Enhanced Endothelial Cell Delivery for Repairing Injured Endothelium via Pretargeting Approach and Bioorthogonal Chemistry.

Arterial wall injury often leads to endothelium cell activation, endothelial detachment, and atherosclerosis plaque formation. While abundant research efforts have been placed on treating the end stages of the disease, no cure has been developed to repair injured and denude endothelium often occurred at an early stage of atherosclerosis. Here, a pretargeting cell delivery strategy using combined injured endothelial targeting nanoparticles and bioorthogonal click chemistry approach was developed to deliver endothelial cells to replenish the injured endothelium via a two-step process. First, nanoparticles bearing glycoprotein 1b α (Gp1bα) proteins and tetrazine (Tz) were fabricated to provide a homogeneous nanoparticle coating on an injured arterial wall via the interactions between Gp1bα and von Willebrand factor (vWF), a ligand that is present on denuded endothelium. Second, transplanted endothelium cells bearing transcyclooctene (TCO) would be quickly immobilized on the surfaces of nanoparticles via TCO:Tz reactions. In vitro binding studies under both static and flow conditions confirmed that our novel Tz-labeled Gp1bα-conjugated poly(lactic-co-glycolic acid) (PLGA) nanoparticles can successfully pretargeted toward the injured site and support rapid adhesion of endothelial cells from the circulation. Ex vivo results also confirm that such an approach is highly efficient in mediating the local delivery of endothelial cells at the sites of arterial injury. The results support that this pretargeting cell delivery approach may be used for repairing injured endothelium in situ at its early stage.

Engineering Delivery of Nonbiologics Using Poly(lactic-co-glycolic acid) Nanoparticles for Repair of Disrupted Brain Endothelium.

Traumatic brain injury (TBI) is known to alter the structure and function of the blood-brain barrier (BBB). Blunt force or explosive blast impacting the brain can cause neurological sequelae through the mechanisms that remain yet to be fully elucidated. For example, shockwaves propagating through the brain have been shown to create a mechanical trauma that may disrupt the BBB. Indeed, using tissue engineering approaches, the shockwave-induced mechanical injury has been shown to modulate the organization and permeability of the endothelium tight junctions. Because an injury to the brain endothelium typically induces a high expression of E-selectin, we postulated that upregulation of this protein after an injury can be exploited for diagnosis and potential therapy through targeted nanodelivery to the injured brain endothelium. To test this hypothesis, we engineered poly(lactic-co-glycolic acid) (PLGA) nanoparticles to encapsulate therapeutic nonbiologics and decorated them with ligands to specifically target the E-selectin. A high level of the conjugated nanoparticles was found inside the injured cells. Repair of the injury site was then quantitatively measured and analyzed. To summarize, exploiting the tunable properties of PLGA, a targeted drug delivery strategy has been developed and validated, which combines the specificity of ligand/receptor interaction with therapeutic reagents. Such a strategy could be used to provide a potential theragnostic approach for the treatment of modulated brain endothelium associated with TBI.