Promotion of U937 cell adhesion on polypropylene surfaces bearing phosphorylcholine functionalities

A zwitterionic serine modified chitosan derivative for improving protein stability and activity

A zwitterionic phosphoryldiserine (PDS)- chitosan conjugate was synthesized via Atherton-Todd reaction, and its degree of substitution of PDS and structure were characterized by ¹H and ³¹P NMR spectra, ICP, FTIR and XRD. Thermal analysis confirmed that there existed the freezing bound water surrounding PDS-chitosan due to the introduction of zwitterionic PDS groups onto chitosan backbone. In vitro cytotoxicity and hemolysis assay demonstrated that PDS-chitosan had excellent cell compatibility. UV adsorption and fluorescence spectra revealed that the model protein, bovine serum albumin (BSA) tended to keep its native conformation and showed better thermal stability in aqueous media in the presence of PDS-chitosan. We also found that the esterase-like activity of BSA could be enhanced by low concentration of PDS-chitosan (C_BSA = 0.33 mg/mL, C_PDS-chitosan = 0.0625 and 0.125 mg/mL, pH = 7.4, T = 25 °C). The results indicated that zwitterionic PDS-chitosan showed great potential for maintaining protein function in biomedical applications.

Cell outer membrane mimetic modification of a cross-linked chitosan surface to improve its hemocompatibility

A novel strategy has been developed to improve the hemocompatibility of chitosan surface by cell outer membrane mimetic structure able to reduce protein adsorption and cell adhesion. Phosphorylcholine dichloride was synthesized and grafted onto a glutaraldehyde-cross-linked chitosan (CS-GA) film surface to prepare phosphorylcholine-coated CS-GA film (CS-GA-PC) through a heterogeneous reaction process. The spectroscopic and contact angle characterization show that a cell outer membrane mimetic structure was formed on the cross-linked chitosan surface, and the significantly improved hemocompatibility of the modified surface was shown by a suppression of 94% on platelet adhesion, a suppression of 60-70% for bovine plasma fibrinogen and bovine serum albumin adsorptions. These results demonstrated that this cell outer membrane mimetic surface modification with phosphorylcholine dichloride is a promising strategy to improve the hemocompatibility of chitosan.

Group reorientation and migration of amphiphilic polymer bearing phosphorylcholine functionalities on surface of cellular membrane mimicking coating

Amphiphilic polymers bearing phosphorylcholine (PC) groups can form films of interfacial structure similar to that of the outer membrane of living cells. The films, as prepared, present PC groups to the external aqueous environment and exhibit good biocompatibility. However, under certain conditions, the surface structure can change irreversibly due to the reorientation and deep migration of the surface groups. X-ray photoelectron spectroscopy (XPS), dynamic contact angle measurements, and cell culture experiments were used to investigate the reorientation and migration of the surface groups of an amphiphilic PC-polymer coating. When the polymer surface is immersed into or drawn out of water, significant reorientation and group migration occurs, as suggested by the large difference between the advancing and receding contact angles. Angle-resolved XPS measurements indicate that the hydrophobic groups move to the air/film interface while the hydrophilic groups migrate towards the bulk of the polymer coating. Long periods of aging may result in irreversible changes of the surface structure and decrease the biocompatibility of the materials.

The effect of novel nitrogen-rich plasma polymer coatings on the phenotypic profile of notochordal cells

BACKGROUND

The loss of the notochordal cells from the nucleus pulposus is associated with ageing and disc degeneration. However, understanding the mechanisms responsible for the loss of these cells has been hampered in part due to the difficulty of culturing and maintaining their phenotype. Furthermore, little is known about the influence of the substratum on the molecular markers of notochordal cells.

METHODS

Notochordal cells were isolated from lumbar spine of non-chondrodystrophoid dogs and cultured on N-rich plasma polymer layers, so-called "PPE:N" (N-doped plasma-polymerised ethylene, containing up to 36% [N]) surfaces, for 3, 7 or 14 days. Gene expression of vimentin (VIM), pleiotrophin (PTN), matrix Gla protein (MGP), cartilage oligomeric matrix protein (COMP), keratin 18 (KRT 18), aggrecan (AGG), collagen type 1 (COL1A2), collagen type 2 (COL2A1) was analyzed through semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

Notochordal cells were maintained in culture on PPE:N for up to 14 days with no loss in cell viability. Except for VIM, gene expression varied depending on the culture periods and [N] concentration of the substratum. Generally, PPE:N surfaces altered gene expression significantly when cells were cultured for 3 or 7 days.

CONCLUSION

The present study has shown that notochordal cells from dogs can attach to and grow on PPE:N surfaces. Analysis of the expression of different genes in these cells cultured on different N-functionalized surfaces indicates that cellular behaviour is gene-specific and time-dependent. Further studies are required to better understand the roles of specific surface functionalities on receptor sites, and their effects on cellular phenotypes.