Influence of material properties upon immobilization of histidine-tagged protein on Ni–Co coated chip

• Ni–Co material properties upon the immobilization of His-tagged protein were studied.
• Ni–Co protein chip with majority of hcp lattice has better binding capability.
• Wettability property of Ni–Co layer is not the dominant factor.

In protein research, protein microarray facilitates high-throughput study of protein abundance and function. An appropriate microarray surface that can be used to immobilize protein samples is a prerequisite for the investigation of molecular interactions. Ni–Co alloy coated protein microarray chip has been found to adsorb histidine-tagged proteins effectively based on the method of immobilized metal affinity chromatography. Due to the ingredient of bi-metallic elements, different electroplating conditions resulted in distinct binding affinities. Therefore, the influence of Ni–Co material properties on the immobilization of histidine-tagged protein was systematically investigated in this study. In the experiments, the contact angle measurement suggested that no strong relationship can be established between the wettability of chip surface and its corresponding protein immobilization. ESCA test demonstrated that the major ingredients of the Ni–Co alloy coated protein microarray chip were Ni and Co. In addition, the XRD test concluded that a Ni–Co protein chip that consists mostly of hcp lattice has better binding capability. SEM micrographs provide direct image evidence. These material tests summarize that the Ni–Co alloy coated protein microarray chip adsorbs His-tagged proteins through its surface morphology. Therefore, it can provide specific binding due to the affinity adsorption between the intermediate metals and the protein.