Biomedical subjects

H Mirzadeh

Publications and source records attributed to H Mirzadeh.

12 recordsLinked to original sources

PubMed2006

Effect of surface charge and hydrophobicity of polyurethanes and silicone rubbers on L929 cells response.

Wettability and zeta potential studies were performed to characterize the hydrophobicity and surface charge of virgin and oxygen plasma irradiated silicone rubbers and polyurethane (polyether and polyesther) samples and evaluate the effect of hydrophobicity and surface charge on fibroblast cells attachment and growth. The surface properties of polyurethanes and silicones and plasma irradiated surfaces were compared by water drop contact angle and zeta potential measurement. Using SEM photomicrographs to study the morphology of virgin and plasma irradiated samples surfaces and light microscopy for study the behavior of cell attachment on these surfaces. Water drop contact angle measurements show that in despite of the silicones, the polyurethanes become more hydrophobic and have stable surface than silicones. Results show that wettability of plasma treated silicones increase and after 48 h recovery take place. Zeta potential measurements noticed that plasma treated polyetherurethane surface is more negatively charge, and consequently attachment of the L929 fibroblast cells decreased whereas on silicones surfaces, negatively charge surfaces show increase cells attachment.

Animals↗

PubMed2006

Hydrophilic interpenetrating polymer networks of poly(dimethyl siloxane) (PDMS) as biomaterial for cochlear implants.

Poly(dimethyl siloxane) (PDMS) was bulk-modified to develop a new intra-cochlear electrode that can closely hug the inner wall of scala tympani (ST). The hydrophilicity of bulk and surface of PDMS was changed using a sequential method for preparation of interpenetrating polymer networks (IPNs). A series of IPNs, based on PDMS and poly(acrylic acid) (PAAc), was synthesized and characterized by means of attenuated total reflectance Fourier transform infrared spectroscopy, water contact-angle measurement, dynamic mechanical thermal analysis and peel strength tests. The performances of actual-sized fabricated electrodes were assessed inside a transparent model of ST, which was filled with saline. The cell behavior of L929 fibroblasts on materials was studied in vitro.

Acrylic Resins↗

PubMed2005

Ultra high molecular weight polyethylene and polydimethylsiloxane blend as acetabular cup material.

An acetabular cup shock absorber implant is formed from a composite of polymer materials. The cup consists of three zones such as the articulating surface of the implant is 100% ultra high molecular weight polyethylene (UHMWPE) (zone 1) and shock absorber of the cup contains of polydimethylsiloxane (PDMS) (zone 3). Zone 2 which is designed for better adhesion between zone 1 and zone 2 consists of a blend of UHMWPE and PDMS is a cushion that from one side adheres to zone 1 and the other side to zone 2. PDMS and UHMWPE have been blended under conditions of shear and elevated temperature in order to form uniform, thermoplastic blends. When blends compared to pure UHMWPE, the blends show lowered tensile modulus and lowered mixing energies. The UHMWPE crystals are increased in quantity or else become more regular, even 50% blend shows no rubbery stage. The morphology and dynamic mechanical behavior of the blends were studied using scanning electron microscopy (SEM) and dynamic mechanic thermal analysis (DMTA). In this study, the biocompatibility have evaluated in vitro the interaction of UHMWPE, silicone and PDMS/UHMWPE blends with L929 fibroblast cells.

Absorbable Implants↗

PubMed2004

BHK cells behaviour on laser treated polydimethylsiloxane surface.

The surface of polydimethylsiloxane (PDMS) was modified using a CO2-pulsed laser to evaluate the changes in physical and biological properties of the treated surface. Attachment of anchorage dependent cells, namely baby hamster kidney (BHK) fibroblastic cells, on PDMS surface was investigated in stationary culture conditions. BHK cell adhesion and growth on the PDMS surfaces were studied using scanning electron microscopy (SEM) and optical microscopy. To evaluate the surface wettability, water drop contact angles were determined. The laser treated PDMS surfaces showed high hydrophobicity and low cell adhesion, no spreading and growth in comparison with the unmodified PDMS. It was found that both the wettability and surface structure of the PDMS surface control cell attachment and growth.

Animals↗

PubMed2004

Segmented detachable structure of cochlear-implant electrodes for close-hugging engagement with the modiolus.

Surface and bulk modification techniques of polydimethylsiloxane (PDMS) polymers were used to develop a new intracochlear electrode that can closely hug the inner wall of scala tympani. Laser-induced surface grafting of poly (2-hydroxyethyl methacrylate) (PHEMA) and sequential method for preparation of interpenetrating polymer networks (IPNs) of PDMS/PHEMA were, respectively, used for surface and bulk modifications. The hydrogel content and water-uptake capability of the modified samples were optimized by Taguchi method for experimental design. The modified PDMS samples were examined by performing attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, water contact-angle measurement, and peel strength tests. The performances of actual-sized fabricated electrodes were assessed inside a transparent model of scala tympani, which was filled with saline. After a swelling process, the hydrophilic branch begins to elongate and detach from hydrophobic branch and pushes it toward the inner wall.

Cochlea↗

PubMed2004

Laser surface modification of silicone rubber to reduce platelet adhesion in vitro.

To improve the blood compatibility, the surface of polydimethylsiloxane (PDMS) films were irradiated using a CO2-pulsed laser. Acrylamide (AAm) was grafted onto a pre-irradiated surface. The AAm-grafted and laser-treated films were characterized using different techniques. Platelet adhesion and activation onto the AAm-grafted PDMS, laser-treated (ungrafted) and unmodified PDMS film surfaces were compared. Data from in vitro assays indicated that the platelet adhesion was reduced on the AAm-grafted PDMS and laser treated PDMS films in comparison with the unmodified PDMS. The laser-irradiated sample showed the minimum platelet adhesion. It seems that laser irradiation onto a silicone rubber surface is a versatile technique to produce anti-thrombogenic surface for biomaterial applications.

Acrylamide↗

PubMed2004

In vitro and in vivo hemocompatibility evaluation of graphite coated polyester vascular grafts.

Attempts have been made in this study to prepare a homogeneous and stable coating of graphite on polyester vascular grafts (GPVG) using an electrophoresis method to evaluate thromboresistant and blood compatibility of GPVG in comparison to non-coated PVG and InterGard (collagen sealed PVG) as control. Lactate dehydrogenase (LDH) activity measurement was carried out on all PVG types to evaluate platelet adhesion. To examine tissue reaction GPVG and non-coated sheets of knitted polyester fabric were implanted simultaneously in the dorsal flank of rats subcutaneously. The GPVG, non-coated and control were implanted in descending aorta as end-to-end or end-to-side implantation substitution in 25 sheep for 4-60 weeks. Results showed that the graphite coating on polyester vascular grafts reduced the number of adherent platelets and prevent platelet activation and spreading on the surface in comparison with non-coated and control. Pathological investigation showed inflammatory reactions were totally resolved after 12 weeks and there was no difference in the tissue reaction between graphite coated, non-coated and control patches. All grafts remained patent and there was no significant difference in patency rate between these three types of PVG. We found that GPVG has no need for pre-clotting and it showed lower platelet aggregation, thinner capsule formation and lower calcification after 15 months. However, suturing of GPVG was more difficult in comparison with the other types.

Animals↗

PubMed2001

In vitro studies of platelet adhesion on laser-treated polyethylene terephthalate surface.

In order to improve blood compatibility, the surfaces of polyethylene terephthalate (PET) were treated using CO2 pulsed and KrF excimer lasers. The physico-chemical characterization of the laser-treated PET surfaces was carried out through attenuated total reflectance infrared spectroscopy and contact-angle measurements. The hemocompatibility of the laser-irradiated PET films was examined in vitro to evaluate their capability of inducing platelet adhesion in comparison with unmodified PET. The number of adhered platelets was determined by lactate dehydrogenase (LDH) activity measurement. Platelet adhesion on the untreated PET was relatively high compared to the laser-treated samples. Laser irradiation of PET surface reduced the number of adherent platelets and prevented platelet spreading on the surface. Reduction of platelet adhesion was attributed to the change in morphology, chemical structure, and crystallinity of the PET surface due to laser irradiation with various numbers of pulses. The morphology of adhered platelets on the PET surfaces was investigated by scanning electron microscopy (SEM). The SEM observations were consistent with the results obtained from LDH activity measurement.

Biocompatible Materials↗

PubMed2001

Cell behavior on laser surface-modified polyethylene terephthalate in vitro.

This work has been undertaken to study the cell behavior of L929 fibroblasts on the laser irradiated polyethylene terephthalate (PET) surface. To modify the surface properties of the PET, CO2 pulsed laser at the wavelength of 9.25 microm and KrF excimer laser at 248 nm with various number of pulses were used. Laser irradiation caused some changes in the chemical and physical properties of the laser-treated film surfaces, which were evaluated using different techniques. These changes may affect the cell adhesion and growth on the laser-treated PET. Therefore, cell attachment and spreading were investigated on the laser-treated PET in vitro. The data from in vitro assays showed the fibroblast cells were attached and proliferated extensively on the CO2 and KrF laser-treated films in comparison with the unmodified PET. The results obtained from the cell behavior studies revealed that surface morphology and wettability affected cell adhesion and spreading on the laser-treated PET.

Animals↗

PubMed2001

Isocyanate-terminated urethane prepolymer as bioadhesive material: evaluation of bioadhesion and biocompatibility, in vitro and in vivo assays.

Attempts have been made to evaluate the degree of bioadhesion and biocompatibility of a synthesized urethane prepolymer with specially tailored microstructure. Wetting behaviour and extent of interfacial adhesion of the prepared prepolymer towards biological substrates were examined by in vitro methods. The former was carried out by measuring the contact angle between drops of the prepolymer liquid and a biological surface, while the latter was determined from the force between the prepolymer and tissue model or mucus. The obtained results exhibited good tissue wettability and bioadhesion by the prepolymer. Preliminary evaluation of biocompatibility for the uncatalytically cured prepolymer films was performed by cytotoxicity and histotoxicity experiments. Results showed a significant growth for the adhered L929 fibroblast cells within a period of 5 days incubation. Also, no severe inflammatory tissue response towards the samples implanted in rabbit for 16 weeks was seen. These observations can support the potentiality of the designed urethane prepolymer to be applied as hemostatic agent.

Adhesiveness↗

PubMed1995

Cell attachment to laser-induced AAm- and HEMA-grafted ethylene-propylene rubber as biomaterial: in vivo study.

With the purpose of improved tissue compatibility, ethylene-propylene rubber (EPR)-based vulcanizates have been surface grafted with acrylamide (AAm) and 2-hydroxyethyl methacrylate (HEMA) using CO2-pulsed laser as excitation source. Grafted surfaces were characterized by performing scanning electron microscopy combined with energy dispersive X-ray analysis and attenuated total reflectance infrared spectroscopy to study the surface morphology and grafting. Surface hydrophilicity (measured by water drop contact angle) increased for the grafted samples. Fractal type of morphology is formed by the grafted poly(AAm) and poly(HEMA) chains on the surface of EPR, which provides both hydrophilic and hydrophobic sites. In vivo tissue compatibility was assessed by implanting test samples in the deep intramuscular and peritoneal layers of rabbits. After 8 weeks of implantation, comparative results indicate that the adhesion of macrophages to EPR samples modified with AAm and HEMA, with no respiratory burst and cellular damage, is significantly lower than their adhesion on unmodified surfaces which show an activated state of the attached macrophages. Also, no acute or chronic inflammatory reaction was observed at the site of implantation and a thinner fibrous tissue capsule formed around the modified samples, whereas foreign body giant cells adhered to unmodified EPR.

Acrylamide↗

PubMed1994

Biocompatibility evaluation of laser-induced AAm and HEMA grafted EPR. Part 1: In-vitro study.

Samples based on ethylene-propylene rubber (EPR) have been surface grafted with acrylamide (AAm) and 2-hydroxyethyl methacrylate (HEMA) using CO2-pulsed laser as a stimulation source. Scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDXA) and attenuated total reflectance infrared (ATR-IR) spectra were performed on the modified samples. These techniques revealed the formation of grafted poly(AAm) and poly(HEMA) on the surface of EPR. The surface grafted poly(AAm) and poly(HEMA) were found to have a fractal type of morphology. EDXA showed insignificant grafted AAm and HEMA in regions where fractals were absent. Fractal patterned surfaces provide hydrophilic and hydrophobic sites, making EPR suitable as a biomaterial. In-vitro adhesion and spreading of alveolar macrophages (AMs) cultured on the surface of modified samples have been evaluated by hemocytometry and SEM, respectively, and compared with unmodified controls. Relationships between AM adhesion and their spreading, with surface morphology, graft level and water compatibility are also discussed. Generally, more AMs attach onto unmodified surfaces with a greater degree of spreading, than on the modified EPR. Samples grafted between 0.7 mg/cm2 and 1 mg/cm2 showed fairly low AM density compared with both unmodified EPR and lightly modified samples (less than 0.2 mg/cm2). AMs cultured on the unmodified EPR were larger and displayed pronounced ruffling of the plasma membrane, an increased capacity for adherence and spreading on the surface, and an increased number of extensive filopodia. Moreover, AMs attached onto the surface of modified samples appeared rounded, with minimal cytoplasmic spreading and ruffling.

Absorptiometry, Photon↗