Abstract: Provided herein a single-domain antibodies (sdAbs) that bind to voltage-gated sodium channel (Nav)1.4 or Nav1.5 and polynucleotides encoding the sdAb. Also provided herein are expression cassettes, vectors and host cells including polynucleotides N encoding the sdAb, and pharmaceutical composition including the sdAb, and methods of use thereof. The methods include the detection and/or capture Nav1.4 or Nav1.5 in a sample, the detection of a disease or condition in a subject, and the treatment of cardiac arrhythmia, myotonia, sudden cardiac death syndrome or cancer in a subject using sdAbs that bind Nav 1.4 or Nav 1.5.

Abstract: This document provides methods and materials for assessing a mammal having or suspected of having cancer and/or for treating a mammal having cancer. For example, molecules including one or more antigen-binding domains (e.g., a single-chain variable fragment (scFv)) that can bind to a modified peptide (e.g., a tumor antigen), as well as method for using such molecules, are provided.