Evaluation of biological responses to polymeric biomaterials by RT-PCR analysis. I. Study of IL-1 beta mRNA expression

In this study, we introduce a novel research methodology, the evaluation of mRNA expression of cells contacting with polymeric materials using reverse transcription-polymerase chain reaction (RT-PCR) analysis HL-60 was used as a model of the macrophages. The expression of interleukin-1 beta (IL-1 beta) mRNA, a cytokine secreted by macrophages, was selected to estimate the extent of inflammation. The expression of IL-1 beta mRNA in the HL60 cells cultured on various substrates and in various conditions was studied. Expression of IL-1 beta could be successfully determined by RT-PCR analysis. A 48 h incubation period was necessary to clarify the expression of IL-1 beta mRNA. It became clear that lipopolysaccharide stimulation was not necessary in this analysis because of the high sensitivity of RT-PCR analysis. It is concluded that RT-PCR analysis is a powerful tool for studying cell-polymer interaction, and is a complementary method for ELISA.

Synthesis and anticoagulant activity of sulfated glucoside-bearing polymer

Poly(glucosyloxyethyl methacrylate) sulfate [poly(GEMA) sulfate], which contains sulfated glucoside residues, was prepared by the reaction with N,N-dimethylformamide (DMF)/sulfur trioxide (SO3) complex. The degree of sulfation was easily controlled by changing the amount of DMF/SO3 complex added and reaction time. The total human blood clotting time in the presence of poly(GEMA) sulfate was prolonged by increasing the dose or the degree of sulfation of the polymer. The anticoagulant activity of poly(GEMA) sulfate was also compared with that of dextran sulfate, poly(styrenesulfonic acid), poly(vinylsulfuric acid), and heparin. The result suggests that sulfated saccharide residues are essential for endowing anticoagulant activity to synthetic polymer.

Novel functional polymers: poly(dimethylsiloxane)-polyamide multiblock copolymer. V. The interaction between biomolecules and the surface of aramid-silicone resins

Multiblock copolymers consisting of aromatic polyamide(aramid) and poly(dimethylsiloxane) (PDMS) aramid-silicone resins (PASs) were synthesized by low temperature solution polycondensation, and PAS films were prepared by casting from an N,N'-dimethylacetamide solution. In this study, we investigated bovine serum albumin (BSA) adsorption, L929 cell adhesion, and tissue reaction on the surface of PAS in order to clarify the interaction between PAS and biomolecules. It was found that the amount of adsorbed biomolecules on PAS was extremely low in contrast with those on aramid and nylon films, and it was comparable to SILASTIC 500-1 film. This suppression of adsorption of biomolecules onto PAS seemed to be due to the low surface free energy of the outermost surface of PAS, where PDMS block was condensed.

Successful management of infantile hepatic hilar hemangioendothelioma with obstructive jaundice and consumption coagulopathy

A 4-month-old boy with benign hemangioma of the porta hepatis is described. Obstructive jaundice and consumption coagulopathy developed, which were treated by percutaneous transhepatic drainage (PTHD), without resection of the tumor or bypass surgery. Because of tumor regression, the patient has remained free of symptoms even after the PTHD tube was removed. Because juvenile hemangioma is a benign tumor and occasional spontaneous regression is known to occur (as in our case and other reports), it is suggested that complete resection or bypass surgery is not necessary for juvenile hemangioendothelioma, even with obstructive jaundice, if bile drainage is adequately maintained.

In vivo and ex vivo evaluation of the antithrombogenicity of human thrombomodulin immobilized biomaterials

Human thrombomodulin (hTM) is a newly described endothelial cell associated protein that functions as a potent natural anticoagulant by converting thrombin from a procoagulant protease to an anticoagulant. Focusing on the establishment of the practical evaluation of hTM immobilized materials, the activity of immobilized hTM was evaluated by in vivo and ex vivo blood contacting tests. As the basis for immobilization, regenerated cellulose films and hollow fibers were used. For the in vivo test, hTM immobilized cellular hollow fibers were implanted into dog blood vessels. Using hTM immobilized cellulose hollow fibers, a small scale dialyzer was assembled and its antithrombogenic activity was studied using human blood. As a result, it was revealed that the immobilized hTM still has co-enzymatic activity for activation of Protein C and anticoagulant activity. The coagulation time of the human blood passed through the hTM immobilized small dialyzer was effectively prolonged. It is expected that hTM immobilized cellulose should be a useful antithrombogenic biomaterial.

Immobilization of human thrombomodulin on biomaterials: evaluation of the activity of immobilized human thrombomodulin

Thrombomodulin (TM) is a newly described endothelial cell associated protein that functions as a potent natural anticoagulant by converting thrombin from a procoagulant protease to an anticoagulant. In this study, the immobilization of hTM was investigated in detail using surface modified polymers. As the basis of immobilization, poly(acrylic acid) (PAAc) surface-grafted poly(ethylene) (PAAc-g-PE) film was used with the expectation of increasing the immobilization amount of hTM. The effect of the immobilization reaction on the hTM activities, and the comparison of the activities of the immobilized hTM with the free hTM, were studied.

Immobilization of human thrombomodulin onto poly(ether urethane urea) for developing antithrombogenic blood-contacting materials

Thrombomodulin (TM) is a newly described endothelial cell-associated protein that functions as a potent natural anticoagulant by converting thrombin from a procoagulant protease to an anticoagulant. In this study, focussing on the application of TM for biomedical materials, recombinant human TM (hTM) was immobilized onto the polymers for medical use, and the evaluation of their antithrombogenicity and the interaction with platelets were investigated. As the base polymer for immobilization reaction, poly(ether urethane urea) (PEUU), which was reported to have good blood compatibility, was used. hTM-immobilized PEUU showed superior antithrombogenic activity, such as the prolongation of plasma recalcification time and the inhibition of thrombin-induced platelet aggregation, though the amount of immobilized hTM was very small (i.e. less than 1 microgram/cm2). Platelet adhesions onto hTM-immobilized PEUU were not observed. These results show that the immobilization of hTM does not change the native good blood compatibility of PEUU, but provides excellent anticoagulant activity.

Experimental study of bioactive polyurethane sponge as an artificial trachea

An artificial trachea that has tissue reconstructive activity and elasticity that matches a biologic trachea was fabricated using a polyurethane sponge (PS). The inner surfaces of the PS were modified by immobilizing collagen, fibronectin, RGD peptide, a coating of collagen, and apatite. Two PS pore sizes were prepared, 150 to 350 microns (small pore) and 350 to 710 microns (large pore). When they were implanted in the subcutaneous tissue of rats, study of the implantation showed severe inflammatory cell infiltration with the treated PS, especially with collagen and collagen coating. Infiltration and maturity of fibroblasts inside the PS were noted with fibronectin. Infiltration of inflammatory cells and fibroblasts was noted with small pore PS compared with large pore PS. Partial tracheal defects were patched with PS. Better epithelization of PS patches was observed with fibronectin and apatite compared with the others. The artificial trachea made of PS was transplanted into the tracheas of dogs. No separation of the anastomosis and tissue reconstruction of the artificial trachea wall were observed; however, sputum absorption and tracheal granulation were seen.

Immobilization of human thrombomodulin onto biomaterials. Comparison of immobilization methods and evaluation of antithrombogenicity

Human thrombomodulin (hTM), which is a newly described endothelial cell associated protein that functions as a potent natural anticoagulant by converting thrombin from a procoagulant protease to an anticoagulant, was immobilized on to various substrates by two immobilization methods. As the substrates of immobilization, poly(acrylic acid) surface grafted poly(ethylene) (PAAc-g-PE) film, poly(vinylamine) surface grafted poly(ethylene) film, and PAAc surface grafted nylon were used. For immobilization, simultaneous preactivation methods were used. The effect of the immobilization reaction on hTM activities, the comparison of the activities of immobilized hTM with those of free hTM, and the effect of the thrombin incorporation on antithrombogenic activity were studied. The hTM immobilized onto PAAc-g-PE by preactivation showed the highest antithrombogenic activity. The thrombin incorporation affected protein C activation activity but not the fibrinogen clotting time. hTM immobilized nylon showed greater antithrombogenicity in vitro.

A novel biomaterial: poly(dimethylsiloxane)-polyamide multiblock copolymer I. Synthesis and evaluation of blood compatibility

Aramid-silicone resins (PASs) consisting of aromatic polyamide (aramid) and poly(dimethyl-siloxane) (PDMS) segments were synthesized by low temperature solution polycondensation. For the evaluation of blood compatibility in vitro, two kinds of experiments were carried out. One was the thromboxane B2(TXB2) release test from platelets attaching to PAS and Biomer. The other was the observation of the platelet adhesion on the surfaces of PAS by scanning electron microscopy (SEM). The results indicated that PAS was bio-inert in vitro. The surface chemical composition of PAS films was investigated by means of electron probe micro analysis (EPMA), X-ray photoelectron spectroscopy (XPS), and dynamic contact angle measurements. The relationship between blood compatibility and surface composition of PAS is discussed.

Novel instrumentation monitoring in situ platelet adhesivity with a quartz crystal microbalance

The quartz crystal microbalance (QCM) in a solution is capable of sensing an extremely small mass change in the nanogram range. In this article, the authors attempted to apply QCM to in situ continuous monitoring of platelet adhesion in plasma. The instrumentation consisted of a piezoelectric quartz crystal vacuum-deposited with gold and connected to two electrodes, an oscillation circuit, a frequency counter, and a DC source (5 V), coupled with a personal computer, a television monitor, and a printer. The authors noted resonant frequency shifts to determine weight increase upon cell adhesion. A QCM sensor, with the sensitivity of 1 ng/Hz, was placed horizontally in platelet poor plasma. The authors did not observe any measurable frequency shift upon adding a suspension of non-adherent cells, such as red blood cells and prostaglandin I2-sensitized platelets, indicating that QCM does not count the increase in the mass of cells that simply settled on the quartz. They did observe, however, a time-dependent frequency shift upon addition of platelet rich plasma. Coupled with visual determination of numbers of adherent platelets and their morphology under scanning electron microscopy, they found that the magnitude of shift and its time dependence seem to correlate not only numbers of adherent platelets, but to their spreading state, indicating that QCM detects only the weight at the focal contact region of adherent cells. This suggested that the former contributes to the early phase of the frequency shift, and the latter contributes to a shift change after a longer period of incubation.(ABSTRACT TRUNCATED AT 250 WORDS)

Preparation of an RGD ALB conjugate. In vitro analysis of cellular responses

RGD (Arg-Gly-Asp) tripeptide was identified as the minimal active core peptide sequence common to adhesive proteins. In this paper, the authors report preparation of RGD containing peptide albumin conjugate (RGD ALB), and its effects on cellular adhesive function in vitro. RGD ALB was prepared via a coupling reaction of albumin with pentapeptide (GRGDS; Gly-RGD-Ser) by water soluble carbodiimide. Bovine endothelial cells (ECs) adhered to and spread well on a surface coated with RGD ALB, whereas few ECs adhered on surfaces coated with GRGESP-albumin conjugate (GRGESP peptide with little cell attachment activity; false control) and albumin. Cellular behavior, such as adhesion, spreading, growth, and migration, on surfaces coated with GRD-ALB, fibronectin (FN), and vitronectin (VN) were quantitatively examined. Adherent cell number on RGD ALB coated surfaces was larger than on those coated with FN and VN. Cell morphology on RGD ALB coated surfaces was similar to that on FN coated surfaces. The cell growth and migration activities on RGD ALB coated surfaces were almost equal to those coated with FN and VN. Thus, RGD ALB was found to promote cell adhesion, migration, and growth as effectively as fibronectin. This indicates that an artificial adhesive protein, simply derived with bioactive peptidyl ligand, can find versatile applications in fields in which cellular events play a critical role--for example, extracellular matrices and wound healing promotion aids.

A bioartificial ventricle used as a totally implantable circulatory assist device

The authors designed a totally implantable circulatory assist device consisting of a bioartificial ventricle composed of a skeletal muscle ventricle lined with a bioartificial endocardium. The bioartificial endocardium consists of a structural matrix made of a polyurethane porous membrane, fragmented blood vessels, and collagen gel. The authors prepared the polyurethane porous membrane by solvent cocasting with salt powder. They used collagen gel with fragmented goat carotid vein to perform in vitro construction of the bioartificial endocardium. For in vivo construction of the bioartificial endocardium, the authors used a modified version of the tissue fragment method for vascular prostheses. The authors prepared suspensions of tissue fragments using collagen gel with fragmented goat carotid artery. They used a highly porous fabric vascular prosthesis as a structural matrix; tissue fragments were entrapped on the outer surface of the prosthesis, and the prosthesis then was implanted into the carotid artery of four adult goats. In specimens 1 and 3 months postimplantation, cells from the fragmented tissue regenerated an endothelium-like monolayer sheet on the inner surface of the prostheses. Output of a prototype bioartificial ventricle reached 660 ml/min at an afterload of 60 mmHg and a preload of 20 mmHg. Based on these data, the authors conclude that the bioartificial ventricle is promising as an implantable device with excellent antithrombogenicity.

RGD-albumin conjugate: expression of tissue regeneration activity

Albumin conjugated with Arg-Gly-Asp (RGD) has cellular adhesive activity comparable to that of fibronectin in vitro. This study examined whether RGD-albumin conjugate (RGD-ALB) can promote soft tissue ingrowth into a porous matrix in vivo. Polyurethane sponges with 150-500 microns pore size adsorbed with RGD-ALB, fibronectin and albumin were implanted in the subcutaneous tissue of rats. The RGD-ALB-adsorbed sponge exhibited tissue ingrowth comparable to that of the fibronectin-adsorbed sponge at the early period of implantation. On the other hand, the tissue ingrowth was markedly retarded for non-adsorbed and albumin-adsorbed sponges. The enhanced tissue ingrowth found for RGD-ALB and fibronectin was deduced to be mainly a result of its cell-adhesion activity. It is concluded that RGD-ALB exhibits tissue ingrowth-promoting activity at the initial stage of wound healing as effectively as fibronectin.

Interactions of poly(ethylene glycol)-grafted cellulose membranes with proteins and platelets

The interactions of proteins and platelets with cellulose membranes grafted with poly(ethylene glycol) were studied. The poly(ethylene glycol) grafting was carried out using poly(ethylene glycol)-monoacid and poly(ethylene glycol)-diacid, which have one and two terminal carboxyl groups, respectively. The grafting operates through esterification between the carboxyl groups of poly(ethylene glycol) and the hydroxyl groups on the membrane surface. Both of the poly(ethylene glycol) grafted membranes reduced the complement activation. Adsorption of bovine serum albumin and gamma-globulin increased when the membrane was grafted with poly(ethylene glycol)-diacid, but did not change when it was grafted with poly(ethylene glycol)-monoacid. When platelets were incubated with serum proteins, the platelet adhesion to the membranes slightly decreased by grafting both the poly(ethylene glycol)-diacid and poly(ethylene glycol)-monoacid. The poly(ethylene glycol)-diacid grafted surface showed more clotting than the poly(ethylene glycol)-monoacid grafted and original surfaces.

Cell behaviour on polymer surfaces grafted with non-ionic and ionic monomers

Following exposure to corona discharge, a polyethylene film was graft polymerized with different water-soluble monomers such as acrylamide (non-ionic), acrylic acid (anionic), 2-acrylamide-2-methyl propane sulphonic acid (anionic), styrene sulphonic acid sodium salt (anionic) and N,N-dimethylaminopropyl acrylamide (cationic). Attachment and proliferation of HeLa S3 cells were studied for grafted surfaces with different zeta potentials and contact angles. The polyethylene surface graft polymerized with styrene sulphonic acid sodium salt exhibited high cell attachment and protein adsorption, whereas the cells did not adhere to the 2-acrylamide-2-methyl propane sulphonic acid graft-polymerized surface, although both surfaces had high negative zeta potentials. Graft polymerization of acrylamide reduced the zeta potential of surface close to zero and rejected the cell attachment. The polyethylene surface became highly cell-adhesive through graft polymerization of the cationic N,N-dimethylaminopropyl acrylamide monomer, but too much grafting killed the attaching cells. Once the cells attached to a surface without being killed, they could proliferate at the same growth rate, whatever their surface zeta potential.