Study of the Properties and Modification Mechanism of SBS-Modified Asphalt by Dry Process.

SBS (styrene-butadiene-styrene block copolymer) is a thermoplastic elastomer with properties most similar to rubber. SBS asphalt modifier is mainly composed of a styrene-butadiene-styrene block copolymer with a certain amount of additives and stabilizers. SBS-modified asphalt binder has always been the most commonly used pavement material both domestically and internationally. However, conventional wet-process SBS-modified asphalt binder requires manufacturers to produce it in advance and transport it to a mixing plant for blending. This has provided an opportunity for unscrupulous businesses to reduce the amount of SBS by adding other substances, allowing inferior asphalt binder to pass inspections undetected. At the same time, conventional wet-process SBS-modified asphalt tends to undergo phase separation and experience a decline in performance as the storage time increases. However, dry-process SBS-modified asphalt can be directly added at the mixing plant, effectively addressing the issues associated with conventional wet-process SBS-modified asphalt. It also helps to reduce environmental pollution to a certain extent. This study investigates the extraction process of dry-process SBS-modified asphalt binder. It clarifies the performance and modification mechanisms of two types of dry-process SBS-modified asphalt binder at different dosages through various testing methods, including basic indicators, rheological properties, infrared spectroscopy, and fluorescence microscopy. The results indicate that due to the incorporation of oil, crosslinker, solubilizer, and other substances into dry-process SBS modifier, there is a small amount of chemical reaction with asphalt in the melting process. The high- and low-temperature properties and fatigue properties of the two dry-process SBS-modified asphalt binders at a 7% dosage are close to wet SBS-modified asphalt binder at a 5% dosage.

Antifungal Effect of Vitamin D3 against Cryptococcus neoformans Coincides with Reduced Biofilm Formation, Compromised Cell Wall Integrity, and Increased Generation of Reactive Oxygen Species.

Cryptococcus neoformans is an invasive fungus that causes both acute and chronic infections, especially in immunocompromised patients. Owing to the increase in the prevalence of drug-resistant pathogenic fungi and the limitations of current treatment strategies, drug repositioning has become a feasible strategy to accelerate the development of new drugs. In this study, the minimum inhibitory concentration of vitamin D3 (VD3) against C. neoformans was found to be 0.4 mg/mL by broth microdilution assay. The antifungal activities of VD3 were further verified by solid dilution assays and "time-kill" curves. The results showed that VD3 reduced fungal cell adhesion and hydrophobicity and inhibited biofilm formation at various developmental stages, as confirmed by crystal violet staining and the 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide assay. Fluorescence staining of cellular components and a stress susceptibility assay indicated that VD3 compromised cell integrity. Reverse transcription quantitative PCR demonstrated that VD3 treatment upregulated the expression of fungal genes related to cell wall synthesis (i.e., CDA3, CHS3, FKS1, and AGS1). Moreover, VD3 enhanced cell membrane permeability and caused the accumulation of intracellular reactive oxygen species. Finally, VD3 significantly reduced the tissue fungal burden and prolonged the survival of Galleria mellonella larvae infected with C. neoformans. These results showed that VD3 could exert significant antifungal activities both in vitro and in vivo, demonstrating its potential application in the treatment of cryptococcal infections.

Riboflavin Targets the Cellular Metabolic and Ribosomal Pathways of Candida albicans In Vitro and Exhibits Efficacy against Oropharyngeal Candidiasis.

Oropharyngeal candidiasis (OPC), which has a high incidence in immunocompromised and denture stomatitis patients, is commonly caused by Candida albicans infection and in some cases develops into disseminated candidiasis throughout the throat and esophagus, resulting in high mortality. New drugs are needed to combat OPC because of the limited treatment options currently available and increasing resistance to existing drugs. Here, we confirmed that riboflavin (RF), a cofactor of flavin adenine mononucleotide and flavin adenine dinucleotide, has broad-spectrum anti-Candida activity. The formation of C. albicans hyphae and biofilm was inhibited by RF. Mechanistically, RF disrupted membrane and cell wall integrity, as well as promoting reactive oxygen species and pyruvate accumulation. Furthermore, RF targeted multiple essential pathways via functional disruption of thiamine and RF metabolic pathways, central carbon metabolism, and ribosome metabolism. Similar to the results in vitro, the inhibitory effect of RF on C. albicans hyphae was confirmed in a mouse model of OPC. Moreover, after 5 consecutive days of intraperitoneal injection, RF exhibited therapeutic efficacy, as demonstrated by phenotype investigation, the fungal burden, and histopathological analysis. These findings revealed that RF exerts a multifaceted anti-Candida effect and has potential benefits in the treatment of OPC. IMPORTANCE Candida species are common pathogens in fungal infections, causing mucosal infection and invasive infection in immunodeficient patients. Given the limited classes of drugs and resistance to these drugs, new antifungal agents need to be developed. Drug repurposing is a potential method for antifungal drug development. This study demonstrated that riboflavin (RF) exhibited broad-spectrum anti-Candida activity. RF affected multiple targets involving the membrane and cell wall integrity, the accumulation of reactive oxygen species and pyruvate, and the altered metabolic pathways in C. albicans. Moreover, RF exhibited efficacy in the treatment of C. albicans in an oropharyngeal candidiasis mouse model. Taken together, the antifungal activity and the promising clinical application of RF were highlighted.

Antifungal activity of vitamin D3 against Candida albicans in vitro and in vivo.

The incidence of intra-abdominal candidiasis (IAC), characterized by high morbidity and mortality, has become a serious concern. The limitations of current antifungal drugs on the market underscores the importance of the development of novel antifungal agents. In the present study, the antifungal activity of vitamin D3 (VD3) against various Candida species was investigated. In vitro, the broth microdilution method and solid plate assay confirmed that VD3 inhibited the growth of Candida spp. in a broad-spectrum, dose-dependent manner. VD3 also had a significant antifungal effect on the initiation, development, and maturation phases of biofilm formation in Candida albicans. The mechanism of VD3 action was explored by transcriptomics and reverse transcription quantitative PCR (RT-qPCR) analysis, and showed that VD3 affects ribosome biogenesis, coenzyme metabolism, and carbon metabolism. These results suggested that VD3 may have multitarget effects against C. albicans. In the murine IAC model, VD3 reduced the fungal burden in the liver, kidneys, and small intestine. Further histopathological analysis and quantification of plasma cytokine levels confirmed that VD3 treatment significantly decreased the infiltration of inflammatory cells and the levels of plasma interferon (IFN)-γ and tumor necrosis factor (TNF)-α. Taken together, these findings suggest a new antifungal mechanism for VD3 and indicate that VD3 could be an effective therapeutic agent for use in IAC treatment.

The promise of endogenous and exogenous riboflavin in anti-infection.

To resolve the growing problem of drug resistance in the treatment of bacterial and fungal pathogens, specific cellular targets and pathways can be used as targets for new antimicrobial agents. Endogenous riboflavin biosynthesis is a conserved pathway that exists in most bacteria and fungi. In this review, the roles of endogenous and exogenous riboflavin in infectious disease as well as several antibacterial agents, which act as analogues of the riboflavin biosynthesis pathway, are summarized. In addition, the effects of exogenous riboflavin on immune cells, cytokines, and heat shock proteins are described. Moreover, the immune response of endogenous riboflavin metabolites in infectious diseases, recognized by MHC-related protein-1, and then presented to mucosal associated invariant T cells, is highlighted. This information will provide a strategy to identify novel drug targets as well as highlight the possible clinical use of riboflavin.