Kevin D. Lance

Nanostructured thin film polymer devices for constant-rate protein delivery.

Herein long-term delivery of proteins from biodegradable thin film devices is demonstrated, where a nanostructured polymer membrane controls release. Protein was sealed between two poly(caprolactone) films, which generated the thin film devices. Protein release for 210 days was shown in vitro, and stable activity was established through 70 days with a model protein. These thin film devices present a promising delivery platform for biologic therapeutics, particularly for application in constrained spaces.

Perivascular delivery of resolvin D1 inhibits neointimal hyperplasia in a rat model of arterial injury

Objective: Lipid mediators derived from omega‐3 polyunsaturated fatty acids such as resolvin D1 (RvD1) accelerate the resolution of inflammation and have potential as vascular therapeutics. The objective of this study was to evaluate local perivascular delivery of RvD1 as a means to attenuate neointimal hyperplasia in a rat model of arterial injury. Methods: Smooth muscle cells were harvested from rat aortas to study the effects of RvD1 on rat arterial vascular smooth muscle cell responses in vitro, with focus on inflammation, proliferation, migration, cytoskeletal changes, and cytotoxicity. The safety and efficacy of perivascular delivery of RvD1 through thin biodegradable three‐layered poly(lactic‐co‐glycolic acid) wraps or 25% Pluronic F127 gels were studied in a rat model of carotid angioplasty. A total of 200 ng of RvD1 was loaded into each construct for perivascular delivery after injury. Morphometric and histologic analyses were performed 3 and 14 days after injury. Results: RvD1 attenuated rat arterial vascular smooth muscle cell inflammatory pathways, proliferation, migration, and mitogen‐induced cytoskeletal changes in vitro, without evidence of cytotoxicity. RvD1‐loaded wraps reduced neointimal formation after carotid angioplasty by 59% vs no‐wrap controls (P = .001) and by 45% vs vehicle‐wrap controls (P = .002). RvD1‐loaded Pluronic gels similarly reduced neointimal formation by 49% vs no‐gel controls (P = .02) and by 52% vs vehicle‐gel controls (P = .02). No group was associated with infection, thrombosis, or negative vessel remodeling. Wraps were found to be easier to apply than gel constructs. Ki67 proliferation index was significantly lower in RvD1‐loaded wrap‐treated arteries compared with both no‐wrap and vehicle‐wrap controls at both 3 and 14 days after injury (65% vs no‐wrap group and 70% vs vehicle‐wrap group at day 3, 49% vs both control groups at day 14; P < .05). Similarly, oxidative stress (30% and 29%; P < .05) and nuclear factor &kgr;B activation (42% and 45%; P < .05) were significantly lower in the RvD1‐loaded wrap group compared with both no‐wrap and vehicle‐wrap controls at 3 days after injury. Conclusions: Local perivascular delivery of RvD1 attenuates formation of neointimal hyperplasia without associated toxicity in a rat model of carotid angioplasty. This effect is likely due to attenuation of inflammatory pathways as well as decreased arterial smooth muscle cell proliferation and migration. Clinical Relevance: Failure of peripheral vascular interventions remains the single greatest challenge in management of vascular disease, with failure rates approaching 50% or greater within 2 years for many interventions. In contrast to the currently available cytotoxic drugs used on vascular devices that delay vessel healing, novel endogenous “proresolving” lipid mediators (such as resolvin D1) have potential to reduce neointimal hyperplasia by accelerating homeostasis. This study provides proof‐of‐concept for local perivascular delivery of proresolving agents to improve the healing response after acute vascular injury.

Unidirectional and sustained delivery of the proresolving lipid mediator resolvin D1 from a biodegradable thin film device.

Resolvin D1 (RvD1) belongs to a family of endogenously derived proresolving lipid mediators that have been shown to attenuate inflammation, activate proresolution signaling, and promote homeostasis and recovery from tissue injury. In this study we present a poly(lactic-co-glycolic acid) (PLGA) based thin-film device composed of layers of varying ratios of lactic and glycolic acid that elutes RvD1 unidirectionally to target tissues. The device demonstrated sustained release in vitro for 56 days with an initial burst of release over 14 days. The asymmetric design of the device released 98% of RvD1 through the layer with the lowest molar ratio of lactic acid to glycolic acid, and the remainder through the opposite side. We validated structural integrity of RvD1 released from the device by mass spectrometry and investigated its bioactivity on human vascular endothelial (EC) and smooth muscle cells (VSMC). RvD1 released from the device attenuated VSMC migration, proliferation, and TNF-α induced NF-κB activation, without evidence of cytotoxicity. Delivery of RvD1 to blood vessels was demonstrated ex vivo in a flow chamber system using perfused rabbit aortas and in vivo in a rat carotid artery model, with the devices applied as an adventitial wrap. Our results demonstrate a novel approach for sustained, local delivery of Resolvin D1 to vascular tissue at therapeutically relevant levels.

In Vitro and In Vivo Sustained Zero-Order Delivery of Rapamycin (Sirolimus) From a Biodegradable Intraocular Device

PURPOSE We created implantable intraocular devices capable of constant and continuous rapamycin release on the scale of months to years. METHODS Polycaprolactone (PCL) thin films were used to encapsulate rapamycin to create implantable and biodegradable intraocular devices. Different film devices were studied by modifying the size, thickness, and porosity of the PCL films. RESULTS In vitro release of rapamycin was observed to be constant (zero-order) through 14 weeks of study. Release rates were tunable by altering PCL film porosity and thickness. In vivo release of rapamycin was observed out through 16 weeks with concentrations in the retina-choroid in the therapeutic range. Rapamycin concentration in the blood was below the lower limit of quantification. The drug remaining in the device was chemically stable in vitro and in vivo, and was sufficient to last for upwards of 2 years of total release. The mechanism of release is related to the dissolution kinetics of crystalline rapamycin. CONCLUSIONS Microporous PCL thin film devices demonstrate good ocular compatibility and the ability to release rapamycin locally to the eye over the course of many weeks.

Perivascular delivery of resolvin D1 inhibits neointimal hyperplasia in a rabbit vein graft model

Objective: Inflammation is a key driver of excessive neointimal hyperplasia within vein grafts. Recent work demonstrates that specialized proresolving lipid mediators biosynthesized from omega‐3 polyunsaturated fatty acids, such as resolvin D1 (RvD1), actively orchestrate the process of inflammation resolution. We investigated the effects of local perivascular delivery of RvD1 in a rabbit vein graft model. Methods: Ipsilateral jugular veins were implanted as carotid interposition grafts through an anastomotic cuff technique in New Zealand white rabbits (3–4 kg; N = 80). RvD1 (1 &mgr;g) was delivered to the vein bypass grafts in a perivascular fashion, using either 25% Pluronic F127 gel (Sigma‐Aldrich, St. Louis, Mo) or a thin bilayered poly(lactic‐co‐glycolic acid) (PLGA) film. No treatment (bypass only) and vehicle‐loaded Pluronic gels or PLGA films served as controls. Delivery of RvD1 to venous tissue was evaluated 3 days later by liquid chromatography‐tandem mass spectrometry. Total leukocyte infiltration, macrophage infiltration, and cell proliferation were evaluated by immunohistochemistry. Elastin and trichrome staining was performed on grafts harvested at 28 days after bypass to evaluate neointimal hyperplasia and vein graft remodeling. Results: Perivascular treatments did not influence rates of graft thrombosis (23%), major wound complications (4%), or death (3%). Leukocyte (CD45) and macrophage (RAM11) infiltration was significantly reduced in the RvD1 treatment groups vs controls at 3 days (60%‐72% reduction; P < .01). Cellular proliferation (Ki67 index) was also significantly lower in RvD1‐treated vs control grafts at 3 days (40%‐50% reduction; P < .01). Treatment of vein grafts with RvD1‐loaded gels reduced neointimal thickness at 28 days by 61% vs bypass only (P < .001) and by 63% vs vehicle gel (P < .001). RvD1‐loaded PLGA films reduced neointimal formation at 28 days by 50% vs bypass only (P < .001). RvD1 treatment was also associated with reduced collagen deposition in vein grafts at 28 days. Conclusions: Local perivascular delivery of RvD1 attenuates vein graft hyperplasia without associated toxicity in a rabbit carotid bypass model. This effect appears to be mediated by both reduced leukocyte recruitment and decreased cell proliferation within the graft. Perivascular PLGA films may also impart protection through biomechanical scaffolding in this venous arterialization model. Our studies provide further support for the potential therapeutic role of specialized proresolving lipid mediators such as D‐series resolvins in modulating vascular injury and repair. Clinical Relevance: Autologous vein bypass grafts are the most durable means for revascularization in peripheral vascular disease; however, midterm and long‐term outcomes are limited by vein graft hyperplasia with associated vein graft failure. Endogenous proresolving lipid mediators such as resolvin D1 have the potential to attenuate vein graft hyperplasia by accelerating repair. This study provides proof of concept for local delivery of resolvin D1 to reduce inflammation and to improve the healing response after vein bypass grafting.