Alginate‐gelatin blend with embedded voids for controlled release applications

Abstract

Alginate gel is known for its potential use in the controlled release of drugs, and as a 3-D structure for tissue harvesting. In this paper, the tuning of the performance of alginate gel by blending gelatin in the aqueous phase, and introducing bubbles in a regular alignment are discussed. Monodisperse bubbles in millimetre or submillimeter size were introduced into the aqueous suspension of the blend prior to gelation, using a novel fluidic arrangement. The CaCl 2 solution, added as the crosslinker diffused into the lamella, forming a rigid structure of calcium alginate. The effective blending of gelatin in alginate provided benefits of both the biopolymers in the final product. The benefits are the excellent absorption capacity of alginate and the mechanical strength of gelatin in the blend. The selfaligned voids enabled further tuning of absorption capacity and/or rate of release. Also, the presence of voids enhanced the elastomeric quality of the composite structure. The uptake of Vitamin B 12 solution was measured gravimetrically, and the release in PBS buffer on a shaker was studied using UV-vis spectrophotometer. For different loadings of void and gelatin, the absorption capacity, mechanical strength and the compression behavior were analysed.

Alginate–chitosan composite hydrogel film with macrovoids in the inner layer for biomedical applications

“…The stress response was nonlinear due to the expulsion of aqueous fluid from the pore space of the hydrogel composite. Our experience suggests that upon release of the stress, the structure imbibes the previously expelled fluid, and swells to the original shape, as long as the deformation is small . Further, this was noticed that for the same level of deformation, the stress was much higher in case of the film with no voids.…”

“…The ultimate stress at which the adhesion broke is 12.9 kPa. This value is on similar order as the tensile strength of wet alginate film, and as such, cohesive failure in alginate layer prior to break in adhesion at the interface cannot be totally ruled out for such soft structure. For the composite film in this study, the detachment of the two layers at the interface was confirmed from visual observations.…”

“…As an alternative to these methods, bubbles can be introduced directly using a fluidic arrangement for a better control of void size, and for uniform distribution of voids over space . The addition of voids in gel film resulted in reduction of strength, which can be compensated by making a layered composite of two biopolymers.…”

Mechanical behaviour of alginate film with embedded voids under compression-decompression cycles

“…The gas phase was injected using a mass flow controller (Alicat Scientific, U.S.A). The liquid and the gas flow rates were precisely maintained at 8 mL/min and 1 mL/min respectively 18,29,33 . The stretching and squeezing of the gas string at the tip of the fluidic device resulted in breaking of gas string into small and uniform bubbles.…”

“…The performance of a hydrogel can be improved by inserting voids in the gel matrix at the time of fabrication 18,19 . There are different methods to embed voids within polymer matrix, such as emulsion freeze drying, solvent casting or particulate leaching, fibre bonding, thermal phase separation, electrospinning, gas foaming, and through use of supercritical CO 2 20 .…”