Gradation of Porcine Bladder ECM in Hydrogels for Chronic Wound Treatment

Chronic, nonhealing wounds affect about 6.5 million individuals in the U.S., and often present as comorbidities of other prevalent conditions such as obesity and diabetes. Chronic wounds are characterized by a recurring inflammatory state without progression to the proliferation and remodeling stages of wound healing. Around $25 billion is spent annually on treatment of chronic wounds; however most traditional wound care approaches do not effectively encourage the physiological healing process. One emerging treatment option is extracellular matrix (ECM)-based wound dressings, which are composed of a network of proteins and other macromolecules that support and anchor cells within tissue. These dressings are typically composed of decellularized tissue derived from animal donors and provide a protein scaffold that mimics dermal ECM by facilitating cell adhesion. Most commercially available ECM-based dressings are dry, uniform sheets of ECM that provide a structural scaffold for cellular growth, but do not provide a physiologically relevant moisture balance or encourage cellular infiltration into the dressing as the wound heals. However, fibroblasts, which play a major role in wound healing, have been shown to migrate to regions of denser ECM concentrations, where they exhibit enhanced metabolic activity and proliferation. A UBM-based hydrogel will serve as an alternative wound dressing that will mitigate the issues with current ECM-based products. A hydrogel dressing offers a more physiologically relevant moisture balance to the site of the wound, while integrated structural cues will encourage fibroblast infiltration. Ultimately, this approach will increase the rate at which ulcers heal and prevent further deterioration of the wound site, in turn lessening the physical and financial burden on patients.Maryland Summer Scholars 201

Characterization of Tensioned PDMS Membranes for Imaging Cytometry on Microraft Arrays

Polydimethylsiloxane (PDMS) membranes can act as sensing elements, barriers, and substrates, yet the low rigidity of the elastomeric membranes can limit their practical use in devices. Microraft arrays rely on a freestanding PDMS membrane as a substrate for cell arrays used in imaging cytometry and cellular isolation. However, the underlying PDMS membrane deforms under the weight of the cell media, making automated analytical microscopy (and thus cytometry and cell isolation) challenging. Here we report the development of microfabrication strategies and physically motivated mathematical modeling of membrane deformation of PDMS microarrays. Microraft arrays were fabricated with mechanical tension stored within the PDMS substrate. These membranes deformed 20× less than that of arrays fabricated using prior methods. Modeling of the deformation of pretensioned arrays using linear membrane theory yielded ≤15% error in predicting the array deflection and predicted the impact of cure temperatures up to 120 °C. A mathematical approach was developed to fit models of microraft shape to sparse real-world shape measurements. Automated imaging of cells on pretensioned microarrays using the focal planes predicted by the model produced high quality fluorescence images of cells, enabling accurate cell area quantification (<4% error) at increased speed (13×) relative to conventional methods. Our microfabrication method and simplified, linear modeling approach is readily applicable to control the deformation of similar membranes in MEMs devices, sensors, and microfluidics

Characterization of Tensioned PDMS Membranes for Imaging Cytometry on Microraft Arrays

Polydimethylsiloxane (PDMS) membranes can act as sensing elements, barriers, and substrates, yet the low rigidity of the elastomeric membranes can limit their practical use in devices. Microraft arrays rely on a freestanding PDMS membrane as a substrate for cell arrays used in imaging cytometry and cellular isolation. However, the underlying PDMS membrane deforms under the weight of the cell media, making automated analytical microscopy (and thus cytometry and cell isolation) challenging. Here we report the development of microfabrication strategies and physically motivated mathematical modeling of membrane deformation of PDMS microarrays. Microraft arrays were fabricated with mechanical tension stored within the PDMS substrate. These membranes deformed 20× less than that of arrays fabricated using prior methods. Modeling of the deformation of pretensioned arrays using linear membrane theory yielded ≤15% error in predicting the array deflection and predicted the impact of cure temperatures up to 120 °C. A mathematical approach was developed to fit models of microraft shape to sparse real-world shape measurements. Automated imaging of cells on pretensioned microarrays using the focal planes predicted by the model produced high quality fluorescence images of cells, enabling accurate cell area quantification (<4% error) at increased speed (13×) relative to conventional methods. Our microfabrication method and simplified, linear modeling approach is readily applicable to control the deformation of similar membranes in MEMs devices, sensors, and microfluidics