Hakan Kaygusuz

Natural alginate biopolymer montmorillonite clay composites for vitamin B2 delivery

This work describes the in vitro release of a small drug, riboflavin, from novel calcium and barium crosslinked alginate–montmorillonite composite beads via oral route. Effect of crosslinking cation, concentration of montmorillonite and media on encapsulation efficiencies, and release profiles of riboflavin were studied. Beads were characterized using gravimetric swelling ability study, Fourier transform infrared spectroscopy, and scanning electron microscopy. Results indicate that addition of montmorillonite increases the encapsulation efficiencies and slows down the release rates significantly.

Surfactant and metal ion effects on the mechanical properties of alginate hydrogels

This paper addresses the controlled variation of the mechanical properties of alginate gel beads by changing the alginate concentration or by adding different surfactants or cross-linking cations. Alginate beads containing nonionic Brij 35 or anionic sodium dodecyl sulfate (SDS) surfactants were prepared with two different types of cations (Ca2+, Ba2+) as crosslinkers. Compression measurements were performed to investigate the effect of the surfactant and cation types and their concentrations on the Youngs modulus of alginate beads. The Youngs modulus was determined by using Hertz theory. For all types of alginate gel beads the Youngs modulus showed an increasing value for increasing alginate contents. Addition of the anionic surfactant SDS increases the Youngs modulus of the alginate beads while the addition of non-ionic surfactant Brij 35 leads to a decrease in Youngs modulus. This opposite behavior is related to the contrary effect of both surfactants on the charge of the alginate beads. When Ba2+ ions were used as crosslinker cation, the Youngs modulus of the beads with the surfactant SDS was found to be approximately two times higher than the modulus of beads with the surfactant Brij 35. An ion specific effect was found for the crosslinking ability of divalent cations.

Effect of Calcium Ion Concentration on Small Molecule Desorption from Alginate Beads

Spherical alginate beads were prepared by ionotropic gelation of sodium alginate through the use of calcium ions. Pyranine (Py) was added to the alginate solution as a small molecule probe for fluorescence studies. Desorption of Py in water from the alginate beads cross-linked with calcium ions was studied by using the steady state fluorescence technique. The fluorescence emission intensity (I) from Py was monitored during the desorption process at 512 nm using the time drive mode of the spectrofluorometer. The increase in I was attributed to Py release from the beads. The Fickian diffusion model was used to calculate the desorption coefficients, D, which were found to be increased up to 3% (w/v) CaCl2 concentration in the beads, and then decreased with a further increase of CaCl2 content. On the other hand, the encapsulation efficiency of Py in the calcium alginate beads presented the reverse behavior compared to D. It was observed that, when the content of CaCl2 was increased, the incubation time, t0, for the start of desorption increased.

Antimicrobial cerium ion-chitosan crosslinked alginate biopolymer films: A novel and potential wound dressing

Wound dressings require good antiseptic properties, mechanical strength and, more trustably, natural material ingredients. Antimicrobial properties of cerium ions and chitosan are known and alginate based wound dressings are commercially available. In this study, the advantages of these materials were combined and alginate films were crosslinked with cerium(III) solution and chitosan added cerium(III) solution. Films were characterized by Fourier transform infrared spectroscopy (FTIR), light transmittance, scanning electron microscopy (SEM), swelling experiments, water vapor transmittance tests, and mechanical stretching tests. The antibacterial and physical properties of the films were compared with those of conventional calcium alginate films. Both cerium ion crosslinked and cerium ion-chitosan crosslinked alginate films gained antibacterial activity against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria. Cerium alginate-chitosan films showed high resistance to being deformed elastically. Results show that cerium alginate-chitosan films can be flexible, ultraviolet-protecting, and antibacterial wound dressings.

Adsorptive removal kinetics of anionic dye onto chitosan films doped with graphene oxide: An in situ fluorescence monitoring

ABSTRACT The aqueous adsorption of a fluorescent dye (pyranine) onto crosslinked chitosan-graphene oxide composite films was studied. In situ fluorescence monitoring technique is introduced as easy and fast experimental technique to select optimal adsorbent conditions. The effect of ionic crosslinker on adsorption was studied with sodium tripolyphosphate, trisodium citrate, and sodium sulfate, respectively. Among the crosslinkers, it was realized that sodium sulfate crosslinked films showed a greater adsorption rate for pyranine than the other two types of crosslinked films. Recently, graphene oxide is of interest as a filler compound for many biopolymer applications due to its favorable thermal, mechanical and surficial properties. In the present study, graphene oxide incorporation increased adsorption rate of the dye and the mechanical strength of ionically crosslinked chitosan films. The adsorption behavior of the adsorbent was explained by a kinetic model. Samples were characterized using scanning electron microscopy, thermogravimetric analysis, swelling experiments and tensile testing method.

Gelation of PAAm-PVP composites: A fluorescence study

Hybrid hydrogels are a new class of composite materials. Polyacrylamide (PAAm) hydrogels are mainly produced by free radical crosslinking copolymerization (FCC) of AAm in the presence of N, N′-methylene bis (acrylamide) (BIS) as the crosslinker. Pyranine doped PAAm-poly (N-vinyl pyrrolidone) (PVP) composite were prepared with different amounts of PVP varying in the range between 0.0015 and 0.1 gr. It was observed that pyranine molecules as a fluoroprobe bind to AAm and PVP chains upon the initiation of the polymerization, causing the fluorescence spectra of the bonded pyranines shift to the shorter wavelengths. The sol–gel phase transition and its universality were monitored and tested as a function of PVP contents. Observations around the critical point show that the gel fraction exponent, β, agreed with the percolation result for below 0.025 gr PVP contents. However, classical result was observed above 0.0125 gr PVP content.