Fabrication of Glucose-Sensitive Layer-by-Layer Films for Potential Controlled Insulin Release Applications

Self-regulated drug delivery systems (DDS) are potential alternative to the conventional method of introducing insulin to the body due to their controlled drug release mechanism. In this study, Layer-by-Layer technique was utlized to manufacture drug loaded, pH responsive thin films. Insulin was alternated with pH-sensitive, [2-(dimethyl amino) ethyl aminoacrylate] (PDMAEMA) and topped of with polymer/glucose oxidase (GOD) layers. Similarly, films using a different polymer, namely Poly(Acrylic Acid) (PAA) were also fabricated. Exposure of the films to glucose solutions resulted to the production of gluconic acid causing a polymer conformation change due to protonation, thus releasing the embedded insulin. The insulin release was monitored by subjecting the dipping glucose solutions to Bradford Assay. Films exhibited a reversal in drug release profile in the presence of glucose as compared to without glucose. PAA films were also found out to release more insulin compared to that of the PDMAEMA films.The difference in the profile of the two films were due to different polymer-GOD interactions, since both films exhibited almost identical profiles when embedded with Poly(sodium 4-styrenesulfonate) (PSS) instead of GOD

Fabrication of Glucose-Sensitive Layer-by-Layer Films for Potential Controlled Insulin Release Applications

Self-regulated drug delivery systems (DDS) are potential alternative to the conventional method of introducing insulin to the body due to their controlled drug release mechanism. In this study, Layer-by-Layer technique was utlized to manufacture drug loaded, pH responsive thin films. Insulin was alternated with pH-sensitive, [2-(dimethyl amino) ethyl aminoacrylate] (PDMAEMA) and topped of with polymer/glucose oxidase (GOD) layers. Similarly, films using a different polymer, namely Poly(Acrylic Acid) (PAA) were also fabricated. Exposure of the films to glucose solutions resulted to the production of gluconic acid causing a polymer conformation change due to protonation, thus releasing the embedded insulin. The insulin release was monitored by subjecting the dipping glucose solutions to Bradford Assay. Films exhibited a reversal in drug release profile in the presence of glucose as compared to without glucose. PAA films were also found out to release more insulin compared to that of the PDMAEMA films.The difference in the profile of the two films were due to different polymer-GOD interactions, since both films exhibited almost identical profiles when embedded with Poly(sodium 4-styrenesulfonate) (PSS) instead of GOD

UV–Irradiation Induced Synthesis of Fluorescent Poly (Acrylic Acid) Stabilized Silver Clusters

Photochemical treatment using ultraviolet radiation was used to prepare fluorescent silver nanoparticles/nanoclusters from AgNO3 precursor upon its encapsulation with Poly (Acrylic Acid). Spectrofluorometric analysis showed an excitation spectra with maxima at approximately 450 nm and 550 regions nm when fixed wavelength of 600 nm was used to scan the solutions. Fluorescent emission occurred at around 500 nm and 700 nm using the 450 nm excitation wavelength. High molecular weight polymer (AgPAA1250) showed higher intensity of emission than low molecular weight (AgPAA450). Stability of the nanoparticle solution was assessed using Zeta Potential Measurements. Despite having a larger average particle diameter, Zeta Potential value for AgPAA 1250 is more negative than AgPAA 450, -59.3 mV and -47.5 mV respectively. This tells us that using a polymer with larger molecular weight can better prevent the aggregation of the nanoparticles

UV–Irradiation Induced Synthesis of Fluorescent Poly (Acrylic Acid) Stabilized Silver Clusters

Photochemical treatment using ultraviolet radiation was used to prepare fluorescent silver nanoparticles/nanoclusters from AgNO3 precursor upon its encapsulation with Poly (Acrylic Acid). Spectrofluorometric analysis showed an excitation spectra with maxima at approximately 450 nm and 550 regions nm when fixed wavelength of 600 nm was used to scan the solutions. Fluorescent emission occurred at around 500 nm and 700 nm using the 450 nm excitation wavelength. High molecular weight polymer (AgPAA1250) showed higher intensity of emission than low molecular weight (AgPAA450). Stability of the nanoparticle solution was assessed using Zeta Potential Measurements. Despite having a larger average particle diameter, Zeta Potential value for AgPAA 1250 is more negative than AgPAA 450, -59.3 mV and -47.5 mV respectively. This tells us that using a polymer with larger molecular weight can better prevent the aggregation of the nanoparticles

One-pot photochemical synthesis of solution-stable TiO2-polypyrrole nanocomposite for the photodegradation of methyl orange

Photocatalysis is a promising technology used in wastewater treatment. However, the practical application of this approach has been hindered by several factors. One issue is the aggregation of the photocatalyst in solution which leads to significant decrease in catalytic efficiency. Recent innovations in photochemical research have geared towards improving the colloidal stability of well-known photocatalysts such as titanium dioxide (TiO2). In this study, a simple method of imparting colloidal stability to TiO2, through one-pot photo-polymerized polypyrrole (PPy) nanoparticle coatings were demonstrated. The resulting TiO2-PPy (TP) dispersions exhibited excellent resistance to aggregation as evident in their uniform particle size distribution (diameter = 81.40 ± 6.58 nm, polydispersity index = 0.412 ± 0.037) and stable zeta-potential values (ζ = 33.15 ± 4.35). The optimum TiO2 to polymer ratio also resulted to significant lowering in band-gap energy (from 3.54 eV to 3.15 eV) which is an indicator of improved photocatalytic properties. Photodegradation of a model pollutant, methyl orange (MO) performed at optimal lightning condition and 4TP dosage showed 35% /hour photocatalytic efficiency. Lastly, kinetic studies suggest that the catalytic performance is dependent on the pollutant concentration as shown by a second-order MO degradation with rate constant of 306.856 x 10-7 M-1 s-1 and proposed rate law of R = k [MO]2. The study had also indicated the chemical conversion of MO to CO2by measuring about 43% decrease in total organic carbon in an hour

Ruthenium(II)—tris-bipyridine/titanium dioxide codoped zeolite Y photocatalysts: II. Photocatalyzed degradation of the model pollutant 2,4-xylidine, evidence for percolation behavior

A considerably arduous test of a novel class of composite materials consisting of [Ru(bpy)3]2+ and TiO2 codoped zeolites Y is presented here. The [Ru(bpy)3]2+ and TiO2 codoped zeolites Y served as photocatalysts in the oxidation of the model compounds 2,4-dimethylaniline (2,4-xylidine) by H2O2 in an acidic aqueous medium. Zeolite-embedded TiO2(nano)particles play an important role in the degradation mechanism. The first step in this complex mechanism is the photoelectron transfer from photoexcited [Ru(bpy)3]2+*, located inside the supercage of zeolite Y, to a neighboring TiO2 nanoparticle. During this electron transfer process, electron injection into the conduction band of TiO2 is achieved. The second decisive step is the reaction of this electron with H2O2, which was previously chemisorbed at the surface-region of the TiO2 nanoparticles. In this reaction, a TiO2 bound hydroxyl radical (TiO2—HO ) is created. This highly reactive intermediate initiates then the oxidation of 2,4-xylidine, which enters the zeolites framework in its protonated form (Hxyl+). The formation of 2,4-dimethylphenol as first detectable reaction product indicated that this oxidation proceeds via an electron transfer mechanism. Furthermore, [Ru(bpy)3]3+, which was created in the initiating photoelectron transfer reaction between [Ru(bpy)3]2+* and TiO2, also takes place in the oxidation of Hxyl+. [Ru(bpy)3]2+ is recycled in that reaction, which also belongs to the group of electron transfer reactions. In addition to the primary steps of this particular Advanced Oxidation Process (AOP), the dependence of the efficiency of the 2,4-xylidine degradation as a function of the [Ru(bpy)3]2+ and TiO2 loadings of the zeolite Y framework is also reported here. The quenching of [Ru(bpy)3]2+* by H2O2 as well as the photocatalytic activity of the [Ru(bpy)3]2+ and TiO2 codoped zeolite Y catalysts both follow a distinct percolation behavior in dependence of their TiO2 content