Multifunctional PLGA microfibrous rings enable MR imaging-guided tumor chemotherapy and metastasis inhibition through prevention of circulating tumor cell shedding

•PLGA microfibrous rings can be formed by fiber homogenization in salt solution.•PLGA fibrous rings can be functionalized as a theranostic platform.•The fibrous rings enable MR imaging-guided tumor therapy and metastasis inhibition.•The fibrous rings can anchor tumor tissues to prevent shedding of CTCs.•The platform with a slow drug release profile enables a long-lasting tumor therapy.