Development and characterization of microparticular controlled release system for angiogenesis enhancement

The human body has the natural ability to heal itself in many ways. Regenerative Medicine goes beyond the typical diseases management procedures to search for, develop and apply new effective therapies to support the human body to better repair, regenerate or restore injured tissues and organs. The enhancement of wound healing has ever been a Regenerative Medicine goal. Chronic, non-healing wounds are a persistent issue that increases morbidity rates and healthcare costs. A key aspect of many non-healing wounds is the reduced presence of vessel growth. Thus, angiogenesis, a complex sequence through which new capillaries and vessels are formed, is one of key regenerative processes. The aim of this work was to develop and optimize a microspheres-based (µS) drug delivery system (DDS) for the sustained release of two selected pro-angiogenic factors (AF): i) L-Lysine (K), an essential ammino acid, chosen for its ability to control the inflammation degree and promote angiogenic processes by a ligand-receptor binding mechanism; and ii) cell secretome (S), derived from human mesenchymal cardiac cells (hCmPCs), chosen for its immuno-modulatory and pro-angiogenic potential. AF-loaded µS were developed in order to be incorporated within a collagen micro-porous scaffold to obtain a regenerative construct that, once implanted in the injury site, can simultaneously act as a supporting substrate (thanks to collagen 3D structure) and as a reservoir of molecular regulators able to support/promote wound healing process during the entire regeneration time-window. The DDS was developed using an FDA-approved synthetic polymer, the poly(lactic-co-glycolic acid) (PLGA), for its well-known biocompatibility, biodegradability and low antigenicity. Specifically, the double emulsion/solvent evaporation technique (W/O/W) was employed for the encapsulation of the selected AF into PLGA µS. Thus, L-Lysine-loaded (µS/K), secretome-loaded (µS/S) and empty PLGA µS were produced and characterized. In particular, AF-loaded µS properties were assessed in terms of surface morphology, diameter distribution, yield, encapsulation efficiency, degradation time and release kinetics. Lastly, the cytotoxicity and the angiogenic power of the developed DDS were in vitro evaluated and compared using primary human mammary endotelial cells (hMEC). The approach proposed in this work, based on the combined use of biomaterials and bioactive molecules, could represent a useful platform for the development of more effective (i.e., ‘advanced’) therapies for hard-to-heal wounds management compared to traditional therapies.