Catalytic parameters and thermal stability of chondroitinase ABCI on red porous silicon nanoparticles

Abstract

The bacterial enzyme chondroitinase ABC, which digests extracellular chondroitin sulfate proteoglycans, has been shown to enhance axonal regeneration. However, the utilization of this enzyme as therapeutics is notably restricted due to its thermal instability. Therefore, red luminescent porous silicon that hold promise for potential applications in biological/medical imaging was used as a carrying matrix for chondroitinase with the aim of enhancing its stability. Porous Si nanoparticles were prepared by electrochemical etching of silicon wafers in ethanolic HF solution. The size of nanoparticles (210 nm) and the mean pore diameter (8 −20 nm) were determined using dynamic light scattering and scanning electron microscopy. Purified chondroitinase was then incorporated into the silicon pores. Results revealed similar Km and lower Vmax value for the immobilized enzyme when compared with the free enzyme. The immobilized chondroitinase exhibited about a 4 fold increase in stability at 37 °C after 50 min. It is likely possible that, the enzyme was protected inside the pores resulted in higher stability. Moreover, porous silicon was seen to be capable of holding the chondroitinase for repeated cyclic tests for three times. The cell viability assay exhibited no significant cytotoxicity for Psi-chondroitinase up to 24 h.