Heparin-based hydrogels with tunable sulfation & degradation for anti-inflammatory small molecule delivery

Abstract

Sustained release of anti-inflammatory agents remains challenging for small molecule drugs due to their low molecular weight and hydrophobicity. Therefore, the goal of this study was to control the release of a small molecule anti-inflammatory agent, crystal violet (CV), from hydrogels fabricated with heparin, a highly sulfated glycosaminoglycan capable of binding positively-charged molecules such as CV. In this system, both electrostatic interactions between heparin and CV and hydrogel degradation were tuned simultaneously by varying the level of heparin sulfation and varying the amount of dithiothreitol within hydrogels, respectively. It was found that heparin sulfation significantly affected CV release, whereby more sulfated heparin hydrogels (Hep and Hep−N) released CV with near zero-order release kinetics (R-squared values between 0.96-0.99). Furthermore, CV was released more quickly from fast-degrading hydrogels than slow-degrading hydrogels, providing a method to tune total CV release between 5-15 days while maintaining linear release kinetics. In particular, N-desulfated heparin hydrogels exhibited efficient CV loading (~90% of originally included CV), near zero-order CV release kinetics, and maintenance of CV bioactivity after release, making this hydrogel formulation a promising CV delivery vehicle for a wide range of inflammatory diseases.

Localized SDF-1α Delivery Increases Pro-Healing Bone Marrow-Derived Cells in the Supraspinatus Muscle Following Severe Rotator Cuff Injury

“…By incorporating varying concentrations of DTT within the MP crosslinking network, it is thought that the thioether group established between PEGDA and DTT increases the atomic charge of the carbonyl carbon within the PEGDA molecule, thereby increasing its reactivity with water and ultimately resulting in ester hydrolysis [19,41]. Thus, DTT concentrations of 20-40 mM, all of which were previously shown to be non-toxic in in vitro studies [42], were incorporated within 10 wt% Hep −N MPs and resulted in degradation within 8 to 30 days in vitro (Figure S2).…”

“…Lastly, though heparin and heparin derivatives have been successfully incorporated within bulk hydrogels for SDF-1α delivery [7,10,11,23], we and others have developed heparin-based microparticles (MPs) [18,24–26] as an injectable protein delivery method without exposure to free radicals that are required for in situ radically-polymerized hydrogels [27–29]. Furthermore, building on our previous work [19], we have incorporated dithiothreitol (DTT) within the MPs to vary the rate of hydrolytic degradation [30] and ultimately allow for more complete release of protein over time. In the present study, we have developed SDF-1α loaded 10 wt% Hep −N MPs comprised of Hep −N methacrylamide, poly (ethylene glycol) diacrylate (PEGDA), and DTT and injected them into the supraspinatus muscle immediately following rotator cuff tendon transection and denervation in rats.…”

Biomaterials for protein delivery for complex tissue healing responses

“…62 However, the protein binding properties of GAG-based, electrostatically-driven biomaterials can be tuned by modifying their sulphate content, which changes the electrostatic interactions between the protein and material and subsequently alters protein release from the material. 70,77,[81][82][83] Sulphating non-sulphated molecules such as hyaluronic acid and alginate increases protein retention, while desulphating GAGs such as heparin increases protein release. Sulphation of hyaluronic acid can also slow biomaterial degradation by reducing the availability of octosaccharides necessary for effective degradation by the enzyme hyaluronidase.…”

Recreating Physiological Environments In Vitro: Design Rules for Microfluidic‐Based Vascularized Tissue Constructs

“…GAGs, which are naturally occurring long polysaccharides consisting of repetitive disaccharide units, can be chemically modified to act as a scaffold for vascular network formation . Heparin, which is a negatively charged GAG, can be engineered to support the microvascular network . A PEG‐heparin gel, which was created by the crosslinking of heparin and multiarm PEG, was shown to be able to allow the formation of an interconnected vascular network with the addition of the integrin ligands and growth factors .…”

“…[73] Heparin, which is a negatively charged GAG, can be engineered to support the microvascular network. [74] A PEG-heparin gel, which was created by the crosslinking of heparin and multiarm PEG, was shown to be able to allow the formation of an interconnected vascular network with the addition of the integrin ligands and growth factors. [75] Another nonsulfated GAG, hyaluronic acid (HA), has profound effect on in vivo vascularization and is an interesting antiangiogenic element with partial degradation units of it reported to be angiogenic.…”