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Biomaterials

Biomaterials - Poster Session E

Poster N6 - Conjugation of proangiogenic peptide to 3D printed gelatin methacrylate affects physical properties of the bioink

Saturday, October 26, 2024
10:00 AM – 11:00 AM EST
Location: Exhibit Hall E, F & G

Introduction:  Approximately 13% of women are diagnosed with breast cancer during their lifetime. Mastectomy to remove breast tissue is often the recommended surgical treatment. Breast reconstruction post-mastectomy can significantly increase patient quality of life and psychosocial well-being.

An important aspect of reconstructive surgery often overlooked is the restoration of the nipple areolar complex (NAC). Reestablishment of the NAC can significantly improve emotional well-being of patients. Previous attempts to create a clinically relevant NAC replacement have drawbacks, most significantly being a lack of vascularization, leading to a loss of shape and tissue necrosis. Tissue engineering, and 3D printing specifically, has the potential to produce personalized NAC implants with precisely placed bioactive components to stimulate vascularization.

Vascular endothelial growth factor (VEGF) has an important role in stimulating vascularization but has drawbacks when used therapeutically. Peptides replicating the binding site of VEGF have similar bioactivity along with improved safety, manufacturability, and chemical stability. Peptide QK is a promising alternative to VEGF, showing proangiogenic capabilities in vitro and in vivo while being uniquely thermodynamically stable. Acrylated QK peptide has previously been covalently bound to gelatin methacrylate (GelMA) while maintaining bioactivity, reducing the risk of freely diffusing peptide. However, more work is needed to characterize the material properties of 3D printed GelMA with bound peptide. Using a factorial design, we investigate the relationship between GelMA degree of methacrylation, GelMA concentration, and QK peptide concentration.

Materials and

Methods:  Lyophilized GelMA was purchased from CELLINK at 50% and 95% degree of methacrylation. GelMA solutions were prepared by combining 10%, 15%, or 20% w/v GelMA with 0.1% Lithium phenyl-2,4,6-trimethylbenzoylphosphinate photo initiator in phosphate buffer saline (PBS). Acrylated QK peptide was synthesized at >/= 85% purity (GenScript) and added at concentrations of 1, 10, or 100 uM.

Cylindrical scaffolds were designed with a height of 10 mm and a diameter of 5 mm. Constructs were printed with the BioAssembly Bot 400 (Advanced Solutions). Each scaffold was then UV crosslinked for 2 minutes.

Compression testing via an Instron machine with a 1 kN load cell determined the compressive modulus. Samples were compressed at a rate of 1.3 +/- 0.3 mm/min. The compressive modulus was determined by calculating the slope of the linear region of the stress-strain curve.

Swelling characteristics were determined through a series of weights. First, scaffolds were weighed post-print. After soaking in PBS at room temperature for 48 hours, a post-swell weight was measured. Finally, scaffolds were lyophilized for 24 hours and measured for dry weight. The mesh size of the hydrogels was calculated using the Flory Rehner theory for polymers crosslinked in the presence of solvents.

To determine the enzymatic degradation rate each scaffold was placed in PBS containing 2 U/mL of collagenase type II at 37 C for 2 weeks. Timepoints of 3, 7, and 14 days were be used. At each timepoint scaffolds were rinsed with PBS, lyophilized, and weighed to calculate the percent degradation.

Results, Conclusions, and Discussions: Increasing concentration of QK peptide within the GelMA constructs correlated with a decrease in the compressive modulus and an increase in mesh size. This is expected as acrylated QK peptide binds by the same mechanism as GelMA crosslinking, thereby interfering with the crosslinking ability of the gel. As GelMA degree of methacrylation increased we also observed an increase in compressive modulus and decrease in mesh size.

This experiment showed how physical and mechanical properties of a 3D printed hydrogel could be modified by the addition of a proangiogenic peptide. Further studies will examine how concentration of the QK peptide affects endothelial cell movement in a GelMA construct. Results from the material studies combined with the endothelial cell response studies will help to determine the ideal concentration of QK peptide within a GelMA construct to induce rapid vascularization of a NAC implant. This study is foundational for the further development of implantable 3D printed structures that encourage rapid vascularization.

Acknowledgements (Optional):