Figure 5.

Addition of CNF to the PLGA substrate alters the topography of the material. Using an Asylum MFP three-dimensional atomic force microscope (scan rate 1.0 Hz, AC mode with 256 × 256 scan points and lines), (A) CNF are shown for a 25:75 ratio (PLGA:CNF [wt%:wt%]) sample with a PLGA density of 0.025 g/mL which increases surface nanometer features as well as the total substrate surface area as compared with an etched glass cover slip. (B) It is shown for all PLGA:CNF ratio samples that increasing the CNF weight ratio increased the surface area of the substrate by creating nano, submicron, and micron features. (C) By normalizing the protein adsorption OD readings to the lowest reading (ie, for the controlled etched glass coverslip) and comparing it with the surface area percent increase, the results indicate that protein saturation was around 40%–55% of amount of increase of the surface area, and provide evidence that increasing the surface area (through addition of CNF) allows more proteins to attach to the surface to promote cell attachment. (D) Calculating the normalized protein adsorption capacity indicates that the 75:25 and 50:50 ratios (PLGA:CNF [wt%:wt%]) had the highest ability to attach the most proteins to a particular surface, indicating that one of the mechanisms regulating cardiomyocyte interactions is increasing material protein capacity through altering topographical features by addition of CNF.

Notes: This is evident in the similar cardiomyocyte growth trends reported by Stout et al.¹⁵ *P < 0.05 CNF wt% in materials versus 0% CNF wt% in materials; **P < 0.05 CNF wt% in materials versus 75% CNF wt% in materials; ***P < 0.05 CNF wt% in materials versus 50% CNF wt% in materials; ****P < 0.05 CNF wt% in materials versus 75% CNF wt% in materials, and *****P < 0.05 CNF wt% in materials versus 100% CNF wt% in materials. Data are shown as the mean count of n = 3.

Abbreviations: CNF, carbon nanofibers; OD, optical density; PLGA, poly(lactic-co-glycolic-acid).