The facile conjugation of biomolecules onto surfaces through mussel adhesive protein inspired coatings were studied. The study demonstrated that bioconjugation reactions on polydopamine surfaces can be modulated by pH, affording discrimination among nucleophiles. The experiment involves the immersion of substrates into 2mg of dopamine. Hcl per 1mL of 10mM tris buffer was rinsed with water for further use. The surface topography was measured in air using an MFP-3D atomic force microscope operated in AC and contact modes. The study showed that bioconjugation to polydopamine is easily adapted for a variety of materials without surface treatment, and is unaffected by incubation in water and through pH control it offers selectivity of reaction with amine or imidazole functional groups of biomolecules. The result also showed that the method used was proved useful for surface immobilization of a variety of biomolecules, as proteins in DNA.