Three-Dimensional Printing Chitosan-Based Bolus Used for Radiotherapy

A bolus is a kind of tissue equivalent material used in radiotherapy for treating superficial lesions. Despite the availability of various commercial boluses, it is hard for them to form full contact with the irregular surface of patients' skin, such as the scalp, nose, and ear, resulting in air gaps and leading to a discrepancy between the delivered dose and planned dose. To solve this problem, we provided a photocurable bioink created from chitosan (CHI) for digital light processing (DLP) three-dimensional (3D) printing the bolus in radiotherapy application. The chitosan-based bioink (CHI-MA) was obtained by a methacrylation process using methacrylic anhydride (MA). Photosensitive crosslinkers with different molecular weights were introduced into the bioink. The photocuring efficiency and mechanical properties of CHI-MA hydrogels can be well modulated by varying the crosslinkers. This CHI-MA bioink allowed us to create complex structures with reliable biocompatibility, good flexibility, and excellent structural stability. Furthermore, the nose bolus processed by 3D printing this bioink proved to be a good fit for the nose model and showed a desirable radiotherapy effect. This suggests that DLP 3D printing of the CHI-MA bioink would be a promising approach to obtain the customized bolus in the application of radiotherapy.