The potential of physiologically relevant in vitro cell culture models for studying physiological and pathophysiological phenomena has been widely recognized as replacements for animal and conventional in vitro models. To create models that accurately replicate the structure and function of tissues and organs, it is essential to comprehend the biophysical and mechanical features of the extracellular matrix (ECM) and incorporate them into the in vitro cell culture models. Therefore, we first aimed to investigate how nanotopography can modulate cell behaviors by studying cell behaviors on nanostructures of various aspect ratios on a cobalt-chromium-molybdenum (CoCrMo) alloy surface. We also explored the impact of nanofibrous membranes on the formation of alveolar epithelium, which is critical for lung alveolar interstitium chips. In addition, we investigated the effect of mechanical stretch on cell behaviors and focused on how the dimensionality of the stretch affects cell behaviors. To create physiologically relevant in vitro models based on our findings, we engineered a stem cell niche using a combination of nanofibrous membranes, mechanical stretch, and a soft substrate, and evaluated its impact on stem cell behaviors. Finally, we created a biomimetic human lung interstitium chip for application in physiological and pathophysiological in vitro studies.

Considering that both cardiovascular disease (CVD) and congenital heart diseases (CHD) are still the leading cause of morbidity and mortality worldwide, there is a need for a robust and reliable cardiac model. Cardiac organoids are complex, three-dimensional cellular constructs that recapitulate the processes of the human embryonic heart. However, certain vital morphological features within the fetus are not yet replicable with cardiac organoids. Here we report our investigation to generate cardiac organoids with chamber formations. Our method involves modulating the Wnt pathway at two different instances while also implementing two cell seeding densities, all to determine the most optimized that to produce chamber formations within cardiac organoids.

The heart is a dynamic environment that is constantly experiencing some degree of remodeling from the point of development, all the way through adulthood. While many genetic components may contribute to the overall presentation of hypertrophic cardiomyopathy (HCM), mutations occurring in sarcomere components such as myosin binding protein C3 (MYBPC3) are of the greatest popularity for study. Aiming to understand the mechanisms underlying heart diseases and to develop effective treatments that circumvent the need for direct patient study, we investigated the use of a platform to mimic the unique physiological conditions of HCM within an in-vitro setting. Following the induction of mechanical stretch on three human induced pluripotent stem cell derived cardiomyocyte (hiPSC-CM) cell lines containing mutations for MYBPC3 (WT, HET, HOM), all displayed HCM like reactions in calcium waveform. In conclusion, this system demonstrated the potential to apply a constant, static strain to healthy and mutated hiPSC-CMs for the MYBPC3 protein to model HCM in-vitro.

Soft actuation methods are a developing field of robotics deemed suitable for physical human-robot interactions due to the adaptability of materials and compliant structures. Thermo-active soft actuators are a subset of these which convert thermal energy to mechanical work in the form of elongation, bending, or twisting to conform to the environment. This study is divided into three major studies that all use actuators with a working principle of phase-change fluid vaporizing for expansion with applied heat from a Peltier. The first study evaluates the bandwidth and efficiency between (i) traditional Joule heating, and (ii) Peltier heating, finding that Peltier heating can considerably improve the operational bandwidth of the actuator. The second study uses a thin membrane actuator placed in a braided mesh to form a McKibben muscle capable of lifting 5N, and formed into a gripper capable of manipulating objects within the environment. The third study uses actuators of a solid, hollow and flexible Peltier embedded silicone structure and are evaluated and optimized in order to increase actuation speed, finding that the embedded flexible Peltier design was able to elongate over 50% of its original height in 20 seconds. The overall aim of all of these studies was to …

The blood-brain barrier (BBB) is composed of brain microvascular endothelial cells (BMECs), pericytes, and astrocytic endfeet, which regulate the transport of molecules into and out of the brain. BMECs possess intrinsic barrier properties that limit the passage of approximately 98% of small molecules into the brain in healthy individuals. However, in some brain diseases, the BBB undergoes structural and functional alterations, which can contribute to disease progression. In this study, we aimed to investigate the BBB by exploring the effects of endothelial cell stretching and the optimal dimensionality of stretching to enhance endothelium barrier tightness in Chapter 2. Subsequently, we developed an endothelium gradient stretching device to further examine the stretching effect in Chapter 3. Additionally, we investigated the promotion of endothelium tightness through the use of electrospun fibers, wherein we controlled the pore size. Based on these findings, we designed and fabricated an organ chip model that incorporates mechanical stretching, microfluidic techniques, electrospun fibers, and hydrogel extracellular matrix (ECM). The results of permeability testing demonstrated that this chip significantly improved the tightness of microvascular selective transport ability and has the potential to be used in drug sorting for central nervous system (CNS) diseases.

In this research, we aimed to develop thin-film devices on a polymer substrate and an alternative 3D-printed device with macroelectrodes for treating gastrointestinal (GI) conditions. First, the fabrication of thin-film devices was demonstrated on a softening thiol-ene/acrylate polymer utilizing titanium nitride (TiN) as electrode material. This was achieved by utilizing cleanroom fabrication processes such as photolithography, wet and dry etching. The functionality of the device was shown by performing electrochemical characterization tests, mainly cyclic voltammetry, electrochemical impedance spectroscopy, and voltage transient. We synthesized a novel thiol-ene/acrylate polymer based on 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TATATO), trimethylolpropanetris (3-mercaptopropionate) (TMTMP), and polyethylene glycol diacrylate (PEGDA). We show that this stretchable shape memory polymer substrate is well suited for cleanroom processes. Finally, for the high throughput of the wearable devices with electrodes size 10 mm in diameter, we implemented single electrode fabrication using printed circuit boards (PCBs) and depositing gold (Au) and TiN on the plated side of PCBs utilizing the sputtering tool. This step was followed by the assembly of those single electrodes on the flexible 3D printed device. We showed that the TiN electrode material performed better in terms of charge storage capacity and charge injection capacity than the widely used stainless steel electrode material …

This study presents a viable strategy using fmoc-protected peptides hydrogels, to encapsulate and stretch mesenchymal stem cells (MSC). To explore the peptide hydrogel potential, a custom mechanical stretching device with polydimethylsiloxane (PDMS) chambers were used to stretch MSCs encapsulated in Fmoc hydrogels. We investigated the impact of fmoc- FF prepared in dimethyl sulfoxide (DMSO), 1,1,1,3,3,3-hexafluoro-2-propanol (HFP) and deionizied water in the self-assembly, and mechanical properties of the gels. The peptide hydrogel is formed through molecular self-assembly of peptide sequence into β-sheets that are connected with the π-π aromatic stacking of F-F groups. The hydrogels provided a stiff, hydrated gel with round nanofiber morphology representing an elastic modulus of 174-266 KPa. MSCs cultured on peptide hydrogels undergo viability, morphology, and alignment evaluations using MTT, live/dead, and phalloidin (F-actin) staining. The F-actins of 3D- cultured MSCs in Fmoc-FF/HFP, and Fmoc-FF/DMSO followed by mechanical stretching showed elongated morphology with defined microfilament fibers compared to the round and spherical F-actin shape of the control cells. Peptide gels with 5mM concentration preserved 100% viability of MSC. Results reveals the feasibility and conditions for successful cell encapsulation and alignment within peptide hydrogels. Encapsulation of MSC in peptide nanofiber followed by a stretching process present a promising …

Layer-by-layer (LBL) polyelectrolyte capsules can be modified to incorporate stimuli such as superparamagnetic nanoparticles which respond to a magnetic field only when it is turned on. Thus, they can act as a switch to load or unload their drug cargo on demand. Specifically, magnetite is incorporated into bilayer capsules made of alternating poly(allylamine hydrochloride) (PAH) and poly(sodium-p-styrenesulfonate) (PSS) which surrounds calcium carbonate core. The core is then dissolved using ethylenediaminetetraacetic acid (EDTA). These capsules are loaded with at FITC-BSA conjugate and examined with fluorescence to show the unloading of the FITC-BSA from capsules as it brightens the entire field of view of the microscope. The results suggest that we can next load and unload an anticancer drug such as doxorubicin using the combination of microcapsule and alternating magnetic field (AMF) to treat the cancer cells. Preliminary data interprets that the low frequency AMF we use has little to no adverse effect cells viability. This coincides with the general thought that low frequency AMF signals are not harmful to humans. Therefore, as an alternative to hyperthermia methods which use heat, it may be possible to deliver the anticancer drugs specifically to the cells when and where it is needed.