Chih-Chiang Weng

Assessment and Characterization of Degradation Effect for the Varied Degrees of Ultra-violet Radiation onto the Collagen-bonded Polypropylene Non-Woven Fabric Surfaces

Exposure to ultra-violet (UV)-C radiation is a frequently used method to prevent bacteria from invasion of blood-contact biomedical products. Potential damage induced by UV radiation to collagen is of concern due to the decay of bioactivity, considerably correlated with structural alterations. Our current investigation studies the collagen-bonded non-woven polypropylene (PP) fabric surface. In this experiment, antenna-coupling microwave plasma is utilized to activate PP fabric and then the sample is grafted with acrylic acid (AAc). Type III collagen is immobilized by using water soluble 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide as coupling agent. The collagen-bonded samples with sample temperature ca. 4 degrees C are then exposed to UV-254nm radiation for different time intervals. By using fourier-transformed infrared with attenuated total reflection (FTIR-ATR) and XPS (X-ray photoelectron spectroscopy), we examine the chemical structures of samples with different treatments. Coomassie brilliant blue G250 method is utilized to quantify the immobilized collagen on the PP fabric surfaces. Blood-clotting effects are evaluated by activated partial thromboplastin time, thrombin time, and fibrinogen concentration tests. By means of cell counter and scanning electron microscopy we count red blood cells and platelets adhesion in the modified porous matrix. Our experimental results have demonstrated that with pAAc-grafting of ca. 173 microg cm(-2) and immobilized collagen of 80.5+/-4.7 microg cm(-2), for human plasma incubated samples of various intervals of UV-254 nm radiation, fibrinogen concentration decreases in human plasma, while platelets and red blood cells adhesions increase before UV radiation. However, the required time for thrombination shows significant change for UV radiation exposure of less than 20 h (alpha = 0.05). The decay of bioactivity for the UV-irradiated, collagen-bonded surfaces is thus evaluated. Surface analyses indicate that the decrease of R-COOH (derivated from grafted-pAAc or de-carboxylation of collagen), amides degradation (broken-NH), and phenylalanine scission (terminated by -OH, tyrosine formation) may gradually damage collagen by increasing the intervals of UV radiation. These effects considerably influence the bioactivity of the collagen-bonded fabric. The XPS measurements of C 1s core levels at 288.4 eV (O = C-NH) and at 289.1 eV (O = C-O) illustrate significant decreases of intensity after radiation time ca. 44 h. It is clear that UV-254 nm radiation exposure for ca. 20 h has the potential impact to moderate the bioactivities of collagen and therefore act as a vital factor to accelerate biodegradation.

Capillary-tube-based micro-plasma system for disinfecting dental biofilm

Abstract Purpose: A low-temperature low-energy capillary-tube-based argon micro-plasma system was applied to disinfect Streptococcus mutans-containing biofilm. Materials and methods: The micro-plasma system uses a hollow inner electrode that is ignited by a radio-frequency power supply with a matching network. The energy content was analyzed using optical emission spectroscopy. The micro-plasma-induced effect on a biofilm cultured for 24 or 48 h with a working distance of ≈3 mm at low temperature was evaluated. The morphologies of the treated live/dead bacteria and the produced polysaccharides after micro-plasma treatment were examined. Results: Scanning electron microscopy images and staining results show that most of the S. mutans on the treated biofilm were acutely damaged within a micro-plasma treatment time of 300 s. Conclusions: The number of living bacteria underneath the treated biofilm greatly decreased with treatment time. The proposed micro-plasma system can thus disinfect S. mutans on/in biofilms.

Microcontact printing pattern as a mask for chemical etching: A scanning photoelectron microscopy study

Synchrotron-based scanning photoelectron spectromicroscopy and microspectroscopy were used to monitor the outcome of the etching process involving the transfer of a lithographic pattern produced by microcontact printing (μCP) of self-assembled monolayers (SAMs) to the underlying metal (gold) substrate. As a test system, octadecanethiolate (ODT) SAMs on gold substrates were chosen. The μCP ODT SAMs were found to protect the underlying gold against the wet-chemical etching, ensuring the effective transfer of the μCP pattern to the substrate. These SAMs exhibited only a slight degradation upon their exposure to the Au-etching solution. In contrast, a significant degradation of the edges of the printed features was observed. This degradation was predominantly related to a lateral diffusion of the active etching agents across these edges, along the SAMs-Au interface. This process can result in a blurring and narrowing of the printing features of a μCP SAM pattern at its transfer to the underlying substrate.

Patterning of alkanethiolate self-assembled monolayers by downstream microwave nitrogen plasma: Negative and positive resist behavior

Taking octadecanethiolate self-assembled monolayers (SAMs) adsorbed on Au(111) as a test system, the authors demonstrated patterning of an aliphatic monomolecular resist by downstream microwave nitrogen plasma in proximity printing geometry with a mesh mask simply placed onto the SAM surface. The behavior of the SAM resist was found to be dependent on the plasma treatment time, which is related to the dominance of different plasma-induced processes at different treatment stages. At a short treatment, the most prominent process is the activation of the SAM-ambient interface, resulting in subsequent adsorption of airborne species onto the plasma-exposed areas upon the exposure of the SAM pattern to ambient. At a long treatment, the dominant process is the chain decomposition with the subsequent desorption of the released fragments and carbonization of the residual film. Due to the above behavior, aliphatic SAMs can serve as either negative or positive monomolecular resists at either a short or long plasma t...