The development and characterization of SDF1α-elastin-like-peptide nanoparticles for wound healing

Abstract

Chronic skin wounds are characterized by poor re-epithelialization, angiogenesis and granulation. Previous work has demonstrated that topical stromal cell-derived growth factor-1 (SDF1) promotes neovascularization, resulting in faster re-epithelialization of skin wounds in diabetic mice. However, the clinical usefulness of such bioactive peptides is limited because they are rapidly degraded in the wound environment due to high levels of proteases. Here, we describe the development of a recombinant fusion protein comprised of SDF1 and an elastin-like peptide that confers the ability to self-assemble into nanoparticles. The fusion protein and recombinant human SDF1 showed similar binding characteristics, as indicated by the measured equilibrium dissociation constant (Kd) for the binding of free SDF1 or the fusion protein to the CXCR4 receptor. The biological activity of SDF1-ELP, as measured by intracellular calcium release in HL60 cells was dose dependent, and also very similar to that of free SDF1. In contrast, the biological activity of SDF1-ELP in vivo was significantly superior to that of free SDF1. When applied to full thickness skin wounds in diabetic mice, wounds treated with SDF1-ELP nanoparticles were 95% closed by day 21, and fully closed by day 28, while wounds treated with free SDF1, ELP alone, or vehicle were only 80% closed by day 21, and took 42 days to fully close. In addition, the SDF1-ELP nanoparticles significantly increased the epidermal and dermal layer of the healed wound, as compared to the other groups. These results indicate SDF1-ELP fusion protein nanoparticles are promising agents for the treatment of chronic skin wounds.

Stromal Cell-Derived Growth Factor-1 Alpha-Elastin Like Peptide Fusion Protein Promotes Cell Migration and Revascularization of Experimental Wounds in Diabetic Mice

“…13 In vitro, SDF1-ELP promoted the migration of cells and induced vascularization similar to SDF1. However, when both SDF1-ELP and SDF1 were incubated in wound fluid ex vivo for an extended period of time, SDF1-ELP fusion protein nanoparticles were stable, while SDF1 lost its biological activity.…”

“…In our previous work, 13 we demonstrated the bioactivity of SDF1-ELP in excisional wounds made on diabetic mice. 1 · 1 cm 2 excisional wounds created on the back of diabetic mice and treated with SDF1-ELP, SDF1, and other negative controls.…”

“…13 Briefly, SDF1-ELP was made by juxtaposing human SDF1 to an ELP in a pET25B+ vector. The fusion protein was expressed in Escherichia coli and purified using a unique property conferred by the ELP, which enables it to reversibly aggregate into nanoparticles above its inverse transition temperature.…”

“…1 · 1 cm 2 excisional wounds were created on the back of the mice using a premade template. Test solutions consisting of 1,000 nM SDF1-ELP, SDF, ELP, and plain PBS were prepared in fibrin gels as previously described 13 and applied onto the wound area, after which the wounds were covered with TegardermÔ (3M) and secured using sutures (Henry Schein).…”

“…In our previous work, 13 we showed the development of an SDF1 derivative, SDF1 elastin-like peptide (SDF1-ELP) with a similar in vitro bioactivity as SDF1, but a superior in vivo efficacy. In this work, we show that while SDF1-ELP promotes the migration of cells and induces vascularization similar to SDF1 in vitro, it is more stable in wound fluid.…”