Porous silicon nanoparticle as a stabilizing support for chondroitinase

Chondroitinase ABCI (cABCI) from Proteus vulgaris is a drug enzyme that can be used to treat spinal cord injuries. One of the main problems of chondroitinase ABC1 is its low thermal stability. The objective of the current study was to stabilize the enzyme through entrapment within porous silicon (pSi) nanoparticles. pSi was prepared by an electrochemical etch of p-type silicon using hydrofluoric acid/ethanol. The size of nanoparticles were determined 180 nm by dynamic light scattering and the mean pore diameter was in the range of 40-60 nm obtained by scanning electron microscopy. Enzymes were immobilized on porouse silicon nanoparticles by entrapment. The capacity of matrix was 35 μg enzyme per 1 mg of silicon. The immobilized enzyme displayed lower Vmax values compared to the free enzyme, but Km values were the same for both enzymes. Immobilization significantly increased the enzyme stability at various temperatures (−20, 4, 25 and 37 °C). For example, at 4 °C, the free enzyme (in 10 mM imidazole) retained 20% of its activity after 100 min, while the immobilized one retained 50% of its initial activity. Nanoparticles loading capacity and the enzyme release rate showed that the selected particles could be a pharmaceutically acceptable carrier for chondroitinase.