Bioconjugated nanotubes combined with the sensitive nanotube-based electronic devices would enable sensitive biosensors toward medical diagnostic. Furthermore, recent findings of improved cell membrane permeability for carbon nanotubes would also expand medical applications to therapeutics using carbon nanotubes as carriers in gene delivery systems. One of the main issues in nanobio systems is the specificity, which requires biofunctionalization of nanomaterials for recognition of only one type of target biomolecule. This study presents an effective functionalization scheme for preventing non-specific antibody binding on nanotubes. Non-specific antibody binding on nanotubes was successfully prevented by co-adsorption of a bio-compatible polymer PEG and a surfactant (NaDDBS) on nanotubes. Optical studies through confocal microscopy revealed very minimal non-specific antibody binding on the PEG/NaDDBS-coated nanotubes (WCC < 0.05) compared to high degree of non-specific antibody binding on nanotubes without PEG pretreatment (WCC >0.80), as determined by weighted co-localization coefficients (WCC). In addition to the confocal microscopy studies, electronic detection studies revealed that PEG/NaDDBS pretreated devices exhibited very little conductance change due to antibody adsorption compared to the devices without any PEG/NaDDBS pretreatment. These findings indicate that the PEG/NaDDBS pretreatment is a very effective functionalization scheme in preventing non-specific antibody binding on nanotubes. © 2008 Materials Research Society.