A new method for modifying atomic force microscope (AFM) probe with polymer was proposed to estimate the interaction between Chitosan (CS)-coated poly (lactic-co-glycolic acid) (PLGA) polymer and mucin film. In this method, the mixture of polymers and its suitable volatile dissolvent were deposited on the AFM probe tip through a micropipette controlled by micromanipulator. After being dried, the polymer film forms on the probe tip. Several evaluation experiments show that using the new method, the AFM probe tip can be smoothly and uniformly coated with PLGA and CS with approximately same curvature radius as that of probe tip less than 500 nm. As a preliminary application of the proposed method, the interaction force between PLGA/CS and mucin film in air was investigated. It was revealed that when a PLGA probe is retracting from the mucin film, a repulsive force appeared; however, after the PLGA probe was further overcoated with CS, the force became attractive if the amount of CS was enough, such as at CS concentrations of 0.2% W/V. The observed force can be interpreted by the surface hydrophilic/hydrophobic characteristics of PLGA/CS and mucin film.
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