Selectively crosslinked hyaluronic acid hydrogels for sustained release formulation of erythropoietin

Abstract

A novel sustained release formulation of erythropoietin (EPO) was developed using hyaluronic acid (HA) hydrogels. For the preparation of HA hydrogels, adipic acid dihydrazide grafted HA (HA-ADH) was synthesized and analyzed with (1)H NMR. The degree of HA-ADH modification was about 69%. EPO was in situ encapsulated into HA-ADH hydrogels through a selective cross-linking reaction of bis(sulfosuccinimidyl) suberate (BS(3)) to hydrazide group (pK(a) = 3.0) of HA-ADH rather than to amine group (pK(a) > 9) of EPO. The denaturation of EPO during HA-ADH hydrogel synthesis was drastically reduced with decreasing pH from 7.4 to 4.8. The specific reactivity of BS(3) to hydrazide at pH = 4.8 might be due to its low pK(a) compared with that of amine. In vitro release of EPO in phosphate buffered saline at 37 degrees C showed that EPO was released rapidly for 2 days and then slowly up to 4 days from HA-ADH hydrogels. When the hydrogels were dried at 37 degrees C for a day, however, longer release of EPO up to 3 weeks could be demonstrated. According to in vivo release test of EPO from HA-ADH hydrogels in SD rats, elevated EPO concentration higher than 0.1 ng/mL could be maintained from 7 days up to 18 days depending on the preparation methods of HA-ADH hydrogels. There was no adverse effect during and after HA-ADH hydrogel implantation.

Synthesis and degradation test of hyaluronic acid hydrogels

“…The hydration rates of various hydrogels were analyzed by measuring their swelling ratios during the in vitro tests as published in our previous reports [9][10][11]. The swelling ratios were in the range of 2.5-3.0 times of their original volumes regardless of the crosslinking chemistry of three HA hydrogels.…”

“…HA has unique viscoelastic properties for the lubrication function of the synovial joint fluid and vitreous humor in the eye [4]. Because of its various functions and physicochemical properties, HA and modified HA have been extensively investigated and used for the treatment of arthritis [5], ophthalmic surgery [6], drug delivery [7][8][9][10][11], and tissue engineering [12,13].…”

“…A number of strategies for the modification of HA through carboxyl and hydroxyl groups have been developed [8][9][10][11][12]. Chemical modification of HA provides tools for its application as a biomaterial in medicine.…”

Guided bone regeneration by poly(lactic-co-glycolic acid) grafted hyaluronic acid bi-layer films for periodontal barrier applications

“…On the other hand, low molecular weight amorphous PLGA is found to be useful for controlled drug delivery applications [15]. Recently, hyaluronic acid (HA) and modified HA have been used for various medical applications such as drug delivery and tissue engineering [16][17][18][19][20][21]. As a natural linear polysaccharide, HA is biodegradable, biocompatible and non-immunogenic [22].…”

Amelioration of Anemia in the ICGN Mouse, a Renal Anemia Model, with a Subcutaneous Bolus Injection of Erythropoietin Adsorbed to Hydroxyapatite Matrix

“…For naturally occurring-polymerbased carriers, such as hyaluronic acid and gelatin, the sustained release of rhEPO have been studied. Based on their network structure of polymer crosslinkings, hyaluronic acid hydrogels have shown the sustained release of rhEPO for 7 days in vivo [9,23]. Gelatin-based sheets, which are applicable to the new treatments for ischemic cardiomyopathy, released rhEPO for 4 weeks [16].…”