Preparation of heparin-immobilized PVA and its adsorption for low-density lipoprotein from hyperlipemia plasma

Dual stimulus-responsive renewable nanoadsorbent for selective adsorption of low-density lipoprotein in serum

Selective removal of ultra-high low-density lipoprotein (LDL) from the blood of hyperlipemia patients using hemoperfusion is considered an efficient method to prevent the deterioration of atherosclerotic cardiovascular disease. Based on the exceptional structure-function properties of multistimulus-responsive materials, we developed a magnetic photorenewable nanoadsorbent (Fe3O4@SiO2@Azo-COOH) with outstanding selectivity and regenerative characteristics, featuring functionalized azobenzene as the ligand. The dual-stimulus response endowed Fe3O4@SiO2@Azo-COOH with rapid separation and photoregenerative properties. The adsorbent demonstrated excellent removal efficiency of LDL with an adsorption capacity of 15.06 mg/g, and highly repetitive adsorption performance (≥5 cycles) under irradiation. Fe3O4@SiO2@Azo-COOH also exhibited remarkable adsorption properties and selectivity in human serum, with adsorption capacities of 10.93, 21.26 and 9.80 mg/g for LDL, total cholesterol and triglycerides and only 0.77 mg/g for high-density lipoprotein (HDL), resulting in a 93% selective adsorption difference (LDL/HDL). Complete green regeneration of the nanoadsorbent was achieved through a simple regeneration process, maintaining a recovery rate of 99.4% after five regeneration experiments. By combining dynamic perfusion experiment with micromagnetic microfluidics, the LDL content decreased by 16.6%. Due to its superior adsorption capacity and regenerative properties, the dual stimulus-responsive nanosorbent is considered a potential hemoperfusion adsorbent.

Photorenewable Azobenzene Polymer Brush-Modified Nanoadsorbent for Selective Adsorption of LDL in Serum

The elevated concentration of low-density lipoprotein (LDL) is recognized as a leading factor of hyperlipidemia (HLP), and selective adsorption of serum LDL is regarded as a practical therapy. Based on the superior structure-function characteristics of stimuli-responsive materials, a photorenewable nanoadsorbent (SiO₂@Azo@Gly) with high selectivity and reusability was developed using azobenzene as the functional ligand. Its principle was certified by the preparation of silicon nanoparticles with atom transfer radical polymerization (ATRP)-initiating groups via a sol-gel reaction and their subsequent grafting of azobenzene polymer brushes by surface-initiated ATRP, followed by modification with glycine. Immobilization of carboxylated azobenzene polymer brushes onto the nanoparticles endowed SiO₂@Azo@Gly with high adsorption selectivity and reusability. The advanced nanoadsorbent exhibited excellent LDL adsorption capacity at about 27 mg/g and could be regenerated by illumination with high efficiency (circulations ≥ 5); this was further verified by transmission electron microscopy (TEM) and Fourier-transform infrared (FTIR) analysis. SiO₂@Azo@Gly also demonstrated superior adsorption efficiency and selectivity in serum from HLP patients, the respective adsorption capacities of LDL, triglyceride, and total cholesterol were about 15.65, 24.48, and 28.36 mg/g, and the adsorption to high-density lipoprotein (cardioprotective effect) was only about 3.66 mg/g. Green regeneration of the nanoadsorbent could be achieved completely through a simple photoregeneration process, and the recovery rate was still 97.9% after five regeneration experiments.

Biomembrane-mimetic hemoperfusion adsorbent for efficient removal of low-density lipoprotein from hyperlipemia blood

Lowering of low-density lipoprotein (LDL) levels in blood of patients with hyperlipidaemia can effectively prevent the progression of atherosclerosis and coronary heart disease. The present study demonstrated a facile synthesis strategy to prepare biomembrane-mimetic LDL adsorbent (PVA@COOH-PE) via directional immobilization of phospholipid onto macro-porous cross-linked poly(vinyl alcohol) spheres. The binding between the prepared adsorbent and LDL particles simulates the cytosolic lipid droplets to form a lipid-packing structure. The adsorbent possesses satisfactory removal efficiency for LDL and total cholesterol (TCH) in hyperlipemia serum, while remains high-density lipoprotein (HDL) concentration within the normal range. The adsorption capacities for LDL and TCH are about 1.13 and 1.74 mg/ml respectively, which are nearly three and four times higher than that of HDL (0.42 mg/ml). The adsorbent also possesses satisfactory anticoagulant properties, causes negligible effect on blood cells and produces low hemolysis ratios. The excellent blood compatibility plus LDL removal efficiency of PVA@COOH-PE indicates its good application prospect as hemoperfusion adsorbent in the treatment of hyperlipidaemia.

Targeting regulation of the tumour microenvironment induces apoptosis of breast cancer cells by an affinity hemoperfusion adsorbent

The cytokine network of tumour microenvironment (TME) plays an important role in cancer growth and progression. The current work aims to provide a new strategy for cancer therapy based on the targeted regulation of cytokines in the TME. Here, heparin-coupled polyvinyl alcohol (PVA-H) microspheres have been developed as an adsorbent for selectively remove tumour-induced immunosuppressive cytokines, such as vascular endothelial growth factor (VEGF) and transforming growth factor-beta (TGF-β), but not tumour necrosis factor-alpha (TNF-α) which has an immune-stimulating effect and can inhibit tumour growth. The proliferation and apoptosis of breast cancer cells after perfusion were tested by cell viability assays, flow cytometry analysis and mRNA microarray assays. Results showed that the PVA-H microspheres efficiently absorbed the majority of VEGF (74.39%) and TGF-β (86.39%), but much less TNF-α (4.16%). The regulation of the cytokines had remarkable anti-proliferative and pro-apoptotic effects on breast cancer cells, which was further confirmed from the change of mRNA expression levels. Thus, targeting regulatory pathways within the TME by an affinity adsorbent that selectively depletes immunosuppressive cytokines is potentially a new and promising strategy for cancer therapy.

Anionic glycosylated polysulfone membranes for the affinity adsorption of low-density lipoprotein via click reactions

An anionic glycosylated polysulfone (PSf) membrane was prepared as a high-affinity adsorbent for low-density lipoprotein (LDL). The UV-induced grafting of acrylic acid to the membrane was followed by amidation and a 'thiol-yne' click reaction to achieve glycosylation and sulfonation. Membrane modification was confirmed by attenuated total reflectance-Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. These tests revealed that the chemical compositions of the membranes' surfaces were easily regulated by controlling the 'thiol-yne' click reaction through the feed ratio of 2,3,4,6-tetra-O-acetyl-1-thio-β-d-glucopyranose and sodium 3-mercapto-1-propanesulfonate. LDL adsorption and desorption rates were estimated using an enzyme-linked-immunosorbent assay, which revealed that the obtained anionic glycosylated PSf membrane had a higher affinity for LDL than either glycosylated or sulfonated membranes alone. The combination of glycosyl and sulfonyl groups enhanced the membranes' affinities for LDL. The modified PSf membrane had an excellent biocompatibility and adsorbed a large amount of LDL, making it a promising material for LDL apheresis.

STATEMENT OF SIGNIFICANCE

Low-density lipoprotein (LDL) adsorbents normally contain negative charged ligand to induce electrostatic interaction with the positively charged regions of LDL. Furthermore, saccharide is another common component which share in most of the LDL-adsorbents and the LDL-receptor (LDLR). Such structural similarity impels us to investigate the synergistic effect of anionic and saccharide on LDL recognition. For this purpose, an anionic glycosylated membrane of which surface composition can be controlled by click reaction with mutable glycosyl/sulfonyl ratios was prepared. The obtained membrane showed better LDL adsorption/desorption property and the adsorption amount for LDL at an optimum feed ratio. This finding highlights the role of synergistic effect of anionic and saccharide, which offer a new strategy for designing LDL adsorbent with high efficiency.

Fe₃O₄@ZnO core-shell nanocomposites for efficient and repetitive removal of low density lipoprotein in plasma and on blood vessel

Low density lipoprotein (LDL)-apheresis therapy, which directly removes LDL from plasma by LDL-adsorbents in vitro is found to be clinically effective and safe to lower the LDL content in blood to prevent cardiovascular disease. Thus, developing excellent LDL adsorbents are becoming more and more attractive. Herein, functional Fe3O4@ZnO core-shell nanocomposites have been synthesized by a facile and eco-friendly two-step method. Not only do they possess high LDL adsorption (in PBS/plasma as well as on blood vessels) and favorable magnetic targeting ability but they can also be reused conveniently, which offer the Fe3O4@ZnO core-shell nanocomposites significant potential in the removal of LDL in vitro and in vivo.

Immobilization of sodium alginate sulfates on polysulfone ultrafiltration membranes for selective adsorption of low-density lipoprotein

A novel method for the immobilization of sodium alginate sulfates (SAS) on polysulfone (PSu) ultrafiltration membranes to achieve selective adsorption of low-density lipoprotein (LDL) was developed, which involved the photoinduced graft polymerization of acrylamide on the membrane and the Hofmann rearrangement reaction of grafted acrylamide followed by chemical binding of SAS with glutaraldehyde. The surface modification processes were confirmed by attenuated total reflectance Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy characterization. Zeta potential and water contact angle measurements were performed to investigate the surface charge and wettability of the membranes. An enzyme-linked immunosorbent assay was used to measure the binding of LDL on plain and modified PSu membranes. It was found that the PSu membrane immobilized with sodium alginate sulfates (PSu-SAS) greatly enhanced the selective adsorption of LDL from protein solutions and the absorbed LDL could be easily eluted with sodium chloride solution, indicating a specific and reversible binding of LDL to SAS, mainly driven by electrostatic forces. Furthermore, the PSu-SAS membrane showed good blood compatibility as examined by platelet adhesion. The results suggest that the PSu-SAS membranes are promising for application in simultaneous hemodialysis and LDL apheresis therapy.

Immobilization of heparin on polysulfone surface for selective adsorption of low-density lipoprotein (LDL)

A versatile method was developed to immobilize heparin covalently on polysulfone sheets (PSu) to achieve selective adsorption of low-density lipoprotein (LDL). This was achieved by activation of PSu with successive treatments of chlorodimethyl ether and ethylenediamine, and subsequent chemical binding of heparin with bifunctional linker molecules. A heparin density up to 0.86 microg cm(-2) on a dense PSu film was achieved. The modified PSu films were characterized by attenuated total reflectance Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The hydrophilicity of the PSu film was improved greatly by covalent immobilization of heparin. The water contact angle of PSu film was decreased from 86.6 + or - 3.7 degrees to 50.5 + or - 3.2 degrees after binding of 0.36 microg cm(-2) heparin. An enzyme-linked immunosorbent assay was used to measure the binding of LDL on plain and modified PSu films. It was found that the heparin-modified PSu film could selectively recognize LDL from binary protein solutions. Furthermore, it was possible to desorb LDL from heparinized PSu, but not from plain PSu, with heparin, sodium chloride or urea solution, which indicates a selective but reversible binding of LDL to heparin. The results suggest that heparin-modified PSu membranes are promising for application in simultaneous hemodialysis and LDL apheresis therapy.