Biomaterials and AFM
AFMs excel in the characterization of samples at the interface of materials and biology. AFM is unique in measuring quantitative three-dimensional specimen surface topography and mechanical data in a single tool and it can operate in the specific gas or liquid environment where the biomaterial fulfills its function. Statistical quantities of the specimen topography (e.g. roughness) and mechanical parameters (e.g. phase imaging and force-distance curves) can be measured and used to verify processes at the nanoscale. The AFM also differentiates itself from transmission and scanning electron microscopy (TEM/SEM) by simpler, nontoxic specimen preparation, ease of use, and substantially lower cost (you can buy one of our AFMs for the cost of an annual TEM maintenance contract).
An example: Filtration membranes, filtrate and filter cake analysis
Filtration membranes fall into the biomaterials category and are ubiquitous in water and air filtration both in everyday life and in laboratory applications. Despite standard labels listing pore sizes and solvent compatibility, the underlying structure can vary dramatically and cause differences in performance among “identical” membranes. Atomic force microscopy (AFM) is the ideal tool to compare and control micro- and nanoscale features before, and after use of the membrane.
New polycarbonate membrane with line profiles.
Pore line profiles vs. specified pore size.
Polycarbonate filtration membrane after filtering 2% milk.
High resolution images of casein micelles in the filter cake.
See application note AFM of Filtration Membranes for more data.
An example: Functionalizing surfaces for bioassays
Substrate-based bioassays fall squarely into the biomaterials category. A key aspect in their production and quality control is the performance of the substrate before functionalization. Many QC assays rely on spectroscopic methods, which give no information on the actual distribution of features. The AFM is very useful to scan the substrate before and after, and can identify surface contaminations with phase imaging (which the AFM can acquire simultaneously with topography).
Polymer substrate before cleaning in topography showing a range of nanoscale features.
Polymer substrate before cleaning in phase, clearly identifying a droplet contamination by a difference in stiffness.
Scratched substrate after ethanol wipe.
Statistical surface quantities after ethanol wipe.
See application note Phase Imaging with AFM for more data.
Atomic force microscopy setups
Three AFM setups are of interest for the characterization of biomaterials depending on the specific experimental requirements. The MolBio3D benchtop system excels at rapid imaging of dry samples especially for quality control purposes. The HR-AFM accepts broader sample geometries and allows for scanning in liquids at the expense of floor space in the lab. The LS-AFM allows the user to correlate light microscopy techniques and AFM measurements in a dedicated system.
