ICMCTF2001 Session H4-3: Novel Materials and Processes

Friday, May 4, 2001 8:30 AM in Room Sunrise

Friday Morning

Start	Invited?	Item
8:30 AM	Invited	H4-3-1 Biodegradable and Hydrophilic Polymer Thin-Films by Pulsed Laser Deposition J.D. Talton (Nanosphere/Nanocaot Technologies, Inc.) Surface modification / functionalization of biomedical devices has gained significant interest in the last decade to improve the tissue interactions and cellular response of the implant surface. Biomedical devices such as stents, catheters, tissue implants, and contact lenses could benefit significantly from improved tissue response, in addition to local delivery of anti-inflammatory/anti-thrombogenic drugs. Deposition of biodegradable polymers such as poly(L-lactic acid) (PLLA), poly(lactic-co-glycolic acid) (PLGA), and poly(ethylene glycol) (PEG), as well as nondegradable polymers such as cross-linked poly(ethylene glycol) (PEG) and poly(vinyl pyrrolidone) (PVP) have been investigated. Optimization of the process parameters using a Pulsed Laser Deposition (PLD) technique were characterized by SEM, GPC, LC/MS/MS, NMR, and FTIR. Deposition of polymer films showed improved morphological properties and higher molecular weights slightly above threshold laser energies, with increased particulate ejection and decomposition occurring at higher energies. General compositional peaks using FTIR and NMR verified deposited polymer films molecular structures and decomposition products, while GPC was used to obtain relationships between energy densities and deposited polymer molecular weight. Finally, identification of polymer and decomposition products was performed using LC/MS/MS. Overall, this PLD coating technique has several unique advantages over other techniques including (1) fast process times on the order of minutes, (2) flexibility in depositing a variety of material such as various polymers and composite coatings, (3) control of coating thickness, morphology, molecular weight, and structure of desired films.
9:10 AM		H4-3-3 Deposition of Anti-Bacterial Silver Coatings on Polymeric Substrates D.P. Dowling, K Donnelly, M.L. McConnell (Enterprise Ireland); R. Eloy, M.N. Arnaud (Biomatech, France) Silver exhibits good anti-bacterial properties and in recent years has been used on medical devices ranging from wound dressings to catheters. Silver coatings can be deposited by magnetron sputtering however the associated substrate heating (200- 300°C) causes considerable difficulty when coating medical devices many of which contain thermally sensitive polymer components. This paper reports on a magnetron deposited silver coating treatment where the maximum substrate temperature obtained during deposition was 70°C. This low temperature deposition was achieved by combining magnetron sputtering with a neutral atom beam (Saddle Field) plasma source. The neutral atom beam was used both to activate the polymer surface prior to coating deposition and to enhance the silver coating adhesion by bombarding the surface during film deposition. Both sources were operated simultaneously at 10ⁿ4 mbar in argon plasma. Films and tubes of polyurethane and silicone were coated with silver thicknesses in the range 5 to 50 nm. The film thickness measurements were obtained using both glancing angle XRD and variable angle ellipsometry on glass slide substrates coated adjacent to the polymers. The silver film growth rate was 10±2 nm / minute. The adhesion of the coating was examined using pull tests, tape tests and leaching tests in water at 40°C. The anti-bacterial performance of silver is dependent on the balance between the activity of the Agⁿ+ ions which kill bacteria and the total amount of silver released from the coating, which if too high results in cytoxicity. The bacterial adhesion and bactericidal effects of the coated polymers was assessed using Sraphylococcus epidermidis and the cytotoxicity using fibroblast cells. Up to a 3 log reduction in bacterial adhesion was achieved for coatings, which did not exhibit cytotoxicity.
9:30 AM		H4-3-4 Plasma Treatment of Wood Surfaces Using RF Excited Benzene and Siloxanes Discharges M.A. Algatti, R.P.C. Costa, G.C.T. Silva, G.Z. Gadioli, R.Y. Honda, R.P. Mota, E.C. Rangel, N.C. Cruz (Unesp - Universidade Estadual Paulista, Brazil) Plasma Polymerization process is a widely applied technique in several technological issues encompassing microelectronics and biomaterials industry. The main reason is that such kind of polymers are pinhole free and can resist to the attack of mild acidic and moderate basic solutions. This paper deals with plasma polymerization process of wood surfaces by RF excited glow discharges in Benzene, Siloxanes, Siloxanes-Hydrocarbon mixtures atmospheres at pressures running from 50 to 400 mTorr. Polymeric films with thickness ranging from 0,1 µm to 1 µm where grown over polished Pinus and Cedrus surfaces in glow discharges with 10 to 30 minutes duration. Polymeric films were submitted to adhesion tests using Scotch 600^TM tape and distilled boiling water. The results showed that all the films presented a good adhesion since no peeling off was observed. These results show that the plasma polymerized films were efficient in wood surface protection. Optical microscopy was performed on several samples. The results showed that the wood porosity was completely recovered by polymeric films resulting in a good wood impermeability. Nanoindentation tests revealed that the films are quite stable for all the plasma parameters used in the experiment such power and pressure for instance. One may conclude that the above mentioned films constitute an efficient material for wood surface protection. The use of such films in an industrial scale may contribute efficiently for the forests preservation due the increase of the lifetime of industrialized wood containing products.
9:50 AM	Invited	H4-3-5 The Deposition, Structure, Patterning, and Activity of Biomaterial Thin-Films by Matrix-Assisted Pulsed-Laser Deposition (MAPLE) P. Wu (Southern Oregon University); B.R. Ringeisen, J. Callahan, A. Piqué, B. Spargo, R.A. McGill, H. Kim, D.M. Bubb, D.B. Chrisey (US Naval Research Laboratory) Biomaterial thin-films, such as protein and insulin, have been deposited using Matrix-Assisted Pulsed-Laser Evaporation (MAPLE). This process involves dissolving or suspending the biomaterial in a volatile solvent, freezing the mixture to create a solid target, and using a low fluence pulsed laser to evaporate the target for deposition of the solute inside a vacuum system. Film thickness ranging from 10 nm to several um can be deposited. Both the structure and activity of these biomaterials is preserved in the deposited film. Using simple shadow masks, i.e., lines, dots, and arrays, pattern features with length scales as small as 20 μm can be deposited using multiple materials on different types of substrates. Biosensors and microarrays can thus be fabricated directly and without complicated lithographical or immobilization procedures. Adhesion of biomaterial thin-films can be improved by using composites which can be deposited and patterned using MAPLE. For sensor applications, a semipermeable overlayer can be used to protect the sensor material from a ruinous environment and yet allows the sensor to interact with specific chemicals in the ambience improving the accuracy, precision, and longevity of a sensor. Such a protective layer against water is deposited in situ and its function is confirmed. This presentation will summarize the use of MAPLE for active biomaterials and will cover the entire process from basic mechanistic studies and film characterization to specific device applications.
10:30 AM		H4-3-7 Mesoporous Silica Coatings for Medical Applications J.M. Gomez-Vega (Nagoya University, Japan); A. Hozumi (National Industrial Research Institute of Nagoya); H. Sugimura, O. Takai (Nagoya University, Japan) Ongoing research is reported aimed at preparing mesoporous silica coatings on various substrates for medical applications by a biomimetic approach (self-assembling of organic/inorganic sol-gel systems into ordered structures). Tetraethylorthosilicate (TEOS) was selected as the silica precursor, and amphiphilic triblock copolymers poly(ethylene oxide)- poly(propylene oxide)- poly(ethylene oxide) as the surfactant micellar template or structure-directing agents. The mesochannels diameter could be adjusted by changing the directing agent, and a preferred alignment of the mesostructure was observed independently of the used substrate (glass, silicon, Ti or Ti6Al4V). Three different treatments (thermocalcination, photocalcination, and solvent extraction) have been also studied to remove the organic templates, of which photocalcination showed to be the most versatile. When soaked in a simulated body fluid, mesoporous silica coatings induced apatite formation after 7 days.
10:50 AM		H4-3-8 Study of Molecular Fragmentation and Recombination Processes and Film Structure in RF Deposited Diglyme Coatings M.A. Algatti, E.F. Antunes, A.R. Bigansolli, R.Y. Honda, R.P. Mota, E.C. Rangel, N.C. Cruz, M.E. Kayama, J.C. Teixeira (Unesp - Universidade Estadual Paulista, Brazil) This papers deals with the study of the chemical reactions in gas phase in a RF excited plasmas in diglyme atmospheres and the molecular structure of the resulted films. Such kind of plasmas are of key importance in biomaterials synthesis and treatment. The study was carried out using actinometric optical emission spectroscopy and mass spectrometry. The optical spectra were obtained with a computer controlled 2m focal distance plane-grating monocromator using a photomultiplier operating in the wavelength range from 250 to 800nm. The mass spectra were collected by a mass spectrometer Hiden Analytical model EQP300 ΔM= 1amu of resolution operating in the mass range from 1 to 300amu. Plasmas were generated within a stainless steel cylindrical reactor in a plane parallel plate configuration. The RF power supply operating in 13.56 MHz was capacitively coupled to the chamber through an appropriate matching network. Mass spectrometry allowed one to follow the trends of the CH (13 amu), CH₂ (14amu), CH₃ (15amu), CH₃-O (31amu), CH₂-O-CH₃ (45 amu) and CH₂-CH₂O-CH₃ (59amu) species, resulting from the fragmentation and recombination processes of the diglyme molecule, for different plasma parameters like pressure and RF power. The results showed that the increase of the RF power coupled to the plasma chamber from 5 to 40 W produced a plasma environment much more reactive resulting in a sensitive increasing on the population of the above mentioned species. This may be attributed to the increase of the electronic temperature that makes predominant the occurrence of inelastic processes resulting in molecular fragmentation. The FTIR spectra of the plasma deposited films revealed the presence of the ethylene glycol structures within the film composition. These results allows one to conclude that the plasma parameters used in the experiment were favorable in producing a film structure with biocompatible characteristics.