The effect of intramural delivery of polymeric nanoparticles loaded with the antiproliferative 2-aminochromone U-86983 on neointimal hyperplasia development in balloon-injured porcine coronary arteries

Nanoparticle eluting-angioplasty balloons to treat cardiovascular diseases

Nanoparticles (NPs) can be used to locally deliver anti-restenosis drugs when they are infused directly to the injured arteries after intervention procedures such as angioplasty. However, the efficacy of transferring NPs via infusion to the arterial wall is limited, at least partially, due to poor NP retention on the inner artery wall. To improve NP retention, angioplasty balloons coated with drug-loaded NPs were fabricated via either layer-by-layer (LbL) electrostatic coating or acrylic-based hydrogel (AAH) coating techniques. Three types of NPs, namely poly (lactide-co-glycolide) (PLGA), biodegradable photo-luminescent PLGA and urethane doped polyester were studied. The transfer efficacy of NPs from various coatings to the arterial wall were further evaluated to find the optimal coating conditions. The ex vivo NP transfer studies showed significantly more NPs being transferred to the rat arterial wall after the angioplasty procedure by the AAH coating (95% transfer efficiency) compared to that of the LbL technique (60%) and dip coating (20%) under flow conditions (10 dyn/cm²). Our results suggest that the AAH coating of drug-loaded NPs on the angioplasty balloon could potentially provide superior retention of drug-loaded NPs onto the arterial wall for a better local delivery of drug-loaded NPs to effectively treat arterial diseases.

Efficiency of drug delivery to the coronary arteries in swine is dependent on the route of administration: assessment of luminal, intimal, and adventitial coronary artery and venous delivery methods

PURPOSE

To compare the efficiency of five different drug delivery methods to the coronary artery in swine.

MATERIALS AND METHODS

A nanoparticle-albumin-bound, nonradioactive isotopic marker was administered within the left anterior descending coronary artery (LAD) through a microinfusion catheter (MIC: adventitial, n = 8, and luminal, n = 4), a porous drug infusion balloon (DIB: intimal, n = 4), and a straight catheter (SC: luminal, n = 2) and within the superior vena cava (SC: intravenous, luminal, n = 2). The distribution of the marker in heart, lung, liver, kidney, muscle, blood, urine, and bile was determined 68-84 minutes after delivery. The heart was sectioned into six axial slices and each slice divided into four quadrants. The marker content was assayed by neutron bombardment and the total counts of disintegrations per minute (DPM) expressed as a percentage of the control for each device delivery control.

RESULTS

After luminal delivery with the nonactuated MIC (MIC-NA) or intimal delivery with the DIB, 0.17% ± 0.07 and 0.39% ± 0.09, respectively, less than 0.39% of the total marker was detected in the heart. After adventitial delivery with the actuated MIC (MIC-A), 63.1% ± 9.9 of the total marker was detected in the heart. Marker was only detected in quadrants containing the coronary LAD, with the highest level in the middle slice and lower marker levels in consecutive proximal and distal heart slices. The nonactuated MIC-NA and DIB drug infusion balloon patterns of marker distribution were similar to those of actuated MIC-A, although with reduced levels. These delivery methods were also associated with considerably more marker detected in the lungs and liver: at least 22% compared with 1.34% ± 1.34 for the actuated MIC-A There was one delivery failure with the actuated MIC.

CONCLUSIONS

Catheter-based adventitial delivery with the MIC-A represents a more efficient delivery method for retention of vascular therapeutics.

Local delivery of modified paclitaxel-loaded poly(epsilon-caprolactone)/pluronic F68 nanoparticles for long-term inhibition of hyperplasia

The purpose of this research is to test the possibility of localized intravascular infusion of didodecyldimethylammonium bromide (DMAB)-modified paclitaxel-loaded poly(epsilon-caprolactone)/Pluronic F68 (PCL/F68) nanoparticles to achieve long-term inhibition of hyperplasia in a balloon-injured rabbit carotid artery model. Paclitaxel-loaded nanoparticles were prepared by modified solvent displacement method using commercial poly(lactide-co-glycolide) (PLGA) and self-synthesized PCL/F68, respectively. DMAB was adsorbed on the nanoparticle surface by electrostatic attraction between positive and negative charges to enhance arterial retention. Nanoparticles were found to be of spherical shape with a mean size of around 300 nm and polydispersity of less than 0.150. The surface charge was changed to positive values after the DMAB modification. The in vitro drug release profile of all nanoparticle formulation showed a biphasic release pattern. Drug release from DMAB-modified PCL/F68 nanoparticles (DPNP) was significantly slower than DMAB-modified PLGA nanoparticles (PGNP). After 90 days, DPNP group showed very significant inhibition of neointimal proliferation (p < 0.01), and PGNP group yielded significant inhibition of neointimal proliferation (p < 0.05), when compared with drug-free nanoparticles group. In conclusion, local delivery of paclitaxel-loaded DMAB-modified PCL/F68 nanoparticles was proven an effective means of long-term inhibition of hyperplasia in the rabbits.

Vitamin E TPGS-emulsified poly(lactic-co-glycolic acid) nanoparticles for cardiovascular restenosis treatment

AIMS

Paclitaxel is one of the most effective antiproliferative agents and it has been applied in the development of drug-eluting stents. There are difficulties, however, in using paclitaxel in clinical applications owing to its poor solubility and side effects. We have synthesized nanoparticles of biodegradable polymers for the effective and sustainable delivery of paclitaxel and other antiproliferative agents for restenosis treatment.

METHODS & RESULTS

Paclitaxel-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles were prepared by a modified solvent extraction/evaporation method with D-alpha-tocopheryl polyethylene glycol 1000 succinate (TPGS) or polyvinyl alcohol (PVA) as an emulsifier. Drug-loaded nanoparticles were characterized for size and size distribution, surface morphology, surface charge, drug-encapsulation efficiency and in vitro drug-release kinetics. Cellular uptake of fluorescent nanoparticles was investigated in vitro in coronary artery smooth muscle cells and in vivo in the carotid arteries of rabbits. The antiproliferative effects of the nanoparticle formulations were assessed in vitro in close comparison with Taxol((R)). Both the PVA- and TPGS-emulsified nanoparticles have similar size and size distribution, surface morphology and dispersion stability and showed great advantages over paclitaxel in in vitro cellular uptake and cytotoxicity than Taxol. The TPGS-emulsified nanoparticle formulation has higher drug-encapsulation efficiency, cellular uptake and cytotoxicity than the PVA-emulsified nanoparticle formulation. IC(50) in 24-h culture with coronary artery smooth muscle cells is 748 ng/ml for paclitaxel, 708 ng/ml for PVA-emulsified nanoparticles and 474 ng/ml for TPGS-emulsified nanoparticles, respectively.

CONCLUSION

TPGS-emulsified PLGA nanoparticles have great potential for the effective and sustainable delivery of antiproliferative agents and for the development of nanoparticle-coated stents, which may become the third generation of cardiovascular stents.

Modified Paclitaxel-loaded Nanoparticles for Inhibition of Hyperplasia in a Rabbit Arterial Balloon Injury Model

PURPOSE

This study tested the possibility of localized intravascular infusion of positive charged paclitaxel-loaded nanoparticles (NPs) to better prevent neointimal formation in a rabbit carotid artery injury model.

MATERIALS AND METHODS

NPs were prepared by oil-water emulsion/solvent evaporation technique using biodegradable poly (lactide-co-glycolide) (PLGA). A cationic surfactant, didodecyldimethylammonium bromide (DMAB), was absorbed on the NP surface by electrostatic attraction between positive and negative charges. NPs were characterized in such aspects as size, surface morphology, surface charges as well as in vitro drug release profile. Balloon injured rabbit carotid arteries were treated with single infusion of paclitaxel-loaded NP suspension and observed for 28 days. The inhibitory effects of NPs on neointima formation were evaluated as end-point.

RESULTS

NPs showed spherical shape with a diameter ranging from 200 to 500 nm. Negatively charged PLGA NPs shifted to positive after the DMAB modification. The in vitro drug release profile showed a biphasic release pattern. Morphometric analyses on the retrieved artery samples revealed that the inhibitory effect of intima proliferation was dose-dependent. At a concentration of 30 mg ml(-1), NP infusion completely inhibited intima proliferation in a rabbit vascular injury model.

CONCLUSIONS

Paclitaxel-loaded NPs with DMAB modification were proven an effective means of inhibiting proliferative response to vascular injury in a rabbit model.

Locally delivered nanoencapsulated tyrphostin (AGL-2043) reduces neointima formation in balloon-injured rat carotid and stented porcine coronary arteries

Local delivery of antiproliferative drugs encapsulated in biodegradable nanoparticles (NP) has shown promise as an experimental strategy for preventing restenosis development. A novel PDGFRbeta-specific tyrphostin, AGL-2043, was formulated in polylactide-based nanoparticles and was administered intraluminally to the wall of balloon-injured rat carotid and stented pig coronary arteries. The disposition and elimination kinetics within the vessel wall, as well as the antirestenotic potential of the novel drug and delivery system, were evaluated. The efficacy and the local drug elimination kinetics were affected by the size of the NP and the drug-carrier binding mode. Despite similar arterial drug levels 90 min after delivery in rats, small NP were more efficacious in comparison to large NP (90 and 160 nm, respectively). AGL-2043 selectively inhibited vascular SMC in a dose-dependent manner. The antiproliferative effect of nanoencapsulated tyrphostin was considerably higher than that of surface-adsorbed drug. In the pig model, intramural delivery of AGL-2043 resulted in reduced in-stent neointima formation in the coronary arteries over control despite similar degrees of wall injury. The results of this study suggest that locally delivered tyrphostin AGL-2043 formulated in biodegradable NP may be applicable for antirestenotic therapy independent of stent design or type of injury.

Surface modification of liposomes for selective cell targeting in cardiovascular drug delivery

Cardiovascular disease processes such as atherosclerosis, restenosis, and inflammation are typically localized to discrete regions of the vasculature, affording great opportunity for targeted pharmacological treatment. Liposomes are potentially advantageous targeted drug carriers for such intravascular applications. To facilitate their use as drug delivery vehicles, we have considered three components of liposome design: (i) identification of candidate cell surface receptors for targeting; (ii) identification of ligands that maintain binding specificity and affinity; and (iii) prevention of rapid nonspecific clearance of liposomes into the reticuloendothelial organs. In this report, we describe our work in developing liposomal surface modifications that address both targeting and clearance. An arginine-glycine-aspartic acid (RGD) containing peptide was used as a model ligand to target liposomes to the integrin GPIIb-IIIa on activated platelets. Additionally, oligodextran surfactants incorporated into liposomes provided insight into the effect of vesicle perturbations on liposome clearance, and the importance of molecular geometry in designing oligosaccharide surface modifications. Together these studies demonstrate the feasibility of using peptides to guide liposomes to desired receptors, and illustrate the influence of vesicle stability on liposome interactions in vivo. Furthermore, they underscore the importance of simultaneously considering both targeting specificity and vesicle longevity in the design of effective targeted drug delivery systems.

Formulation and delivery mode affect disposition and activity of tyrphostin-loaded nanoparticles in the rat carotid model

Poor drug residence in the arterial wall hinders clinical implementation of local drug delivery strategies for the treatment of restenosis. A rat carotid model of vascular injury and intraluminal delivery of tyrphostin-containing polylactic acid (PLA) nanoparticles (NPs) were used to determine the relationship between residence properties and biological activity of different formulations and administration modes. The effects of delivery modes (denudation and delivery time) and formulation variables (adsorbed vs encapsulated drug, and NP size) on arterial drug/NP retention were examined. Antirestenotic effects of large (160 nm) and small (90 nm) tyrphostin-containing NPs, surface-absorbed tyrphostin, and systemic treatment were compared. Fluorescent NPs were used to study the spatial distribution of the carrier in the arterial wall. The decrease in arterial tyrphostin level over time fitted a biexponential model. Delivery time and pressure, endothelium integrity, particle size, and drug-polymer association affected local pharmacokinetics and the antirestenotic results after 14 days. The PLA-based tyrphostin NP formulation ensured a prolonged drug residence at the angioplasty site after single intraluminal application. Several readily adjustable formulation and procedural factors considerably modified arterial ingress of the drug-loaded NPs and governed their subsequent redistribution, tissue binding, elimination, and ensuing antirestenotic effect.

Preparation and characterization of gelatin surface modified PLGA microspheres

This study optimized conditions for preparing and characterizing gelatin surface modified poly (lactic-co-glycolic acid) (PLGA) copolymer microspheres and determined this system's interaction with fibronectin. Some gelatin microspheres have an affinity for fibronectin-bearing surfaces; these microspheres exploit the interaction between gelatin and fibronectin. PLGA copolymer microspheres were selected because they have reproducible and slow-release characteristics in vivo. The PLGA microspheres were surface modified with gelatin to impart fibronectin recognition. Dexamethasone was incorporated into these microspheres because dexamethasone is beneficial in chronic human diseases associated with extra fibronectin expression (eg, cardiovascular disease, inflammatory disorders, rheumatoid arthritis). The gelatin surface modified PLGA microspheres (prepared by adsorption, conjugation, and spray coating) were investigated and characterized by encapsulation efficiency, particle size, in vitro release, and affinity for fibronectin. The gelatin-coated PLGA microspheres had higher interaction with fibronectin compared with the other gelatin surface modified PLGA microspheres (adsorption and conjugation). Dexamethasone was released slowly (over 21 days) from gelatin surface modified PLGA microspheres.

Nanoparticulate delivery system of a tyrphostin for the treatment of restenosis

Restenosis, the principal complication of percutaneous transluminal coronary angioplasty is responsible for the 35-40% long-term failure rate following coronary revascularization. The neointimal formation, a morphological substrate of restenosis, is dependent on smooth muscle cells (SMC) proliferation and migration. Signal transduction through the platelet-derived growth factor (PDGF)/PDGF receptors system is involved in the process of post-angioplasty restenosis. The unsuccessful attempts to control restenosis by systemic pharmacological interventions have prompted many researchers to look for more promising therapeutic approaches such as local drug delivery. Tyrphostins are low molecular weight inhibitors of protein tyrosine kinases. We assessed the release kinetics and in vivo effects of nanoparticles containing PDGF-Receptor beta (PDGFRbeta) tyrphostin inhibitor, AG-1295. AG-1295-loaded poly(DL-lactide) (PLA) nanoparticles were prepared by spontaneous emulsification/solvent displacement technique. In vitro release rate and the impact of drug/polymer ratio on the nanoparticle size were determined. The degree of tyrosine phosphorylation was assessed by Western blot with phosphotyrosine-specific antibody in rat SMC extracts. Several bands characteristic of PDGF BB-stimulated SMC disappeared or weakened following tyrphostin treatment. Local intraluminal delivery of AG-1295-loaded PLA nanoparticles to the injured rat carotid artery had no effect on proliferative activity in medial and neointimal compartments of angioplastisized arteries, indicating a primary antimigration effect of AG-1295 on medial SMC.

Arterial uptake of biodegradable nanoparticles: effect of surface modifications

Restenosis is the reobstruction of an artery following interventional procedures such as balloon angioplasty or stenting. Local pharmacotherapeutic approaches using controlled release systems are under investigation to inhibit the regional pathophysiologic process of restenosis. We have been investigating biodegradable nanoparticles (100 +/- 39 nm in diameter, mean +/- sd) for the local intra-arterial drug delivery. The purpose of this study was to investigate nanoparticle surface modifications (see Table 1) to enhance their arterial uptake. The PLGA (polylactic polyglycolic acid copolymer) nanoparticles were formulated by an oil-in-water emulsion solvent evaporation technique using a 2-aminochromone (U-86983, Upjohn and Pharmacia) (U-86) as a model antiproliferative agent. The various formulations of nanoparticles were evaluated for the arterial wall uptake by using an ex-vivo dog femoral artery model. The selected formulations were then tested in vivo in acute dog femoral artery and pig coronary artery models. The nanoparticles surface modified with a cationic compound, didodecyldimethylammonium bromide (DMAB), demonstrated 7-10-fold greater arterial U-86 levels compared to the unmodified nanoparticles in different ex-vivo and in-vivo studies. The mean U-86 levels were 10.7 +/- 1.7 microg/10 mg (dog) and 6.6 +/- 0.6 microg/10 mg (pig) in the artery segments ( approximately 2 cm) which were infused with the nanoparticles. The pig coronary studies further demonstrated that the infusion of nanoparticles with higher U-86 loading reduced the arterial U-86 levels, whereas increasing the nanoparticle concentration in the infusion solutions increased the arterial U-86 levels. The biodistribution studies in pigs following coronary arterial administration of nanoparticles demonstrated disposition of U-86 in the myocardium and distally in the liver and the lung. The mechanism of enhanced arterial uptake of the DMAB surface modified nanoparticles seems to be due to the alteration in the nanoparticle surface charge. The unmodified nanoparticles had a zeta potential of -27.8 +/- 0.5 mV (mean +/- sem, n = 5), whereas the DMAB modified nanoparticles demonstrated a zeta potential of +22.1 +/- 3.2 mV (mean +/- sem, n = 5). The adsorption of DMAB to the nanoparticle surface followed the Freundlich isotherm with binding capacity k = 28.1 microg/mg and affinity constant p = 2. 33. In conclusion, surface modified nanoparticles have potential applications for intra-arterial drug delivery to localize therapeutic agents in the arterial wall to inhibit restenosis.

Arterial uptake of biodegradable nanoparticles for intravascular local drug delivery: results with an acute dog model

Biodegradable nanoparticles (NP) with a spherical diameter ranging from 70 to 160 nm were investigated for potential usefulness for the local intraluminal therapy of restenosis, the disease process responsible for arterial reobstruction following angioplasty. NPs containing a water-insoluble anti-proliferative agent U-86983 (U-86, Pharmacia and Upjohn, Kalamazoo, MI) were formulated from oil-water emulsions using biodegradable polymers such as poly(lactic acid-co-glycolic acid) (PLGA), and specific additives after particle formation, to enhance arterial retention using either heparin, didodecylmethylammonium bromide (DMAB), or fibrinogen, or combinations. Femoral and carotid arteries of male mongrel dogs were isolated in situ, and were then subjected to a balloon angioplasty. A NP suspension of a predetermined concentration was then infused into the artery for various durations. This was followed by a 30 min restoration of blood flow through the vessel. The arterial segments were excised and analyzed for drug levels. From the drug loading the NP and the drug levels in the artery, the quantity of nanoparticles retained was calculated and expressed as microgram per 10 mg dry arteries. In general, repeated short infusions of nanoparticle suspension (15 s x 4) were two-fold more effective in terms of higher arterial U-86 levels than a single prolonged infusion (60 s). A single 15 s infusion was not significantly different than a 60 s compared to non-modified NPs (39.2 +/- 2.5 and 49.1 +/- 2.4 vs. 21.5 +/- 0.6 micrograms/10 mg mean +/- s.e., respectively). A comparably enhanced NP uptake was noted with a combined heparin/DMAB modification. Increasing the concentration of NP in infusate from 5 to 30 mg ml-1 significantly increased arterial NP uptake level (from 22.5 +/- 3.5 to 83.7 +/- 1.4 micrograms/10 mg). Thus, the results support the view that modified nanoparticles along with optimized infusion conditions could enhance arterial wall drug concentrations of agents to treat restenosis.