Enhanced thermal and ultrasonic stability of a fungal protease encapsulated within biomimetically generated silicate nanospheres

Background: Dendrimers are highly branched synthetic macromolecules with a globular shape. They have been successfully used for generation of nanospheres at mild conditions via biomimetic silicification. Encapsulation of enzyme molecules within these nanospheres during their synthesis is a promising method for rapid and efficient entrapment of several enzymes. However, encapsulation of proteolytic enzymes has been rarely done via biomimetic silicification. As well, the operational stability of encapsulated enzyme has not been systematically reported. Methods: A proteolytic enzyme, either alpha-Chymotrypsin or a fungal protease from Aspergilus Oryzea was encapsulated along with iron oxide nanoparticles within particles yielded via biomimetic silicification of different generations of polyamidoamine (PAMAM) dendrimers. Stability of encapsulated enzyme was compared to that of free enzyme during storage at room temperature. As well, their thermal and ultrasonic stabilities were measured. Scanning electron microscopy, transmission electron microscopy and optical microscopy were used to investigate the morphology of nanospheres. Results: Determination of encapsulation efficiency revealed that similar to 85% of fungal protease with concentration 1.4 mg mL(-1) stock solution was immobilized within particles yielded by generation 0. Based on microscopic images the generated particles interconnected with each other and had spherical morphologies independent of generation. Kinetic analysis of encapsulated fungal protease demonstrated that Mechaelis-Menten constant (K(m)) slightly increased. Conclusion: PAMAM dendrimer generation 0 Could be effectively used for rapid encapsulation of a fungal protease from Aspegilus Oryzae. General significance: Encapsulation significantly enhances the thermal and Ultrasonic stabilities of enzymes, suggesting a range of diverse applications for them. (c) 2010 Elsevier B.V. All rights reserved.