Shrink Temperature Research Articles

Glutaraldehyde fixation of venous valve tissue: A benchmark for alternative fixation methods.

Bioprosthetic venous valves have yet to achieve long-term patency due to issues with calcification following implantation that is influenced by current xenograft fixation methods, most notably glutaraldehyde. The goal of this study was to investigate the effects of glutaraldehyde fixation on the functional properties of venous tissue to establish a benchmark for the evaluation of alternative fixation methods. The degree of crosslinking was evaluated by determining shrink temperature and the stability of tissue with pronase and collagenase digestion. Glutaraldehyde fixation of venous tissue was confirmed by a significant difference in the shrink temperature between fresh and glutaraldehyde treated samples. Significant differences in the amount of tissue remaining following digestion were observed for venous versus cardiac tissue. This study demonstrates the importance of tissue-specific evaluation in the development of alternative xenograft fixation methods to improve outcomes with bioprosthetic venous valves.

A novel anti-calcification method for bioprosthetic heart valves using dopamine-modified alginate

Calcification is one of the main causes for bioprosthetic heart valves (BHVs)’ failure. Reported strategies to improve BHVs’ anti-calcification properties only target some of risk factors for calcification. In the current study, we demonstrated dopamine-modified alginate coating served as a protected layer for BHVs’ anti-calcification. Alginate coating was characterized by infrared spectroscopic analysis, ultraviolet spectrophotometer, and water contact angle test. By both high-calcium and high-phosphorus in vitro calcification model and rat subdermal implant in vivo calcification model, our results showed alginate-coated BHVs’ have greatly improved BHVs’ anti-calcification performance due to constant ionic exchange of calcium and sodium. Besides, alginate-coated BHVs did not change BHVs’ mechanical strength and tissue’s shrink temperature. This was the first proof-of-concept study to verify that alginate coating would be a novel method for BHVs’ anti-calcification.

Shrink-induced graphene sensor for alpha-fetoprotein detection with low-cost self-assembly and label-free assay

Combination of shrink induced nano-composites technique and layer-by-layer (LbL) self-assembled graphene challenges controlling surface morphology. Adjusting shrink temperature achieves tunability on graphene surface morphology on shape memory polymers, and it promises to be an alternative in fields of high-surface-area conductors and molecular detection. In this study, self-assembled graphene on a shrink polymer substrate exhibits nanowrinkles after heating. Induced nanowrinkles on graphene with different shrink temperature shows distinct surface roughness and wettability. As a result, it becomes more hydrophilic with higher shrink temperatures. The tunable wettability promises to be utilized in, for example, microfluidic devices. The graphene on shrink polymer also exhibits capability of being used in sensing applications for pH and alpha-fetoprotein (AFP) detection with advantages of label free and low cost, due to self-assembly technique, easy functionalization, and antigen-antibody reaction on graphene surface. The detection limit of AFP detection is down to 1 pg/mL, and therefore the sensor also has a significant potential for biosensing as it relies on low-cost self-assembly and label-free assay.

Comparación de la curtición con harina de Caesalpinia Spinosa, con una curtición mineral con sulfato de cromo para pieles caprinas

En el Laboratorio de Curtiembre de Pieles de la FCP, de la ESPOCH, se realizó la comparación de la curtición con extracto de polifenoles vegetales de Caesalpinia spinosa, con una curtición mineral con sulfato de cromo para pieles caprinas, es decir se aplicaron 2 tratamientos con 7 repeticiones cada uno y, en dos ensayos consecutivos dando un total de 28 unidades experimentales, modelados bajo un diseño completamente al Azar en arreglo bifactorial. Los resultados indican que La curtición más adecuado fue al utilizar Polifenoles vegetales de Caesalpinia spinosa (tara), ya que se logra obtener cueros de muy buena clasificación, observándose que el porcentaje de elongación (72,12%) y resistencia a la tensión (333,24 N/ cm2), no registraron diferencias estadísticas sin embargo numéricamente se aprecia superioridad en los cueros curtidos al vegetal (T1), al igual que para la temperatura de encogimiento, (92,86oC), siendo las diferencias altamente significativas. La evaluación sensorial determina mayor llenura (4,50 puntos), al utilizar curtiente vegetal (T1), mientras tanto que finura de flor (4,57 puntos) y plenitud (4,71 puntos), con sulfato de cromo. La evaluación económica determina que la curtición con Polifenoles vegetales (T1), proporciona mayor rentabilidad al proceso productivo ya que al ser la relación beneficio costo de 1,37, indica una ganancia de 37%; Por lo que se recomienda utiliza la curtición vegetal con Polifenoles vegetales de la tara ya que se mejora las características del cuero, permitiendo dotar a los artesanos de una materia prima elevada que se reflejara sobre el artículo final como es el calzado.

Study on the Shrinkable Behavior of PETG/PET Blending Shrink Film

This paper has studied heat shrinkable behaviors of PETG/PET blending film under different blending ratio. The shrink curve, shrink force, film structure and film seaming property were studied by use of electron stretcher, SEM, shrink force tester, shrinkage tester and so on. The results indicated that PETG/PET blending film had uniform internal structure, single melting point which increased with the PET content, and more than 75% TD shrinkage of PETG/PET blending film was achieved which can be widely used in sleeve labels, but MD shrinkage and shrink force was gradually increased with the increase of PET content inside. At the same time, PETG/PET shrink film had better film stiffness, lower seaming strength, higher density and sharper shrink curve under same shrink temperature.

“Blown pack” Probabilistic Modeling for C. Algidicarnis and C. Estertheticum under the Effects of Storage Temperature, Vacuum Level and Package Shrink Temperature

A model for ‘blown pack’ probability (BPP) caused by spores of C.estertheticum DSM8809 and C.algidicarnis, was developed as a function of vacuum packaging variables: storage temperature(ST:-2, 2, 4 and 15°C), vacuum level(VL:6 and 9mBar) and heat shrink temperature(HST:83 and 87°C). Beef meat pieces, were inoculated with spore suspensions individually at 102spores/cm2, packed and daily monitored up to 90 days. The lower BPP, estimated by the log-logistic model, for C.algidicarnis was 0.8% at:-1.5°C/6mBar/87°C while for C.estertheticum was 99.13% at the same conditions. For both organisms, tested variables were unable to eliminate the risk of blown packaged spoilage, at 102spores/cm2 contamination level.

The effects of the covalent attachment of 3-(4-hydroxy-3,5-di-tert-butylphenyl) propyl amine to glutaraldehyde pretreated bovine pericardium on structural degeneration, oxidative modification, and calcification of rat subdermal implants.

Bioprosthetic heart valves (BHV) fabricated from glutaraldehyde pretreated heterograft materials, porcine aortic valves or bovine pericardium (BP), are widely used in cardiac surgery. BHV progressively fail in clinical use due to structural degeneration. Previously we reported that dityrosine, an oxidized amino acid, was present in failed clinical BP-BHV explants; unimplanted BP had no detectable dityrosine. In the same studies BP were demonstrated in vitro to be susceptible to oxidative damage, that could be mitigated with BP covalently modified with the antioxidant, 3-(4-hydroxy-3,5-di-tert-butylphenyl)propyl amine (DBP). The present studies compared in rat subdermal implants glutaraldehyde pretreated BP to BP modified with either DBP or the chemical reactions used to link DBP. All BP explants regardless of DBP demonstrated reduced hydroxyproline and increased digestibility by collagenase. However, the DBP-BP explants showed significant inhibition of reduced explant shrink temperatures (an index of crosslinking) as compared with control BP. Significant mitigation of calcification was observed in both the BP-DBP and chemically modified explants as compared with BP. Dityrosine was not detectable in the 90 day explants. It is concluded that rat subdermal BP implants undergo both calcific and noncalcific structural degeneration, but without the formation of dityrosine, unlike clinical BP explants.

A Polyamic Acid from Pyromellitic Dianhydride and Diaminodiphenyl Ether for Thickening Leather and Reducing Chromium Offer in Tannage

A polyamic acid suitable for either pretanning or retanning wet-blue in leather industry has been synthesized by polycondensing pyromellitic dianhydride with diaminodiphenyl ether. Its performances for improving physical properties of crust leather, reinforcing absorption and fixation of chromium were investigated by applying it in a reduced chromium offer system. The results show that the extension and tearing strength, especially thickness of crust leather can be significantly improved by the polyamic acid, and residual chromium in spent tanning bath could be reduced to below 40 mgCr+3/l by pretanning with the polyamic acid. The chromium released from wet-blue during fatliquoring can be reduced by 85.7%, and kept at a much lower limit of 6 mg/l by the polyamic acid. A much fuller crust leather with shrink temperature of over 95°C can be obtained with 3% of normal chrome powder by pretannig or retanning with the polyamic acid. Therefore, this polyamic acid has the good potential for industrial application in ecological leather.

Synthesis of a phenol copolymer with horseradish peroxidase and the study of its structure–property relations

AbstractA phenol copolymer was synthesized by the free‐radical copolymerization of p‐hydroxybenzaldehyde (HBA) and p‐phenolsulfonate with horseradish peroxidase (HRP)/H2O2 as an initiator. The synthesis process included aldehyde protection via acetalization, enzymatic polymerization, and aldehyde deprotection via hydrolysis of acetals. The effects of the monomer ratio and the HRP and H2O2 composites on the properties of poly(p‐hydroxybenzaldehyde‐co‐p‐phenolsulfonate) [poly(HBA‐co‐PS)] were investigated by the determination of the shrink temperature (Ts) of tanned leather. The poly(HBA‐co‐PS) structure was characterized by Fourier transform infrared spectroscopy, NMR, UV spectroscopy, and gel permeation chromatography. The mechanism of enzymatic copolymerization, including initiation, H transfer, radical transfer, coupling, termination, differed from that of traditional free‐radical polymerization. A remarkable characteristic was that poly(HBA‐co‐PS) had a large conjugated structure in its molecules that markedly improved the activity of the aldehyde and hydroxyl groups and showed easy crosslinking in the leather fibers. The applied results showed that the Ts of tanned leather with poly(HBA‐co‐PS) reached 83.6°C. Poly(HBA‐co‐PS) could be used as agent for tanning leather. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2013

Study on Structure and Tanning Properties of Copolymer of Resorcinol and 3,5-Dihydroxyl Benzoic Acid

The radical copolymerization of resorcinol (RSC) and 3,5-dihydroxyl benzoic (DHBA) was carried out in water by the initiator of horseradish (HRP)/H2O2. It was discussed that the effects of monomer composition on the properties of the copolymer. The best monomer mass ratio of RSC:DHBA was 60:40 and the shrink temperature can reached to 88.5oC. The tanning result indicated that the copolymer of RSC and DHPA has particularly excellent tanning properties and can be served as leather tannage substitute for chrome tanning materials. And also the mechanism of the HRP initiated copolymerization was proposed. The structure and molecular weight of the copolymer was characterized by Fourier Transform Infrared spectroscopy (FTIR), Nuclear Magnetic Resonance (NMR) and Gel Permeation Chromatography (GPC). The copolymer can be as tannage and retannage in making leather process. The results showed that it has excellent tanning properties and retanning effects.

Study on Tanning Properties of Modified Tannic Acid with Sulfanilic Acid Using Horseradish Peroxidase

Tannic acid (TA) was modified by sulfanilic acid (SAA) using HRP catalysis in aqueous phase. The structure of modified TA was characterized by FTIR. The tanning properties of modified TA have been studied by the tanning test together with aluminum and chrome tannages. The tanning results show that the modified TA is suitable for use as pretannage and in combinaton with chrome and aluminum tannage. The shrink temperature (Ts) of leather tanned using 6% modified TA and 2% chrome tannage can reach to 92.0 oC by the modified TA and and chrome tannage by sequential step. The applied leather has merits of good uniformity, fullness, softness and fine grain. With this method, the dosage of chrome tannage is lessened and environment pollution is alleviated.

Study on Modified Starch by Glutaraldehyde and its Properties and Application

The modified starch was prepared by degradation starch with glutaraldehyde. The process conditions of degradation and modification starch were investigation. The result shows that the degradation starch was obtained through 22.5 g cornstarch and 1g ammonium persulfate (APS) in 127.5 g water at 95°C for 1h, and the modified starch was obtained by aldolization reaction of degradation starch and 4 mol/AGU glutaraldehyde at 85°C for 5h. The modified starch can be used as leather tannage. The shrink temperature (Ts) of tanned leather can be increase from 41.6 °C to 85.2°C. It may replace chrome tannage and decrease the pollution produced in chrome tanning processing. Meanwhile, the chemistry structure of modified starch was characterized by FTIR, 1H-NMR, 13C-NMR

Study on Modified Starch by Glutaraldehyde and its Properties and Application

The modified starch was prepared by degradation starch with glutaraldehyde. The process conditions of degradation and modification starch were investigation. The result shows that the degradation starch was obtained through 22.5 g cornstarch and 1g ammonium persulfate (APS) in 127.5 g water at 95°C for 1h, and the modified starch was obtained by aldolization reaction of degradation starch and 4 mol/AGU glutaraldehyde at 85°C for 5h. The modified starch can be used as leather tannage. The shrink temperature (Ts) of tanned leather can be increase from 41.6 °C to 85.2°C. It may replace chrome tannage and decrease the pollution produced in chrome tanning processing. Meanwhile, the chemistry structure of modified starch was characterized by FTIR, 1H-NMR, 13C-NMR

Modification of fish skin collagen film and absorption property of tannic acid.

Fish collagen is a biomacromolecule material and is usually used as a clarifying agent. However, fish collagen is not recyclable, and sedimentation usually occurs in the clarification process using fish collagen so that the filtration process is inevitable. This work aimed to provide a recyclable modified fish skin collagen film (MFCF) for adsorption of tannic acids. The collagen from channel catfish skin was extracted and used for preparation of the fish skin collagen film (FCF) and MFCF. The result indicated that the mechanical properties of MFCF were improved by addition of 2ml/L glycerol, 6ml/L polyvinyl alcohol (PVA) and 2ml/L glutaraldehyde in 15g/L collagen solution. As the most important property of adsorption material, the hydroscopicity of MFCF was only 54%, significantly lower than that of FCF (295%). Therefore, MFCF would not collapse in water. The infrared and thermal properties of MFCF were also investigated in this work. Results indicated that, in comparison to FCF, the physical and chemical properties of MFCF had been improved significantly. MFCF had higher shrink temperature (79.3°C) and it did not collapse in distilled water at normal temperature. Furthermore, absorption and desorption properties of tannic acid were studied. MFCF showed good capability of absorption and desorption of tannic acid, which leaded to the suggestion that MFCF could have potential applications in adsorption material.

Preparation and Properties of Modified Starch Tannage

Modified starch tannage was synthesized by two steps. First step, a graft starch was synthesized by graft copolymerization of degraded starch with p-aminobenzene sulfonic acid and nekal using horseradish peroxidase (HRP)/H2O2 catalyze system. The effects of system pH, reaction temperature and amount of HRP on the graft efficient (GE) and graft percent (GP) were investigated and the maximum GE and GP of modified starch were obtained using 4 mg HRP/2.24 g H2O2 as catalyst at 35 for 3h under pH 7. The second step, the graft starch was oxidized by periodic acid to prepare modified starch tannage with dial dehyde.The effect of periodic acid on aldehyde groups content of graft starch was studied and it was found that the maximum content was at periodic acid concentration of 4 mol/L. The structure of modified starch tannage was characterized by FTIR, NMR and GPC. The shrink temperature (Ts)of tanned leather is 80.6 °C and the retanned leather has distinctive style of softness and flexibility.

Tailoring the Properties of Cholecyst-Derived Extracellular Matrix Using Carbodiimide Cross-Linking

Modulation of properties of extracellular matrix (ECM) based scaffolds is key for their application in the clinical setting. In the present study, cross-linking was used as a tool for tailoring the properties of cholecyst-derived extracellular matrix (CEM). CEM was cross-linked with varying cross-linking concentrations of N,N-(3-dimethyl aminopropyl)-N′-ethyl carbodiimide (EDC) in the presence of N-hydroxysuccinimide (NHS). Shrink temperature measurements and ATR–FT-IR spectra were used to determine the degree of cross-linking. The effect of cross-linking on degradation was tested using the collagenase assay. Uniaxial tensile properties and the ability to support fibroblasts were also evaluated as a function of cross-linking. Shrink temperature increased from 59°C for non-cross-linked CEM to 78°C for the highest EDC cross-linking concentration, while IR peak area ratios for the free –NH2 group at 3290 cm−1 to that of the amide I band at 1635 cm−1 decreased with increasing EDC cross-linking concentration. Collagenase assay demonstrated that degradation rates for CEM can be tailored. EDC concentrations 0 to 0.0033 mmol/mg CEM were the cross-linking concentration range in which CEM showed varied susceptibility to collagenase degradation. Furthermore, cross-linking concentrations up to 0.1 mmol EDC/mg CEM did not have statistically significant effect on the uniaxial tensile strength, as well as morphology, viability and proliferation of fibroblasts on CEM. In conclusion, the degradation rates of CEM can be tailored using EDC-cross-linking, while maintaining the mechanical properties and the ability of CEM to support cells.

Amine Functionalization of Cholecyst-Derived Extracellular Matrix with Generation 1 PAMAM Dendrimer

A method to functionalize cholecyst-derived extracellular matrix (CEM) with free amine groups was established in an attempt to improve its potential for tethering of bioactive molecules. CEM was incorporated with Generation-1 polyamidoamine (G1 PAMAM) dendrimer by using N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide and N-hydroxysuccinimide cross-linking system. The nature of incorporation of PAMAM dendrimer was evaluated using shrink temperature measurements, Fourier transform infrared (FTIR) assessment, ninhydrin assay, and swellability. The effects of PAMAM incorporation on mechanical and degradation properties of CEM were evaluated using a uniaxial mechanical test and collagenase degradation assay, respectively. Ninhydrin assay and FTIR assessment confirmed the presence of increasing free amine groups with increasing quantity of PAMAM in dendrimer-incorporated CEM (DENCEM) scaffolds. The amount of dendrimer used was found to be critical in controlling scaffold degradation, shrink temperature, and free amine content. Cell culture studies showed that fibroblasts seeded on DENCEM maintained their metabolic activity and ability to proliferate in vitro. In addition, fluorescence cell staining and scanning electron microscopy analysis of cell-seeded DENCEM showed preservation of normal fibroblast morphology and phenotype.

A Reworkable Adhesive-Free Interconnection Technology for Microfluidic Systems

In this paper, we present a simple adhesive-free interconnect technology for microfluidic systems. Reliable connection between microfluidic devices and macroscopic world is a critical issue in many lab-on-a-chip applications. In such interconnections, it is particularly advantageous to avoid liquid adhesives (e.g., epoxy, silicone, etc.) since they can create reliability (blockage or leakage) and reproducibility problems. Our adhesive-free interconnection technology is based on a micromachined silicon flange which is connected to a medical-grade silastic tube using a heat shrink tubing sleeve. The silicon part was fabricated by consecutive anisotropic and isotropic etching processes resulting in a through-hole surrounded by a connection socket ring created using the well known lag effect of deep reactive ion etching. Biocompatible polyolefin heat shrink tubing (expansion ratio of 2:1 at its shrink temperature of 143/spl deg/C) was used to connect and tightly seal the silicon flange to the silastic tube without application of any adhesive. A two-step heat treatment starting from the silicon flange and terminating at the silastic tubing was used to seal the connection. High temperature removability of the heat shrink tubing makes interconnects reworkable. Pull-out force was measured to test the mechanical strength of interconnects with different socket shapes (square, hexagon, octagon, and 32-side circle). Increasing the number of sides improves the mechanical strength with the circular interconnects having an average pull-out force of more than 3N. Leakage tests were also performed to characterize the seal quality. The circular connectors of two different flange sizes showed zero leakage up to the maximum test pressure of 200 kPa (29 psi).

Triglycidylamine Crosslinking of Porcine Aortic Valve Cusps or Bovine Pericardium Results in Improved Biocompatibility, Biomechanics, and Calcification Resistance: Chemical and Biological Mechanisms

We investigated a novel polyepoxide crosslinker that was hypothesized to confer both material stabilization and calcification resistance when used to prepare bioprosthetic heart valves. Triglycidylamine (TGA) was synthesized via reacting epichlorhydrin and NH(3). TGA was used to crosslink porcine aortic cusps, bovine pericardium, and type I collagen. Control materials were crosslinked with glutaraldehyde (Glut). TGA-pretreated materials had shrink temperatures comparable to Glut fixation. However, TGA crosslinking conferred significantly greater collagenase resistance than Glut pretreatment, and significantly improved biomechanical compliance. Sheep aortic valve interstitial cells grown on TGA-pretreated collagen did not calcify, whereas sheep aortic valve interstitial cells grown on control substrates calcified extensively. Rat subdermal implants (porcine aortic cusps/bovine pericardium) pretreated with TGA demonstrated significantly less calcification than Glut pretreated implants. Investigations of extracellular matrix proteins associated with calcification, matrix metalloproteinases (MMPs) 2 and 9, tenascin-C, and osteopontin, revealed that MMP-9 and tenascin-C demonstrated reduced expression both in vitro and in vivo with TGA crosslinking compared to controls, whereas osteopontin and MMP-2 expression were not affected. TGA pretreatment of heterograft biomaterials results in improved stability compared to Glut, confers biomechanical properties superior to Glut crosslinking, and demonstrates significant calcification resistance.

Thermal and shrinkage behaviour of stretched peroxide-crosslinked high-density polyethylene

The thermal shrinkage of stretched crosslinked high-density polyethylene (HDPE) was investigated with the aim to produce heat shrinkable materials. The heat shrinkable property was achieved by a process of heating–stretching–cooling by aid of tensile machine on crosslinked HDPE obtained by compounding with various amount of peroxide. Effect of stretching ratio and stretching temperature on thermal and shrinkage behaviour at varying peroxide contents was investigated. The results showed that crosslinking hindered the crystallization process by decreasing the melting and crystallization temperatures as well as the total degree of crystallinity. The stretching ratio had no significant effect on shrink temperature but rather on ultimate shrinkage. The stretching temperature had relatively significant influence on the shrink temperature. Crosslinked HDPE stretched at above melting point (140 °C) had higher shrink temperature as compared to those stretched at lower temperature (90 °C). These effects could be reasonably explained by Hoffman theory and changes in crystallites size and total amount of crystallinity.