| 1. |
- Oommen, Oommen P., et al.
(author)
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Smart Design of Stable Extracellular Matrix Mimetic Hydrogel : Synthesis, Characterization, and In Vitro and In Vivo Evaluation for Tissue Engineering
- 2013
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In: Advanced Functional Materials. - : Wiley. - 1616-301X .- 1616-3028. ; 23:10, s. 1273-1280
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Journal article (peer-reviewed)abstract
- The simplicity and versatility of hydrazone crosslinking has made it a strategy of choice for the conjugation of bioactive molecules. However, the labile nature of hydrazone linkages and reversibility of this coupling reaction restricts its full potential. Based on the fundamental understanding of hydrazone stability, this problem is circumvented by resonance-stabilization of a developing N2 positive charge in a hydrazone bond. A novel chemistry is presented to develop a resilient hydrazone bond that is stable and non- reversible under physiological conditions. A carbodihydrazide (CDH) type hydrazide derivative of the biomolecule forms intrinsically stabilized hydrazone-linkages that are nearly 15-fold more stable at pH 5 than conventional hydrazone. This chemoselective coupling reaction is catalyst-free, instantaneous, and virtually non-cleavable under physiological conditions, therefore can serve as a catalyst-free alternative to click chemistry. This novel crosslinking reaction is used to tailor a hyaluronan hydrogel, which delivered exceptional hydrolytic stability, mechanical properties, low swelling, and controlled enzymatic degradation. These desired characteristics are achieved without increasing the chemical crosslinking. The in vivo evaluation of this hydrogel revealed neo-bone with highly ordered collagen matrix mimicking natural bone regeneration. The proximity ligation assay or PLA is used to detect blood vessels, which highlighted the quality of engineered tissue.
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| 2. |
- 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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| 3. |
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| 4. |
- Podiyan, Oommen, 1977-, et al.
(author)
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Smart design of stable hydrazone crosslinked extracellular matrix mimetic hydrogel for tissue engineering application
- 2012
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In: Journal of Tissue Engineering and Regenerative Medicine. - : Hindawi Limited. - 1932-6254. ; 6:suppl 1, s. 192-192
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Journal article (other academic/artistic)abstract
- Injectable hydrogels are important biomaterials with enormous applications. They are used for various biomedical applications such as diagnostics, 3D cell culture matrix, drug reservoir, encapsulation of bioactive compounds and growth factors, scaffold for tissue engineering etc. We here present our recent development in our efforts to develop hydrogel scaffolds with enhanced rigidity, stability, swelling characteristics. Hydrazone crosslinked gels are attractive due to its simplicity and versatility which could be formed by mixing appropriate aldehyde and hydrazide functionalized hyaluronan. By fine-tuning the electronic character around the hydrazone linkage, we succeeded in developing extremely stable hydrazone bond and utilized it for developing hyaluronan (HA) based synthetic extracellular matrix (ECM) hydrogel. Among the different hydrazides tested, we identified carbonyldihydrazide (CDH) as the best candidate to deliver stable hydrazone linkage. This stability is presumably due to extensive delocalization of the positive charge across neighboring amino groups of CDH. The hydrolytic stability imparted by this group was found to be several folds under acidic, basic and physiological pH when compared to other hydrazones. This tailored hydrogel with CDH also exhibited superior swelling and mechanical properties and enzymatic stability which makes it ideal for tissue engineering application.
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| 5. |
- Ravichandran, Ranjithkumar, et al.
(author)
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Functionalised type-I collagen as a hydrogel building block for bio-orthogonal tissue engineering applications
- 2016
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In: Journal of materials chemistry. B. - : ROYAL SOC CHEMISTRY. - 2050-750X .- 2050-7518. ; 4:2, s. 318-326
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Journal article (peer-reviewed)abstract
- In this study, we derivatized type I collagen without altering its triple helical conformation to allow for facile hydrogel formation via the Michael addition of thiols to methacrylates without the addition of other crosslinking agents. This method provides the flexibility needed for the fabrication of injectable hydrogels or pre-fabricated implantable scaffolds, using the same components by tuning the modulus from Pa to kPa. Enzymatic degradability of the hydrogels can also be easily fine-tuned by variation of the ratio and the type of the crosslinking component. The structural morphology reveals a lamellar structure mimicking native collagen fibrils. The versatility of this material is demonstrated by its use as a pre-fabricated substrate for culturing human corneal epithelial cells and as an injectable hydrogel for 3-D encapsulation of cardiac progenitor cells.
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| 6. |
- Wang, Shujiang, et al.
(author)
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Dynamic covalent crosslinked hyaluronic acid hydrogels and nanomaterials for biomedical applications
- 2022
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In: Biomaterials Science. - : Royal Society of Chemistry (RSC). - 2047-4830 .- 2047-4849. ; 10:22, s. 6399-6412
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Research review (peer-reviewed)abstract
- Hyaluronic acid (HA), one of the main components of the extracellular matrix (ECM), is extensively used in the design of hydrogels and nanoparticles for different biomedical applications due to its critical role in vivo, degradability by endogenous enzymes, and absence of immunogenicity. HA-based hydrogels and nanoparticles have been developed by utilizing different crosslinking chemistries. The development of such crosslinking chemistries indicates that even subtle differences in the structure of reactive groups or the procedure of crosslinking may have a profound impact on the intended mechanical, physical and biological outcomes. There are widespread examples of modified HA polymers that can form either covalently or physically crosslinked biomaterials. More recently, studies have been focused on dynamic covalent crosslinked HA-based biomaterials since these types of crosslinking allow the preparation of dynamic structures with the ability to form in situ, be injectable, and have self-healing properties. In this review, HA-based hydrogels and nanomaterials that are crosslinked by dynamic-covalent coupling (DCC) chemistry have been critically assessed.
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| 7. |
- 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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| 8. |
- Wang, Shujiang, 1985-
(author)
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Insights into dynamic covalent chemistry for bioconjugation applications
- 2017
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Doctoral thesis (other academic/artistic)abstract
- Dynamic covalent chemistry (DCC) is currently exploited in several areas of biomedical applications such as in drug discovery, sensing, molecular separation, catalysis etc. Hydrazone and oxime chemistry have several advantages, such as mild reaction conditions, selectivity, efficiency, and biocompatibility and therefore, have the potential to be for bioconjugation applications. However, these reactions suffer from major drawbacks of slow reaction rate and poor bond stability under physiological conditions. In this regard, the work presented in this thesis focuses on designing novel bioconjugation reactions amenable under physiological conditions with tunable reaction kinetics and conjugation stability.The first part of the thesis presents different strategies of dynamic covalent reactions utilized for biomedical applications. In the next part, a detailed study related to the mechanism and catalysis of oxime chemistry was investigated in the presence of various catalysts. Aniline, carboxylate and saline were selective as target catalysts and their reaction kinetics were compared under physiological conditions (Paper I and II). Then we attempted to explore the potential of those chemistries in fabricating 3D hydrogel scaffolds for regenerative medicine application. A novel mild and regioselective method was devised to introduce an aldehyde moiety onto glycosaminoglycans structure. This involved the introduction of amino glycerol to glycosaminoglycans, followed by regioselective oxidation of tailed flexible diol without affecting the C2-C3 diol groups on the disaccharide repeating unit. The oxidation rate of the tailed flexible diol was 4-times faster than that of C2-C3 diol groups of native glycosaminoglycan. This strategy preserves the structural integrity of the glycosaminoglycans and provides a functional aldehyde moiety (Paper III). Further, different types of hydrazones were designed and their hydrolytic stability under acidic condition was carefully evaluated. The hydrazone linkage with the highest hydrolytic stability was utilized in the preparation of extracellular matrix hydrogel for delivery of bone morphogenetic proteins 2 in bone regeneration (Paper IV) and studied for controlled release of the growth factor (Paper III).In summary, this thesis presents a selection of strategies for designing bioconjugation chemistries that possess tunable stability and reaction kinetics under physiological conditions. These chemistries are powerful tools for conjugation of biomolecules for the biomedical applications.
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| 9. |
- Wang, Shujiang, et al.
(author)
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Insights into the Mechanism and Catalysis of Oxime Coupling Chemistry at Physiological pH
- 2015
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In: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 21:15, s. 5980-5985
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Journal article (peer-reviewed)abstract
- The dynamic covalent-coupling reaction involving alpha-effect nucleophiles has revolutionized bioconjugation approaches, due to its ease and high efficiency. Key to its success is the discovery of aniline as a nucleophilic catalyst, which made this reaction feasible under physiological conditions. Aniline however, is not so effective for keto substrates. Here, we investigate the mechanism of aniline activation in the oxime reaction with aldehyde and keto substrates. We also present carboxylates as activating agents that can promote the oxime reaction with both aldehyde and keto substrates at physiological pH. This rate enhancement circumvents the influence of alpha-effect by forming H-bonds with the rate-limiting intermediate, which drives the reaction to completion. The combination of aniline and carboxylates had a synergistic effect, resulting in a similar to 14-31-fold increase in reaction rate at pD 7.4 with keto substrates. The biocompatibility and efficiency of carboxylate as an activating agent is demonstrated by performing cell-surface oxime labeling at physiological pH using acetate, which showed promising results that were comparable with aniline.
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| 10. |
- Wang, Shujiang, et al.
(author)
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Mild and Efficient Strategy for Site-Selective Aldehyde Modification of Glycosaminoglycans : Tailoring Hydrogels with Tunable Release of Growth Factor
- 2013
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In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 14:7, s. 2427-2432
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Journal article (peer-reviewed)abstract
- Aldehydes have been used as an important bioorthogonal chemical reporter for conjugation of large polymers and bioactive substances. However, generating aldehyde functionality on carbohydrate-based biopolymers without changing its native chemical structure has always persisted as a challenging task. The common methods employed to achieve this require harsh reaction conditions, which often compromise the structural integrity and biological function of these sensitive molecules. Here we report a mild and simple method to graft aldehydes groups on glycosaminoglycans (GAGs) in a site-selective manner without compromising the structural integrity of the biopolymer. This regio-selective modification was achieved by conjugating the amino-glycerol moiety on the carboxylate residue of the polymer, which allowed selective cleavage of pendent diol groups without interfering with the C2C3 diol groups of the native glucopyranose residue. Kinetic evaluation of this reaction demonstrated significant differences in second-order reaction rate for periodate oxidation (by four-orders of magnitude) between the two types of vicinal diols. We employed this chemistry to develop aldehyde modifications of sulfated and nonsulfated GAGs such as hyaluronic acid (HA), heparin (HP), and chondroitin sulfate (CS). We further utilized these aldehyde grafted GAGs to tailor extracellular matrix mimetic injectable hydrogels and evaluated its rheological properties. The composition of the hydrogels was also found to modulate release of therapeutic protein such as FGF-2, demonstrating controlled release (60%) for over 14 days. In short, our result clearly demonstrates a versatile strategy to graft aldehyde groups on sensitive biopolymers under mild conditions that could be applied for various bioconjugation and biomedical applications such as drug delivery and regenerative medicine.
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| 11. |
- Wang, Shujiang, et al.
(author)
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Saline Accelerates Oxime Reaction with Aldehyde and Keto Substrates at Physiological pH
- 2018
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In: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 8
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Journal article (peer-reviewed)abstract
- We have discovered a simple and versatile reaction condition for oxime mediated bioconjugation reaction that could be adapted for both aldehyde and keto substrates. We found that saline accelerated the oxime kinetics in a concentration-dependent manner under physiological conditions. The reaction mechanism is validated by computational studies, and the versatility of the reaction is demonstrated by cell-surface labeling experiments. Saline offers an efficient and non-toxic catalytic option for performing the bioorthogonal-coupling reaction of biomolecules at the physiological pH. This saline mediated bioconjugation reaction represents the most biofriendly, mild and versatile approach for conjugating sensitive biomolecules and does not require any extensive purification step.
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| 12. |
- Wang, Shujiang, et al.
(author)
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Saline catalyse oxime reaction at physiological pH : overcoming a major limitation of bioorthogonal reaction
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Journal article (peer-reviewed)abstract
- We have discovered a simple and versatile reaction condition for oxime mediated bioconjugation reaction that could be adapted for both aldehyde and keto substrates. We found that saline accelerated the oxime kinetics in a concentration dependent manner under physiological conditions. The reaction mechanism is validated by computational studies, and the versatility of the reaction is demonstrated by cell-surface labeling experiments. Saline offers an efficient and non-toxic catalytic option for performing the bioorthogonal-coupling reaction of biomolecules at the physiological pH. This saline mediated bioconjugation reaction represents the most bio-friendly, mild and versatile approach for conjugating sensitive biomolecules and does not require any extensive purification step.
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| 13. |
- Yan, Hongji, 1986-, et al.
(author)
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Lithium hyaluronate hydrogels enhance osteogenesis in vitro and ex vivo
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Other publication (pop. science, debate, etc.)abstract
- Lithium is a clinical drug for bipolar disorders and can enhance bone mass, promote osteogenesis of MSCs through inhibiting the Wnt/β-catenin signalling inhibitor GSK 3β. However, the systemic administration of lithium can trigger severe side-effects. Local administration has been attempted in the treatment of bone defects in animal models with positive outcomes. In this study, we explored a pre-manufactured hydrogel system containing the Li ion (Li-gel) in bone applications. Human MSCs cultured in this Li-gel exhibited enhanced osteogenic differentiation. Furthermore, this Li-gel was used to treat chick embryo chorioallantoic membrane (CAM) femur defects and enhanced the bone healing process.
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| 14. |
- Yan, Hongji, et al.
(author)
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Synthetic design of growth factor sequestering extracellular matrix mimetic hydrogel for promoting in vivo bone formation
- 2018
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In: Biomaterials. - : Elsevier. - 0142-9612 .- 1878-5905. ; 161, s. 190-202
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Journal article (peer-reviewed)abstract
- Synthetic scaffolds that possess an intrinsic capability to protect and sequester sensitive growth factors is a primary requisite for developing successful tissue engineering strategies. Growth factors such as recombinant human bone morphogenetic protein-2 (rhBMP-2) is highly susceptible to premature degradation and to provide a meaningful clinical outcome require high doses that can cause serious side effects. We discovered a unique strategy to stabilize and sequester rhBMP-2 by enhancing its molecular interactions with hyaluronic acid (HA), an extracellular matrix (ECM) component. We found that by tuning the initial protonation state of carboxylic acid residues of HA in a covalently crosslinked hydrogel modulate BMP-2 release at physiological pH by minimizing the electrostatic repulsion and maximizing the Van der Waals interactions. At neutral pH, BMP-2 release is primarily governed by Fickian diffusion, whereas at acidic pH both diffusion and electrostatic interactions between HA and BMP-2 become important as confirmed by molecular dynamics simulations. Our results were also validated in an in vivo rat ectopic model with rhBMP-2 loaded hydrogels, which demonstrated superior bone formation with acidic hydrogel as compared to the neutral counterpart. We believe this study provides new insight on growth factor stabilization and highlights the therapeutic potential of engineered matrices for rhBMP-2 delivery and may help to curtail the adverse side effects associated with the high dose of the growth factor.
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| 15. |
- Yan, Hongji, et al.
(author)
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Tuning biomaterial pH for regulating BMP-2 stability and bioactivity in vitro and in vivo
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Other publication (pop. science, debate, etc.)abstract
- The poor affinity of rhBMP-2 to the scaffolds leads to high dose administration requirement resulted in massive side effects has been the hurdle for successful clinic translation for treating delayed unions or remained non-union at bone defect. Optimizing the scaffolds with the purpose of obtaining optimal BMP2 dose and release have been addressed as critical for BMP-2 administration, however, the results are contradictory concerning whether bone formation is more beneficial from burst or controlled release of BMP2. While this might be due to these studies incorporated other bioactive molecules onto scaffolds to immobilize BMP-2. In this study, we report the affinities of rhBMP-2 to the scaffolds can be improved by only tuning the pH of hyaluronic acid (HA) hydrazone crosslinking hydrogel without addition of other molecules. Neo bone induced by BMP-2 showed significantly higher volume with more impact structure and vascularization in pH 4.5 HA hydrogel compared to that in pH7 HA hydrogel. The mechanisms were demonstrated by In vitro BMP-2 release followed by diffusion quantitative calculation and computational simulation methods. Initial burst release of BMP-2 from pH 7 HA hydrogels with the fitting of Fickian behavior while sustained release from pH 4.5 HA hydrogel was observed. Computational stimulation revealed this is due to the protonation state of BMP2 at pH 4.5 resulted in stronger electrostatic interaction with negatively charged groups along the backbone of hyaluronic acid molecules compared to at pH 7. This study gives new direction to scaffolds designing for basic bioactive protein applications in future.
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