Immobilization of biocatalysts in SBA-15 ordered mesoporous silica with cross-linked enzyme aggregates

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Erika Crowley

Abstract




Naturally occurring enzymes have many advantages over synthetic catalysts as biocatalytic materials. In specific, biospecies have greater catalytic activity and are more environmentally friendly. However, the loss of enzyme stability when they are removed from physiological conditions poses a significant challenge to their widespread application. Enzyme entrapment through encapsulation in templated silica materials known as Santa Barbara acid (SBA) is a cost effective and convenient approach to retaining enzyme activity in environments that differ from the physiological state. However, once the SBA host is loaded with enzyme, leaching from the material can lead to a significant loss of activity. Previous work has demonstrated that glutaraldehyde cross-linking of the enzymes to form crosslinked enzyme aggregates (CLEA) reduces leaching. The present work investigates the novel combination of SBA-15 enzyme encapsulation and CLEA formation to generate a matrix that enables hosting of a functionally active enzyme and mitigates leaching. The Brunauer-Emmett-Teller (BET) surface area of our


material that was used to encapsulate either cytochrome b5 or pepsin was 690 ± 60 m2/g. It was demonstrated that the Pluronic P-123 templating agent was necessary to make a uniform porous structure that can be used for encapsulation. Untemplated materials, while generating high surface areas, were not structured enough to effectively load the enzyme. UV-visible spectroscopy was used to probe loading efficiency as a function of pH and encapsulation time; loading efficiency and leaching as a function of loading concentration; and glutaraldehyde concentration as a function of leaching. Encapsulation in a templated silica with post-encapsulation CLEA formation is a promising approach for generating biocatalytic materials.




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Author Biography

Erika Crowley, OC

Erika Crowley is currently a Master’s Candidate in the Environmental and Life Sciences Program, using nuclear magnetic resonance spectroscopy to determine the structure of cytochrome b5 in the parasite Giardia lamblia. Erika also does research in clinical dermatology, specifically exploring treatment options for patients with hidradenitis suppurativa, chronic hand dermatitis, atopic dermatitis, palmoplantar pustulosis, alopecia areata, and other skin conditions. Erika completed her undergraduate Honours degree at Trent University in Biochemistry and Molecular Biology, with Specialization in Health Science. Her undergraduate thesis in the Inorganic Material Science Laboratory focused on the synthesis and characterization of Santa Barbara-15 silica polymers with cross-linked enzyme aggregates to retain native properties of enzymes when in unfavourable environments. Erika has had leadership roles in several clubs, including the Trent Pre-Medical Society, Chemistry Society, and Biology Society. Other commitments include the Trent Graduate Student Association, Journal of Multidisciplinary Research at Trent, Journal of Undergraduate Studies at Trent, Symons Seminar Series, Research Ethics Committee, Biology Curriculum Committee, and quadriplegic care. In her spare time, Erika volunteers at the Salvation Army to provide a free breakfast to the Peterborough community and at the Peterborough Regional Hospital to help patients achieve cardiac rehabilitation. Erika plans to pursue a MD/PhD after her Master’s degree.