Fast and Mild Strategy, Using Superhydrophobic Surfaces, to Produce Collagen/Platelet Lysate Gel Beads for Skin Regeneration

Platelet lysate (PL) was encapsulated in collagen (Coll) millimetric gel beads, on biomimetic superhydrophobic surfaces, under mild conditions, with the aim of obtaining easy-to-handle formulations able to provide sustained release of multiple growth factors for skin ulcers treatment. The gel particles were prepared with various concentrations of PL incorporating or not stem cells, and tested as freshly prepared or after being freeze-dried or cryopreserved. Coll + PL particles were evaluated regarding degradation in collagenase-rich environment (simulating the aggressive environment of the chronic ulcers), sustained release of total protein, PDGF-BB and VEGF, cell proliferation (using particles as the only source of growth factors), scratch wound recovery and angiogenic capability. Compared to Coll solely particles, incorporation of PL notably enhanced cell proliferation (inside and outside gels) and favored scratch wound recovery and angiogenesis. Moreover, cell-laden gel particles containing PL notably improved cell proliferation and even migration of cells from one particle towards a neighbor one, which led to cell-cell contacts and the spontaneous formation of tissue layers in which the spherical gels were interconnected by the stem cells.