Comparative Study of Osteogenic Activity of Multilayers Made of Synthetic and Biogenic Polyelectrolytes.

Polyelectrolyte multilayer (PEM) coatings on biomaterials are applied to tailor adhesion, growth, and function of cells on biomedical implants. Here, biogenic and synthetic polyelectrolytes (PEL) are used for layer-by-layer assembly to study the osteogenic activity of PEM with human osteosarcoma MG-63 cells in a comparative manner. Formation of PEM is achieved with biogenic PEL fibrinogen (FBG) and poly-l-lysine (PLL) as well as biotinylated chondroitin sulfate (BCS) and avidin (AVI), while poly(allylamine hydrochloride) (PAH) and polystyrene sulfonate (PSS) represent a fully synthetic PEM used as a reference system here. Surface plasmon resonance measurements show highest layer mass for FBG/PLL and similar for PSS/PAH and BCS/AVI systems, while water contact angle and zeta potential measurements indicate larger differences for PSS/PAH and FBG/PLL but not for BCS/AVI multilayers. All PEM systems support cell adhesion and growth and promote osteogenic differentiation as well. However, FBG/PLL layers are superior regarding MG-63 cell adhesion during short-term culture, while the BCS/AVI system increases alkaline phosphatase activity in long-term culture. Particularly, a multilayer system based on affinity interaction like BCS/AVI may be useful for controlled presentation of biotinylated growth factors to promote growth and differentiation of cells for biomedical applications.

Nanostructured material surfaces--preparation, effect on cellular behavior, and potential biomedical applications: a review.

Nanostructures play important roles in vivo, where nanoscaled features of extracellular matrix (ECM) components influence cell behavior and resultant tissue formation. This review summarizes some of the recent developments in fostering new concepts and approaches to nanofabrication, such as top-down and bottom-up and combinations of the two. As in vitro investigations demonstrate that man-made nanotopography can be used to control cell reactions to a material surface, its potential application in implant design and tissue engineering becomes increasingly evident. Therefore, we present recent progress in directing cell fate in the field of cell mechanics, which has grown rapidly over the last few years, and in various tissue-engineering applications. The main focus is on the initial responses of cells to nanostructured surfaces and subsequent influences on cellular functions. Specific examples are also given to illustrate the potential nanostructures may have for biomedical applications and regenerative medicine.

Blood compatibility and permeability of heparin-modified polysulfone as potential membrane for simultaneous hemodialysis and LDL removal.

Heparin was covalently immobilized on PSf membranes to obtain a dialysis membrane with high affinity for LDL. WCA and streaming potential measurements were performed to investigate wettability and surface charge of the membranes. The morphology of the membranes was investigated by SEM. An ELISA was used to measure the adsorption and desorption of LDL on plain and modified PSf. Blood compatibility was studied by measurement of thrombin time, partial thromboplastin time, kallikrein activity and platelet adhesion. It was found that the blood compatibility of the membrane was improved by covalent immobilization of heparin at its surface. However, PSf-Hep membrane showed higher flux recovery after BSA solution filtration, which revealed antifouling property of PSf-Hep membranes.

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.