Biomedical subjects

H W Sung

Publications and source records attributed to H W Sung.

At least 19 recordsLinked to original sources

PubMed2003

S1 glycoprotein gene analysis of infectious bronchitis viruses isolated in Korea.

Fifteen isolates of Infectious bronchitis virus (IBV) were obtained from the kidney, trachea, and cecal tonsil of IB suspected chickens between 2001 and 2002 years in Korea. The S1 glycoprotein gene of IBV isolates were amplified by reverse transcriptase - polymerase chain reaction (RT-PCR) and analyzed by restriction fragment length polymorphism (RFLP) analysis. Fifteen Korean IBV isolates were classified into 4 groups by their RFLP patterns using restriction enzymes, HaeIII, BstYI, and XcmI. The RFLP patterns for 3, 1, and 1 of 15 isolates corresponded to the patterns of IBV Arkansas, Connecticut, and Massachusetts strains, respectively. Ten of 15 isolates generated unique KM91 RFLP pattern that was observed in the IBV KM 91 strain previously isolated in Korea. To confirm genetic diversity in the S1 genes of IBV isolates, viral RNAs of representative 9 of 15 IBV isolates were amplified, cloned, sequenced and compared with published sequences for non-Korean IBV strains. Korean IBV isolates showed amino acid sequence similarity between 61.8% (K446-01 and K161-02) and 96.1% (K281-01 and K210-02) with each other and they showed amino acid sequence similarity between 42.9% (K161-02 and GA980470) and 96.5% (K203-02 and KB8523) compared to non-Korean IBV strains. By phylogenetic tree analysis, Korean IBV field isolates were branched into five clusters in which 3 clusters were differentiated from non-Korean IBV strains. Especially, Korean IBV isolates K069-01, K507-01, K774-01 and K142-02 formed a separate cluster. It seems that IBVs continue to evolve and IBVs showing various genetic differences may cocirculate in Korea.

Amino Acid Sequence↗

PubMed2003

Pathogenesis of and immunity to a new influenza A (H5N1) virus isolated from duck meat.

The outbreak of avian influenza H5N1 in Hong Kong in 1997 raised concerns about the potential for the H5 subtype to cause a human pandemic. In 2001 a new H5N1 virus, A/Duck Meat/Anyang/AVL-1/2001 (A/Dkmt), was isolated from imported duck meat in Korea. The pathogenesis of this virus was investigated in mice. A/Dkmt virus had low infectivity but was lethal for mice at high doses, and at lethal doses, the virus replicated in the brains of infected mice. A/Dkmt virus cross-reacted poorly with ferret antisera raised against human H5N1 viruses, but prior infection with A/Dkmt virus protected mice from death after secondary infection with human H5N1 virus.

Animals↗

PubMed2003

Evaluation of a high-pathogenicity H5N1 avian influenza A virus isolated from duck meat.

The introduction of an influenza A virus possessing a novel hemagglutinin (HA) into an immunologically naive human population has the potential to cause severe disease and death. Such was the case in 1997 in Hong Kong, where H5N1 influenza was transmitted to humans from infected poultry. Because H5N1 viruses are still isolated from domestic poultry in southern China, there needs to be continued surveillance of poultry and characterization of virus subtypes and variants. This study provides molecular characterization and evaluation of pathogenesis of a recent H5N1 virus isolated from duck meat that had been imported to South Korea from China. The HA gene of A/Duck/Anyang/AVL-1/01 (H5N1) isolate was found to be closely related to the Hong Kong/97 H5N1 viruses. This virus also contained multiple basic amino acids adjacent to the cleavage site between HA1 and HA2, characteristic of high-pathogenicity avian influenza viruses (HPAI). The pathogenesis of this virus was characterized in chickens, ducks, and mice. The DK/Anyang/AVL-1/01 isolate replicated well in all species and resulted in 100% and 22% lethality for chickens and mice, respectively. No clinical signs of disease were observed in DK/Anyang/AVL-1/01-inoculated ducks, but high titers of infectious virus could be detected in multiple tissues and oropharyngeal swabs. The presence of an H5N1 influenza virus in ducks bearing a HA gene that is highly similar to those of the pathogenic 1997 human/poultry H5N1 viruses raises the possibility of reintroduction of HPAI to chickens and humans.

Animals↗

PubMed2001

Stability of a biological tissue fixed with a naturally occurring crosslinking agent (genipin).

The study was undertaken to investigate the stability of a biological tissue fixed with a naturally occurring crosslinking agent (genipin) at distinct elapsed storage durations. The glutaraldehyde-fixed counterpart was used as a control. Porcine pericardia procured from a slaughterhouse were used as raw materials. After fixation, the fixed tissues were sterilized in a graded series of ethanol solutions and thoroughly rinsed in phosphate buffered saline for 1 day, and then stored in a jar containing sterilized water. The samples were taken out and tested for their stability during the durations of 1day through 6 months after storage. The stability of each study group was tested by measuring its tensile strength, free-amino-group content, and denaturation temperature. Additionally, the cytotoxicity of each test sample and its corresponding storage solution were investigated in vitro using 3T3 fibroblasts. The results were examined using a microscope and 3-(4,5-dimethylthiazol-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. It was found that the stability of the genipin-fixed tissue during storage was superior to its glutaraldehyde-fixed counterpart. The differences in stability between the genipin- and glutaraldehyde-fixed tissues during storage may be caused by their differences in crosslinking structure. There was no apparent cytotoxicity for both the genipin-fixed tissue and its corresponding storage solution throughout the entire course of the study, whereas significant cytotoxicity was observed for both the glutaraldehyde-fixed tissue and its storage solution. However, the cytotoxicity of the glutaraldehyde-fixed tissue decreased with increasing elapsed storage duration, whereas that of its corresponding storage solution increased. This suggested that the toxic residues remaining in the glutaraldehyde-fixed tissue leached out slowly into its corresponding storage solution during the course of storage.

3T3 Cells↗

PubMed2001

Effects of heparin immobilization on the surface characteristics of a biological tissue fixed with a naturally occurring crosslinking agent (genipin): an in vitro study.

Heparinized biomaterials have been used to manufacture blood-contacting prostheses. The present study was intended to characterize the surface properties of a genipin-fixed biological tissue immobilized with heparin using the methods of ionic binding (the /h-i tissue) or covalent binding via multi-point attachment (the /h-m tissue) or end-point attachment (the /h-e tissue). The surface characteristics of test tissues evaluated were water contact angle, surface tension, protein adsorption, platelet adhesion, and cellular compatibility. Nonheparinized and the glutaraldehyde-fixed counterparts were used as controls. It was found that immobilization of heparin on the glutaraldehyde- and genipin-fixed tissues increased their hydrophilicity and surface tension and suppressed their mole ratio of adsorbed fibrinogen to adsorbed albumin and the amount of platelets adhered. Among the heparinized tissues, the /h-m tissue was more hydrophobic and had a higher mole ratio of adsorbed fibrinogen to adsorbed albumin and a greater amount of platelets adhered than the /h-i and /h-e tissues. In general, the surface characteristics of the /h-i tissue were comparable to the /h-e tissue. However, it is known that the ionically immobilized heparin may be displaced from the surface by an ion-exchange mechanism when exposed to blood. There were no significant differences in hydrophilicity, surface tension, the mole ratio of adsorbed fibrinogen to adsorbed albumin, and the amount of platelet adhesion between the glutaraldehyde- and genipin-fixed tissues in comparison with their respective counterparts. However, the cellular compatibility of the genipin-fixed tissues with or without heparinization was significantly superior to its glutaraldehyde-fixed counterparts.

Adsorption↗

PubMed2001

Reconstruction of the right ventricular outflow tract with a bovine jugular vein graft fixed with a naturally occurring crosslinking agent (genipin) in a canine model.

OBJECTIVE: This study was designed to evaluate a newly developed biologic valved conduit fixed with genipin used to reconstruct the right ventricular outflow tract in a canine model. METHODS: Fresh bovine jugular veins with a retained native valve procured from a slaughterhouse were used as raw materials to fabricate the valved conduits. A naturally occurring crosslinking agent, genipin, was used to fix the procured jugular veins. The glutaraldehyde-fixed counterpart was used as a control. A canine model was used in the study. RESULTS: Echocardiography revealed that the motion of the valvular leaflets in both the glutaraldehyde- and genipin-fixed conduits was satisfactory. The transvalvular pressure gradients of both studied groups were minimal. No endothelium-like cells were observed on the luminal surface of the conduit and the valvular leaflet for the glutaraldehyde-fixed group throughout the entire course of the study. In contrast, endothelium-like cells were observed on the entire surface of the genipin-fixed valved conduit retrieved at 6 months postoperatively in all the cases studied. There was no evidence of luminal fibrous peel in any the valved conduits studied. Degradation of valvular leaflet in one of the glutaraldehyde-fixed conduits was observed. In this particular case, thrombus formation was also observed on the surface of the valvular leaflet. On the other hand, no apparent degradation or thrombus formation was observed on the surfaces of the genipin-fixed valvular leaflet and conduit. A significantly more severe inflammatory reaction was observed for the glutaraldehyde-fixed conduit than for its genipin-fixed counterpart throughout the entire course of the study. The calcium contents of the samples before implantation and those retrieved at distinct implantation duration were minimal for both the glutaraldehyde- and genipin-fixed tissues. CONCLUSION: Although further studies are necessary, the genipin-fixed valved conduit appears to have great potential in helping mitigate the complications observed in the commercially available conduits.

Adhesives↗

PubMed2001

In vitro evaluation of a chitosan membrane cross-linked with genipin.

The study was to evaluate the characteristics of a chitosan membrane cross-linked with a naturally-occurring cross-linking reagent, genipin. This newly-developed genipin-cross-linked chitosan membrane may be used as an implantable drug-delivery system. The chitosan membrane without cross-linking (fresh) and the glutaraldehyde-cross-linked chitosan membrane were used as controls. The characteristics of test chitosan membranes evaluated were their cross-linking degree, swelling ratio, mechanical properties. antimicrobial activity, cytotoxicity, and degradability. It was found that cross-linking of chitosan membrane using genipin increased its ultimate tensile strength but significantly reduced its strain-at-fracture and swelling ratio. There was no significant difference in antimicrobial activity between the genipin-cross-linked chitosan membrane and its fresh counterpart. Additionally, the results showed that the genipin-cross-linked chitosan membrane had a significantly less cytotoxicity and a slower degradation rate compared to the glutaraldehyde-cross-linked membrane. These results suggested that the genipin-cross-linked chitosan membrane may be a promising carrier for fabricating an implantable drug-delivery system. The drug-release characteristics of the genipin-cross-linked chitosan membrane are currently under investigation.

Adhesives↗

PubMed2000

In vitro evaluation of the genotoxicity of a naturally occurring crosslinking agent (genipin) for biologic tissue fixation.

The objective of the present study was to evaluate in vitro, using Chinese hamster ovary (CHO-K1) cells, the genotoxicity of genipin, a naturally occurring crosslinking agent. Glutaraldehyde, the most commonly used crosslinking agent for biologic tissue fixation, was employed as a reference chemical. The selected procedures for this evaluation were the micronucleus (MN) and sister chromatid exchange (SCE) assays with or without the addition of a metabolic activation system (S9 mix). Before starting the genotoxicity assays, the maximum noncytotoxic amounts of glutaraldehyde and genipin were determined using the MTT assay. The results obtained in the MTT assay revealed that the cytotoxicity of genipin was significantly lower than that of glutaraldehyde with or without S9 mix. The frequencies of MN observed in the cases drugged with varying concentrations of glutaraldehyde or genipin were not statistically different from those seen in the negative controls (blank) in the presence or absence of S9 mix. However, it was noted that glutaraldehyde significantly inhibited the cell-cycle progression while the cells drugged with genipin did not result in cell-cycle delay. In the SCE assay, the numbers of SCE per cell observed in the cases drugged with varying concentrations of glutaraldehyde were significantly greater than those found in the negative controls with or without S9 mix. Nevertheless, these numbers were still low compared to the numbers of SCE induced by the strong mutagens used as our positive control substances. This suggests that glutaraldehyde may produce a weakly clastogenic response in CHO-K1 cells. In contrast, the numbers of SCE per cell obtained in the cases drugged with genipin were comparable to those observed in the negative controls in those that were except drugged with the highest dose (50 ppm). This suggests that genipin does not cause clastogenic response in CHO-K1 cells provided its concentration is lower than 50 ppm. In conclusion, as far as cytotoxicity and genotoxicity are concerned, genipin is a promising crosslinking agent for biologic tissue fixation.

Animals↗

PubMed2000

Fixation of biological tissues with a naturally occurring crosslinking agent: fixation rate and effects of pH, temperature, and initial fixative concentration.

In an attempt to overcome the cytotoxicity problem of the glutaraldehyde-fixed tissues, a naturally occurring crosslinking agent (genipin) was used by our group to fix biological tissues. The study was intended to investigate the rate of tissue fixation by genipin. Glutaraldehyde was used as a control. In addition, the degrees of tissue fixation by genipin at different pHs (pH 4.0, pH 7. 4, pH 8.5, or pH 10.5), temperatures (4 degrees C, 25 degrees C, 37 degrees C, or 45 degrees C), and initial fixative concentrations (0.250%, 0.625%, or 1.000%) were examined. The results obtained revealed that the rate of tissue fixation by glutaraldehyde was significantly faster than that by genipin. The degree of tissue fixation by genipin may be controlled by adjusting its fixation duration or fixation conditions. The order in degree of tissue fixation by genipin at different pHs, from high to low, was: at nearly neutral pH (pH 7.4 or pH 8.5) > at basic pH (pH 10.5) > at acidic pH (pH 4.0). The degrees of tissue fixation by genipin at different temperatures were about the same, except for that at 4 degrees C. In contrast, the initial fixative concentration did not seem to affect the degree of tissue fixation by genipin, if only the amount of genipin in the fixation solution was sufficient to complete tissue fixation. The concentrations of genipin in the aqueous solutions at different pHs, temperatures, and initial fixative concentrations tended to decrease with time with or without the occurrence of tissue fixation. This indicated that genipin was not stable in the aqueous solution. The instability of aqueous genipin was more remarkable with increasing pH or temperature. The results obtained in this study may be used to optimize the fixation process for developing bioprostheses fixed by genipin.

Animals↗

PubMed2000

In vitro surface characterization of a biological patch fixed with a naturally occurring crosslinking agent.

The study was designed to characterize the surface properties (including water contact angle, surface tension, protein adsorption, platelet adhesion, and cellular compatibility) of a biological patch fixed with genipin, a naturally occurring crosslinking agent. Fresh and glutaraldehyde-fixed counterparts were used as controls. It was found that both glutaraldehyde and genipin are effective crosslinking agents for biological tissue fixation. Fixation of biological tissue with glutaraldehyde or genipin significantly increased its hydrophilicity and surface tension and reduced its mol ratio of adsorbed fibrinogen to adsorbed albumin as well as the amount of adhered platelet. There were no significant differences in hydrophilicity, surface tension, the mole ratio of adsorbed fibrinogen to adsorbed albumin, and the amount of platelet adhesion between the glutaraldehyde- and genipin-fixed tissues. However, the cellular compatibilities of fresh and the genipin-fixed tissues were significantly superior to the glutaraldehyde-fixed tissue.

3T3 Cells↗

PubMed1999

Evaluation of gelatin hydrogel crosslinked with various crosslinking agents as bioadhesives: in vitro study.

Bioadhesives are used for tissue adhesion and hemostasis in surgery. A gelatin-resorcinol mixture crosslinked with formaldehyde (GRF glue) and/or glutaraldehyde (GRG) is used for this purpose. Although the bonding strength of the GRF glue to tissue is satisfactory, concerns about the cytotoxicity of formaldehyde are reported in the literature. It was suggested that the cytotoxicity problem of the GRF glue may be overcome by changing its crosslinking method. The study was therefore undertaken to assess the feasibility of using an epoxy compound (GRE glue), a water-soluble carbodiimide (GAC glue), or genipin (GG glue) to crosslink with a gelatin hydrogel as new bioadhesives. GRF glue and GRG glue were used as controls. The results of our cytotoxicity study suggested that the cellular compatibility of the GAC and GG glues was superior to the GRF, GRG, and GRE glues. The gelation time for the GG glue was relatively longer than the GRF and GRG glues, while no gelation time could be determined for the GAC glue. Additionally, it took approximately 17 h for the GRE glue to become adhesive. The GRF and GRG glues had the greatest bonding strengths to tissue among all test adhesives, while the bonding strengths of the GAC and GG glues were comparable. In contrast, there was almost no bonding strength to tissue for the GRE glue. However, the GRF and GRG glues were less flexible than the GAC and GG glues. Subsequent to the bonding strength measurement, each test adhesive was found to adhere firmly to the tissue surface and underwent cohesive failure during the bond breaking. In conclusion, the GRF and GRG glues may be used as tissue adhesives when their ability to bind tissue rapidly and tightly is required; the GAC and GG glues are preferable when the adhesive action must be accompanied with minimal cytotoxicity and stiffness; and the GRE glue is not suitable for bioadhesion in clinical applications.

3T3 Cells↗

PubMed1999

Crosslinking characteristics and mechanical properties of a bovine pericardium fixed with a naturally occurring crosslinking agent.

Currently available crosslinking agents used in fixing bioprostheses are all highly (or relatively highly) cytotoxic, which may induce an adverse inflammatory reaction in vivo. It is therefore desirable to provide a crosslinking agent that is of low cytotoxicty and may form stable and biocompatible crosslinked products. To achieve this goal, a naturally occurring crosslinking agent-genipin-was used by our group to fix biological tissues. Genipin may be obtained from its parent compound, geniposide, which may be isolated from the fruits of Gardenia jasminoides Ellis. In our previous studies, it was found that the cytotoxicity of genipin is significantly lower than both glutaraldehyde and an epoxy compound. Also, it was shown that genipin can form stable and biocompatible crosslinked products. The present study further investigates the crosslinking characteristics and mechanical properties of a genipin-fixed bovine pericardium. Fresh and glutaraldehyde- and epoxy-fixed counterparts were used as controls. It was found that the denaturation temperatures of the glutaraldehyde- and genipin-fixed tissues were significantly greater than the epoxy-fixed tissue, although their fixation indices were comparable. The mechanical properties of fresh bovine pericardium are anisotropic. However, fixation tended to eliminate tissue anisotropy. The tendency in the elimination of tissue anisotropy for the genipin-fixed tissue was more remarkable than for the glutaraldehyde- and epoxy-fixed tissues. In addition, the genipin-fixed tissue had the greatest ultimate tensile strength and toughness among all the fixed tissues. Distinct patterns in rupture were observed in the study: The torn collagen fibers of the genipin- and glutaraldehyde-fixed tissues appeared to be bound together, while those of fresh and the epoxy-fixed tissues stayed loose. The results obtained in the study suggests that tissue fixation in glutaraldehyde, epoxy compound, and genipin may produce distinct crosslinking structures. The differences in crosslinking structure may affect the crosslinking characteristics and mechanical properties of the fixed tissues.

Animals↗

PubMed1999

Mechanical properties of a porcine aortic valve fixed with a naturally occurring crosslinking agent.

The study investigates the mechanical properties of porcine aortic valve leaflets fixed with a naturally occurring crosslinking agent, genipin, at distinct pressure heads. Fresh and the glutaraldehyde-fixed counterparts were used as controls. Subsequent to fixation, the changes in leaflet collagen crimps and its surface morphology were investigated by light microscopy and scanning electron microscopy (SEM). Also, the crosslinking characteristics of each studied group were determined by measuring its fixation index and denaturation temperature. In the mechanical testing, tissue strips made from each studied group were examined in both the circumferential and radial directions. Histological and SEM comparisons between fresh porcine aortic valve leaflet and those fixed at medium or high pressure revealed that the following changes may occur: elimination of the natural collagen crimping, and extensive loss of the endothelial layer. The denaturation temperatures of the glutaraldehyde-fixed leaflets were significantly greater than the genipin-fixed leaflets; however, their fixation indices were comparable. Generally, fixation pressure did not affect the crosslinking characteristics of the genipin- and glutaraldehyde-fixed leaflets. It was found that fixation of porcine aortic valves in genipin or glutaraldehyde did not alter the mechanical anisotropy observed in fresh valve leaflets. This indicated that the intramolecular and intermolecular crosslinks introduced into the collagen fibrils during fixation is of secondary importance to the presence of structural and mechanical anisotropy in fresh leaflet. Tissue fixation in genipin or glutaraldehyde may produce distinct crosslinking structures. However, the difference in crosslinking structure between the genipin- and glutaraldehyde-fixed leaflets did not seem to cause any significant discrepancies in their mechanical properties when compared at the same fixation pressure. Nevertheless, regardless of the crosslinking agent used, changes in mechanical properties and ruptured patterns were observed when the valve leaflets were fixed at distinct pressures.

Animals↗

PubMed1999

In vitro evaluation of cytotoxicity of a naturally occurring cross-linking reagent for biological tissue fixation.

A recognized drawback of the currently available chemical cross-linking reagents used to fix bioprostheses is the potential toxic effects a recipient may be exposed to from the fixed tissues and/or the residues. It is, therefore, desirable to provide a cross-linking reagent which is of low cytotoxicity and may form stable and biocompatible cross-linked products. To achieve this goal, a naturally occurring cross-linking reagent -- genipin -- which has been used in herbal medicine and in the fabrication of food dyes, was used by our group to fix biological tissues. The study was to assess the cytotoxicity of genipin in vitro using 3T3 fibroblasts (BALB/3T3 C1A31-1-1). Glutaraldehyde, the most commonly used cross-linking reagent for tissue fixation, was used as a control. The cytotoxicity of the glutaraldehyde- and genipin-fixed tissues and their residues was also evaluated and compared. The observation in the light microscopic examination revealed that the cytotoxicity of genipin was significantly lower than that of glutaraldehyde. Additionally, the results obtained in the MTT assay implied that genipin was about 10000 times less cytotoxic than glutaraldehyde. Moreover, the colony forming assay suggested that the proliferative capacity of cells after exposure to genipin was approximately 5000 times greater than that after exposure to glutaraldehyde. It was noted that the cells seeded on the surface of the glutaraldehyde-fixed tissue were not able to survive. In contrast, the surface of the genipin-fixed tissue was found to be filled with 3T3 fibroblasts. Additionally, neocollagen fibrils made by these fibroblasts were observed on the genipin-fixed tissue. This fact suggested that the cellular compatibility of the genipin-fixed tissue was superior to its glutaraldehyde-fixed counterpart. Also, the residues from the glutaraldehyde-fixed tissue markedly reduced the population of the cultured cells, while those released from the genipin-fixed tissue had no toxic effect on the seeded cells. In conclusion, as far as cytotoxicity is concerned, genipin is a promising cross-linking reagent for biological tissue fixation.

3T3 Cells↗

PubMed1999

Gelatin-derived bioadhesives for closing skin wounds: an in vivo study.

Bioadhesives have been used in surgery as hemostatic and wound healing agents. GRF (gelatin + resorcinol + formaldehyde) glue, composed of a mixture of gelatin and resorcinol polymerized by the addition of formaldehyde, has been used for this purpose. Widespread acceptance of the GRF glue, however, has been limited by reports of cytotoxicity due to its release of formaldehyde upon degradation. It has been suggested by Wertzel et al. that the cytotoxicity problem of GRF glue may be overcome by changing its cross-linking method. The study was, therefore, undertaken to assess the feasibility of using a water-soluble carbodiimide or genipin to cross-link gelatin as new bioadhesives to close skin wound lesions in a rat model. Formaldehyde-cross-linked counterpart (GRF glue) and a resorbable suture were used as controls. It was noted that the tensile strength of the skin across each wound treated by either application of test glues or suture increased consistently with time during the healing process. Also, the wounds repaired by test glues or suture caused no calcification. The suture used in the study was completely resorbed at the wound area in about 6 days postoperatively. However, the durations required to completely resorb the carbodiimide- or genipin-cross-linked glues were approximately the same (9 days), while it took about 14 days to completely resorb the formaldehyde-cross-linked glue. The healing process for the suture wound repaired was more rapid than those treated by test glues. Of the test glues, the wounds treated by the carbodiimide- or genipin-cross-linked glues induced less inflammatory response and recovered sooner than that treated by the formaldehyde-cross-linked glue. This indicated that the biocompatibility of the carbodiimide- or genipin-cross-linked glues was superior to the formaldehyde-cross-linked glue. The results of this study may serve as a preliminary experimental model for the further investigation of both the carbodiimide- and genipin-cross-linked glues when applied to human skin closure.

Animals↗

PubMed1998

Feasibility study of a natural crosslinking reagent for biological tissue fixation.

Bioprostheses derived from biological tissues must be chemically modified and subsequently sterilized before they can be implanted in humans. Various crosslinking reagents, including formaldehyde, glutaraldehyde, dialdehyde starch, and epoxy compound, have been used to chemically modify biological tissues. However, these synthetic crosslinking reagents are all highly (or relatively highly) cytotoxic. It is therefore desirable to provide a crosslinking reagent suitable for use in biomedical applications that is of low cytotoxicity and that forms stable and biocompatible crosslinked products. This study evaluates the feasibility of using a naturally occurring crosslinking reagent--genipin--to chemically modify biological tissues. Genipin and its related iridoid compounds, extracted from gardenia fruits, have been used in traditional Chinese medicine for the treatments of jaundice and various inflammatory and hepatic diseases. In this feasibility study, the cytotoxicity of genipin and the crosslinking characteristics of genipin-fixed biological tissues were investigated. Fresh porcine pericardia procured from a slaughterhouse were used as raw materials. Glutaraldehyde and an epoxy compound (ethylene glycol diglycidyl ether), which has been used extensively in developing bioprostheses, were used as controls. It was found that the cytotoxicity of genipin was significantly lower than that of glutaraldehyde and the epoxy compound. The amino acid residues in the porcine pericardium that may react with genipin were lysine, hydroxylysine, and arginine. Additionally, the genipin-fixed tissue had a mechanical strength and resistance against enzymatic degradation comparable to the glutaraldehyde-fixed tissue. This suggests that genipin can form stable crosslinked products. The results of this in vitro study demonstrate that genipin is an effective crosslinking reagent for biological tissue fixation.

Animals↗

PubMed1998

Biocompatibility study of a biological tissue fixed with a naturally occurring crosslinking reagent.

A recognized disadvantage of the currently available chemical reagents used to fix bioprostheses is the potential toxic effects a recipient may be exposed to from residues. It is therefore desirable to provide a crosslinking reagent that is of low cytotoxicity and can form stable and biocompatible crosslinked products. To achieve this goal, a naturally occurring crosslinking reagent-genipin-was used by our group to fix biological tissues. Genipin can be obtained from its parent compound geniposide, which can be isolated from the fruits of Gardenia jasminoides ELLIS. In our previous feasibility study, it was found that the cytotoxicity of genipin is significantly lower than both glutaraldehyde and an epoxy compound. Additionally, it was shown that genipin can form stable crosslinked products. The present study further investigates the biocompatibility of a genipin-fixed porcine pericardium implanted subcutaneously in a growing rat model. The fresh, glutaraldehyde-, and epoxy-fixed counterparts were used as controls. It was noted that the inflammatory reaction of the genipin-fixed tissue was significantly less than its glutaraldehyde- and epoxy-fixed counterparts. Also, the genipin-fixed tissue has tensile strength and resistance against in vivo degradation comparable to the glutaraldehyde-fixed tissue. Additionally, the calcium content of the genipin-fixed tissue measured throughout the entire course of the study was minimal. Nevertheless, further study in calcification for the genipin-fixed tissue should be conducted in a blood-contact environment. The results obtained in this subcutaneous study indicate that genipin is a promising crosslinking reagent for biological tissue fixation. However, further durability testing in vitro and in vivo are needed to determine the relative functional merits of this new crosslinker.

Animals↗

PubMed1998

Pulmonary artery hemodynamics with varying degrees of valvular stenosis: an in vitro study.

The study was to investigate the effects of varying degrees of valvular stenosis on the hemodynamics of the main (MPA), left (LPA), and right (RPA) pulmonary arteries. Particle flow visualization was used to examine the flow patterns in a series of pulmonary artery models manufactured out of glass. These glass models were made based on the geometry of the porcine pulmonary arteries with dilatation in the MPA and LPA. Also, detailed pressure mappings in the models were conducted using a side-hole catheter. As the valve became stenotic, a jet-like flow was observed in the M PA. A higher degree of valvular stenosis corresponded to a narrower jet. This jet-like flow was noted to deflect away from the centerline and impinge on the roof of the dilated MPA. Additionally, a notable pressure gradient across the deflected jet-like flow in the direction of its radius of curvature was seen. Moreover, secondary flows started to appear in the dilated MPA. This suggested that the change in geometry in the MPA, due to its dilatation, had a marked effect on the pulmonary artery hemodynamics. In the LPA and RPA, the strengths of the secondary flows increased as the valve became more stenotic. The flow patterns observed in the LPA appeared to be more disturbed than in the RPA, due to the poststenotic, dilatation present in the LPA. Pressure recovery along the axial direction in the M PA was observed for all the stenotic valves studied. As the degree of valvular stenosis increased, the transvalvular energy loss increased. Moreover, it was observed that the energy loss decreased progressively as the flow traveled downstream. This tendency was consistent with the phenomenon of pressure recovery observed in the pressure measurement. The study demonstrates the importance of analyzing biological flows from a three-dimensional viewpoint.

Algorithms↗