Biochemical surface modification of Co-Cr-Mo

Area of Science:

• Biomaterials Science
• Surface Chemistry
• Tissue Engineering

Background:

• Polymeric scaffolds have limitations for load-bearing tissue replacements.
• Biochemical surface modification can influence the bone-implant interface.
• Developing effective methods for biomolecule immobilization on implant surfaces is crucial.

Purpose of the Study:

• To evaluate different chemical derivatization methods for immobilizing a model enzyme (trypsin) on cobalt-chromium-molybdenum (Co-Cr-Mo) alloy.
• To compare the effectiveness of tresyl chloride, gamma-aminopropyltriethoxysilane (APS), and p-nitrophenyl chloroformate (p-NPC) immobilization schemes.
• To determine the optimal method for achieving high and stable enzyme activity on the implant surface.

Main Methods:

• Bulk samples of Co-Cr-Mo were chemically modified using tresyl chloride, gamma-aminopropyltriethoxysilane (APS), and p-nitrophenyl chloroformate (p-NPC).
• A model enzyme, trypsin, was immobilized onto the derivatized surfaces.
• Enzyme activity was measured and compared across different immobilization methods and with simple protein adsorption.

Main Results:

• Tresyl chloride was ineffective for immobilizing active trypsin on Co-Cr-Mo.
• Aqueous silanization with 12.5% APS yielded optimal immobilized enzyme activity among silane methods.
• Samples derivatized with p-NPC (0.65 mg/cm²) exhibited significantly higher enzyme activity (4-5 times greater than adsorbed, 8 times greater than tresylated).

Conclusions:

• Chemical derivatization is a viable strategy for altering biomolecule immobilization on Co-Cr-Mo surfaces.
• The choice of immobilization method significantly impacts the level and stability of immobilized enzyme activity.
• p-nitrophenyl chloroformate (p-NPC) offers a highly effective method for enzyme immobilization on Co-Cr-Mo, outperforming other tested schemes.