Kinetic Method of Producing Pores Inside Protein-Based Biomaterials without Compromising Their Structural Integrity

Mechanical Unfolding of Network Nodes Drives the Stress Response of Protein-Based Materials

Biomaterials synthesized from cross-linked folded proteins have untapped potential for biocompatible, resilient, and responsive implementations, but face challenges due to costly molecular refinement and limited understanding of their mechanical response. Under a stress vector, these materials combine the gel-like response of cross-linked networks with the mechanical unfolding and extension of proteins from well-defined 3D structures to unstructured polypeptides. Yet the nanoscale dynamics governing their viscoelastic response remains poorly understood. This lack of understanding is further exacerbated by the fact that the mechanical stability of protein domains depends not only on their structure, but also on the direction of the force vector. To this end, here we propose a coarse-grained network model based on the physical characteristics of polyproteins and combine it with the mechanical unfolding response of protein domains, obtained from single molecule measurements and steered molecular dynamics simulations, to explain the macroscopic response of protein-based materials to a stress vector. We find that domains are about 10-fold more stable when force is applied along their end-to-end coordinate than along the other tethering geometries that are possible inside the biomaterial. As such, the macroscopic response of protein-based materials is mainly driven by the unfolding of the node-domains and rearrangement of these nodes inside the material. The predictions from our models are then confirmed experimentally using force-clamp rheometry. This model is a critical step toward developing protein-based materials with predictable response and that can enable applications for shape memory and energy storage and dissipation.

Aided Porous Medium Emulsification for Functional Hydrogel Microparticles Synthesis

Despite the substantial advancement in developing various hydrogel microparticle (HMP) synthesis methods, emulsification through porous medium to synthesize functional hybrid protein-polymer HMPs has yet to be addressed. Here, the aided porous medium emulsification for hydrogel microparticle synthesis (APME-HMS) system, an innovative approach drawing inspiration from porous medium emulsification is introduced. This method capitalizes on emulsifying immiscible phases within a 3D porous structure for optimal HMP production. Using the APME-HMS system, synthesized responsive bovine serum albumin (BSA) and polyethylene glycol diacrylate (PEGDA) HMPs of various sizes are successfully synthesized. Preserving protein structural integrity and functionality enable the formation of cytochrome c (cyt c) - PEGDA HMPs for hydrogen peroxide (H2O2) detection at various concentrations. The flexibility of the APME-HMS system is demonstrated by its ability to efficiently synthesize HMPs using low volumes (≈50 µL) and concentrations (100 µm) of proteins within minutes while preserving proteins' structural and functional properties. Additionally, the capability of the APME-HMS method to produce a diverse array of HMP types enriches the palette of HMP fabrication techniques, presenting it as a cost-effective, biocompatible, and scalable alternative for various biomedical applications, such as controlled drug delivery, 3D printing bio-inks, biosensing devices, with potential implications even in culinary applications.

Toward Tunable Protein-Driven Hydrogel Lens

Despite the significant progress in protein-based materials, creating a tunable protein-activated hydrogel lens remains an elusive goal. This study leverages the synergistic relationship between protein structural dynamics and polymer hydrogel engineering to introduce a highly transparent protein-polymer actuator. By incorporating bovine serum albumin into polyethyleneglycol diacrylate hydrogels, the authors achieved enhanced light transmittance and conferred actuating capabilities to the hydrogel. Taking advantage of these features, a bilayer protein-driven hydrogel lens that dynamically modifies its focal length in response to pH changes, mimicking the adaptability of the human lens, is fabricated. The lens demonstrates durability and reproducibility, highlighting its potential for repetitive applications. This integration of protein-diverse biochemistry, folding nanomechanics, and polymer engineering opens up new avenues for harnessing the wide range of proteins to potentially propel various fields such as diagnostics, lab-on-chip, and deep-tissue bio-optics, advancing the understanding of incorporating biomaterials in the optical field.

What Is the Force-per-Molecule Inside a Biomaterial Having Randomly Oriented Units?

Both synthetic and natural protein-based materials are made of randomly oriented cross-linked molecules. Here we introduce a coarse-grained approach to estimate the average force-per-molecule for materials made from globular proteins. Our approach has three steps: placement of molecules inside a unit volume, cross-linking, and trimming to remove the protein domains that do not participate to the force response. Following this procedure, we estimate the number of active domains per cross-section area, that allows for a direct calculation of the force-per-domain. Among the variables considered, we found that concentration was the most sensitive parameter. We then synthesized protein hydrogels made from BSA and polyprotein L and measured the stresses that these materials can withstand. We found that forces-per-molecules of up to 17 pN per domain can be obtained experimentally using protein hydrogels. Our approach represents an important step toward understanding the scaling of tension in biomaterials.