Proteases immobilized on nanomaterials for biocatalytic, environmental and biomedical applications: Advantages and drawbacks

Proteases have gained significant scientific and industrial interest due to their unique biocatalytic characteristics and broad-spectrum applications in different industries. The development of robust nanobiocatalytic systems by attaching proteases onto various nanostructured materials as fascinating and novel nanocarriers has demonstrated exceptional biocatalytic performance, substantial stability, and ease of recyclability over multiple reaction cycles under different chemical and physical conditions. Proteases immobilized on nanocarriers may be much more resistant to denaturation caused by extreme temperatures or pH values, detergents, organic solvents, and other protein denaturants than free enzymes. Immobilized proteases may present a lower inhibition. The use of non-porous materials in the immobilization prevents diffusion and steric hindrances during the binding of the substrate to the active sites of enzymes compared to immobilization onto porous materials; when using very large or solid substrates, orientation of the enzyme must always be adequate. The advantages and problems of the immobilization of proteases on nanoparticles are discussed in this review. The continuous and batch reactor operations of nanocarrier-immobilized proteases have been successfully investigated for a variety of applications in the leather, detergent, biomedical, food, and pharmaceutical industries. Information about immobilized proteases on various nanocarriers and nanomaterials has been systematically compiled here. Furthermore, different industrial applications of immobilized proteases have also been highlighted in this review.

Immobilization of Trypsin from the Subphase to the Langmuir Monolayer of Fluorocarbon-Modified Single-Walled Carbon Nanotube and Its Activity Maintenance

Single-walled carbon nanotubes (SWCNTs) synthesized by the improved arc discharge method were modified with a fluorocarbon chain, and the maintenance of trypsin activity upon adsorption from the subphase to the interfacial monolayer of SWCNTs was evaluated. The adsorption of trypsin on the fluorocarbon-modified SWCNT monolayer was confirmed by morphological and spectroscopic evaluations. Fiber morphology studies revealed that the fluorocarbon-modified SWCNT monolayer was covered by trypsin, and a trypsin-derived amide band was detected in the infrared spectra of the multilayers. After adsorption onto the fluorocarbon-modified SWCNT film, the ability of trypsin to cleave the fluorescent casein chain was maintained even at 160 °C. Furthermore, circular dichroism (CD) spectra showed that the second-order structure of the activity of trypsin adsorbed on the fluorocarbon-modified SWCNT was maintained up to nearly 200 °C. At 200 °C, the enhancement of emission intensity by casein chain cleavage was negligible, and the CD signal resulting from the negative Cotton effect was completely altered at 250 °C.