Shih Peng Wen

Preparation and Evaulation of Degradable Poly(lactic acid) Composite Dressings

Chitosan and sodium alginate are two prominent biomaterials because they have some unique properties such as good biocompatible and biodegradable. In this study, sodium alginate was as swelling and moisture retention layer; Chitosan was antibacterial layer.Polylactic acid (PLA) blended in different weight ratios with low melting point polylactic acid (LMPLA) to fabricate nonwoven fabric which reinforced by needle punching and hot pressing. Afterward, chitosan/ sodium alginate compound solution were treated by UV light in order to form cross-linking. Then chitosan/ sodium alginate compound solution coated on the PLA nonwoven fabric to make PLA composite dressings. The mechanical properties of chitosan/ sodium alginate membrane and dressing were measured. The optimum parameters of chitosan/sodium alginate composite membrane was treated by UV light for five minutes and the volume ratio of chitosan (3 wt %) and sodium alginate (1 wt %) solution was 8:2. After we coated chitosan/sodium alginate solution on PLA nonwoven fabric, the Tensile strength, and tear strength were upgraded by 80 % and 98 %; its air permeability and flexibility length, however, dropped by 18 % and 60 %, respectively.

Effects of 1-Ethyl-3-(3-Dimethylaminopropyl) Carbodiimide Cross-Linking Duration on the Structure of Chitosan/Gelatin Composite Bone Scaffolds

Freeze-drying method can create three-dimensional, porous structure bone scaffolds, the pore size of which can be changed by a cross-linking agent. This study dissolves chitosan powder in a 1 v/v % acetic acid aqueous solution to form a 2 w/v% chitosan solution. The chitosan solution and a 4 w/v % gelatin aqueous solution are blended to form Chitosan/Gelatin mixture, after which the mixture is frozen at-20 °C for 1 hour, removed, and cross-linked with a 0.5 v/v % 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) solution for different durations. The cross-linked mixture is frozen at-20 °C for 1 hour and then freeze-dried for 24 hours to form Chitosan/Gelatin composite bone scaffolds. A stereomicroscope and a scanning electron microscopes (SEM) and Image Pro Plus are used to observe the surface and pore size of the bond scaffolds, and in vitro evaluates their biocompatibility. The experiment results show that resulting bone scaffolds possess a uniform pore distribution a desirable biocompatibility.

Process Technology and Mechanical Properties of Polylactic Acid Ply Yarns and 316L Stainless Steel Braids

Biodegradable polymer has been widely used in surgical suture, dressing, artificial bone and other bone-related applications. However, when compared with the human cortical bone, the pure polymer obviously did not have enough strength. The present study aimed to give preliminary insights from a pilot study of designing a scaffold of polylactic acid ply yarns composited with stainless steel (SS) braids. To evaluate the fabrication processes and alkali effects on the individual materials, the different heating temperature and alkali treating time and alkali concentration were applied to clarify the changes in mechanical strength. The experimental results showed that the strength was not significant declined with alkali and heating treatments. The retained mechanical strength was kept at 100-120 MPa and ultimately led to bone-like mechanical properties.

The Freeze-Dry Method and In Vitro Assay of Chitosan/Gelatin/Hydroxyapatite Artificial Bone Scaffolds

This study aims to create avirulent artificial bone scaffolds. Chitosan/gelatin mixture is blended with hydroxyapatite (HA) powder, followed by being processed with a free-dry method in order to form CGH artificial bone scaffolds. A stereomicroscope, an optical microscope and an MTT assay are used to evaluate the applications of the bone scaffolds. The combination of HA powders leads to isotropic pores in the bone scaffolds, while not inflicting their biocompatibility. In addition, the cell viability increases with the increasing content of HA powder. This study successfully produces biocompatible and non-toxic bone scaffolds.

Compression Behaviors of Stainless Steel Braided Coronary Stents and Polyvinyl Alcohol/Stainless Steel Braided Coronary Stents

With the appearance of reticular tubes, coronary stents can resist the compressive strength caused by vascular pulsation. This study braids stainless steel fibers with diameters of 0.12 mm and 0.08 mm with a braiding technique, and the resulting braids are then combined with polyvinyl alcohol (PVA) solution to form three stent types-S12, PVA/S12, and PVA/S8. S12 is braids that are made of 0.12-mm-diameter stainless steel fibers, PVA/S12 is S12 coated with PVA. PVA/S8 is braids made with 0.08-mm-diameter stainless steel fibers and then coated with PVA. Surface, braiding angle, and compression behavior of the coronary stents are observed by a stereomicroscope, analyzed by Motic Images Plus 2.0 software, and examined by an Instron 5566, respectively. The experiment results show that compared to S12 and PVA/S8, PVA/S12 has a smaller braiding angle, indicating its manufacturing process is not stable. Of the three coronary stents, PVA/S8 possesses the greatest recovery from the compression, and thus this study yields optimal coronary stents with satisfactory surface, braiding angle, and recovery ability.

Polylactic Acid Bone Scaffolds Made by Heat Treatment

Polylactic acid (PLA) has a widespread application, such as bone scaffolds, in biomedical field. This study creates PLA bone scaffolds, which has a structural stability, by using 150 denier (D) PLA plied yarn. 75 D PLA filaments are combined and then twisted into plied yarn. During the twisting process, the twists per inch (TPI) are varied. The resulting plied yarn undergoes heat treatment, and then is evaluated with mechanical property tests, determining an optimal TPI of 9. The plied yarn is then braided into PLA bone scaffolds. PLA bone scaffolds, thermally treated or not, are observed by a stereomicroscope and tested for porosity and tensile strength. According to test results, the optimal TPI is 9, which results from the optimal tensile strength. However, the variation in elongation of various 150 D plied yarn is not significant. When observed by a stereomicroscope, PLA bone scaffolds, which are thermally treated, have a compact filament arrangement. This is due to thermal bonding between filaments; in addition, the heat treatment duration is short, so the PLA filaments are not melted completely, resulting in a stable, hollow structure. According to porosity and tensile strength test, PLA bone scaffolds that are thermally treated exhibit a lower porosity and tensile strength due to the compact arrangement and tender phenomenon of the filaments. As a result, the optimal PLA bone scaffolds are made of 150 D plied with a TPI of 9, followed by a heat treatment at 165 °C for ten minutes.

Manufacturing Technology of 316L Stainless Steel/Poly(Lactic acid) Composite Braids and the Induction of Hydroxyapatite Formation on the Braid

Many biodegradable synthetic polymers have been used as tissue-engineered scaffolds. The major problem of these polymers to be used in bone tissue engineering is their poor mechanical strength. It is well known that we can deposit hydroxyapatite, a material with strong osteoconductivity, onto a surface using electrochemical methods. These polymers, again, lack electrical conductivity so that deposition of hydroxyapatite onto these polymers is very challenging, if not impossible. Here we presented a novel scaffold for bone tissue engineering based on textile technology. First, we fabricated 316L stainless steel/poly(lactic acid) composite ply yarn by wrapping stainless steel wires and poly(lactic acid) yarn together. A 16-spindle braiding machine was then used to braid the composite yarn layer by layer into a 3-dimensional scaffold for bone tissue engineering. Furthermore, due to the electrical conductivity of 316L stainless steel wires in the composite yarn, we employed an electrochemical method to induce hydroxyapatite deposition on the braid. SEM was used to evaluate the growth of hydroxyapatite formation on the braid.

Biodegradable Braided Coronary Stents: Effects of Cross-Linking Concentrations on Surface Structure and Compressive Strength

This study proposes coronary stents in a manner of reticular tube, which are made by applying a braiding method. Polyvinyl alcohol (PVA) plied yarns are braided into hollow braids on a 16-spindle braid machine, followed by being cross-link treated to form the coronary stents. The surface observation and a compressive test are used to evaluate the resulting products. The test results show that cross-link treatment does not pertain to the reticular, tubular manner of the braids. However, a low cross-linking concentration results in a light shade and a greater compressive strength in the coronary stents. In addition, the acidification of the cross-linking solution affects the compressive modulus. The coronary stents presented by this study are proved to be biodegradable and have compressive strength and a reticular-and-tubular form.

Braided Bone Scaffolds Made by Braiding Polyvinyl Alcohol and Cross-Linked by Glutaraldehyde: Manufacturing Process and Structure Evaluation

When the bone tissues suffer from an impaired area that is greater than their self-healing size limit, the impairment may not heal or heal incompletely. With the purpose of developing artificial bone scaffolds for the recovery of bone tissues, this study twists 3-ply polyvinyl alcohol (PVA) fibers into plied yarns, which are then braided into PVA bone scaffolds using a braiding technique. Afterward, the braids are cross-linked with glutaraldehyde in order to improve their structure and their water stability. The experiment results show that a cross-linking by glutaraldehyde does not significantly influence the surface morphology of the braids. However, a cross-linking by high concentration glutaraldehyde provides the braids with a swelling phenomenon, which in turn causes a dense internal feature of the braids, and namely a lower porosity. This study successfully prepares braided PVA bone scaffolds with water stability, through a glutaraldehyde cross-linking.

Using a Hollow Braiding Technique to Prepare 316L Stainless Steel Braids as Coronary Stents

This study proposes a novel manufacturing method, a hollow braiding technique, to make reticular tubes. Coronary stents for coronary arteries have to have a size equal to the size of the arteries, and as a result, material and diameter of stents are both critical designed parameters. By using a hollow braiding technique and a braiding machine, 316L stainless steel fibers are made into coronary stents with an internal diameter of 3 mm, which meets the requirement of coronary arteries. The experiment results show that the hollow braiding technique can effectively braid reticular tubes with an internal diameter of 3 mm. In addition, variation in tooth number on the take-up gear can influence the braiding angle but does not influence the stability of the braiding structure and metal cover rate. In this study, the hollow braiding technique successfully produces coronary stents in the form of reticular tubes with a size equal to coronary arteries.