Microfluidic-based microgels for biomedical applications
Guerzoni, Luis Paulo Busca; De Laporte, Laura (Thesis advisor); Möller, Martin (Thesis advisor)
Aachen : RWTH Aachen University (2021)
Dissertation / PhD Thesis
Dissertation, RWTH Aachen University, 2021
In this thesis, I developed three different microfluidic platforms to produce cell-loaded spherical, cell-loaded anisometric microgels and microgel capsules as drug delivery systems. In chapter 2, for the first time, I performed the encapsulation of cardiomyocytes derived from human-induced pluripotent stem cells (hiPSC-CM) in poly(ethylene glycol) (PEG)-based microgels generated via microfluidics. Microgels contained a matrix metalloproteinase (MMP)-sensitive crosslinker peptide for degradation. The layer-by-layer (LbL) deposition of fibronectin(FN) and gelatin (G) molecules on single cells to form an extracellular matrix (ECM) nanofilm on cells’ surfaces prior to encapsulation enhanced cell-cell interactions, and consequently viability and functionality of encapsulated hiPSC-CMs. This has led to functional beating cardiac mini tissues. In chapter 3, I developed a novel method to produce monodisperse anisometric PEG microgels via click chemistry and microfluidics that have the potential to be used as biocompatible scaffold for cell encapsulation with controlled directionality. Flow ratios controlled the microgels’ aspect ratios and varying the initial prepolymer concentration led to different microgels’ mechanical properties. The anisometric microgels’ showed homogeneous crosslinking degree evaluated by cryo-scanning electron microscopy (cryo-SEM) and Stimulated Emission Depletion (STED) microscopy. Encapsulated Normal Human Dermal Fibroblasts (NHDFs) remained viable and migrated across the anisometric microgels’ structure. In chapter 4, a microfluidic technique was developed for the continuous fabrication of stable, monodisperse water-in-oil-in-water (W/O/W) double emulsion droplets. A multi-arm PEG-acrylate prepolymer was dissolved in the middle oil phase and crosslinked under UV light to form microgel capsules. These microgel capsules had an aqueous core which enabled the encapsulation of large amounts of hydrophilic biomolecules during microfluidic production (virtual 100% encapsulation efficiency). Shell thickness of microgel capsules and their overall diameters were tuned by varying the flow rates. The morphology and thickness of the shellswere determined by cryo-SEM, and the retention and release of 10 kDa fluorescein isothiocyanate (FITC)-dextran were monitored via fluorescence microscopy. The results of this thesis potentially serve as inspiration for further researches, where the focus is to continuously produce shape-controlled microgels that could be delivered to injured or damaged tissues through minimally invasive techniques, either as cell or drug carriers, with the great potential of controlled release of their cargo.