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PubMed1988

In vitro evaluation of iris chafe protection afforded by hydrophilic surface modification of polymethylmethacrylate intraocular lenses.

An in vitro iris chafe test was developed to evaluate possible differences in abrasive interaction of various intraocular lens (IOL) materials with the posterior surface of the iris. The materials that were compared in initial tests with rabbit irides were high molecular weight polymethylmethacrylate (PMMA), the primary IOL material in current use, and surface-modified PMMA, which had a permanent, chemically bound, hydrophilic, polymer surface. Scanning electron microscopy, light microscopy, and examination of histological sections were used to assess tissue damage. A "window defect" type of abrasive damage was observed by light microscopy for PMMA lenses and is very similar in appearance to that seen for iris abrasion by human implants when viewed in vivo in slitlamp examinations. Results for both pigmented and albino rabbit irides indicate a reduction in abrasive insult to the external iris basement membrane and underlying pigment epithelium by the hydrophilic surface modification of PMMA. These results are consistent with our observation of a major reduction in corneal endothelium damage on contact with the hydrophilic surface-modified PMMA as compared with PMMA itself. This in vitro iris abrasion test, therefore, appears to be a useful technique for future evaluation of IOL surface properties.

Animals↗
PubMed2006

Surface modification of silica core-shell nanocapsules: biomedical implications.

In this article we present the synthesis of oil core silica shell nanocapsules with different shell thicknesses. The surface of the nanocapsules was modified with polyethyleoxide (PEO) and succinic anhydride. Two biomedical tests were then used to study the biocompatibility properties of these nanocapsules with different surface treatments, hemolysis and thromboelastography (TEG). PEO surface modification greatly reduced the damaging interactions of nanocapsules with red blood cells (RBCs) and platelets and attenuated particle size effects. It was found that the blood toxicity of charged particles increased with the acid strength on the surface. Experiments toward the assessment of detoxification of these nanocapsules in model drug overdose concentrations are currently underway.

Animals↗
PubMed2004

Plasma surface modification of organic materials: comparison between polyethylene films and octadecyltrichlorosilane self-assembled monolayers.

Low-pressure low-frequency NH3 plasmas have been used for the surface modification of bulk polyethylene films and of octadecyltrichlorosilane (OTS) self-assembled monolayers deposited on oxidized silicon wafers. The incorporation of nitrogen-containing groups by the plasma treatment has been followed by contact angle measurements and by X-ray photoelectron spectroscopy. The surface degradation of the OTS monolayers due to plasma etching has been measured separately by optical ellipsometry with subnanometric accuracy. Our data show clear evidence for the existence of an optimum treatment time, yielding a high density of NH2 functional groups without significant variation of the structural features of the organic material. Self-assembled monolayers appear as excellent model systems to characterize the effects of plasma discharges on polyolefins. In particular, they allow testing the influence of molecular orientation, packing density, and crystallinity on the final results.

Ammonia↗
PubMed2005

Surface modification of starch based blends using potassium permanganate-nitric acid system and its effect on the adhesion and proliferation of osteoblast-like cells.

The surface modification of three starch based polymeric biomaterials, using a KMnO4/HNO3 oxidizing system, and the effect of that modification on the osteoblastic cell adhesion has been investigated. The rationale of this work is as follows--starch based polymers have been proposed for use as tissue engineering scaffolds in several publications. It is known that in biodegradable systems it is quite difficult to have both cell adhesion and proliferation. Starch based polymers have shown to perform better than poly-lactic acid based materials but there is still room for improvement. This particular work is aimed at enhancing cell adhesion and proliferation on the surface of several starch based polymer blends that are being proposed as tissue engineering scaffolds. The surface of the polymeric biomaterials was chemically modified using a KMnO4/HNO3 system. This treatment resulted in more hydrophilic surfaces, which was confirmed by contact angle measurements. The effect of the treatment on the bioactivity of the surface modified biomaterials was also studied. The bioactivity tests, performed in simulated body fluid after biomimetic coating, showed that a dense film of calcium phosphate was formed after 30 days. Finally, human osteoblast-like cells were cultured on unmodified (control) and modified materials in order to observe the effect of the presence of higher numbers of polar groups on the adhesion and proliferation of those cells. Two of the modified polymers presented changes in the adhesion behavior and a significant increase in the proliferation rate kinetics when compared to the unmodified controls.

Body Fluids↗
PubMed2003

Formation of low-symmetric 2D superlattices of gold nanoparticles through surface modification by acid-base interaction.

In the present work, a novel method was developed for the fabrication of 2D superlattices with different symmetries. Same-surface amino-functionalized Au nanoparticles as building blocks were self-assembled to form different 2D superlattices using surface modification with organic acids. The 2D superlattices of quasi-honeycomb and square structures were obtained by neutralizing amino-functionalized Au nanoparticles with 1,3,5-tribenzenecarboxylic acid and acetic acid, respectively. These results strongly suggest that the different types of 2D or 3D superlattices can be constructed by simple addition of proper acid to nanoparticles functionalized with amino groups. This method will allow us to obtain various desired metal superlattices without fully synthesizing the ligands.

Journal Article↗
PubMed2002

Fabrication and surface modification of macroporous poly(L-lactic acid) and poly(L-lactic-co-glycolic acid) (70/30) cell scaffolds for human skin fibroblast cell culture.

The fabrication and surface modification of a porous cell scaffold are very important in tissue engineering. Of most concern are high-density cell seeding, nutrient and oxygen supply, and cell affinity. In the present study, poly(L-lactic acid) and poly(L-lactic-co-glycolic acid) (70/30) cell scaffolds with different pore structures were fabricated. An improved method based on Archimedes' Principle for measuring the porosity of scaffolds, using a density bottle, was developed. Anhydrous ammonia plasma treatment was used to modify surface properties to improve the cell affinity of the scaffolds. The results show that hydrophilicity and surface energy were improved. The polar N-containing groups and positive charged groups also were incorporated into the sample surface. A low-temperature treatment was used to maintain the plasma-modified surface properties effectively. It would do help to the further application of plasma treatment technique. Cell culture results showed that pores smaller than 160 microm are suitable for human skin fibroblast cell growth. Cell seeding efficiency was maintained at above 99%, which is better than the efficiency achieved with the common method of prewetting by ethanol. The plasma-treatment method also helped to resolve the problem of cell loss during cell seeding, and the negative effects of the ethanol trace on cell culture were avoided. The results suggest that anhydrous ammonia plasma treatment enhances the cell affinity of porous scaffolds. Mass transport issues also have been considered.

Cells, Cultured↗
PubMed2001

Surface modifications and molecular imprinting of polymers in medical and pharmaceutical applications.

Recent developments in the field of biomaterials are based on molecular design of polymers with improved surface and bulk properties. Novel techniques of surface modification by addition of tethered chains can lead to materials with the ability to recognize biological and pharmaceutical compounds. Methods based on molecular imprinting can increase the recognition capabilities of such systems. Chain tethering can also can improve the mucoadhesive behavior of a delivery device and the effectiveness of a drug by allowing targeting and localization of a drug at a specific site. Acrylic-based hydrogels are well-suited for mucoadhesion due to their flexibility and nonabrasive characteristics which reduce damage-causing attrition to the tissues in contact. However, the adhesive and drug delivery capabilities of these devices can continue to be improved as presently known bioadhesive materials are modified and more bioadhesive materials are discovered. Tethering of long PEG chains on PAA hydrogels and their copolymers can be achieved by grafting reactions involving thionyl chloride, followed by PEG grafting. The ensuing materials exhibit mucoadhesive properties due to enhanced anchoring of the chains with the mucosa. Theoretical calculations can lead to optimization of the tethered structure.

Biocompatible Materials↗
PubMed1992

Effect of heparin surface modification of polymethylmethacrylate intraocular lenses on signs of postoperative inflammation after extracapsular cataract extraction. One-year results of a double-masked multicenter study.

PURPOSE: A heparin surface modified posterior chamber intraocular lens (IOL) was compared with a conventional polymethylmethacrylate (PMMA) IOL regarding postoperative complications caused by inflammation. METHODS: Five hundred twenty-four patients from 10 different centers were included in a parallel group, double-masked, multicenter study. RESULTS: The cumulative number of patients with inflammatory cellular deposits on their IOLs during the first postoperative year differed significantly in favor of the heparin surface modified group, with 29.8% of the patients having cellular deposits compared with 48.8% of patients in the control group. Cellular deposits were observed most frequently at 3 months after surgery, and the difference between the groups was most pronounced and statistically significant at this time. The same results were seen at 1 year, but the difference was not significant. The number of cellular deposits per patient, however, was significantly lower in the heparin surface modified group at 1 year. Cumulatively, there were significantly more patients with posterior synechiae in the PMMA group than in the heparin surface modified group during the 1-year follow-up. Complications were few and comparable between the groups. CONCLUSION: The results of this study indicate that heparin surface modification reduces the inflammatory response to PMMA IOLs.

Adult↗
PubMed2007

Effect of surface modification of siliconeon Staphylococcus epidermidis adhesion and colonization.

Cerebrospinal fluid (CSF) shunts for the treatment of hydrocephalus are generally made of silicone rubber. The growth of bacterial colonies on the silicone surface leads to frequent CSF shunt complications. A systematic study of the effect of the surface modification of silicone on Staphylococcus epidermidis adhesion and colonization was performed for different incubation times by means of colony counting and scanning electron microscopy (SEM). Silicone was modified with different biopolymers and silanes, including heparin, hyaluronan, octadecyltrichlorosilane (OTS), and fluoroalkylsilane (FAS) to provide a stable and biocompatible surface with different surface functional groups and degrees of hydrophobicity. The modified silicone surfaces were studied by using contact angle measurements, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). After 4 and 8 h of incubation, the FAS- and OTS-coated silicone and the hyaluronan coated OTS/silicone surfaces showed significantly reduced bacterial adhesion and colonization compared to blank silicone by both quantification methods. However, the heparin coated OTS/silicone showed significantly increased bacterial adhesion. These results indicate that the nature of the surface functional group and surface roughness determine the extent of bacterial adhesion and colonization. However, the degree of hydrophobicity of the surface did not appear to play a determining role in bacterial adhesion and colonization.

Bacterial Adhesion↗
PubMed2005

Surface modification of titanium by etching in concentrated sulfuric acid.

OBJECTIVE: The purpose of this study was to characterize the etching behavior of titanium in concentrated sulfuric acid and discuss its application on surface modification of titanium for biological use. METHODS: Commercially pure titanium (cpTi) plate was etched in 48% H2SO4 at RT -90 degrees C for 0.25-8 h. The weight loss was derived from the weight differences before and after etching. The surfaces after etching were characterized by surface roughness, X-ray diffractometry, and scannning electron spectroscopy. The apparent activation energy of the dissolution of cpTi into acid was derived from an Arrhenius plot of the rate of weight loss versus the acid temperature. RESULTS: The surface roughness of cpTi increased with the acid temperature and etching time. The surface roughness was strongly related to the weight loss. The weight loss increased drastically with the acid temperature after an initial period, which shortened with increasing acid temperature. The apparent activation energy for the dissolution of cpTi in H2SO4 was derived as 67.8 kJ/mol. SIGNIFICANCE: This study indicates that etching with concentrated sulfuric acid is an effective way to modify the surface of titanium for biological applications.

Acid Etching, Dental↗
PubMed2004

Engineered microcrystals for direct surface modification with layer-by-layer technique for optimized dissolution.

This investigation relates to a two-step formulation development technique-synthesis of sterically stabilized drug microcrystals followed by direct surface modification by sequential electrostatic adsorption. Stable microcrystals of naproxen were produced by pH-induced reprecipitation in presence of a stabilizer. Sequential layer growth was achieved by the layer-by-layer assembly of biocompatible polyelectrolytes (PEs) and was registered using microelectrophoresis. The coated colloids were characterized using confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). The in vitro controlled release pattern of the drug through the PE diffusion barrier was studied using a diffusion cell assembly at physiological pH of 7.4, both before and after freeze-drying. Thermodynamically stable naproxen microcrystals were obtained by association and had a mean length of 15 microm and a zeta potential of -37.5 mV and were surface modified efficiently using biocompatible polysaccharide/protein-based PEs. Sufficient charge reversal with each layer was evident indicating layer growth with successive deposition cycles. The coating was complete and homogeneous as visualized under CLSM and SEM. The in vitro release study revealed that the stoichiometry of PEs in the complex coating and its molecular architecture played important roles in forming the diffusion barrier, which offered efficient control of the dissolution rate of drug core (up to 50% lower than bare crystal). The release profile fitted zero order release kinetics. This novel formulation technique enables administration of high concentrations of water-insoluble drugs in a stable, tissue compatible form, simultaneously affording sustained release.

Chemical Engineering↗
PubMed2003

Surface modifications induced by ns and sub-ps excimer laser pulses on titanium implant material.

Medical implants used in oral and orthopaedic surgery are mainly produced from titanium. Their biological behaviour, e.g. osseointegration, essentially depends on both the chemical composition and the morphology of the surface. Modifications achieved by excimer laser irradiation of titanium samples were investigated in order to improve their surface characteristics so as to facilitate biointegration. To enlarge the effective interfacial area of bone-implant contact, holes were ablated by laser pulses of ns or sub-ps length. During ns ablation, crown-like projecting rims formed around the borders of the holes. Ultra-short (0.5ps) KrF excimer laser pulses were successfully applied to avoid these undesirable formations. Since a smooth dental implant surface is necessary to maintain a healthy connection with the soft tissues, laser polishing of samples was investigated, too. Irradiation with a series of ns laser pulses resulted in effective smoothing, as measured with atomic force microscope. X-ray photoelectron spectroscopy analysis of the laser-polished titanium surface revealed that laser treatment led to a decrease of the surface contamination and in thickening of the oxide layer. X-ray diffraction measurements demonstrated that the original alpha-titanium crystal structure was preserved.

Biocompatible Materials↗
PubMedDate not supplied

Surface modification of stents for improving biocompatibility.

Much headway is being made in the quest to improve biocompatibility and reduce restenosis related to the use of stents. This article reviews the research data involving stent coatings and surface treatments techniques. It also describes recent work in surface modification of metallic stents and covalent coupling of drugs that employs a novel bonding process.

Animals↗
PubMed2006

Surface modification by electric discharge implemented with electrodes composed of carbon nanotubes.

In this work the electric discharge machining (EDM) implementing with multi-wall carbon nanotubes (MWCNT) as a miniscule electrode for pursuing precise surface modification was studied. The excellent upright growth of carbon nanotubes on copper based alloy substrates by a radio frequency (RF) assisted hot filament chemical vapor deposition (HFCVD) method suggests us to exploit MWCNTs as the miniature electrodes for discharge machining. The results reveal that the electrodes are much endurable to be distorted even when the spoiling rates for the polishing of n-type Si wafer (of 10 to approximately 100 omega-cm) are up to 30 nm/min with. It is expected that MWCNTs can be applied to non-conventional material processing especially in miniature discharge machining.

Alloys↗
PubMed2005

Influence of surface modification of Ti-SBA15 catalysts on the epoxidation mechanism for cyclohexene with aqueous hydrogen peroxide.

The thermolytic molecular precursor method was used to introduce site-isolated Ti(IV) centers onto the surface of a mesoporous SBA15 support. The resulting surface Si-OH/Ti-OH sites of the Ti-SBA15 catalysts were modified with a series of (N,N-dimethylamino)trialkylsilanes, Me(2)N-SiMe(2)(R) (where R = Me, (n)Bu, or (n)Oc). Compared with the unmodified catalysts, the surface-modified catalysts are more active in the oxidation of cyclohexene with H(2)O(2) and exhibit a significantly higher selectivity (up to 58%) for cyclohexene oxide formation (vs allylic oxidation products). In situ Fourier transform infrared (FTIR) and diffuse reflectance UV visible (DRUV-vis) spectroscopies were used to probe this phenomenon, and it was determined that active sites with capped titanol centers, (SiO(surface))(3)Ti(OSiR(3)), likely undergo Ti-OOH formation upon addition of H(2)O(2) in a manner analogous to that for active sites of the type (SiO(surface))(3)TiOH. On the basis of the observation of similar Ti-OOH intermediates for both species, the electron-withdrawing effects on the Ti(IV) active site, resulting from the surface modification, are likely responsible for the observed increase in selectivity.

Journal Article↗
PubMed2003

Enhancement of bone growth in titanium fiber mesh by surface modification with hydrogen peroxide solution containing tantalum chloride.

A tight fixation between bone and implant materials is of great importance for a successful outcome of procedures such as total knee arthroplasty (TKA) and total hip arthroplasty (THA). Surface modification of titanium metal and titanium alloy is one of the attractive methods to improve the biological affinity of orthopedic prostheses. Recent studies reported that titanium substrates were provided with bone-bonding ability, that is, osteoconductivity, through a chemical treatment with hydrogen peroxide solution containing tantalum chloride. The present study investigated the histological and mechanical effects of such treatment of the surface of titanium fiber mesh. Titanium alloy rods of 7.6 x 7.6 x 20 mm that had a titanium fiber mesh of 250 microm were implanted bilaterally into the distal aspect of the femur of adult beagle dogs. At 3, 5, and 8 weeks after implantation, the rods were removed to examine their bonding strength and histological compatibility with bone. Bonding strength was evaluated by the pull-out test. The bonding strength of the treated specimen with bone increased with time, and was faster than that of untreated specimens. At 8 weeks postoperative, the bonding strength of both the treated and untreated specimens became almost equal. The amount of newly formed bone on and in the titanium fiber mesh was significantly increased by the chemical treatment (p<0.05). The rate of bone formation in the fiber mesh was accelerated after chemical treatment. These results indicated that the surface treatment enhanced bone formation in the initial stage thank to the osteoconductive property of the titanium fiber mesh conferred by the chemical treatment so that faster bonding strength was achieved. Surface treatment providing titanium mesh with osteoconductivity has the advantages of the fast healing and tight bonding for prostheses in TKA and THA.

Animals↗
PubMed1998

Integration of surface modification and 3D fabrication techniques to prepare patterned poly(L-lactide) substrates allowing regionally selective cell adhesion.

Regeneration of organizationally complex tissue requires regulation of spatial distributions of particular cell types in three dimensions. In this paper we demonstrate an integration of polymer processing and selective polymer surface modification using methods suitable for construction of three-dimensional polymer scaffolds which may aid such cell organization. Specifically, the surfaces of degradable polyesters were modified with poly(ethylene-oxide) (PEO)-poly(propylene-oxide) (PPO) copolymers using a process compatible with a solid free-form fabrication technique, the 3DP printing process. We demonstrate inhibition of cell (hepatocyte and fibroblast) adhesion to regions of two-dimensional poly(lactide) (PLA) substrates modified with PEO-PPO-PEO copolymers. We further show that PEO-PPO-PEO-modified surfaces which are not adhesive for hepatocytes or fibroblasts can be made selectively adhesive for hepatocytes by covalent linkage of a carbohydrate ligand specific for the hepatocyte asialoglycoprotein receptor to the PEO chain ends. Our approach may be generally useful for creating regionally selective, microarchitectured scaffolds fabricated from biodegradable polymers, for spatial organization of diverse cell types.

3T3 Cells↗