Collagen organization deposited by fibroblasts encapsulated in pH responsive methacrylated alginate hydrogels

Abstract

The pH of dermal wounds shifts from neutral during the inflammatory phase to slightly basic in the tissue remodeling phase. Stage specific wound treatment can be developed using environmentally responsive alginate hydrogels. The chemistry of these networks dictates swelling behavior. Here, we fabricated alginate hydrogels using chain growth, step growth, and combined mixed mode gelation methods to crosslink methacrylated alginate (ALGMA) and gain control over swelling responses. Methacrylation of the alginate network was confirmed through NMR spectroscopy. Strontium cations were introduced to fabricate stiffer, dually crosslinked hydrogels. Dual crosslinking significantly decreased the swelling response over the pH range of 3-9 for step growth and chain growth hydrogels, with no impact on mixed mode hydrogels. The extent of crosslinking altered the hydrogel degradation profiles under accelerated degradation conditions. Encapsulated NIH/3T3 fibroblasts in the different ALGMA hydrogels remained viable with greater cell proliferation in the stiffer gels. Collagen organization deposited by the NIH/3T3 fibroblasts was monitored using second harmonic generation (SHG) microscopy and was influenced by the crosslinking mechanism. Ionic chain growth and ionic mixed mode crosslinked ALGMA hydrogels caused relatively isotropic collagen organization, particularly 10 days post-cell encapsulation. Principal component analysis (PCA) was employed to uncover correlations between the observed properties. The ability of these environmentally responsive gels to induce isotropic collagen and respond to pH changes means they hold promise as phase specific wound dressings. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 2934-2943, 2018.

Thiol-ene cross-linked alginate hydrogel encapsulation modulates the extracellular matrix of kidney organoids by reducing abnormal type 1a1 collagen deposition

“…Besides hydrogel stiffness, the relative relaxation time has been observed to affect type 1 collagen deposition. For example, the encapsulation of chondrocytes in hydrazone covalently adapatible network PEG hydrogels resulted in lower levels of type 1 collagen in hydrogels with faster relaxation times, with no effect on type 2 collagen [43,46]. Interestingly, tuning the hydrogel's mechanical properties (specifically stiffness or relaxation time) did not affect the expression and modulation of type 2 [46] or type 3 collagen [43] in these studies, which is similar to our observations for type 6 collagen.…”

“…For example, the encapsulation of chondrocytes in hydrazone covalently adapatible network PEG hydrogels resulted in lower levels of type 1 collagen in hydrogels with faster relaxation times, with no effect on type 2 collagen [43,46]. Interestingly, tuning the hydrogel's mechanical properties (specifically stiffness or relaxation time) did not affect the expression and modulation of type 2 [46] or type 3 collagen [43] in these studies, which is similar to our observations for type 6 collagen. Finally, the reduction of type 1 collagen could also be caused by increased collagen degradation activity by matrix metalloproteinases, as has been reported for a cartilage-specific degradable poly(ethylene) glycol hydrogel used for encapsulating chondrocytes [47].…”

Engineering Tough, Injectable, Naturally Derived, Bioadhesive Composite Hydrogels

“…The degree of crosslinking is calculated by integrating the double bond proton peaks (vinyl) considering methyl peaks. [ 47,48 ] Same procedure is followed to calculate the percentage of crosslinking for the hybrid hydrogel, which was found to be ≈65%.…”

“…To quantify the degree of methacrylation, GelMA and AlgMA were separately dissolved in D 2 O at a concentration of 10 mg mL −1 , and the degree of substitution was estimated based on literature. [ 47,48 ] To assess the crosslinking degree of bioadhesives, the hybrid hydrogels containing GelMA (20% w/v) and 3% w/v AlgMA were photocrosslinked according to the previous section. The samples were then immersed in DMSO for 7 days at 37 °C and sonicated for 1 h every day to partially dissolve the hydrogels prior to conducting the NMR spectroscopy.…”

Dual Crosslinked Methacrylated Alginate Hydrogel Micron Fibers and Tissue Constructs for Cell Biology

“…Meanwhile, some chemical photoinitiators (e.g., VA-086, VA-044, V-50, and Irgacure 1870) are cytotoxic to cells or bioactive molecules that are embedded in alginate hydrogels [35]. In order to reduce the amount of photoinitiator and its damage to cells or bioactive molecules without affecting the degree of crosslink, the active groups with photoinitiation, such as methacrylate (MA) are introduced into macromolecular chains [38,39]. For the hydrogels prepared by the photo-crosslinking process, most of their structures are mostly capsules, scaffolds, and thin films, meanwhile the photo-crosslinked hydrogels with fibrous structure are relatively less [6,33,34,35].…”