Bioinspired multiple-interaction model revealed in adsorption of low-density lipoprotein to surface containing saccharide and alkanesulfonate

Facile Preparation of β-Cyclodextrin-Modified Polysulfone Membrane for Low-Density Lipoprotein Adsorption via Dopamine Self-Assembly and Schiff Base Reaction

A facile method for the immobilization of β-cyclodextrin on polysulfone membranes with the aim of selectively adsorbing low-density lipoprotein (LDL) was established, which is based on the self-assembly of dopamine on the membrane followed by the Schiff base reaction with mono-(6-ethanediamine-6-deoxy)-β-cyclodextrin. The surface modification processes were validated using X-ray photoelectron spectroscopy and attenuated total reflectance Fourier-transform infrared spectroscopy. Surface wettability and surface charge of the membranes were investigated through the water contact angle and zeta potential analysis. The cyclodextrin-modified polysulfone membrane (PSF-CD) showed good resistance to protein solutions, as shown by the measurement of BSA adsorption. The assessment of BSA adsorption revealed that the cyclodextrin-modified polysulfone membrane (PSF-CD) exhibited excellent resistance to protein solutions. To investigate the adsorption and desorption behaviors of the membranes in single-protein or binary-protein solutions, an enzyme-linked immunosorbent assay was employed. The results revealed that the PSF-CD possessed remarkable adsorption capacity and higher affinity for LDL in both single-protein and binary-protein solutions, rendering it a suitable material for LDL apheresis.

Fabrication and Study of Dextran/Sulfonated Polysulfone Blend Membranes for Low-Density Lipoprotein Adsorption

The abnormal increase in low-density lipoprotein (LDL) in human blood is a main independent risk factor for the pathogenesis of atherosclerosis, whereas a reduced LDL level effectively lowers morbidity. It is important to develop LDL adsorption materials with high efficiency and selectivity, as well as to simplify their fabrication processes. In this paper, polysulfone (PSF), sulfonated polysulfone (SPSF), and sulfonated polysulfone/dextran (SPSF/GLU) membranes were successfully fabricated for LDL adsorption using a solution casting technique. Attenuated total reflectance Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy measurements confirmed the success of the preparation. The water contact angle decreased from 89.7 ± 3.4° (PSF) to 76.4 ± 3.2° (SPSF) and to 71.2 ± 1.9° (SPSF/GLU), respectively. BSA adsorption testing showed that the SPSF/GLU with surface enrichment of sulfonate groups and glycosyl groups possessed higher resistance to protein solution. The adsorption and desorption behaviors of the studied samples in single-protein or binary-protein solutions were systematically investigated by enzyme-linked immunosorbent assay (ELISA), The results showed that SPSF/GLU, which had excellent resistance to protein adsorption, possessed a similar adsorption capacity to that of PSF. SPSF membrane exhibited excellent selective affinity for LDL in single and binary protein solutions, suggesting potential applications in LDL removal.

Selective Molecular Recognition of Low Density Lipoprotein Based on β-Cyclodextrin Coated Electrochemical Biosensor

The excess of low-density lipoprotein (LDL) strongly promotes the accumulation of cholesterol on the arterial wall, which can easily lead to the atherosclerotic cardiovascular diseases (ACDs). It is a challenge on how to recognize and quantify the LDL with a simple and sensitive analytical technology. Herein, β-cyclodextrins (β-CDs), acting as molecular receptors, can bind with LDL to form stable inclusion complexes via the multiple interactions, including electrostatic, van der Waals forces, hydrogen bonding and hydrophobic interactions. With the combination of gold nanoparticles (Au NPs) and β-CDs, we developed an electrochemical sensor providing an excellent molecular recognition and sensing performance towards LDL detection. The LDL dynamic adsorption behavior on the surface of the β-CD-Au electrode was explored by electrochemical impedance spectroscopy (EIS), displaying that the electron-transfer resistance (Ret) values were proportional to the LDL (positively charged apolipoprotein B-100) concentrations. The β-CD-Au modified sensor exhibited a high selectivity and sensitivity (978 kΩ·µM⁻¹) toward LDL, especially in ultra-low concentrations compared with the common interferers HDL and HSA. Due to its excellent molecular recognition performance, β-CD-Au can be used as a sensing material to monitor LDL in human blood for preventing ACDs in the future.

Advances in biomolecule inspired polymeric material decorated interfaces for biological applications

With the development of surface modification technology, interface properties have great effects on the interaction between biomedical materials and cells and biomolecules, which significantly affects the biocompatibility and functionality of materials. As an orderly and perfect system, biological organisms in nature effectively integrate all kinds of bio-interfaces with physiological functions, which shed light on the importance of biomolecules in organisms. It gives birth to a bio-inspiration strategy to design and fabricate smart materials with specific functionalities, e.g. osteogenic and chondrocytic induced materials inspired by bone sialoprotein and chondroitin sulfate. Through this mimicking approach, various functional materials were utilized to decorate the interfaces and further optimize the performance of biomedical materials, which would widely expand their applications. In this review, followed by a summary and brief introduction of surface modification methods, we highlight recent advances in the fabrication of functional polymeric materials inspired by a range of biomolecules for decorating interfaces. Then, the other applications of biomolecule inspired materials including tissue engineering, diagnosis and treatment of diseases and physiological function regulation are presented and the future outlook is discussed as well.

Improvement on the extraction efficiency of low density lipoprotein in an ionic liquid microemulsion

A novel microemulsion is developed at room temperature with 30 µL of sodium alginate sulfate (SAS, 0.02 mol/L), 0.005 g bis (2-ethylhexyl) succinate sulfonate (AOT) and 270 µL of 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF₆) ionic liquid as aqueous phase, surfactant and IL phase, respectively. The SAS/AOT/BmimPF₆ microemulsion significantly improves the extraction efficiency for low density lipoprotein (LDL). 96% LDL in a 300 µL of PBS is selectively extracted into a same volume of microemulsion, with respect to those of 67%, 76% and 85% by BmimPF₆, H₂O/AOT/BmimPF₆ microemulsion and sodium alginate (SA)/AOT/BmimPF₆ microemulsion. LDL in the SAS/AOT/BmimPF₆ microemulsion is distributed both in BmimPF₆ via hydrophobic interaction and in the "pools" of the microemulsion via electrostatic interaction with AOT and specific interaction between LDL with SAS. 83% of LDL in the microemulsion can be readily back extracted into an aqueous phase with 0.8% (m/v) of sodium dodecyl sulfate (SDS) as stripping reagent. For practical applications, LDL in human serum is selectively extracted with the microemulsion, as demonstrated by enzyme linked immunosorbent assay (ELISA) and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE).

Selective and Regenerable Surface Based on β-Cyclodextrin for Low-Density Lipoprotein Adsorption

Cyclodextrins (CDs) are a family of cyclic oligosaccharides, whose unique hydrophilic outer surface and lipophilic central cavity facilitate the formation of inclusion complexes with various biomolecules, such as cholesterol and phospholipids, via multi-interactions. Low-density lipoprotein (LDL) is the main carrier of cholesterol in bloodstream and is associated with the progression of atherosclerosis. The surface of LDL is composed of a shell of phospholipids monolayer containing most of the free unesterified cholesterol as well as the single copy of apolipoprotein B-100. To date, various LDL adsorbents have been fabricated to interact with the biomolecules on LDL surface. Owing to its elegant structure, CD is considered to be a promising choice for preparation of more economical and effective LDL-adsorbing materials. Therefore, in this study, interaction between β-CD and LDL in solution was investigated by dynamic light scattering, circular dichroism, and ultraviolet spectroscopy. Further, a supramolecular surface based on β-CD was simply prepared by self-assembled monolayer on gold surface. The effect of hydrogen bond and the cavity of β-CD on the interaction between β-CD and LDL was particularly explored by surface plasmon resonance (SPR) analysis. The SPR results showed that such β-CD-modified surface exhibited good selectivity and could be largely regenerated by sodium dodecyl sulfate wash. This study may extend the understanding of the interaction between LDL and LDL adsorbent or the design and development of more efficient and lower-cost LDL adsorbents in the future.

Effect of bilayer charge on lipoprotein lipid exchange

Lipoproteins play a key role in the onset and development of atherosclerosis, the formation of lipid plaques at blood vessel walls. The plaque formation, as well as subsequent calcification, involves not only endothelial cells but also connective tissue, and is closely related to a wide range of cardiovascular syndromes, that together constitute the number one cause of death in the Western World. High (HDL) and low (LDL) density lipoproteins are of particular interest in relation to atherosclerosis, due to their protective and harmful effects, respectively. In an effort to elucidate the molecular mechanisms underlying this, and to identify factors determining lipid deposition and exchange at lipid membranes, we here employ neutron reflection (NR) and quartz crystal microbalance with dissipation (QCM-D) to study the effect of membrane charge on lipoprotein deposition and lipid exchange. Dimyristoylphosphatidylcholine (DMPC) bilayers containing varying amounts of negatively charged dimyristoylphosphatidylserine (DMPS) were used to vary membrane charge. It was found that the amount of hydrogenous material deposited from either HDL or LDL to the bilayer depends only weakly on membrane charge density. In contrast, increasing membrane charge resulted in an increase in the amount of lipids removed from the supported lipid bilayer, an effect particularly pronounced for LDL. The latter effects are in line with previously reported observations on atherosclerotic plaque prone regions of long-term hyperlipidaemia and type 2 diabetic patients, and may also provide some molecular clues into the relation between oxidative stress and atherosclerosis.

A Green and Sustainable Route to Carbohydrate Vinyl Ethers for Accessing Bioinspired Materials with a Unique Microspherical Morphology

Synthesizing chemicals and materials from renewable sources is one of the main aims of modern science. Carbohydrates represent excellent renewable natural raw materials that are ecofriendly, inexpensive, and biologically compatible. A green procedure has been developed for the vinylation of carbohydrates by using readily available calcium carbide. Various carbohydrates were utilized as starting materials, resulting in mono-, di-, and tetravinyl ethers in high to excellent yields (81-92 %). The synthesized biobased vinyl ethers were utilized as monomers in free radical and cationic polymerizations. A unique combination of a smooth surface and intrinsic microcompartments was achieved in the synthesized materials. Two types of biobased materials were prepared involving microspheres and intrinsic hollow compartments in polymers. Scanning electron microscopy with built-in ion beam cutting was applied to reveal the spatial hierarchical structures in 3D space.

A correlation between secondary structure and rheological properties of low-density lipoproteins at air/water interfaces

The secondary structure of apolipoprotein B-100 is studied within the bulk phase and at the air/water interface. In these "in viro" experiments, infrared reflection absorption spectroscopy (IRRAS) study was performed at the air/water interface while circular dichroism (CD) was conducted in the bulk phase. In the bulk phase, the conformational structure containing a significant amount of β-structure, whereas varying amount of α-helix, unordered structures, and β-sheet were observed at the air/water interface depending on the low-density lipoprotein (LDL) film interfacial pressure. The present IRRAS results demonstrate the importance of interfacial pressure-induced structural conformations on the apoB-100. A correlation between the secondary structure of the apoB-100 protein and the monomolecular film elasticity at the air/water interface was also established. The orientation of apoB-100 with respect to the LDL film-normal was found to depend on the interfacial pressure exhibited by the monomolecular film. These results may shed light on LDL's pivotal role in the progression of atherosclerotic coronary artery disease as demonstrated previously by clinical trials.

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.

Interactions of Apolipoproteins AI, AII, B and HDL, LDL, VLDL with Polyurethane and Polyurethane-PEO Surfaces

The lipoproteins (HDL, LDL, VLDL) are important components of blood present in high concentration. Surprisingly, their role in blood-biomaterial interactions has been largely ignored. In previous work apolipoprotein AI (the main protein component of HDL) was identified as a major constituent of protein layers adsorbed from plasma to biomaterials having a wide range of surface properties, and quantitative data on the adsorption of apo AI to a biomedical grade polyurethane were reported. In the present communication quantitative data on the adsorption of apo AI, apo AII and apoB (the latter being a constituent of LDL and VLDL), as well as the lipoprotein particles themselves (HDL, LDL, VLDL), to a biomedical segmented polyurethane (PU) with and without an additive containing poly(ethylene oxide) (material referred to as PEO) are reported. Using radiolabeled apo AI, apo AII, and apoB, adsorption levels on PU from buffer at a protein concentration of 50 μg/mL were found to be 0.34, 0.40, and 0.14 μg/cm(2) (12, 23, and 0.25 nmol/cm(2)) respectively. Adsorption to the PEO surface was <0.02 μg/cm(2) for all three apolipoproteins demonstrating the strong protein resistance of this material. In contrast to the apolipoproteins, significant amounts of the lipoproteins were found to adsorb to the PEO as well as to the PU surface. X-ray photoelectron spectra, following exposure of the surfaces to the lipoproteins, showed a strong phosphorus signal, confirming that adsorption had occurred. It therefore appears that a PEO-containing surface that is resistant to apolipoproteins may be less resistant to the corresponding lipoproteins.

Glycosylation of polyphosphazenes by thiol-yne click chemistry for lectin recognition

Strong carbohydrate–lectin binding interactions in biological systems can be mimicked through the synthesis of glucose containing macromolecules, particularly glycosylated polymers.