title: Nanodiamond-insulin complexes as pH-dependent protein delivery vehicles.
abstract: Enhanced specificity in drug delivery aims to improve upon systemic elution methods by locally concentrating therapeutic agents and reducing negative side effects. Due to their robust physical properties, biocompatibility and drug loading capabilities, nanodiamonds serve as drug delivery platforms that can be applied towards the elution of a broad range of therapeutically-active compounds. In this work, bovine insulin was non-covalently bound to detonated nanodiamonds via physical adsorption in an aqueous solution and demonstrated pH-dependent desorption in alkaline environments of sodium hydroxide. Insulin adsorption to NDs was confirmed by FT-IR spectroscopy and zeta potential measurements, while both adsorption and desorption were visualized with TEM imaging, quantified using protein detection assays and protein function demonstrated by MTT and RT-PCR. NDs combined with insulin at a 4:1 ratio showed 79.8+/-4.3% adsorption and 31.3+/-1.6% desorption in pH-neutral and alkaline solutions, respectively. Additionally, a 5-day desorption assay in NaOH (pH 10.5) and neutral solution resulted in 45.8+/-3.8% and 2.2+/-1.2% desorption, respectively. MTT viability assays and quantitative RT-PCR (expression of Ins1 and Csf3/G-csf genes) reveal bound insulin remains inactive until alkaline-mediated desorption. For applications in sustained drug delivery and therapy we have developed a therapeutic protein-ND complex with demonstrated tunable release and preserved activity.
authors.affiliation: Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA.
authors.forename: Rafael A
authors.initials: RA
authors.lastname: Shimkunas
authors.forename: Erik
authors.initials: E
authors.lastname: Robinson
authors.forename: Robert
authors.initials: R
authors.lastname: Lam
authors.forename: Steven
authors.initials: S
authors.lastname: Lu
authors.forename: Xiaoyang
authors.initials: X
authors.lastname: Xu
authors.forename: Xue-Qing
authors.initials: XQ
authors.lastname: Zhang
authors.forename: Houjin
authors.initials: H
authors.lastname: Huang
authors.forename: Eiji
authors.initials: E
authors.lastname: Osawa
authors.forename: Dean
authors.initials: D
authors.lastname: Ho
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002417:Cattle; D002470:Cell Survival / Q000187:drug effects; D018130:Diamond / Q000737:chemistry*; D004337:Drug Carriers / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007328:Insulin / Q000737:chemistry*; D008422:Materials Testing; D051379:Mice; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D011506:Proteins / Q000008:administration & dosage / Q000737:chemistry*
chemical_list: D004337:Drug Carriers; D007328:Insulin; D011506:Proteins; D018130:Diamond