Neointimal thickening after stent delivery of paclitaxel: change in composition and arrest of growth over six months

Applications of Nanotechnology in the Field of Cardiology

Cardiovascular diseases (CVDs) are a leading cause of death globally, demanding innovative therapeutic strategies. Nanoformulations, including nanoparticles, address challenges in drug delivery, stem cell therapy, imaging, and gene delivery. Nanoparticles enhance drug solubility, bioavailability, and targeted delivery, with gas microbubbles, liposomal preparations, and paramagnetic nanoparticles showing potential in treating atherosclerosis and reducing systemic side effects. In stem cell therapy, nanoparticles improve cell culture, utilizing three-dimensional nanofiber scaffolds and enhancing cardiomyocyte growth. Gold nanoparticles and poly(lactic-co-glycolic acid) (PLGA)-derived microparticles promote stem cell survival. Stem cell imaging utilizes direct labeling with nanoparticles for magnetic resonance imaging (MRI), while optical tracking employs dye-conjugated nanoparticles. In gene delivery, polymeric nanoparticles like polyethylenimine (PEI) and dendrimers, graphene-based carriers, and chitosan nanoparticles offer alternatives to virus-mediated gene transfer. The potential of magnetic nanoparticles in gene therapy is explored, particularly in hepatocellular carcinoma. Overall, nanoparticles have transformative potential in cardiovascular disease management, with ongoing research poised to enhance clinical outcomes.

Residual inflammatory risk predicts long-term outcomes following stenting for symptomatic intracranial atherosclerotic stenosis

BACKGROUND AND PURPOSE

Residual inflammatory risk (RIR) can predict the unfavourable outcomes in patients with minor ischaemic stroke. However, the impact of preprocedural RIR on long-term outcomes in patients with symptomatic intracranial atherosclerotic stenosis (sICAS) who underwent stenting remains understudied.

METHODS

This retrospective, single-centre cohort study evaluated consecutive patients with severe sICAS who underwent intracranial stenting. Patients were categorised into four groups based on preprocedural high-sensitivity C-reactive protein (hs-CRP) and low-density lipoprotein cholesterol (LDL-C): residual cholesterol inflammatory risk (RCIR, hs-CRP ≥3 mg/L and LDL-C ≥2.6 mmol/L), RIR (hs-CRP ≥3 mg/L and LDL-C <2.6 mmol/L), residual cholesterol risk (RCR, hs-CRP <3 mg/L and LDL-C ≥2.6 mmol/L) and no residual risk (NRR, hs-CRP <3 mg/L and LDL-C <2.6 mmol/L). The long-term clinical outcomes included recurrent ischaemic stroke and death. The long-term imaging outcomes consisted of in-stent restenosis (ISR) and symptomatic ISR (sISR) after stenting.

RESULTS

In this study, 952 patients were included, with 751 (78.9%) being male. Forty-six cases were categorised into the RCIR group, 211 into the RIR group, 107 into the RCR group and 588 into the NRR group. Patients with RCIR (adjusted HR 6.163; 95% CI 2.603 to 14.589; p<0.001) and RIR (adjusted HR 2.205; 95% CI 1.294 to 3.757; p=0.004) had higher risks of recurrent ischaemic stroke than those with NRR during the 54 months of median follow-up time. Patients with RCIR (adjusted HR 3.604; 95% CI 1.431 to 9.072; p=0.007) were more likely to occur ISR, and patients in the RIR group showed a significant increase in the risk of sISR (adjusted HR 2.402; 95% CI 1.078 to 5.351; p=0.032) compared with those in the NRR group with a median follow-up time of 11.9 months.

CONCLUSIONS

In patients with sICAS, preprocedural RIR may predict long-term recurrent ischaemic stroke, ISR and sISR following intracranial stenting.

The Ranger drug-coated balloon: advances in drug-coated technology for treatment of femoropopliteal segment arterial disease

Paclitaxel drug-coated balloons (DCBs) have been shown to improve patency and lower revascularization rates compared with plain old balloon angioplasty. DCBs continue to evolve by improving balloon-coating techniques that minimize the quantity of particles washed off into the bloodstream while maximizing drug retention and vascular-healing profile. Against this backdrop, it is clear that the future of antiproliferatives for the superficial femoral artery will focus on enhancements in device coating materials that will improve the efficiency of drug delivery. The Ranger DCB system recently gained US FDA approval for use. This review discusses the background of DCBs and how the Ranger DCB builds on these previous platforms based on experimental and clinical data.

Evolution of drug-eluting coronary stents: a back-and-forth journey from the bench-to-bedside

Coronary stents have revolutionized the treatment of coronary artery disease. Compared with balloon angioplasty, bare-metal stents effectively prevented abrupt vessel closure but were limited by in-stent restenosis due to smooth muscle cell proliferation and neointimal hyperplasia. The first-generation drug-eluting stent (DES), with its antiproliferative drug coating, offered substantial advantages over bare-metal stents as it mitigated the risk of in-stent restenosis. Nonetheless, they had several design limitations that increased the risk of late stent thrombosis. Significant advances in stent design, including thinner struts, enhanced polymers' formulation, and more potent antiproliferative agents, have led to the introduction of new-generation DES with a superior safety profile. Cardiologists have over 20 different DES types to choose from, each with its unique features and characteristics. This review highlights the evolution of stent design and summarizes the clinical data on the different stent types. We conclude by discussing the clinical implications of stent design in high-risk subsets of patients.

Multiple predictors of in-stent restenosis after stent implantation in symptomatic intracranial atherosclerotic stenosis

OBJECTIVE

This study aimed to identify predictors of intracranial in-stent restenosis (ISR) after stent placement in symptomatic intracranial atherosclerotic stenosis (ICAS).

METHODS

The authors retrospectively collected data from consecutive patients who suffered from symptomatic ICAS and underwent successful stent placement in Beijing Tiantan hospital. Eligible patients were classified into "ISR," "indeterminate ISR," or "no-ISR" groups by follow-up digital subtraction angiography or CT angiography. A multivariate logistic regression model was used to explore the predictors of intracranial ISR after adjustments for age and sex. In addition, ISR and no-ISR patients were divided into two groups based on the strongest predictor, and the incidence of ISR, recurrent stroke, and symptomatic ISR was compared between the two groups.

RESULTS

A total of 511 eligible patients were included in the study: 80 ISR, 232 indeterminate ISR, and 199 no-ISR patients. Elevated high-sensitivity C-reactive protein (hs-CRP; odds ratio [OR] 4.747, 95% confidence interval [CI] 2.253-10.01, p < 0.001), Mori type B and C (Mori type B vs Mori type A, OR 3.119, 95% CI 1.093-8.896, p = 0.033; Mori type C vs Mori type A, OR 4.780, 95% CI 1.244-18.37, p = 0.023), coronary artery disease (CAD; OR 2.721, 95% CI 1.192-6.212, p = 0.017), neutrophil/lymphocyte ratio (NLR; OR 1.474 95% CI 1.064-2.042, p = 0.020), residual stenosis (OR 1.050, 95% CI 1.022-1.080, p = 0.001) and concurrent intracranial tandem stenosis (OR 2.276, 95% CI 1.039-4.986, p = 0.040) synergistically contributed to the occurrence of intracranial ISR. Elevated hs-CRP (hs-CRP ≥ 3 mg/L) was the strongest predictor for ISR, and the incidence of ISR in the elevated hs-CRP group and normal hs-CRP group (hs-CRP < 3 mg/L) was 57.14% versus 21.52%, respectively, with recurrent stroke 44.64% versus 16.59%, and symptomatic ISR 41.07% versus 8.52%.

CONCLUSIONS

Elevated hs-CRP level, NLR, residual stenosis, Mori type B and C, CAD, and concurrent intracranial tandem stenosis are the main predictors of intracranial ISR, and elevated hs-CRP is crucially associated with recurrent stroke in patients with symptomatic ICAS after intracranial stent implantation.

Balloon-based drug coating delivery to the artery wall is dictated by coating micro-morphology and angioplasty pressure gradients

Paclitaxel coated balloon catheters (PCB) were developed as a polymer-free non-implantable alternative to drug eluting stents, delivering similar drug payloads in a matter of minutes. While PCB have shown efficacy in treating peripheral arterial disease in certain patient groups, restenosis rates remain high and there is no class effect. To help further optimize these devices, we developed a scanning electron microscopy (SEM) imaging technique and computational modeling approach that provide insights into the coating micromorphology dependence of in vivo drug transfer and retention. PCBs coated with amorphous/flaky or microneedle coatings were inflated for 60 sec in porcine femoral arteries. Animals were euthanized at 0.5, 24 and 72 h and treated arteries processed for SEM to image endoluminal coating distribution followed by paclitaxel quantification by mass spectrometry (MS). Endoluminal surfaces exhibited sparse coating patches at 0.5 h, predominantly protruding (13.71 vs 0.59%, P < 0.001), with similar micro-morphologies to nominal PCB surfaces. Microneedle coating covered a 1.5-fold endoluminal area (16.1 vs 10.7%, P = 0.0035) owing to higher proximal and distal delivery, and achieved 1.5-fold tissue concentrations by MS (1933 vs 1298 μg/g, P = 0.1745) compared to amorphous/flaky coating. Acute longitudinal coating distribution tracked computationally predicted microindentation pressure gradients (r = 0.9, P < 0.001), with superior transfer of the microneedle coatings attributed to their amplification of angioplasty contact pressures. By 24 h, paclitaxel concentration and coated tissue areas both declined by >93% even as nonprotruding coating levels were stable between 0.5 and 72 h, and 2.7-fold higher for microneedle vs flaky coating (0.64 vs 0.24%, P = 0.0195). Tissue retained paclitaxel concentrations at 24-72 h trended 1.7-fold higher post treatment with microneedle coating compared to the amorphous/flaky coating (69.9 vs 39.9 μg/g, P = 0.066). Thus, balloon based drug delivery is critically dependent on coating micromorphologies, with superior performance exhibited by micromorphologies that amplify angioplasty pressures.

Paclitaxel Drug-Coated Balloon Angioplasty Suppresses Progression and Inflammation of Experimental Atherosclerosis in Rabbits

Paclitaxel drug-coated balloons (DCBs) reduce restenosis, but their overall safety has recently raised concerns. This study hypothesized that DCBs could lessen inflammation and reduce plaque progression. Using 25 rabbits with cholesterol feeding- and balloon injury-induced lesions, DCB-percutaneous transluminal angioplasty (PTA), plain PTA, or sham-PTA (balloon insertion without inflation) was investigated using serial intravascular near-infrared fluorescence-optical coherence tomography and serial intravascular ultrasound. In these experiments, DCB-PTA reduced inflammation and plaque burden in nonobstructive lesions compared with PTA or sham-PTA. These findings indicated the potential for DCBs to serve safely as regional anti-atherosclerosis therapy.

Current concepts regarding drug dosing for peripheral stents

Drug-eluting stent (DES) are the mainstay therapy for the treatment of coronary artery disease. Stent design and drug-elution strategies have evolved over the years leading to the last generation DES which shows optimal safety and efficacy outcome. Peripheral arteries have different mechanical and biological features and the lessons learned from the coronary field have been difficult to introduce into the development of peripheral vascular technologies. First, due to its complex biomechanical behavior the use of metallic stents is limited in some vascular segments (i.e., distal superficial fermoral artery [SFA]). Also, peripheral vascular atherosclerosis is different containing higher levels of plaque burden and calcium. Finally, peripheral arterial disease tends to be more aggressive including longer lesions and higher incidence of total chronic occlusion. In general terms, restenosis in the peripheral vascular territory is more aggressive and occurs at a later time (~12 months) requiring a different pharmacokinetic profile compared to coronary technologies. Several strategies have been evaluated in the peripheral arteries raging from the bare metal stent to the drug coated balloon and drug eluting stent with outcome varying depending on the different field of application (i.e. SFA and below-the-knee). Results coming from the clinical trial are encouraging but further studies and direct comparison among the different technologies are demanded to determine the best therapy for peripheral vascular disease.

B'reshith

The Hebrew word "b'reshith" (בְּרֵאשִׁית) means "in the beginning". It is the first word and title of the Book of Genesis, and it describes a process of creation. The four authors were present at the beginning of Langer labs, and the purpose of this essay is to convey the scientific and technological zeitgeist that existed in the late 1970s and early 1980s, when Bob Langer began his exceptionally creative work. While Langer labs has branched into many other areas, Bob's unique ability to recognize important problems and entice people to look beyond their own disciplines to solve them was evident from the start. We focus on the two areas of most interest to Bob at the time, namely controlled release of macromolecules from polymers, and removal of heparin in order to prevent uncontrolled bleeding during surgery.

Understanding the Impact of Stent and Scaffold Material and Strut Design on Coronary Artery Thrombosis from the Basic and Clinical Points of View

The technology of percutaneous coronary intervention (PCI) is constantly being refined in order to overcome the shortcomings of present day technologies. Even though current generation metallic drug-eluting stents (DES) perform very well in the short-term, concerns still exist about their long-term efficacy. Late clinical complications including late stent thrombosis (ST), restenosis, and neoatherosclerosis still exist and many of these events may be attributed to either the metallic platform and/or the drug and polymer left behind in the arterial wall. To overcome this limitation, the concept of totally bioresorbable vascular scaffolds (BRS) was invented with the idea that by eliminating long-term exposure of the vessel wall to the metal backbone, drug, and polymer, late outcomes would improve. The Absorb-bioabsorbable vascular scaffold (Absorb-BVS) represented the most advanced attempt to make such a device, with thicker struts, greater vessel surface area coverage and less radial force versus contemporary DES. Unfortunately, almost one year after its initial approval by the U.S. Food and Drug Administration, this scaffold was withdrawn from the market due to declining devise utilization driven by the concerns about scaffold thrombosis (ScT) seen in both early and late time points. Additionally, the specific causes of ScT have not yet been fully elucidated. In this review, we discuss the platform, vascular response, and clinical data of past and current metallic coronary stents with the Absorb-BVS and newer generation BRS, concentrating on their material/design and the mechanisms of thrombotic complications from the pre-clinical, pathologic, and clinical viewpoints.

Defining drug and target protein distributions after stent-based drug release: Durable versus deployable coatings

BACKGROUND

Innovations in drug eluting stent designs make it increasingly important to develop models for differentiating performance through spatial definition of drug, receptor binding and cell state.

METHODS

Two designs of sirolimus analog eluting stents were implanted into porcine coronary arteries for 28, 60 or 90 days (n = 9/time point), durable coating (Xience) and deployable absorbable coating (MiStent). Explanted arteries were evaluated for drug content (n = 3/time point) by LC-MS/MS and for drug and target protein (mTOR) distributions by immunofluorescence (IF, n = 6/time point). A computational model was developed to predict drug release and arterial distribution maps.

RESULTS

Both stents released the majority of drug load by 28 days, with different tissue retention efficiencies (91.4 ± 4.9% MiStent versus 21.5 ± 1.9% Xience, P < 0.001). Computational modeling of MiStent coating deployment and microcrystal dissolution recapitulated in vivo drug release and net tissue content and predicted that >98.5% of deployed drug remains crystalline through 90 days. Immunofluorescence and computational modeling showed peristrut drug localization for both stents, with similar peaks, but high interstrut levels only at sites of coating deployment from the absorbable coating. Co-localization of mTOR-IF with drug-IF for both devices showed persistent drug effects, though with differential drug-receptor pharmacokinetics.

CONCLUSIONS

Immunofluorescence and computational modeling provide insights into drug distribution and binding status that can help differentiate drug delivery technologies. Herein we found that tissue deployment of slow dissolving crystalline drug particles results in temporally and spatially more uniform drug delivery to interstrut zones that might otherwise be under-dosed without excess peristrut drug.

Coronary Stents in Diabetic Patients: State of the Knowledge

PURPOSE OF REVIEW

This review article aims to summarize the findings of the most relevant research that compared the use of paclitaxel vs. "limus" based drug eluting stent (DES) in diabetic patients and to define the current state of knowledge with new stent technologies in this patient population.

RECENT FINDINGS

Since drug eluting stents (DES) were introduced, it has been of great interest to establish whether paclitaxel or sirolimus eluting stents have the same safety and efficacy features for patients with coronary artery disease. The answer to this question is particularly relevant for diabetic patients. Several randomized trials, registry-based studies, and meta-analyses have assessed the performance of these different DES in diabetic patients. The most recently published data favors limus over paclitaxel DES in diabetic patients, but most of these studies compared first vs. second generation DES with the inherent caveats of comparing different platforms, alloys, and drug delivery vehicles. In this literature review, we found that there is robust evidence favoring the use of DES over bare metal stents in diabetic patients with coronary artery disease. We also found that the current state of knowledge is that the everolimus eluting stents have better safety and efficacy than paclitaxel eluting stents in diabetic patients and hence should be the preferred choice. New revascularization strategies including bio-absorbable scaffolds, polymer free stents, and bio-degradable polymers are being studied in diabetic patients with encouraging results.

Small molecule-mediated induction of miR-9 suppressed vascular smooth muscle cell proliferation and neointima formation after balloon injury

Pathologic proliferation and migration of vascular smooth muscle cells (VSMCs) exacerbate cardiovascular disease. MicroRNAs (miRNAs), as endogenous inhibitors of protein synthesis, are expected to modulate pathologic proliferation of VSMCs. Here we report that both platelet-derived growth factor receptor (PDGFR) targeting miR-9 and a small molecule that increases miR-9 can inhibit the serum-induced proliferation of VSMCs. First, based on miRNA-target prediction databases and empirical data, we have selected miR-9 as a potent anti-proliferative miRNA in VSMCs. Further examination indicated that miR-9 directly targets PDGFR disrupting downstream signaling cascades, and this resulted in inhibition of VSMC proliferation and migration. Exogenous delivery of miR-9 inhibited VSMC proliferation in vitro, and a small molecule that increased miR-9 expression also inhibited neointima formation following balloon injury in vivo. We provide evidence of miRNA-mediated modulation of VSMC proliferation and further demonstrate that small molecule-mediated regulation of miRNA targeting a key regulator of VSMC proliferation is a viable therapeutic strategy for treating vascular disease involving pathologic VSMC proliferation such as restenosis.

From Nonclinical Research to Clinical Trials and Patient-registries: Challenges and Opportunities in Biomedical Research

The most important challenge faced by human beings is health. The only way to provide better solutions for health care is innovation, true innovation. The only source of true innovation is research, good research indeed. The pathway from a basic science study to a randomized clinical trial is long and not free of bumps and even landmines. These are all the obstacles and barriers that limit the availability of resources, entangle administrative-regulatory processes, and restrain investigators' initiatives. There is increasing demand for evidence to guide clinical practice but, paradoxically, biomedical research has become increasingly complex, expensive, and difficult to integrate into clinical care with increased barriers to performing the practical aspects of investigation. We face the challenge of increasing the volume of biomedical research and simultaneously improving the efficiency and output of this research. In this article, we review the main stages and methods of biomedical research, from nonclinical studies with animal and computational models to randomized trials and clinical registries, focusing on their limitations and challenges, but also providing alternative solutions to overcome them. Fortunately, challenges are always opportunities in disguise.

Coronary Artery Aneurysms: A Review of the Epidemiology, Pathophysiology, Diagnosis, and Treatment

Coronary artery aneurysms (CAAs) are uncommon and describe a localized dilatation of a coronary artery segment more than 1.5-fold compared with adjacent normal segments. The incidence of CAAs varies from 0.3 to 5.3%. Ever since the dawn of the interventional era, CAAs have been increasingly diagnosed on coronary angiography. Causative factors include atherosclerosis, Takayasu arteritis, congenital disorders, Kawasaki disease (KD), and percutaneous coronary intervention. The natural history of CAAs remains unclear; however, several recent studies have postulated the underlying molecular mechanisms of CAAs, and genome-wide association studies have revealed several genetic predispositions to CAA. Controversies persist regarding the management of CAAs, and emerging findings support the importance of an early diagnosis in patients predisposed to CAAs, such as in children with KD. This review aims to summarize the present knowledge of CAAs and collate the recent advances regarding the epidemiology, etiology, pathophysiology, diagnosis, and treatment of this disease.

Modeling gold nanoparticle-eluting spacer degradation during brachytherapy application with in situ dose painting

OBJECTIVE

To investigate the dosimetric impact of slow vs burst release of gold nanoparticles (GNPs) from biodegradable brachytherapy spacers loaded with GNPs, which has been proposed to increase therapeutic efficacy during brachytherapy application with in situ dose painting.

METHODS

Mathematical models were developed based on experimental data to study the release of GNPs from a spacer designed with poly(lactic-co-glycolic acid) polymer. The models addressed diffusion controlled-release process and poly(lactic-co-glycolic acid) degradation kinetics that were used to determine GNP concentration profiles in tumour and the corresponding dose enhancement.

RESULTS

The results show a significant delay of GNP diffusion in the tumour in comparison to burst release assumed in previous studies. The model for diffusion controlled-release process and the model for combined processes of both diffusion and polymer degradation indicated that it may take about 25 and 45 days, respectively, for all GNPs to release from the spacer. Based on tumour concentration profiles, a significant dose enhancement factor (>2) could be attained at a tumour distance of 5 mm from a spacer loaded with 2-, 5- and 10-nm GNP sizes.

CONCLUSION

The results highlight the need to account for the slow release of GNPs from spacers and polymer biodegradation in research development of the GNP-eluting spacers. The findings suggest the use of radioisotopes with longer half-lives, such as iodine-125, in comparison with others with shorter half-lives such as Pd-103 and Cs-131. Advances in knowledge: The study provides a scientific platform and basis for research development of GNP-eluting spacers that can be used during brachytherapy to boost dose to tumour subvolumes, towards enhancing therapeutic efficacy. It concludes that the use of iodine-125 would be more feasible.

Current State of Bioabsorbable Polymer-Coated Drug-Eluting Stents

Drug-eluting stents (DES) have been shown to significantly reduce clinical and angiographic restenosis compared to bare metal stents (BMS). The polymer coatings on DES elute antiproliferative drugs to inhibit intimal proliferation and prevent restenosis after stent implantation. Permanent polymers which do not degrade in vivo may increase the likelihood of stent-related delayed arterial healing or polymer hypersensitivity. In turn, these limitations may contribute to an increased risk of late clinical events. Intuitively, a polymer which degrades after completion of drug release, leaving an inert metal scaffold in place, may improve arterial healing by removing a chronic source of inflammation, neoatherosclerosis, and/or late thrombosis. In this way, a biodegradable polymer may reduce late ischemic events. Additionally, improved healing after stent implantation could reduce the requirement for long-term dual antiplatelet therapy and the associated risk of bleeding and cost. This review will focus on bioabsorbable polymer-coated DES currently being evaluated in clinical trials.

Percutaneous Transluminal Angioplasty and Drug-Eluting Stents for Infrapopliteal Lesions in Critical Limb Ischemia (PADI) Trial

Supplemental Digital Content is available in the text.

Background—

Endovascular infrapopliteal treatment of patients with critical limb ischemia using percutaneous transluminal angioplasty (PTA) and bail-out bare metal stenting (BMS) is hampered by restenosis. In interventional cardiology, drug-eluting stents (DES) have shown better patency rates and are standard practice nowadays. An investigator-initiated, multicenter, randomized trial was conducted to assess whether DES also improve patency and clinical outcome of infrapopliteal lesions.

Methods and Results—

Adults with critical limb ischemia (Rutherford category ≥4) and infrapopliteal lesions were randomized to receive PTA±BMS or DES with paclitaxel. Primary end point was 6-month primary binary patency of treated lesions, defined as ≤50% stenosis on computed tomographic angiography. Stenosis >50%, retreatment, major amputation, and critical limb ischemia–related death were regarded as treatment failure. Severity of failure was assessed with an ordinal score, ranging from vessel stenosis through occlusion to the clinical failures. Seventy-four limbs (73 patients) were treated with DES and 66 limbs (64 patients) received PTA±BMS. Six-month patency rates were 48.0% for DES and 35.1% for PTA±BMS (P=0.096) in the modified-intention-to-treat and 51.9% and 35.1% (P=0.037) in the per-protocol analysis. The ordinal score showed significantly worse treatment failure for PTA±BMS versus DES (P=0.041). The observed major amputation rate remained lower in the DES group until 2 years post-treatment, with a trend toward significance (P=0.066). Less minor amputations occurred after DES until 6 months post-treatment (P=0.03).

Conclusions—

In patients with critical limb ischemia caused by infrapopliteal lesions, DES provide better 6-month patency rates and less amputations after 6 and 12 months compared with PTA±BMS.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00471289.

Flexible Coils with a Drug-Releasing Hydrophilic Coating: A New Platform for Controlled Delivery of Drugs to the Eye?

Delivery of drugs to the front-side of the eye is routinely done through eye drops. It is known that approximately 80% of each eye-drop is lost, as a result of rapid clearance of the tear fluid via the naso-lacrymal canal. Consequently, repeated administration through several droplets is usually necessary to achieve a desired effect, such as widening of the pupil prior to corneal surgery. A new ocular drug delivery device was studied. The new device is believed to provide a basis for a more convenient and efficient method for ocular drug delivery. The device is a metallic coil with a hydrophilic, drug-containing polymeric coating. The coil is placed in the conjuctival fornix (under the lower eye-lid) and the drug is slowly released by diffusion into the tear fluid. The capacity of the device could be increased by using the lumen of the coils as a depot for the drug to be released. Preliminary experiments with the new device were performed largely in vitro and in vivo. The latter experiments involved the release of a fluorescent dye and atropine (a potent mydriatic agent) in the eye of several healthy volunteers. The first results obtained with the new device indicate its potential utility. More research and development work is required to define the optimal design of the coil in order to minimize the risk of irritation. Furthermore, the parameters that define the kinetics of the intraocular drug release must be defined and optimized with respect to the exact application.

Adding Functions to Biomaterial Surfaces through Protein Incorporation

The concept of biomaterials has evolved from one of inert mechanical supports with a long-term, biologically inactive role in the body into complex matrices that exhibit selective cell binding, promote proliferation and matrix production, and may ultimately become replaced by newly generated tissues in vivo. Functionalization of material surfaces with biomolecules is critical to their ability to evade immunorecognition, interact productively with surrounding tissues and extracellular matrix, and avoid bacterial colonization. Antibody molecules and their derived fragments are commonly immobilized on materials to mediate coating with specific cell types in fields such as stent endothelialization and drug delivery. The incorporation of growth factors into biomaterials has found application in promoting and accelerating bone formation in osteogenerative and related applications. Peptides and extracellular matrix proteins can impart biomolecule- and cell-specificities to materials while antimicrobial peptides have found roles in preventing biofilm formation on devices and implants. In this progress report, we detail developments in the use of diverse proteins and peptides to modify the surfaces of hard biomaterials in vivo and in vitro. Chemical approaches to immobilizing active biomolecules are presented, as well as platform technologies for isolation or generation of natural or synthetic molecules suitable for biomaterial functionalization.

Survival of Endothelial Cells in vitro on Paclitaxel-loaded Coronary Stents

Coronary stents that are developed for use with balloon angioplasty are known to cause acute occlusion and long-term stenosis. It is likely that a controlled release of drugs at the site of stent implantation might inhibit the proliferation of vascular smooth muscle cells (VSMC) and reduce restenosis. However, if the drug is necrotic and affects cell survival near the implant, it may interrupt the local tissue regeneration. Different methods have been used for the immobilization of drugs with stents to get an effective concentration that inhibits cell proliferation. The objective of this study is to assess the effectiveness of Paclitaxel-loaded stents by immobilization with a biodegradable polymer, to inhibit cell proliferation. The cells used for the evaluation are human umbilical vein endothelial cells (HUVEC) and the proliferation rate of these cells on the drug-coated stent is compared against an uncoated stent for a 72-h period. Evaluations were also made to differentiate between cell apoptosis and necrosis to prove that the drug released is not deleterious to the surrounding tissue.

While a similar initial cell adhesion is observed in bare and coated stents, the proliferation of HUVEC is negligible when grown on a drug-coated stent (p < 0.001). By specific staining techniques, the cells on the drug-coated stents are found to be apoptotic and not necrotic, throughout the evaluation period. In vitro leukocyte adhesion and platelet deposition on the drug-coated stents are found to be low when they are exposed to human blood and platelet-rich plasma (PRP), suggesting that the coated stents may not be thrombogenic in vivo. Therefore, drug coating of stents using the described technique may have a considerable promise for the prevention of neointimal proliferation, restenosis, and associated failure of angioplasty.

Sustained Efficacy and Arterial Drug Retention by a Fast Drug Eluting Cross-Linked Fatty Acid Coronary Stent Coating

The long held assumption that sustained drug elution from stent coatings over weeks to months is imperative for clinical efficacy has limited the choice for stent coating materials. We developed and evaluated an omega-3 fatty acid (O3FA) based stent coating that is 85% absorbed and elutes 97% of its Sirolimus analog (Corolimus) load within 8d of implantation. O3FA coated stents sustained drug levels in porcine coronary arteries similarly to those achieved by slow-eluting durable coated Cypher Select Plus Stents and with significantly lower levels of granuloma formation and luminal stenosis. Computational modeling confirmed that diffusion and binding constants of Corolimus and Sirolimus are identical and explained that the sustained retention of Corolimus was facilitated by binding to high affinity intracellular receptors (FKBP12). First in man outcomes were positive-unlike Cypher stents where late lumen loss drops over 6 month, there was a stable effect without diminution in the presence of O3FA. These results speak to a new paradigm whereby the safety of drug eluting stents can be optimized through the use of resorbable biocompatible coating materials with resorption kinetics that coincide with the dissociation and tissue elimination of receptor-bound drug.

Cell Cycle Regulation of Smooth Muscle Cells--Searching for Inhibitors of Neointima Formation: Is Combretastatin A4 an Alternative to Sirolimus and Paclitaxel?

PURPOSE

To compare the effects of sirolimus, paclitaxel, and combretastatin A4 (CA4) on regulatory proteins of the cell cycle in proliferating smooth muscle cells (SMCs).

MATERIALS AND METHODS

Human aortic SMCs were treated with sirolimus, paclitaxel, and CA4 at 5 × 10(-9) mol/L. After 1 day, half of the cells were harvested (DAY1 group). The treatment medium of the other half was replaced with culture medium on day 4, and those cells were harvested on day 5 (DAY5 group). Cyclins D1, D2, E, and A and cyclin-dependent kinase (CDK) inhibitors p16, p21, and p27 were detected by Western blot technique. Quantification was performed by scanning densitometry of the specific bands.

RESULTS

In the DAY1 group, treatment with sirolimus resulted in decreased intracellular levels of cyclins D2 and A (P < .05). Increased D cyclins and reduced levels of cyclins E and A (P < .05) in the DAY5 group indicated a permanent G1/S block by sirolimus. Paclitaxel led to only slight alterations of cyclin and CDK inhibitor expression (P > .05). In the DAY1 group, CA4 decreased intracellular levels of cyclins D2, E, and A (P < .05). Despite recovery effects in the DAY5 group (increase of cyclins D1, D2, and A compared with DAY1 group; P < .05), the upregulation of the CDK inhibitor p21, increased D cyclins, and decreased cyclins E and A (P < .05) are compatible with a G1 arrest.

CONCLUSIONS

CA4 is a stronger inhibitor of the SMC cycle than sirolimus or paclitaxel and may represent an alternative for drug-eluting stents in atherosclerotic luminal stenosis. The effect of CA4 on neointima formation should be evaluated further.

Effect of pretreatment of ezetimibe/simvastatin on arterial healing and endothelialization after drug-eluting stent implantation in a porcine coronary restenosis model

Background and Objectives

We sought to evaluate the effect of the early use of ezetimibe/simvastatin (Vytorin®) on arterial healing and endothelialization after the implantation of a drug-eluting stent (DES) in a porcine model of coronary restenosis.

Materials and Methods

A total of 20 pigs (40 coronary arteries) were randomly allocated to a pretreatment or no treatment group. The pretreatment group (n=20) received oral ezetimibe/simvastatin (10/20 mg) daily for 7 days before stenting and the no pretreatment group (n=20) did not. All pigs were treated with ezetimibe/simvastatin (10/20 mg) daily after stenting for 4 weeks. Stenting was performed using a bare-metal stent (BMS, n=10) and three types of DES: biolimus A9-eluting stent (BES, n=10), zotarolimus-eluting stent (ZES, n=10), and everolimus-eluting stents (EES, n=10). Four weeks later, pigs underwent a follow-up coronary angiography and were sacrificed for histopathologic analysis.

Results

There were no significant differences between the pretreatment and no pretreatment groups in the internal elastic lamina area, lumen area, neointima area, stenotic area, injury score, fibrin score, and inflammation score. In both groups, the fibrin score was higher in pigs with DES than in BMS, particularly in ZES and EES. The inflammatory score was not different between DES and BMS.

Conclusion

In a porcine model of coronary restenosis, pretreatment with ezetimibe/simvastatin before DES implantation failed to improve arterial healing and endothelialization compared to treatment after stenting.

Local delivery of paclitaxel in the treatment of peripheral arterial disease

BACKGROUND

Despite advancements from balloon angioplasty to drug-eluting stents, primary patency rates after endovascular revascularization of peripheral artery disease have remained inferior compared to surgery. Endovascular revascularization has been limited by restenosis and mechanical stent failure. Thus, there is increased research into other nonstent-based local drug delivery modalities, which can provide an active drug to inhibit restenosis focally and avoid the risk of systemic adverse effects.

METHODS

This review will summarize the unique properties of paclitaxel and studies on paclitaxel local delivery for the treatment of peripheral artery disease. A MEDLINE search for relevant peer-reviewed scientific literature published in English was conducted. Search terms included but were not limited to paclitaxel pharmacodynamics, paclitaxel local drug delivery, and drug eluting balloons, with a focus on the use of paclitaxel in the context of coronary and peripheral vascular disease.

RESULTS

The primary search produced 182 results of which 51 papers were relevant. Of the 51 relevant papers, 27 were original research papers and 24 were either review papers, commentary or opinion papers.

CONCLUSIONS

Paclitaxel has several chemical properties, which make it ideal for local drug delivery including its hydrophobicity, ability to concentrate into the arterial intima layer and prolonged effect on cells even after brief exposure periods. Local delivery of paclitaxel via injection catheters, balloon catheters and coated balloons has shown encouraging results in terms of efficacy and safety in small-scale animal and clinical studies. Additional preclinical and clinical studies are needed to determine the long-term efficacy and safety of these treatments in humans.

Myocardial drug distribution generated from local epicardial application: potential impact of cardiac capillary perfusion in a swine model using epinephrine

Prior studies in small mammals have shown that local epicardial application of inotropic compounds drives myocardial contractility without systemic side effects. Myocardial capillary blood flow, however, may be more significant in larger species than in small animals. We hypothesized that bulk perfusion in capillary beds of the large mammalian heart not only enhances drug distribution after local release, but also clears more drug from the tissue target than in small animals. Epicardial (EC) drug releasing systems were used to apply epinephrine to the anterior surface of the left heart of swine in either point-sourced or distributed configurations. Following local application or intravenous (IV) infusion at the same dose rates, hemodynamic responses, epinephrine levels in the coronary sinus and systemic circulation, and drug deposition across the ventricular wall, around the circumference and down the axis, were measured. EC delivery via point-source release generated transmural epinephrine gradients directly beneath the site of application extending into the middle third of the myocardial thickness. Gradients in drug deposition were also observed down the length of the heart and around the circumference toward the lateral wall, but not the interventricular septum. These gradients extended further than might be predicted from simple diffusion. The circumferential distribution following local epinephrine delivery from a distributed source to the entire anterior wall drove drug toward the inferior wall, further than with point-source release, but again, not to the septum. This augmented drug distribution away from the release source, down the axis of the left ventricle, and selectively toward the left heart follows the direction of capillary perfusion away from the anterior descending and circumflex arteries, suggesting a role for the coronary circulation in determining local drug deposition and clearance. The dominant role of the coronary vasculature is further suggested by the elevated drug levels in the coronary sinus effluent. Indeed, plasma levels, hemodynamic responses, and myocardial deposition remote from the point of release were similar following local EC or IV delivery. Therefore, the coronary vasculature shapes the pharmacokinetics of local myocardial delivery of small catecholamine drugs in large animal models. Optimal design of epicardial drug delivery systems must consider the underlying bulk capillary perfusion currents within the tissue to deliver drug to tissue targets and may favor therapeutic molecules with better potential retention in myocardial tissue.

In vitro evaluation of cenderitide-eluting stent I -an antirestenosis and proendothelization approach

Despite the success that drug-eluting stents (DESs) have achieved for minimizing in-stent restenosis (ISR), the antirestenotic agents used in DES have been implicated in delayed endothelial healing and impairment of endothelial functions. Cenderitide (CD-NP) is a novel antiproliferation chimeric peptide of semiendothelial origin; thus, this paper aims to demonstrate the selectivity aspect of this new peptide via in vitro evaluation on key players in ISR-smooth muscle cells (SMCs) and endothelial cells. The microbicinchoninic acid protein assay was used to investigate the CD-NP release from films and stents. Cenderitide-containing films blended with poly(ethylene glycol) and its copolymer exhibited higher release kinetics compared with neat poly(ε-caprolactone) (PCL) formulation. Cenderitide-eluting stents (CES) was produced by coating bare metallic stents with CD-NP entrapped PCL using an ultrasonic spray coater. The investigation of CD-NP on in vitro cells revealed that CD-NP inhibits human coronary smooth muscle cells (HCaSMCs) proliferation but exhibits no effects on human umbilical vein endothelial cells (HUVECs) proliferation. Moreover, CD-NP released up to 7 days displayed inhibitory effects on SMCs proliferation. The CES produced in this work shows that the released CD-NP inhibits HCaSMCs proliferation but did not hamper HUVECs proliferation in vitro, suggesting that it has potential to reduce ISR without retarding the endothelialization healing in vivo.

The real world experience of the biodegradable polymer-coated sirolimus-eluting coronary stent system: Results From an "All-Comers" Clinical Experience

OBJECTIVES

This INDOLIMUS Registry sought to evaluate the safety and efficacy of the biodegradable polymer coated Indolimus(®) sirolimus-eluting coronary stent for the treatment of coronary artery disease across a wide range of patients treated in routine clinical practice, including those with high-risk characteristics and complex lesions.

BACKGROUND

First-generation drug-eluting stents utilize nonbiodegradable polymeric coatings, whose persistent presence in the arterial wall may negatively affect long-term outcomes. It has been hypothesized that persistent presence of polymer may compromise the safety of drug-eluting stents, and that therefore biodegradable polymer coatings might reduce late adverse events in an unselected patient population.

METHODS

All 530 consecutive unselected patients (415 males and 115 females) included who underwent percutaneous coronary intervention at the Sri Venkateswara Institute of Medical Sciences, Tirupati, India between August 2012 and March 2013, with an in-hospital, at 30-days and at 6-months follow-up. Retrospective analysis of those data had been done.

RESULTS

A total of 617 lesions were treated in 530 enrolled patients (mean age 54.9 ± 10.8 years) with average stent length of 18.8 ± 6.0 mm. An average of 1.18 stents was implanted per patient. The patients' characteristics are noted as having 169 (31.9%) patients of diabetics and 215 (40.6%) hypertension. Smoking, alcoholism and tobacco chewing were found in 273 (51.5%), 130 (24.5%) and 17 (3.2%), respectively. The indications for intervention were unstable angina in 77 (14.5%) and previous myocardial infarction in 56 (10.6%) of the patients. Lesions were of type B2 in 264 (42.7%) and type C in 127 (20.6%). Stent delivery was successful in all cases and in-hospital, 30-days and 6-months follow-up of all 530 patients was obtained. The incidence of any major adverse cardiac events at in-hospital, at 30-days and at 6-months were 5 (0.94%), 8 (1.52%), and 18 (3.40%), respectively. Long term follow-up of this registry is ongoing to confirm safety and efficacy profiles.

CONCLUSIONS

The relatively low event rate that was observed in INDOLIMUS Registry indicates that the biodegradable polymer coated Indolimus(®) sirolimus-eluting coronary stent can achieve excellent clinical performances in a large group of patients. © 2013 Wiley Periodicals, Inc.

Water soluble polymer films for intravascular drug delivery of antithrombotic biomolecules

Over the past 10 years, the number of percutaneous coronary intervention (PCI) procedures performed in the United States has increased by 33%; however, restenosis, which inhibits complete functional recovery of the vessel wall, remains a complication of this procedure. To traverse the complications associated with PCI, the investigation of therapeutic delivery has become an integral topic in modern research. One such therapeutic, a mimic of the proteoglycan decorin, termed DS-SILY, can mask exposed collagen and thereby effectively decrease platelet activation, has recently been developed by our lab. Drawing inspiration from coating technologies developed by the pharmaceutical industry, a fast-dissolving polymer film has been developed to deliver active therapeutic agents from a balloon catheter during PCI. This research investigates the release of DS-SILY from fast-dissolving polymer films composed of poly(vinyl alcohol) (PVA) and poly(ethylene glycol) (PEG). Thin, uniform polymer films were produced via spin coating technique. The dissolution speed of the polymer films was found to be dependent on the concentration of polymer solution, where at least 65% of the films were shown to dissolve into nanometer sized polymer fragments within 2 min. DS-SILY, up to 6.26 μg/cm(2), was loaded into the films and functional release of the mimic was demonstrated by its successful binding to collagen upon release. Furthermore, DS-SILY released from films resulted in increased platelet inhibition. These results indicate that use of fast-dissolving polymer films allow for the successful release of biomolecules and further investigation of their use for localized drug delivery during PCI procedures is warranted.

Effects of the simultaneous use of drug-eluting stents and statins in an atherosclerotic animal model

INTRODUCTION

The use of statins and medicated stents (MS) is the best available therapy for the treatment of severe coronary disease in selected cases. However, the vascular effects of the simultaneous use of both therapies are unknown.

MATERIALS AND METHODS

An experimental study was carried out on 60 NZ rabbits with advanced atherosclerosis, distributed in four groups of 15 animals each. Group 1: Control. Group 2: paclitaxel-eluting stent (PES) in the thoracic aorta. Group 3: Atorvastatin 2.5mg/day po+PES implant, and Group 4: Atorvastatin 2.5mg/day po. They were followed up at 30, 60 and 90 days. Histo-morphometric analyses were carried out.

RESULTS

A total of 60 PES were successfully implanted. One animal from Group 3 died due to respiratory infection. PES increased the lumen diameter and area, as well as the vessel area; atorvastatin induced a potent plaque regression. In the PES group, the lumen diameter was 4.25±0.0mm, lumen area was 14.2±0.4mm(2), vessel area was 16.7±0.0mm(2), and plaque/media area ratio was 0.1±0.0. In the PES+atorvastatin group the measurements were 4.9±0.1mm (p<0.001), 18.6±0.8mm(2) (p=0.005), 21.6±0.9mm(2) (p=0.007) and 0.8±0.08 (p=0.032), respectively.

CONCLUSIONS

Our results confirm the potent synergistic mechanical effect of the PES and plaque regression of the statins in an animal model with advanced atherosclerosis.

First in vitro and in vivo results of an anti-human CD133-antibody coated coronary stent in the porcine model

BACKGROUND

Drug-eluting stents successfully reduce restenosis at the cost of delayed re-endothelialization. A novel concept to enhance re-endothelialization is the use of antibody-coated stents which capture circulating progenitor cells. A CD34-positive-cell-capturing stent was recently developed with conflicting clinical results. CD133 is a glycoprotein expressed on circulating hematopoietic and putative endothelial-regenerating cells and may be superior to CD34.

OBJECTIVE

The aim of our study was to develop a CD133-cell-capturing bare-metal stent and investigate feasibility, safety, and efficacy of CD133-stents in terms of re-endothelialization and neointima inhibition.

METHODS AND RESULTS

Anti-human CD133-antibodies were covalently attached to bare-metal stents. In vitro, binding capacity of CD133-stents was studied, revealing a significantly higher affinity of human CD133-positive cells to CD133-stents compared with mononuclear cells (MNCs). In vivo, 15 landrace pigs received BMS and CD133-stents in either RCX or LAD (n = 30 stents). Re-endothelialization was examined on day 1 (n = 4), 3 (n = 4) and day 7 (n = 4) using scanning electron microscopy. In histology, injury and inflammatory scores, as well as diameter restenosis were evaluated after day 7 (n = 3), 14 (n = 4), and 28 (n = 2). Overall no reduction in re-endothelialization, diameter stenosis or inflammatory score was seen with CD133-stents.

CONCLUSION

Stent coating with anti-human CD133-antibodies was successfully achieved with effective binding of CD133-positive cells. However, in vivo, no difference in re-endothelialization or neointima formation was evident with the use of CD133-stents compared with BMS. The low number of circulating CD133-positive cells and an increase in unspecific binding of MNCs over time may account for the observed lack of efficacy.

Study of drug-eluting coating on metal coronary stent

Drug-eluting stent has been proved to decrease the restenosis caused by the stent implantation, owing to the existence of a drug-eluting coating on the stent. For ensuring the effectivity and security of the drug-eluting stent during the service period, the uniform surface, good deformation and stabilized drug release behavior of the stents should be satisfied. In this study, the performances mentioned were studied on stainless steel stents. The results showed that the surface morphology of the coating was affected by the sorts of solvent, the parameters of the spraying process and the addition of the plasticizer. The drug-eluting profile of the coating was influenced by the plasticizer content and PLGA/drug ratio of the coating. Meanwhile, the plasticizer as an additional agent obviously increased the deformation performance of the coating. Optimized parameters for preparation of the drug-eluting coating were investigated to obtain a drug-eluting coating with good integrated performances.

Stent elution rate determines drug deposition and receptor-mediated effects

Drug eluting stent designs abound and yet the dependence of efficacy on drug dose and elution duration remains unclear. We examined these issues within a mathematical framework of arterial drug distribution and receptor binding following stent elution. Model predictions that tissue content linearly tracks stent elution rate were validated in porcine coronary artery sirolimus-eluting stents implants. Arterial content varied for stent types, progressively declining from its Day 1 peak and tracking with rate-limiting drug elution--near zero-order release was three-fold more efficient at depositing drug in the stented lesion than near first-order release. In vivo data were consistent with an overabundance of non-specific sirolimus-binding sites relative to the specific receptors and to the delivered dose. The implication is that the persistence time of receptor saturation and effect is more sensitive to duration of elution than to eluted amount. Consequently, the eluted amount should be sufficiently high to saturate receptors at the target lesion, but dose escalation alone is an inefficient strategy for prolonging the duration of sirolimus deposition. Moreover, receptor saturating drug doses are predicted to be most efficacious when eluted from stents in a constant zero order fashion as this maximizes the duration of elution and receptor saturation.

Preparation of injectable auto-forming alginate gel containing simvastatin with amorphous calcium phosphate as a controlled release medium and their therapeutic effect in osteoporosis model rat

Highly soluble amorphous calcium phosphate powder (ACP) was added to the alginate gel as a buffering agent, in an attempt to enable widely controlled release while avoiding an acidification of the gel-environment. Therapeutic effects of the ACP-containing alginate gel which slowly releases a drug, simvastatin, on osteoporosis model rats were examined. A model drug, simvastatin, incorporated in the alginate gel with ACP up to 0.5%, was continuously released for a long time under the acidic condition. The release rate was controlled by the amount of ACP, serving as a buffer to suppress acidity. When the alginate solution intramuscularly injected in the rat, a soft gel was formed in the injected site. Simvastatin released from the gel containing 0.5% of ACP showed high therapeutic effect on osteoporosis rat. Thus, the present injectable long-sustained release system is expected to be a novel drug delivery controlling device.

Aqueous N,N-diethylnicotinamide (DENA) solution as a medium for accelerated release study of paclitaxel

N,N-Diethylnicotinamide (DENA) was identified as an excellent hydrotropic agent for paclitaxel (PTX) in our previous studies. The aqueous solubility of PTX was increased by several orders of magnitude in the presence of DENA. Because of such a high hydrotropic property, DENA was used as a release medium providing a sink condition for the release of PTX from poly(lactic-co-glycolic acid) (PLGA) matrices. The release profiles of PTX from PLGA matrices into DENA, serum and phosphate-buffered saline (PBS) were compared. The stability of PTX in DENA and the degradation of PLGA molecules in DENA were examined. The degradation rate constant of PTX in 2 M DENA was similar to those in other aqueous solutions. The use of 2 M DENA as a release medium allowed differentiation of the release profiles of PTX from PLGA matrices made of different PLGA compositions. The PTX release from PLGA matrices was much faster in DENA solution than in serum or PBS, and the concentration of DENA affected the PTX release rate. The presence of DENA in the release medium increased the hydrolysis rate of PLGA polymers. The faster release of PTX from PLGA matrices in DENA solution may be due to the high PTX solubility and faster degradation of PLGA polymers in the presence of DENA. Our study suggests that the aqueous DENA solution can be used for the accelerated release study of PTX from PLGA matrices.