Surface Engineering

Porous Silicon Biomaterials

Porous silicon (pSi) is a non-toxic and biodegradable material with interesting optical properties, showing photoluminescence, interferometric and photonic effects. PSi is produced during anodic galvanostatic, chemical, or photochemical etching of monocrystalline silicon in the presence of hydrofluoric acid (HF). Depending on the etching condition, different nanostructured architectures arise, which in general are comprised of unidirectionally aligned pores that are generally perpendicular to the surface.

 

We are using biodegradable pSi as a scaffold for the transfer of primary cells and stem cells, including limbal stem cells. We are also investigating drug delivery focusing on treating ocular diseases.

 

Figure 1. Cell outgrowth from a corneal rim explant on a thermally-oxidised, aminosilanised porous silicon membrane after two weeks. Large cells (L), cells with the morphology of fibroblasts (F) and small cuboidal cells (C) were visible in the population. Cells were stained with DiOC5(3). Scale bar: 150 µm.

Furthermore, we are using pSi-based topography and chemistry gradients to investigate the influence of surface chemistry and topography on cell behaviour.

 

Figure 2. Morphological analysis of neuroblastoma cells. Laser scanning confocal microscopy (cells stained with Hoechst 33342 and Alexa Fluor® phalloidin conjugate) after 24 hours of growth on (a) 1000-3000nm, (c) 300-1000nm, (e) 100-300nm, (g) 50-100nm, (i) 20-50nm, (k) 5-20nm porous silicon regions and (m) flat silicon. Corresponding SEM micrographs of cells growing on (b) 1000-3000nm, (d) 300-1000nm, (f) 100-300nm, (h) 50-100nm, (j) 20-50nm, (l) 5-20nm porous silicon regions and (n) flat silicon are shown on the right.

We also use surface-initiated polymerizations and electrospinning to prepare pSi polymer composites which combine the benefits of both materials. The use of composite materials may help improve drug resistance to first pass metabolism and degradation in vivo and increase the bioavailability at the site of delivery.

Figure 3. SRA cells seeded on composite material made from pSi and poly(caprolactone).