Biological products, such as proteins and nucleic acids, must often be separated from a solution as part of an industrial purification process. One approach to this separation is to pass the fluid containing the biological product through a membrane made of hydrogels. Hydrogels are a three-dimensional network of polymeric chains that are designed to absorb water-based solutions. Lignin, a plant-based polymer, can be incorporated into the hydrogel network to enhance the membrane's ability to capture biological molecules from the solution. However, there is relatively little information on how adding lignin to the hydrogel changes the three-dimensional structure of the resulting composite membrane. Additionally, conventional methods used to recover lignin from plant material results in low-purity lignin with unpredictable chemical structure. Using heterogeneous lignin in the production of hydrogel membranes will result in composite materials with ill-defined network structures, making it difficult to design membranes for real applications. The goal of this project is to clarify how introducing lignin into hydrogels influences the resulting structure. The project will make use of a new lignin purification process to obtain ultraclean lignin with controlled molecular architecture. By systematically varying the polymeric hydrogel structure with lignin, fundamental relationships between membrane structure, molecular interactions, and protein transport through the membrane will be uncovered. The anticipated outcomes of this project have the potential substantially impact next-generation materials fabrication strategies by establishing parameters for predictive materials design of novel, composite hydrogels. Composite hydrogel membranes are finding use in applications ranging from biological molecule separation, tissue engineering, to protein delivery. The research efforts are closely tied to educational outreach initiatives that aim to engage and inspire the next generation of engineers and scientists through the development of a 'membrane module' related to bioseparations and water purification.

The aim of the proposed research is to uncover the fundamental transport principles and key network structure-property relationships underlying the protein separation and immobilization performance of an emerging class of novel, lignin-based hydrogels. This aim will be achieved by leveraging fractionated lignins of low dispersity and controlled molecular weights to systematically vary the network structure (i.e., mesh size) of the composite hydrogels. By tuning both the chemical functionality and the molecular weight of the lignins, the role of both structure and molecular-scale interactions on membrane performance can be elucidated. The lignin fractions will be modified with functional groups that allow them to participate in the crosslinking reaction that forms the network structure of the hydrogel. The separation/binding efficiency of various biomacromolecules from the composite membranes will be investigated using a combination of in situ permeation experiments with longer-term, 'bind-and-release' experiments. The water transport and hydrated mechanical properties of composite membranes will be characterized using a mechanics-based technique, poroelastic relaxation indentation. Using a Darcy's law framework, the average mesh (pore) size of the hydrated network structure can be determined. The structure of the hydrated membranes will be independently characterized using small-angle neutron scattering, and the results will be compared to those obtained from indentation experiments. Additionally, molecular-level interactions between the biomacromolecules and the composite hydrogels, as well as protein dynamics within the membrane, will be captured using infrared spectroscopy and quasi-elastic neutron scattering, respectively. These findings have the potential to impact the design of new materials in several other membrane-based separations processes, such as materials for water purification and desalination. Finally, the research component of this proposal is closely tied to STEM-based outreach objectives that seek to integrate findings and materials from this research into departmental outreach efforts related to bioseparations and water purification.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Project Start
Project End
Budget Start
2019-08-15
Budget End
2022-07-31
Support Year
Fiscal Year
2019
Total Cost
$465,746
Indirect Cost
Name
Clemson University
Department
Type
DUNS #
City
Clemson
State
SC
Country
United States
Zip Code
29634