Methylene Blue polymers

Lactate dehydrogenase, alcohol dehydrogenase Laponite gel-methylene blue polymer Biosensor [47]... 

Release of tetracycUne hydrochloride from PCL fibers was evaluated as a means of controlled administration to periodontal pockets (69). Only small amounts of the drug were released rapidly in vitro or in vivo, and poly(ethylene-co-vinyl acetate) gave superior results. Because Fickian diffusion of an ionic hydrochloride salt in a UpophiUc polymer is unlikely, and because PCL and EVA have essentially identical Fickian permeabilities, we attribute this result to leaching of the charged salt by a mechanism similar to release of proteins from EVA (73). Poly-e-caprolactone pellets have been found unsuitable for the release of methylene blue, another ionic species (74,75). In this case, blending PCL with polyvinyl alcohol (75% hydrolyzed) increased the release rate. 

The rate of polymer erosion in the presence of incorporated anhydride and release of an incorporated drug depends on the pK of the diacid formed by hydrolysis of the anhydride and its concentration in the matrix (20). This dependence is shown in Fig. 7 for 2,3-pyridine dicarboxylic anhydride and for phthaUc anhydride. In this study, methylene blue was used as a marker. The methylene blue release rate depends both on the pK and on the concentration of diacid hydrolysis product in the matrix. However, at anhydride concentrations greater than 2 wt%, the erosion rate reaches a limiting value and further increases in anhydride concentration have no effect on the rate of polymer hydrolysis. Presumably at that point Vj, the rate of water intrusion into the matrix, becomes rate limiting. 

Convincing evidence for a surface erosion process is shown in Fig. 8, which shows the concomitant release of the incorporated marker, methylene blue, release of the anhydride excipient hydrolysis product, succinic acid, and total weight loss of the device. According to these data, the release of an incorporated drug from an anhydride-catalyzed erosion of poly (ortho esters) can be unambiguously described by a polymer surface erosion mechanism. 

FIGURE 7 Effect of nature and amount of anhydride on methylene blue release rate from a polymer prepared fi om 3,9-bis(ethylidene-2,4,8,10-tetraoxaspiro[5,5]undecane) and a 35 65 mole ratio of trans-cyclohexane dimethanol and 1,6-hexanediol. (From Ref, 20.)... 

Methylene blue was used as a model drug, and matrices were based upon crosslinked copolymers of sodium acrylate or polymer composites of ferrite. 

Ionic charges of the polymers were determined by photometric colloid titrations in some instances. A known amount of poly(diallyldimethylammonium chloride) was added to the polymer solution at a pH of 2.5. The excess poly(diallyldimethylammonium chloride) was titrated by poly(vinylsulfate) using the adsorption indicator methylene blue. The end point was detected by the photometric detector as the color of the solution changes from blue to violet. For anionic copolymers the colloid titration was conducted at pH values of 2.5 and 10.0 to determine the extent of modification. 

Perni S, Picdrillo C, Pratten J et al. (2009) The antimicrobial properties of light-activated polymers containing methylene blue and gold nanoparticles. Biomaterials 30 89-93... 

It has been shown that methylene blue binds to DNA in a manner similar to that of acridine orange, with the intercalated solute being coplanar with the base pairs at low dye/polymer ratios and low ionic strengths [89]. The induced CD data indicated the existence of two origins for the observed chirality. At low ratios of dye/polymer, the CD is... 

Besides the PVK band (in the UV range) and the dye band a new peak appeared in the photoconductivity spectrum. In the case of Methylene Blue it appears at 490 nm, i.e. between the polymer and the dye bands. This new peak is not a PVK/TCNE band since that appears near 600 nm and it is not a peak of the dye/TCNE complex since it does not vary with the nature of the dye. Although not supported by any other example in the literature, this can be an interesting concept of practical consequences. 

As can be seen from Table 9.12, photochromism is also strongly affected by humidity. It is well known that thiazine and its derivatives undergo photoreduction smoothly in the presence of such activated surfaces as silica gel and alumina with water molecules,37 and that methylene blue is also photochemically reduced in acid solution, even with only available water as the reducing agent38 Therefore the water present in polymer films must produce a thionine-water hydration system, which accelerates the rate of the photoreduction of thionine, as well as promoting the contact of reductants by a plasticizer effect. PVA, used as the matrix, can also play the role of reductant, but its extent may be minor as compared with the added reductant. The effect of water is supported by the fact that a less hydrophilic polymer matrix such as poly(methyl methacrylate) does not exhibit photochromism even though the system contains an appreciable amount of reductants. 

Modihed polymers can also be analyzed by the use of some reactive dyes. Some of the reactive dyes are specihc to the functional groups. Rhodamine 6G can be used to determine the presence of carboxyl functional groups. Similarly, toluidine blue (TBO) and methylene blue can be used to determine the surface carboxyl group whereas methyl orange can be used to determine the presence of amino groups present on the surface of modihed polymers. 

Modified electrodes for this analytical purpose have mostly been formed by electrode adsorption of the mediator systems on the electrode surface or by electropolymerization [24,116]. Recently, for example, NAD(P)H oxidations have been performed on platinum or gold electrodes modified with a monolayer of pyrroloquinoline quinone (PQQ) [117] or on poly(methylene blue)-modified electrodes with different dehydrogenases entrapped in a Nafion film for the amperometric detection of glucose, lactate, malate, or ethanol [118]. In another approach, carbon paste electrodes doped with methylene green or meldola blue together with diaphorase were used for the NADH oxidation [119]. A poly(3-methylthio-phene) conducting polymer electrode was efficient for the oxidation of NADH [120]. By electropolymerization of poly(aniline) in the presence of poly(vinylsulfonate) counterions. 

Figure 5. Gel-permeation chromatograms of (A) cis- and (B) trans-polybutadiene-1,4- (—) undegraded polymer and degraded in the presence of FL-fluoresceine, MB-methylene blue, and RB-Rose Bengal. Concentration of dyes in benzene-methanol (9 1) solution of polyoutadienes was 10- M/1.

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