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Yes / This study investigated adsorption kinetics, adsorption equilibrium, and adsorption isotherm of three dyes [i.e., methylene blue (MB), rhodamine-B (RB), and safranin T (ST)] onto polyacrylonitrile (PAN) and ethanolamine (EA) grafted PAN nanofibers (NFs) membranes (EA-g-PAN). The membranes were characterized by field emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FT-IR) spectroscopy, and Brunauer–Emmet–Teller (BET). FE-SEM showed a smooth morphology for the NFs before and after grafting, while FT-IR confirmed EA grafting into the nitrile group of PAN. The grafting percentage with no change in the physical nature of the membrane was 12.18%. The nitrogen adsorption–desorption isotherms for PAN and EA-g-PAN NFs membranes were similar and classified as a Type IV according to the International Union of Pure and Applied Chemistry. The surface area, pore-volume, and pore size of the EA-g-PAN increased to 21.36 m2 g−1, 0.16 cm3 g−1, and 304.93 Å, respectively. The pores were cylindrical mesopores with bimodal openings, which means that pores were open at both ends. The adsorption of the MB, RB, and ST dyes onto the PAN and EA-g-PAN NFs membranes leveled off at ~ 60 min. The adsorption kinetics showed good fitting to pseudo-second-order kinetic model and multi-step diffusion process. The order of the dye adsorption was PAN / the Deanship of Scientific Research, King Saud University [RG-1440-060]

Contact inhibition of locomotion (CIL), a migratory mechanism, first introduced by Abercrombie and Heaysman in 1953 is now a fundamental driving force in developmental, repair and disease biology. Much of what we know of CIL stems from studies done on 2D substrates which are unable to provide the essential biophysical cue of fibrous extracellular matrix curvature. Here we inquired if the same rules are applicable for cells attached to and migrating persistently on suspended and aligned ECM-mimicking nanofibers. Using two elongated cell shapes (spindle attached to one fiber, and parallel attached to two fibers), we quantitate CIL rules for spindle-spindle, parallel-parallel and spindle-parallel collisions. Two approaching spindles do not repolarize upon contact but rather continue to migrate past one another. Contrastingly, approaching parallel cells establish distinct CIL, with only one cell repolarizing upon contact followed by migration of both cells as a cohesive unit in the repolarization direction. Interestingly, for the case of spindle and parallel cell collision, we find the parallel cell to shift the morphology to that of spindle and continue persistent movement without repolarization. To account for effect of cell speed, we also quantitate CIL collisions between daughter and non-dividing cells. While spindle-spindle collisions result in cells still walking by, for parallel-parallel collisions, we capture rare events of a daughter cell pushing the non-dividing cell. With increasing population numbers, we observe formation of cell streams that collapse into spheroids. Single cells are able to invade along fibers from the spheroids and are then subject to same CIL conditions, thus providing a platform with cyclic CIL. The presented coupling of experimental and analytical framework provides new insights in contextually relevant CIL and predictive capabilities in cell migration decision steps. / Master of Science / Contact inhibition of locomotion (CIL) is a migratory process that can lead to a change in migration direction through protrusion inhibition of single cells. First described in 1953, the traditional model of CIL shows that on a 2D substrate, two migrating cells experience a decrease in protrusive behavior upon contacting each other, followed by repolarization, and migration away from one another. However, a cell's extracellular matrix (ECM) is fibrous in nature, and how cells maintain standard CIL rules in fibrous environments remains unclear. Here, using suspended, aligned nanofibers created using a non-electrospinning Spinneret based Tunable Engineered Parameters (STEP) method, we investigate CIL decision steps of two fibroblast cells approaching each other in two shapes: spindle cells attached to single fibers, and parallel cells attached to two fibers. Most spindle cells approaching each other do not switch direction upon contact, but rather continue to migrate past each other, termed a walk past. Contrastingly, approaching parallel cells display unique CIL whereby only one cell repolarizes and reverses its migration direction. Subsequently, both cells remain in contact while migrating in the repolarization direction. Interestingly, we report that both spindle and parallel CIL are also affected by speed post cell division. Altogether, for the first time, we introduce a platform to understand cell shape driven CIL geometrical rules in ECM mimicking environments.

Spinneret based Tunable Engineered Parameters (STEP) Platform is a recently reported pseudo-dry spinning and non-electrospinning technique that allows for the deposition of aligned polymeric nano-fibers with control on fiber diameters and orientation in single and multiple layers (diameter: sub 100nm micron, length: mm-cm), deposition (parallelism 2.5 degrees) and spacing (microns)). A wide range of polymers such as PLGA, PLA, PS, and PU have been utilized for their unique material properties in scaffold design. In this thesis two unique bioscaffolds are demonstrated for the measurement of group cell migration for wound closure and single cell contractility force for the study of force modulation. The wound healing assay bridges the gap between confluent reservoirs of NIH3T3 fibroblasts through arrangement of a suspended array of fibers guiding group cell migration along the fiber axis. This platform demonstrates that topographical and geometrical features of suspended fibers play a very important role in wound closure. Spacing, alignment and orientation were optimized to shown an increased rate of closure. In the second complementary assay, we report a fused-fiber network of suspended fibers capable of measuring single cell forces. Results from our experiments demonstrate that force behavior is dependent on mechanical properties such as stiffness and geometry of fiber networks. We also demonstrate changes in spatial and temporal organization of focal adhesion zyxin in response to single cell migration on these networks. / Master of Science