Jesus, C. | Search bioRxiv

bioRxiv2026

A room-temperature ⁸⁹Zr⁴⁺ radiolabelling strategy for small extracellular vesicles with enhanced plasma stability for PET Imaging

Both for diagnostic purposes and regenerative medicine, it is essential to develop advanced imaging platforms capable of tracking the biodistribution of small extracellular vesicles (sEVs), as current methods are limited by inadequate resolution and sensitivity. In this study, we introduce a novel labeling strategy utilizing the radioisotope zirconium-89 (89Zr), which boasts a half-life of 78.4 h and is cost-effective to produce. To achieve this, we designed a new chelator tailored for 89Zr4+ that offers enhanced stability compared to the conventional deferoxamine (DFO). This chelator forms a robust complex with 89Zr4+ at room temperature, suitable for sEV labeling for PET imaging applications. The radiolabeling process involved a two-step procedure: first, conjugation of the chelator to the sEVs, and second, radiolabeling with 89Zr4+. The resulting sEV-L1-Zr demonstrated a radiochemical yield of approximately 60% and maintained around 80% stability in plasma over seven days. Importantly, our modifications did not alter the morphology, surface protein composition, internal RNA content, or bioactivity of the sEVs. We successfully visualized sEVs at very low doses in the mouse heart following intravenous injection of sEV-L1-Zr. Additionally, ex vivo experiments using a Langendorff rat heart perfusion model confirmed targeted accumulation of the vesicles in cardiomyocytes as compared to other cells in the heart compartment. This approach provides a promising platform for sensitive and stable in vivo tracking of sEVs, advancing their application in both diagnostic imaging and regenerative therapies.

bioengineering↗

bioRxiv2025

Aging: an inevitable road toward gut microbiota pathoadaptation

Laboratory-raised mice live approximately seven times longer and healthier lives compared to their wild counterparts, due to a standardized healthy diet and limited exposure to environmental stressors1. Aging is associated with increased inflammation and microbial dysbiosis2-4. Collectively, these influence microbiota evolution and may contribute to the enrichment in pathobiont frequency observed in old age4. Alternatively, this increase could stem from a decline in colonization resistance5,6, creating favorable conditions for pathobiont invasion. Here, we sought to test whether aging in healthy, controlled conditions, could prevent the selection of age-associated pathobionts. We have followed the adaptive evolution of a commensal strain of Escherichia coli in the guts of mice of advanced age and found that it acquired several mutations common to bacteria colonizing young mice, which were absent in old animals. This, together with the increase in Akkermansia muciniphila in mice of advanced age, suggest healthy aging7,8. However, mutations acquired exclusively in the older were mainly pathoadaptive, tuning the metabolism to oxygen and iron availability, hypermotility, and biofilm formation. In summary, while the evolutionary signature in the guts of very old mice shows youth-like features that may be associated with longevity, the selection of pathoadaptive traits is magnified in very old age. While suggesting that a breach in colonization resistance is not needed to justify the abundance of age-associated pathobionts, our findings raise the question whether specialized bacteria, as opposing to generalists such as E. coli, will display the same ability to evolve pathoadaptive traits. HighlightsO_LIGut commensals face increasingly personalized selective pressures in the aging gut C_LIO_LIEven healthy aging selects for pathoadaptive traits in the gut microbiota C_LIO_LIE. coli s adaptive pattern better reflects the metabolome than microbiota composition C_LI In BriefPathobionts are often enriched in the microbiota of the elderly. Melo-Miranda et al. showed that irrespectively of limiting the opportunity for gut invasion, the strength of selection for pathoadaptation increases with aging. Yet, the gut environment of extreme ages seems to converge, highlighting the discontinuity of the aging process.

evolutionary biology↗