Investigation of Different Drug Deposition Techniques on Drug Releasing Properties of Cardiovascular Drug Coated Balloons

Plaque heterogeneity and the spatial distributions of its components dictate drug-coated balloon therapy

Drug-coated balloon (DCB) angioplasty is one of the potential approaches to alleviating in-stent restenosis and treating peripheral artery disease. An in-silico model has been developed for sirolimus drug eluted from an inflated balloon in a patient-specific arterial cross-section consisting of fibrous tissue, fibrofatty tissue, dense calcium, necrotic core, and healthy tissue. The convection-diffusion-reaction equation represents the transport of drug, while drug binding, both specific and non-specific, can be modelled as a reaction process. The Brinkman equations describe the interstitial flow in porous tissue. An image processing technique is leveraged for reconstructing the computational domain. The Marker and Cell, and Immersed Boundary Methods are used to solve the set of governing equations. The no-flux interface condition and convection do amplify the tissue content, and the regions of dense calcium and necrotic core limited to or extremely close to the interface pose a clinical threat to DCB therapy. Simulations predict the effects of the positioning and clustering of plaque components in the domain. This study demands extensive intravascular ultrasound-derived virtual histology (VH-IVUS) imaging to understand the plaque morphology and determine the relative positions of different plaque compositions about the lumen-tissue interface, which have a significant impact on arterial pharmacokinetics.

Drug-Eluting Stents and Balloons-Materials, Structure Designs, and Coating Techniques: A Review

Controlled drug delivery is a matter of interest to numerous scientists from various domains, as well as an essential issue for society as a whole. In the treatment of many diseases, it is crucial to control the dosing of a drug for a long time and thus maintain its optimal concentration in the tissue. Heart diseases are particularly important in this aspect. One such disease is an obstructive arterial disease affecting millions of people around the world. In recent years, stents and balloon catheters have reached a significant position in the treatment of this condition. Balloon catheters are also successfully used to manage tear ducts, paranasal sinuses, or salivary glands disorders. Modern technology is continually striving to improve the results of previous generations of stents and balloon catheters by refining their design, structure, and constituent materials. These advances result in the development of both successive models of drug-eluting stents (DES) and drug-eluting balloons (DEB). This paper presents milestones in the development of DES and DEB, which are a significant option in the treatment of coronary artery diseases. This report reviews the works related to achievements in construction designs and materials, as well as preparation technologies, of DES and DEB. Special attention was paid to the polymeric biodegradable materials used in the production of the above-mentioned devices. Information was also collected on the various methods of producing drug release coatings and their effectiveness in releasing the active substance.

Optimization of balloon coating process for paclitaxel coated balloons via micro-pipetting method

Drug coated balloons (DCBs) have proven to be a suitable alternative for the treatment of cardiovascular diseases. They allow for uniform delivery of an antiproliferative drug to the stenotic site without permanent implantation of the device in the patient's body. There are, however, regulatory concerns regarding the lack of data associated with variable drug delivery to the target site, which can be related to the coating process. This study describes the process for an in-house micro-pipetting coating method that incorporates a laboratory-developed coating equation for determining optimal coating parameters. The coating solutions included a common drug of choice, paclitaxel, along with a hydrophilic excipient, such as iopromide. It was found that using a revolution rate of 240 rev/min, a flow rate of 25 µL/min and a translational speed of 0.033 cm/s resulted in visually uniform coatings. High performance liquid chromatography (HPLC) allowed for the determination of paclitaxel content on the balloon surface. Scanning electron microscopy (SEM) enabled analysis of coating thickness and texture at distal, middle, and proximal positions on the balloon; average thicknesses were determined to be 16.4 ± 5.8, 14.8 ± 1.4, and 18.1 ± 3.9 µm, respectively. These optimized coating conditions have been confirmed by in vitro drug release kinetics studies. Overall this study generated a simple and reproducible micro-pipetting coating method for the sustained release of drugs from the drug coated balloons.

Coating and Pharmacokinetic Evaluation of Air Spray Coated Drug Coated Balloons

Drug coated balloons (DCB) are becoming the standard-care treatment for peripheral arterial disease (PAD). DCB use excipients to transfer and retain anti-proliferative drugs, such as paclitaxel. Excipients thus play a vital role in the design and function of DCB, however methods to coat balloons with excipients and anti-proliferative drugs remain unknown. The goal of this study was to thus develop an approach to coat and evaluate DCB for various excipients. An air sprayer method was developed to deposit paclitaxel and various excipients onto non-coated commercially available angioplasty balloons. The coating of the angioplasty balloons was evaluated for drug deposition and coating efficiency using high performance liquid chromatography tandem mass spectrometry. Drug transfer and retention of the coated angioplasty balloons into arterial segments were evaluated ex vivo using harvested pig arteries in a pulsatile flow bioreactor. The air sprayer method successfully delivered varying excipients including bovine serum albumin (BSA), urea and iohexol. The air spray method was configured to coat four angioplasty balloons simultaneously with paclitaxel and iohexol with an average paclitaxel load of 4.0 ± 0.70 µg/mm². The intra-day (within) and inter-day (between) coating precisions, defined as relative standard deviation (RSD), was 17.2 and 15.5%, respectively. Ex vivo deployment of iohexol-paclitaxel DCB yielded an arterial paclitaxel concentration of 123.4 ± 44.68 ng/mg (n = 3) at 1 h, 126.7 ± 25.27 ng/mg (n = 3) at 1 day, and 12.9 ± 12.88 ng/mg (n = 3) at 7 days. This work provides proof-of-concept of a quick, inexpensive approach to coat commercially available angioplasty balloons with paclitaxel and various excipients.

EFFECTS OF AQUEOUS MEDIUM, TWEEN-20 AND FLOW ON THE STABILITY OF SIROLIMUS

Sirolimus-eluting stents have been widely used in the treatment of coronary artery disease. Prior to the clinical application, the in vitro drug release test is a mandatory requirement for the quality control of sirolimus-eluting stents. How to maintain the stability of sirolimus in the release medium is an important issue throughout the drug release research. In this study, the stability tests of sirolimus in three aqueous media (ultrapure water (UPW), normal saline (NS) and phosphate-buffered saline (PBS, pH 7.4)) were carried out. It was found that the half-lives of sirolimus in UPW, NS and PBS (pH 7.4) were, respectively, 111.8, 43.6 and 11.5[Formula: see text]h. Tween-20 was then added to the above-mentioned three aqueous media and was shown to improve the solubility and stability of sirolimus in aqueous solutions. Under static conditions, the half-life value for sirolimus was significantly increased in the presence of Tween-20 (UPW, 3.5-fold; NS, 2.0-fold; PBS (pH 7.4), 2.7-fold). The effect of solution flow on the stability of sirolimus was also investigated in a flow loop apparatus to mimic vessel-like flow conditions. There was a significant decrease in the stability of sirolimus in aqueous media with the increase of flow rate. The results suggest that aqueous solution supplemented with Tween-20 could be used as the release medium for sirolimus-eluting stents, and that the circulation of the release medium should be controlled at low flow rate.

Application of quality by design (QbD) approach to ultrasonic atomization spray coating of drug-eluting stents

The drug coating process for coated drug-eluting stents (DES) has been identified as a key source of inter- and intra-batch variability in drug elution rates. Quality-by-design (QbD) principles were applied to gain an understanding of the ultrasonic spray coating process of DES. Statistically based design of experiments (DOE) were used to understand the relationship between ultrasonic atomization spray coating parameters and dependent variables such as coating mass ratio, roughness, drug solid state composite microstructure, and elution kinetics. Defect-free DES coatings composed of 70% 85:15 poly(DL-lactide-co-glycolide) and 30% everolimus were fabricated with a constant coating mass. The drug elution profile was characterized by a mathematical model describing biphasic release kinetics. Model coefficients were analyzed as a DOE response. Changes in ultrasonic coating processing conditions resulted in substantial changes in roughness and elution kinetics. Based on the outcome from the DOE study, a design space was defined in terms of the critical coating process parameters resulting in optimum coating roughness and drug elution. This QbD methodology can be useful to enhance the quality of coated DES.