Chemotaxis or cell motility in response to chemical gradients plays a central role in several physiological and pathological processes such as organ development, tissue repair, wound healing, cellular immunity. The cell speeds vary from a few microns per hour, managed by crawling stem cells to several hundred microns per second, achieved by swimming sperm. Microfluidic devices support the generation of stable as well as rapidly switchable chemical gradients. These devices facilitate not only increased precision in measurements on individual cells but also multiplexing capability for statistical estimates of population behavior. We are focused on designing robust microfluidic devices that support stable chemical gradients in the presence of pressure / flow fluctuations. To this end we employ computer simulations to screen and optimize designs that provide superior performance over a range of flow rates. The screened designs are then microfabricated using soft lithography techniques and subjected to experimental validation.
Liposomes are nanometer scale spherical vesicles of phospholipid bilayers and have been used as carriers for delivery of several drugs. While several liposome encapsulated drugs are already on the market, their full potential remains to be realized. Some of the limitations include poor encapsulation efficiencies for certain drugs, difficulties related to site-specific targeting and controlled / triggered release as well as challenges associated with evasion of the reticulo-endothelial clearance as well as lysosomal degradation. Our efforts are concentrated towards optimizing the drug carrier by estimating the effects of drug interaction with the bilayer on liposome stability. To this end, we employ microaspiration technique to estimate properties such as moduli for bilayer expansion and bending, bilayer rupture force and bilayer permeability. Several drug-phospholipid compositions are screened for optimal performance parameters such as stability and drug release kinetics.