Silicone-covered biodegradable magnesium-stent insertion in the esophagus: a comparison with plastic stents

Biodegradable PTX-PLGA-coated magnesium stent for benign esophageal stricture: An experimental study

Biodegradable stents can degrade step by step and thereby avoid secondary removal by endoscopic procedures in contrast to metal stents. Herein, a biodegradable composite stent, a magnesium (Mg)-based braided stent with a surface coating of poly (lactic-co-glycolic acid) (PLGA) containing paclitaxel (PTX), was designed and tested. By adding this drug-loaded polymer coating, the radial force of the stent increased from 33 Newton (N) to 83 N. PTX was continuously released as the stent degraded, and the in vitro cumulative drug release in phosphate-buffered saline for 28 days was 115 ± 13.5 μg/mL at pH = 7.4 and 176 ± 12 μg/mL at pH = 4.0. There was no statistically significant difference in the viability of fibroblasts of stent extracts with different concentration gradients (P > 0.05), while the PTX-loaded stents effectively promoted fibroblast apoptosis. In the animal experiment, the stents were able to maintain esophageal patency during the 3-week follow-up and to reduce the infiltration of inflammatory cells and the amount of fibrous tissue. These results showed that the PTX-PLGA-coated Mg stent has the potential to be a safe and effective approach for benign esophageal stricture. STATEMENT OF SIGNIFICANCE: We designed a biodegradable composite stent, having poly (lactic-co-glycolic acid) (PLGA) containing paclitaxel (PTX) coated the surface of the magnesium (Mg)-based braided stent. We evaluated in vitro and in vivo characteristics of the Mg esophageal stent having a PLGA coating plus a variable concentration of PTX in comparison with the absence of PTX PLGA coating. The PTX PLGA stents exerted higher radial force than stents without coating, degraded more quickly in an acid medium, and effectively promoted fibroblast apoptosis in vitro experiments. In a rabbit model of caustic-induced esophageal stricture, there was an increased lumen and decreased inflammation of the esophageal wall in the animals stented with PTX-PLGA versus the sham group, indicating a potential approach for benign esophageal stricture.

Bioresorbable Metals for Biomedical Applications: From Mechanical Components to Electronic Devices

Bioresorbable metals and metal alloys are of growing interest for myriad uses in temporary biomedical implants. Examples range from structural elements as stents, screws, and scaffolds to electronic components as sensors, electrical stimulators, and programmable fluidics. The associated physical forms span mechanically machined bulk parts to lithographically patterned conductive traces, across a diversity of metals and alloys based on magnesium, zinc, iron, tungsten, and others. The result is a rich set of opportunities in healthcare materials science and engineering. This review article summarizes recent advances in this area, starting with an historical perspective followed by a discussion of materials options, considerations in biocompatibility, and device applications. Highlights are in system level bioresorbable electronic platforms that support functions as diagnostics and therapeutics in the context of specific, temporary clinical needs. A concluding section highlights challenges and emerging research directions.

Silver nanoparticle-coated self-expandable metallic stent suppresses tissue hyperplasia in a rat esophageal model

BACKGROUND

To evaluate the efficacy of a silver nanoparticle (AgNP)-coated self-expandable metallic stent (SEMS) for suppressing tissue hyperplasia in a rat esophageal model.

METHODS

Twenty-four male Sprague-Dawley rats were randomly assigned to four groups. Animals in group A underwent uncoated SEMS placement, whereas animals in groups B, C, and D underwent 6, 12, and 24 mg/mL AgNP-coated SEMS placement, respectively. All animals were euthanized 4 weeks after SEMS placement, and a gross examination and histological analyses were performed.

RESULTS

All rats achieved technical success and survived until the end of the study. The gross examination showed moderate to severe tissue hyperplasia in 5 rats in group A and 2 rats in group B. In contrast, no animals in groups C and D had moderate or severe tissue hyperplasia. The gross examination revealed no complications. The percentage of granulation tissue area, number of epithelial layers, thickness of submucosal fibrosis, percentage of connective tissue area, inflammatory cell infiltration grade, degree of collagen deposition, and degrees of Ki67, TUNEL, and α-SMA-positive deposition were significantly lower in groups C and D than in group A (all p < 0.05). However, only the percentage of granulation tissue area, number of epithelial layers, thickness of submucosal fibrosis, and percentage of connective tissue area were significantly lower in group B than in group A (all p < 0.05). No histological parameters were significantly different between group D and group C (all p > 0.05).

CONCLUSION

AgNP-coated SEMSs suppressed tissue hyperplasia in a rat esophageal model.

Silicone-covered biodegradable magnesium stent for treating benign esophageal stricture in a rabbit model

BACKGROUND

Stent insertion can effective alleviate the symptoms of benign esophageal strictures (BES). Magnesium alloy stents are a good candidate because of biological safety, but show a poor corrosion resistance and a quick loss of mechanical support in vivo.

AIM

To test the therapeutic and adverse effects of a silicone-covered magnesium alloy biodegradable esophageal stent.

METHODS

Fifteen rabbits underwent silicone-covered biodegradable magnesium stent insertion into the benign esophageal stricture under fluoroscopic guidance (stent group). The wall reconstruction and tissue reaction of stenotic esophagus in the stent group were compared with those of six esophageal stricture models (control group). Esophagography was performed at 1, 2, and 3 weeks. Four, six, and five rabbits in the stent group and two rabbits in the control groups were euthanized, respectively, at each time point for histological examination.

RESULTS

All stent insertions were well tolerated. The esophageal diameters at immediately, 1, 2 and 3 wk were 9.8 ± 0.3 mm, 9.7 ± 0.7 mm, 9.4 ± 0.8 mm, and 9.2 ± 0.5 mm, respectively (vs 4.9 ± 0.3 mm before stent insertion; P < 0.05). Magnesium stents migrated in eight rabbits [one at 1 wk (1/15), three at 2 wk (3/11), and four at 3 wk (4/5)]. Esophageal wall remodeling (thinner epithelial and smooth muscle layers) was found significantly thinner in the stent group than in the control group (P < 0.05). Esophageal injury and collagen deposition following stent insertion were similar and did not differ compared to rabbits with esophageal stricture and normal rabbits (P > 0.05).

CONCLUSION

Esophageal silicone-covered biodegradable magnesium stent insertion is feasible for BES without causing severe injury or tissue reaction. Our study suggests that insertion of silicone-covered magnesium esophageal stent is a promising approach for treating BES.

Biodegradable Stents in Resistant Peptic Oesophageal Stricture: Is It the Right Way to Go?

Peptic oesophageal stricture can be considered as the end result of prolonged gastro-oesophageal reflux. The 'gold standard' treatment for peptic stricture is endoscopic dilatation with balloon or bougie. It is predicted that up to 40% of patients remain symptomatic with dysphagia due to refractory (resistant to treatment) or recurrent strictures, needing frequent interventions at short intervals. Such patients have poor nutritional status due to the primary disease and are susceptible to complications related to repeated endoscopic dilatation such as bleeding and perforation. This general review aims to analyse existing published evidence and address the role of biodegradable stents in resistant peptic strictures as an alternative treatment to provide long-term dysphagia-free intervals.

The current trends of Mg alloys in biomedical applications-A review

Magnesium (Mg) has emerged as an ideal alternative to the permanent implant materials owing to its enhanced properties such as biodegradation, better mechanical strengths than polymeric biodegradable materials and biocompatibility. It has been under investigation as an implant material both in cardiovascular and orthopedic applications. The use of Mg as an implant material reduces the risk of long-term incompatible interaction of implant with tissues and eliminates the second surgical procedure to remove the implant, thus minimizes the complications. The hurdle in the extensive use of Mg implants is its fast degradation rate, which consequently reduces the mechanical strength to support the implant site. Alloy development, surface treatment, and design modification of implants are the routes that can lead to the improved corrosion resistance of Mg implants and extensive research is going on in all three directions. In this review, the recent trends in the alloying and surface treatment of Mg have been discussed in detail. Additionally, the recent progress in the use of computational models to analyze Mg bioimplants has been given special consideration. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1970-1996, 2019.

Updates on the research and development of absorbable metals for biomedical applications

Absorbable metals, metals that corrode in physiological environment, constitute a new class of biomaterials intended for temporary medical implant applications. The introduction of these metals has shifted the established paradigm of metal implants from preventing corrosion to its direct application. Interest toward absorbable metals has been growing in the past decade. This is proved by the rapid increase in scientific publication, progressive development of standards, and launching the first commercial products. Iron, magnesium, zinc, and their alloys are the current three absorbable metals families. Magnesium-based metals are the most progressing family with a large data set obtained from both basic and translational research. Iron-based metals are still facing a major challenge of low in vivo corrosion rate despite the significant efforts that have been put to overcome its weakness. Zinc-based metals are the new alternative absorbable metals with moderate corrosion rates that fall between those of iron and magnesium. This manuscript provides a brief review on the latest progress in the research and development of absorbable metals, the most important findings, the remaining challenges, and the perspective on the future direction.