Biomaterials tools to modulate the tumour microenvironment in immunotherapy

Cancer immunotherapies, such as immune checkpoint blockade and chimeric antigen receptor (CAR) T cell therapy, have transformed clinical oncology. However, limited patient response rates and immune-related adverse events remain major clinical challenges. The immunosuppressive tumour microenvironment (TME) has a key role in the response to immunotherapy. The TME of solid tumours can prevent infiltration and negatively affect the activity of immune cells. The immunosuppressive features of the TME can be modulated using biomaterials-based tools that target, respond to and modulate the physicochemical properties of the TME, including hypoxia, acidity, high levels of reactive oxygen species, a dense extracellular matrix and abnormal vasculature. In this Review, we introduce hallmarks of the TME and discuss biomaterials and nanomedicine technologies that can regulate the TME of solid tumours to improve the efficacy of different types of immunotherapy. We outline the remaining challenges in the clinical translation of TME-modulating biomaterials tools and conclude by envisioning future milestones in this field. The tumour microenvironment of solid tumours can prevent immune cell infiltration and negatively affect the efficacy of immunotherapies. This Review discusses the design of biomaterials-based tools that can modulate the physicochemical features of the tumour microenvironment to assist immunotherapies.