Provided herein are delivery particle systems (XDP) useful for the delivery of payloads of any type. In some embodiments, a XDP particle system with tropism for target cells of interest is used to deliver CRISPR/Cas polypeptides (e.g., CasX proteins) and guide nucleic acids (gNA), for the modification of nucleic acids in target cells. Also provided are methods of making and using such XDP to modify the nucleic acids in such cells.