Pre-Clinical Investigation of Keratose as an Excipient of Drug Coated Balloons

Human Hair Keratin-Based Hydrogels in Regenerative Medicine: Current Status and Future Directions

Regenerative medicine (RM) is a multidisciplinary field that utilizes the inherent regenerative potential of human cells to generate functionally and physiologically acceptable human cells, tissues, and organs in vivo or ex vivo. An appropriate biomaterial scaffold with desired physicochemical properties constitutes an important component of a successful RM approach. Among various forms of biomaterials explored until the present day, hydrogels have emerged as a versatile candidate for tissue engineering and regenerative medicine (TERM) applications such as scaffolds for spatial patterning and delivering therapeutic agents, or substrates to enhance cell growth, differentiation, and migration. Although hydrogels can be prepared from a variety of synthetic polymers as well as biopolymers, the latter are preferred for their inherent biocompatibility. Specifically, keratins are fibrous proteins that have been recently explored for constructing hydrogels useful for RM purposes. The present review discusses the suitability of keratin-based biomaterials in RM, with a particular focus on human hair keratin hydrogels and their use in various RM applications.

Local intraluminal delivery of a smooth muscle-targeted RNA ligand inhibits neointima growth in a porcine model of peripheral vascular disease

Anti-proliferative agents have been the primary therapeutic drug of choice to inhibit restenosis after endovascular treatment. However, recent safety and efficacy concerns for patients who underwent peripheral artery disease revascularization have demonstrated the need for alternative therapeutics. The aim of this investigation was to investigate the efficacy of a cell-specific RNA aptamer inhibiting vascular smooth muscle cell proliferation and migration. First, the impact of the RNA aptamer (Apt 14) on the wound healing of primary cultured porcine vascular smooth muscle cells (VSMCs) was examined in response to a scratch wound injury. We then evaluated the effect of local luminal delivery of Apt 14 on neointimal formation in a clinically relevant swine iliofemoral injury model. In contrast with a non-selected control aptamer (NSC) that had no impact on VSMC migration, Apt 14 attenuated the wound healing of primary cultured porcine VSMCs to platelet-derived growth factor-BB. Histological analysis of the Apt 14-treated arteries demonstrated a significant reduction in neointimal area percent diameter stenosis compared with arteries treated with saline and NSC controls. The findings of this study suggest that aptamers can function as selective inhibitors and thus provide more fine-tuning to inhibit selective pathways responsible for neointimal hyperplasia.

The Development of an ex vivo Flow System to Assess Acute Arterial Drug Retention of Cardiovascular Intravascular Devices

Purpose: The goal of this study was to develop an ex vivo system capable of rapidly evaluating arterial drug levels in living, isolated porcine carotid arteries.

Methods: A vascular bioreactor system was developed that housed a native porcine carotid artery under physiological flow conditions. The ex vivo bioreactor system was designed to quantify the acute drug transfer of catheter-based drug delivery devices into explanted carotid arteries. To evaluate our ex vivo system, a paclitaxel-coated balloon and a perfusion catheter device delivering liquid paclitaxel were utilized. At 1-h post-drug delivery, arteries were removed, and paclitaxel drug levels measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Parallel experiments were performed in a pig model to validate ex vivo measurements.

Results: LC-MS/MS analysis demonstrated arterial paclitaxel levels of the drug-coated balloon-treated arteries to be 48.49 ± 24.09 ng/mg and the perfusion catheter-treated arteries to be 25.42 ± 9.74 ng/mg at 1 h in the ex vivo system. Similar results were measured in vivo, as arterial paclitaxel concentrations were measured at 59.23 ± 41.27 ng/mg for the drug-coated balloon-treated arteries and 23.43 ± 20.23 ng/mg for the perfusion catheter-treated arteries. Overall, no significant differences were observed between paclitaxel measurements of arteries treated ex vivo vs. in vivo.

Conclusion: This system represents the first validated ex vivo pulsatile system to determine pharmacokinetics in a native blood vessel. This work provides proof-of-concept of a quick, inexpensive, preclinical tool to study acute drug tissue concentration kinetics of drug-releasing interventional vascular devices.

Understanding the Mechanism of Drug Transfer and Retention of Drug-Coated Balloons

Objective:

The purpose of this study was to determine the impact of varying inflation parameters on paclitaxel delivery and retention using a commercially available DCB.

Background:

Drug-coated balloons (DCB) have become the standard treatment for peripheral artery disease. Clinical data suggest that varying DCB delivery parameters directly impact patient outcome. Differences in delivery parameters can potentially alter the retention of the drug coating on DCBs.

Methods:

Harvested porcine carotid arteries were utilized in an ex vivo pulsatile flow bioreactor system. The DCBs were then deployed at a DCB-to-artery ratio of 1:1 or 1.25:1, an inflation time of 30 seconds or 1 minute and transit time of 30 seconds or 3 minutes. The amount of drug retention in arterial tissue was evaluated by pharmacokinetic analysis at 1 hour and 1 day post DCB deployment.

Results:

Arterial paclitaxel levels were found to be less at an inflation ratio of 1:1 with 3-minute transit time as compared to 30 seconds of transit time at 1 hour (12.3 ± 1.6 ng/mg vs. 391 ± 139 ng/mg, P = .036). At 1-day, DCBs deployed at a ratio of 1:1 resulted in less drug retention as compared to 1.25:1 (61.3 ± 23.1 ng/mg vs. 404 ± 195 ng/mg, P = .013).

Conclusion:

Arterial paclitaxel retention is reduced with extended transit times and sub-optimal expansion of the balloon. Optimization of delivery parameters can serve as an effective strategy to enhance clinical DCB outcomes.

Precision delivery of liquid therapy into the arterial wall for the treatment of peripheral arterial disease

Perfusion catheters have recently emerged as a novel approach to deliver liquid anti-proliferative agents into flow obstructed arterial segments. The purpose of this study was to determine the impact of luminal delivery pressure on liquid drug penetration into the vessel wall. An ex vivo model using harvested porcine carotid arteries and a two-dimensional computational model were utilized to determine the impact of delivery pressure of liquid therapy into the arterial wall. A pig peripheral injury model determined the impact of intra-luminal delivery pressure on drug retention. Ex vivo results demonstrated that depth of fluid penetration varies from 6.93 ± 1.90% at 0 atm to 27.75 ± 6.61% penetration of the medial layer at 0.4 atm. Computational results had similar outcomes, as penetration varied between 4.4% and 22.84%. The in vivo results demonstrated significant increase in drug delivery to the arterial tissue at 0.4 atm versus 0.1 atm at 1 h (23.43 ± 13.59 ng/mg vs. 2.49 ± 1.81 ng/mg, p = 0.026) and 7 days (0.50 ± 0.39 ng/mg vs. 0.018 ± 0.023 ng/mg, p = 0.0496). The result of this study provides an innovative strategic and technical approach to enable targeted liquid therapy.

Development of a Multi-Layer Skin Substitute Using Human Hair Keratinic Extract-Based Hybrid 3D Printing

Large-sized or deep skin wounds require skin substitutes for proper healing without scar formation. Therefore, multi-layered skin substitutes that mimic the genuine skin anatomy of multiple layers have attracted attention as suitable skin substitutes. In this study, a novel skin substitute was developed by combining the multi-layer skin tissue reconstruction method with the combination of a human-derived keratinic extract-loaded nano- and micro-fiber using electrospinning and a support structure using 3D printing. A polycaprolactone PCL/keratin electrospun scaffold showed better cell adhesion and proliferation than the keratin-free PCL scaffold, and keratinocytes and fibroblasts showed better survival, adhesion, and proliferation in the PCL/keratin electrospun nanofiber scaffold and microfiber scaffold, respectively. In a co-culture of keratinocytes and fibroblasts using a multi-layered scaffold, the two cells formed the epidermis and dermal layer on the PCL/keratin scaffold without territorial invasion. In the animal study, the PCL/keratin scaffold caused a faster regeneration of new skin without scar formation compared to the PCL scaffold. Our study showed that PCL/keratin scaffolds co-cultured with keratinocytes and fibroblasts promoted the regeneration of the epidermal and dermal layers in deep skin defects. Such finding suggests a new possibility for artificial skin production using multiple cells.

Pre-Clinical Investigation of Liquid Paclitaxel for Local Drug Delivery: A Pilot Study

The purpose of this pilot study was to investigate the feasibility of a perfusion catheter to deliver liquid paclitaxel into arterial segments. A clinically relevant rabbit ilio-femoral injury model was utilized to determine the impact of liquid paclitaxel delivered locally into the vessel wall using a perfusion catheter at 1 h to 14 days. Treatment by two clinically available forms of liquid paclitaxel, a solvent-based (sb) versus an albumin-bound (nab), along with a control (uncoated balloons), were investigated. Pharmacokinetic results demonstrated an increase in the retention of the sb-paclitaxel versus the nab-paclitaxel at 1 h; however, no other differences were observed at days one, three, and seven. Histological findings at 14 days showed significantly less neointimal area in the sb-paclitaxel treated arteries as compared with the nab-paclitaxel and the uncoated balloon-treated arteries. Additionally, percent area stenosis was significantly less in the sb-paclitaxel group. These results support the concept of local liquid delivery of paclitaxel into the arterial segments.