Collagen-Targeted Theranostic Nanosponges for Delivery of the Matrix Metalloproteinase 14 Inhibitor Naphthofluorescein

We report the development of a theranostic collagen targeted cell penetrating drug delivery system toward treatment of cardiovascular disease. Caused by the action of matrix metalloproteinases (MMP), degraded collagen is a hallmark of unstable atherosclerotic plaques that are highly susceptible toward rupture. Targeting unstable plaques and delivering MMP blockers directly to plaque to inhibit MMP activity is a promising new strategy that requires the benefits and possibilities of nanodelivery approaches. The presented delivery system is designed to (a) target and bind to a cryptic epitope on collagen IV exposed through the degradative action of matrix metalloproteinase 2 (MMP2), (b) to image the targeting and cell uptake, and (c) to deliver the MMP14 inhibitor naphthofluorescein. In detail, the novel targeting unit is composed of a collagen-homing T-peptide and bound to a MMP2-cleavable activatable cell penetrating peptide (ACPP) which upon cleavage by MMP2 deposits the MMP14 blocker drug into cells, directly into contact with MMP 14 activating enzymes. To selectively attach both the targeting peptide and a reporting imaging dye, a nanosponge nanoparticle network is modified to present orthogonal aldehyde and thiol functional groups as surface units. The MMP14 inhibitor naphthofluorescein is loaded into the nanoparticle delivery system after postconjugation chemistries and finalizes the synthesis of this novel theranostic delivery system. The ability to evade phagocytosis is confirmed in vitro by using murine RAW cell line and effective cell uptake in vitro by using the MMP2 producing the HT1080 cell line is demonstrated. In this work, we have combined a highly specific targeting peptide directed against degraded collagen and a tailorable nanosystem that is deemed to deliver its potent drug load directly into cells, to inhibit the cascade for MMP activation which breaks down collagen structures leading to plaque rupture, the underlying cause of myocardial infarction and strokes.