Combating Wound Infections Through the Use of Microfluidic Devices, Antimicrobial Hydrogels, and Layer-by-Layer Films

Over the years, engineers have developed cutting-edge techniques to propel the advancement of research in some of the world’s most complex problems. The use of such techniques to develop tools and materials with a broad range of applications and functions is pivotal to drive innovation and the progression of society. Microfluidic devices, hydrogels, and layer-by-layer (LbL) films are three commonly employed engineering tools with highly tunable features capable of being exploited to tackle a variety of issues. Of particular interest is their application towards bacterial analysis and wound infection research due to the looming threat of antimicrobial resistance, which must be addressed now to avoid serious societal health implications and increases in multi-resistant superbugs. In this dissertation, a three-dimensional (3D) printed microscope mask alignment adapter (MMAA) was created to facilitate efficient, accurate, and affordable multi-layer microfluidic device production. By using common laboratory equipment combined with the MMAA, a double-layer master mold of a herringbone microfluidic device and a four-layer master mold of stacked microstructures were fabricated with minimal alignment errors. Fully functional herringbone microfluidic devices were procured using the associated master mold, solidifying the adequate alignment efficacy of the MMAA. Next, a multi-functional and inherently antibacterial hydrogel was fabricated using chitosan (CHI), aldehyde-chitosan (ACHI), and phytic acid (PA) to assess its applicability as a bioactive wound dressing. The two-layer hydrogel was produced from a two-step process resulting in a CHI/ACHI hydrogel core with an outer CHI/ACHI/PA hydrogel layer. The CHI/ACHI hydrogel showed optimal skin adhesion, easy injectability, and complete killing of Staphylococcus aureus and Escherichia coli in vitro. In addition, the CHI/ACHI/PA hydrogel demonstrated enhanced mechanical strength and good biocompatibility, allowing it to act as a protective layer. Finally, a LbL film was designed for wound bandage coating to maximize loading and delivery of the biofilm-degrading enzyme α-amylase (AMY). The LbL film was fabricated using CHI, carboxymethyl cellulose (CMC), and AMY and successfully deposited on commercial wound bandages using the standard dipping method and underutilized vacuum-assisted method. AMY loading and release from the film system was confirmed by quartz crystal microbalance with dissipation analysis and fluorimetry, respectively. Optimal film building parameters (AMY pH, number of layers, fabrication method) and film degradation conditions (temperature, time, media type) were determined to maximize AMY loading and subsequent release. In addition, the AMY concentrations of several films were analyzed, and the optimal film was tested against Pseudomonas aeruginosa to determine its antibiofilm activity.