Ko-Shao Chen

Design and evaluation of drug-loaded wound dressing having thermoresponsive, adhesive, absorptive and easy peeling properties

In order to develop a novel unique wound dressing, a combination of self-adhesive Eudragit E film with antibacterial drug-loaded poly (N-isopropyl-acrylamide) (PNIPAAm) microgel beads was designed. The result indicates that the tack property of Eudragit E film increased with an increase of the PNIPAAm microgel beads added, but there was no significant difference between the dried PNIPAAm microgel beads with or without adsorbing drug. In addition, the peel strength of Eudragit E film initially decreased with the addition of PNIPAAm microgel beads, but increased to a maximum value when PNIPAAm microgel beads were added from 4% to 7.6%. then decreased again after 7.6%. The optimal concentration of PNIPAAm microgel beads was 7.6% (w/v) which had better tack and peel adhesive properties. The water uptake ratio of Eudragit E film containing PNIPAAm microgel beads was found to be temperature-dependent, suggesting that the Eudragit E film containing PNIPAAm microgel beads enabled to absorb the wound fluid. Eudragit E film containing PNIPAAm microgel beads with or without adsorbing drug had significantly reduced peel strength after 12 h-immersion in solution. All these results suggest that a novel drug-loaded wound dressing has been developed by binding a self-adhesive Eudragit E film with an antibacterial drug-loaded PNIPAAm microgel beads to achieve thermo-responsive, adhesive, absorptive and easy peeling functions.

The antibacterial activities of hydrophilic-modified nonwoven PET

Abstract The hydrophobic surface of nonwoven PET with surface inertia has limited the practical bioapplications. In this study, nonwoven PET was activated by argon gas plasma and subsequently water-soluble monomers (acrylamide and itaconic acid) were grafted onto the PET by UV-induced surface graft polymerization. After the plasma activation and/or grafting, the hydrophobic surface of nonwoven was modified into a hydrophilic surface. To improve wound healing, the following three biocides have been used in this study: (1) AgNO3 solution complexes, (2) Vinyl quarternary ammonium salt (VQAS) and (3) chitosan. For Ag+ ion impregnation and VQAS grafting, the amount of these biocidal materials on the surface increases when the monomer concentration increases. However, for the chitosan immobilization, the chitosan amounts seemingly decrease with an increase in the chitosan concentration. For biocidal properties, the Ag+ ions produce best result. However, the VQAS grafting is most durable against the flushing water.

Organic esters of plasticizers affecting the water absorption, adhesive property, glass transition temperature and plasticizer permanence of eudragit acrylic films.

The materials used in film coating technology are very important tools for pharmaceutical applications. The effects of four organic esters used as plasticizers (triacetin, diethyl phthalate (DEP), dibutyl phthalate (DBP) and tributyl citrate (TBC)) on the water absorption behavior and adhesive property of Eudragit films and on the glass transition temperature (T(g)) and plasticizer permanence of Eudragit E film were investigated. The results indicate that the water absorption of these Eudragit films was dependent on the type of Eudragit polymers and plasticizers used. Eudragit E film plasticized with triacetin showed a slight water absorption, but when plasticized with DEP, DBP or TBC did not. All Eudragit RL films showed significant uptake of water, but Eudragit RS films exhibited a lesser degree of water absorption. The adhesion (tack value) of all Eudragit films was markedly increased when the concentration of plasticizer was greater than 25%. Eudragit E film exhibited a greater adhesiveness than the Eudragit RL or RS film, particularly with higher plasticizer concentration. Weight loss of the Eudragit E film plasticized with triacetin or DEP was more pronounced with aging, but when plasticized with DBP or TBC weight loss was not seen. The results indicate that TBC may be the best choice of plasticizer for Eudragit film, particularly for the Eudragit E film.

Humidity sensors using polyvinyl alcohol mixed with electrolytes

Abstract Resistive-type humidity sensors were fabricated by casting polyvinyl alcohol on comb-shaped electrodes. The impedance of the PVA film decreased with increasing relative humidity (RH), the best sensing behavior being attained at a film thickness of 10 μm. The addition of p-styrenesulfonate sodium (PSSD), sodium chloride or m-benzenedisulfonate disodium (MBSD) to the PVA film was effective for improving the humidity sensitivity. The PSSD-added PVA film (1/15 in molar ratio) gave the best humidity sensing performance among the films tested. With this film, the impedance measured at 1 kHz and 25°C varied by more than four orders of magnitude in the range of 15–95% RH. A post-argon plasma treatment introduced to cross-link the PVA film was found to improve not only the stability of the film at high humidity, but also the response rate and hysteresis problem without deteriorating its sensitivity.

Effects of additives on the photo-induced grafting polymerization of N-isopropylacrylamide gel onto PET film and PP nonwoven fabric surface

Abstract In this study, the thermosensitive gels were grafted onto plasma-activated polyethylene terephthalate (PET) film and polypropylene (PP) nonwoven fabric surface. The Ar* plasma pretreatment was carried out and subsequent photo-induced surface graft polymerization was employed to graft the N-isopropylacrylamide (NIPAAm). The effects of additives during the grafting were accessed. The additives used were ammonium peroxodisulfate (APS, initiator), N,N,N′,N′-tetra-methylethylene-diamine (TEMED, promoter) and N,N′-methylenebisacrylamide (NMBA, cross-linking agent). The results indicate that the additives of APS, TEMED and NMBA will be beneficial in promoting the grafting. The additives, including all three, will give the best result. These grafted gels exhibit a lower critical solution temperature (LCST) at about 32 °C, which shows that the temperature-responsive behavior of bulk P (NIPAAm) hydrogel was preserved.

Petal-like apatite formed on the surface of tricalcium phosphate ceramic after soaking in distilled water.

In the present study six types of tricalcium phosphate ceramic were prepared and soaked in distilled water for different periods to investigate whether a surface apatite layer was formed on TCP ceramics or not. X-ray diffractometry (XRD) and Fourier-transformed infrared (FTIR) spectrometer were used to examine the changes in crystalline phases and functional groups of TCP ceramics for different soaking periods. Calcium and phosphate ions released from TCP ceramics during soaking were recorded by atomic absorption analysis and ion-coupled plasma. Results revealed that alphaTCP, alphaTCP/betaTCP mixture (alphabetaTCP) and betaTCP ceramic were gradually dissolved. There was no apatite layer formed on their surface after being immersed in distilled water for different durations of time. Mg-TCP ceramic, tricalcium phosphate doped with Mg ions, exhibited a lower dissolution rate than the other types of TCP ceramics. Apatite crystals were also not formed on the surface of Mg-TCP ceramic when immersed in distilled water. Tribasic calcium phosphate, prepared from wet precipitation method, was converted to betaTCP/HAP (HbetaTCP) or alphaTCP/betaTCP/HAP (HalphabetaTCP) crystalline composition at different sintering temperatures (1,150 degrees C and 1,300 degrees C). The surface apatite layer did not appear on HbetaTCP ceramic after soaking. We observed that petal-like apatite was formed on the HalphabetaTCP ceramic surface after being immersed for 2 weeks. alphaTCP phase of HalphabetaTCP ceramic was not directly converted to apatite during soaking. The surface apatite layer formed on the HalphabetaTCP ceramic surface was due to the precipitation of the calcium and phosphate ions released from alphaTCP dissolution. HAP, which existed in the structure of HalphabetaTCP ceramic, plays a role as apatite-precipitating seed to uptake calcium and phosphate ions. TCP ceramics which lacked alphaTCP and HAP content neither converted to apatite nor formed surface apatite on their surfaces during immersion.

Preparation of a biphasic porous bioceramic by heating bovine cancellous bone with Na4P2O7 · 10H2O addition

Sintered bovine cancellous bone exhibited excellent biocompatiblity, high porosity and have an interconnecting porous structure allowing for bone ingrowth. However, the main mineral constitution of sintered bovine bone-hydroxyapatite (Ca10(PO4)6(OH)2, HAP) seems to be too stable in vivo. For improving its bioactivity, the calcined bovine bone removing the organic substance by burning process-with different quantities of sodium pyrophosphate (Na4P2O7.10H2O, NP) addition was heated to a high temperature to transform its crystalline phase constitution from HAP into TCP/HAP biphasic or other multiphasic structures. Results revealed that the calcined bovine bone without NP addition, exhibited a pure form of HAP characterized pattern during heating. Its thermal behavior was similar to stoichiometric HAP, it gradually lost its OH- ions and transformed into oxyhydroxyapatite at high temperature. After being doped into calcined bovine bone, NP would react with HAP to form betaBTCP and NaCaPO4 around 600 degrees C. At 900 degrees C, doped NP would completely react with HAP and the NaCaPO4 would further react with HAP to form more betaBTCP in the system. With NP increasing in the calcined bovine bone, HAP would gradually convert into different crystalline phase compositions of TCP/HAP, TCP/HAP/NaCaPO4 or TCP/NaCaPO4 at high temperature. By heating calcined bovine cancellouse bone with different quantities of NP we could obtain different crystalline phase compositions of natural porous bioceramic in this study.

New nerve regeneration strategy combining laminin-coated chitosan conduits and stem cell therapy

Nerve regeneration remains a difficult challenge due to the lack of safe and efficient matrix support. We designed a laminin (LN)-modified chitosan multi-walled nerve conduit combined with bone marrow stem cell (BMSC) grating to bridge a 10 mm long gap in the sciatic nerve of Sprague-Dawley rats. The repair outcome was monitored during 16 weeks after surgery. Successful grafting of LN onto the chitosan film, confirmed by immunolocalization, significantly improved cell adhesion. In vivo study showed that newly formed nerve cells covered the interior of the conduit to connect the nerve gap successfully in all groups. The rats implanted with the conduit combined with BMSCs showed the best results, in terms of nerve regrowth, muscle mass of gastrocnemius, function recovery and tract tracing. Neuroanatomical horseradish peroxidase tracer analysis of motor neurons in the lumbar spinal cord indicated that the amount and signal intensity were significantly improved. Furthermore, BMSCs suppressed neuronal cell death and promoted regeneration by suppressing the inflammatory and fibrotic response induced by chitosan after long-term implantation. In summary, this study suggests that LN-modified chitosan multi-walled nerve conduit combined with BMSCs is an efficient and safe conduit matrix for nerve regeneration.

Preparation of ?TCP/HAP biphasic ceramics with natural bone structure by heating bovine cancellous bone with the addition of (NH4)2HPO4

In this study, the calcined bovine bone (CBB)—removing the organic substance by a burning process—with addition of different quantities of ammonium phosphate [(NH4)2HPO4] (AP) was heated to a high temperature to transform its crystalline phase constitution from hydroxyapatite (HAP) into a tricalcium phosphate (TCP)/HAP biphasic structure. Results revealed that the CBB without AP appeared to be mainly composed of an HAP type pattern when heated to 1300°C. After adding doped AP to CBB, the HPO42− ions of AP condensed into P2O74− ions at temperatures of 400–600°C. P2O74− ions reacted with the OH− ions of HAP to form βTCP at temperatures up to 600°C. The conversion reaction of HAP to βTCP finished at around 900°C. With increasing AP in the CBB, HAP gradually converted into different phase compositions of TCP/HAP or TCP at high temperature. Mechanical testing results showed that there was no significant difference in sintered CBB with different quantities of AP. By heating calcined bovine cancellous bone with different quantities of AP, we obtained different crystalline phase compositions of bioceramics with a natural porous structure.

Preparation of high-temperature stabilized β-tricalcium phosphate by heating deficient hydroxyapatite with Na4P2O7.10H2O addition

In this paper, the high-temperature stabilized beta-tricalcium phosphate (betaTCP, beta-Ca3(PO4)2) were prepared by heating the deficient HAP (d-HAP, Ca10-x(HPO4)x(PO4)6-x(OH)2-x) with tetra-sodium diphosphate decahydrate (NP, Na4P2O7 x 10H2O) addition. The betaTCP, d-HAP and d-HAP doped with 2.5, 5, 7.5 and 10 wt % NP were heated to different temperatures and were investigated by X-ray diffraction analysis (XRD) and Fourier-transformed infrared spectroscopy (FTIR). The results demonstrated that the HPO4(2-) of d-HAP condensed into P2O7(4-) occurred before 650 degrees C. The P2O7(4-) ions could be traced in the FTIR spectrum when the d-HAP was heated up to 750 degrees C. The reaction of P2O7(4-) with OH- did not occur instantly but over a wide range of temperatures. The d-HAP doped with NP would decrease the decomposition temperature of d-HAP. NP doped into d-HAP not only induced the d-HAP decomposition at lower temperature but also stabilized the betaTCP crystal structure at higher-temperature. It could also increase the conversion temperature of betaTCP to alphaTCP from 1180 degrees C up to 1300 degrees C. We could successfully prepare high-temperature (up to 1300 C) stabilized ffTCP by heating NP doped d-HAP.