Lailong Luo

Layer-by-layer assembly of chitosan and platelet monoclonal antibody to improve biocompatibility and release character of PLLA coated stent.

The aim of this study is to construct a biocompatible coating of a drug-eluting stent through the incorporation of chitosan with monoclonal antibody (mAb) to a platelet glycoprotein (GP) IIIa receptor, by electrostatic layer-by-layer (LBL) adsorption of oppositely charged polyelectrolytes and proteins. The platelet maximum aggregation rate and aggregation inhibition rate tests confirm the bioactivity of mAb in different pH assembly environments. The fluorescence spectra test and confocal laser scanning microscopy observation were used to monitor the LBL assembly process of the mAb/chitosan multilayer on the surface of the aminolyzed Poly-L-lactic acid (PLLA) membrane, when using Rhodamine B isothiocyanate-labeled mAb and Fluorescein isothiocyanate-labeled chitosan. The in vitro platelet adhesion experiment demonstrated the amicable blood compatibility of the mAb/chitosan multilayer. The endothelial cell adhesion and migration test revealed that the multilayer could improve the cytocompatibility of the PLLA matrix in terms of cell attachment, proliferation, and migration. An in vitro perfusion circuit was designed to evaluate the release rates measured by a radioisotope technique with ¹²⁵I-labeled GP IIIa mAb. The different eluting curves of the mAb/chitosan-assembled stent and mAb physically absorbed stent showed the improvement of mAbs release character when using LBL self-assembly technology. Our method to prepare a biocompatible stent surface with mAb/chitosan multilayers has proved to be favorable and effective in vitro, thus justifying further evaluation to improve the biocompatibility in an animal model test.

Heparinized poly(vinyl alcohol)--small intestinal submucosa composite membrane for coronary covered stents.

To develop a novel coating material for coronary covered stents, we prepared a kind of composite membrane which contains polyvinyl alcohol (PVA) and porcine small intestinal submucosa (SIS) powders crosslinked and heparinized by N-(3-dimethylaminopropyl)-N-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). The amount of immobilized heparin increased with increasing ratios of EDC:heparin, and the maximum amount was approximately 60 microg heparin per milligram SIS powder at a weight ratio of EDC:heparin of 2. Uniaxial tensile and balloon inflation testing suggested that the composite membrane crosslinked by lower EDC concentration is more flexible and elastic. The clotting time (APTT and PT) of the heparinized PVA-SIS membrane was longer than that of the unheparinized membrane. The number of adherent platelets on the heparinized PVA-SIS composite membrane was about 25% of the unheparininzed, and there was no sign of accumulation and almost no pseudopodium was observed. The endothelial cells were amicable with the heparinized and unheparinized PVA-SIS composite membranes. In in vivo implantation tests, we observed a thin capsule formed by several layers of fibroblasts surrounding the implants. These results showed that the heparinized PVA-SIS composite membrane has potential biomechanical and biological properties as a coating material for coronary covered stent.

Ultrasonic atomization and subsequent desolvation for monoclonal antibody (mAb) to the glycoprotein (GP) IIIa receptor into drug eluting stent

An eluting-stent system with mAb dispersed in the PLLA (poly (L-lactic acid)) was validated in vitro. Specifically designed spray equipment based on the principle of ultrasonic atomization was used to produce a thin continuous PLLA (poly (L-lactic acid)) polymer coating incorporating monoclonal antibody (mAb). This PLLA coating was observed in light microscopy (LM) and scanning electron microscopy (SEM). The concentration of the monoclonal antibody (mAb) to the platelet glycoprotein (GP) IIIa receptor and the eluting rate were then measured by a radioisotope technique with (125)I-labelled GP IIIa mAb. An in vitro perfusion circuit was designed to evaluate the release rates at different velocities (10 or 20 ml min(-1)). The PLLA coating was thin and transparent, uniformly distributed on the surface of the stent. Three factors influenced its thickness: PLLA concentration, duration and gas pressure. The concentration of mAb was influenced by the duration of absorption and the concentration of the mAb solution; the maximum was 1662.23 + or - 38.83 ng. The eluting rate was fast for the first 2 h, then decreased slowly and attained 80% after 2 weeks. This ultrasonic atomization spray equipment and technological process to prepare protein eluting-stents were proved to be effective and reliable.

Endothelialization and in‐stent restenosis on the surface of glycoprotein IIIa monoclonal antibody eluting stent

Since the percutaneous transtuminal coronary angioplasty was introduced into China in 1984, this procedure has become widely accepted as an important step in coronary revascularization. This study shows the effect of the monoclonal antibody (mAb) on the platelet glycoprotein IIIa receptor during endothelialization and in-stent restenosis by implanting the mAb-eluting stents into iliac arteries of rabbits. The hard tissue cross sections of the stent-implanted arterial segments were made by polymethylmethacrylate embedding. Arterial intima proliferation was observed and analyzed. The endothelialization of the stent surface was observed using scanning electron microscope, whereas the ultrastructure of the neointima was observed using transmission electron microscope. After one month of stent implantation, the surfaces of both groups were covered by intact endothelial layers, but the neointimal areas and the ratio of stenosis were significantly lesser in the mAb-eluting stent group (p < 0.01). After 3 months, the ratio of stenosis in the mAb-eluting stent group was 14.67 ± 0.79, whereas that of the bare stent group was 21.58 ± 1.76 (p < 0.01). Therefore, the mAb eluting from the stent surface has the potential to accelerate endothelialization, prevent thrombosis formation due to the interaction of stent with blood, and decrease the stenosis ratio by inhibiting neointima proliferation.

A Novel Micro-spraying System for Preparing Polymer-coated Intravascular Stent

In order to prepare the polymer coating effectively and simply on the stent, which avails producing the drug eluting stent (DES), a novel micro-spraying system was introduced in this paper. Based on the theory of ultrasonic atomization, the spray system was designed and established which was composed of four primary modules. The optimized spray parameters were also determined through orthogonal experiment for preparing coating by the system. The fluorescence stain and image analysis were used to make the morphologies of coating more apparent. Our experimental results reveal that the spray system designed in this paper is suitable for preparing polymer coating, which will facilitate the development of DES.

Eluting characteristics of a platelet glycoprotein receptor antibody using a PLLA-coated stent

Drug-eluting stents (DES) have emerged as a recognized alternative to treat stent restenosis but many questions remain regarding the optimal type and eluting characteristics of both drug and stent. The first component of the study examines the extent of surface coating of PLLA (poly(L-lactic acid)) on a Nitinol stent. The second characterizes the adsorption and elution rates of monoclonal mouse anti-human platelet glycoprotein (GP) IIIa antibody SZ-21 from a PLLA-coated surface. The PLLA coating was examined by fluorescence staining and image analysis using the Image Processing Box of MATLAB. Stents exposed to the monoclonal mouse anti-human platelet GP IIIa antibody were tested for their adsorption characteristics by radioisotope technique with 125I-labelled SZ-21. The elution rates were then measured in looped circuits at different velocities (10 or 20 ml/min) and durations (30 min up to 312 h). Results showed that the fluorescence staining and image analysis showed a striking difference in the extent of coating between PLLA-coated stents and SZ-21 eluting stents on the gray-scale distribution of Nitinol surfaces. The amount of SZ-21 adsorbed onto the PLLA-coated stents was dependent on the concentration and duration of immersion in the solution. The method of preparation the mAb eluting stent significantly influenced the elution characteristics for a continuous perfusion of more than 300 h. The eluting curve was biphasic with initial rapid elution for the first 24 h followed by a gradual slow elution. These results indicate that the Image Processing Box of MATLAB appears to be a useful method for semi-quantitative analysis of fluorescence images. Furthermore, SZ-21 can be passively adsorbed onto PLLA-coated stents and predictably influenced by the concentration and duration of immersion. These studies may pave the way to developing stent-based delivery of a potent anti-platelet agent.