Uncoated PMMA Research Articles

Effect of nano-ceramic coating on surface property and microbial adhesion to poly(methyl methacrylate).

To improve surface properties of poly(methyl methacrylate) (PMMA) using nano-ceramic coatings and assess microbial adherence after long-term use of a chemical cleanser. Thirty-six PMMA samples were fabricated, polished and coated with a nano-thin TiO2 or mixed TiO2 /ZrO2 , with uncoated samples as controls. Six samples in each group (n=12) were soaked in Polident denture cleaner 180 times for 30 min, while six were soaked in deionized water. Surface roughness of PMMA before and after being soaked in Polident was assessed. All samples were subsequently exposed to Candida albicans for 6h and the adherent cells were determined by viable colony count. Two-way analysis of variance was performed for statistical analysis. No significant difference in surface roughness was noted between the uncoated and coated PMMA before soaking. After soaking, surface roughness of the uncoated PMMA increased from 0.164 to 0.532 μm (p < .05). No significant change was observed for TiO2 -coated (0.105-0.143 μm) or TiO2 /ZrO2 -coated PMMA (0.104-0.141 μm). Attachment of C. albicans to PMMA soaked in water showed significantly less attachment to both TiO2 -coated (1.4 × 103 cfu/ml) and TiO2 /ZrO2 -coated PMMA (1.6 × 103 cfu/ml) than to the uncoated PMMA (2.6 × 103 cfu/ml). After soaking in Polident, the uncoated PMMA had significantly less C. albicans attachment than coated samples. Less attachment was noted on the TiO2 /ZrO2 -coated PMMA then the TiO2 -coated samples (p < .05). Nano-ceramic TiO22 /ZrO2 coating of PMMA denture base material alters surface properties thus reduces oral microbial adhesion. It represents a promising alternative to the chemical disinfection for PMMA denture materials.

Sputter Deposition of Titanium on Poly(Methyl Methacrylate) Enhances Corneal Biocompatibility.

PurposeTo evaluate titanium (Ti) sputtering of the poly(methyl methacrylate) (PMMA) stem of the Boston Keratoprosthesis (BK) as a method to enhance interfacial adhesion between the PMMA and the recipient corneal tissue.MethodsPMMA specimens were plasma treated with Ar/O2 and coated with Ti using a DC magnetron sputtering instrument. The topography and hydrophilicity of the surfaces were characterized using atomic force microscopy and a water contact angle instrument, respectively. Scratch hardness and adhesion of the Ti film were measured using a mechanical tester. Biocompatibility assessments were performed using cultured human corneal fibroblasts and whole blood ex vivo. The optical quality of the Ti sputtered BK was evaluated using a custom-made optical bench.ResultsBy contact angle studies, the Ti coating improved PMMA hydrophilicity to match that of medical-grade Ti (Ti-6Al-4V-ELI). Ti sputtering of contact surfaces resulted in a plate-like morphology with increased surface roughness, without impacting the transparency of the BK optical component. Scratch testing indicated that the mechanical behavior of the Ti coating was similar to that of casted Ti, and the coating was stable in pull-off adhesion testing. Sputtered Ti film was highly biocompatible based on tests of cell viability, adhesion, proliferation, differentiation, collagen deposition, and keratocan expression, the properties of which exceeded those of uncoated PMMA and did not induce increased complement activation.ConclusionsTitanium coating of the BK stem generated a mechanically and biologically favorable interface, which may help to enhance corneal stromal adhesion and biocompatibility.Translational RelevanceImproving the biocompatibility of the BK PMMA stem may improve long-term outcomes of implantation.

Bovine serum albumin conjugation on poly(methyl methacrylate) nanoparticles for targeted drug delivery applications

During the application of nanoparticles (NPs) in vivo, it is inevitable that the adsorption of proteins takes place on the surface of the nanocarriers. The formation of this protein corona determines the “identity” of the NPs and how they interact with complex biological media. By controlling the composition of the protein corona it becomes possible to improve properties of NPs and promote targeted drug delivery. In this work, poly(methyl methacrylate) (PMMA) NPs were conjugated with bovine serum albumin (BSA) by a non-covalent method. The successful conjugation of BSA to PMMA NPs was confirmed by a set of different techniques, such as dynamic light scattering, zeta potential, transmission electron microscopy, Lowry protein quantification assay and flow cytometry. Cytotoxicity assays were also performed and the results shows that NPs and conjugates did not present any cytotoxic effect on the tested cells. Cell uptake assays showed that the conjugation of BSA on PMMA NPs increased cellular uptake by HeLa cells in comparison to uncoated PMMA NPs, which is an important feature for successful drug delivery applications. These results are important evidence that it is possible to control the interaction of nanocarriers with cells, by designing a pre-formed protein corona through simple non-covalent conjugation.

Antireflection Coating on PMMA Substrates by Atomic Layer Deposition

Antireflection coatings (ARC) are essential for various optical components including such made of plastics for high volume applications. However, precision coatings on plastics are rather challenging due to typically low adhesion of the coating to the substrate. In this work, optimization of the atomic layer deposition (ALD) processes towards conformal optical thin films of Al2O3, TiO2 and SiO2 on poly(methyl methacrylate) (PMMA) has been carried out and a five-layer ARC is demonstrated. While the uncoated PMMA substrates have a reflectance of nearly 8% in the visible (VIS) spectral range, this is reduced below 1.2% for the spectral range of 420–670 nm by applying a double-side ARC. The total average reflectance is 0.7%. The optimized ALD coatings show a good adhesion to the PMMA substrates even after the climate test. Microscopic analysis on the cross-hatch areas on PMMA after the climate test indicates very good environmental stability of the ALD coatings. These results enable a possible route by ALD to deposit uniform, crack free, adhesive and environmentally durable thin film layers on sensitive thermoplastics like PMMA.

Low-Temperature Preparation of Mechanically Robust and Contamination-Resistant Antireflective Coatings for Flexible Polymeric Glasses via Embedding of Silica Nanoparticles and HMDS Modification.

Mechanical and contamination-resistant properties are the most crucial and challenging issues that impede the practical applications of sol-gel antireflective (AR) coating. In this paper, we report a low-temperature vapor surface treatment strategy for the partial embedding and surface functionalization of silica nanoparticles (SNPs) on flexible polymeric glass substrates. SNPs, which were synthesized via the Stöber method, were partially embedded into the polymeric glass substrates by vapor-phase surface treatment using volatile chloroform. Further vapor-phase surface treatments by water and hexamethyldisilazane (HMDS) were applied successively to achieve high trimethylsilyl coverage of the SNPs. The HMDS modification could convert the polar surface of SNPs to a nonpolar surface for contamination resistance, while ammonia, as a byproduct generated, could help to cross-link the SNPs via self-condensation of silanol groups, thus hardening the coating. The SNP-CWH coatedpolymethylmethacrylate (PMMA) substrate shows an average transmittance of 98.62% in the wavelength region of 400-800 nm, which is 6.32% higher than that of the uncoated bare PMMA. The AR performance of SNP-CWH coated PMMA shows almost no degradation after 100 times of rubbing or bending, indicating the greatly enhanced abrasion resistance and flexibility. Furthermore, the SNP-CWH coating exhibits superior contamination-resistant property, where the transmittance curve of the coated substrate displays a barely noticeable change after exposure to a "dirty" environment with water and organic contaminants for 6 months. This work paves a new way for developing mechanically robust and contamination-resistant AR coating for polymeric substrates.

Improving Polymethyl Methacrylate Resin Using a Novel Titanium Dioxide Coating.

The objective of this study was to improve the surface characteristics of poly (methyl methacrylate) (PMMA) by developing a novel, thin film coating process and to characterize the resulting coated surface. An atomic layer deposition (ALD) technique was developed to deposit a titanium dioxide (TiO2 ) nano-thin film on PMMA. The surface wettability for both coated and uncoated PMMA was determined by measuring water contact angle. Wear resistance was assessed using a mechanical tooth-brushing device with a 50 g load for 6000 strokes after 5 months of water storage. A denture cleanser challenge test was performed by using sonication in 3.8% sodium perborate for 1 hour with aged specimens. X-ray photoelectron spectroscopy (XPS) was used before and after the brushing test and challenge test to analyze the PMMA surface chemical composition. The mechanical strength of coated and uncoated PMMA was measured using a three-point bending test. Surface microbial interactions were also evaluated by assessing Candida albicans biofilm attachment. Nano-TiO2 coating (30 nm thick) was successfully deposited on PMMA at 65°C. After coating, water contact angle decreased from 70° to less than 5°. After brushing test, the coating remained intact. XPS analysis revealed no loss of TiO2 from coated specimens following brushing and denture cleanser sonication for 1 hour. There was no statistically significant difference in mechanical strength (MPa) (mean ± SD) between PMMA (139.4 ± 11.3) and TiO2 -PMMA (160.7 ± 37.1) (p = 0.0995). C. albicans attachment decreased by 63% to 77% on the coated PMMA surface. ALD is a promising technique to modify surface properties of PMMA and resulted in a stable adherent thin film. By depositing a TiO2 coating, PMMA surface properties may lead to significantly reduced microorganism adhesion and easier pathogen removal from PMMA. For patients who wear dentures, reducing the oral microbial biofilm burden using a TiO2 -coated PMMA surface could positively impact their oral and systemic health.

Light propagation in multimoded square hollow waveguides

The irradiance–distance relation for light propagation in multimoded hollow waveguides is calculated from theory and compared with measurement for visible light. These are the first measurements of this relation for square waveguides and the first for round waveguides for visible light. The square waveguides had either silvered glass surfaces or uncoated PMMA surfaces. A geometric optics method based on image formation in a kaleidoscope is used for calculations. The measurements agreed with the predictions of theory in all cases. The loss is not described by a fixed value of an attenuation coefficient as the angular divergence of the light changes with distance. At larger distances the logarithm of the irradiance is linearly dependent on the logarithm of distance, regardless of material type, surface properties and waveguide cross section. The silvered square waveguide shows the lowest measured attenuation while PMMA square waveguides constructed without any special surface preparation performed almost as well as silvered round tubes sourced commercially. The surface roughness present in the silver coating of commercially sourced round tubes compromised their performance. An array of square PMMA waveguides was used to demonstrate an application for signal transport in megavoltage radiation fields for profiling a medical radiation beam and measuring the variation of dose rate with depth in water.

Polydopamine coatings enhance biointegration of a model polymeric implant

The biointegration of implants affects their function, stability and safety. Although most research on this topic has focused on bone and other hard tissues, biointegration with soft tissues is important in numerous applications, such as in prosthetic corneas. Here, we have adapted polydopamine-based adhesive surface chemistry to enhance the biointegration with soft tissue of a model polymer—poly(methyl methacrylate) (PMMA), commonly used in prosthetic corneas. Polydopamine coating (PDA) and subsequent modification with the cell-adhesive peptide RGD (PDA-PEG-RGD) significantly enhanced cellular proliferation of corneal epithelial cells and keratocytes without causing excessive secretion of pro-inflammatory cytokines (e.g.IL-6) by either cell type. PDA adhered tightly to collagen gels, while PDA-PEG-RGD and uncoated PMMA did not. PDA's adhesion to collagen was greatly reduced by preincubation in serum. Tissue reaction to both polydopamine-coated surfaces was benign after 45 days of subcutaneous implantation. However, in contrast to the findings with collagen gels, PDA-PEG-RGD bound much more tightly to tissue than did PDA—although both bound better than unmodified PMMA. Polydopamine-based surface chemistries are potentially useful in enhancing tissue integration of implants with soft tissues.

Cohesive and adhesive properties of polycaprolactone/silica hybrid coatings on poly(methyl methacrylate) substrates

Organic–inorganic hybrid materials were prepared using the sol–gel process in order to improve the scratch resistance of poly(methyl methacrylate) (PMMA) substrates. Sol–gel solutions based on tetraethoxysilane and α,ω-triethoxysilane terminated polycaprolactone with two different organic / inorganic weight ratios (5 / 5 and 7 / 3) were applied and cured on the substrate. The final coatings consisted of interconnected nanodomains of silica and polycaprolactone, which increased in size and resulted into microdomains when the content of organic phase increased. The surface energies of coated and uncoated PMMA, and the cohesive and adhesive properties of the hybrid coatings were examined using contact angle measurements, and fragmentation tests, respectively. The surface energy of the hybrid coatings and their work of adhesion to the PMMA substrate were found to be similar, with a higher polar contribution at increasing silica content. In contrast, the strain to failure, cohesive strength, toughness and adhesion to PMMA of the coating with a 5 / 5 organic / inorganic ratio were considerably higher, compared to the coating with a 7 / 3 organic / inorganic ratio. These results demonstrate that the adhesion strength is the result of a series of complex phenomena that probably involves diffusion of reactants in PMMA and their crosslinking, as suggested by electron energy loss spectroscopy analyses, other than effects deriving from residual stresses and from the morphology produced during the formation of the coating.

Poly(caprolactone)/silica organic-inorganic hybrids as protective coatings for poly(methyl methacrylate) substrates

Organic-inorganic hybrid materials (also known as ceramers or phase-interconnected nanocomposites) were prepared starting with tetraethyoxysilane and α,θ-triethoxysilane-terminated poly(e-caprolactone) (PCL-Si) using the sol-gel process. In all cases the formation of nanocomposites with a high level of interpenetration between PCL and SiO2 phases was noted. Poly(methyl methacrylate) (PMMA) slabs were dip-coated with PCL-Si/silica hybrids and a preferential segregation of silica on to the outer surface was found, together with a PCL-rich coating PMMA interface. In all cases, a marked reduction in both the average roughness and the apparent friction coefficient was noted with respect to the uncoated PMMA. All the PCL-Si/SiO2-coated samples showed a significant increase in flame resistance before and after UV irradiation, while improvements in the anti-scratch properties were noted only in the case of the PMMA coated with silica-rich ceramers.

Structures induced in polysilane and thin polysilane layer coated polymer films by irradiation of femto-second laser pulse

We investigated the structures induced in polysilane and polysilane coated thermoplastic bis-phenol A type epoxy (Epoxy) and poly(methyl methacrylate) (PMMA) films by irradiation of near-infrared (NIR) femto-second laser pulse. Long stripe-shaped structures with approximately 200–400 μm length was induced in polysilane bulk. Thin polysilane layer coated Epoxy and PMMA films showed photo-sensitive effect on the formation of stripe-shaped structures in PMMA and Epoxy, whereas no structures were induced in uncoated PMMA and Epoxy films. An ensemble of stripe-shaped structures worked as a diffraction grating. This photo-sensitive effect has potential application to grating structures in optical polymeric fiber (OPF).

Well-defined sulfobetaine-based statistical copolymers as potential antibioadherent coatings.

The potential use of novel poly(sulfobetaine) copolymers as antibioadherent coatings was investigated using Pseudomonas aeruginosa as a model microorganism and human macrophages and 3T3 mouse embryonic fibroblasts. Two well-defined statistical copolymers with narrow molecular weight distributions were prepared by group transfer copolymerization of n-butyl methacrylate (nBuMA) with either 10 or 30 mol % 2-(dimethylamino)ethyl methacrylate (DMAEMA). Sulfobetainized nBuMA-DMAEMA copolymers (poly[sulfobetaine-stat-nBuMA]) were obtained by treating these precursor polymers with 1,3-propanesultone under mild conditions. Both proton NMR spectroscopy and elemental microanalyses indicated that essentially all the DMAEMA residues were derivatized in both copolymers. Poly(methyl methacrylate) (PMMA) discs were coated with the sulfobetainized nBuMA-DMAEMA copolymers and the bioadherent properties of these coated materials were compared with those of PMMA. Statistically significantly fewer (p<.05) bacteria, macrophages, and fibroblasts adhered to the poly(sulfobetaine-stat-nBuMA)-coated PMMA than to the uncoated PMMA. The poly(sulfobetaine-stat-nBuMA) copolymer containing the higher proportion (30 mol %) sulfobetainized DMAEMA residues proved to be the more effective antibioadherent coating. The antibioadherent properties of these coating materials may allow the cost-effective production of dirt-resistant, easy to clean work surfaces, bioinert coatings for medical devices, and antifouling coatings for marine, agricultural, and industrial applications.

Well-defined sulfobetaine-based statistical copolymers as potential antibioadherent coatings

The potential use of novel poly(sulfobetaine) copolymers as antibioadherent coatings was investigated using Pseudomonas aeruginosa as a model microorganism and human macrophages and 3T3 mouse embryonic fibroblasts. Two well-defined statistical copolymers with narrow molecular weight distributions were prepared by group transfer copolymerization of n-butyl methacrylate (nBuMA) with either 10 or 30 mol % 2-(dimethylamino)ethyl methacrylate (DMAEMA). Sulfobetainized nBuMA-DMAEMA copolymers (poly[sulfobetaine-stat-nBuMA]) were obtained by treating these precursor polymers with 1,3-propanesultone under mild conditions. Both proton NMR spectroscopy and elemental microanalyses indicated that essentially all the DMAEMA residues were derivatized in both copolymers. Poly(methyl methacrylate) (PMMA) discs were coated with the sulfobetainized nBuMA-DMAEMA copolymers and the bioadherent properties of these coated materials were compared with those of PMMA. Statistically significantly fewer (p<.05) bacteria, macrophages, and fibroblasts adhered to the poly(sulfobetaine-stat-nBuMA)-coated PMMA than to the uncoated PMMA. The poly(sulfobetaine-stat-nBuMA) copolymer containing the higher proportion (30 mol %) sulfobetainized DMAEMA residues proved to be the more effective antibioadherent coating. The antibioadherent properties of these coating materials may allow the cost-effective production of dirt-resistant, easy to clean work surfaces, bioinert coatings for medical devices, and antifouling coatings for marine, agricultural, and industrial applications.

Endothelial damage caused by uncoated and fluorocarbon-coated poly(methyl methacrylate) intraocular lenses

Purpose: To assess endothelial damage induced by poly(methyl methacrylate) (PMMA) intraocular lenses (IOLs) coated with a fluorocarbon polymer, Teflon™ AF to make them highly hydrophobic.Setting: Department of Ophthalmology, Hôtel-Dieu Hospital, Paris, France.Methods: Ten Teflon-coated and 10 uncoated PMMA IOLs were used in an in vitro static touch model. The corneal endothelium was placed in direct contact with the IOL for 15 seconds and then stained with trypan blue and alizarin red. The endothelial damage produced by each IOL in the area of contact was assessed semiquantitatively and quantitatively.Results: Teflon-coated IOLs produced significantly less endothelial damage than uncoated PMMA IOLs (P < .0001). Endothelial cells in contact with Teflon-coated IOLs did not usually adhere to the IOL surface. In contrast, the uncoated IOLs produced large areas of endothelial cell loss.Conclusion: Teflon-coated PMMA IOLs have an antiadhesive effect that reduced endothelial damage after IOL insertion in an in vitro model.