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- Paidikondala, Maruthibabu, 1985-, et al.
(author)
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Impact of Hydrogel Cross-Linking Chemistry on the in Vitro and in VivoBioactivity of Recombinant Human Bone Morphogenetic Protein-2
- 2019
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In: ACS Applied Bio Materials. - : American Chemical Society (ACS). - 2576-6422.
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Journal article (peer-reviewed)abstract
- Designing strategies to deliver functional proteins at physiologically relevant concentrations using chemically cross-linked biocompatible hydrogels is a major field of research. However, the impact of cross-linking chemistry on the encapsulated protein bioactivity is rarely studied. Here we examine the two well-known cross-linking reactions namely; hydrazone cross-linking chemistry and thiol-Michael addition reaction to form hyaluronic acid (HA) hydrogels. As a therapeutic protein, we employed recombinant human bone morphogenetic protein-2 (rhBMP-2) for this study. Incubation of rhBMP-2 with HA functionalized with a thiol diminished phosphorylation of Smad 1/5/8, a signal transducer for osteogenic differntiation, whereas an aldehyde functionalized HA had no effect. This indicates that thiol functionalized polymers indeed has an impact on protein function. To validate this result in an in vivo setting we performed BMP-2 induced bone formation in a rat ectopic model. These experiments revealed that the hydrazone-cross-linked HA-hydrogel induced significantly higher bone formation (18.90 ± 4.25 mm3) as compared to the HA-thiol-Michael hydrogels (1.25 ± 0.52 mm3) after 8 weeks as determined by micro-computed tomography. The histological examination of the neo-bone indicated that hydrazone-hydrogels promoted a better quality of bone formation with improved mineralization and collagen formation as compared to the thiol-Michael hydrogels. We believe such a direct comparison of two cross-linking chemistries will provide new insight for developing biomaterials for protein delivery for in vivo applications.
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| 2. |
- Wang, Shujiang, et al.
(author)
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Influence of ions to modulate hydrazone and oxime reaction kinetics to obtain dynamically cross-linked hyaluronic acid hydrogels
- 2019
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In: Polymer Chemistry. - : ROYAL SOC CHEMISTRY. - 1759-9954 .- 1759-9962. ; 10:31, s. 4322-4327
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Journal article (peer-reviewed)abstract
- Dynamic covalent chemistry forming hydrazone and oxime linkages is attractive due to its simplicity, selectivity and compatibility under aqueous conditions. However, the low reaction rate at physiological pH hampers its use in biomedical applications. Herein, we present different monovalent and bivalent aqueous salt solutions as bio-friendly, non-toxic catalysts which can drive the hydrazone and oxime reactions with excellent efficacy at physiological pH. Direct comparison of hydrazone and oxime reactions using a small molecule model, without any salt catalysis, indicated that oxime formation is 6-times faster than hydrazone formation. Addition of different salts (NaCl, NaBr, KCl, LiCl, LiClO4, Na2SO4, MgCl2 and CaCl2) accelerated the pseudo-first-order reaction kinetics by similar to 1.2-4.9-fold for acylhydrazone formation and by similar to 1.5-6.9-fold for oxime formation, in a concentration-dependent manner. We further explored the potential of such catalysts to develop acylhydrazone and oxime cross-linked hyaluronic acid (HA) hydrogels with different physicochemical properties without changing the degree of chemical modification. Analogous to the small molecule model system, the addition of monovalent and divalent salts as catalysts significantly reduced the gelling time. The gelling time for the acylhydrazone cross-linked HA-hydrogel (1.6 wt%) could be reduced from 300 min to 1.2 min by adding 100 mM CaCl2, while that for the oxime cross-linked HA-hydrogel (1.2 wt%) could be reduced from 68 min to 1.1 min by adding 50 mM CaCl2. This difference in the gelling time also resulted in hydrogels with differential swelling properties as measured after 24 h. Our results are the first to demonstrate the use of salts, for catalyzing hydrogel formation under physiologically relevant conditions.
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