title: Synthesis and evaluation of hydrolyzable hyaluronan-tethered bupivacaine delivery systems.
abstract: Local anesthetics are useful for reducing acute pain, but their short duration precludes them from use in solely managing postoperative pain. To prolong the duration of local anesthesia, we conjugated bupivacaine to native hyaluronan (HA) and divinyl sulfone cross-linked Hylan A (Hylan B particles) using a hydrolyzable linker incorporating an imide. Bupivacaine was prepared for conjugation to HA by forming the acryl imide derivative. Separately, the carboxyl group of HA was reacted with nipsylethylamine (NEA) using carbodiimide-mediated coupling to provide HA-NEA that was subsequently reduced with tris(2-carboxyethylphosphine) hydrochloride to yield HA carrying a free sulfhydryl (HA-SH). The HA-bupivacaine conjugate was assembled by reacting HA-SH with acrylbupivacaine. Characterization of the conjugates showed 22% degree of modification by 1 mol of carboxyl. In vitro release studies comparing bupivacaine admixed in HA with bupivacaine conjugated to HA showed half-lives of 0.4 +/- 0.1 h, and 16.9 +/- 0.2 h, respectively, and the bupivacaine was released chemically unaltered as confirmed by LC-MS. In vivo studies to assess the duration of anesthetic activity were performed in a rat sciatic nerve blockade model. For these studies, bupivacaine was conjugated to Hylan B following a similar procedure, and the degree of modification obtained was 14%. Free bupivacaine (3 and 16 mg/kg) and free bupivacaine (3 mg/kg) admixed with Hylan B particles showed nerve block over 4, 9, and 6 h, respectively. Free bupivacaine (3 mg/kg) admixed with bupivacaine (13 mg/kg) conjugated to Hylan B particles showed a four to 5-fold longer impairment of motor function over the free bupivacaine formulations with a total block time of 19 h. Bupivacaine conjugated to Hylan B particles has the potential to prolong the duration of local anesthesia.
authors.affiliation: Biomaterials Science & Engineering, Genzyme Corporation, 500 Kendall Street, Cambridge, Massachusetts 02142, USA.
authors.forename: Diego A
authors.initials: DA
authors.lastname: Gianolio
authors.forename: Michael
authors.initials: M
authors.lastname: Philbrook
authors.forename: Luis Z
authors.initials: LZ
authors.lastname: Avila
authors.forename: Hollace
authors.initials: H
authors.lastname: MacGregor
authors.forename: Su X
authors.initials: SX
authors.lastname: Duan
authors.forename: Richard
authors.initials: R
authors.lastname: Bernasconi
authors.forename: Marina
authors.initials: M
authors.lastname: Slavsky
authors.forename: Sandra
authors.initials: S
authors.lastname: Dethlefsen
authors.forename: Peter K
authors.initials: PK
authors.lastname: Jarrett
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Miller
mesh_terms: D000758:Anesthesia / Q000379:methods; D000818:Animals; D001673:Biodegradation, Environmental; D002045:Bupivacaine / Q000008:administration & dosage* / Q000737:chemistry / Q000493:pharmacokinetics; D003432:Cross-Linking Reagents / Q000737:chemistry; D016503:Drug Delivery Systems / Q000379:methods*; D005260:Female; D006207:Half-Life; D006820:Hyaluronic Acid / Q000737:chemistry*; D006868:Hydrolysis; D009407:Nerve Block / Q000379:methods; D051381:Rats; D017207:Rats, Sprague-Dawley; D012584:Sciatic Nerve / Q000187:drug effects
chemical_list: D003432:Cross-Linking Reagents; D006820:Hyaluronic Acid; D002045:Bupivacaine