Fabrication of electrospun meshes from natural polymers for biomedical applications

Naik, B. Reddy Prasad and Samavedi, S (2018) Fabrication of electrospun meshes from natural polymers for biomedical applications. Masters thesis, Indian Institute of Technology Hyderabad.

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Abstract

Diabetic retinopathy (DR) involves a progressively worsening cycle of microglial cell activation and inflammation that leads to severe retinal damage. While the inflammatory nature of DR is well-established, the exact role of microglial cells in contributing to disease progression is not clear. Towards the long-term goal of creating in vitro platforms to understand microglial cells responses in health/disease, the objective of this work is to create electrospun substrates from natural polymers with systematically varying properties for the in vitro culture of microglial cells. Accordingly, gelatin and composite nanofibers with different diameters and architectures were successfully electrospun. Increasing the concentration of gelatin in solution resulted in a slight increase in fiber diameter. Concurrently, a 10% (w/v) gelatin solution was mixed with 10% polycaprolactone (PCL) solution at a ratio of 50:50 and electrospun to produce gelatin/ PCL composite nanofibers. In a parallel study, fiber architecture was varied by changing the collector geometry. While randomly oriented gelatin and PCL fibers (with angular standard deviation >50°) were generated by electrospinning onto a flat plate collector, semi-aligned (with angular standard deviation >30°) and highly aligned fibers (with angular standard deviation <20°) were collected by using a drum collector rotating at 750 rpm and 1500 rpm respectively. To improve the stability of gelatin in aqueous environments, nanofibers were crosslinked with glutaraldehyde (GTA) vapor at room temperature for different time periods, namely 2h, 6h, 12h and 24h. While the non-crosslinked control fibers almost entirely degraded within 1 day of exposure to aqueous buffer at 37 °C, fibers crosslinked with GTA for 2h or more remained stable for at least four days in buffer, indicating that 2h was sufficient to retard degradation. Culture of primary mixed retinal cells on randomly oriented and aligned fibers resulted in randomly oriented and highly aligned vimentin and cell nuclei. In summary, the work demonstrates that the properties of gelatin meshes can be changed by systematically varying electrospinning parameters. In the future, the effects of fiber diameter and chemistry on cell phenotypic activation will be studied. Furthermore, fibers will be tethered with cytokines that can be released in a controlled manner through fiber degradation.

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