The pH stimulated reversible loading and release of a cationic dye in a layer-by-layer assembled DNA/PAH film

Electrochemically controlled release of -tetrakis(4-N-methylpyridyl)porphine from layer-by-layer thin films

“…1B). A rapid release of TMPyP in acidic solutions from DNA-containing LbL film was also reported [19,20]. Another feature is a remarkable effect of ionic strength on the rate of release.…”

“…Fig. 1A depicts a typical UV-visible absorption spectrum of TMPyP-adsorbed PAA-PAH film together with spectrum of TMPyP recorded in solution, showing a clear absorption peak at 420 nm originating from TMPyP [19,20]. The amount of TMPyP in the film is shown in Fig.…”

“…For example, the binding and release of methyl orange (MO) in LbL films composed of a thermo-sensitive polymer [15] and cyclodextrin-containing LbL films [18] were studied. α,β,γ ,δ-Tetrakis(4-N-methylpyridyl)porphyrin (TMPyP) has also been used as a model dye for studying its binding and release properties of DNA-containing LbL films [19,20]. The above studies have established that the rate of release of model compounds are highly sensitive to pH and ionic strength of the solution where the model compounds are released.…”

Optical interference effect corrections for absorbance spectra of layer-by-layer thin films bearing covalently bound dye

“…In each polyelectrolyte adsorption step, overcompensation of charge [2] enables cyclic repetition to thicken films, which are readily deposited via spincoating [3,4], spraycoating [5,6], or dipcoating [1,2] processes. PEMLs so produced have already been applied to areas of metal enhanced fluorescence [7], photovoltaic sensitization [8], light-emitting diodes [9], permselective membranes [3], heterogeneous catalysts [10,11], sensors [12,13], microcapsules [3,14], and pH controlled release delivery systems [15,16]. A valuable attribute of LbL deposition is control over the PEML physicochemical properties by variation of factors such as pH [15,16], the presence of salts [2,17] (as well as ionic strength [18]), and temperature [19] to tune layer thickness [20], degree of polyelectrolyte layer interpenetration [2], surface roughness (RMS) [21], film wettability [13], and the formation/size of pores [14].…”

“…Films with high dye loading [17] are somewhat immune to F-P artifacts because high absorption coefficients reduce the number of reflections taking part in the observed response [16,17], thus explaining their lack of attention in such LbL films. Additionally, the limited data sets found in the literature often do not exhibit these artifacts either because they did not extend film thicknesses past the maximum for the oscillation of the system [21,24] or they comprise a limited number of data points so oscillations were not apparent [21].…”