The rationale behind the design stems from a growing recognition that secondary injury, rather than the initial mechanical blow, determines how much function is ultimately lost. Within hours of trauma, the lesion site becomes flooded with reactive oxygen species, mitochondrial membranes collapse, and immune cells shift into a destructive inflammatory mode. Mitochondrial dysfunction sits at the center of this cascade. Damaged mitochondria leak superoxide, which activates the NLRP3 inflammasome, drives gasdermin D-associated pyroptotic signaling, and pushes microglia and macrophages into a glycolysis-dominant, pro-inflammatory state. Because these processes feed one another, single-target drugs have consistently underperformed in preclinical models.

The team’s solution was to combine two natural compounds with complementary bioactivities inside a single responsive vehicle. Astaxanthin, a carotenoid with potent mitochondrial-protective and antioxidant properties, was encapsulated within zeolitic imidazolate framework-8, a pH-sensitive metal-organic framework that degrades under the pathological acidosis characteristic of injured tissue. Myricetin, a flavonoid known to regulate mitochondrial homeostasis and suppress inflammasome activation, was then coordinated with zinc ions to form a metal-phenolic outer shell. The result is a particle of roughly 172 nanometers in hydrodynamic diameter that carries both a protected drug reservoir and a redox-active surface interface.

Characterization confirmed the architecture in detail. Transmission electron microscopy revealed polyhedral particles with roughened surfaces after coating, while elemental mapping showed carbon, nitrogen, oxygen, and zinc distributed throughout. X-ray diffraction demonstrated that the ZIF-8 crystalline framework survived shell formation, and X-ray photoelectron spectroscopy verified the surface chemical states. Drug loading was quantified by high-performance liquid chromatography at 7.28 weight percent astaxanthin for the uncoated core and 1.47 weight percent for the full construct, with myricetin loading of approximately 12.03 percent. Release experiments showed the platform’s defining feature: at physiological pH 7.4, cargo liberation remained limited, but acidic conditions and hydrogen peroxide dramatically accelerated release of both astaxanthin and myricetin, with combined acidic and oxidative conditions releasing 66.9 percent of myricetin within 72 hours.

The zinc-myricetin shell proved to be far more than a passive coating. Electron paramagnetic resonance showed that the coated particles quenched superoxide and hydroxyl radicals more effectively than the uncoated core, and colorimetric assays confirmed concentration-dependent scavenging of ABTS, DPPH, hydrogen peroxide, and hydroxyl radicals. Zinc release, measured by ICP-MS, rose from about 9 micromolar at neutral pH to nearly 25 micromolar under combined acidic and oxidative stimulation, a range that primary hippocampal neurons tolerated without significant viability loss. The authors are careful to note that without isolated shell-only controls, the individual contributions of zinc coordination and myricetin chemistry cannot be formally separated, and the data do not establish true synergy between components.

In cell studies, the nanoplatform reshaped the behavior of activated microglia. When BV2 cells were stimulated with lipopolysaccharide, mitochondrial superoxide surged, membrane potential collapsed, and glycolytic activity climbed. Treatment with the full nanoparticle suppressed these changes more effectively than free drugs or the uncoated core, restoring respiratory parameters measured by Seahorse extracellular flux analysis and shifting the cells away from a CD68-positive, CD86-positive inflammatory phenotype toward a CD206-positive reparative one. Levels of NLRP3, gasdermin D, and interleukin-1 beta fell markedly, though the authors emphasize that total gasdermin D abundance does not prove inhibition of pyroptotic cell death itself, since the cleaved pore-forming fragment was not assessed.

Neuronal cells benefited in parallel. In PC12 cells exposed to hydrogen peroxide, the nanoparticles entered cells progressively over 36 hours, reduced cytosolic and mitochondrial reactive oxygen species, restored membrane potential, and repaired mitochondrial ultrastructure as visualized by electron microscopy. Bioenergetics recovered too: basal respiration, ATP-linked respiration, maximal respiration, spare respiratory capacity, and cellular ATP all rebounded. The treatment also rebalanced mitochondrial dynamics, restoring the fusion proteins MFN1 and MFN2 and the deacetylase SIRT3 while suppressing the fission protein DRP1. In primary hippocampal neurons, the platform improved survival and increased both the number and total length of neurites after oxidative challenge, suggesting preservation of growth-associated phenotypes permissive for structural repair.

The in vivo results tied the cellular story to functional recovery. Locally injected into the lesion immediately after clip-compression injury at the T8 segment, the nanoparticles prolonged early astaxanthin retention in tissue without progressive zinc accumulation through day seven. Chemiluminescence imaging on day three showed the strongest reduction in lesion oxidative burden among all treatment groups. By day seven, flow cytometry of dissociated tissue revealed that resident microglia, which outnumbered infiltrating macrophage-lineage cells roughly seventeen-fold, had shifted away from CD86-positive inflammatory activation toward CD206-positive reparative markers. Caspase-3 signals fell, NeuN-positive neurons were preserved, and NLRP3 and gasdermin D signals in CD68-positive cells declined. Transcriptome sequencing independently supported these observations, with enrichment changes in NOD-like receptor signaling, IL-17 signaling, and extracellular matrix-receptor interaction pathways, validated for selected genes by quantitative PCR.

Eight weeks after injury, the structural gains translated into measurable function. Treated animals showed higher Basso, Beattie, and Bresnahan locomotor scores that improved progressively over the observation period, along with larger motor evoked potential amplitudes, shorter response latencies, preserved muscle wet weight and fiber area, stronger electromyographic activity, and more regular gait patterns. Histology revealed denser Nissl-positive neurons, greater Luxol fast blue-positive myelin, more myelinated axons with reduced g-ratios on electron microscopy, and constructive remodeling of laminin and fibronectin deposition at the lesion. Major organ histology, blood counts, and serum chemistry showed no treatment-associated abnormalities within the eight-week window, though the authors caution that long-term degradation, biodistribution, and clearance of the zinc-containing framework remain unresolved questions for translation.

The study’s most important contribution may be conceptual rather than a specific therapy. Rather than targeting a single pathological event, the nano-biointerface treats the lesion as an interconnected system in which redox balance, mitochondrial bioenergetics, immune metabolism, and inflammatory signaling must be remodeled together. The authors themselves are notably restrained about causality: mitochondrial restoration is presented as a convergent treatment-associated feature, not a proven upstream driver, and no formal dose-ranging or component-perturbation experiments were performed. Still, the demonstration that a single responsive material can coordinate mitochondrial-immune crosstalk across cell types and produce durable functional recovery offers a compelling template for microenvironment-oriented spinal cord repair, and a reminder that the next generation of neuroregenerative biomaterials may need to be as dynamic as the injuries they confront.

Subject of Research: A lesion-responsive ZIF-8/zinc-myricetin nano-biointerface that remodels mitochondrial-immune crosstalk for spinal cord injury repair

Article Title: A lesion-responsive ZIF-8/zinc–myricetin nano-biointerface remodels mitochondrial–immune crosstalk for spinal cord repair

Article References: Zhao, Y., Xia, Z., Xie, T., Liu, R., Liu, S., Luo, R., Wang, S., Huang, D., Yan, L., Hu, H., & Ju, C. (2026). A lesion-responsive ZIF-8/zinc–myricetin nano-biointerface remodels mitochondrial–immune crosstalk for spinal cord repair. Materials Today Bio, 41, Article 103683. https://doi.org/10.1016/j.mtbio.2026.103683

Image Credits: AI Generated

DOI: 10.1016/j.mtbio.2026.103683

Keywords: spinal cord injury, nanoparticles, ZIF-8, astaxanthin, myricetin, mitochondria, microglia, NLRP3 inflammasome, oxidative stress, metal-organic framework, neuroinflammation, biomaterials

PFAS compounds, often called forever chemicals because of their extraordinary persistence in the environment and the human body, have been used for decades in nonstick coatings, water repellents, and industrial processes. When the older compounds PFOA and PFOS were phased out following widespread reports of health hazards, PFNA and its chemical cousin PFDA were adopted as primary substitutes because of their similar physicochemical properties. These replacements are now routinely detected in surface waters, sediments, and even Arctic soils, and they rank among the most commonly found PFAS congeners in human serum samples worldwide.

The Zhejiang University team, led by Kean Lu, Zhenyan Cui, Yihua Wu, and Dajing Xia, set out to address a critical gap in environmental health science. Most previous studies of PFAS toxicity employed doses far exceeding the levels that humans actually encounter in daily life. Because epidemiological research has already linked PFAS exposure to elevated risk of inflammatory bowel disease, or IBD, and because IBD incidence is rising rapidly in newly industrialized regions, understanding how environmentally realistic exposures translate into gut inflammation has become a pressing scientific priority.

The researchers compared three PFAS compounds, PFOA, PFNA, and PFDA, in mouse peritoneal macrophages, the immune cells that act as central effectors in the inflammatory cascade of IBD. The results were strikingly compound-specific. PFOA showed no significant effect on the inflammatory cytokines IL-1β and IL-18 across the entire tested concentration range. PFDA produced a more general increase in inflammatory signaling at higher concentrations. But PFNA stood out: at remarkably low concentrations of 0.1 to 1 micromolar, it drove dose-dependent increases in both IL-1β and IL-18, the signature effector cytokines of the NLRP3 inflammasome, a multiprotein complex widely recognized as a central driver of IBD progression.

Delving into the mechanism, the team discovered that low-dose PFNA selectively activated the noncanonical NLRP3 inflammasome pathway, which depends on the enzyme caspase-11 rather than the more commonly studied caspase-1. Within the low concentration range, PFNA dose-dependently increased caspase-11 expression and triggered the downstream cascade: upregulation of NLRP3, cleavage of caspase-1, and activation of gasdermin D, the protein that forms pores in cell membranes during inflammatory cell death. Notably, at high concentrations PFNA shifted behavior entirely, activating caspase-8 and caspase-3 and pushing cells toward apoptosis instead, a biphasic dose-response pattern the authors suggest may reflect crosstalk between inflammatory and apoptotic caspases or a hormetic effect of PFAS compounds.

To confirm that caspase-11 was genuinely the upstream driver, the researchers silenced the caspase-11 gene with small interfering RNAs. Knockdown significantly suppressed the entire PFNA-induced inflammatory program, reducing NLRP3, cleaved caspase-1, gasdermin D, and the mature forms of IL-1β and IL-18, while restoring cell viability. A pancaspase inhibitor, Z-VAD-FMK, produced similar protection. Molecular docking simulations then suggested a physical basis for the interaction: PFNA appeared to bind within the pro-caspase-11 protein, forming a hydrogen bond with the arginine residue ARG-360, with a calculated binding energy of −8.40 kilocalories per mole. Molecular dynamics simulations over 100 nanoseconds showed the PFNA–caspase-11 complex remained structurally stable, and more stable than the corresponding PFNA–caspase-1 complex, supporting a preferential association with caspase-11. The authors caution, however, that these computational findings are preliminary and require direct experimental validation.

The relevance to human health hinges on dose. Population studies indicate that PFAS concentrations in human serum range from 20 nanomolar to 215 micromolar, with PFNA levels reaching up to 352 nanomolar, squarely within the range where the study observed maximal inflammasome activation. Even more alarming, recent work published in Nature Microbiology demonstrated that human gut bacteria efficiently bioaccumulate PFNA, achieving intracellular concentrations 25- to 60-fold higher than environmental exposure levels. This suggests the gut microbiome may act as a reservoir, concentrating the chemical locally and enhancing its bioavailability to the intestinal lining, meaning that local gut concentrations could substantially exceed both environmental background and serum levels.

To test the findings in living animals, the team established a chronic colitis model in mice using three cycles of DSS treatment, a protocol that mimics the relapsing-remitting course of human IBD. Mice received PFNA orally at 1.01 micrograms per kilogram per day for 24 days, a dose derived from the tolerable daily intake proposed in human risk assessments. The results were unambiguous. PFNA-exposed mice showed significantly shortened colons, extensive inflammatory cell infiltration, crypt loss, and elevated histopathological scores. Colon tissue displayed upregulated pro-caspase-11, cleaved caspase-11, and the full downstream NLRP3 pathway, while serum levels of IL-1β and IL-18 rose sharply, confirming systemic inflammasome-mediated cytokine release. Immunofluorescence revealed increased numbers of F4/80-positive macrophages carrying active cleaved caspase-1, directly implicating these cells in the pathology.

Crucially, the study also identified a potential intervention. Myricetin, a natural flavonoid found in berries, tea, and various fruits and vegetables, was administered to a subset of mice starting on day 9, a delayed protocol designed to model how patients begin treatment after disease onset. Myricetin treatment significantly inhibited PFNA-induced colon shortening, ameliorated tissue damage, reduced inflammatory infiltration, and lowered serum cytokine levels. At the molecular level, it suppressed caspase-11 expression and cleavage along with the entire downstream NLRP3 cascade. In vitro, pretreating macrophages with myricetin before PFNA exposure similarly restored cell viability and dampened inflammatory signaling. The authors note that myricetin has previously been shown to inhibit NLRP3 activation through modulation of ASC and NLRP3 ubiquitination, and to suppress upstream NF-κB signaling and oxidative stress, though the present data cannot yet distinguish whether it directly targets caspase-11 or acts through these upstream pathways.

The researchers frame their findings within an adverse outcome pathway-like framework, linking a molecular initiating event, the interaction of PFNA with caspase-11, through the key event of NLRP3 inflammasome activation, to the adverse outcome of aggravated intestinal inflammation. This structure provides a template for investigating other PFAS members, whose mechanisms appear to differ: the team’s earlier work showed that PFDA exacerbates IBD through the cGAS/STING/NF-κB axis instead. The study does carry limitations. Only male mice were included, so conclusions may not generalize to females given known sex differences in PFAS toxicokinetics, and antibody limitations prevented direct visualization of caspase-11 localization in colon tissue. Nevertheless, by demonstrating that a substitute forever chemical can inflame the gut at doses people actually encounter, and by pointing to a dietary flavonoid as a possible shield, the work adds urgency to PFAS risk assessment and opens a concrete avenue for protecting the millions of people living with inflammatory bowel disease in an increasingly contaminated world.

Subject of Research: How low-dose PFNA exposure exacerbates intestinal inflammation through caspase-11-dependent noncanonical NLRP3 inflammasome activation in macrophages

Article Title: Low-dose PFNA exposure exacerbates intestinal inflammation via caspase-11-dependent noncanonical NLRP3 inflammasome activation in macrophages

Article References: Lu, K., Cui, Z., Fei, X., Zhang, J., Fang, S., Wang, Y., Chen, Y., Wu, Y., & Xia, D. (2026). Low-dose PFNA exposure exacerbates intestinal inflammation via caspase-11-dependent noncanonical NLRP3 inflammasome activation in macrophages. Journal of Advanced Research. https://doi.org/10.1016/j.jare.2026.09.005

Image Credits: AI Generated

DOI: 10.1016/j.jare.2026.09.005

Keywords: PFAS, PFNA, forever chemicals, inflammatory bowel disease, NLRP3 inflammasome, caspase-11, macrophages, myricetin, intestinal inflammation, environmental toxicology, gut microbiome, colitis