Characterization of a Sandwich PLGA-Gallic Acid-PLGA Coating on Mg Alloy ZK60 for Bioresorbable Coronary Artery Stents

Abstract

Absorbable magnesium stents have become alternatives for treating restenosis owing to their better mechanical properties than those of bioabsorbable polymer stents. However, without modification, magnesium alloys cannot provide the proper degradation rate required to match the vascular reform speed. Gallic acid is a phenolic acid with attractive biological functions, including anti-inflammation, promotion of endothelial cell proliferation, and inhibition of smooth muscle cell growth. Thus, in the present work, a small-molecule eluting coating is designed using a sandwich-like configuration with a gallic acid layer enclosed between poly (d,l-lactide-co-glycolide) layers. This coating was deposited on ZK60 substrate, a magnesium alloy that is used to fabricate bioresorbable coronary artery stents. Electrochemical analysis showed that the corrosion rate of the specimen was ~2000 times lower than that of the bare counterpart. The released gallic acid molecules from sandwich coating inhibit oxidation by capturing free radicals, selectively promote the proliferation of endothelial cells, and inhibit smooth muscle cell growth. In a cell migration assay, sandwich coating delayed wound closure in smooth muscle cells. The sandwich coating not only improved the corrosion resistance but also promoted endothelialization, and it thus has great potential for the development of functional vascular stents that prevent late-stent restenosis.

Advances in coatings on magnesium alloys for cardiovascular stents – A review

“… ZK60 PLGA/GA/PLGA 2.1 ± 0.3 SBF −1.59 −0.24 20.51 0.01 0.468 0.0002 – The corrosion rate of the coating was ~2000 times lower than that of the bare substrate. The released GA molecules selectively promoted the proliferation of ECs, and inhibit SMCs growth [ 238 ]. AZ60 APTES/PCL – SBF −1.41 −0.365 70.5 0.293 1.610 0.0069 7 The corrosion rates of Mg alloys were extremely improved due to the preparation of the APTES/PCL coating [ 168 ].…”

“…Moreover, a multifunctional Mg-OH-PDA-HA (1 g/L) coating markedly boosted HUVECs proliferation because of the exposure of more active sites on the PDA layer; interestingly, the intrinsic anti-thrombotic function of the HA layer was also retained. For providing the degradation rate required to match the vascular reform speed, Yeh et al [ 238 ] designed a layer of sandwich-like coating with a gallic acid layer (GA, which is a type of phenolic acid with biological activity that has anti-inflammatory effects, promotes the proliferation of ECs and inhibits the growth of SMCs [ 239 , 240 ]) enclosed between the PLGA layers on the ZK60 alloy. An electrochemical analysis attested that the corrosion rate of the PLGA/GA/PLGA coating with a close-packed sandwiched layer was ~2000 times lower than that of the bare Mg substrate, demonstrating a better corrosion resistance.…”

Progress in bioactive surface coatings on biodegradable Mg alloys: A critical review towards clinical translation

“…The PA/Ca 2+ coated sample showed an increase in expression for alkaline phosphatase activity (ALP) by 60% compared to the uncoated sample, signifying osteoblast and osteogenic differentiation response of coated substrate. To enhance the corrosion resistance of OCCs, Lin et al [ 131 ] fabricated a noble coating architecture with an organic gallic acid layer sandwich between synthetic PLGA polymer layers on ZK60 Mg substrate for bioresorbable coronary artery stents. The coated sample shows a positive shift in E corr to −0.24 V SCE from −1.59 V SCE for bare substrate with a decrease in I corr nearly 10 4 times.…”

“…In recent years, organic coatings have received extensive attention for their superior corrosion resistance and multiple bio-functionalities [ 131 , 285 , 286 ]. Sol-gel is the highly reported coating technique for Mg and its alloys due to its capability to coat organic and inorganic materials on Mg alloys [ 287 ].…”

A Novel Biodegradable Composite Polymer Material Based on PLGA and Silver Oxide Nanoparticles with Unique Physicochemical Properties and Biocompatibility with Mammalian Cells

“…Nano-and micromaterials contained of poly (lactic-co-glycolic acid) (PLGA) are promising candidates for many biomedical applications, in particular, oncology therapy, targeted drug delivery, and vaccine efficacy improvement [25][26][27]. PLGA is often used to make biodegradable stent coatings, as well as parts of the stents themselves and other materials used for implantation [28][29][30][31][32][33][34][35][36].…”