I. Rapid detection of pathogenic bacteria with immutable ligands. II. Mechanochemical surface modification of cellulose nanocrystals

Thora R Maltais, Purdue University

Abstract

I. Rapid Detection of Pathogenic Bacteria with Immutable Ligands Rapid detection methods are necessary to improve diagnostics for efficient identification of pathogenic bacteria. By focusing on their innate virulence factors, pathogenic bacteria offer specific markers for their rapid and efficient identification. These “immutable” factors include heme protein acquisition systems to harvest iron, used by certain Gram-positive bacteria, and cell-surface glycans like α-mannoside that are recognized by Type 1 fimbriae, as expressed by certain Gram-negative bacteria. Chapter 1 describes how the hemin acquisition systems of select Gram-positive bacteria provides opportunities for rapid detection by a direct targeting mechanism. Functional assays were developed for identifying pathogens that express high-affinity cell-surface hemin receptors (CSHRs), using hemin analogs or conjugates for rapid detection or visualization. Several Gram-positive bacteria including Bacillus anthracis, Staphylococcus aureus, and Streptococcus pneumoniae are detected within minutes by Ga–PpIX, a fluorescent hemin analog, and by adhesion onto hemin-conjugated substrates using a label-free optical imaging modality. Direct recognition of hemin by CSHR-expressing bacteria permits their discrimination from bacteria that rely on the release and recapture of hemophores for hemin acquisition, with subsequently longer times to detection. Direct hemin capture provides a novel approach for rapid identification of CSHR-expressing bacteria for diagnosis, with implications for targeted therapies. Chapter 2 includes studies that suggest the Enterobacteriaceae, whose Type 1 fimbriae provide preferential adhesion to α-mannosides, can be further discriminated by using glycoconjugates with different linkers. Preliminary studies have revealed that E.coli and Salmonella sp. can be selectively identified by designing α-mannoside ligands with hydrophobic substituents, and negative control studies with S. aureus support the use of α-mannoside recognition as a functional alternative to Gram classification. II. Mechanochemical Surface Modification of Cellulose Nanocrystals Efforts to incorporate biorenewable resources into manufactured goods have increased since the introduction of green chemistry practices in the 1990s. Cellulose nanocrystals (CNCs) are attractive for their low carbon footprint and scalable preparation, and are amenable to surface modification for improved materials processing. In particular, esterification of CNCs can enhance their miscibility with various types of thermoplastics. In Chapter 3, we apply mechanochemical methods to esterify CNCs with fatty acids by ball milling using catalytic amounts of solvents (50 μL/g). Mechanochemical functionalization of CNCs is facile and can be achieved with several variations in synthesis design. In the course of this work, zeolitic imidazolate frameworks (ZIFs) were identified as novel reagents for CNC esterification under ball-milling conditions. Blending esterified CNCs into bulk thermoplastics may lead to lightweight materials with enhanced mechanical properties, while reducing carbon footprint and chemical waste.

Degree

Ph.D.

Advisors

Wei, Purdue University.

Subject Area

Microbiology|Biochemistry

Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server
.

Share

COinS