In some aspects, the disclosure pertains to injectable particles that contain at least one pH-altering agent that is configured to be released from the injectable particles in vivo, upon embolization of an intratumoral artery of a tumor with the injectable particles. In certain instances, the pH-altering agent may be a basic agent having a pH value of 7.5, a buffering agent having a pKa value of 7.6 or more, or both. Other aspects of the disclosure pertain to preloaded containers containing such injectable particles and methods of using such injectable particles.