| AVS 62nd International Symposium & Exhibition | |
| Biomaterial Interfaces | Monday Sessions |
| Session BI+AS-MoM |
| Session: | Characterization of Biological and Biomaterials Surfaces (1) |
| Presenter: | Daniel Barlow, Naval Research Laboratory |
| Authors: | D.E. Barlow, Naval Research Laboratory J.C. Biffinger, Naval Research Laboratory A.L. Cockrell, Nova Research M. Lo, Anasys Instruments K. Kjoller, Anasys Instruments D. Cook, Anasys Instruments W. Kyung Lee, Naval Research Laboratory P.E. Pehrsson, Naval Research Laboratory W.J. Goodson, Air Force Research Laboratory J.N. Russell, Jr., Naval Research Laboratory |
| Correspondent: | Click to Email |
Synthetic polymers can be prone to degradation in microbial and other biological environments, often through enzymatic activity. Quantitative assays are important to characterize these degradation mechanisms and accurately correlate relationships with environmentally dependent microbial physiology. For microbial degradation of polyurethane films, conventional FTIR microscopy has been previously applied in quantitative assays with micron – scale spatial resolution. Photothermal AFM-IR offers the potential to extend this analysis to the nanoscale, allowing early degradation processes and mechanisms relative to single microbes to be quantified. As a first step towards this, we have used AFM-IR to characterize a known polyurethane degrading microbe (Pseudomonas fluorescens, Pf01) grown on films of a polyether – polyurethane (PU) formulation known to resist enzymatic degradation. This allowed us to conduct preliminary AFM-IR assessments with a relevant microbe and polymer, but without additional complications from biodegradation. Height images of air-dry samples showed the growth procedure in liquid media resulted in monolayer Pf01 biofilm clusters on top of the ~250 nm PU layer, providing a conducive model system for AFM-IR in an ATR configuration. Both bacteria and PU spectral signatures were detectable by AFM-IR spectroscopy and showed generally good agreement with FTIR. However, PU AFM-IR absorption intensities were observed up to 2x higher in regions covered by dried bacteria, versus uncovered regions, even though the PU thickness was uniform over the substratum. This was due to damping variations which were reflected in the cantilever ring-down and attributed to differences in loss modulus and tip – sample adhesion for the two materials. This shows that local cantilever damping can be an important property to assess in AFM-IR analysis of combined biological / polymer samples, a factor that has received little attention thus far. Analysis of the cantilever ring-down will be discussed regarding extraction of damping parameters for normalization of the IR signal.