Dispersions of single-walled carbon nanotubes (SWNT) and biological molecules can enable multifunctional materials that combine SWNTs’ intrinsic mechanical and/or electrical properties with the properties of the biomolecule. For example, functionalization of SWNT and organic phosphate hydrolase can be used for pesticide detection, and dispersions of SWNT and laccase can be used to make anodes for electrochemical fuel cells. Some of the most intriguing biological SWNT dispersants are double stranded DNA (dsDNA) and enzymes and protein digests containing tryptophan residues. For example, dilute dispersions of dsDNA/SWNT and lysozyme/SWNT have been used to produce conductive antimicrobial films using layer-by layer assembly. Higher concentration dsDNA/SWNT dispersions form either cholesteric or nematic liquid crystalline phases which can be processed into tightly packed aligned films with controlled optical properties. Higher concentration lysozyme/SWNT dispersions can be used to produce mechanically robust antimicrobial films and properties. Finally, dispersion of SWNT in tryptic soy broth (TSB) containing casein digest has recently been shown to enable direct investigation of SWNTs’ microbiological properties in standard biological growth media.