes in C. albicans (ERG, EFG, UME6, and HGC) and C. auris (ERG, CDR, and HGC). The findings showed that Pd(II) complex B effectively inhibited the growth of Candida biofilm formation and was reported as a potential anti-biofilm agent against Candida spp. that are resistant to drugs.

Refining antimicrobial photodynamic therapy: effect of charge distribution and central metal ion in fluorinated porphyrins on effective control of planktonic and biofilm bacterial forms

Antibiotic resistance represents a pressing global health challenge, now acknowledged as a critical concern within the framework of One Health. Photodynamic inactivation of microorganisms (PDI) offers an attractive, non-invasive approach known for its flexibility, independence from microbial resistance patterns, broad-spectrum efficacy, and minimal risk of inducing resistance. Various photosensitizers, including porphyrin derivatives have been explored for pathogen eradication. In this context, we present the synthesis, spectroscopic and photophysical characteristics as well as antimicrobial properties of a palladium(II)-porphyrin derivative (PdF2POH), along with its zinc(II)- and free-base counterparts (ZnF2POH and F2POH, respectively). Our findings reveal that the palladium(II)-porphyrin complex can be classified as an excellent generator of reactive oxygen species (ROS), encompassing both singlet oxygen (Φ△ = 0.93) and oxygen-centered radicals. The ability of photosensitizers to generate ROS was assessed using a variety of direct (luminescence measurements) and indirect techniques, including specific fluorescent probes both in solution and in microorganisms during the PDI procedure. We investigated the PDI efficacy of F2POH, ZnF2POH, and PdF2POH against both Gram-negative and Gram-positive bacteria. All tested compounds proved high activity against Gram-positive species, with PdF2POH exhibiting superior efficacy, leading to up to a 6-log reduction in S. aureus viability. Notably, PdF2POH-mediated PDI displayed remarkable effectiveness against S. aureus biofilm, a challenging target due to its complex structure and increased resistance to conventional treatments. Furthermore, our results show that PDI with PdF2POH is more selective for bacterial than for mammalian cells, particularly at lower light doses (up to 5 J/cm2 of blue light illumination). This enhanced efficacy of PdF2POH-mediated PDI as compared to ZnF2POH and F2POH can be attributed to more pronounced ROS generation by palladium derivative via both types of photochemical mechanisms (high yields of singlet oxygen generation as well as oxygen-centered radicals). Additionally, PDI proved effective in eliminating bacteria within S. aureus-infected human keratinocytes, inhibiting infection progression while preserving the viability and integrity of infected HaCaT cells. These findings underscore the potential of metalloporphyrins, particularly the Pd(II)-porphyrin complex, as promising photosensitizers for PDI in various bacterial infections, warranting further investigation in advanced infection models.

Nanotechnology for Dentistry: Prospects and Applications

In the XXI century, application of nanostructures in oral medicine has become common. In oral medicine, using nanostructures for the treatment of dental caries constitutes a great challenge. There are extensive studies on the implementation of nanomaterials to dental composites in order to improve their properties, e.g., their adhesive strength. Moreover, nanostructures are helpful in dental implant applications as well as in maxillofacial surgery for accelerated healing, promoting osseointegration, and others. Dental personal care products are an important part of oral medicine where nanomaterials are increasingly used, e.g., toothpaste for hypersensitivity. Nowadays, nanoparticles such as macrocycles are used in different formulations for early cancer diagnosis in the oral area. Cancer of the oral cavity-human squamous carcinoma-is the sixth leading cause of death. Detection in the early stage offers the best chance at total cure. Along with diagnosis, macrocycles are used for photodynamic mechanism-based treatments, which possess many advantages, such as protecting healthy tissues and producing good cosmetic results. Application of nanostructures in medicine carries potential risks, like long-term influence of toxicity on body, which need to be studied further. The introduction and development of nanotechnologies and nanomaterials are no longer part of a hypothetical future, but an increasingly important element of today's medicine.

New Insights in Phenothiazinium-Mediated Photodynamic Inactivation of Candida Auris

In recent years, Candida auris has emerged as a hazardous hospital-acquired pathogen. Its resistance to antifungal treatments makes it challenging, requiring new approaches to manage it effectively. Herein, we aimed to assess the impact of photodynamic inactivation mediated by methylene blue (MB-PDI) or 1,9-dimethyl MB (DMMB-PDI) combined with a red LED against C. auris. To evaluate the photoinactivation of yeasts, we quantified colony-forming units and monitored ROS production. To gain some insights into the differences between MB and DMMB, we assessed lipid peroxidation (LPO) and mitochondrial membrane potential (ΔΨm). After, we verified the effectiveness of DMMB against biofilms by measuring metabolic activity and biomass, and the structures were analyzed through scanning electron microscopy and optical coherence tomography. We also evaluated the cytotoxicity in mammalian cells. DMMB-PDI successfully eradicated C. auris yeasts at 3 μM regardless of the light dose. In contrast, MB (100 μM) killed cells only when exposed to the highest dose of light. DMMB-PDI promoted higher ROS, LPO and ΔΨm levels than those of MB. Furthermore, DMMB-PDI was able to inhibit biofilm formation and destroy mature biofilms, with no observed toxicity in fibroblasts. We conclude that DMMB-PDI holds great potential to combat the global threat posed by C. auris.

Strategies to Prevent Transmission of Candida auris in Healthcare Settings

Purpose of Review

Candida auris, a recently recognized yeast pathogen, has become a major public health threat due to the problems associated with its accurate identification, intrinsic and acquired resistance to antifungal drugs, and its potential to easily contaminate the environment causing clonal outbreaks in healthcare facilities. These outbreaks are associated with high mortality rates particularly among older patients with multiple comorbidities under intensive care settings. The purpose of this review is to highlight strategies that are being adapted to prevent transmission of C. auris in healthcare settings.

Recent Findings

Colonized patients shed C. auris into their environment which contaminates surrounding equipment. It resists elimination even by robust decontamination procedures and is easily transmitted to new patients during close contact resulting in outbreaks. Efforts are being made to rapidly identify C. auris-infected/C. auris-colonized patients, to determine its susceptibility to antifungals, and to perform effective cleaning and decontamination of the environment and isolation of colonized patients to prevent further transmission.

Summary

Rapid and accurate identification of hospitalized patients infected/colonized with C. auris, rapid detection of its susceptibility patterns, and appropriate use of infection control measures can help to contain the spread of this highly pathogenic yeast in healthcare settings and prevent/control outbreaks.