Poster O3 - Strategic Modification of Carrageenan to Modulate Protein Binding

Introduction: This study investigates the strategic modification of carrageenan, a polysaccharide derived from red seaweed, to control protein binding to biomaterials surfaces. Protein binding to surfaces is a crucial determinant of subsequent biological processes on biomaterials, including cell attachment, blood clotting, and cellular inflammation. Tuning the surface chemistry of biomaterials is an important strategy for understanding and guiding these and many other important biological responses to medical devices and in tissue engineering applications. Carrageenans can be carboxymethylated and aminated, providing a library of new materials with a range of chemical functionality.
This work uses the layer-by-layer technique to prepare polysaccharide-based polyelectrolyte multilayers (PEMs), which can modify biomaterial surfaces. This technique can introduce nanoscale features an chemistries to biomaterials surfaces making it an excellent technique for developing new surface coatings. In this work, chitosan is used as the polycation, and modified carrageenans are used as polyanions. Using these chemically modified carrageenans in PEMs, we aim to demonstrate how the material chemistry and surface topography can be tailored to minimize adverse biological reactions and encourage favorable biological responses to surfaces.
This research contributes a new class of naturally derived biomaterials from modified carrageenans and demonstrates their utility for tuning biological responses that could activate healing mechanisms and reduce the need for delivering therapeutics from biomaterials surfaces to inhibit adverse reactions.

Materials and

Methods: In this experimental approach, a series of carboxymethylated and aminated carrageenans are synthesized. Carrageenans (kappa-, lambda, and iota-carrageenan, fig. 1) are carboxymethylated (CMKC, CMIC, and CMLC) using Williamson’s ether procedure with monochloroacetic acid (MCA). Multiple synthetic routes are also explored for amination of carraggenans (ACK, ALC, and AIC). These modifications give rise to carrageenans containing carboxymethyl and amine groups. These modified carrageenan polymers are then used to make chitosan-based polyelectrolyte multilayers (PEMs) and nanoparticles (PCNs), which are the testbed surfaces for biological response studies. PEMs are formed by sequentially exposing surfaces to solutions in the following order: polycation, rinse, polyanion, rinse, resulting in coatings with precise control over the layer number, thickness, and composition . PCNs are also included in PEMs to modulate the surface nanotopography. Nanotopgraphy is evaluated by atomic force microscopy, (Figure 2).
Biomolecule binding to PEM and PEM+PCN surfaces is evaluated through spectroscopic and quantitative techniques, including X-ray photoelectron spectroscopy (XPS) and enzyme-linked immunosorbent assays (ELISAs). The important blood proteins albumin and fibrinogen are evaluated, as well as lipopolysaccharides from E. coli. These studies test hypotheses about how surface chemistry influences biomolecule adsorption (Table 1).

Results, Conclusions, and Discussions: X-ray photoelectron spectroscopy (XPS) confirms the formation of PEMs and the adsorption of important biomolecules. Atomic force microscopy (AFM) details the roughness and heterogeneity of the surfaces that are important for cellular interactions. Moreover, water contact angle measurements indicated increased hydrophilicity ( < 90°) when strong polyanions are present at the PEM surfaces. Using spectroscopic ellipsometry, dry thicknesses ranging between 20 -30 nm were obtained, thus confirming the effectiveness of the layer-by-layer assembly.
Modulating protein adsorption through altered surface chemistry is correlated to additional cellular and biological outcomes, including blood clotting, macrophage polarization, and bacterial biofilm formation. These represent important biological phenomena driving the success or failure of implanted biomaterials that can be regulated through surface chemistry changes, as an alternative to systemic or local delivery of drugs.

The studies demonstrate the possibilities of a new library modified carrageenans in affecting biological responses to biomaterials surfaces through simple changes in surface chemistry. These materials offer biomaterials scientist the opportunity to improve biomaterial compatibility with blood and tissues. By modifying the chemical structure of carrageenans, we achieved modulated biomolecule adsorption characteristics that influence a wide range of important downstream biological phenomena. Carboxymethylated and aminated carrageenans are an important new class of materials for the development of biomedical device coatings and tissue engineering applications.

Acknowledgements (Optional): The funding for this work was provided by the National Science Foundation award number: 2313878.