New Insights into Protein Behavior in Hydrogels Unveiled Using Near-Infrared Spectroscopy

In a recent study, researchers from China investigated the unfolding of ovalbumin (OVA) within hydrogels, which helped them discover new information about the role of water structure in protein conformational changes. The findings of this study, which were published in the International Journal of Biological Molecules, reveal how near-infrared (NIR) spectroscopy can contribute to protein and polymer analysis (1). The research team was led by Xueguang Shao from Nankai University and Beijing University of Technology, and the team was comprised of researchers from these two institutions as well as Beijing Inno Medicine Co., Ltd.

OVA is a glycoprotein often used in biochemical studies (1,2). This glycoprotein is found in egg whites, and it is used for drug and pharmaceutical processing (2). In this study, Shao and the team concentrated their efforts on learning more about the behavior of OVA when it is condensed in poly(N, N-dimethyl acrylamide) (PDMAA) hydrogel, which is a synthetic polymer known for its hydrophilic properties and biocompatibility (1). Through the use of advanced NIR spectroscopy techniques, which include continuous wavelet transform (CWT) and independent component analysis (ICA), the research team was able to monitor both protein unfolding and water structure dynamics over a range of temperatures (1).

The researchers uncovered several important findings. One of the main discoveries was that the α-helix structure of OVA undergoes a sharp decline at relatively low temperatures within the PDMAA hydrogel (1). This observation is important because it indicates that the hydrogel environment facilitates protein unfolding, a behavior that contrasts with what is typically observed in free aqueous solutions (1). The NIR spectral signature at 4851 cm⁻¹, associated with the α-helix conformation, served as a sensitive marker for this transition (1).

Another key finding was that changes in hydrogen-bonded water closely mirrored the unfolding process of the protein. The researchers believe this observation suggests a direct interaction between the hydration layer and the protein conformation (1). Using ICA, the researchers identified a novel water structure, referred to as “S₂ water,” which is characterized by two hydrogen bonds and is unique to the OVA-loaded PDMAA hydrogel system (1).

This novel water structure intrigued the researchers, and they thought it could be a double hydration shell, which means it interacts with the surface of the polymer as well as the methyl groups of the PDMAA polymer (1). According to the researchers, the ease with which this double hydration water dissociates may be the key to facilitating the structural transition from α-helix to β-sheet in the encapsulated protein (1).

Understanding protein chemistry is important when developing drug delivery systems. Hydrogels are widely explored as carriers for protein-based drugs because of their tunable properties and compatibility with biological tissues (1). Understanding how proteins unfold within these materials could help scientists design hydrogels that better preserve drug stability or, conversely, promote controlled release through triggered unfolding (1).

However, the researchers acknowledge that more research needs to be done. Their study revealed the discovery of the S2 water structure, which opens up pathways for future studies to investigate the regulatory role of water in protein conformation and hydrogel function (1). Their study also presented an approach that demonstrates the utility of advanced spectral analysis to extract subtle changes in protein and water behavior (1). These two critical points should be the focus of future studies on biomolecule–material interactions.

The biomedical field is continuing to grow, with an expected growth for biomedical engineers and bioengineers to grow 7% through 2033, which is faster than average for all occupations (3). As the biomedical field continues to push toward precision materials and targeted therapies, the insights gleaned from studies such as this one can be used to help create better therapeutics.

References

1. Ma, B.; Chen, N.; Cai, W.; et al. Understanding the Protein Conformation Transition Within Polymer Hydrogels Using a Near-infrared Water Spectroscopy Probe. Int. J. Biol. Mol. 2025, 290, 138995. DOI: 10.1016/j.ijbiomac.2024.138995
2. U.S. Biological, O8075 Ovalbumin CAS: 9006-59-1. US Bio. Available at: https://www.usbio.net/molecular-biology/O8075 (accessed 2025-04-08).
3. U.S. Bureau of Labor Statistics. Bioengineers and Biomedical Engineers. BLS.gov. Available at: https://www.bls.gov/ooh/architecture-and-engineering/biomedical-engineers.htm#tab-6 (accessed 2025-04-08).