title: Investigating thiol-modification on hyaluronan via carbodiimide chemistry using response surface methodology.
abstract: Hyaluronan (HA) is a naturally occurring glycosaminoglycan widely researched for its use as a biomaterial in tissue engineering, drug delivery, angiogenesis, and ophthalmic surgeries. The mechanical properties of this biomaterial can be altered to a required extent by chemically modifying the pendant reactive groups. However, derivatizing these polymers to a predetermined extent has been the Achilles heel for this process. In this study, we have investigated the factors controlling the derivatization of the carboxyl moieties of HA with amine containing thiol, cystamine dihydrochloride (Cys), via carbodiimide crosslinking chemistry. We used fractional factorial design to screen and identify the significant factor(s) affecting the reaction, and response surface methodology (RSM) to develop a model equation for predicting the degree of thiolation of HA. Also, we analyzed the reaction mechanism for potential side reactions. We observed that N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC) (mole ratio with repeat unit of HA) is the significant factor controlling the degree of amidation. The quadratic equations developed from RSM predict the formulation for a desired degree of amidation of HA and percentage of potential side product. Hence, derivatizing HA to a predetermined extent with minimal side product can be achieved using the statistical design of experiments.
authors.affiliation: Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, Saint Louis, Missouri.
authors.forename: Sruthi
authors.initials: S
authors.lastname: Santhanam
authors.affiliation: Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, Saint Louis, Missouri.
authors.forename: Jue
authors.initials: J
authors.lastname: Liang
authors.affiliation: Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, Saint Louis, Missouri.
authors.forename: Rinku
authors.initials: R
authors.lastname: Baid
authors.affiliation: Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, Saint Louis, Missouri.|Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, Saint Louis, Missouri.|Department of Research, Veterans Affairs Healthcare System, Saint Louis, Missouri.
authors.forename: Nathan
authors.initials: N
authors.lastname: Ravi
mesh_terms: D000577:Amides / Q000737:chemistry; D002234:Carbodiimides / Q000737:chemistry*; D006820:Hyaluronic Acid / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D000577:Amides; D002234:Carbodiimides; D013438:Sulfhydryl Compounds; D006820:Hyaluronic Acid
keywords: carbodiimide crosslinking; hyaluronan; response surface methodology; side reaction; thiol