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Tissue Engineering

Tissue Engineering - Poster Session E

Poster BB12 - Promoting Wound Repair With Thrombin-Sensitive Platelet-Like Particles

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

Introduction:  Platelet-like particles (PLPs) are a polymeric microparticle-based wound healing technology developed to enhance hemostatic responses to injury. They are comprised of an ultra-low crosslinked microgel (ULC) functionalized with fibrin-binding motifs. By increasing the interaction of fibrin molecules in the bloodstream and applying mechanical contractile forces to the resulting clot, wounds are stabilized faster and show improved healing characteristics. A formulation of PLP with integrated thrombin-cleavable peptides in the microgel polymer chains (referred to as TS-PLPs), has been developed by our group to replicate the shape changing properties of platelets. (Figure 1) The loosely crosslinked and highly deformable nature of TS-PLPs also make them an attractive vehicle for the delivery of growth factors to assist in regeneration, as they are directly incorporated throughout the initial clot and developing tissue. The partial degradation of these particles at the wound site due to the presence of endogenous thrombin may also affect their performance as a drug delivery mechanism, so they will be studied side-by-side with normal PLPs. Additionally, these particles may further improve wound healing when applied in a fibrin scaffold containing other supportive cell types such as mesenchymal stem cells (MSCs). This study will determine if MSCs, growth factors, and/or exosomes can be successfully integrated into the PLP system and delivered into fibrin hydrogel clots to stimulate the repair of the wound microenvironment. The ability of this system to recruit and support the growth of fibroblasts will be assessed to determine if there is potential for in vivo wound healing applications.

Materials and

Methods:  ULCs constructed of 10% acrylic acid and either 90% PNIPAM (PLPs) or 85% PNIPMAM and 5% thrombin-sensitive peptide (TS-PLPs) were synthesized using precipitation polymerization. Each type of particle was then functionalized with an anti-fibrin antibody using NHS/EDC chemistry to enable them to bind to fibrin within the wound environment. The size and shape of the TS-PLPs were assessed with AFM to compare them to existing PLP formulations. TSNs (TS-PLPs before the addition of fibrin-sensitive antibodies) were then exposed to 100 U/mL thrombin over a period of 96 hours and assessed with AFM and Nanosight particle analysis to determine their response to degradation in a simulated clot environment. Finally, fibrin clots were formed containing either PLPs or TS-PLPs to assess their effect on the porosity of the resultant clot structure. On-going studies include the addition of PLPs or TS-PLPs to fibrin clots containing fibroblasts in vitro to simulate their effect on wound healing.

Results, Conclusions, and Discussions: Studies performed by our group to this point have shown that TS-PLPs created by current methods have an average dry diameter of 320±81 nm and average dry height of 23±8 nm. When exposed to thrombin, the TS-PLPs initially swell for the first two hours and then decrease in size over time, indicating that their functional peptide group is being cleaved successfully. (Figure 2) Analysis of the clot retraction behavior of each particle shows that PLPs are able to reduce the porosity of a fibrin matrix from 76±7% to 63±8%, and TS-PLPs perform similarly with a resulting porosity of 63±4% when exposed to thrombin. On-going studies are evaluating in vitro information on the impact of delivering PLPs or TS-PLPs augmented with cells and/or growth factors to a wound model and will allow our group to make future decisions about the most effective way to apply this technology in vivo. The PLP technology alone has already been shown to decrease bleeding time and improve healing outcomes in vivo, and concomitant delivery of cells and growth factors may further increase its effectiveness in stimulating regeneration.

Acknowledgements (Optional):