Surface modification of poly-L-lactic acid (PLLA) membrane by grafting acrylamide: an effective way to improve cytocompatibility for chondrocytes

Poly-L-lactic acid (PLLA) membranes were photo-oxidized in hydrogen peroxide solution under ultraviolet light (UV) to introduce hydroperoxide groups onto the PLLA membrane surfaces. The photo-oxidized membranes were then immersed in acrylamide (AAm) solution containing Fe2+ to graft polyacrylamide (PAAm) onto the PLLA membrane surfaces. The density of the hydroperoxide groups introduced on the PLLA membrane surfaces varied with the temperature and the photo-oxidization time. The occurrence of grafting was verified by X-ray photoelectron spectroscopy (XPS). The degree of grafting increased with the monomer concentration and the polymerization time. Water contact angle measurements showed that the wettability of the modified PLLA membranes had improved. Chondrocytes proliferated more rapidly and were more spread out on the modified membrane than on the control PLLA membrane, indicating that the PAAm-grafted PLLA membrane has better cytocompatibility for chondrocytes.     

UV surface modification of a new nanocomposite polymer to improve cytocompatibility

A novel modified nanocomposite was studied for the adhesion and proliferation of the human umbilical vein endothelial cell (HUVEC) line EA.hy926. The nanocomposite under investigation was poly(carbonate-urea)urethane with silsesquioxane nano-cages, here in the form of a mixture of two polyhedral oligomeric silsesquioxanes. The nanocomposite surfaces were exposed to ultraviolet (UV) light of a Xe^* ₂-excimer lamp at a wavelength of 172 nm in an ammonia atmosphere. The effects of the irradiation were characterized by atomic force and scanning electron microscopy (AFM, SEM), X-ray photo-electron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR) using an attenuated total reflection (ATR) device and measurements of advancing water contact angle (CA). The irradiation resulted in the introduction of new hydrophilic N- and O-containing groups into the surface, which was initially amphiphilic, while surface morphology remained mainly unchanged. Slight chemical changes were also observed for the silsesquioxane nano-cages at the surface. Onto the untreated and irradiated samples HUVECs were seeded and grown for various durations in culture. Standard tissue-culture polystyrene (PS) was employed as a positive control to check the efficiency of the cell-culture methods. Viability and proliferation of the cells were then assessed using a non-radioactive assay. Compared to the untreated nanocomposite polymer, irradiation times of at least 5 min resulted in a significantly increased cell proliferation between 3 and 8 days after seeding with the HUVEC line EA.hy926.     

UV surface modification of a new nanocomposite polymer to improve cytocompatibility

A novel modified nanocomposite was studied for the adhesion and proliferation of the human umbilical vein endothelial cell (HUVEC) line EA.hy926. The nanocomposite under investigation was poly(carbonate-urea)urethane with silsesquioxane nano-cages, here in the form of a mixture of two polyhedral oligomeric silsesquioxanes. The nanocomposite surfaces were exposed to ultraviolet (UV) light of a Xe(*)(2)-excimer lamp at a wavelength of 172 nm in an ammonia atmosphere. The effects of the irradiation were characterized by atomic force and scanning electron microscopy (AFM, SEM), X-ray photo-electron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR) using an attenuated total reflection (ATR) device and measurements of advancing water contact angle (CA). The irradiation resulted in the introduction of new hydrophilic N- and O-containing groups into the surface, which was initially amphiphilic, while surface morphology remained mainly unchanged. Slight chemical changes were also observed for the silsesquioxane nano-cages at the surface. Onto the untreated and irradiated samples HUVECs were seeded and grown for various durations in culture. Standard tissue-culture polystyrene (PS) was employed as a positive control to check the efficiency of the cell-culture methods. Viability and proliferation of the cells were then assessed using a non-radioactive assay. Compared to the untreated nanocomposite polymer, irradiation times of at least 5 min resulted in a significantly increased cell proliferation between 3 and 8 days after seeding with the HUVEC line EA.hy926.     

Immobilization of chitosan onto poly-L-lactic acid film surface by plasma graft polymerization to control the morphology of fibroblast and liver cells

Surface functionalization of biodegradable poly-L-lactic acid (PLLA) was achieved by plasma coupling reaction of chitosan. The structure of modified PLLA surfaces was characterized by contact angle measurements and X-ray photoelectron spectroscopy. Two cell lines, L929 (mouse fibroblasts) and L02 (human hepatocytes), were cultured on the modified PLLA surface. It was found that cells cultured on this film could hardly spread and tend to become round, and the film was demonstrated to be a poorly adhering substrate. However, cells grown on this substrate can proliferate at almost the same speed as cultured on a glass surface. These results suggest that the new substrate can be used to control the morphology of cells, and has potential applications in tissue engineering. It may be helpful in understanding the mechanism of the switch between cell phases of growth and differentiation, which is necessary for the design of tissue regeneration biomaterials.     

Surface modification of poly(L-lactic acid) to improve its cytocompatibility via assembly of polyelectrolytes and gelatin

Poly(L-lactide) (PLLA) surface was modified via aminolysis by poly(allylamine hydrochloride) (PAH) at high pH and subsequent electrostatic self-assembly of poly(sodium styrenesulfonate) (PSS) and PAH, and the process was monitored by X-ray photoelectron spectroscopy (XPS) and contact angle measurement. These modified PLLAs were then used as charged substrates for further incorporation of gelatin to improve their cytocompatibility. The amphoteric nature of the gelatin was exploited and the gelatin was adsorbed to the negatively charged PLLA/PSS and positively charged PLLA/PAH at pH=3.4 and 7.4, respectively. XPS and water contact angle data indicated that the gelatin adsorption at pH=3.4 resulted in much higher surface coverage by gelatin than at pH=7.4. All the modified PLLA surfaces became more hydrophilic than the virgin PLLA. Chondrocyte culture was used to test the cell attachment, cell morphology and cell viability on the modified PLLA substrates. The results showed that the PAH and PSS modified PLLA exhibited better cytocompatibility than virgin PLLA, and the incorporation of the gelatin on these modified PLLA substrates further improved their cytocompatibility, with the PLLA/PSS substrate treated with the gelatin at pH=3.4 being the best, exceeding the chondrocyte compatibility of the tissue culture polystyrene.     

Immobilization and characterization of gamma-aminobutyric acid on gold surface

gamma-Aminobutyric acid (GABA) is one of two main inhibitory neurotransmitters in the central nervous system that plays an important role in neuronal function and dysfunction. Immobilization of GABA molecules on a rigid surface in an ordered fashion will provide an opportunity to understand some of the fundamental properties related to its structure and function. In this study, we report a novel strategy for immobilization of bioactive GABA on gold substrate. GABA was immobilized in three consecutive steps, namely gold substrate amination, dextran covalent attachment, and GABA immobilization. Surface chemistry was verified at each step using XPS and FTIR. Bioactivity of GABA immobilized on the gold surface was studied using atomic force microscopy to reveal antigen-antibody binding. Nonspecific protein adsorption on the bioactive surface was analyzed quantitatively using anti-GABA antibody and an enzyme linked nonspecific anti-immunoglobulin-G antibody in an ELISA assay. GABA functionalized surface has high affinity for anti-GABA, while showing significantly low affinity for nonspecific anti-IgG antibody. All these data support the presence of a bio-functional immobilized GABA on the gold surface. In conclusion, we report a novel technique for immobilizing bioactive GABA molecules in an orderly fashion on gold substrates.     

Soft-tissue response to silicone and poly-L-lactic acid implants with a periodic or random surface micropattern

Tissue reaction to biomaterials is dependent on properties such as surface topography. The aim of this study was to evaluate the tissue reaction around implants with different surface topographies. We made coin-shaped silicone and poly-L-lactic acid (PLLA) implants with double-sided parallel microgrooves (depth 1.0 microm; width 10.0 microm) and random roughness on a micrometer scale. The control implants were smooth. These implants were inserted into subcutaneous pockets created on the flanks of goats. After 1, 3, or 12 weeks, the goats were sacrificed and the implants retrieved and histologically processed. Light microscopic evaluation revealed the formation of fibrous tissue capsules around all implant materials. The PLLA did not visibly degrade during the study period. Histomorphometric analyses were performed on capsule thickness, capsule quality, and on the implant-tissue interface quality. Compared with the silicone implants, the capsules around the PLLA implants showed significantly better capsule quality. Compared to the smooth implants, the capsules around the microgrooved implants were thicker, but the capsules around the roughened implants were thinner. However, randomly roughened implant surfaces generally elicited a stronger and more prolonged inflammatory reaction compared to smooth and microgrooved implant surfaces. We conclude that the application of microgrooves or random surface roughness to polymer implants apparently does not have beneficial effects on peri-implant tissue healing.     

Ex vivo mechanical evaluation of carbonate apatite-collagen-grafted porous poly-L-lactic acid membrane in rabbit calvarial bone

Appropriate mechanical recovery is an important parameter in successful restoration of skeletal defects. Carbonate apatite and type I atelocollagen mixture (CAp) was grafted on a porous poly-L-lactic acid (PLLA) membrane to produce a CAp bilayered PLLA membrane (CAp+PLLA). After implantation, regional mechanical change in the membrane was investigated in rabbit calvarial bone defects. Dynamic viscoelasticity and elastic modulus of the implanted specimen were measured after 2, 4, 8, 12, 16, 26, and 52 weeks. The modulus of the peripheral part was higher than that of the central part of the implanted area, whereas the central part demonstrated a gradual increase. This phenomenon indicates that regeneration initially occurs from the periphery of the calvarial bone. After 26 weeks, stiffness of the central part became similar to that of the periphery in the CAp+PLLA-implanted area. According to this result, measuring viscoelasticity of an implanted biodegradable material would be a useful method to determine degrees of regeneration and replacement of an implanted region.     

The effect of poly-L-lactic acid with parallel surface micro groove on osteoblast-like cells in vitro.

In this study we evaluated the behavior of rat bone marrow (RBM) cells on microgrooved poly-L-lactic acid (PLA) and polystyrene (PS) surfaces. The applied groove depth was 0.5, 1.0 or 1.5 microns, with a groove and ridge width of 1, 2, 5 or 10 microns. Scanning electron microscopical examination showed that a collagen-rich mineralized layer of extracellular matrix (ECM) was deposited. Alignment of the cells and matrix to the surface grooves was observed as described before. Quantitative evaluation, using a tetracycline labeling assay, revealed that more mineralized ECM was formed on the PLA than on the PS. Further, PLA surfaces with a groove depth of 1.0 micron and groove widths of 1 and 2 microns induced most mineralized ECM. Finally, alkaline phosphatase activity was also higher on most microgrooved PLA surfaces, compared with the other materials. On the basis of these observations, we concluded that microtextured surfaces are able to influence the differentiation of osteoblast-like cells and the deposition of mineralized matrix. Probably, this phenomenon can be used to increase the bone regeneration around oral implants.     

Immobilization of a nonsteroidal antiinflammatory drug onto commercial segmented polyurethane surface to improve haemocompatibility properties

A method has been developed in which a layer of p-aminosalicylic acid (4-amino-2-hydroxybenzoic acid) (PAS), a water soluble pharmaceutical compound of the nonsteroidal anti-inflammatory drug (NSAID) class with antiaggregant platelet activity, is covalently immobilized onto a segmented polyurethane, Biospan (SPU) surface. Thus, SPU surfaces were modified by grafting of hexamethylenediisocyanate. and the free isocyanate remaining on the SPU surface were then coupled through a condensation reaction to amine groups of p-aminosalicylic acid. The bonding of PAS from aqueous solution onto SPU surface was studied by ATR-FTIR. UV and fluorescence spectroscopy. Plateau levels of coupled PAS were reached within 1.2 microg/cm2 using PAS solution concentrations of 1mg/ ml. The surface wettability of the polymeric films measured by contact angle indicate that the introduction of the PAS turns the surface more hydrophilic (theta(water) = 43.1 +/- 2.1) relatively to the original SPU films (theta(water) = 70.3 +/- 1.9). The in vitro albumin (BSA) adsorption shows that the PAS-SPU films adsorb more BSA (250/microgmm2) than the original SPU (112 microg mm2). Thrombogenicity was assessed by measuring the thrombus formation and platelet adhesion of the SPU containing PAS relatively to nonmodified SPU surfaces. The polymeric surfaces with immobilized PAS had better nonthrombogenic characteristics as indicated by the low platelet adhesion, high adsorption of albumin relatively to fibrinogen and low thrombus formation, making them potentially good candidates for biomedical applications.     

The synthesis of tenuazonic acid o‐carboxymethyl oxime and its conjugation to macromolecules

The o‐carboxymethyl oxime derivative of the mycotoxin and phytotoxin, tenuazonic acid, has been synthesized and characterized by ¹H‐NMR (nuclear magnetic resonance) and IR spectroscopy and mass spectrometry. The derivative contains a carboxylic acid moiety which has been conjugated to bovine serum albumin and a modified bovine serum albumin, using the mixed anhydride method, in toxin‐to‐protein ratios of 15:1 and 30:1 respectively. Isoelectric focusing was used to demonstrate that the conjugation process had been successfully achieved. The two conjugates appear to be suitable for the preparation of either polyclonal or monoclonal antibodies to tenuazonic acid for use in the development of immunoassays for this toxin.     

Covalent bonding of lysine to EVAL membrane surface to improve survival of cultured cerebellar granule neurons

Polylysine is a commonly used coating material in the preparation of neuronal cultures. In the present study, poly (ethylene-co-vinyl alcohol) (EVAL) membranes were modified by the covalent bonding of lysine via isocyanation of surface hydroxyl groups to improve cell behavior in cultured cerebellar granule neurons from 7-day-old Wistar rats. Cell survival and death ratio were assayed by MTT reduction activity and lactate dehydrogenase release, respectively. Cell morphology and neurite growth were observed by a scanning electron microscope. It was found that immobilizing lysine onto the EVAL membranes could improve neuronal MTT reduction activity and delay the death rate of neurons. In addition, neurons seeded on the lysine-immobilized EVAL membrane were able to regenerate with the formation of an extensive neuritic network, indicating that the surface modification on the EVAL membrane should be useful for culturing of neurons. Furthermore, the influence exerted by the modification of different amino acids (glycine, arginine and ornithine) onto the EVAL membranes on the neuronal behavior were investigated. We found that the effect of the terminal primary amine of the side chain of the basic amino acids on the neuronal behavior should be taken into account because the immobilized glycine molecules did not improve neuronal cultures. In order to interpret the phenomenon further, in the surface modification process, both the two amino groups of lysine were designed to react with the EVAL membrane surface to form a cyclic structure. On such a surface, neuronal MTT reduction activity was decreased and neuronal death was not delayed. The result shows that the lysine molecules immobilized on the EVAL membrane surface can mediate cellular response to promote neuronal cell survival and guidance of neuritic processes, indicating a delicate interaction of neuron with lysine molecules on the EVAL membrane surface.     

Immobilization of bisphosphonates on surface modified titanium

The efficiency of surface modifications on the immobilization of bisphosphonates on titanium was investigated with Ca-ion implantation and thin hydroxyapatite coatings. The ALP activity of osteoblastic cells and the inhibitory effects on the initial adherence of P. gingivalis were also evaluated using bisphosphonate-immobilized titanium. X-ray photoelectron spectroscopy analysis suggested that titanium surfaces modified with Ca-ion implantation and thin hydroxyapatite coatings caused the immobilization of bisphosphonate on titanium plates. The ALP activity of osteoblastic cells cultured on plates immobilized with bisphosphonate was almost the same as that of cells cultured on titanium plates, indicating that the bisphosphonate-immobilization showed no toxic effect on osteoblastic cells, and that it provides a favorable micro-environment with osteogenetic ability. Data of the adherence of oral bacteria showed that a bisphosphonate-immobilized titanium surface inhibited the initial adherence of P. gingivalis. These results indicate that the immobilization of bisphosphonates on titanium modified with Ca-ion implantation and thin hydroxyapatite coatings are useful for dental implants.     

左旋聚乳酸羟基磷灰石材料上人牙周膜细胞的生长

BACKGROUND: In constructing tissue-engineered periodontium in vitto, the effective combination of seed cells with scaffold materials is the key to promote the quality of tissue-engineered periodontium, in which human periodontal ligament cells are commonly used. OBJECTIVE: To explore the growth of human periodontal ligament cells on the poly-L-lactic acid hydroxyapatite. METHODS: Human periodontal ligament cells were isolated and cultured in vitro, and passage 3 cells were chosen to be randomly divided into two groups: cells cultured alone as control group, and cultured with poly-L-lactic acid hydroxyapatite as experimental group. After 1, 2 and 3 days, alkaline phosphatase activity and expression of type III collagen in the two groups were detected, and the cell growth curve was depicted using MTT method. RESULTS AND CONCLUSION: By immunohistochemical staining, cultured cells were positive for vimentin and alkaline phosphatase staining and negative for anti-keratin staining, indicating that the cells were identified as human periodontal ligament cells. By MTT method, there was no significant difference in the absorbance value of two groups at different time points (P > 0.05). And after 1, 2 and 3-day co-culture, the alkaline phosphatase activity levels showed no significant difference between two groups (P > 0.05). Besides, no significant difference in the absorbance value of type III collagen was found in the two groups (P > 0.05). To conclude, the human periodontal ligament cells can grow and proliferate well on the poly-L-lactic acid hydroxyapatite scaffold with no cytotoxicity.     

Immobilization of L-asparaginase on the microparticles of the natural silk sericin protein and its characters

The natural silk sericin recovered from Bombyx mori silk waste by the degumming processing in the high-temperature and high-pressure is a macromolecular protein. Amino acid composition and molecular weight range of the sericin protein as a vector for enzyme immobilization were investigated. The silk sericin protein with different molecular mass from 50 to 200 kDa was poorly soluble microparticles with an average size of about 10 microm. Anti-leukemic enzyme L-asparaginase (L-ASNase) was covalently conjugated on the microparticles of the sericin protein. The immobilized L-ASNase on the natural support by cross-linking with glutaraldehyde maintained 62.5% of the original activity of the enzyme. The Km of sericin-conjugates was 8 times lower than that of native L-ASNase. The bioconjugation of L-ASNase widened the optimum reactive temperature range of the enzyme. The immobilized L-ASNase showed significantly higher stability when the temperature raised to 40-50 degrees C, it also showed preferable resistance to trypsin digestion as compared with native enzyme. The results are discussed regarding the possible explanations of sericin-induced enzyme stability, as well as the possible applications of immobilized L-ASNase research.     

Exploiting order effects to improve the quality of decisions

Objective

To examine the effect of ordering information in a patient decision aid (PtDA) about treatments for obstructive sleep apnea (OSA).

Methods

We recruited 643 individuals to imagine that they had been diagnosed with OSA and to choose between treatment options. A value clarification exercise was used to determine which attributes of treatment mattered most to each individual. Before deciding on their preferred treatment option, we randomly assigned participants to view information with attributes in: a pre-specified order (Group 1), order of what mattered most last (Group 2), and first (Group 3).

Results

Of the 510 participants who provided usable results, viewing information that mattered most first was associated with choosing the treatment option most concordant with their informed values. The order effect was most pronounced in younger individuals.

Conclusions

In this study of hypothetical patients, order effects were found to improve the information patients focussed on, potentially improving the quality of their decisions.

Practice implications

The order of information presented in a PtDA can inadvertently influence patients’ choices. By tailoring information order for each patient, developers cannot only overcome this dilemma, but also make it simpler for patients to choose the option that is best for them.     

Immobilized heparin and its anti-coagulation effect on polysulfone membrane surface

Polysulfone has been widely used as hemodialysis membrane material because of its excellent physiochemical performance. There is still a need to further improve its anti-coagulation property in clinical practice. In this work, we covalently immobilized heparin onto polysulfone membrane to improve its anti-coagulation performance. Low temperature plasma technique with environmentally friendly nitrogen as the gas source, as well as N-ethyl-N′-[3-dimethylaminopropy] carbodiimide hydrochloride/hydroxy-2,5-dioxopyrolidine-3-sulfonicacid sodium chemistry were utilized to immobilize heparin onto the surface of polysulfone membrane. X-ray photoelectron spectroscopy, attenuated total reflectance Fourier-transform infrared spectroscopy, as well as water contact angle results confirmed successful binding of heparin to the membrane surface. Only slight permeability differences were observed between the immobilized surface and the unmodified surface, while the polysulfone membrane had become more hydrophilic after immobilization. The blood coagulation time was greatly prolonged after modification and less platelets adhesion was observed on the heparin immobilized surface. Also, compared with heparin injection doses in clinical, the heparinized process in our work consumed less heparin. Our study suggests that the immobilized heparin has local anti-coagulation effect, while reducing the doses.     

Design of bioinspired polymeric materials based on poly(D,L-lactic acid) modifications towards improving its cytocompatibility

To design novel bioinspired polymeric material, poly(D,L-lactic acid) (DL-PLA) was on the base and modified in the bulk. Firstly, maleic anhydride (MA) groups were introduced to the side chain of DL-PLA by the way of melting free radical copolymerization using benzoyl peroxide as an initiator. Then, to neutralize the acid generated during DL-PLA degradation, aliphatic diamine was immobilized by the N-acylation of anhydrides with butanediamine. As the following stage, adhesive peptides Arg-Gly-Asp-Ser (RGDS) were grafted into the backbone of DL-PLA by using carbodiimide as a coupling agent, in order to endow DL-PLA with bioactivity and biospecificity. The characterizations of the obtained polymers were by the means of GPC-MALLS, FTIR, (13)C NMR and XPS to explore the structures and rhodamine-carboxyl interaction method, ninhydrin reaction and amino acid analyzer to determine the content of MA, butanediamine, and RGDS, respectively, followed the test of pH changes during degradation in distilled water (pH = 6.45). Finally, the osteoblast behavior on different DL-PLA based films was investigated and the results indicated that the introduction of diamine could promote cell attachment and viability, and the incorporation of RGDS further improved its cytocompatibility. The synthetic DL-PLA based bioinspired material may have potentials for tissue engineering and other biomedical applications.     

The effect of fluorinated surface modifying macromolecules on the surface morphology of polyethersulfone membranes

Polyethersulfone (PES) has been recently adopted for membrane materials in applications such as ultrafiltration and haemodialysis. As a biomaterial, the factors which affect the blood compatibility of PES membranes include surface energetics, hydrophobicity, and surface morphology. Surface fluorination of materials has been found to create surfaces with improved blood compatibility and chemical stability. One novel approach to generating fluorinated polymer surfaces has included the use of fluorinated surface modifying macromolecules (SMMs). These macromolecules have been reported to establish fluorinated functional groups at surfaces of polymeric materials without significantly affecting the physical properties of the base polymer. However, to date there has been relatively little information published on the nature of the surface structure for PES materials containing these SMMs. In this study, synthesized SMMs with varying chemical compositions were characterized and blended with PES, and fabricated into flat sheet membranes. The bulk thermal transitions of PES materials were not significantly altered by the addition of 4 wt% SMMs. Contact angle data showed that the addition of SMMs in PES created more hydrophobic surfaces, accompanied by an increase in surface heterogeneity. X-ray photoelectron spectroscopy studies confirmed the presence of elemental fluorine at the surface. Through microscopy studies, it was shown that surface modification was achieved by the migration of SMM concentrated microdomains to the air-membrane interface. The generated microdomains (approximately 1-2 μm in diameter) are dispersed within the top 8 μm of the surface. The concentration of microdomains was gradually depleted from the surface to the bulk of the membrane. A schematic of the morphology for SMMs within the PES membrane surface was proposed.     

The effect of fluorinated surface modifying macromolecules on the surface morphology of polyethersulfone membranes

Polyethersulfone (PES) has been recently adopted for membrane materials in applications such as ultrafiltration and haemodialysis. As a biomaterial, the factors which affect the blood compatibility of PES membranes include surface energetics, hydrophobicity, and surface morphology. Surface fluorination of materials has been found to create surfaces with improved blood compatibility and chemical stability. One novel approach to generating fluorinated polymer surfaces has included the use of fluorinated surface modifying macromolecules (SMMs). These macromolecules have been reported to establish fluorinated functional groups at surfaces of polymeric materials without significantly affecting the physical properties of the base polymer. However, to date there has been relatively little information published on the nature of the surface structure for PES materials containing these SMMs. In this study, synthesized SMMs with varying chemical compositions were characterized and blended with PES, and fabricated into flat sheet membranes. The bulk thermal transitions of PES materials were not significantly altered by the addition of 4 wt% SMMs. Contact angle data showed that the addition of SMMs in PES created more hydrophobic surfaces, accompanied by an increase in surface heterogeneity. X-ray photoelectron spectroscopy studies confirmed the presence of elemental fluorine at the surface. Through microscopy studies, it was shown that surface modification was achieved by the migration of SMM concentrated microdomains to the air-membrane interface. The generated microdomains (approximately 1-2 microm in diameter) are dispersed within the top 8 microm of the surface. The concentration of microdomains was gradually depleted from the surface to the bulk of the membrane. A schematic of the morphology for SMMs within the PES membrane surface was proposed.