Ging-Ho Hsiue

Zwitterionic Sulfobetaine-Grafted Poly(vinylidene fluoride) Membrane with Highly Effective Blood Compatibility via Atmospheric Plasma-Induced Surface Copolymerization

Development of nonfouling membranes to prevent nonspecific protein adsorption and platelet adhesion is critical for many biomedical applications. It is always a challenge to control the surface graft copolymerization of a highly polar monomer from the highly hydrophobic surface of a fluoropolymer membrane. In this work, the blood compatibility of poly(vinylidene fluoride) (PVDF) membranes with surface-grafted electrically neutral zwitterionic poly(sulfobetaine methacrylate) (PSBMA), from atmospheric plasma-induced surface copolymerization, was studied. The effect of surface composition and graft morphology, electrical neutrality, hydrophilicity and hydration capability on blood compatibility of the membranes were determined. Blood compatibility of the zwitterionic PVDF membranes was systematically evaluated by plasma protein adsorption, platelet adhesion, plasma-clotting time, and blood cell hemolysis. It was found that the nonfouling nature and hydration capability of grafted PSBMA polymers can be effectively controlled by regulating the grafting coverage and charge balance of the PSBMA layer on the PVDF membrane surface. Even a slight charge bias in the grafted zwitterionic PSBMA layer can induce electrostatic interactions between proteins and the membrane surfaces, leading to surface protein adsorption, platelet activation, plasma clotting and blood cell hemolysis. Thus, the optimized PSBMA surface graft layer in overall charge neutrality has a high hydration capability and the best antifouling, anticoagulant, and antihemolytic activities when comes into contact with human blood.

Phosphorus-containing epoxy for flame retardant. III: Using phosphorylated diamines as curing agents

Two phosphorus-containing diamine compounds, bis(4-aminophenoxy)-phenyl phosphine oxide and bis(3-aminophenyl)phenyl phosphine oxide, were synthesized for use as curing agents of epoxy resins. Phosphorylated epoxy resins were obtained by curing Epon 828 and Eponex 1510 with these two diamine agents. For raising the phosphorus contents of the resulting epoxy resins, the phosphorus-containing epoxy, bis(glycidyloxy)phenyl phosphine oxide (BGPPO), was also used. These two diamine agents showed similar reactivity toward epoxies. Their reactivities were higher than DDS and lower than DDM. High char yields in TGA evaluation were found for all the phosphorylated epoxy resins, implying their high flame retardancy. The excellent flame-retardant properties of these phosphorylated epoxy resins were also demonstrated by the high limiting oxygen index (LOI) values of 33 to 51.

Phosphorus-containing epoxy resins for flame retardancy V: synergistic effect of phosphorus-silicon on flame retardancy

Epoxy resins containing phosphorus and/or silicon are prepared from phosphorus/silicon-containing epoxides and diamine curing agents. The flame-retardant properties of the phosphorus/silicon-containing epoxy were studied. Furthermore, the phosphorus–silicon synergistic effect on LOI enhancement and increasing flame retardancy of the epoxy materials were demonstrated. While under flame, phosphorus provides the tendency of char formation, and silicon provides the enhancement on thermal stability of the char, to show their individual benefit on flame retardancy. Introducing both phosphorus and silicon together in the epoxy resin composition brings the success of combining these two factors in a flame retardation mechanism. An LOI enhancement from 26 to 36 is observed for epoxy resins containing both phosphorus and silicon. Moreover, the synergistic effect of phosphorus–silicon on fire resistance can be further leveled up by using siloxane reagents to replace silanes. Epoxy resins with a composition of phosphorus epoxides and siloxane diamines exhibit a high LOI value of 41, to demonstrate the high synergistic efficiency of phosphorus and silicon on flame retardation.

Plasma-induced grafted polymerization of acrylic acid and subsequent grafting of collagen onto polymer film as biomaterials

Polyacrylic acid (pAA) was introduced onto Ar-plasma treatment silicone rubber (SR) membrane surfaces by plasma-induced grafted polymerization. Collagen (type III) was also linked with the carboxylic group of pAA grafted onto the SR surface via a carbodiimine agent to obtain a secondary structure of SR. The SR surface properties were characterized by ATR-FTIR, ESCA, contact angle, and SEM. The biocompatibility of the SR surface was evaluated by a culture of cornea epithelial (CE) cells. Subsequently, 75-450 micrograms cm-2 of pAA were obtained on the SR surfaces under different reactive conditions; 3-12 micrograms cm-2 of collagen were linked on modified surfaces of SR. Moreover, ATR-FTIR and ESCA were utilized to confirm the proceedings of these reactions. The hydrophility of the modified SR was measured by a contact angle meter. The values of contact angle for SR grafted with pAA were approximately 45-50 degrees; a 50-55 degrees contact angle on pAA-g-SR to be further linked with collagen was subsequently obtained. Moreover, the influence of surface properties toward migration, growth and attachment of CE cells on the modified surfaces was also examined. Here, untreated SR was used as a control. Experimental results indicated that the number of CE cells attached onto the controlled SR was negligible. The attachment of cells onto pAA-grafted surfaces was clearly observed and peusopoda occurred; however, cell growth was depressed. This depression may have been caused by the acid environment of the pAA-grafted membrane. Nevertheless, both cell attachment and growth onto collagen-linked surfaces were significant. In addition, the morphology of the cells attached onto this surface was considered normal for primary cells. Collagen introduced on the SR surface was not denatured, i.e the natural properties of collagen were maintained. The results obtained in this study will hopefully lead to the successful development of modified SR for clinical applications.

Phosphorus-containing epoxy for flame retardant. I. Synthesis, thermal, and flame-retardant properties

A new phosphorus-containing oxirane, bis-(3-glycidyloxy)phenylphosphine oxide (BGPPO), was synthesized. Further curing BGPPO with diamine curing agents, dicyanodiamide (DICY), 4,4′-diaminodiphenylmethane (DDM), and 4,4′-diaminodiphenylsulfone (DDS), respectively, resulted in several phosphorylated epoxy resins. Compared with Epon 828, Eponex 1015, and DER 732, BGPPO showed relatively high reactivity toward diamine agents via DSC studies. Furthermore, the reactivity of the three curing agents toward BGPPO were found to be in the order of DDM > DICY > DDS. Thermal stability and the weight loss behavior of the cured polymers were studied by TGA. The phosphorylated resins showed lower weight loss temperatures and higher char yields than did the Epon 828-based resins. The high char yields as well as high limited oxygen index (LOI) values of the BGPPO-based resins confirmed the effectiveness of phosphorus-containing epoxy resins as flame retardants.

Microstructural and morphological characteristics of PS–SiO2 nanocomposites

Abstract A series of organic–inorganic hybrid materials have been prepared by copolymerizing styrene and alkoxysilane-methacrylate via the sol–gel process. The alkoxysilane-containing copolymer precursors were synthesized by free-radical copolymerization of styrene with an alkoxysilane-containing monomer, methacrylic acid 3-(trimethoxysilyl)propyl ester (MAMSE), at several feeds. The copolymer precursors were then hydrolyzed and condensed to generate PS–SiO 2 hybrid sol–gel materials. The hybrid copolymers possess excellent optical transparency and a nanoscale microphase separation. The copolymer precursors and their hybrid copolymers were characterized by FT-IR spectra, 1 H NMR spectra, DSC, and TGA thermograms. Chemical structural effect on the morphology and thermal properties was investigated with SEM, mapping photographs, and high-resolution solid state 13 C and 29 Si NMR spectra. It was found that compatibility between copolymer and silica mainly comes from incorporating the polymer with silica covalently. Moreover, MAMSE could be hydrolyzed to methacrylic acid and ester-interchanged to silyl methacrylate during heat treatment. This also enhances the compatibility between the copolymer and silica. The thermal properties of the PS–SiO 2 hybrid copolymers are improved as silica content increase. However, the presence of silyl ester groups, which were formed during heat treatment, would reduce the thermal stability of the hybrid copolymers.

Preparation of controlled release ophthalmic drops, for glaucoma therapy using thermosensitive poly-N-isopropylacrylamide.

In this study, controlled release ophthalmic agents for glaucoma therapy were developed based on the thermosensitivity of poly-N-isopropylacrylamide (PNIPAAm). The clear solution of PNIPAAm was known to undergo phase transition when the temperature was raised from the room temperature to about 32 degrees C. The drug was entrapped in the tangled polymer chains or encapsulated within the crosslinked polymer hydrogel at room temperature, and released progressively after topical application (i.e., at a higher temperature). Linear PNIPAAm and crosslinked PNIAAm nanoparticles containing epinephrine were prepared. The drug release rate and cytotoxicity were investigated in vitro. Ophthalmic formulations based on either linear PNIPAAm or the mixture of linear PNIPAAm and crosslinked PNIPAAm nanoparticles were administered to rabbits and the intraocular pressure (IOP)-lowering effect was evaluated. The decreased pressure response of the formulation based on linear PNIPAAm lasted six-fold longer than that of the conventional eye drop. Furthermore, for formulation based on the mixture of linear PNIPAAm and crosslinked nanoparticles, the pressure-lowering effect lasted eight times longer. These results suggest the use of thermosensitive polymer solutions or hydrogels is potential in controlled release antiglaucoma ophthalmic drugs.

Synthesis, characterization, thermal, and flame retardant properties of phosphate-based epoxy resins

A new phosphorus-containing oxirane bis-glycidyl phenylphosphate (BGPP), and a diamine, bis(4-aminophenyl)phenylphosphate (BAPP), were synthesized. Both of these two phosphorus-containing compounds lead to phosphate-containing epoxy resin via curing reaction. The kinetics of the curing reaction of BGPP with various curing agents, including BAPP, were studied. The introduction of electron-withdrawing group into the compounds increases the BGPP and decreases the BAPP reactivity in the curing reaction. The thermal and the weight loss behavior of the cured epoxy resins were studied by TGA. High char yields (32–52%) as well as high limiting oxygen index (LOI) values (34–49) of these phosphorylated resins were found, confirming the usefulness of these phosphorus-containing epoxy resins as flame retardants.

Tissue-Engineered Human Corneal Endothelial Cell Sheet Transplantation in a Rabbit Model Using Functional Biomaterials

Background. This study was performed to investigate whether transplantation of bioengineered human corneal endothelial cell (HCEC) sheet grafts into corneas denuded of endothelium could restore corneal function and clarity in a rabbit model. Methods. After being labeled with PKH26 fluorescent dye, the adult HCECs derived from eye bank corneas were cultivated on the thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm)-grafted surfaces for 3 weeks at 37°C, and were harvested as transplantable cell sheets after incubation for 45 min at 20°C. Attached by gelatin hydrogel discs, the bioengineered cell monolayers were transplanted to rabbit corneas denuded of endothelium (HCEC sheet group). Traumatized rabbit corneas were served as controls. Postsurgical corneas underwent clinical observations and histological examinations for 6 months. Results. By transmission electron microscopy and Western blot analysis of zonula occludens-1 and Na+,K+-adenosine triphosphatase proteins, the structure and function of HCEC sheets resembled those of native corneal endothelium. After endothelial cells were removed, corneas of each group turned severe edematous and opaque. In the HCEC sheet groups, corneal clarity was gradually restored and corneal thickness was significantly less than that in the control groups (P<0.05). The attached PKH26-positive HCECs spread on rabbit Descemet’s membrane after receiving cell sheet grafts. Intraocular delivery of HCEC sheets by means of a minimally invasive technique (i.e., small-incision surgery using biodegradable hydrogels) demonstrated long-term graft integration with damaged corneas. Conclusions. These results indicate that using cultured HCECs and functional biomaterials, PNIPAAm and gelatin, an effective cell sheet-based therapy can be developed for the treatment of corneal endothelium deficiency.

Phosphorus-containing epoxy for flame retardance: IV. Kinetics and mechanism of thermal degradation

Abstract The kinetics and mechanisms of thermal degradation of a phosphorus-containing epoxy based on bis-(3-glycidyloxy)phenylphosphine oxide (BGPPO) and 4,4′-diaminodiphenylsulfone (DDS) were studied. Two and four stages were found for BGPPO/DDS degradation in nitrogen and air, respectively. The degradation activation energies calculated from the methods of Kissinger, Friedman and Ozawa were obtained. The first stage of degradation, which results from the decomposition of phosphorous groups, showed lower activation energy than the other stages. Furthermore, via FTIR and TG-FTIR investigations, the degradation of this phosphorus-containing epoxy was determined to begin by the breaking of PPh bonds, followed by dehydration reactions breaking POC bonds, and elimination of propyl groups. Therefore, the degradation of the epoxy resulted in high char yields and residues with high phosphorus contents.