A Controlled-Release Strategy for the Generation of Cross-Linked Hydrogel Microstructures

Abstract

Microscale hydrogels of controlled sizes and shapes are useful for cell-based screening, in vitro diagnostics, tissue engineering, and drug delivery. However, the rapid cross-linking of many chemically and pH cross-linkable hydrogel materials prevents the application of existing micromolding techniques. In this work we present a method for fabricating micromolded calcium alginate and chitosan structures through controlled release of the gelling agent from a hydrogel mold. Replica molding was employed to generate patterned membranes, whereas microtransfer molding was used to produce microparticles of controlled shapes. To explore the viability of this technique for producing complex tissue engineering micro-architectures, this approach was used to generate cell-laden size- and shape-controlled 3D microgels as well as composite hydrogels with well-defined spatially segregated regions. In addition, shape-controlled microstructures that can exhibit differential release properties were loaded with macromolecules to verify the potential of this approach for drug delivery applications.

Formulation and Evaluation of in Situ Ocular Gel for Dry Eye Syndrome

“…[15] hydrogels show minimal tendency to adsorb proteins from body fluids because of their low interfacial tension. Further, the ability of molecules of different sizes to diffuse into (drug loading) and out of (drug release) hydrogels allow the possible use of dry or swollen polymeric networks as drug delivery [16] These are polymers endow with an ability to swell in water or aqueous solvents and induce a liquid-gel transition. [17] Currently, two groups of hydrogels are distinguished, namely performed and in situ forming gels.…”

“…[16] It is powerful bactericidal agent and is used clinically. Polymixin B is obtained from bacillus polymyxa.…”

Structured biopolymer-based delivery systems for encapsulation, protection, and release of lipophilic compounds

“…However, some closely-related systems have been investigated. For instance, alginate particles have been made by placing a calcium-releasing plate on one side of the mold (TaleiFranzesi, Ni, Ling, & Khademhosseini, 2006). Diffusion of the calcium ions out of the plate caused gelation of the alginate within the mold.…”

Directed assembly of cell-laden hydrogels for engineering functional tissues

“…These materials, which encompass a large class of hydrogels, were molded by using hydrogel micromolds that were capable of simultaneously controlling the shape of the hydrogel precursors and the delivery of crosslinking agents. 40 Printing technology can also be used to encapsulate cells in hydrogels. 41 In this process, standard or modified printers are used where paper and ink are replaced with substrate (usually polymer made) and cell-laden medium respectively.…”