Pluronic Polymer Research Articles

Effect of temperature gradients on single-strand conformation polymorphism analysis in a capillary electrophoresis system using Pluronic polymer matrix

Capillary electrophoresis-single strand conformation polymorphism (CE-SSCP) analysis is a prominent bioseparation method based on the mobility diversity caused by sequence-induced conformational differences of single-stranded DNA. The use of Pluronic polymer matrix has opened up new opportunities for CE-SSCP, because it improved the resolution for various genetic analyses. However, there still exists a challenge in optimizing Pluronic-based CE-SSCP, because the physical properties of Pluronic solutions are sensitive to temperature, particularly near the gelation temperature, where the viscoelasticity of Pluronic F108 solutions sharply changes from that of a Newtonian fluid to a hydrogel upon heating. We have focused on a set of experiments to control the ambient temperature of the CE system with the aim of enhancing the reliability of the CE-SSCP analysis by using the Applied Biosystems ABI 3130xl genetic analyzer with Pluronic F108 solution matrix. The ambient temperature control allowed us to vary the inlet and outlet portion of the capillary column, while the temperature of the column was kept at 35°C. The resolution to separate 2 single-base-pair-differing DNA fragments was significantly enhanced by changing the temperature from 19 to 30°C. The viscoelastic properties of the F108 solution matrix upon heating were also investigated by ex situ rheological experiments with an effort to reveal how the development of gels in Pluronic solutions affects the resolution of CE-SSCP. We found that the column inlet and outlet temperatures of the capillary column have to be controlled to optimize the resolution in CE-SSCP by using the Pluronic matrix.

Development, in vitro and in vivo Evaluation of Novel Injectable Smart Gels of Azithromycin for Chronic Periodontitis

Periodontitis is an inflammatory condition affecting teeth resulting in progressive destruction of periodontal ligaments, resorption of alveolar bone and loss of teeth. Treatment of periodontitis includes surgical and non surgical management. Systemic antibiotics are also used for the treatment of periodontitis. The aim of this research was to formulate smart gel system of azithromycin (AZT) and to evaluate in vitro and in vivo for non-surgical treatment of chronic periodontitis. Azithromycin dihydrate, used systemically in the treatment of periodontitis, was formulated into smart gels using biodegradable, thermosensitive polymer Pluronic® F-127 (PF-127) and Hydroxy Ethyl Cellulose (HEC) as copolymer. The prepared smart gels were evaluated for sterility, content uniformity, gelation temperature and time, syringeability, rheological behavior, in vitro diffusion and in vivo efficacy in human patients. The prepared smart gels were clear and transparent, sterile, thermoresponsive and injectable. Viscosity of gels increased with increase in concentration of polymer/co-polymer and also with temperature. They gelled in short response time below the body temperature. In vitro release studies showed controlled drug release which was influenced significantly by the properties and concentration of PF-127 and HEC. In vivo efficacy studies showed a significant improvement (p <0.001) in clinical parameters such as gingival index, probing pocket depth, clinical attachment level, bleeding index and plaque index. The developed azithromycin smart gel system is a novel approach for the treatment of chronic periodontitis since it reduces the dose and side effects, bypasses the usual surgical procedures and improves patient compliance.

Supramolecular Hydrogels from In Situ Host–Guest Inclusion between Chemically Modified Cellulose Nanocrystals and Cyclodextrin

When grafted β-cyclodextrin is used as targeting sites, Pluronic polymers have been introduced on the surface of cellulose nanocrystals by means of inclusion interaction between β-cyclodextrin and hydrophobic segment of the polymer. Because of the steric stabilization effect, surface poly(ethylene glycol) chains facilitate the dispersion and compatibility of nanocrystals, which also enhance the loading levels of nanocrystals in the hydrogel system. Meanwhile, uncovered poly(ethylene glycol) segments render the participating inclusion of α-cyclodextrin for the architecture of in situ hydrogels. Surface grafting and inclusion reactions were proved by solid (13)C NMR and FTIR. Grafting efficiency of β-cyclodextrin and inclusion efficiency of Pluronic on the surface of nanocrystals were confirmed by UV spectroscopy and elemental analysis. A significant enhancement of the structural and thermal stability of in situ hydrogels with high loading levels of modified nanocrystals (>5.77 wt %) was observed by rheological analysis. Further study reveals the performance and behavior of hydrogels under a different pH environment. Finally, in situ hydrogels were used as drug carrier for in vitro release of doxorubicin and exhibit the behavior of prolonged drug release with special release kinetics.

Control over hygroscopic growth of saline aqueous aerosol using Pluronic polymer additives

The hygroscopic properties of an aerosol originating from a nebulizer solution can affect the extent of peripheral deposition within the respiratory tract, which in turn affects drug efficacy of drugs delivered to the lungs. Thus, the ability to tailor the degree and rate of hygroscopic growth of an aerosol produced by a nebulizer through modification of the formulation would serve to improve drug efficacy through targeted lung deposition. In this study, the kinetic and thermodynamic hygroscopic properties of sodium chloride aerosol mixed with commercially available Pluronic polymers, specifically F77 and F127, are reported using three complementary single aerosol analysis techniques, specifically aerosol optical tweezers, a double ring electrodynamic balance and a concentric cylinder electrodynamic balance. The F77 polymer is shown to have a predictable effect on the hygroscopic properties of the aerosol: the ability of the droplet to uptake water from the air depends on the solute weight percent of sodium chloride present in a linear dose dependant manner. Unlike the smaller F77, a non-linear relationship was observed for the larger molecular weight F127 polymer, with significant suppression of hygroscopic growth (>50% by mass) for solution aerosol containing even only 1 wt% of the polymer and 99 wt% sodium chloride. The suppression of growth is shown to be consistent with the formation of mixed phase aerosol particles containing hydrophilic inorganic rich domains and hydrophobic polymer rich domains that sequester some of the inorganic component, with the two phases responding to changes in relative humidity independently. This independence of coupling with the gas phase is apparent in both the equilibrium state and the kinetics of water evaporation/condensation. By starting with a saline nebulizer solution with a concentration of F127 ∼10(-2)mM, a 12% reduction in the radius of all aerosol produced at a relative humidity (RH) of 84% is possible. The difference in diameter is RH dependent, and may be much greater at higher humidities. These findings suggest that the addition of μM concentrations of larger Pluronic polymers to nebulizer formulations may greatly reduce the size of aerosols produced.

Micellar ordered structure effects on high‐resolution CE‐SSCP using Pluronic triblock copolymer blends

Pluronic F108 block copolymers have shown a great promise to achieve the desirable high resolution in the conformation-sensitive separation of ssDNA using CE-SSCP. However, fundamental understanding of the structures and properties of Pluronic matrix affecting the resolution is still limited. Unlike conventional gel-forming homopolymers, Pluronic F108 block copolymers are amphiphilic macromolecules consisting of poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) triblock copolymers, which are capable of forming a highly ordered micellar structure in aqueous solution. In this study, we have performed a series of experiments by blending different types of Pluronic polymers to control the formation of micelles and to study the correlation between separation and rheological characteristics of Pluronic gels affecting the resolution of CE-SSCP. Our experiments have been specifically designed to elucidate how the micellar structure affects the resolution of CE-SSCP upon altering the size uniformity and constituent homogeneity of the micelles. Our results suggest that uniformly sized micelle packing is the primary structural feature of Pluronic gel matrix for the high-resolution separation, while the size and constituent of the micelle themselves need to be considered as secondary factors.

Pluronic polymer capped biocompatible mesoporous silica nanocarriers

A facile self-assembly method is described to prepare PEGylated silica nanocarriers using hydrophobic mesoporous silica nanoparticles and a pluronic F127 polymer. Pluronic capped nanocarriers revealed excellent dispersibility in biological media with cyto- and blood compatibilities.

A Facile Template Approach for Preparing Microstructures of Bimodal Crystalline Mesoporous Titania Powders

This paper presents the preparation of bimodal crystalline macro-/mesoporous titania powders by using a pluronic polymer (EO20PO70EO20, P123) as a template through a hydrothermal treatment. The as-prepared powders were characterized by X-ray diffraction (XRD), nitrogen adsorption-desorption, scanning electron microscope (SEM) and transmission electron microscope (TEM). The results reveal that the amount of P123 has a significant effect on the surface area of the mesoporous titania. When the mass ratio of P123:TBOT is 1:14, the crystalline macro-/mesoporous titania has the largest surface area (120.96 m2/g), the average pore diameter of this sample reaches a minimum of 6.67 nm.

Titanium dioxide separation from water by PEG and Pluronic type polymers

Separation property of aqueous solutions of PEG (Mv=10,000) and poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO–PPO–PEO) triblock copolymers (F-68 and F-127), both in the absence and presence of salts, in a titanium dioxide suspension was evaluated. The separation process was performed by turbidity and zeta potential measurements and investigated with respect to some parameters such as the settling time, the polymer dose, the salt nature and concentration (sodium chloride (NaCl) and potassium chloride (KCl)) as well as polymer structure (ethylene oxide (EO) content). According to the turbidimetric results, a significant change in separation performance was noticed when salt solutions of PEG were used; the residual turbidity decreased with increasing salt concentration. F68 and F127 samples showed a much lower decrease of the residual turbidity over the entire range of polymer dose investigated, both in water and water containing salts. A zeta potential value close to zero at optimum polymer dose points to contribution from neutralization mechanism for destabilization of titanium dioxide suspension by PEG in 0.01M KCl. The viscosity behavior of the polymers under study was also investigated. In order to obtain the intrinsic viscosities, the experimental data were plotted in terms of the Wolf method. The results show that the experimental data fit well with the Wolf model.

Direct synthesis, characterization and catalytic performance of Al-SBA-15 mesoporous catalysts with varying Si/Al molar ratios

Through a directly hydrothermal process and utilizing Pluronic P123 triblock polymer (EO20PO70EO20, Mav = 5800) as a template, Al-SBA-15 mesoporous materials have been prepared with different Si/Al molar ratios. The materials were characterized by XRD, ICP-OES, SEM, TEM, Py FT-IR, N2 adsorption–desorption and NH3-TPD techniques. Meanwhile, the catalytic performance of the Al-SBA-15 materials was investigated through Friedel–Crafts alkylation of 2,4-ditert-butyl-phenol with cinnamyl alcohol. Characterization results showed that the catalysts contain a variety of acid sites whose contents vary in a systematic manner with various Si/Al molar ratios of the materials, and have a higher catalytic activity in the alkylation reaction of phenol with tert-butanol. It was found that the Al-SBA-15 samples with good mesoporous structure are highly reusable preserving most of their catalytic activity after five cycles.

Small-Angle Neutron Scattering from Aqueous Dispersions of Single-Walled Carbon Nanotubes with Pluronic F127 and Poly(vinylpyrrolidone)

Amphiphilic block copolymers are excellent dispersants for single-walled carbon nanotubes (SWCNT) in aqueous environments, where their noncovalent attachments do not affect the π chemical bonding. In this small-angle neutron scattering (SANS) study, we investigate whether the coverage of Pluronic F127 polymers around the CNTs depends on the solution concentration in the range of 1-6% (w/w). The observations indicate that at these concentrations the SWCNT surface is fully saturated at about 14 chains per unit length of 100 Å. Furthermore, we seek to verify whether the unusual effect observed in a previous study by contrast variation, interpreted as being due to a dense hydration layer around the polymer chains, also appears using a homopolymer (polyvinylpyrrolidone - PVP) that does not contain poly(ethylene oxide) (PEO) units. The SANS patterns showed again a minimal intensity value at much higher solvent composition (75% D(2)O) than the expected value of 29% D(2)O. The minimum scattering curve exhibited a nearly q(-1) power law at small angles, an indication of rodlike entities. A model of a CNT thin bundle with loosely adsorbed polymer chains around it (core-chains) was reasonably well fitted to the data. The polymer chains are assumed to be surrounded by a water layer with a slightly higher density than bulk water, having partial selectivity for D(2)O.

Abstract 2893: Curcumin loaded magnetic nanoparticles for breast cancer therapeutics and imaging applications

Abstract Background: Magnetic nanoparticles (MNPs) with theranostic features (diagnosis and treatment) have attracted significant attention and will greatly improve the scope of nanomedicine in cancer applications. The aim of this study is to develop a novel MNPs formulation composed of an iron oxide core coated with α-cyclodextrin and pluronic polymer (F68), to load an anti-cancer drug (curcumin, CUR) and prevent particle aggregation, respectively. The therapeutic efficacy and imaging capabilities of this novel formulation were evaluated in breast cancer cell line models. Methods: The physico-chemical analyses of curcumin loaded MNPs (MNP-CUR) were performed using dynamic light scattering (DLS), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) analyses. MNP-CUR internalization was evaluated after 6 hrs incubation with MDA-MB-231 cancer cells by Prussian blue stain and TEM. Anti-cancer effects of the MNP-CUR formulation was determined by a tetrazolium based dye (MTT) and colony formation assays using “triple negative” MDA-MB-231 cancer cells. Tetramethylrhodamine, ethyl ester, perchlorate (TMRE), red mitochondrial superoxide indicator (Mitosox), and propidium iodide stains were used to evaluate the loss of mitochondrial membrane potential, reactive oxygen species (ROS) generation, and apoptosis/dead cells, respectively, to determine effects MNP-CUR on these cellular features. The imaging capability of this MNP-CUR formulation was analyzed using a magnetic resonance imaging (MRI) system. The magnetic targeting feature of the MNP-CUR formulation was evaluated using fluorescence microscopy. Results: We prepared MNP-CUR with an average aggregative particles size of ∼ 150 nm (individual particle grain size, ∼ 9-11 nm). Prussian blue stain data represent a preferential uptake of MNP-CUR in MDA-MB-231 cells in a dose dependant manner. TEM analysis demonstrates that accumulation of MNP-CUR nanoparticles in cancer cells indicate that particles are not attached on the surface of cells but internalized within the cells. The MNP-CUR formulation showed strong anti-cancer effects in breast cancer cells including “triple negative” MDA-MB-231 cancer cells compared to free curcumin. This formulation also enhanced loss of mitochondrial membrane potential, generation of ROS and apoptosis compared to free curcumin treatment. Additionally, the MNP-CUR formulation exhibits superior T2 imaging characteristics compared to T1. A significant increase of the targeting feature was observed with MNP-CUR in breast cancer cells. Conclusion: These data suggest that our novel MNP-CUR formulation exhibits potent anti-cancer activity along with imaging and magnetic targeting capabilities. This approach can be extended to pre-clinical and clinical use and may have importance in cancer treatment and cancer imaging in the future. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2893. doi:1538-7445.AM2012-2893

Poly(caprolactone)-modified Pluronic P105 micelles for reversal of paclitaxcel-resistance in SKOV-3 tumors

Three poly(caprolactone)-modified Pluronic P105 polymers (P105/PCLs) were synthesized using commercially available ε-caprolactone monomers and Pluronic P105 copolymers. The chemical structures, compositions and molecular weights of the P105/PCLs were confirmed by FT-IR, 1H NMR and GPC measurements. Three paclitaxel (PTX)-loaded P105/PCL polymeric micelles were then prepared, and they showed average diameters in the range of 30–150 nm, drug-loading coefficients of 0.15%–5.43%, and encapsulation ratios of 2.1%–76.53%. The in vitro cytotoxicity assay demonstrated that three PTX-loaded P105/PCL micelles were able to sensitize the resistant SKOV-3/PTX tumor cells. The PTX-loaded P105/PCL50 micelle was then selected for an in vivo antitumor efficacy study. The tumor volumes in nude mice bearing s.c. resistant SKOV-3/PTX carcinoma treated with this micellar PTX were significantly less than the control group treated with Taxol. It was demonstrated that three PCL-modified P105 monomers and micelles inhibited P-gP efflux activity in the resistant SKOV-3/PTX cells via at least three intracellular events: 1) inhibition of ATPase of P-gP, 2) decrease of membrane microviscosity and 3) a loss of mitochondrial membrane potential and subsequent decrease of ATP levels at the concentration of monomers (0.001%) and/or micelles (0.01–1.0%). Considering other favorable characteristics, such as sustained PTX release in vitro, long-circulating time in vivo and increased PTX concentration in the tissues of ovaries and uterus in mice, the PCL-modified Pluronic P105 polymeric micelle system could have important clinical implications for delivery of paclitaxel and treatment of the resistant ovarian tumors.

Alkali metal salts doped pluronic block polymers as electron injection/transport layers for high performance polymer light-emitting diodes

A series of alkali metal salts doped pluronic block copolymer F127 were used as electron injection/transport layers (ETLs) for polymer light-emitting diodes with poly[2-(4-(3′,7′-dimethyloctyloxy)-phenyl)-p-phenylenevinylene] (P-PPV) as the emission layer. It was found that the electron transport capability of F127 can be effectively enhanced by doping with alkali metal salts. By using Li2CO3 (15%) doped F127 as ETL, the resulting device exhibited improved performance with a maximum luminous efficiency (LE) of 13.59 cd/A and a maximum brightness of 5529 cd/m2, while the device with undoped F127 as ETL only showed a maximum LE of 8.78 cd/A and a maximum brightness of 2952 cd/m2. The effects of the doping concentration, cations and anions of the alkali metal salts on the performance of the resulting devices were investigated. It was found that most of the alkali metal salt dopants can dramatically enhance the electron transport capability of F127 ETL and the performance of the resulting devices was greatly improved.

Preparation and irradiation of Pluronic F127-based thermoreversible and mucoadhesive hydrogel for local delivery of naproxen

To improve physical properties and modulate the mucoadhesive hydrogel formulation via cross-linking by radiation, hydrogels were prepared using thermoreversible polymer Pluronic F127 (PF127) and mucoadhesive polymer carbopol 934P (C934P). As a model drug, naproxen was loaded in the hydrogel formulation. Sol-gel transition temperatures of hydrogels were measured by the tube-inversion method. The mucoadhesive potential of each formulation was determined by measuring the force required to detach the formulation from oral mucosal tissue. To strengthen the mechanical properties, the formulations were irradiated using an electronic beam. Drug release from the hydrogels and the cytotoxicity of each formulation were investigated. Sol-gel transition temperatures of the formulations were decreased by the addition of carbopol and were close to body temperature. The mucoadhesive force of the PF127 formulation was increased by addition of carbopol. In vitro release was sustained and the release rate was reduced by the addition of carbopol. After irradiation, the mucoadhesive force was increased about five-fold especially in the case of PF127 23% (9.7 kPa) and in vitro release was not sustained further. In conclusion, the use of a PF127 formulation incorporating a mucoadhesive polymer could effectively and safely improve oral residence time and absorption of naproxen. Irradiated formulations showed permanent cross-linking and improved properties.

Assembly of mesoporous indium tin oxide electrodes from nano-hydroxide building blocks

We describe the elaboration of nanostructured transparent conducting indium tin oxide (ITO) materials that is based on controlled self-assembly of ultra-small indium tin hydroxide nanoparticles. We developed a strategy for preparing nanosized, nearly spherical and highly dispersible nanoparticles of indium tin hydroxide (“nano-hydroxides”), which can be assembled into regular mesoporous architectures directed by a commercially available Pluronic polymer. The assembled structures are easily transformed into conducting crystalline mesoporous ITO films by a mild heat treatment at 300 °C. The resulting ITO layers feature a regular mesoporosity with a mesostructure periodicity of about 13 ± 2 nm, high surface area of 190 m2 cm−3, porosity of 44% and electrical conductivity up to 9.5 S cm−1. The ITO films can accommodate large amounts of redox-active molecules and serve as efficient conducting electrodes with a very high surface area. The perfect dispersibility of nano-hydroxides without any stabilizing agents, their preferential interaction with the hydrophilic part of amphiphilic molecules leading to their self-assembly, and a facile transformation of the assembled nano-hydroxides into crystalline ITO with similar morphology make the nano-hydroxides very attractive building blocks for the elaboration of nanostructured ITO materials. We believe that the nano-hydroxides can become universal building blocks for the fabrication of crystalline ITO materials with arbitrary nano-morphologies.

Incorporation of tungsten oxide in mesoporous silica: Catalytic epoxidation of olefins using sodium-bi-carbonate as co-catalyst

Tungsten oxide incorporated mesoporous molecular sieve (WO3–SBA-15) composite was successfully synthesized via one-step hydrothermal process using tetraethylorthosilicate (TEOS) as the silica source, sodium tungstate as the tungsten precursor, and pluronic P123 triblock polymer (EO20PO70EO20, Mav=5800) as a structure-directing agent. The material was characterized by small angle X-ray diffraction (SAX), transmission electron microscopy (TEM), nitrogen sorption measurement and Fourier transform infrared spectroscopy. The catalyst showed excellent catalytic efficiency in epoxidation reactions with various olefinic compounds using H2O2 as oxidant and NaHCO3 as co-catalyst. The solid catalyst can be recovered after reaction and can be reused for several times in catalytic reactions without any significant loss of activity.

Novel formulations enhance the thermal stability of live-attenuated flavivirus vaccines

Thermal stability is important for the manufacture, distribution and administration of vaccines, especially in tropical developing countries, where particularly adverse field conditions exist. Current live-attenuated flavivirus vaccines exhibit relatively poor liquid stability in clinical settings, and clinicians are instructed to discard the yellow fever vaccine 1h after reconstitution. We have identified novel combinations of excipients that greatly enhance the thermal stability of live-attenuated DEN-2 PDK-53-based flavivirus vaccine candidates. Liquid formulations comprising a sugar, albumin and a pluronic polymer minimized the loss of flavivirus infectious titer to less than 0.5log10pfu after storage for at least 8h at 37°C, 7 days at room temperature or at least 11 weeks at 4°C. Additionally, these formulations prevented reduction of viral infectivity after two freeze–thaw cycles of virus. Formulated candidate vaccines were readily lyophilized and reconstituted with minimal loss of viral titers. In mice, the formulations were safe and did not hinder the ability of the vaccine virus to generate a potent, protective immune response. These formulations provided significantly greater liquid-phase stability than has been reported previously for other flavivirus vaccine formulations. The enhanced thermal stability provided by the formulations described here will facilitate the effective distribution of flavivirus vaccines worldwide.

Catalytic performance of subtilisin immobilized without covalently attachment on surface-functionalized mesoporous silica materials

Mesoporous silica (MPS) materials were synthesized using cetyltrimethylammonium bromide or amphiphilic pluronic polymer P123 (EO20PO70EO20) as structure-directing agent. MPS samples were characterized by FE-SEM and N2 adsorption-desorption isotherms, respectively. Subtilisin from Bacillus licheiformis (4.1 × 7.8 × 3.7 nm) was easily immobilized by a direct one-step immobilization process onto MPS with different organo-functinalized surfaces. However, enzyme immobilized on MPS modified with 3-mercaptopropyl group strongly reduced its enantioselectivity. Denaturation temperature of immobilized subtilisin shifted to a high temperature compared to free-enzyme. These biocatalysts on MPS particles retained about 30% of original activity even after 5 cycles of recycle use.

A New Angle on Pluronic Additives: Advancing Droplets and Understanding in Digital Microfluidics

Biofouling in microfluidic devices limits the type of samples which can be handled and the duration for which samples can be manipulated. Despite the cost of disposing fouled devices, relatively few strategies have been developed to tackle this problem. Here, we have analyzed a series of eight amphiphilic droplet additives, Pluronic coblock polymers of poly(propylene oxide) (PPO) and poly(ethylene oxide) (PEO), as a solution to biofouling in digital microfluidics using serum-containing cell culture media as a model fluid. Our analysis shows that species with longer PPO chains are superior for enabling droplet motion and reducing biofouling. Two of the tested species, L92 and P105, were found to lengthen device lifetimes by 2-3 times relative to additives used previously when used at optimal concentrations. Pluronics with low PEO content such as L92 were found to be cytotoxic to an immortalized mammalian cell line, and therefore we recommend that Pluronic additives with greater or equal to 50% PEO composition, such as P105, be used for digital microfluidic applications involving cells. Finally, contact angle measurements were used to probe the interaction between Pluronic-containing droplets and device surfaces. Strong correlations were found between various types of contact angle measurements and the capacity of additives to reduce biofouling, which suggests that contact angle measurements may be useful as a tool for rapidly screening new candidates for the potential to reduce biofouling. We propose that this study will be useful for scientists and engineers who are developing digital microfluidic platforms for a wide range of applications involving protein-containing solutions, and in particular, for applications involving cells.

Pluronic–lysozyme conjugates as anti-adhesive and antibacterial bifunctional polymers for surface coating

This paper describes the preparation and characterization of polymer–protein conjugates composed of a synthetic triblock copolymer with a central polypropylene oxide (PPO) block and two terminal polyethylene oxide (PEO) segments, Pluronic F-127, and the antibacterial enzyme lysozyme attached to the telechelic groups of the PEO chains. Covalent conjugation of lysozyme proceeded via reductive amination of aldehyde functionalized PEO blocks (CHO-Pluronic) and the amine groups of the lysine residues in the protein. SDS-PAGE gel electrophoresis together with MALDI-TOF mass spectrometry analysis revealed formation of conjugates of one or two lysozyme molecules per Pluronic polymer chain. The conjugated lysozyme showed antibacterial activity towards Bacillus subtilis. Analysis with a quartz crystal microbalance with dissipation revealed that Pluronic–lysozyme conjugates adsorb in a brush conformation on a hydrophobic gold-coated quartz surface. X-ray photoelectron spectroscopy indicated surface coverage of 32% by lysozyme when adsorbed from a mixture of unconjugated Pluronic and Pluronic–lysozyme conjugate (ratio 99:1) and of 47% after adsorption of 100% Pluronic–lysozyme conjugates. Thus, bifunctional brushes were created, possessing both anti-adhesive activity due to the polymer brush, combined with the antibacterial activity of lysozyme. The coating having a lower degree of lysozyme coverage proved to be more bactericidal.