Thesis Defence: From Biowaste to Biomedicine: Antimicrobial and Biocompatible Cellulose Aerogels Derived from Agricultural Residues
November 12 at 11:00 am - 3:00 pm
Sam Yeo, supervised by Dr. Sepideh Pakpour, will defend their thesis titled “From Biowaste to Biomedicine: Antimicrobial and Biocompatible Cellulose Aerogels Derived from Agricultural Residues” in partial fulfillment of the requirements for the degree of Master of Applied Science in Mechanical Engineering.
An abstract for Sam Yeo’s thesis is included below.
Defences are open to all members of the campus community as well as the general public. Registration is not required for in-person defences.
Abstract
Agricultural residues are produced in staggering quantities worldwide. Too often, they are burned or landfilled, creating pollution while discarding a renewable resource with untapped potential. Transforming these residues into advanced materials (e.g., bioplastics, nanocellulose, aerogels) offers a route to combine sustainability with innovation. Among possible upcycled products, cellulose aerogels stand out for their ultralight structure, high porosity, and tunable surface properties, making them strong candidates for antimicrobial and biocompatible applications. As such, this thesis investigates cellulose aerogels derived from agricultural waste, their functionalization with antimicrobial agents, and biocompatibility performance.
Aerogels were prepared from hemp, flax, and beech wood residues, with commercial cellulose as a benchmark. Synthesis followed a NaOH/urea dissolution route with acid-induced gelation, solvent exchange, and scCO2 drying. Functionalization occurred via immersion in antimicrobial agents (tea tree oil, AgNO₃, ZnCl₂, HM4072, HM4005) or atomic layer deposition (ALD) of ZnO (10–100 cycles). Antimicrobial performance was assessed against Gram-positive (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae). Biocompatibility was evaluated in mammalian cell cultures (MDCK, HDF) and a human epidermis model.
Biowaste-derived aerogels paralleled the physical properties of commercial cellulose (e.g. high porosity, low density), were biocompatible, but lacked intrinsic antimicrobial activity. Commercial cellulose aerogels demonstrated partial inherent activity (S. aureus, K. pneumoniae), yet were cytotoxic (<50% cell viability). Immersion in AgNO₃ or ZnCl₂ eradicated Gram-negative bacteria across aerogel types, while efficacy against S. aureus was limited to select hemp and flax formulations. Likewise, tea tree oil functionalized aerogels eliminated K. pneumoniae, while only hemp and some flax aerogels achieved full inhibition of S. aureus or E. coli. HM4072 was effective only against K. pneumoniae. HM4005 had no activity. Biowaste-derived aerogels retained cell viability after immersion (MDCK; HDF were less robust). Post-ALD, hemp-based aerogels were antimicrobial against Gram-negative (10 cycles) and Gram-positive (50 cycles) species, though cytotoxic after direct contact in cell cultures, but non-toxic in leachate assays at the tissue level.
Evidently, biowaste can be valorized into biocompatible, antimicrobial cellulose aerogels, offering biomedical potential, reducing waste, and advancing circular economy goals.
