Biology subjects

Pashuck, E. T.

Publications and source records attributed to Pashuck, E. T..

6 recordsLinked to original sources

bioRxiv2025

Design and Synthesis of Peptide-Polyester Conjugates for Cell-Mediated Scaffold Degradation

Biodegradable thermoplastic polyesters are promising biomaterials for tissue engineering due to their processability and mechanical properties. Polycaprolactone (PCL) is particularly attractive for load-bearing applications but does not degrade at the same rate as new tissue formation, which may compromise functional regeneration. This study presents a strategy for cell-mediated scaffold remodeling by incorporating a protease-cleavable peptide directly into the PCL backbone. Linear peptide-PCL conjugates were synthesized with poly(ethylene glycol) (PEG) spacers flanking the peptide to enhance protease access. A functional proteomics approach was used to identify a fast-degrading peptide sequence (Fast) selectively cleaved by multiple cell types. Conjugates containing Fast or its scrambled control (ScrFast) were combined with an RGDS-PCL conjugate and fabricated into scaffolds. Including Fast and ScrFast peptides did not impair cell adhesion to the scaffolds. Cy3 labeling enabled real-time quantification of scaffold degradation in the presence of collagenase or human mesenchymal stromal cells (hMSCs). Fast-PCL scaffolds degraded significantly faster than ScrFast-PCL in both conditions, demonstrating sequence-dependent and cell-directed resorption. Integrating protease-sensitive peptides into the polymer backbone is therefore an effective approach to fabricate solid scaffolds that degrade in response to cells. This platform can be adapted to couple cellular processes to scaffold remodeling to enhance tissue regeneration.

bioengineering↗

bioRxiv2025

Biocompatible Composite Hydrogel with On-Demand Swelling-Shrinking Properties for 4D Bioprinting

Hydrogels with tunable swelling and shrinking properties are of great interest in biomedical applications, particularly in wound healing, tissue regeneration, and drug delivery. Traditional hydrogels often fail to achieve high swelling without mechanical failure. In contrast, high-swelling hydrogels can absorb large amounts of liquid, expanding their volume by 10-1000 times, due to low crosslink density and the presence of hydrophilic groups. Additionally, some high-swelling hydrogels can also shrink in response to external stimuli, making them promising for applications like on-demand drug delivery and biosensors. An emerging application of high-swelling hydrogels is four-dimensional (4D) printing, where controlled swelling induces structural transformations in a 3D printed construct. However, current hydrogel systems show limited swelling capacity, restricting their ability to undergo significant shape changes. To address these limitations, we developed a high-swelling composite hydrogel, termed SwellMA, by combining gelatin methacryloyl (GelMA) and sodium polyacrylate (SPA). SwellMA exhibits a swelling capacity over 500% of its original area and can increase its original water weight by 100-fold, outperforming existing materials in 4D bioprinting. Furthermore, SwellMA constructs can cyclically swell and shrink on-demand upon changing the ionic strength of the aqueous solution. Additionally, SwellMA demonstrates superior cytocompatibility and cell culture properties than SPA, along with excellent 3D printing fidelity. These findings demonstrate SwellMAs potential for advanced 4D printing and a broad range of biomedical applications requiring precise and dynamic control over hydrogel swelling and shrinking.

bioengineering↗

bioRxiv2024

A Streamlined High-Throughput LC-MS Assay for Quantifying Peptide Degradation in Cell Culture

Peptides are widely used in biomaterials due to their easy of synthesis, ability to signal cells, and modify the properties of biomaterials. A key benefit of using peptides is that they are natural substrates for cell-secreted enzymes, which creates the possibility of utilizing cell-secreted enzymes for tuning cell-material interactions. However, these enzymes can also induce unwanted degradation of bioactive peptides in biomaterials, or in peptide therapies. Liquid chromatography-mass spectrometry (LC-MS) is a widely used, powerful methodology that can separate complex mixtures of molecules and quantify numerous analytes within a single run. There are several challenges in using LC-MS for the multiplexed quantification of cell-induced peptide degradation, including the need for non-degradable internal standards and the identification of optimal sample storage conditions. Another problem is that cell culture media and biological samples typically contain both proteins and lipids that can accumulate on chromatography columns and degrade their performance. However, removing these constituents can be expensive, time consuming, and increases sample variability. Here we show that directly injecting samples onto the LC-MS without any purification enables rapid and accurate quantification of peptide concentration, and that hundreds of LC-MS runs can be done on a single column without a significantly diminish the ability to quantify the degradation of peptide libraries. We also show that column failure is evident when hydrophilic peptides fail to be retained on the column, and this can be easily identified using standard peptide mixtures for column benchmarking. In total, this work introduces a simple and effective method for simultaneously quantifying the degradation of dozens of peptides in cell culture. By providing a streamlined and cost-effective method for the direct quantification of peptide degradation in complex biological samples, this work enables more efficient assessment of peptide stability and functionality, facilitating the development of advanced biomaterials and peptide-based therapies.

bioengineering↗

bioRxiv2024

Hydrogels with Independently Controlled Adhesion Ligand Mobility and Viscoelasticity Increase Cell Adhesion and Spreading

A primary objective in designing hydrogels for cell culture is recreating the cell-matrix interactions found within human tissues. Identifying the most important biomaterial features for these interactions is challenging because it is difficult to independently adjust variables such as matrix stiffness, stress relaxation, the mobility of adhesion ligands and the ability of these ligands to support cellular forces. In this work we designed a hydrogel platform consisting of interpenetrating polymer networks of covalently crosslinked poly(ethylene glycol) (PEG) and self-assembled peptide amphiphiles (PA). We can tailor the storage modulus of the hydrogel by altering the concentration and composition of each network, and we can tune the stress relaxation half-life through the non-covalent bonding in the PA network. Ligand mobility can be adjusted independently of the matrix mechanical properties by attaching the RGD cell adhesion ligand to either the covalent PEG network, the dynamic PA network, or both networks at once. Interestingly, our findings show that endothelial cell adhesion formation and spreading is maximized in soft, viscoelastic gels in which RGD adhesion ligands are present on both the covalent PEG and non-covalent PA networks. The dynamic nature of cell adhesion domains, coupled with their ability to exert substantial forces on the matrix, suggests that having different presentations of RGD ligands which are either mobile or are capable of withstanding significant forces are needed mimic different aspects of complex cell-matrix adhesions. By demonstrating how different presentations of RGD ligands affect cell behavior independently of viscoelastic properties, these results contribute to the rational design of hydrogels that facilitate desired cell-matrix interactions, with the potential of improving in vitro models and regenerative therapies.

bioengineering↗

bioRxiv2024

Optimizing Peptide Crosslinks for Cell-Responsive Hydrogels

Cells dynamically modify their local extracellular matrix by expressing proteases that degrade matrix proteins. This enables cells to spread and migrate within tissues, and this process is often mimicked in hydrogels through the incorporation of peptide crosslinks that can be degraded by cell-secreted proteases. However, the cleavage of hydrogel crosslinks will also reduce the local matrix mechanical properties, and most crosslinking peptides, such as the widely used GPQGIWGQ "PanMMP" sequence, lead to bulk degradation of the hydrogel. A subset of proteases are localized to the cell membrane and are only active in the pericellular region in the immediate vicinity of the cell surface. These membrane-type proteases have important physiological roles and enable cells to migrate within tissues. In this work we developed an approach to identify and optimize peptide sequences that are specifically degraded by membrane-type proteases. We utilized a proteomic screen to identify peptide targets, and coupled this with a functional assay that both quantifies peptide degradation by individual cell types and can elucidate whether the peptides are primarily cleaved by soluble proteases or membrane-type proteases. We then used a split-and-pool synthesis approach to generate more than 300 variants of the target peptide to improve the degradation behavior. We identified an optimized peptide sequence, KLVADLMASAE, which is primarily degraded by membrane-type proteases, but enables both endothelial cells and stem cells grown in KLVADLMASAE-crosslinked hydrogels to spread and have viabilities similar to the gels crosslinked by the PanMMP peptide. Notably, the biological performance of the KLVADLMASAE peptide-cross linked gels was significantly improved from the initial peptide target found in the proteomic screen. This work introduces a functional approach to identifying and refining protease-substrate peptides as a way to enhance the properties of hydrogel matrices.

bioengineering↗

bioRxiv2024

Quantifying and controlling the proteolytic degradation of cell adhesion peptides

Peptides are widely used within biomaterials to improve cell adhesion, incorporate bioactive ligands, and enable cell-mediated degradation of the matrix. While many of the peptides incorporated into biomaterials are intended to be present throughout the life of the material, their stability is not typically quantified during culture. In this work we designed a series of peptide libraries containing four different N-terminal peptide functionalizations and three C-terminal functionalization to better understand how simple modifications can be used to reduce non-specific degradation of peptides. We tested these libraries with three cell types commonly used in biomaterials research, including mesenchymal stem/stromal cells (hMSCs), endothelial cells, and macrophages, and quantified how these cell types non-specifically degraded peptide as a function of terminal amino acid and chemistry. We found that peptides in solution which contained N-terminal amines were almost entirely degraded by 48 hours, irrespective of the terminal amino acid, and that degradation occurred even at high peptide concentrations. Peptides with C-terminal carboxylic acids also had significant degradation when cultured with cells. We found that simple modifications to the termini could significantly reduce or completely abolish non-specific degradation when soluble peptides were added to cells cultured on tissue culture plastic or within hydrogel matrices, and that functionalizations which mimicked peptide conjugations to hydrogel matrices significantly slowed non-specific degradation. We also found that there were minimal differences across cell donors, and that sequences mimicking different peptides commonly-used to functionalized biomaterials all had significant non-specific degradation. Finally, we saw that there was a positive trend between RGD stability and hMSC spreading within hydrogels, indicating that improving the stability of peptides within biomaterial matrices may improve the performance of engineered matrices.

bioengineering↗