Sustainably Sourced Bacterial Cellulose Nanoparticles for Cellular Drug Delivery

Abstract

Sustainable nanomedicine is an emerging field of nanotherapeutics to combat the environmental impact of current synthetic nanomaterials. Green chemistry and engineering are implemented at the early stages of nanoparticle design and processing to utilize biologically derived nanomaterials, minimize waste generation and the use of harsh solvents, and to create commercially scalable and eco-friendly nanotherapeutics.In this dissertation, we established bacterial cellulose nanoparticles (BCNPs) as a new generation of sustainable nano-platforms, using two independent syntheses to formulate 100 nm and negatively charged BCNPs for protein-based drug loading and cellular delivery. In the first formulation, BCNPs were grown in a kombucha co-culture media in agitated and aerated conditions for 24 h and size separated using centrifugation and polysorbate 80 as a stabilizing surfactant. We reported the BCNPs to be primarily amorphous and thermally stable up to 90 °C. We also performed proof of concept studies to show drug loading capabilities by incorporating bovine serum albumin (BSA) as a model drug and quantified sustained release of BSA. These findings further motivate the use of BCNPs as a promising protein-based therapeutic platform. In a second process to generate nanoparticles, BCNPs were formulated via nanoprecipitation using dissolved bacterial cellulose (BC) in dimethylacetamide and lithium chloride and Pluronic® F-127 as a surfactant. Surface chemistries, such as hydroxyl-, methyl-, acetyl-, and amino- functional groups were applied to BC prior to formulation to create tunable and chemically functional nanoparticles for cellular delivery. Fourier Transformation Infrared Spectroscopy validated the presence of functional groups, and X-ray crystallography and atomic force microscopy revealed distinct structural consequences of the functionalization: 1) methylation caused complete amorphization and lack of nanofibril assembly; 2) acetylation reduced but did not eliminate crystallinity; 3) amination preserved the cellulose backbone connectivity but disrupted long-range order. We assessed the colloidal stability of the functionalized BCNPs in biologically relevant salt- and protein-based environments, where methyl- and amino-BCNPs remained dispersed for 48 h and acetyl-BCNPs agglomerated out of suspension; in comparison, hydroxyl-BCNPs gradually flocculated in salt-based media. To investigate the use of BCNPs for drug delivery to the brain, BCNPs were evaluated in an organotypic whole hemisphere (OWH) brain slice model and exhibited low cytotoxicity (<10%). In the OWH brain slice, we observed functional group-dependent localization and uptake in microglia cells, the brain’s resident immune cell population. Through this body of work, we have developed a small library of innovative BCNPs as a sustainably derived nanoplatform that show good biocompatibility and potential for targeted cell delivery. This foundational work to establish a BCNP platform provides a promising approach to generate eco-friendly nanotherapeutics.