Advancing Open Science

Background: Chlorine dioxide (ClO₂), formulated as an aqueous solution (CDS), has been proposed as a therapeutic agent, yet its classification among oxidizing compounds is frequently confounded with chemically distinct species—sodium chlorite (NaClO₂) and sodium hypochlorite (NaOCl). Objective: This study aimed to synthesize the physicochemical, mechanistic and cellular basis of ClO₂ action and to delineate the distinctions between ClO₂ and related oxidants, with explicit separation of established data from hypothesized data. Methods: The methodology includes a narrative synthesis of electrochemical data, primary toxicological and clinical literature (PubMed) and the redox-biology literature on low-dose oxidant signaling. Results: ClO₂ is a neutral free radical that acts via one-electron transfer (E°′ = +0.95 V vs. SHE for the half-reaction ClO₂ + e⁻ → ClO₂⁻, essentially pH-independent over pH 4–8, pH-independent) without chlorination. Its antimicrobial action is attributable to oxidation of thiol-dependent enzymes and membrane constituents and to the inhibition of bacterial respiratory metabolism; host-cell sparing is consistent with differential glutathione-dependent buffering. Controlled human ingestion studies at low concentrations report a favorable short-term safety profile; conversely, the principal metabolite (chlorite) is associated with documented developmental toxicity in animals and regulatory caution by EPA/WHO. Low-dose ClO₂ exposure is hypothesized—but not yet directly demonstrated—to elicit dose-dependent adaptive redox responses and redox-regulatory modulation. Conclusions: The one-electron, non-chlorinating chemistry of ClO₂ provides a coherent mechanistic framework. The translation of this framework into clinical application requires prospective trials and direct mechanistic measurement, ideally conducted by independent investigators. The following mechanisms are hypothesized and have not yet been directly demonstrated in vivo: modulation of oxidative phosphorylation, mitochondrial oxygenation, and associated redox-regulatory signaling. Reported antimicrobial efficacy typically occurs in the low-ppm range (0.1–5 ppm), whereas adverse effects on mammalian cells in the reviewed literature are reported at concentrations at least one order of magnitude higher; direct head-to-head cytotoxicity comparisons remain scarce and are identified as a priority for future work. This differential thiol buffering—in particular, the higher glutathione content of many mammalian cells relative to many pathogens—has been proposed as a contributing basis for host-cell sparing; direct quantitative confirmation in vivo is not yet available. Bacterial species possess their own thiol-based defense systems (e.g., mycothiol in actinomycetes, bacillithiol in Firmicutes), and the interplay between ClO₂ and these systems requires further investigation.

Neglected tropical diseases (NTDs) caused by Leishmania and Schistosoma species continue to impose a significant health burden in endemic regions, largely due to limited therapeutic options, drug resistance, and incomplete understanding of parasite biology at the molecular level. A major restriction in the development of targeted interventions is the structural inaccessibility of parasite membrane-associated proteins, which are central to host invasion, nutrient transport, immune evasion, and survival. Recent advances in cryogenic electron microscopy (cryo-EM) have expanded the structural biology toolkit available for studying difficult parasite proteins, particularly large and membrane-associated macromolecular assemblies. However, experimentally resolved cryo-EM structures remain limited for many of the Leishmania and Schistosoma targets relevant to therapeutic and vaccine development. This review therefore distinguishes experimentally determined structures from partial structural information and computational models and examines how potential cryo-EM approaches may address unresolved structural questions. We discuss current structural knowledge of selected parasite targets, approaches for recombinant expression and membrane-protein stabilization, membrane-mimetic systems for structural characterization, and computational methods that complement experimental structural biology. We further examine how experimentally supported structural information, complemented by computational predictions where appropriate, could contribute to structure-guided drug discovery, vaccine design, and targeted nanomedicine. At present, however, the direct translation of parasite structural information into rational nanotherapeutic design remains limited. Key gaps include the scarcity of experimentally resolved parasite membrane protein structures, challenges in their expression and structural characterization, and limited integration of structural biology with nanoparticle engineering. Resolving these gaps may improve the prospects for structure-informed therapeutic and nanomedicine applications against leishmaniasis, schistosomiasis, and other NTDs.

Animal material culture is most often discussed in relation to tool use and foraging, while non-foraging object use remains poorly documented in many taxa. This study reports opportunistic observations of a novel object-directed behavior in the critically endangered pygmy raccoon (Procyon pygmaeus), an island-endemic species restricted to Cozumel, Mexico. During fieldwork on tourism effects between January and February 2026, researchers used direct observation, site assessment, photography, videography, and interviews to document raccoon behavior at several sites. At one beach club, two juvenile female siblings were observed retrieving paper waste, dipping it in water, rolling and compacting it with sand, and using the resulting balls in play. One juvenile first performed the full sequence while the other observed and then attempted the behavior; the second juvenile later completed the sequence independently after her sister had been removed from the site. However, at a comparable tourism site with juvenile raccoons and access to paper and water, this behavior was not observed. These observations provide potential evidence of socially mediated material engagement in pygmy raccoons. The findings expand the known behavioral repertoire of the species and support continued field-based behavioral monitoring, especially where tourism, waste exposure, and juvenile development overlap.

Background: Environmental surface contamination in early childhood education settings has been recognized as a potential source of exposure to microorganisms. However, the available evidence on bacterial contamination in these environments remains limited, methodologically heterogeneous, and difficult to interpret from an epidemiological perspective. Methods: A scoping review was conducted following Joanna Briggs Institute methodology and reported according to the PRISMA-ScR guidelines. Searches were performed in PubMed/MEDLINE, Embase, Scopus, Web of Science, CINAHL, LILACS, and gray literature sources. Studies reporting bacterial contamination of environmental surfaces and fomites in early childhood education settings were included. Data were extracted and synthesized using descriptive and thematic approaches. Results: Nine studies met the inclusion criteria. Most employed cross-sectional designs and showed substantial variability in sampling strategies, microbiological methods, and outcome definitions. Frequently identified microorganisms included Staphylococcus aureus (including methicillin-resistant strains [MRSA]), Bacillus spp., Pseudomonas spp., Klebsiella spp., Enterococcus spp., and Escherichia coli. Bacterial contamination was consistently reported on high-touch surfaces such as toys, tables, doorknobs, and shared objects. However, most studies did not distinguish between microbial detection, viability, and transmission potential, limiting epidemiological interpretation. Evidence regarding antimicrobial resistance was restricted to a small number of studies and remained fragmented. Conclusions: Evidence on the bacterial contamination of surfaces and fomites in early childhood education settings is scarce, heterogeneous, and predominantly descriptive. Current knowledge is largely limited to documenting the presence of microorganisms, with insufficient evidence to determine their viability or role in transmission processes. Future studies should adopt standardized methodologies and integrate environmental, microbiological, and epidemiological measures to strengthen the understanding of contamination patterns and their public health relevance.

Cellulose fibers are abundant, renewable biopolymers with significant potential to replace petroleum-based materials, yet their high flammability limits their use in fire-sensitive applications such as protective packaging, electrical insulation, and interior building materials. In this study, softwood kraft fibers were phosphorylated without solvent or chemical pre-treatment using a molten urea/phosphoric acid system at 160 °C for 3 h (molar ratio of 6:3:1 for urea, H₃PO₄, and cellulose anhydroglucose units). After water quenching, disintegration, and washing, the modified fibers were blended with unmodified kraft fibers at various ratios (0, 20, 40, 60, 80, and 100 wt.%) to prepare standard paper handsheets (85–90 g/m²) dried at 120 °C. Fiber characterization confirmed successful phosphate ester grafting, yielding a phosphorus content of 5.9%, a nitrogen content of 8.7%, and a total charge increase from 92 to 4676 mmol/kg, while preserving fiber length (decreasing slightly from 2.04 to 1.93 mm). Thermogravimetric analysis revealed enhanced thermal stability, generating a residual char mass of 31.12 wt.% at 900 °C compared to 6.9 wt.% for untreated fibers. Handsheet apparent density varied from 0.260 g/cm³ for KFP60 to 0.316 g/cm³ for KFP100. Inter-fiber phosphate crosslinking during hot drying significantly improved mechanical performance, increasing maximum load from 10.27 N to 42.29 N and Young’s modulus from 39.77 to 99.78 MPa. Vertical flammability tests demonstrated that handsheets containing ≥60 wt.% phosphorylated fibers preserved their structural integrity after 30 s of flame exposure, whereas untreated handsheets burned completely. These results highlight phosphorylation as a scalable, halogen-free, and effective strategy for producing mechanically robust, fire-resistant cellulose materials.

The growing global demand for particleboards has generated large quantities of waste in recent years. This waste mainly arises from manufacturing processes, furniture industry offcuts, and end-of-life disposal. In response to waste management challenges, recycling and reuse technologies have advanced significantly. In this context, this study evaluates the feasibility of producing new particleboards using recycled particles obtained from laminated particleboard waste. Recycled particles were treated with hot water, oxalic acid, and a combination of both, and the most effective treatment was selected for panel production. Hot water treatment was insufficient to remove the cured UF resin and promote particle separation, whereas oxalic acid successfully achieved both. Three-layer panels were then manufactured using oxalic acid-treated recycled particles at incorporation levels of 0%, 25%, 50%, 75%, and 100% in the core layer. The average density, vertical density profile, and physical and mechanical properties, as well as the formaldehyde emissions, were assessed. The results showed that the inclusion of recycled particles did not significantly impact the average density or the vertical density profiles of the panels. Thickness swelling and water absorption after 24 h immersion were similar across all panels, indicating good dimensional stability. Internal bond (IB) strength showed no consistent trend with increasing recycled particle content, and panels with 75% recycled particles achieved the highest IB strength (0.48 MPa). In contrast, bending properties decreased when the proportion of recycled particles exceeded 25%. All panels satisfied the requirements of the LD-2 Grade for low-density particleboards specified by the ANSI A208.1-2022 standard. An increase in formaldehyde emissions was observed in panels containing more than 25% recycled particles compared to the control panels. These findings indicate that particleboards can incorporate up to 75% recycled particles in the core, while maintaining physical and mechanical properties comparable to those of the control panels.