Anti-migratory chitosan/BaSO4 markers with hydration in situ for long-term multimodal breast tissue imaging

Tissue markers can effectively indicate diseased sites within the body. However, conventional metal-based markers are severely limited by imaging artifacts and high migration risks resulting from mechanical mismatch with soft tissues. Herein, we developed a composite xerogel system composed of chitosan and BaSO 4 particles. Through comprehensive screening, 20–40 wt% BaSO 4 was established as the optimal functional window, within which 40BS-C (a composite xerogel containing 40 wt% BaSO 4 and 60 wt% chitosan) was identified as the optimal formulation for balancing multimodal micro-CT/ultrasound (US)/magnetic resonance imaging (MRI) and mechanical compliance. Upon hydration equilibrium, the compressive modulus of approximately 10 MPa was significantly lower than that of metallic or other rigid materials. Favorable imaging capabilities were shown in both micro-CT and US in vitro . Furthermore, volume swelling and the formation of a moderately thick fibrous capsule provided effective physical anchoring, resulting in significantly lower relative displacement of the markers (4.4–4.6 mm) compared to the metallic counterparts (6.9 mm). A 6-month in vivo animal study confirmed that the markers exhibited favorable multimodal imaging stability (with a micro-CT signal-to-background ratio of 5.43 for the optimal 40BS-C, and an overall US dimensional deviation < 5%) and biocompatibility compared with clinical titanium markers. In summary, this optimized multimodal and anti-migratory marker system provides a reliable strategy for precise lesion localization, demonstrating promising potential for clinical translation.