Biomedical subjects

Zahida Ademovic

Publications and source records attributed to Zahida Ademovic.

4 recordsLinked to original sources

PubMed2006

Colloid probe AFM investigation of interactions between fibrinogen and PEG-like plasma polymer surfaces.

Interaction forces between surfaces designed to be protein resistant and fibrinogen (Fg) were investigated in phosphate-buffered saline with colloid probe atomic force microscopy. The surfaces of the silica probes were coated with a layer of fibrinogen molecules by adsorption from the buffer. The technique of low-power, pulsed AC plasma polymerization was used to make poly(ethylene glycol) (PEG)-like coatings on poly(ethylene teraphthalate) by using diethylene glycol vinyl ether as the monomer gas. The degree of PEG-like nature of the films was controlled by use of a different effective plasma power in the chamber for each coating, ranging from 0.6 to 3.6 W. This produced a series of thin films with a different number of ether carbons, as assessed by X-ray photoelectron spectroscopy. The interaction force measurements are discussed in relation to trends observed in the reduction of fibrinogen adsorption, as determined quantitatively by (125)I radio-labeling. The plasma polymer coatings with the greatest protein-repelling properties were the most PEG-like in nature and showed the strongest repulsion in interaction force measurements with the fibrinogen-coated probe. Once forced into contact, all the surfaces showed increased adhesion with the protein layer on the probe, and the strength and extension length of adhesion was dependent on both the applied load and the plasma polymer surface chemistry. When the medium was changed from buffer to water, the adhesion after contact was eliminated and only appeared at much higher loads. This indicates that the structure of the fibrinogen molecules on the probe is changed from an extended conformation in buffer to a flat conformation in water, with the former state allowing for stronger interaction with the polymer chains on the surface. These experiments underline the utility of aqueous surface force measurements toward understanding protein-surface interactions, and developing nonfouling surfaces that confer a steric barrier against protein adsorption.

Journal Article↗

PubMed2006

Biocompatible surface preparation using amino-functionalized amylose.

Aminopropyl amyloses with various degrees of substitution (DS) were prepared and investigated with respect to their surface modification properties. Poly(acrylic acid) was grafted to plasma-activated PVDF films, and the functional amylose was bound via amide linkage formation. Layer formation was confirmed by X-ray photoelectron spectroscopy. Contact angle measurements and surface MALDI-TOF mass spectrometry indicated a hydrophilic surface and minimization of protein adsorption.

Amines↗

PubMed2005

The recognition of adsorbed and denatured proteins of different topographies by beta2 integrins and effects on leukocyte adhesion and activation.

Leukocyte beta2 integrins Mac-1 and p150,95 are promiscuous cell-surface receptors that recognise and mediate cell adhesion to a variety of adsorbed and denatured proteins. We used albumin as a model protein to study whether leukocyte adhesion and activation depended on the nm-scale topography of a protein adlayer. Albumin adsorbed from the native conformation gave rise to different adlayer topographies and different amounts of adsorbed protein on hydrophobic and relatively hydrophilic polystyrene and silanised silicon-wafer surfaces, whereas adsorption of pre-denatured Alb resulted in similar adlayer topographies and similar amounts of adsorbed protein on these surfaces. All three distinct protein-adlayer topographies supported adhesion of in vitro differentiated, macrophage-like U937 and THP-1 cells, but did not support adhesion of their promonocytic precursors. Human monocytes freshly isolated from peripheral blood did not adhere to adsorbed albumin, not even in the presence of monocyte chemoattractant protein-1 and macrophage inflammatory protein-1alpha chemokines. Adhesion of the macrophage-like cells to albumin in any of the three topographies was inhibited by antibodies against beta2 integrins, but not by antibodies against beta1 integrins, and did not induce secretion of the proinflammatory cytokine tumour necrosis factor-alpha.

Adsorption↗

PubMed2003

Surface modification of poly(vinylidenefluoride) to improve the osteoblast adhesion.

Cell adhesion to biomaterials is mediated primarily by the interaction between surface bound proteins and corresponding receptors on the membrane of the cells. The attachment of fibronectin onto poly(vinylidenefluoride) (PVDF) surface and the application of PVDF as biomaterial in bone contact was the subject of our study. PVDF is a biomaterial established for soft tissue applications. Surface modifications of PVDF were performed by plasma induced graft copolymerisation of acrylic acid or CVD polymerisation of 4-amino[2.2]paracyclophane. The provided functionalised PVDF surface was used to immobilise fibronectin using different techniques. All modification steps were verified by means of X-ray photoelectron spectroscopy (XPS), attenuated total reflection infrared spectroscopy (IR-ATR) and contact angle measurements. Surface topology was studied by atomic force measurements (AFM). Protein adsorption was controlled by enzyme linked immunosorbent assay (ELISA). Cell attachment was enhanced if physically adsorbed fibronectin was used, while enhanced attachment and proliferation were induced by covalently binding fibronectin to the surface modified PVDF.

Acetates↗