Detection of human neutrophil elastase by fluorescent peptide sensors conjugated to TEMPO-oxidized nanofibrillated cellulose

Authors: Mackin, Robert; Fontenot, Krystal; Edwards, Judson - Vince; Prevost, Nicolette; Jordan, Jacobs; Easson, Michael; Condon, Brian; French, Alfred - Al

Submitted to: International Journal of Molecular Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/2/2022
Publication Date: 3/13/2022
Citation: Mackin, R.T., Fontenot, K.R., Edwards, J.V., Prevost, N.T., Jordan, J.H., Easson, M.W., Condon, B.D., French, A.D. 2022. Detection of human neutrophil elastase by fluorescent peptide sensors conjugated to TEMPO-oxidized nanofibrillated cellulose. International Journal of Molecular Sciences. 23(6):3101. https://doi.org/10.3390/ijms23063101.
DOI: https://doi.org/10.3390/ijms23063101

Interpretive Summary: Effectively detecting elevated levels of pathogens in chronic wounds is crucial to early diagnosis and treatment. Human Neutrophil Elastase (HNE) is one such pathogen. When present in normal levels in the body, it can aid in wound repair and regeneration. However, at elevated levels, HNE prevents wound healing and works to degrade healthy tissue, furthering the severity of the wound. In our work, we test the biosensor activity of a TEMPO-oxidized cellulose-peptide conjugate in the presence of human neutrophil elastase and compare those results to previous cellulose-based sensor devices. We employ molecular modeling to investigate how to optimize the biosensor devices, and then examine new materials which can be used in future work to develop a more sensitive detection system for use in chronic wounds.

Technical Abstract: Peptide-cellulose conjugates designed for use as optical protease sensors have recently gained interest for point-of-care (POC) detection. Elevated serine protease levels are often found in patients with chronic illnesses, leading to increased enthusiasm for optimizing biosensor design for POC assessment. Nanocellulose provides a platform for protease sensors as a transducer surface, and the employment of nanocellulose in this capacity combines its biocompatibility and high specific surface area properties to confer sensitive detection of highly dilute biomarkers. However, a basic understanding of the spatiotemporal relationships of the transducer surface and sensor disposition is needed to improve protease sensor design and development. Therefore, balancing sensor detection sensitivity with selectivity poses fundamental questions about the molecular orientation of the sensor to the cellulose surface. Here we examine an elastase biosensor attached to the glucan C6 hydroxyl of nanofibrillated TEMPO-oxidized cellulose. The sensor is elongated with respect to the transducer surface by a PEGylated linker attached to an elastase substrate composed of a tripeptide and capped by a coumarin fluorophore. The synthetic conjugate was found to be active in the presence of Human Neutrophil Elastase at levels comparable to other cellulose-based biosensors. Computational models were designed to examine the relationship of the biosensor to the transducer surface. These calculations suggested notable differences in two crystallite transducer surfaces (110 vs. 1-10) and revealed preferred orientations of the peptide with respect to the cellulose crystallite based on Boltzmann distribution determinations. Finally we report the results of a determination of the relative 110 vs 1-10 orientations of crystals extracted from cotton. These provide a source of preferred orientations that illustrates the 1-10 conformer orientation. This model study will potentiate realizing HNE sensor results for enhanced sensor activity design. Thus, the results of this study offer insight into potential design approaches for biosensors using specific peptide/cellulose crystallite orientations to provide the highest level of sensitivity for POC diagnostics.