(723g) Biofilm Formation of Candida Albicans On Nanofiber Textured Surfaces

Introduction:
Medical implants are susceptible to
infection caused by microorganisms that adhere to the surface and form
biofilms. Biofilms consist of extracellular polymeric substance which protects
the embedded microbial cells from the antimicrobials. Due to the high cost of surgical
replacements and ineffectiveness of long-term antibiotic as treatments, a new method is needed. The new research direction for
anti-biofilm surfaces have been prompted by the anti-fouling
topographies of marine organisms. Our research involves interaction between microorganism
and bio-inspired submicron topographic features on surface. In the work presented here, we
investigate the effect of surface topography feature size and shear stress on
biofilm formation and differentiation of Candida albicans, a model
organism for fungal infection.

Materials and Methods:

Sample Fabrication- Nanofiber-textured
model surfaces were fabricated by depositing a single layer of highly aligned
and isodiametric polystyrene nanofibers on 45 mm² flat polystyrene
substrates. The Spinneret based Tunable Engineered Parameters (STEP) nanofiber
manufacturing platform developed by Nain et al. was utilized to make the
polystyrene nanofibers (diameter = 750 nm; separation distance = 2000 nm –
3000 nm). Three different types of surfaces were manufactured for the
experiment; smooth (control), single layer, and crisscross double layer. The
scanning electron microscopy (SEM) images of single and double layer fiber
surfaces are shown in Figure 1.

Biofilm Growth Assay- All samples
were soaked in fetal bovine serum (FBS) overnight prior to the biofilm growth
assay in order to condition the surface to mimic the natural environment of the
microorganism. Candida albicans (C. albicans) SC5314, a model
human fungal pathogen, was used in this study. Dynamic retention assay was
conducted by placing the smooth (control) and the nanofiber-textured surfaces
on the sample holder bars of a center for
disease control (CDC) biofilm reactor and
exposing them to a suspension of 1•10⁵ CFU/ml of C. albicans
in yeast nitrogen base (YNB) media with 50 mM dextrose. After 24 hours of
growth at 37°Æ C and 80 RPM (1.6 dyne/cm²), the cells are detached
from the surfaces and counted using serial dilution and standard plate count
method.

Results and Discussion: Our preliminary experimental results shown in Figure 2
suggest that the minimum experimental
adhesion density occurs for samples with single
layer nanofiber texture. When compared to the smooth surface, the adhesion
density for these samples is reduced by approximately 24%.  Unlike the
single layer surface, the double layer nanofiber surface increased the cell
adhesion by 170% when compared to the smooth surface.

 Conclusions: Our results indicate that a
highly aligned single layer of nanofiber texture significantly delays biofilm
formation of C. albicans, and is therefore a potentially effective way
to minimize the pathogenic effect of this organism. The shear stress of common implant
devices that are affected by C. albicans are shown in Table 1. Our
current and future experiments are focused on conducting pathogenicity assays
and optimizing the nanofiber texture parameters for maximum delay in biofilm
formation under different physiologically relevant shear stresses.