Swellable Hydrogel-based Systems for Controlled Drug Delivery

Abstract

The controlled delivery of drugs can be effectively obtained using systems based on hydrogels. Tablets, to be orally administered, represent the simplest and the most traditional dosage systems based on hydrogel. Their formulation and preparation require to mix and to compress, in proper ratios, various excipients, including a swellable polymer and a drug. Carriers for controlled release systems are usually cross-linked polymers able to form hydrogels that show peculiar release mechanisms, where both diffusion and tablet swelling play important roles.When a dry swellable hydrogel-based matrix is immersed in a physiological fluid, this starts to penetrate inside the polymeric hydrophilic matrix. When a certain solvent concentration is reached, the polymeric chains unfold due to a glass-rubber transition, and a gel-like layer is formed. In the swollen region, the drug molecules can easily diffuse toward the outer dissolution medium, once they are dissolved. The polymer network became extremely hydrated where the swollen matrix is in contact with the outer medium, and processes like chain disentanglement take place, "eroding" the matrix.This chapter is focused on the analysis of the state of the art about the uses of carriers for controlled release systems composed by hydrogel-based matrices. This analysis has been performed studying in deep both the experimental and the modeling techniques which have been investigated over the years to characterize all the phenomena involved during the drug release.

Towards Developing Bioresponsive, Self-Assembled Peptide Materials: Dynamic Morphology and Fractal Nature of Nanostructured Matrices

“…Of the different systems, hydrogels that form nanofiber networks are promising in vivo carriers. Hydrogels offer dynamic and novel applications due to their unique properties, including: swelling with water, housing drugs and ligands, and being made into a multitude of mechanical and morphological configurations that provide multiple means of controlling release [4][5][6][7][8]. However, developing exact and tuneable release mechanisms and morphological features can be extremely complicated, needing additional chemical synthesis involving toxic co-solvents, chemical triggers, or full transplantation to provide a fully formed network in vivo [9].…”

Dissolution Kinetics of Partially Purified Bromelain From Pineapple Cores (Ananas Comosus [L.] Merr.) Encapsulated in Glutaraldehyde-Crosslinked Alginate-Guar Gum

“…Moreover, the maximum protein content is considerably smaller in the artificial gastric fluid (0.18 mg/L) than in the intestinal environment (1.97 mg/L). The protein release into the intestinal environment is affected by swelling of the hydrogel [23]. Its high swelling ability causes the trapped bromelain to easily diffuse out through the pores.…”

How Can One Controllably Use of Natural ΔpH in Polyelectrolyte Multilayers?

“…The water uptake depending on pH can be a key parameter to determine the swelling phenomenon and, as a consequence, the drug release from a matrix. [45] Release kinetics is faster at the beginning and tends to decrease with time, till all of the drug contained in the matrix reaches the dissolution medium. [45] Release kinetics is faster at the beginning and tends to decrease with time, till all of the drug contained in the matrix reaches the dissolution medium.…”

“…A typical drug release profile via diffusion from PEs is shown in Figure 5, red circles on the right axis. [45] Release kinetics is faster at the beginning and tends to decrease with time, till all of the drug contained in the matrix reaches the dissolution medium. Release kinetics for pH sensitive sys tems is strongly dependent from the pH: either capsule being in open or closed state.…”