Structural and permeability characterization of biosynthetic PVA hydrogels designed for cell-based therapy

Abstract

Incorporation of extracellular matrix (ECM) components to synthetic hydrogels has been shown to be the key for successful cell encapsulation devices, by providing a biofunctional microenvironment for the encapsulated cells. However, the influence of adding ECM components into synthetic hydrogels on the permeability as well as the physical and mechanical properties of the hydrogel has had little attention. Therefore, the aim of this study was to investigate the effect of incorporated ECM analogues on the permeability performance of permselective synthetic poly(vinyl alcohol) (PVA) hydrogels in addition to examining the physico-mechanical characteristics. PVA was functionalized with a systematically increased number of methacrylate functional groups per chain (FG/c) to tailor the permselectivity of UV photopolymerized hydrogel network. Heparin and gelatin were successfully incorporated into PVA network at low percentage (1%), and co-hydrogels were characterized for network properties and permeability to bovine serum albumin (BSA) and immunoglobulin G (IgG) proteins. Incorporation of these ECM analogues did not interfere with the base PVA network characteristics, as the controlled hydrogel mesh sizes, swelling and compressive modulii remained unchanged. While the permeation profiles of both BSA and IgG were not affected by the addition of heparin and gelatin as compared with pure PVA, increasing the FG/c from 7 to 20 significantly limited the diffusion of the larger IgG. Consequently, biosynthetic hydrogels composed of PVA with high FG/c and low percent ECM analogues show promise in their ability to be permselective for various biomedical applications.

Visible Light Cross‐Linking of Gelatin Hydrogels Offers an Enhanced Cell Microenvironment with Improved Light Penetration Depth

“…Among these, photo‐polymerizable gelatin hydrogels are especially attractive as they offer the ability for spatial and temporal control over the polymerization process. Additionally, the reaction can be performed at room or physiological temperature, with fast curing rates and minimal heat generation …”

New Visible-Light Photoinitiating System for Improved Print Fidelity in Gelatin-Based Bioinks

“…However, these techniques require specialized biomaterials (bioinks), which generally have specific rheological properties that allow printing of constructs with high shape fidelity, as well as being cyto-compatible to support cell survival, function, and phenotype. Hydrogels, which are composed of highly hydrated polymeric networks, have shown great promise as bioinks due to their structural similarity to the native extracellular matrix. − …”

Bioactivity of permselective PVA hydrogels with mixed ECM analogues

“…In our preceding study, the controlled physico‐mechanical characteristics of the base PVA network was shown to be preserved after incorporation of a 1% of separate ECM molecules. More importantly, the heparin and gelatin did not interfere with the expected permeability of different FG/c PVA hydrogels, which is an essential feature determining the permselectivity capacity of these hydrogels for various biomedical applications including cell immunoisolation.…”

“…Solutions were then lyophilized to obtain dry macromers. A schematic representation of methacrylation reactions for PVA, heparin, and gelatin has been previously illustrated elsewhere …”

“…The amount of incorporated heparin and gelatin remaining in the hydrogel network was calculated by determining the percent unbound heparin and gelatin released from the hydrogels after immersion in PBS (pH 7.4) at 37°C for 1, 3, and 7 days, according to methods described previously . Briefly, hydrogel discs (7 mm diameter × 1 mm thick) were immersed in 1 mL PBS.…”