Polylactic acid (PLA) is a naturally produced biomaterial. Its ideal properties, such as biodegradability and biocompatibility, have made it a widely adopted material for a variety of purposes (e.g., 3D printing, food packaging, and numerous medical applications). As PLA grows in popularity, especially within the medical field, understanding its structural responsiveness to different types of biological entities becomes increasingly significant. PLA is a semi-crystalline polymer, meaning it displays regions of both amorphous and crystalline structures. This may be influential in interactions with bacteria. In this study, we investigated the roles of crystal structure and crystallinity of PLA at biointerfaces. To examine the bacterial activity at the PLA surface, we selected E. coli as our model bacterium. We prepared thicker films (thickness > 100 nm) and thinner films (thickness < 20 nm) through spin-casting on cleaned silicon wafers. We varied the degree of crystallinity by annealing our as-spun samples at 120 °C for 48 hours. We then characterized our samples using atomic force microscopy (AFM), differential scanning calorimetry (DSC), and grazing-incidence wide-angle X-ray scattering (GIWAXS). Bacterial attachment was analyzed by confocal microscopy using Hoechst 33342 (a cell-permeable dye) to visualize the total quantity of bacteria adhered to each surface. In addition, we utilized colony-forming unit (CFU) enumerations to assess the health of the E. coli after four hours of exposure to each of our sample types. These experiments tell us about the health of the bacteria and their reproductive abilities after interacting with our samples. We observed trends of crystalline surfaces hindering colony growth more than amorphous surfaces. Confocal microscopy displayed preliminary trends of E. coli adhesion. By combining CFU and confocal imaging techniques, we can assess bactericidal properties. Further studies will include quantitative and statistical analysis of E. coli attachment, specifically examining time dependence, surface roughness, and thickness. Additional details will be discussed during the presentation.
