School of Engineering

Abstract. Durum wheat is used for making pasta and semolina. Knowledge of the structure and properties of microscopic surfaces of durum wheat starch granules at the nanometer level is essential for understanding the functional and physico-chemical properties. The influence of the nanoscale nature of the surface undulations on the starch granules inside durum wheat is macroscopically relevant as it affects the milling properties.

Polymer derived ceramic materials such as SiCN is gaining momentum because of its excellent thermo-mechanical properties at high temperatures. In addition, the electrical conductivity of SiCN can be tailored and characterized to suit specific application needs. These excellent properties make SiCN a best choice for sensor applications.

Abstract. The knowledge of distribution of pore space inside grain bulks is essential for determining the effect of porosity on the airflow resistance of grains. In this study, the geometry of pore structure and the 3D-distribution of void spaces inside the grain bulks were studied using high resolution X-ray computed tomography (CT) images. The quantitative analysis of the architecture, geometry and spatial continuity of the pore network inside grain bulks was done using image processing algorithms.

ABSTRACT Microfluidics, a rapidly emerging enabling technology has the potential to revolutionize food, agriculture and biosystems industries. The principles of eletrokinetics, electro-hydrodynamics, and thermo-capillarity of microfluidic devices help solve important scientific problems that are difficult using conventional technologies. Microfluidic devices allow real-time temporal and spatial sensing in food safety.

ABSTRACT A carbon dioxide sensor was developed using polyaniline boronic acid (PABA) conducting polymer nanoparticles as the electrically conductive region of the sensor and was demonstrated for use in detecting incipient or ongoing spoilage in stored grain. The developed sensor dynamically detected up to 2455 ppm of CO2 concentration levels. The developed sensor was evaluated for the influence of temperature and relative humidity.

Background: Surgical site infections (SSIs) caused by biofilm-forming methicillin-resistant Staphylococcus pseudintermedius (MRSP) have emerged as the most common hospital-acquired infections in companion animals. No methods currently exist for the therapeutic remediation of SSIs caused by MRSP in biofilms. Clarithromycin (CLA) has been shown to prevent biofilm formation by Staphylococcus aureus. This study aims to assess the in vitro activity of CLA in eradicating MRSP biofilm formation on various materials. Results: Quantitative assay results (P = 0.5126) suggest that CLA does not eradicate MRSP biofilm formation on polystyrene after 4 -24 h growth periods. Scanning electron micrographs confirmed that CLA did not eradicate MRSP biofilm formed on orthopaedic implants. Conclusions: By determining the in vitro characteristics and activities of MRSP isolates alone and against antibiotics, in vitro models of biofilm related infections can be made. In vitro data suggests that CLA does not effectively eradicate S. pseudintermedius biofilms in therapeutic doses.

Background: Current methods for testing treatments for veterinary surgical site infections can successfully emulate elements of a chronic wound, but these are time consuming and costly, requiring specialized laboratory equipment and considerable space to house study animals. Microfluidic devices however, can be coated with collagen and maintained at basal body temperature, providing a more cost-effective and space-saving model of a chronic wound. Our study assesses the applicability of a new microfluidic model by testing the activity of DispersinB against biofilms of methicillin-resistant Staphylococcus pseudintermedius (MRSP); DispersinB has been shown to prevent biofilm growth of Staphylococcus epidermidis, another prominent wound colonizer.

Here we present a high-resolution chromosomal spectral map derived from synchrotron-based soft X-ray spectromicroscopy applied to quinoa species. The label-free characterization of quinoa metaphase chromosomes shows that it consists of organized substructures of DNA-protein complex. The analysis of spectra of chromosomes using the scanning transmission X-ray microscope (STXM) and its superposition of the pattern with the atomic force microscopy (AFM) and scanning electron microscopy (SEM) images proves that it is possible to precisely locate the gene loci and the DNA packaging inside the chromosomes. STXM has been successfully used to distinguish and quantify the DNA and protein components inside the quinoa chromosomes by visualizing the interphase at up to 30-nm spatial resolution. Our study represents the successful attempt of non-intrusive interrogation and integrating imaging techniques of chromosomes using synchrotron STXM and AFM techniques. The methodology developed for 3-D imaging of chromosomes with chemical specificity and temporal resolution will allow the nanoscale imaging tools to emerge from scientific research and development into broad practical applications such as gene loci tools and biomarker libraries.

The effectiveness of fosfomycin was examined across 31 methicillin-resistant Staphylococcus pseudintermedius (MRSP) strains by agar dilution. Prevalence of the fosfomycin-resistance determinant gene, fosB, was assessed by PCR analysis. Results found that 84% of isolates were fosfomycin-susceptible. Interestingly, 87% of isolates possessed fosB, indicating no association between this putative staphylococci resistance gene and phenotypic resistance. Further evaluation of fosfomycin as a potential treatment of MRSP in dogs is warranted.

Chitosan has been reported to be a non-toxic, biodegradable antibacterial agent. The aim of this work was to elucidate the relationship between the molecular weight of chitosan and its antimicrobial activity upon two model microorganisms, one Gram-positive (Staphylococcus aureus) and one Gramnegative (Escherichia coli). Atomic force microscopy (AFM) imaging was used to obtain high-resolution images of the effect of chitosans on the bacterial morphology. The AFM measurements were correlated with viable cell numbers, which show that the two species reacted differently to the high-and lowmolecular-weight chitosan derivatives. The images obtained revealed not only the antibacterial effects, but also the response strategies used by the bacteria; cell wall collapse and morphological changes reflected cell death, whereas clustering of bacteria appeared to be associated with cell survival. In addition, nanoindentation experiments with the AFM revealed mechanical changes in the bacterial cell wall induced by the treatment. The nanoindentation results suggested that despite little modification observed in the Gram-positive bacteria in morphological studies, cell wall damage had indeed occurred, since cell wall stiffness was reduced after chitooligosaccharide treatment.

A nanorobot is defined as any smart structure which is capable of actuation, sensing, manipulation, intelligence, and swarm behavior at the nanoscale. In this study, we designed an intelligent system using fuzzy logic for diagnosis and treatment of tumors inside the human body using bionanorobots. We utilize fuzzy logic and a combination of thermal, magnetic, optical, and chemical nanosensors to interpret the uncertainty associated with the sensory information. Two different fuzzy logic structures, for diagnosis (Mamdani structure) and for cure (Takagi-Sugeno structure), were developed to efficiently identify the tumors and treat them through delivery of effective dosages of a drug. Validation of the designed system with simulated conditions proved that the drug delivery of bionanorobots was robust to reasonable noise that may occur in the bionanorobot sensors during navigation, diagnosis, and curing of the cancer cells. Bionanorobots represent a great hope for successful cancer therapy in the near future.

Bacterial biofilms are of tremendous concern for clinicians, as they can compromise the ability of the immune system and antimicrobial therapy to resolve chronic and recurrent infections. Novel antimicrobial therapies or combinations targeted against biofilm establishment and growth subsequently represent a promising new option for the treatment of chronic infectious diseases. In this study, we treated bacterial biofilms produced by methicillin-resistant Staphylococcus pseudintermedius (MRSP) with a combination of fosfomycin and clarithromycin. We selected these agents, because they prevent biofilm formation and induce antimicrobial synergism that may also target other staphylococci.

Background: Determination of β-hydroxybutyrate (βHBA) is a gold standard for diagnosis of Subclinical Ketosis (SCK), a common disease in dairy cows that causes significant economic loss. Early detection of SCK can help reduce the risk of the disease progressing into clinical stage, thus minimizing economic losses on dairy cattle. Conventional laboratory methods are time consuming and labor-intensive, requiring expensive and bulky equipment. Development of portable and robust devices for rapid on-site SCK diagnosis is an effective way to prevent and control ketosis and can significantly aid in the management of dairy animal health. Microfluidic technology provides a rapid, cost-effective way to develop handheld devices for on-farm detection of sub-clinical ketosis. In this study, a highly sensitive microfluidics-based biosensor for on-site SCK diagnosis has been developed. Results: A rapid, low-cost microfluidic biosensor with high sensitivity and specificity was developed for SCK diagnosis. Determination of βHBA was employed as the indicator in the diagnosis of SCK. On-chip detection using miniaturized and cost-effective optical sensor can be finished in 1 minute with a detection limit of 0.05 mM concentration.

Microbial attachment is the first and only reversible step in biofilm formation and the physical attributes of the substrate surface play a crucial role in the attachment process. Medically relevant surfaces such as clean stainless steel and gold surfaces exhibit negative surface potentials and inhibit microbial attachment. Poly-Llysine functionalized surfaces have positive surface potentials and promote the rapid attachment of microbes after 30 minutes. KPFM analyses revealed that the cell surface potentials for all species (Pseudomonas aeruginosa and MRSA) and culture conditions were affected by the type of substrate used. Co-culturing in vitro, which mimics the in vivo situation, is a critical factor determining the observed shifts in surface potential for MRSA, significantly affecting its cellular activity. Selective plating experiments further confirmed the growth inhibition of MRSA in the presence of P. aeruginosa. Under KPFM measurement conditions it was revealed that both microbial species show positive cell surface potentials, with the exception of MRSA on the gold surface. No morphological changes were observed in both mono and co-cultured P. aeruginosa and MRSA as observed by atomic force microscopy. Zeta potential measurements on cultures revealed negative zeta values. This study provides an insight into the electrokinetic dynamics of surfaces and their consequence on the attachment of virulent bacteria. The study further highlights the importance of physical attributes such as surface charge, that could be exploited for the development of therapies involving nanocoatings or electrical fields in order to prevent microbial attachment and the formation of recalcitrant wound biofilms.

The majority of foodborne illness outbreaks can be linked to cross-contamination events through contact with contaminated surfaces. Consequently, there is a sustained interest in developing antimicrobial coatings such as silver zeolite to reduce contamination levels. In this study, we examined the efficacy of silver zeolite for preventing biofilm formation by common foodborne pathogens such as Listeria innocua Seeliger and Escherichia coli O157:H7. Biofilm formation was assessed by cresyl violet assay, quantification of colony-forming units and scanning electron microscopy, and atomic force microscopy. For silver zeolite suspended in growth media, concentrations of 0.3% w/v were effective at reducing bacterial growth of L. innocua after 8 h. For E. coli incubated with silver zeolite, there was a dosedependent reduction in bacteria after 4 h. When coated stainless steel coupons were incubated with Listeria and E. coli, significant reductions in bacterial growth were achieved. Coating stainless steel food processing surfaces with silver zeolite may provide a means of reducing cross-contamination events of pathogens and spoilage microbes. The ability of the surface to resist the attachment of biofilms provides a complementary approach to chemical sanitation.

Wounds can easily become chronically infected, leading to secondary health complications, which occur more frequently in individuals with diabetes, compromised immune systems, and those that have suffered severe burns. When wounds become chronically infected, biofilm producing microbes are often isolated from these sites. The presence of a biofilm at a wound site has significant negative impact on the treatment outcomes, as biofilms are characteristically recalcitrant to removal, in part due to the formation of a protective matrix that shield residents organisms from inimical forces. Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus (MRSA) are two of the organisms most prevalently isolated from wound sites, and are of particular concern due to their elevated levels of antibiotic resistance, rapid growth, and exotoxin production. In order to understand the biofilm forming abilities of these microbes in a simulated wound environment we used a microtiter plate assa...

Surface potential is a commonly overlooked physical characteristic that plays a dominant role in the adhesion of microorganisms to substrate surfaces. Kelvin probe force microscopy (KPFM) is a module of atomic force microscopy (AFM) that measures the contact potential difference between surfaces at the nano-scale. The combination of KPFM with AFM allows for the simultaneous generation of surface potential and topographical maps of biological samples such as bacterial cells. Here, we employ KPFM to examine the effects of surface potential on microbial adhesion to medically relevant surfaces such as stainless steel and gold. Surface potential maps revealed differences in surface potential for microbial membranes on different material substrates. A step-height graph was generated to show the difference in surface potential at a boundary area between the substrate surface and microorganisms. Changes in cellular membrane surface potential have been linked with changes in cellular metabol...

Wound healing is a complex process essential to repairing damaged tissues and preventing infection. Skin is the first line of defense, a chief physical barrier to microbe entry. Wound healing is a physical rebuilding process, but at the same time it is an inflammatory event. In turn, molecules for wound repair are secreted by fibroblasts and others present at the wound site. Vascular endothelial growth factor (VEGF) is a critical cytokine that exhibits chemoattractant properties, recruiting other immune cells to the site. Although generally beneficial, VEGF may also act as a chemoattractant for invading microorganisms, such as Pseudomonas aeruginosa. P. aeruginosa is problematic during wound infection due to its propensity to form biofilms and exhibit heightened antimicrobial resistance. Here, we explored the influence of VEGF gradients (in a microfluidic device wound model) on the motility and chemotactic properties of P. aeruginosa. At lower concentrations, VEGF had little effect ...