Surface Modification and Characterization of Polylactic Acid (PLA) 3D printed structures for Cell culture applications.

P. Pokharna, M. Ghantasala, E. Rozhkova
Western Michigan University,
United States

Keywords: polylactic acid, 3D printing, surface modification, fluorescence imaging, Raman spectroscopy

Summary:

The main aim of this research is to understand the surface modification effects and improve the surface properties of 3D printed scaffolds that would be biocompatible and support the growth and proliferation of cells. Polylactic acid (PLA) structures were printed using Makerbot 3D printer, obtained from 3D printing Lab at Western Michigan University, and are used as the scaffold material. Two different surface modification methods, Hydrolysis and UV/Ozone are studied with the objective of introducing useful levels of carboxylic acid or primary and secondary amine groups, respectively, onto the surface of PLA. Also, gold thin film coating on PLA surface is used as another alternative for facilitating functionalization in a relatively simpler method. Hydrolysis (wet chemical etching) was performed by immersing the 3D printed PLA samples in 1 M NaOH/Etanhol solution for 24 hours. UV/Ozone treatment was performed on PLA samples for 20 min using Jelight UVO cleaner-144AX system. Plasma cleaned PLA surfaces were coated with 15nm thick Titanium seed layer and 50 nm thick gold layers using magnetron sputtering. All the above three surface modification techniques were tested on unpolished (Ra - 21 µm) & polished 3D printed surfaces (Ra – 2 µm) to study the effects of surface roughness on Protein Immobilization. After surface modification, surface functionalization on chemically etched & UVO treated PLA surface is carried out through EDC [1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride] crosslinking technique. Surface functionalization on gold thin film coated PLA samples is performed using SATA/DMSO solution along with Organic base following standard protocol. Poly-L-lysine-FITC Labelled protein is attached to the surface functionalized PLA samples. The Hydrolysis (wet chemical etching) method and UVO initiated grafting method led to a fall in contact angle from 82 degrees to 32 degrees & 62 degrees respectively, suggesting improved hydrophilicity on PLA surface. Raman Spectroscopy analysis was found to be difficult with samples having large roughness and higher porosity. However, Raman spectra on samples with optimized conditions showed the presence of protein on the surface. Upright Fluorescence microscopic images on functionalized PLA surfaces demonstrated successful immobilization of proteins. Further, these studies clearly showed better protein attachment on polished samples compared to unpolished chemically etched. This paper will discuss the results of these studies in detail.