Controlling antimicrobial activity and drug loading capacity of chitosan-based layer-by-layer films.

We report on layer-by-layer (LbL) films of chitosans (CHI) and hyaluronic acid (HA) whose properties could be controlled by employing chitosans with different degrees of deacetylation (DD¯ ≈ 85%; 65%; 40%) and high average molecular weight (ca. 106 g/mol). In spite of their high molecular weight, these chitosans are soluble within a wide pH range, including physiological pH. HA/CHI LbL films produced from polymer solutions at pH 4.5 were thinner, smoother, more hydrophilic than those prepared at pH 7.2. This is attributed to the more extended conformation adopted by chitosan due to its very high charge density at low pH, favoring a compact chain packing during the film formation and resulting in lower film thickness and roughness. The smoother HA/CHI LbL films obtained at pH 4.5 were effective against Escherichia coli, while the thicker, rougher LbL films fabricated at pH 7.2 could be used in the controlled released of Rose Bengal dye. In summary, the tuning of only two parameters, i.e. solution pH and DD¯ of chitosans, provides access to a library of HA/CHI LbL films for tailored, diversified applications.

Engineering the surface of prostate tumor cells and hyaluronan/chitosan multilayer films to modulate cell-substrate adhesion properties.

This paper explores different film assembly conditions of the polyelectrolyte solutions of hyaluronan (HA) and chitosan (CHI), as well as both substrate and cell surface modifications, to investigate PC3 cells adhesion properties. UV-Visible, AFM-IR and Zeta potential techniques indicate that the solution ionic strength is a relevant parameter to modulate the free carboxylic groups of HA on the film surface. In addition, capacitive coupling measurements suggest that assembly conditions that favor surface charge mobility inhibit cell adhesion due to polymer rearrangements that support non-specific electrostatic interactions of positively charged CHI residues and the negatively charged cell moieties, rather than specific CD44-hyaluronan interactions. Moreover, the PC3 cells treatment with hyaluronidase and anti-CD44 antibody also highlighted the importance of CD44 binding site availability on the tumor cell adhesion properties. Finally, the conjugation of wheat germ agglutinin on the film surface proved to be a suitable strategy to boost the PC3 cell adhesion properties. Our results reveal the remarkable capacity of HA/CHI films to modulate cell-substrate properties, which pave the road for the development of surfaces suitable for several applications based on biosensing.