Permeability and Separation Characteristics of Polypeptide-Functionalized Polycarbonate Track-Etched Membranes (original) (raw)
Related papers
Substrate-specific functional membranes based on etched ion tracks
Radiation Measurements, 1997
A novel thin membrane synthesized by copolymerizing diethyleneglycol-bis-allylcarbonate (CR-39) with a minor amount of acryloyl-L-proline methyl ester (A-ProOMe) was etched by an aqueous NaOH solution after a 6.19 MeV/n S4Kr ion irradiation to produce ion-track membranes. The ion-track membranes were chemically modified by radiation-induced grafting of A-ProOMe. We found that a polymer gel of A-ProOMe shows a characteristic volume phase transition around a lower critical solution temperature (LCST) of 14°C, namely thermo-responsive function. The changes in size of pores in the grafted membrane under different temperatures in water were measured by both the scanning electron microscopy (SEM) and the atomic force microscopy (AFM). The pore was controlled from an open state above LCST to a completely closed state below LCST. The permeability of pnitrophenol through the grafted membrane was also measured by changing the temperature of the cell.
Functionalization and Application of Ion Track-Etched Nanochannels in Polymer Membranes
2009
Nanochannels fabricated in ion-tracked polymer membranes have a great range of applications in biotechnology, where they are suitable for sensing biomolecules, and act as stimuli-responsive devices and molecular filters of high selectivity. For all these applications, it is highly desirable to control the channel-surface properties, i.e. to functionalize the surface in order to match specific requirements concerning hydrophobicity, selectivity, and interaction with molecules passing through the channel. In ion-tracked polymer membranes, single conical nanochannels were fabricated by selective chemical etching of the damage trails caused by the ions along their trajectories, resulting in the generation of carboxylate groups on the channel surface. These groups were functionalized with molecules having variable polarity and chemical groups that act as binding sites for different analytes. As is well-known, the negatively or positively charged conical nanochannels selectively transport cations or anions, respectively. This rectifies ionic current flowing through the channel. The success of functionalization procedure was examined and proven by measuring the asymmetric current-voltage (I-V) curves and permselectivity of the channel. The functionalized single conical nanochannels were successfully used for the electrochemical interaction of bovine serum albumin. The work presented here also includes the fabrication and characterization, both experimentally and theoretically of a single amphoteric nanochannel, functionalized with lysine and histidine chains, whose positive and negative charges are very sensitive to external pH. This nanofluidic diode with amphoteric chains attached to the channel surface allows for a broad set of rectification properties supported by a single nanodevice. A new facile approach was also introduced to incorporate biosensing elements into nanochannels by using electrostatic self-assembly of bifunctional macromolecular ligands which were used for the biospecific recognition of protein analytes. This approach also enables the creation of supramolecular multilayered structures inside the nanochannels that are stabilized by strong ligand-receptor interactions. The integration of "smart" polymer brushes, constituted of zwitterionic monomers in polyimide conical nanochannels, to obtain a new highly functional signal-responsive chemical nanodevice, has been reported for the first time. This strategy enables a higher degree of control over rectification properties, when compared with charged monolayer assemblies. Moreover, nanochannels were also functionalized with poly-N-isopropylacrylamide and poly(4-vinyl pyridine) brushes to display temperature and pH controlled gating properties, respectively.
Langmuir, 2002
Control of external pH and ionic strength is used to separate proteins with surface-modified, nanoporous polycarbonate track etched (PCTE) membranes. The porous PCTE membranes were modified with monolayers of self-assembled thiols (HSC10H20COOH) on electroless gold. The hydraulic radius of the pores in the surface-modified membranes was 8.7 nm. Two proteins of nearly identical molecular weight, bovine serum albumin (BSA) and bovine hemoglobin (BHb), were used as the permeants. The fluxes of BSA and BHb through the membranes show maximum values at the isoelectric points (pI) of the proteins. At pH values above and below the pI, charge interactions between the proteins, their counterions, and the pore surface leads to a decrease in flux. The imposition of a difference in ionic strength across the membrane causes osmotic flow and leads to a significant increase in the protein fluxes and an enhancement of the selectivity of BSA over BHb. In protein separation experiments, the BSA and BHb fluxes are nearly 3 times larger than those observed with no ionic strength difference.
Langmuir, 2002
The functionalization of materials with polyamino acids provides opportunities where electrostatic and conformational properties can be utilized for selective separations and controlled transport applications. The influence of covalently attached poly(L-glutamic acid) (PLGA) on the performance characteristics of a microporous cellulosic support has been investigated to determine its effect on the transport of water and charged solutes. The presence of these charged multifunctional groups promotes electrostatic interactions with ionic species far removed from the pore surface. This allows for nonsteric ion exclusion involving membrane materials that offer less resistance to solvent (water) transport. In addition, the helix-coil transitions of this polypeptide and "core leakage" effects have been shown to affect both the permeability and solute retention in a reversible fashion upon variations in the solution pH. Following PLGA attachment, the permeability could be adjusted from 50 to 90% of the value of the base support matrix (∼3-6 × 10-4 cm 3 /cm 2 s bar). Experiments were performed on single and mixed electrolyte systems using model inorganic and organic solutes. Solute rejection values as high as 73% were reported for dilute Na2SO4 solutions using membranes with pore sizes ranging from 0.05 to 0.21 µm.
Advances in Biomimetics, 2011
at al., 2000). In particular, ATP takes part in active membrane potential formation, Hep in the anticoagulation process (Desai, 2004) and Asn and Gln in the voltage-ligand gated influx on calcium ions via the NMDA channels (McBain & Mayer, 1994). The following methodology is accepted for applying CPs as biomimetic membranes. In order to obtain the membranes (CP-BL-Y, where Y = K + , Na + , Li + , Ca 2+ , Mg 2+), first ATP, ADP, Hep, Asn or Gln are introduced into the CP matrix during electropolymerization. Next, the calcium, magnesium, lithium, sodium or potassium potentiometric sensitivity is induced by soaking in an alkaline solution of one of these ions until close-to-Nernstian sensitivity for the films is obtained. The films are then used to monitor the equilibration processes induced by the change in bulk concentration of magnesium/calcium or lithium/potassium/sodium ions or stimulation with external electrical signal (Paczosa-Bator at al., 2009). The resulting transitory potential response is recorded and characteristic potential transients observed are theoretically interpreted. 2. Conducting polymers used and their properties It is well known that conducting polymers (CPs) such as poly(pyrrole) (PPy), poly(Nmethylpyrrole) (PMPy) or poly(3,4-ethylenedioxythiophene) (PEDOT) in the oxidation process during electrodeposition are easily doped with small inorganic anions and in consequence exhibit anionic open-circuit sensitivity. Cationic sensitivity can be observed if the CP films are doped with cations during reduction. This happens when the CP film is doped with bulky immobile anions, for instance naphthalenesulphonate, indigo carmine or methylene blue (Gao at al., 1994; Bobacka et al., 1994). The ionic sensitivity induced in this way is dependent on the redox status of the polymer film and is rather nonselective (Lewenstam at al., 1994). As we shown, the cationic sensitivity may be enhanced and stabilized with use of bulky, metal-complexing ligands from the group of metallochromic indicators as dopants. This happens because the bulky dopants retain in the polymer film their complexing properties known from water chemistry and the selective cationic sensitivity results from the complex formation inside CP films (Migdalski et al., 1996). This provides the unique possibility of forming CP films doped with bulky and biologically active anions such as adenosinotriphosphate (ATP), adenosinodiphosphate (ADP), heparin (Hep) or amino acids-asparagine (Asn) and glutamine (Gln). These films may be used as biomimetic membranes to inspect processes important for membrane potential formation or membrane transport (Paczosa-Bator at al., 2007). Our observations have shown that the conducting polymer designed for biomimetic membranes should have smooth surface morphology (a. Paczosa-Bator at al., 2006). It is well known that the morphology of conducting polymer films depends on many experimental parameters, such as substrate used, electrodeposition method, kind of monomer and doping anions, kind of solvent, pH and post deposition treatment of the film. Depending on the further application of conducting polymer layers, different surface morphology (rough or smooth) and different structure are required (
Structure and Properties of Poly(4-methylpentene-1) Track-Etched Membranes
—The influence of irradiation and the subsequent etching of latent tracks in poly(4-methylpen-tene-1) (PMP) films on the transport parameters of the resulting membranes has been studied. The films have been irradiated with accelerated Kr and Xe ions of 4.5 and 1.2 MeV/nucleon in energy at a fluence of 10 6 –10 9 cm −2. It has been found that the irradiation followed by etching makes it possible to obtain an anisotropic membrane with a nonporous selective layer between two porous layers with tapered pores. The CH 4 , CO 2 , and He transport characteristics of the membranes have been examined. It has been shown that these modification methods can significantly increase the gas flux through the membrane. It is believed that the ion track etching procedure as applied to PMP can form the basis for fabricating membranes with a highly permeable, nonporous, gas-selective layer.
Selective ion-permeable membranes by insertion of biopores into polymersomes
In nature there are various specific reactions for which highly selective detection or support is required to preserve their bio-specificity or/and functionality. In this respect, mimics of cell membranes and bio-compartments are essential for developing tailored applications in therapeutic diagnostics. Being inspired by nature, we present here biomimetic nanocompartments with ion-selective membrane permeability engineered by insertion of ionomycin into polymersomes with sizes less than 250 nm. As a marker to assess the proper insertion and functionality of ionomycin inside the synthetic membrane, we used a Ca2+-sensitive dye encapsulated inside the polymersome cavity prior to inserting the biopore. The calcium sensitive dye, ionomycin, and Ca2+ did not influence the architecture and the size of polymersomes. Successful ionomycin functionality inside the synthetic membrane with a thickness of 10.7 nm was established by a combination of fluorescence spectroscopy and stopped-flow spectroscopy. Polymersomes equipped with ion selective membranes are ideal candidates for the development of medical applications, such as cellular ion nanosensors or nanoreactors in which ion exchange is required to support in situ reactions.
2019
In this study we have prepared cylindrical and conical nanopores on poly(ethylene terephthalate) (PET) membranes using track-etching method. Later on we have investigated the mass transport of the chosen model dye Methyl Orange (MO) through these membranes. In order to enhance the transport flux of the dye, we have used surface functionalization using ethylene diamine (EDA) as the functionalization agent. We have confirmed the functionalization of the nanopore surface using electrochemical measurements. We have investigated mass transport through functionalized and bare PET membranes and shown that by attaching amine groups on the nanopore walls, we can indeed increase the transport of MO. Effects of pore size, pore geometry and temperature were investigated for the transport of MO. We have shown that PET, which has a negative surface charge at neutral pH, can be functionalized for a more effective transport of negatively charged analyte.
Radiation Measurements, 2008
The effect of surfactants on chemical development of ion tracks in polymers has been studied. It has been shown that surface-active agents added to an alkaline etching solution adsorb on the polymer surface at the pore entrances. This reduces the etch rate, which leads to the formation of pores tapered toward the surface. Self-assembly of surfactant molecules at the pore entrance creates a barrier for their penetration into the etched-out nanopores, whereas hydroxide ions diffuse freely. Due to this, the internal pore volume grows faster than the pore surface diameter. The ability to control pore shape is demonstrated with the fabrication of profiled nano-and micropores in polyethylene terephthalate, polycarbonate. Some earlier published data on small track-etched pores in polycarbonate (in particular, the pore diameter vs. etching time curves measured conductometrically) have been revised in light of the above findings. Adding surfactants to chemical etchants makes it possible to optimize the structure of track membranes, thus improving their retention and permeation properties. Asymmetric membranes with thin skin retention layers have been produced and their performance studied.
Conducting polyamic acid membranes for sensing and site-directed immobilization of proteins
Analytical Biochemistry, 2012
A biosensor platform based on polyamic acid (PAA) is reported for oriented immobilization of biomolecules. PAA, a functionalized conducting polymer substrate that provides electrochemical detection and control of biospecific binding, was used to covalently attach biomolecules, resulting in a significant improvement in the detection sensitivity. The biosensor sensing elements comprise a layer of PAA antibody (or antigen) composite self-assembled onto gold (Au) electrode via N-hydroxysuccinimide (NHS) and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) linking. The modified PAA was characterized by Fourier transform infrared (FTIR), 1 H nuclear magnetic resonance (NMR), and electrochemical techniques. Cyclic voltammetry and impedance spectroscopy experiments conducted on electrodeposited PAA on Au electrode using ferricyanide produced a measurable decrease in the diffusion coefficient compared with the bare electrode, indicating some retardation of electron transfer within the bulk material of the PAA. Thereafter, the modified PAA surface was used to immobilize antibodies and then to detect inducible nitric oxide synthase and mouse immunoglobulin G (IgG) using enzyme-linked immunosorbent assay (ELISA), surface plasmon resonance (SPR), and amperometric techniques. ELISA results indicated a significant amplified signal by the modified PAA, whereas the SPR and amperometric biosensors produced significant responses as the concentration of the antigen was increased. Detection limits of 3.1 Â 10 À3 ng/ml and 2.7 Â 10 À1 ng/ml were obtained for SPR and amperometric biosensors, respectively.