Rattachat Mongkolnavin

Improvement of early cell adhesion on Thai silk fibroin surface by low energy plasma.

Low energy plasma has been introduced to treat the surface of Thai silk fibroin which should be enhanced for cell adhesion due to its native hydrophobic surface. Plasma surface treatment could introduce desirable hydrophilic functionalities on the surface without using any chemicals. In this work, nitrogen glow discharge plasma was generated by a low energy AC50Hz power supply system. The plasma operating conditions were optimized to reach the highest nitrogen active species by using optical emission spectroscopy. X-ray photoelectron spectroscopy (XPS) revealed that amine, hydroxyl, ether, and carboxyl groups were induced on Thai silk fibroin surface after plasma treatment. The results on Fourier transform infrared attenuated total reflection (FTIR-ATR) spectroscopy confirmed that the plasma treated effects were only on the outermost layer since there was no change in the bulk chemistry. The surface topography was insignificantly changed from the detection with atomic force microscopy (AFM). The plasma-treated effects were the improved surface wettability and cell adhesion. After a 90-s treatment, the water contact angle was at 20°, while the untreated surface was at 70°. The early cell adhesion of L929 mouse fibroblast was accelerated. L929 cells only took 3h to reach 100% cell adhesion on 90 s N2 plasma-treated surface, while there was less than 50% cell adhesion on the untreated Thai silk fibroin surface after 6h of culture. The cell adhesion results were in agreement with the cytoskeleton development. L929 F-actin was more evident on 90 s N2 plasma-treated surface than others. It could be concluded that a lower energy AC50Hz plasma system enhanced early L929 mouse fibroblast adhesion on Thai silk fibroin surface without any significant change in surface topography and bulk chemistry.

The effects of pulsed inductively coupled plasma (PICP) on physical properties and biocompatibility of crosslinked gelatin films.

In this work, pulsed inductively coupled plasma (PICP) device is introduced to treat crosslinked gelatin film. The effects of plasma on the properties of gelatin film were investigated. Type A gelatin film crosslinked by dehydrothermal process was treated by PICP. The properties of crosslinked gelatin were characterized by differential scanning calorimetry (DSC), amino acid content assay (TNBS), contact angle measurement and atomic force microscopy (AFM). The results showed that pulsed inductively coupled plasma did not significantly affect the thermal behavior and the degree of crosslinking of crosslinked gelatin film. The contact angle by both water and ethylene glycol of crosslinked gelatin films treated with nitrogen plasma was decreased in comparison with untreated film. The surface energy was slightly increased when increasing number of repeated discharges were applied from 1 to 20 times. This implied that nitrogen plasma could improve hydrophilicity of the crosslinked gelatin surface. The result from AFM revealed that surface roughness of crosslinked gelatin film was introduced when PICP treatment was applied. In vitro test using L929 mouse fibroblast revealed that, the number of cells proliferated on PICP-treated samples was higher than that on untreated samples. The results indicated that PICP is a potential method for crosslinked gelatin surface modification for future tissue engineering applications.

Comparison of the behavior of fibroblast and bone marrow-derived mesenchymal stem cell on nitrogen plasma-treated gelatin films.

The attachment and growth behavior of mouse fibroblast (L929) and rat bone marrow-derived mesenchymal stem cell (MSC) on nitrogen plasma-treated and untreated gelatin films was investigated and compared. The gelatin films were prepared by solution casting (0.05% w/v) and crosslinked using dehydrothermal treatment. The crosslinked gelatin films were treated with nitrogen alternating current (AC) 50 Hz plasma systems at various treatment time. The results on the attachment and growth of two cells; L929 and MSC, on plasma-treated gelatin film showed that the number of attached and proliferated cells on plasma-treated gelatin films was significantly increased compared to untreated samples. However, no significant difference between the number of attached L929 and MSC on plasma-treated gelatin was observed. The shorter population doubling time and higher growth rate of cells cultured on plasma-treated film indicated the greater growth of cells, compared to ones on untreated films. The greatest enhancement of cell attachment and growth were noticed when the film was treated with nitrogen plasma for 9 to 15s. This suggested that the greater attachment and growth of both cells on gelatin films resulted from the change of surface properties, i.e. hydrophilicity, surface energy, and chemistry. The suitable water contact angle and oxygen/nitrogen ratio (O/N) of gelatin film for best L929 and MSC attachment were observed at 27-32° and 1.4, respectively. These conditions also provided the best proliferation of cells on plasma-treated gelatin films.

Plasma Enhancement of In Vitro Attachment of Rat Bone-Marrow-Derived Stem Cells on Cross-Linked Gelatin Films

Abstract In this work, nitrogen, oxygen and air glow discharges powered by 50 Hz AC power supply are used for the treatment of type-A gelatin film cross-linked by a dehydrothermal (DHT) process. The properties of cross-linked gelatin were characterized by contact angle measurement, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) analysis. The results showed that the water contact angle of gelatin films decrease with increasing plasma treatment time. The treatment of nitrogen, oxygen and air plasma up to 30 s had no effects on the surface roughness of the gelatin film as revealed by AFM results. The XPS analysis showed that the N-containing functional groups generated by nitrogen and air plasma, and O-containing functional groups generated by oxygen and air plasmas were incorporated onto the film surface, the functional groups were found to increase with increasing treatment time. An in vitro test using rat bone-marrow-mesenchym-derived stem cells (MSCs) revealed that the number of cells attached on plasma-treated gelatin films was significantly increased compared to untreated samples. The best enhancement of cell attachment was noticed when the film was treated with nitrogen plasma for 15–30 s, oxygen plasma for 3 s, and air plasma for 9 s. In addition, among the three types of plasmas used, nitrogen plasma treatment gave the best MSCs attachment on the gelatin surface. The results suggest that a type-A gelatin film with water contact angle of 27–28° and an O/N ratio of 1.4 is most suitable for MSCs attachment.

The Effects of Pulse Inductively Coupled Plasma on the Properties of Gelatin

Plasma treatment is a technique that can be used to modify the surface of materials. It has been widely used in applications such as surface cleaning, activation, etching, and coating. In this work, pulse inductively coupled plasma (PICP) device is introduced for treatment of crosslinked gelatin film. The effects of plasma on the properties of gelatin film were investigated. Type A gelatin film crosslinked by dehydrothermal (DHT) was treated by N2 plasma. PICP device produces plasma by discharging large electrical current around a cylindrical quartz tube. The operating pressure of N2 was 5 Pa and the number of pulse applied was varied from 1 to 10 pulses. The surface properties of crosslinked gelatin were characterized by water contact angle and atomic force microscopy (AFM). The preliminary results showed that, the water contact angle of crosslinked gelatin treated by N2 plasma were decreased compared to untreated crosslinked gelatin film. This implied that, N2 plasma could introduce hydrophilic groups onto the surface of crosslinked gelatin. The result from AFM revealed that, enhanced surface roughness of crosslinked gelatin film when much number of pulses applied. In vitro test using L929 mouse fibroblast revealed that, the number of cells adhere and proliferate on plasma-treated samples was higher than that on untreated samples. The results implied that PICP has a high potential to modify the surface of gelatin for greater cell affinity.

Alkaline Stability of Polyaniline Synthesized Using Pulsed Inductively Coupled Plasma Device

The stability of polyaniline synthesized using pulsed inductively coupled plasma device was studied in alkaline media. Polyaniline was exposed to potassium hydroxide at 25°C and 90°C for various time intervals up to 4 months. An increase in %mass loss, the decreases in the absorbance intensities of polyaniline characteristic bands in FT-IR and UV-Visible spectra and the reduction of the conductivity with increasing exposure time to alkaline solution and/or temperature indicated the increases in the conversion of polyaniline into its base form and the degradation of its structure. The results also suggested that the temperature was the main factor affecting its conductivity in alkaline stability since exposing at 25°C and 90°C caused the conductivity to decrease from 4.53x10-8 S.cm-1 to 1.74x10-8 S.cm-1 and 8.15x10-9 S.cm-1 in 4 months, respectively. Therefore, this polyaniline synthesized via this system may be suitable for the applications at room temperature where alkaline stability is needed.

Cost-Effective Plasma Experiments for Developing Countries

Plasma technology forms the backbone of many modern industries today in the field of electronics, agriculture, medicine as well as environmental remediation sectors. However, plasma systems for industrial applications can be expensive to set up with the need for ultralow pressure operation and sophisticated power sources. With the goal of developing cost-effective plasma devices for industrial purposes, we present the development of plasma devices and their applications undertaken in selected small laboratories among the AAAPT fraternity. These include the 50 Hz AC glow discharge to treat biomedical materials (Chulalongkorn University, Thailand); dielectric barrier discharge for treating polymer surfaces and as a chemical reactor (Kathmandu University, Nepal); nonequilibrium atmospheric pressure plasma jets for bacterial inactivation and killing of malignant cells as well as nanoparticles synthesis (University of Malaya, Malaysia); and pulsed plasma sources (small vacuum spark as EUV and X-ray source, nanoparticles synthesis via wire explosion method) (University of Malaya, Malaysia).

Basic Concepts in Plasma Technology

Some of the fundamental basic concepts useful for the understanding of plasma will be introduced and explained in this chapter. These include particle collision and the fundamental processes that may occur as a consequence of collision between particles, the concept of Debye shielding, plasma sheath formation at the surface of object placed inside plasma, particle oscillation. The criteria of plasma and the particle transport due to electric and magnetic fields as well as density gradient will be discussed briefly.

Some Examples of Small Plasma Devices

In this chapter, the principle of operation, experimental setup as well as some results obtained from research work carried out by the authors and collaborators based on several small plasma devices will be discussed briefly.

Methods of Plasma Generation

In this chapter, the generation of plasma by gaseous electrical discharge will be discussed. Townsend Theory of electrical breakdown of gases will be explained. Various types of discharge, including to corona discharge, glow discharge and arc discharge and the characteristics of the plasmas produced will be introduced. The electrical power sources used for the generation of these plasma including DC, AC, RF, microwave and pulsed capacitor discharge are introduced.