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PubMed2006

Role of silicon contamination on calcification of hydrophilic acrylic intraocular lenses.

PURPOSE: To verify the presence of the element silicon on hydrophilic acrylic intraocular lenses (IOLs) explanted because of calcification. DESIGN: Interventional case series with clinicopathological correlation. METHODS: Twenty explanted IOLs with surface deposits (MemoryLens), and 20 with deposits mostly within their optic substance (SC60B-OUV and Aqua-Sense; 10 each) were used. After gross, microscopic, and histochemical analyses to confirm the presence of deposits, the lenses underwent scanning electron microscopy (SEM) with energy dispersive x-ray spectroscopy (EDS) for elemental composition, on the external surface of MemoryLens IOLs, and on the surface and internal substance of SC60B-OUV and Aqua-Sense IOLs. The weight percentage of the element silicon was obtained at the level of deposits, and at adjacent deposit-free areas in all lenses. RESULTS: Scanning electron microscopy (SEM) coupled with EDS confirmed that the composition of the deposits was calcium/phosphate in all cases. The element silicon was found in all 40 lenses, on all areas analyzed. The silicon weight percentage was higher at the level of the deposits. The presence of aluminum on five MemoryLens IOLs, and in most of the SC60B-OUV and Aqua-Sense lenses might be related to scattering from the aluminum mounting stubs used for surface analyses. CONCLUSIONS: Silicone compounds have been implicated in the calcification of another hydrophilic acrylic design (Hydroview). They may also have a role in the calcification of other hydrophilic acrylic IOLs. Further investigation on the relationship between the presence of the element silicon and the silicone compounds found on calcified hydrophilic acrylic lenses is necessary.

Acrylic Resins↗

PubMed2004

Influence of mechanical and chemical polishing in the solubility of acrylic resins polymerized by microwave irradiation and conventional water bath.

OBJECTIVES: The aim of this work was to evaluate the solubility of acrylic resin activated by microwave irradiation (MI) or water bath (WB), when submitted to chemical (CP) or mechanical (MP) polishing. METHODS: Forty acrylic resin samples were made and processed either by water bath (74 +/- 1 degrees C, 9 h) or microwave irradiation (500 W, 3 min). After deflasking, the samples were finished with aluminum oxide sandpapers in decreasing granulations till reaching similar dimensions. The samples were divided into four groups according to the association between kind of polymerization and polishing: A (WB + CP), B (WB + MP), C (MI + CP) and D (MI + MP). Solubility test was performed for each group and percentile solubility was calculated. Data were statistically analyzed using variance analysis and Kruskal-Wallis. RESULTS: The average of percentile solubility (%) was obtained: A = 0.07, B = 0.02, C = 0.04, D = -0.14, however, no significant difference was found between types of polishing in the samples polymerized by water bath (A and B). When processed by microwave irradiation (C and D), there was significant difference between the applied methods of polishing, so that mechanical polishing lead to a lower solubility. SIGNIFICANCE: Solubility is a property of acrylic resins, representing not reacted substances releasing that could promote tissular reactions in prosthesis users. The association between polymerization by microwave irradiation and mechanical polishing showed less residual substances releasing for heat-cured acrylic resins, reducing the probability of developing tissular reactions.

Acrylic Resins↗

PubMed2005

Interactions of sodium montmorillonite with poly(acrylic acid).

The chemical-structural modifications of the natural clay sodium montmorillonite during interaction with poly(acrylic acid) were studied mainly by X-ray photoemission spectroscopy. Samples of modified montmorillonite were prepared from the reaction of sodium montmorillonite ( approximately 0.5 g) and an aqueous solution of poly(acrylic acid) (pH approximately 1.8, 50 g) at varying temperatures. X-ray diffraction indicated that the montmorillonite interlayer space ( approximately 13 A), formed by regular stacking of the silicate layers (dimension approximately 1x1000 nm), expanded to approximately 16 A as the reaction was carried out at room temperature and at 30 degrees C. At 60 degrees C, the interlayer space further expanded to approximately 20 A. The results of X-ray photoemission spectroscopy indicated that poly(acrylic acid) molecules exchange sodium ions on the surface of the silicate layers. These combined results allowed development of a reaction model that explains the dependency of the interlayer expansion with temperature. Information concerning the surface chemical reactions and systematic increases in the interlayer distances is particularly useful if montmorillonite and poly(acrylic acid) are to be used for formation of nanocomposite materials.

Acrylic Resins↗

PubMed2005

Comparison of tilt and decentration of 1-piece and 3-piece hydrophobic acrylic intraocular lenses.

PURPOSE: To determine the amount of tilt and decentration of 1-piece and 3-piece hydrophobic acrylic intraocular lenses (IOLs) in patients having cataract surgery. SETTING: Department of Ophthalmology, Gulhane Military Medical Academy and Medical School, Ankara, Turkey. METHODS: Eighty-eight patients having phacoemulsification with IOL implantation were divided into 2 groups. One group received a 3-piece hydrophobic acrylic IOL with 12.5 mm poly(methyl methacrylate) haptics and the other, a 1-piece hydrophobic acrylic IOL with 12.5 mm haptics. The amount of IOL decentration and tilt was quantitated using Purkinje reflections and photographic documentation at the last postoperative control. The results of the 2 groups were compared. RESULTS: Bag fixation of the IOL and an intact continuous curvilinear capsulorhexis (CCC) were confirmed in all cases at the last postoperative control, which was at a mean of 27.1 months +/- 5.4 (SD) and 26.7 +/- 4.4 months in the 3-piece group and 1-piece group, respectively (P = 0.659). There was no significant difference between groups in the percentage of patients with measurable tilt and decentration and of patients without measurable tilt and decentration (P = .956). The mean IOL tilt was 2.72 +/- 0.55 degrees in the 3-piece group and 2.70 +/- 0.84 degrees in the 1-piece group and the mean IOL decentration, 0.39 +/- 0.13 mm and 0.34 +/- 0.08 mm, respectively. There were no significant between-group differences in tilt or decentration (P = .897 and P = .103, respectively). CONCLUSION: There were no significant differences in tilt and decentration between 1-piece and 3-piece hydrophobic acrylic IOLs in eyes with capsular bag IOL implantation and an intact CCC.

Acrylic Resins↗

PubMed2005

Cell adhesion to acrylic intraocular lens associated with lens surface properties.

PURPOSE: To examine the number cells adhering to acrylic intraocular lenses (IOLs) having different degrees of surface roughness and acrylic IOLs having different contact angles. SETTING: Department of Ophthalmology, Tokyo Medical University Hospital, Tokyo, Japan. METHODS: In this study, VA-60 CB acrylic IOLs were used. After different durations of polishing of the optics, the roughness values of the lenses were set at 10.0 nm, 2.5 nm, and 0.7 nm. Intraocular lenses were also chemically coated to achieve angles of contact of 100 degrees and 57.5 degrees, with untreated IOLs having a 93.5-degree angle of contact. Intraocular lenses were cultured for 96 hours in 1 x 10(7) spleen cells/mL of developed experimental autoimmune uveoretinitis, and the number of cells adhering to the IOLs was counted. RESULTS: Fewer cells adhered to the optics of IOLs with lower roughness values, and fewer cells adhered to the IOL surface with increased contact angles. CONCLUSION: Hydrophobic optics with small roughness values of acrylic IOLs may reduce the number of adherent cells and escaped the unexpected inflammatory cell reaction associated with intraocular inflammation in the eye.

Acrylic Resins↗

PubMed2006

Hydrogen bonding interaction between acrylic esters and monohydric alcohols in non-polar solvents: An FTIR study.

The association between acrylic esters (methyl methacrylate, ethyl methacrylate and butyl methacrylate) and some monohydric (primary, secondary and tertiary) alcohols in non-polar solvents, viz. n-heptane, CCl4 and benzene has been investigated by means of FTIR spectroscopy. The most likely association complex between alcohol and acrylic ester is 1:1 stoichiometric complex through the hydroxyl group of alcohol and the carbonyl group of acrylic ester. The formation constant of the 1:1 complexes has been calculated using Nash method. It appears that the primary alcohols have larger formation constant than the secondary and tertiary alcohols. The results show that the proton donating power of the alcohols decreases in the order primary>secondary>tertiary and the association constant increases with the increase in carbon chain of the alkyl group of acrylic esters and alcohols. Also the results show a significant dependence of the association constant upon the solvents used. The solvent effect on the formation of hydrogen bond equilibria is discussed in terms of specific interaction between the solute and solvent.

Acrylates↗

PubMed2000

A tape-stripping method for measuring dermal exposure to multifunctional acrylates.

Current methods for measuring dermal exposure to skin irritants and allergens, such as acrylates, have significant drawbacks for exposure assessment. A noninvasive sampling method has been developed and tested for measuring dermal exposure to a multifunctional acrylate employing a tape stripping of the nonviable epidermis (stratum corneum). Samples were subsequently extracted and a gas chromatographic method was employed for quantitative analysis of tripropylene glycol diacrylate (TPGDA). This method was tested in 10 human volunteers exposed to an a priori determined amount of TPGDA or a UV-radiation curable acrylate coating containing TPGDA (UV-resin) at different sites on hands and arms. On the average, the first tape stripping removed 94% (coefficient of variation 16%) of the theoretical quantity of deposited TPGDA and 89% (coefficient of variation 15%) of the theoretical quantity of deposited TPGDA in UV-resin 30min after exposure. Quantities of TPGDA recovered from two consecutive tape strippings accounted for all of the test agent, demonstrating both the efficiency of the method to measure dermal exposure and the potential to determine the rate of absorption with successive samples over time. In general, the amount removed by the first stripping was greater for TPGDA than for UV-resin while the second stripping removed approximately 6 and 21% of TPGDA and UV-resin, respectively. However, when the amounts removed with the first tape stripping for TPGDA or UV-resin from the five different individual sites were compared, no significant differences were observed (P=0.111 and 0.893, respectively). No significant difference was observed in recovery between TPGDA and UV-resin for the first tape stripping when calculated as a percentage of the theoretical amount (P=0.262). The results indicate that this tape-stripping technique can be used to quantify dermal exposure to multifunctional acrylates.

Acrylates↗

PubMed1999

Disinfection of denture base acrylic resin.

STATEMENT OF PROBLEM: During repair or adjustments of acrylic resin removable complete and partial dentures, particles of the acrylic resin from the interior of the prosthesis may expose dental personnel to microbial health hazards if the prosthesis has not been thoroughly disinfected. PURPOSE: This study investigates the efficacy of a commercially prepared microbial disinfectant (Alcide) on the external and internal surfaces of acrylic resins. MATERIAL AND METHODS: Four groups of acrylic resin were incubated in an experimental model to simulate the oral environment over time. Specimens were treated in 2 groups, disinfected and not disinfected, and then further grouped by breaking and not breaking. Analysis was performed with microbial colony counts, SEM, and statistical analyses. RESULTS: Viable microorganisms still remain on the internal and external surfaces of treated resins. CONCLUSION: Chlorine dioxide reduces, but does not eliminate, viable microorganisms on these dental prostheses.

Acrylic Resins↗

PubMed1999

Effect of processing method on the dimensional accuracy and water sorption of acrylic resin dentures.

STATEMENT OF PROBLEM: Acrylic resin complete dentures exhibit certain unavoidable dimensional changes. Processing shrinkage and expansion due to water uptake are 2 important aspects influencing dimensional accuracy. PURPOSE: This study investigated linear dimensional changes and water sorption of dentures processed by dry and wet heat with different rates of cooling. METHODS: Fine crosses marked on tinfoil inserts were placed at the incisive papilla and tuberosity regions of edentulous maxillary casts and incorporated into the dentures during polymerization by 3 processing techniques. A traveling microscope was used to measure the distances between the reference points to determine dimensional changes. Water uptake and content were determined by the mass changes of the dentures with an electronic balance. Data of linear dimensional change and water sorption were analyzed by multivariate analysis of variance and analysis of variance, respectively. Bonferroni simultaneous confidence intervals (95%) were applied for multiple comparison. RESULTS: Dry heat-processed and water bath-processed acrylic resin dentures did not exhibit significant differences in shrinkage (0.42% to 0.58%) at water saturation. Amounts of water sorption of dentures processed by dry and wet heat (0.50 and 0.48 mass%, respectively) were not significantly different, and their associated expansion did not entirely compensate for the processing shrinkage. The initial water content of dry heat-processed dentures (1.77 mass%) was unexpectedly slightly higher than that of wet heat-processed dentures (1.68 mass%). The rate at which the dentures cooled did not affect their initial water content and subsequent water uptake. CONCLUSIONS: Water uptake of dry and wet heat-processed acrylic resin dentures after deflasking was in both cases low, and the dentures did not reveal significant differences in shrinkage at water saturation. Air oven-processed and water bath-processed acrylic resin dentures show similar dimensional shrinkage at water saturation.

Acrylic Resins↗

PubMed2001

Aqueous flare induced by heparin-surface-modified poly(methyl methacrylate) and acrylic lenses implanted through the same-size incision in patients with diabetes.

PURPOSE: To compare the degree of blood-aqueous barrier (BAB) breakdown in eyes of diabetic patients after phacoemulsification and implantation of heparin-surface-modified poly(methyl methacrylate) (PMMA) or soft hydrophobic acrylic intraocular lenses (IOLs) performed using the same technique with the same incision size to determine the influence of the IOLs on postoperative inflammation independent of other surgical factors. SETTING: Department of Ophthalmology, University of Paris XIII, Bobigny, France. METHODS: In a prospective study, 44 eyes of 31 diabetic patients with or without mild to moderate diabetic retinopathy were randomly assigned to receive an HSM PMMA IOL (22 eyes) or a soft hydrophobic acrylic IOL (22 eyes) after standardized phacoemulsification surgery. Both types of IOLs had a 6.0 mm optic, were inserted unfolded, and were placed in the bag through a calibrated 6.0 mm superior scleral incision. Anterior chamber flare was measured preoperatively and 1, 7, 30, and 240 days postoperatively using the Kowa 500 laser flare meter. RESULTS: The mean flare value was higher on the first postoperative day in both groups. There were no statistically significant between-group differences in flare scores or clinical parameters preoperatively or at any postoperative visit. CONCLUSIONS: No significant difference was observed in inflammation between eyes having HSM PMMA IOL implantation or those having soft hydrophobic acrylic IOL implantation through the same-size incision. This indicates that hydrophobic acrylic and HSM PMMA materials induce the same degree of BAB breakdown after phacoemulsification in eyes of diabetic patients.

Acrylic Resins↗

PubMed2001

Membranous proliferation of lens epithelial cells on acrylic, silicone, and poly(methyl methacrylate) lenses.

PURPOSE: To determine whether intraocular lens (IOL) material influences the membranous proliferation of lens epithelial cells (LECs) on the anterior surface of the IOL. SETTING: Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan. METHODS: This prospective study included 87 eyes of 87 consecutive patients who had cataract surgery with IOL implantation. Patients were randomly assigned to receive a single-piece poly(methyl methacrylate) (PMMA) IOL, a 3-piece silicone IOL, or a 3-piece acrylic IOL. Postoperatively, the IOL optic was examined by slitlamp microscopy at 1 and 10 days and 1, 2, and 3 months to determine the incidence, duration, and extent of membranous LEC proliferation. The optic was also examined at 6, 9, and 12 months if proliferation persisted. RESULTS: Thirteen eyes were excluded from analysis because of incomplete coverage of the IOL rim by the anterior capsule margin; 74 remaining eyes were studied. All patients obtained good postoperative visual acuity (20/25 or better). Incidence (P =.0024) and duration (P =.0002) of membranous LEC proliferation with the acrylic IOL was greater than with the other 2 types. Proliferation on the acrylic IOL was more extensive than on the PMMA IOL 10 days postoperatively (P <.05) and on the silicone IOL at 10 days (P <.01) and 1 month (P <.01). However, LEC proliferation on the 3 types of IOLs usually decreased by the third postoperative month, and proliferation did not disturb visual acuity. CONCLUSIONS: The material of an IOL influenced membranous proliferation of LECs on its anterior surface. Proliferation on the acrylic IOL persisted longer than on the other 2 types but did not cause visual symptoms.

Acrylic Resins↗

PubMed2002

Relationship of AcrySof acrylic and PhacoFlex silicone intraocular lenses to visual acuity and posterior capsule opacification.

PURPOSE: To compare the changes in visual acuity and the development of posterior capsule opacification (PCO) with AcrySof acrylic intraocular lenses (IOLs) (Alcon Laboratories) and second-generation PhacoFlex silicone IOLs (Allergan ). SETTING: Eye Associates of New Mexico and Southwest Colorado, Albuquerque, New Mexico, USA. METHODS: Medical charts of patients having cataract extraction with implantation of an AcrySof MA30BA or MA60BM (MA30/60) or PhacoFlex SI-30NB or SI-40NB (SI-30/40) IOL between January 1995 and June 1997 were abstracted. Analyzed were the changes in visual acuity and development of PCO 1 month postoperatively and at the last available ophthalmologist visit or the visit before neodymium:YAG (Nd:YAG) capsulotomy. RESULTS: Patients with MA30/60 acrylic IOLs were significantly older, had a worse preoperative best corrected visual acuity (BCVA), and had more concomitant ocular diseases than those with SI-30/40 silicone IOLs. The change in BCVA from preoperatively to 1 month postoperatively was equivalent in the 2 lens groups. The BCVA declined from 1 month postoperatively to the last recorded or pre-Nd:YAG visit. This decline was greater in eyes with SI-30/40 silicone IOLs than in those with MA30/60 acrylic IOLs. Although the decrease in BCVA between IOL types was not significantly different, eyes with a SI-30/40 silicone IOL were significantly more likely to develop PCO and have Nd:YAG capsulotomy. Eyes developing PCO had a statistically significant decline in BCVA from 1 month postoperatively to the last/pre-Nd:YAG visit. CONCLUSIONS: The MA30/60 acrylic lenses were associated with lower PCO and Nd:YAG capsulotomy rates than second-generation SI-30/40 silicone IOLs. Patients with MA30/60 IOLs also tended to have less of a decrease in visual acuity than patients with SI-30/40 silicone lenses, probably as a result of the difference in PCO rates between groups.

Acrylic Resins↗

PubMed2004

Empty-bag technique for acrylic intraocular lens implantation using Healon5.

PURPOSE: To determine how often the empty-bag technique (EBT) for injecting an acrylic foldable intraocular lens (IOL) into the capsular bag using Healon5 (sodium hyaluronate 2.3%) will require a 2-compartment technique to remove the ophthalmic viscosurgical device (OVD) and compare this with that of a standard injection method using Healon5. SETTING: Cincinnati Eye Institute and Ambulatory Surgical Center, Cincinnati, Ohio, USA. METHODS: Forty-one eyes of 40 patients were randomly assigned to 1 of 2 groups. In Group A, standard capsular bag expansion was performed with Healon5 before implantation of an acrylic posterior chamber (PC) IOL. In Group B, Healon5 was placed in the anterior chamber followed by balanced salt solution expansion of the capsular bag before acrylic PC IOL implantation. In all patients, complete OVD removal was attempted with the automated aspiration tip anterior to the optic (rock 'n roll technique). The number of patients in each group who required placement of the aspiration tip posterior to the optic for complete removal was compared. Early postoperative intraocular pressure (IOP) was also compared. RESULTS: In Group A, 15 (75%) of 20 eyes required placement of the aspiration tip posterior to the optic for complete OVD removal and in Group B, 1 (0.05%) of 20 eyes. The postoperative IOP was similar in both groups. CONCLUSIONS: The EBT decreased the likelihood that a 2-compartment OVD removal method would be necessary when using Healon5 for acrylic PC IOL implantation. The limitations of this new technique must be fully understood before it is used.

Acrylic Resins↗

PubMed1998

Transscleral fixation of acrylic intraocular lenses in the absence of capsular support through 3.5 mm self-sealing incisions.

PURPOSE: To evaluate the safety and efficacy of transscleral ciliary sulcus fixation of acrylic intraocular lenses (IOLs) through small incisions in the management of secondary IOL implantation. SETTING: Department of Ophthalmology, Osaka Rosai Hospital, Osaka, Japan. METHODS: This retrospective study consisted of 28 patients (30 eyes) who had transscleral fixation of acrylic IOLs through 3.5 mm incisions. All patients were followed for a minimum of 6 months in several different clinical settings. Data on visual acuity, keratometry, and central corneal endothelial cell count were evaluated preoperatively and postoperatively. The refractive error achieved and incidence of postoperative complications were determined. RESULTS: Uncorrected visual acuity (UCVA) improved in all eyes. Of the 18 eyes without pre-existing pathology, 11 (61.1%) had a UCVA of 20/40 or better from 1 week postoperatively. Best corrected visual acuity was unchanged in 24 eyes (80.0%) and improved by 2 Snellen lines or more in 5 eyes (16.7%) at the final examination. Self-sealing wound adaptation was achieved in 25 eyes (83.3%). The mean scalar shift in keratometric cylinder was 1.25 diopters (D) at 1 day postoperatively, 1.17 D at 1 week, and 1.06 D at 3 months. The rate of central corneal endothelial loss 6 months postoperatively averaged 7.84%. No intraoperative complications that were directly associated with acrylic IOL implantation occurred. Postoperative complications that included transient ocular hypertension, slight vitreous hemorrhage, and IOL malposition were found in a small population but resolved spontaneously without further surgical intervention. CONCLUSIONS: The good visual outcomes and low incidence of complications achieved in the present study indicate that acrylic IOLs positioned through small incisions might be considered for ciliary sulcus fixation. However, evaluation of this technique in a large population over the long term is required.

Acrylic Resins↗

PubMed2001

Poly(ethylene-co-acrylic acid) stationary phases for the separation of shape-constrained isomers.

A new approach for the synthesis of long alkyl chain length stationary phases for use in reversed-phase liquid chromatography is described. Poly(ethylene-co-acrylic acid) copolymers (i.e., (-CH2CH2-)x[CH2CH(CO2H)-]y) with different levels of acrylic acid were covalently bonded to silica via glycidoxypropyl or aminopropyl linkages. 13C cross polarization magic angle spinning (CP/MAS) nuclear magnetic resonance (NMR) spectroscopy was used to characterize the new reversed-phase materials. Aspects of shape selectivity were evaluated for six different columns with Standard Reference Material (SRM) 869a, Column Selectivity Test Mixture for Liquid Chromatography. Selectivity for isomer separations was enhanced for stationary phases prepared with poly(ethylene-co-acrylic acid) containing a mass fraction of 5% acrylic acid. The relationship between alkyl conformation and chromatographic properties was studied by 13C magic angle spinning (MAS) NMR measurements, and correlations were made with the composition of the polymer. Finally, the effectiveness of this phase is demonstrated by the separation of several beta-carotene isomers.

Acrylic Resins↗

PubMed2006

Glycine derived polymerizable cosurfactant in the synthesis of functionalized poly(butyl acrylate) nanolatexes.

The approach of employing N-glycinylmaleamic acid (NGMA) as an efficient cosurfactant to provide microemulsion polymerization of butyl acrylate using a weight ratio of sodium dodecyl sulfate (SDS)/butyl acrylate (BA) at <or=1.5, which is lower than that employed in previous experiments, has been demonstrated. The narrow polydispersity index at 1.36-1.48 of poly(butyl acrylate) copolymers from investigated microemulsion polymerization reactions evidences the promotion of a controlled polymerization reaction, in contrast to the solution polymerization method generating polymers with higher polydispersity index at 3.15-4.23. The enhanced incorporation of NGMA at approximately 0.35 m in the copolymer demonstrates the merits of the proximity effect enabled in the microemulsion polymerization reaction. The incorporation of NGMA promotes rigidity of the polymer chain as suggested by a higher Tg of -16.8 degrees C for the copolymer in comparison to that of the poly(butyl acrylate) homopolymer.

Acrylates↗

PubMed2002

Integration of polyaniline/poly(acrylic acid) films and redox enzymes on electrode supports: an in situ electrochemical/surface plasmon resonance study of the bioelectrocatalyzed oxidation of glucose or lactate in the integrated bioelectrocatalytic systems.

Electropolymerization of aniline in the presence of poly(acrylic acid) on Au electrodes yields a polyaniline/poly(acrylic acid) composite film, exhibiting reversible redox functions in aqueous solutions at pH = 7.0. In situ electrochemical-SPR measurements are used to identify the dynamics of swelling and shrinking of the polymer film upon the oxidation of the polyaniline (PAn) to its oxidized state (PAn(2+)) and the reduction of the oxidized polymer (PAn(2+)) back to its reduced state (PAn), respectively. Covalent attachment of N(6)-(2-aminoethyl)-flavin adenin dinucleotide (amino-FAD, 1) to the carboxylic groups of the composite polyaniline/poly(acrylic acid) film followed by the reconstitution of apoglucose oxidase on the functional polymer yields an electrically contacted glucose oxidase of unprecedented electrical communication efficiency with the electrode: electron-transfer turnover rate approximately 1000 s(-1) at 30 degrees C. In situ electrochemical-SPR analyses are used to characterize the bioelectrocatalytic functions of the biomaterial-polymer interface. The current responses of the bioelectrocatalytic system increase as the glucose concentrations are elevated. Similarly, the SPR spectra of the system are controlled by the concentration of glucose. The glucose concentration controls the steady-state concentration ratio of PAn/PAn(2+) in the film composition. Therefore, the SPR spectrum of the film measured upon its electrochemical oxidation is shifted from the spectrum typical for the oxidized PAn(2+) at low glucose concentration to the spectrum characteristic of the reduced PAn at high glucose concentration. Similarly, the polyaniline/poly(acrylic acid) film acts as an electrocatalyst for the oxidation of NADH. Accordingly, an integrated bioelectrocatalytic assembly was constructed on the electrode by the covalent attachment of N(6)-(2-aminoethyl)-beta-nicotinamide adenine dinucleotide (amino-NAD(+), 2) to the polymer film, and the two-dimensional cross-linking of an affinity complex formed between lactate dehydrogenase and the NAD(+)-cofactor units associated with the polymer using glutaric dialdehyde as a cross-linker. In situ electrochemical-SPR measurements are used to characterize the bioelectrocatalytic functions of the system. The amperometric responses of the system increase as the concentrations of lactate are elevated, and an electron-transfer turnover rate of 350 s(-1) between the biocatalyst and the electrode is estimated. As the PAn(2+) oxidizes the NADH units generated by the biocatalyzed oxidation of lactate, the PAn/PAn(2+) steady-state ratio in the film is controlled by the concentration of lactate. Accordingly, the SPR spectrum measured upon electrochemical oxidation of the film is similar to the spectrum of PAn(2+) at low lactate concentration, whereas the SPR spectrum resembles that of PAn at high concentrations of lactate.

Acrylic Resins↗

PubMedDate not supplied

Application of whole cell rhodococcal biocatalysts in acrylic polymer manufacture.

Rhodococci are ubiquitous in nature and their ability to metabolise a wide range of chemicals, many of which are toxic, has given rise to an increasing number of studies into their diverse use as biocatalysts. Indeed rhodococci have been shown to be especially good at degrading aromatic and aliphatic nitriles and amides and thus they are very useful for waste clean up where these toxic chemicals are present. The use of biocatalysts in the chemical industry has in the main been for the manufacture of high-value fine chemicals, such as pharmaceutical intermediates, though investigations into the use of nitrile hydratase, amidase and nitrilase to convert acrylonitrile into the higher value products acrylamide and acrylic acid have been carried out for a number of years. Acrylamide and acrylic acid are manufactured by chemical processes in vast tonnages annually and they are used to produce polymers for applications such as superabsorbents, dispersants and flocculants. Rhodococci are chosen for use as biocatalysts on an industrial scale for the production of acrylamide and acrylic acid due to their ease of growth to high biomass yields, high specific enzyme activities obtainable, their EFB class 1 status and robustness of the whole cells within chemical reaction systems. Several isolates belonging to the genus Rhodococcus have been shown in our studies to be among the best candidates for acrylic acid preparation from acrylonitrile due to their stability and tolerance to high concentrations of this reactive and disruptive substrate. A critical part of the selection procedure for the best candidates during the screening programme was high purity product with very low residual substrate concentrations, even in the presence of high product concentrations. Additionally the nitrile and amide substrate scavenging ability which enables rhodococci to survive very successfully in the environment leads to the formation of biocatalysts which are suitable for the removal of low concentrations of acrylonitrile and acrylamide in waste streams and for the removal of impurities in manufacturing processes.

Acrylic Resins↗