Germanium-embedded fabrics attenuate oxidative stress and modulate cytokine activity in a progressive in vitro model...

Germanium-embedded fabrics (GEF) have been proposed as bioactive wearable materials capable to modulate inflammatory and oxidative processes through the thermally induced emission of mid- and far-infrared (MIR/FIR) radiation and the generation of negative air ions (NAIs). However, the events governing the inflammatory crosstalk between endothelial and monocytic cells under GEF exposure, particularly regarding the regulation of adhesion molecules like ICAM-1, as well as overall cytokine secretion and NOx production, has been never investigated. This study systematically investigated the effects of GEF on endothelial and monocytic cells in three sequentially in vitro culture models assembled to simulate endothelial dysfunction: (i) conventional 2D monolayer single cultures, (ii) 2D static co-cultures, and (iii) a novel biofabricated 3D dynamic perfusion co-culture system, not previously described in the literature. Human umbilical vein endothelial cells (HUVECs) and monocytic THP-1 cells were stimulated with tumour necrosis factor-alpha (TNF-α; 10 ng/mL) and lipopolysaccharide (LPS; 10 ng/mL), respectively, for 3 days to generate reproducible inflammatory baselines prior to GEF exposure (NAI measured at 1,420 ± 145 ions/cm³). In single monolayer cultures, GEF did not compromise cell viability, and significantly reduced intracellular reactive oxygen species (ROS) in HUVECs by 37% at day 7 (p < 0.01) and modulated cytokine secretion, decreasing interleukin-6 (IL-6) release by 30% and enhancing IL-2 production in THP-1 cells by 4.3-fold (p < 0.05). In 2D static co-cultures, GEF consistently reduced endothelial ROS and exhibited biphasic regulation of intercellular adhesion molecule-1 (ICAM-1) expression, with early upregulation followed by significant attenuation at later time points. Cytokine profiling revealed a transient, temporally balanced modulation of both pro-inflammatory (IL-6, IL-8) and anti-inflammatory (IL-10, IL-4) mediators. In the 3D perfused co-culture system, encompassing HUVECs and THP-1 cells bioprinted within methacrylated collagen (ColMA) hydrogels, GEF preserved high cell viability, limited ROS accumulation, and promoted nitric oxide (NO) production, most prominently at day 7. Cytokine profiling in the 3D model confirmed suppression of pro-inflammatory mediators at concentrations orders of magnitude lower than those observed in equivalent 2D co-cultures. GEF exerts a context-dependent, biphasic modulatory action on endothelial inflammation: attenuating oxidative stress and endothelial activation rather than effecting simple immunosuppression. The convergent antioxidant and cytokine-modulating effects across progressively biomimetic culture models support the potential of GEF as a non-invasive, biophysical strategy for the management of vascular inflammatory conditions.