Hydrophilic Polyacrylamide Research Articles

Unusual presentation of a late complication in a polyacrylamide gel-injected breast

Implant migration is a known complication of hydrophilic polyacrylamide gel (PAAG) mammoplasty. We report the case of a female patient with an undisclosed history of bilateral breast augmentation with PAAG injections 10 years ago. The patient presented with abdominal pain and rapid gel migration into the abdominal and pelvic walls after sneezing. Computed tomography and sonography were performed, but the results were inconclusive. The diagnosis of PAAG migration was not made until the patient complained of progressive shrinkage of her right breast and disclosed the history of PAAG mammoplasty. A subsequent magnetic resonance imaging study confirmed the diagnosis. Gel migration was successfully treated using endoscopic lavage and breast debridement. Familiarity with the radiological features of PAAG migration and a thorough examination of the patient's history are mandatory for the accurate diagnosis of this complication.

Neutral hydrophilic coatings for capillary electrophoresis prepared by controlled radical polymerization

In the present study, porous silica particles as well as impervious fused-silica wafers and capillary tubes were modified with hydrophilic polymers (hydroxylated polyacrylamides and polyacrylates), using a surface-confined grafting procedure based on atom transfer radical polymerization (ATRP) which was also surface-initiated from α-bromoisobutyryl groups. Initiator immobilization was achieved by hydrosilylation of allyl alcohol on hydride silica followed by esterification of the resulting propanol-bonded surface with α-bromoisobutyryl bromide. Elemental analysis, IR and NMR spectroscopies on silica micro-particles, atomic force microscopy, ellipsometry and profilometry on fused-silica wafers, as well as CE on fused-silica tubes were used to characterize the chemically modified silica substrate at different stages. We studied the effect of monomer concentration as well as cross-linker on the ability of the polymer film to reduce electroosmosis and to prevent protein adsorption (i. e., its non-fouling capabilities) and found that the former was rather insensitive to both parameters. Surface deactivation towards adsorption was somewhat more susceptible to monomer concentration and appeared also to be favored by a low concentration of the cross-linker. The results show that hydrophilic polyacrylamide and polyacrylate coatings of controlled thickness can be prepared by ATRP under very mild polymerization conditions (aqueous solvent, room temperature and short reaction times) and that the coated capillary tubes exhibit high efficiencies for protein separations (0.3–0.6 million theoretical plates per meter) as well as long-term hydrolytic stability under the inherently harsh conditions of capillary isoelectric focusing. Additionally, there was no adsorption of lysozyme on the coated surface as indicated by a complete recovery of the basic enzyme. Furthermore, since polymerization is confined to the inner capillary surface, simple precautions (e.g., solution filtration) during the surface modification process are sufficient to prevent capillary clogging.

Phase transition in hydrogels of thermoresponsive semi-interpenetrating and interpenetrating networks of poly(N,N-diethylacrylamide) and polyacrylamide

Temperature-induced phase transition in hydrogels of semi-interpenetrating (SIPNs) and interpenetrating (IPNs) polymer networks of thermoresponsive poly(N,N-diethylacrylamide) (PDEAAm) and hydrophilic polyacrylamide (PAAm) was studied by a combination of 1H NMR spectroscopy, small-angle neutron scattering (SANS) and DSC. The effect of various network composition and reverse sequence in the preparation procedure of the network on the volume phase transition was examined. Transition temperature linearly increased with the content of PAAm component in SIPNs and IPNs. SANS results revealed in investigated SIPN and IPN hydrogels two types of regions (aggregates), small and large. At temperature above the phase transition the small and large regions are related to compact multi-chain aggregates with smooth and fuzzy surface, respectively. From NMR results it follows that the individual polymer groups participated in the transition to various extent dependently on the type of hydrogel preparation. We found that parameters of the phase transition are tunable not only by composition of the SIPNs and IPNs but also by the preparation process. A certain portion of water bound in globular structures and a slow exchange regime between “bound” and “free” water were established by NMR methods for all investigated SIPNs and IPNs hydrogels.

Self-assembling transition behavior of a hydrophobic associative polymer based on counterion and pH effects

Abstract The hydrophobically associating cationic polyacrylamides (C-HAPAM), containing a major part of hydrophilic polyacrylamide backbones and a minor part of ionic hydrophobic groups, i.e. N,N′-dimethyl octadeyl allyl ammonium chloride (DOAC), were synthesized. The self-assembling behaviors of the C-HAPAM molecules in water under different concentrations and pH values were investigated in detail and disclosed by rheological tests, dynamic light scattering (DLS), zeta potential, scanning electron microscope (SEM), and atomic force microscope (AFM). The critical aggregate concentration (CAC) for C-HAPAM was about 0.42 wt% and a solution-sol–gel appearance transition has been observed for C-HAPAM aqueous solutions with increasing concentration. Rheological tests demonstrated a pH reversible sol–gel transition when the pH was regulated from its original value of 7.45 to the weak alkaline value of 9.87 by adding NaOH and then switched back to 5.28 by adding HCl. The SEM, AFM and DLS results revealed that the sol–gel transition was actually attributed to the fiber-network aggregate structure transition. The mechanism of above pH responsive self-assembling behavior transition was explained by the remarkable counterion effect of OH−. Specifically, OH− was additionally capable of H-bonding with surrounding water molecules which promoted the solvation of C-HAPAM and induced thick hydration layer. Then, the hydrated layer led to the increment of zeta potential and volume expansion of C-HAPAM molecule which in turn strongly enhanced the viscosity of the solution. The strong counterion effect of OH− and the inter-molecular hydrophobic association interactions of C-HAPAM collectively triggered the formation of joints and hence the network structure transition, i.e. sol–gel transition.

Temperature-induced phase transition in hydrogels of interpenetrating networks of poly(N-isopropylacrylamide) and polyacrylamide

Collapse transition in hydrogels of interpenetrating polymer networks (IPNs) of thermoresponsive poly(N-isopropylacrylamide) (PNIPAm) and hydrophilic polyacrylamide (PAAm) was studied by a combination of NMR spectroscopy, small-angle neutron scattering (SANS) and DSC. The influence of IPNs composition and preparation on the phase transition was examined with respect to possible application of these responsive materials for drug delivery and molecular separation. Heterogeneous nature and an existence of compact globular structures with gyration radius ∼20nm was revealed in all investigated IPN hydrogels by SANS. The increasing content of PAAm component in IPNs shifts the transition toward higher temperatures and the fraction pmax of polymer units with significantly reduced mobility detected by NMR as well as the enthalpy change ΔH in DSC measurements are reduced. Reversed order of adding components during IPNs preparation also significantly affects parameters of the phase transition and collapsed structures. IPN PAAm/PNIPAm 42/58 shows substantially reduced ΔH values of the transition in comparison with IPNs PNIPAm/PAAm. A certain portion of water (HDO) bound in globular structures was established from measurements of 1H NMR spectra and spin–spin relaxation times T2 in all PNIPAm/PAAm collapsed hydrogels and in collapsed hydrogel of the neat PNIPAm, while bound water was not detected by NMR in PAAm/PNIPAm hydrogel. A slow exchange regime between bound and free water was revealed in most cases. T2 relaxation times of bound HDO are then up to one order of magnitude smaller in comparison with “free” HDO. Interestingly enough, the bound HDO appears already at temperatures when polymer segments just begin to form collapsed structures. The fraction of bound water slowly decreases with time.

An animal model of obstructive sleep apnoea-hypopnea syndrome corrected by mandibular advancement device.

The aim of the study is to establish a stable animal model of obstructive sleep apnoea-hypopnea syndrome (OSAHS) and assess the effectiveness of a mandibular advancement device (MAD). Eighteen 6-month-old male New Zealand white rabbits were randomized into three groups according to intervention: Group OSAHS, Group MAD, and a control group (n = 6 for each group). Rabbits in Group OSAHS and Group MAD were established as OSAHS model by injection, at a dose of 2 ml hydrophilic polyacrylamide gel, in the submucous muscular layer of the soft palate. Computed tomography (CT) and polysomnography (PSG) showed that OSAHS was developed successfully, the rabbits in Group MAD were fitted with the MAD and CT of the upper airway and PSG evaluated its effectiveness. Histological observation of the injection sites was conducted. CT scans showed the reduced sagittal space and cross-sectional areas of retropalatal upper airway in Group OSAHS were corrected by MAD (upper airway space in Group MAD was similar to that in the control group). The rabbits in Group OSAHS developed obvious sleep apnoea and hypopnea in supine position, with increased apnoea-hypopnea index and decreased oxygen saturation (SaO2). These were significantly improved by MAD and apnoea and hypopnea were not observed. Histology of the soft palate showed that the injected gel was entirely surrounded with connective tissues. We primarily developed an OSAHS and MAD therapy animal model with narrow oropharynx in upper airway which could be further available for OSAHS analysis.

Accelerated cell-sheet recovery from a surface successively grafted with polyacrylamide and poly(N-isopropylacrylamide)

A double polymeric nanolayer consisting of poly(N-isopropylacrylamide) (PIPAAm) and hydrophilic polyacrylamide (PAAm) was deposited on tissue culture polystyrene (TCPS) surfaces using electron beam irradiation to form a new temperature-responsive cell culture surface in which the basal hydrophilic PAAm component in the double polymeric layer promotes the hydration of the upper PIPAAm layer and induces rapid cell detachment compared to a conventional temperature-responsive cell culture surface, PIPAAm-grafted TCPS (PIPAAm-TCPS). Take-off angle-dependent X-ray photoelectron spectroscopy spectral analysis demonstrated that the grafted PIPAAm and PAAm components were located in the upper and basal regions of the double polymeric layer, respectively, suggesting that the double polymeric layer forms an inter-penetrating-network-like structure with PAAm at the basal portion of the PIPAAm grafted chains. The wettability of the temperature-responsive cell culture surfaces with the double polymeric layer tended to be more hydrophilic, with an increase in the basal PAAm graft density at a constant PIPAAm graft density. However, when the graft densities of the upper PIPAAm and basal PAAm were optimized, the resulting temperature-responsive cell culture surface with the double polymeric layer exhibited rapid cell detachment while maintaining cell adhesive character comparable to that of PIPAAm-TCPS. The cell adhesive character was altered from cell-adhesive to cell-repellent with increasing PAAm or PIPAAm graft density. The cell adhesive character of the temperature-responsive cell culture surfaces was relatively consistent with their contact angles. These results strongly suggest that the basal PAAm surface properties affect the degree of hydration and dehydration of the subsequently grafted PIPAAm. In addition, the roles of the hydrophilic component in accelerating cell detachment are further discussed in terms of the mobility of the grafted PIPAAm chains. Applications of this insight might be useful for designing temperature-responsive cell culture surfaces for achieving efficient cell culture and quick target cell detachment.

Micropatterning of hydrophilic polyacrylamide brushes to resist cell adhesion but promote protein retention.

Contrary to a prevailing concept on protein adsorption and cell adhesion, novel micropatterned polyacrylamide (PAAm) brushes that can resist cell adhesion but promote protein retention are created through patterning of ATRP initiators and surface-initiated ATRP on a polymer substrate.

PHBV/PAM Scaffolds with Local Oriented Structure through UV Polymerization for Tissue Engineering

Locally oriented tissue engineering scaffolds can provoke cellular orientation and direct cell spread and migration, offering an exciting potential way for the regeneration of the complex tissue. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) scaffolds with locally oriented hydrophilic polyacrylamide (PAM) inside the macropores of the scaffolds were achieved through UV graft polymerization. The interpenetrating PAM chains enabled good interconnectivity of PHBV/PAM scaffolds that presented a lower porosity and minor diameter of pores than PHBV scaffolds. The pores with diameter below 100 μm increased to 82.15% of PHBV/PAM scaffolds compared with 31.5% of PHBV scaffolds. PHBV/PAM scaffold showed a much higher compressive elastic modulus than PHBV scaffold due to PAM stuffing. At 5 days of culturing, sheep chondrocytes spread along the similar direction in the macropores of PHBV/PAM scaffolds. The locally oriented PAM chains might guide the attachment and spreading of chondrocytes and direct the formation of microfilaments via contact guidance.

Gel Polymer Electrolyte from Poly(Acrylamide) Coated on Natural Rubber Latex by Topology-Controlled Emulsion Polymerization for Dye Sensitized Solar Cells Application

Gel polymer electrolyte for dye sensitized solar cell application was synthesized from the hydrophilic polyacrylamide (PAM) grafted on natural rubber (NR) particles as flexible substrates at different monomer concentrations (40, 60, and 80% wt) in order to improve ionic conductivity. The seed emulsion polymerization of polyacrylamide on the surfaces of NR particles was carried out to obtain the core-shell structure using the redox couple initiator, tetraethylene pentamine (TEPA) and cumene hydroperoxide (CHP). Moreover, pyrrole monomer was polymerized on the modified rubbers via chemical oxidative polymerization by using iodine as a dopant and initiator. The synthesized materials were characterized by FTIR, grafting efficiency (% GE), degree of swelling (% DS) and ion conductivity.

Mutual interaction between embedded microgel particles and the surrounding hydrogel matrix

Polymerized crystalline colloidal array (PCCA) films, i.e., a highly ordered crystalline colloidal array of poly(N-isopropylacrylamide-co-acrylic acid) (P(NIPAM-AAc)) microgel particles embedded in a polyacrylamide (PAAm) hydrogel matrix, were prepared. The interaction between the embedded thermosensitive microgel particles and the non-thermosensitive hydrogel matrix was studied, using the Bragg diffraction of the films as a tool. The intensity and position of the diffraction peak change with temperature, from which important information on the interaction between the microgel particles and the hydrogel matrix was deduced. Our results indicate that the non-thermosensitive, hydrophilic PAAm hydrogel matrix significantly influences the thermosensitive phase transition of the embedded P(NIPAM-AAc) microgel particles. Compared with the freely dispersed microgel particles in solution, only a small change in the volume phase transition temperature of the embedded microgel particles was observed; however, the phase transition becomes less sharp. More importantly, the extent of size change is reduced significantly. On the other hand, the temperature-induced swelling/deswelling of the embedded microgel particles induces a swelling/deswelling of the surrounding hydrogel matrix, revealing that the interaction between the two components is mutual. The temperature-induced swelling/deswelling of the microgel particles is fast; in contrast, the swelling/deswelling of the hydrogel matrix is much slower. The stiffness of the hydrogel matrix affects the interaction between the two components. As the hydrogel matrix becomes stiffer, its influence on the swelling of the microgel particles becomes more prominent. On the other hand, the influence of the microgel particles on the swelling of the hydrogel matrix becomes less prominent.

Preparation and Dispersion of Polyacrylamide-Grafting Graphene

Graphene has weak interface compatibility to its solvent, and it is easy to get agglomeration in the solvent. In this paper, graphehe is modified by grafting method to improve the aqueous dispersion. Oxidized graphene is firstly prepared by modified Hummer’s method and supersonic exfoliation. Then oxidized graphene is grafted by hydrophilic polymer polyacrylamide (PAM) and deoxidized into modified graphene. The product is characterized by TEM, FTIR, Raman spectroscopy and sedimentation test. And the result demonstrates a modified graphene is successfully synthesized and its compatibility to the media is enhanced as assumption. When the ratio between PAM and graphene is 1:10, the suspension absorbance is improved as twice as common graphene’s. Meanwhile the concentration of graphene in suspension can reach 0.05mg/ml without any agglomeration.

Breast Fibromatosis after Hydrophilic Polyacrylamide Gel Injection for Breast Augmentation: a Case Report and Review of the Literature

REAST fibromatosis is a rare kind of lesion. The average incidence is about 2-4 per million every year. So far there have been about 100 cases reported altogether. In this report, we describe a case of breast fibromatosis developed after hydrophilic polyacrylamide gel (HPG) injection for breast augmentation. By reviewing the literature, the possible pathogenesis of this case and the proper treatment strategy are investigated.

Bioactive surface modification on amide-photografted poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

Collagen was chemically immobilized on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) films via hydrophilic polyacrylamide spacers, aiming to establish the bioactive surface and the inner surface models. The inner surface modified films presented higher wettability than the surface modified films. Wide-angle x-ray diffraction results showed that the d-spacing values of the inner surface model increased compared with those of the surface model, but there was no significant difference between the amide- and collagen-modified PHBV films. The peak melting temperatures of PHBV and the special endotherm around 70 °C were following the order: PHBV > amide-modified PHBV > collagen-modified PHBV. The weight loss of the collagen-modified PHBV (inner surface model) might involve hydrolyzation and mineralization during 360 days of incubation, with a maximum value of 18.24%, while PHBV films did not show significant weight loss. The pH value of the degradation fluids fluctuated in the range of 6.86–7.22, as the initial pH was recorded at 7.20. Based on the surface model, collagen-modified PHBV scaffolds were prepared, which enhanced chondrocyte adhesion and spread on the biomimetic surface. Two surface modification models might develop a protocol with a view to generating a biocompatible and biomechanical scaffold for use in meniscus regeneration.

Polyacrylamide grafted on multi‐walled carbon nanotubes for open‐tubular capillary electrochromatography: Comparison with silica hydride and polyacrylate phase matrices

A new nanoparticle-bound polymer stationary phase was prepared by in situ polymerization of methacrylamide (MAA), bis-acrylamide crosslinker, and carboxylated multi-walled carbon nanotubes (multi-walled CNTs; MWNTs), using the abundant double bonds in the cyclopentadienyl rings in MWNT structure, on a silanized capillary. Each intermediate capillary between the synthesis steps was characterized by SEM, by ATR-IR, and by EOF measurements varying the pH, concentration, and volumetric ratios of ACN in running buffers. The resulting EOF profile was comparable to those of two other capillaries with different phase matrices, silica hydride and polybutyl methacrylate (BMA) phases. With the complex functionality of MWNTs on the hydrophilic polyacrylamide network, the MAA-CNT capillary was capable of separating diverse samples with a wide range of polarity and dissociation properties using open-tubular CEC. Besides optimizing CEC conditions, the migration times of samples were analyzed with respect to velocity and retention factors to evaluate electrophoretic and chromatographic contributions to the CEC mechanism. The migration rates of benzoic acids were determined by the electrophoretic mobilities of the various phenolate ions, while phenolic aldehydes and ketones were additionally influenced by chromatographic interactions, such as π-π, electrostatic effects, hydrogen bonding, and hydrophobic interactions. The retention factors were greater for flavonoids, which are polyphenolic, than for simple phenols, but were smaller than those obtained from the hydrophobic BMA-CNT column. A complete well-resolved separation of the cationic forms of tetracyclines was acheived either by electrophoresis or by chromatography in the MAA-CNT capillary, but not in the BMA-CNT and silica hydride-CNT capillaries.

Our strategy in complication management of augmentation mammaplasty with polyacrylamide hydrogel injection in 235 patients

Polyacrylamide hydrogel (PAAG) was once widely used in breast augmentation in China. Although it had been banned for augmentation mammaplasty in 2006, a large number of patients whose breasts were augmented with the gel injection have continued to seek medical advice because of its complications. The clinical management of these complications has never been standardised. The data of a total of 235 patients with complications following PAAG-injected breast augmentation have been summarised and the types and causations analysed. Magnetic resonance imaging (MRI) was undertaken in 228 patients with palpable masses, breast pain or tenderness, asymmetry or deformity and functional or psychological problems to eliminate neoplasm, infection and to delineate the diseases. The surgical gel evacuation via periareolar incisions was performed for all patients and immediate silicone breast prostheses were implanted in 108 patients and were delayed in 28 cases by 6 months. Most patients (214/235) of the group were satisfied with the treatment, and symptoms disappeared after removal of the gel. The gel distribution and involved tissue were well defined and neoplasm was ruled out by MRI. Postoperative MRI in 68 patients revealed that no obvious PAAG remaining. In either immediate or delayed reconstructive patients with silicone breast implants, good breast contour presented. A diagnosis and management strategy for these complications is proposed. In conclusion, the breast masses, pain and deformity are major complications after PAAG-injected breast augmentation. Psychological problems should be paid attention to. MRI is a sensitive and accurate method for diagnosis and treatment evaluation. Surgical removal of injected gel is the preferred method for complication management. The implantation of silicone prostheses for breast contour restoration after PAAG evacuation is effective for patients under strict selection. Our strategy for treating PAAG-related complications proved useful.

Unacceptable Results with an Accepted Soft Tissue Filler: Polyacrylamide Hydrogel

All injectable volumizing agents and fillers may be associated with immediate or delayed complications (overall rate, \1%) [1]. The complication rate is directly related to the technique of injection as well as to the properties of the injected material. With increased persistence of the material, the possibilities of serious complications become more dependent on the inherent physiochemical characteristics of the material rather then on those of the injection technique. Polyacrylamide is used for protein separation in molecular biology [2]. The clinical use of polyacrylamide gel (PAG) as an injectable filler started as Interfall in the Ukraine in 1983. In small quantities, the gel is well tolerated and slowly absorbed by the body (t1/2, 20 years). Different preparations of polyacrylamide hydrogels have unique characteristics, although they all are a combination of a hydrophilic polyacrylamide and nonpyrogenic water. The PAGs discussed in the article by Manafi and colleagues have very different characteristics in terms of the gel concentration. Interfall (Interfall Ltd., Kiev, UA) is a hydrogel with a variable gel concentration of 3.5% to 9%. The latest PAG that has undergone PMA submission to the Food and Drug Administration (FDA) is Aquamid hydrogel [3], a consistent 2.5% cross-linked polyacrylamide gel manufactured by Contura (Denmark). Aquamid (Contura International, Switzerland) is a gel with a constant PAG concentration of 5%. When the safety profile and efficacy of an injectable material is evaluated, all of its unique characteristics must be discussed so an appropriate conclusion can be drawn. In the article by Manafi and colleagues, the patient basis was biased in the conclusion drawn. Only patients experiencing unsatisfactory results and complications of polyacrylamide hydrogel injections were included in their study. Three different preparations of PAG materials were included, yet the effect of the gel concentration on the complication rate was not discussed. An in-depth discussion on the relationship of the volume injected (200 ml/ breast for case 2 vs. 5 ml/lips for case 1) would have been welcome because our experience and clinical data in relation to permanent and semipermanent fillers supported it [1]. Although this article is of clinical interest, the conclusion drawn is not based on the data presented. Recent data [3, 4] from multicenter double-blind studies of 315 and 101 patients, respectively, have shown injections of polyacrylamide hydrogel for soft tissue augmentation at 12 and 24 months to be safe, efficacious, and without adverse soft tissue reactions. In the United States, PMA has submitted Aquamid hydrogel to the FDA.

Diagnostic cytological features of polyacrylamide gel injection augmentation mammoplasty

To study the cytological features of breast lesions associated with hydrophilic polyacrylamide gel (PAAG) injection augmentation mammoplasty and to determine the specific diagnostic features. Fine needle aspiration (FNA) cytology smears from 14 patients who presented with breast lump and a clinical history of PAAG injection were reviewed. The staining properties of the PAAG material in Papanicolaou (Pap), Haematoxylin and Eosin (H&E) and Diff-Quik stains, as well as the cellular background, were studied. Cell blocks were also studied with H&E, periodic acid-Schiff (PAS), periodic acid-Schiff with diastase digestion (PASD) and mucicarmine (MC) stains. PAAG was stained consistently pinkish with a homogenous smooth texture on H&E (100%), polychromasia on Pap (100%) and magenta violet with bubbly vacuoles on Diff-Quik (100%). Half (7) of the cases showed sharp borders. The presence of foreign body type giant cells with histiocytes (5 cases, 36%) and scanty clusters of benign ductal cells (4 cases, 29%) were seen in the background of a minority of the cases. PAAG was represented by blocks of homogenous grey-purplish acellular material with a sharp border on cell block sections, which were negative for PAS, PASD and MC. PAAG shows a consistent staining pattern in various common cytological staining preparations. Blocks of acellular gelatinous material, stained homogenous pinkish on H&E, polychromasia on Pap and magenta violet with bubbly vacuoles on Diff-Quik, are the reliable cytological features of PAAG.

Rigid Crosslinked Polyacrylamide Monoliths with Well‐Defined Macropores Synthesized by Living Polymerization

Rigid crosslinked polyacrylamide monoliths with well-defined macropores have been successfully fabricated by organotellurium-mediated living radical polymerization (TERP) accompanied by spinodal decomposition. The TERP forms homogeneous networks derived from N,N-methylenebis(acrylamide) (BIS), in which spinodal decomposition is induced to form macropores. Macropore diameter can be controlled from submicrons to a few microns, and also the obtained networks contain mesopores in the macroporous skeletons, which are collapsed by evaporative drying. They are promising materials with hydrophilic polyacrylamide surfaces and have enough strength to preserve the macropores from the surface tension arising in the repetitive swelling and drying that may occur in many applications.

The use of electron beam lithographic graft-polymerization on thermoresponsive polymers for regulating the directionality of cell attachment and detachment

A simple process for nano-patterned cell culture substrates by direct graft-polymerization has been developed using an electron beam (EB) lithography system requiring no photo-masks or EB-sensitive resists. The compound N-isopropylacrylamide (IPAAm) was locally polymerized and grafted directly by EB lithographic exposure onto hydrophilic polyacrylamide (PAAm)-grafted glass surfaces. The size of the surface grafted polymers was controlled by varying the area of EB dose, and a minimal stripe pattern with a 200 nm line-width could be fabricated onto the surface. On the stripe-patterned surfaces, above the lower critical solution temperature (LCST), the cells initially adhered and spread with an orientation along the pattern direction. The magnitude of the spreading angle and elongation of adhered cells depended on the pattern intervals of the grafted PIPAAm. When culture temperature was lower than the LCST, cultured cells detached from the surfaces with strong shrinkage along the pattern direction, and sometimes folded and became parallel with the stripe pattern. This patterned cell recovery technique may be useful for the construction of muscle cell sheets with efficient shrinkage/relaxation in a specific direction and spheroidal 3D cell structures, with application to tissue engineering and microfluidic cellular devices.