Nanoscale fluconazole-constructed metal-organic frameworks with smart drug release for eradication of Candida biofilms in vulvovaginitis infection

Fungal infections associated with oral, gynecological, and skin ailments pose significant clinical challenges. The presence of biofilms often hampers the efficacy of conventional antifungal drugs owing to the complex microenvironment they create. In this study, the widely used antifungal medication fluconazole is utilized as a foundational component to be incorporated into zinc 2-methylimidazolate frameworks, resulting in the synthesis of nanoscale fluconazole-constructed metal-organic frameworks (F-ZIF). The F-ZIF is constructed through coordination interactions between zinc and fluconazole, retaining the structure and pH-responsiveness of the zinc 2-methylimidazolate framework. The pH-responsiveness F-ZIF makes sure the fluconazole can be released in acidic biofilm, which prevents the undesired release in healthy tissue, resulting in good biocompatibility both in vitro and in vivo. The in vitro studies demonstrated that F-ZIF exhibits enhanced efficacy in eradicating fungal pathogens in their biofilm growth state compared with the free fluconazole. Furthermore, in vivo experiments reveal the better effectiveness of F-ZIF in treating Candida albicans-induced vulvovaginal candidiasis, and less infection-related inflammation was observed. Hence, the one-port synthetic F-ZIF presents a promising solution for addressing fungal biofilm-related infections.

Meyer R, Lund MB, Schlafer S. Combined pH ratiometry and fluorescence lectin-binding analysis (pH-FLBA) for microscopy-based analyses of biofilm pH and matrix carbohydrates

Bacterial biofilms have a complex and heterogeneous three-dimensional architecture that is characterized by chemically and structurally distinct microenvironments. Confocal microscopy-based pH ratiometry and fluorescence lectin-binding analysis (FLBA) are well-established methods to characterize pH developments and the carbohydrate matrix architecture of biofilms at the microscale. Here, we developed a combined analysis, pH-FLBA, to concomitantly map biofilm pH and the distribution of matrix carbohydrates in bacterial biofilms while preserving the biofilm microarchitecture. As a proof of principle, the relationship between pH and the presence of galactose- and fucose-containing matrix components was investigated in dental biofilms grown with and without sucrose. The pH response to a sucrose challenge was monitored in different areas at the biofilm base using the ratiometric pH-sensitive dye C-SNARF-4. Thereafter, the fucose- and galactose-specific fluorescently labeled lectins Aleuria aurantia lectin (AAL) and Morus nigra agglutinin G (MNA-G) were used to visualize carbohydrate matrix components in the same biofilm areas and their immediate surroundings. Sucrose during growth significantly decreased biofilm pH (P < 0.05) and increased the amounts of both MNA-G- and AAL-targeted matrix carbohydrates (P < 0.05). Moreover, it modulated the biofilm composition towards a less diverse community dominated by streptococci, as determined by 16S rRNA gene sequencing. Altogether, these results suggest that the production of galactose- and fucose-containing matrix carbohydrates is related to streptococcal metabolism and, thereby, pH profiles in dental biofilms. In conclusion, pH-FLBA using lectins with different carbohydrate specificities is a useful method to investigate the association between biofilm pH and the complex carbohydrate architecture of bacterial biofilms.IMPORTANCEBiofilm pH is a key regulating factor in several biological and biochemical processes in environmental, industrial, and medical biofilms. At the microscale, microbial biofilms are characterized by steep pH gradients and an extracellular matrix rich in carbohydrate components with diffusion-modifying properties that contribute to bacterial acid-base metabolism. Here, we propose a combined analysis of pH ratiometry and fluorescence lectin-binding analysis, pH-FLBA, to concomitantly investigate the matrix architecture and pH developments in microbial biofilms, using complex saliva-derived biofilms as an example. Spatiotemporal changes in biofilm pH are monitored non-invasively over time by pH ratiometry, while FLBA with lectins of different carbohydrate specificities allows mapping the distribution of multiple relevant matrix components in the same biofilm areas. As the biofilm structure is preserved, pH-FLBA can be used to investigate the in situ relationship between the biofilm matrix architecture and biofilm pH in complex multispecies biofilms.

Effect of 5-Aminolevulinic Acid Photodynamic Therapy on Aspergillus fumigatus Biofilms in Vitro

Aspergillus fumigatus biofilm development results in enhanced pathogenicity and treatment resistance. Most contemporary antibiotics, however, are unable to eliminate biofilms. In recent years, with the application of new photosensitizers and the development of treatment, ALA-PDT (5-aminolevulinic acid photodynamic treatment) has achieved remarkable curative effect in the treatment of fungal infectious diseases; however, no research has been conducted on ALA-PDT against A. fumigatus. This study investigated the inhibitory effect of ALA-PDT at various 5-aminolevulinic acid concentrations and light doses on A. fumigatus planktonic and biofilms in vitro. We found that ALA-PDT may successfully inhibit the development of A. fumigatus biofilm and disintegrate mature biofilm. After ALA-PDT treatment, the adherence rate and vitality dramatically decreased, and the biofilm's structure was severely compromised. Our findings show for the first time that ALA-PDT may be used to prevent the formation of A. fumigatus biofilm and disturb the structure of mature biofilm, and that it could be employed as a therapeutic therapy for A. fumigatus superficial infection.

Cryptococcus escapes host immunity: What do we know?

Cryptococcus is an invasive fungus that seriously endangers human life and health, with a complex and well-established immune-escaping mechanism that interferes with the function of the host immune system. Cryptococcus can attenuate the host’s correct recognition of the fungal antigen and escape the immune response mediated by host phagocytes, innate lymphoid cells, T lymphocytes, B lymphocytes with antibodies, and peripheral cytokines. In addition, the capsule, melanin, dormancy, Titan cells, biofilm, and other related structures of Cryptococcus are also involved in the process of escaping the host’s immunity, as well as enhancing the ability of Cryptococcus to infect the host.

Real-time monitoring of mono- and dual-species biofilm formation and eradication using microfluidic platform

In a human host, bacterial Staphylococcus aureus and fungal Candida albicans pathogens form a mixed biofilm that causes severe mortality and morbidity. However, research on the formation and eradication of mixed biofilms under dynamic conditions is lacking. Thus, this study employed a microfluidic technique to analyze the real-time formation of mono- and dual-species (S. aureus and C. albicans) biofilms and noninvasive optical treatment of the established mature biofilm using 405-nm laser light. A herringbone mixer thoroughly mixed both bacterial and fungal cells in the growth media before being injected into the observation channels on the microfluidic chip. At a flow rate of 1.0 µL/min of growth media for 24 h, the bacterial biofilm coverage was up to 15% higher than that of the fungal biofilm (50% for bacteria vs. 35% for fungus). On the other hand, the dual-species biofilm yielded the highest coverage of ~ 96.5% because of the collective interaction between S. aureus and C. albicans. The number of cell proliferation events in S. aureus was higher than that of C. albicans for 12 h, which indicates that the S. aureus biofilm was developed faster than C. albicans. The novel in situ test platform showed a significant bactericidal effect (80%) of the 405-nm laser light at 1080 J/cm² towards the established S. aureus biofilm, whereas the same treatment removed approximately 69% of the mixed cells in the dual-species biofilm. This study revealed that the developed microfluidic platform could be utilized to monitor the formation of dual-species biofilms in real-time and laser-induced antimicrobial effects on dual-species biofilms.

Fluorescent toys 'n' tools lighting the way in fungal research

Although largely overlooked compared to bacterial infections, fungal infections pose a significant threat to the health of humans and other organisms. Many pathogenic fungi, especially Candida species, are extremely versatile and flexible in adapting to various host niches and stressful situations. This leads to high pathogenicity and increasing resistance to existing drugs. Due to the high level of conservation between fungi and mammalian cells, it is hard to find fungus-specific drug targets for novel therapy development. In this respect, it is vital to understand how these fungi function on a molecular, cellular as well as organismal level. Fluorescence imaging allows for detailed analysis of molecular mechanisms, cellular structures and interactions on different levels. In this manuscript, we provide researchers with an elaborate and contemporary overview of fluorescence techniques that can be used to study fungal pathogens. We focus on the available fluorescent labelling techniques and guide our readers through the different relevant applications of fluorescent imaging, from subcellular events to multispecies interactions and diagnostics. As well as cautioning researchers for potential challenges and obstacles, we offer hands-on tips and tricks for efficient experimentation and share our expert-view on future developments and possible improvements.

Ratiometric imaging of extracellular pH in Streptococcus mutans biofilms exposed to different flow velocities and saliva film thicknesses

Introduction: Fluid flow has a prominent influence on the metabolism of surface-attached biofilms. Dental biofilms are covered by a thin saliva film that flows at different rates in different locations under stimulated and unstimulated conditions. Methods:The present study employed pH ratiometry to study the impact of different flow velocities, saliva film thicknesses and saliva concentrations on microscale pH developments in Streptococcus mutans biofilms of different age. Results:While saliva flow at a velocity of 0.8 mm/min (unstimulated flow) had little impact on biofilm pH, stimulated flow (8 mm/min; 80 mm/min) affected vertical pH gradients in the biofilms and raised the average pH in 48-h biofilms, but not in 72-h and 168-h biofilms. The saliva film thickness had a strong impact on biofilm pH under both static and dynamic conditions. pH drops were significantly higher in biofilms exposed to a thin saliva film (≤ 50 µm) than a thick saliva film (> 50 µm). pH drops in the biofilms were also strongly dependent on the saliva concentration and thus the buffer capacity of the salivary medium. For 48-h and 72-h biofilms, but not for 168-h biofilms, pH drops in distinct microenvironments were more pronounced when the local biofilm thickness was high.