Surface Modification Of Polystyrene Research Articles

Surface Modification of Polystyrene with Boronic Acid for Immunoaffinity-Based Cell Enrichment.

Obtaining an enriched and phenotypically pure cell population from heterogeneous cell mixtures is important for diagnostics and biosensing. Existing techniques such as fluorescent-activated cell sorting (FACS) and magnetic-activated cell sorting (MACS) require preincubation with antibodies (Ab) and specialized equipment. Cell immunopanning removes the need for preincubation and can be done with no specialized equipment. The majority of the available antibody-mediated analyte capture techniques require a modification to the Abs for binding. In this work, no antibody modification is used because we take advantage of the carbohydrate chain in the Fc region of Ab. We use boronic acid as a cross-linker to bind the Ab to a modified surface. The process allows for functional orientation and cleavable binding of the Ab. In this study, we created an immunoaffinity matrix on polystyrene (PS), an inexpensive and ubiquitous plastic. We observed a 37% increase in Ab binding compared with that of a passive adsorption approach. The method also displayed a more consistent antibody binding with 17 times less variation in Ab loading among replicates than did the passive adsorption approach. Surface topography analysis revealed that a dextran coating reduced nonspecific antibody binding. Elemental analysis (XPS) was used to characterize the surface at different stages and showed that APBA molecules can bind upside-down on the surface. While upside-down antibodies likely remain functional, their elution behavior might differ from those bound in the desired way. Cell capture experiments show that the new surface has 43% better selectivity and 2.4-fold higher capture efficiency compared to a control surface of passively adsorbed Abs. This specific surface chemistry modification will allow the targeted capture of cells or analytes with the option of chemical detachment for further research and characterization.

Tethered primary hepatocyte spheroids on polystyrene multi-well plates for high-throughput drug safety testing

Hepatocyte spheroids are useful models for mimicking liver phenotypes in vitro because of their three-dimensionality. However, the lack of a biomaterial platform which allows the facile manipulation of spheroid cultures on a large scale severely limits their application in automated high-throughput drug safety testing. In addition, there is not yet a robust way of controlling spheroid size, homogeneity and integrity during extended culture. This work addresses these bottlenecks to the automation of hepatocyte spheroid culture by tethering 3D hepatocyte spheroids directly onto surface-modified polystyrene (PS) multi-well plates. However, polystyrene surfaces are inert toward functionalization, and this makes the uniform conjugation of bioactive ligands very challenging. Surface modification of polystyrene well plates is achieved herein using a three-step sequence, resulting in a homogeneous distribution of bioactive RGD and galactose ligands required for spheroid tethering and formation. Importantly, treatment of polystyrene tethered spheroids with vehicle and paradigm hepatotoxicant (chlorpromazine) treatment using an automated liquid handling platform shows low signal deviation, intact 3D spheroidal morphology and Z’ values above 0.5, and hence confirming their amenability to high-throughput automation. Functional analyses performance (i.e. urea and albumin production, cytochrome P450 activity and induction studies) of the polystyrene tethered spheroids reveal significant improvements over hepatocytes cultured as collagen monolayers. This is the first demonstration of automated hepatotoxicant treatment on functional 3D hepatocyte spheroids tethered directly on polystyrene multi-well plates, and will serve as an important advancement in the application of 3D tethered spheroid models to high throughput drug screening.

Antibacterial properties of angle-dependent nanopatterns on polystyrene

Surface modification of polystyrene by a KrF pulse excimer UV laser under the angles of incidence of the laser beam of 0, 22.5 and 45° was proposed in this paper. The influence of the angle of incidence, laser fluence, number of pulses and a deposition of a thin gold layer on the physical and chemical properties of the surface was studied closely. Changes in the surface morphology, the formation of the periodic surface structures as well as the dependence of their dimension on the angle of incidence of the laser beam were determined by Atomic force microscopy and Scanning electron microscopy. Changes in the surface chemistry were studied by X-ray Photoelectron spectroscopy, which revealed a significant increase of oxygen concentration for all laser treated samples and also by electrokinetic analysis to further clarify the surface chemistry and charge changes occurring during the laser treatment. An optimal conditions for antibacterial surface construction was found on the basis of combination of silver nanolayer and PS treated under angle of laser beam incidence 45°. The potential application of laser-treated polystyrene foils can be found mainly in the biotechnological industry, as well as in various other fields dealing with surface modification and micro-patterning of solids.

Construction and Properties of Ripples on Polymers for Sensor Applications

Surface modification of polystyrene and polyethylene naphthalate by a KrF pulse excimer UV laser under the angles of incidence of the laser beam in the range of 0 to 60° with a step of 7.5° was studied in this paper. The influence of the angle of incidence on the period of the resulting surface structures and the modified refractive index of the substrates was determined with all the other parameters of the laser radiation held constant. All data was acquired on the basis of surface analysis. Atomic force microscopy was used to study the morphological changes in the laser treated samples and to determine the period of the ripple-like surface structures, from which the modified refractive index was subsequently calculated. Selected samples were metallized with gold with aim to determine the influence of patterned substrate on consequently formed nanolayer. These information may be useful for consequently constructed SERS system based on ripple-metal system.

Surface Modification of Polystyrene with O Atoms Produced Downstream from an Ar/O2 Microwave Plasma

Because discarded polystyrene (PS) is little affected by degrading agents, PS was treated with a remote microwave (MW) plasma discharge of an Ar/O2 mixture in the absence of radiation to increase wettability and introduce functional groups which make the waste more liable to degradation and useful for technological applications. X-ray photoelectron spectroscopy (XPS) detected decreases in the aromatic sp2 and aliphatic sp3 carbons with treatment and, initially, increases in C–O and carbonyl groups, present in the formation of ethers, epoxides, alcohols, ketones and aldehydes. At longer treatment times, ester, O–C=O; carbonate-like, O–(C=O)–O; and anhydride, O=C–O–C=O; moieties are observed with an overall oxygen saturation level of 23.6 ± 0.9 at% O. Atomic Force Microscopy (AFM) measurements detected little change in surface roughness with treatment time. Advancing water contact angle decreased by ca. 50% compared to pristine PS indicating an increase in hydrophilicity because of oxidation. Washing the treated samples in deionized water decreased the oxygen concentrations at the saturation treatment times down to 18.6 ± 1 at% O due to the washing away of a weak boundary layer.

Simultaneous process of surface modification and sterilization for polystyrene dish

Surface modification of polystyrene (PS) dish used for cell culture substrate is necessary to enhance cell adhesion and spreading. Generally, plasma treatment is employed for enhancement of hydrophilic surface at the PS dish surface, and sterilization treatment of the PS dish is performed after the plasma treatment. Simultaneous process of the surface modification and sterilization is required, and we have investigated surface modification effects on the PS dish in a sterilization bag by using active oxygen species (AOS) generated via ultraviolet (UV) lamps. It is considered that excited oxygen molecules (1O2) as well as ozone (O3) generated via the UV lamps greatly affect surface modification of the PS dish in the sterilization bag.Cell adhesion and spreading characteristics of the modified PS dish by the AOS were almost the same level as those onto the commercially available PS dish. In addition, homogeneity of the surface modification is slightly enhanced compared to that of the commercially available PS dish. As microbes are sterilized by the AOS exposure in sterilization bag, surface modification of the PS dish is simultaneously achieved with the sterilization.

The Effect of Substrate Temperature on Surface Modification of Polystyrene by using Nitrogen Plasma

Studies on the effect of substrate temperature on the modification process of a thin layer of polystyrene samples deposited on glass by using spin coating technique have been conducted. The polystyrene thin film surface was modified by using nitrogen plasma generated in a vacuum reactor by a capacitive plasma generator with a frequency of 40 kHz. The substrate temperature was set by variation of 60, 70 and 80 °C during the modification process to determine the effect of substrate temperature on the level of roughness and hydrophobicity of the film. Observations were conducted by using optical microscopy, optical micro-profiler, and measuring the contact angle of liquid. The results showed a decrease in roughness due to modification at a temperature of 60 °C and 70 °C. On the other hand, the treatment at a temperature of 80 °C resulted in an increase of roughness. By measuring the contact angle, it was proven that hydrophobicity is not only influenced by the surface roughness of thin layers.

A study of diazonium couplings with aromatic nucleophiles both in solution and on a polymer surface

Diazonium coupling is a technique finding wider application to materials and biological science, for hybridization and linking processes, and for the construction of responsive surface functionality. For this reason, detailed examination of solution and surface processes was warranted, and results of such a study are reported here. The modification of polystyrene surfaces was examined as a model, and the process compared to a solution mimic using N,N-dimethylaniline. It was confirmed that solution and solid surface reactions proceed in a similar manner in terms of the chemical functionality generated, but with lower chemical efficiency and reaction times slower for the latter, in a reaction which was pH dependent. The solution process was shown to give only the trans-azo para- coupled products. Whilst there are clear similarities between the solution and surface chemistry, the efficiency of coupling at a surface is not necessarily replicated in the chemical yield of the mimicking solution processes, but nonetheless provides an alternative to other Click-type surface modifications. It should not be assumed that such couplings occur with quantitative efficiency at the surface.

Surface Modification of Polystyrene by Femtosecond Laser Irradiation

Surface Modification of Polystyrene by Femtosecond Laser Irradiation

Synthesis and Characterization of Poly(styrene-co-acrylamide) Polymers Prior to Electrospinning

Electrospun nanofibers present a new and rapidly growing research area due to their pronounced micro and nano characteristics associated with high surface area to volume ratio. Poly(styrene-co-acrylamide) and polystyrene polymers were synthesized by boiling temperature soap free emulsion polymerization in aqueous medium with potassium peroxosulphate as the initiator. The resulting polymers were dissolved in dimethylformamide and teterahydrofuran (DMF: THF) (4:1) to form polymer solutions that were electrospun into fiber mats with diameters ranging from 1.84 - 2.53 μm and 5.01 μm, respectively. The fibers were characterized by Fourier transform infrared spectroscopy (FTIR) equipped with universal ATR sampling accessory (4000 - 400 cm-1). The morphology and size were examined by a scanning electron miscroscope (SEM) and the thermal properties by thermogravimetric analysis (TGA). The FTIR spectra of the poly(styrene-co-acrylamide) revealed the presence of acrylamide on the polystyrene chain. Thus, surface modification of polystyrene with acrylamide is possible in a single step polymerization reaction prior to electrospinning.

Modification of polystyrene surface in aqueous solutions

Herein, we report our analysis of the surface modification of polystyrene (PS) when treated under ambient conditions with a common biological buffer such as phosphate buffered saline (PBS) or aqueous solutions of the ionic constituents of PBS. Attenuated total reflection Fourier transform infrared spectroscopy was used for the analysis because the resultant spectra are very sensitive to minor changes in the chemical and structural properties of PS films. In addition, ultraviolet–visible spectroscopy was applied to characterize the surface modifications of PS. Treatment with PBS resulted in the most significant chemical and structural surface modifications of the PS films, as compared with each of the solutions of the constituents of PBS, which were tested separately. A multistep mechanism for the wet modification of PS is discussed. We postulate that the observed surface modifications are the result of photo-oxidation/reduction, swelling, and conformational changes and re-arrangement of the polymer chain. The resultant surface modifications could be similar to those produced by commonly used dry processes such as plasma treatments and electron, ion or ultraviolet irradiation. We found that the modifications that occurred in PBS were more stable than those initiated by dry processes. The formation of active groups on the surface of PS can be controlled by adsorption of bovine serum albumin or thermal annealing of PS before PBS treatment. This approach provides a simple and efficient method for the surface modification of PS for biomedical applications.

Surface modification of polystyrene with the bovine serum albumin-Tween 80 complex and a forecast of biocompatibility

The surface of polystyrene was modified with the bovine serum albumin-Tween 80 complex. The adsorption of the complex and the formation of films on the surface of polystyrene were studied using the piezoelectric weighing method. The state of the modified surface was evaluated by contact angle measurements. The stability of the modifying layer was determined based on the critical interfacial energy values of the surface equilibrated with water. A conclusion was drawn that the complex can be effectively used to enhance the biocompatibility of polymer materials.

Surface modification of polystyrene by low energy hydrogen ion beam

Polystyrene was modified by low energy hydrogen ions in ultrahigh vacuum. The modified surfaces were analyzed in situ by x-photoelectron spectroscopy and ex situ by atomic force microscopy. Results revealed that 10 eV H + ion bombardment on polystyrene produces a cross-linked network film, while the polymer backbone remains intact and undesirable impurity (such as nitrogen, oxygen, etc) incorporation is eliminated. The as-prepared network film is just about 5–6 nm thick, but is highly resistant to chemical solvent. However, when 100 eV H + ion bombardment is used, the aromatic rings are seriously damaged and the surface of organic film is etched. This work suggests a new route to the preparation of ultrathin polymer network films.

Size-Selective Protein Adsorption to Polystyrene Surfaces by Self-Assembled Grafted Poly(ethylene Glycols) with Varied Chain Lengths

We report about the surface modification of polystyrene (PSt) with photoreactive alpha-4-azidobenzoyl-omega-methoxy poly(ethylene glycol)s (ABMPEG) of three different molecular weights (MWs of approximately 2, approximately 5, and approximately 10 kg/mol) and with two poly(ethylene glycol)/poly(propylene glycol) triblock copolymers (PEG-PPG-PEG) of about identical PEG/PPG ratio (80/20, w/w) and MW(PEG) of approximately 3 and approximately 6 kg/mol, all via adsorption from aqueous solutions. For ABMPEGs, an additional UV irradiation was used for photografting to the PSt. Contact angle (CA) and atomic force microscopy data revealed pronounced differences of the hydrophilicity/hydrophobicity and topography of the surfaces as a function of PEG type and concentration used for the modification. In all cases, an incomplete coverage of the PSt was observed even after modification at the highest solution concentrations (10 g/L). However, clear differences were seen between PEG-PPG-PEGs and ABMPEGs; only for the latter was a nanoscale-ordered interphase structure with an influence of MW(PEG) on the PEG density observed; after modification at the same solution concentrations, the density was significantly higher for lower MW(PEG). The adsorption of three proteins, myoglobin (Mgb), bovine serum albumin (BSA), and fibrinogen to the various surfaces was analyzed by surface plasmon resonance. Pronounced differences between the two PEG types with respect to the reduction of protein adsorption were found. At high, but still incomplete, surface coverage and similar CA, the shielding of ABMPEG layers toward the adsorption of Mgb and BSA was much more efficient; e.g., the adsorbed Mgb mass relative to that of unmodified PSt was reduced to 10% for ABMPEG 2 kg/mol while for both PEG-PPG-PEGs the Mgb mass was still around 100%. In addition, for the ABMPEG layers an effect of MW(PEG) on adsorbed protein mass-decrease with decreasing MW-could be confirmed; and the highest Mgb/BSA selectivities were also observed. A "two-dimensional molecular sieving", based on PEG molecules having a nanoscale order at the hydrophobic substrate polymer surface has been proposed, and the main prerequisites were the use of PEG conjugates which are suitable for an "end-on" grafting (e.g., ABMPEGs), the use of suitable (not too high) concentrations for the surface modification via adsorption/self-assembly, optionally the photografting on the substrate (possible only for ABMPEG), and presumably, a washing step to remove the excess of unbound PEGs. The results of this study also strongly support the hypothesis that the biocompatibility of hydrophobic materials can be very much improved by PEG modifications at surface coverages that are incomplete but have an ordered layer structure controlled by the size and steric interactions of surface-bound PEGs.

Vacuum‐ultraviolet Photochemically Initiated Modification of Polystyrene Surfaces: Chemical Changes¶,‡

ABSTRACTFourier‐Transform infrared (FTIR) spectroscopy and surface energy analysis (contact angle measurements) have been performed as a means of identification and quantification of the functionalization of polystyrene surfaces upon vacuum ultraviolet‐ (VUV‐) photochemically initiated oxidation. Photochemical oxidation was performed in the presence of water vapor and molecular oxygen using a pulsed Xe2‐excimer radiation source (λexc: 172 nm). Surface oxidation was studied as a function of two parameters: irradiation time and distance between sample and radiation source. During the first 1–2 min of irradiation, an increase of the concentrations of hydroxyl (OH) and carbonyl (C=O) groups on the surface was observed, both reaching limiting values. As expected, the rate of oxidation diminished exponentially with increasing distance between the radiation source and the surface of the polystyrene film. Changes in the surface energy due to the introduction of these polar (i.e. OH and C=O) groups were also determined. The densities of the functional groups decreased upon washing with acetonitrile, and analysis of the washing solution by means of gas chromatography‐mass spectrometry (GC‐MS) revealed the presence of a large number of products. The application of pulsed Xe2‐excimer radiation sources as a valuable alternative to conventional means (i.e. laser and plasma) for the photochemical oxidation and surface modification of polystyrene is discussed.

Vacuum-ultraviolet Photochemically Initiated Modification of Polystyrene Surfaces: Chemical Changes¶,‡

Fourier-Transform infrared (FTIR) spectroscopy and surface energy analysis (contact angle measurements) have been performed as a means of identification and quantification of the functionalization of polystyrene surfaces upon vacuum ultraviolet- (VUV-) photochemically initiated oxidation. Photochemical oxidation was performed in the presence of water vapor and molecular oxygen using a pulsed Xe2-excimer radiation source (λexc: 172 nm). Surface oxidation was studied as a function of two parameters: irradiation time and distance between sample and radiation source. During the first 1–2 min of irradiation, an increase of the concentrations of hydroxyl (OH) and carbonyl (C=O) groups on the surface was observed, both reaching limiting values. As expected, the rate of oxidation diminished exponentially with increasing distance between the radiation source and the surface of the polystyrene film. Changes in the surface energy due to the introduction of these polar (i.e. OH and C=O) groups were also determined. The densities of the functional groups decreased upon washing with acetonitrile, and analysis of the washing solution by means of gas chromatography-mass spectrometry (GC-MS) revealed the presence of a large number of products. The application of pulsed Xe2-excimer radiation sources as a valuable alternative to conventional means (i.e. laser and plasma) for the photochemical oxidation and surface modification of polystyrene is discussed.

Vacuum-Ultraviolet Photochemically Initiated Modification of Polystyrene Surfaces: Chemical Changes

Fourier-Transform infrared (FTIR) spectroscopy and surface energy analysis (contact angle measurements) have been performed as a means of identification and quantification of the functionalization of polystyrene surfaces upon vacuum ultraviolet- (VUV-) photochemically initiated oxidation. Photochemical oxidation was performed in the presence of water vapor and molecular oxygen using a pulsed Xe2-excimer radiation source (lambda(exc): 172 nm). Surface oxidation was studied as a function of two parameters: irradiation time and distance between sample and radiation source. During the first 1-2 min of irradiation, an increase of the concentrations of hydroxyl (OH) and carbonyl (C=O) groups on the surface was observed, both reaching limiting values. As expected, the rate of oxidation diminished exponentially with increasing distance between the radiation source and the surface of the polystyrene film. Changes in the surface energy due to the introduction of these polar (i.e. OH and C=O) groups were also determined. The densities of the functional groups decreased upon washing with acetonitrile, and analysis of the washing solution by means of gas chromatography-mass spectrometry (GC-MS) revealed the presence of a large number of products. The application of pulsed Xe2-excimer radiation sources as a valuable alternative to conventional means (i.e. laser and plasma) for the photochemical oxidation and surface modification of polystyrene is discussed.

Effects of the Addition of Hydrogen in the Nitrogen Cold Plasma: The Surface Modification of Polystyrene

Polystyrene, a polymer extensively used in the biomedical field, causes a problem for some applications because of its surface hydrophobicity. Nitrogen plasma could transform this shortage through polar group attachment. To understand the role of hydrogen during surface functionalization in the nitrogen cold plasma, the effects of the nitrogen and the mixture of N2/H2 plasma are investigated by both the examinations of the densities of attached amine groups and the in-situ diagnostic analyses such as optical emission spectroscopy and mass spectrometry. An increase of functionalization has been proved to be controlled by the gaseous NH radical formation when H2 is added.

Surface modification of polystyrene and poly(methyl methacrylate) by active oxygen treatment

We examined the possibility of the surface modification of hydrophobic polystyrene (PS) and poly(methyl methacrylate) (PMMA) by ozone aeration, UV irradiation and combination of ozone aeration and UV irradiation (ozone/UV) in distilled water. The surface states of treated films and particles were investigated by means of contact angle, atomic force microscopy (AFM) and FT-IR measurements. According to the contact angle measurements, the values of the contact angle of ultrapure water on treated PS films decreased with an increase in the elapsed time of the treatments. The most remarkable decrease was seen in ozone/UV treatment. On the other hand, the contact angle on treated PMMA films slightly increased to an equal extent after three types of treatments. The film and the particle surfaces of PS with aromatic rings were found to be well modified with hydroxyl (OH) and carbonyl (C=O) groups and to give the most remarkable effects in ozone/UV treatments, whereas those of PMMA with no aromatic ring were hardly modified, merely resulting in a slight disorder in their surface roughness. The experimental results on surface modification of PS and PMMA revealed that the ozone/UV treatment in distilled water is usable as one of the useful techniques for the surface modification of polymers with aromatic rings.

Surface modification of polystyrene by K ion implantation

Surface modifications of polystyrene (PS) by potassium (K) ion implantation and its characterization have been carried out to investigate the mechanism of addition of a hydrophilic function. The depth distribution of K atoms was evaluated by Rutherford backscattering spectroscopy (RBS). The phenomenon of decrease of contact angle was found to be related to the increase of K atomic concentration in an earlier X-ray photoelectron spectroscopy study [1]. TRIM-98 code [2] predicts a Gaussian-like distribution K atom in a PS matrix. To examine the unexpected appearance of K atoms near or on the PS surface, K ion implantation in PS was performed at energies of 50 and 150 keV with doses ranging from 5×10 15 to 5×10 16 ions/cm 2, and the composition in the K implanted layers of PS has been investigated by RBS. The depth distribution of K atoms showed a Gaussian distribution for a low dose and is in a good agreement with the theoretical distribution calculated by TRIM. At an intermediate dose, the K depth profile changed to a trapezoidal distribution. At a high dose, K enrichment was found at the surface and shows different phenomena according to accelerator energy between 50 and 150 keV. The mechanism of enrichment of K atoms is discussed in relation to TRIM code results, varying the parameters of density, surface binding energy and replacement energy.