title: Providing sustained transgene induction through affinity-based drug delivery.
abstract: Small molecule drug activators of gene expression have been used in applications ranging from gene therapy, to tissue engineering and regenerative medicine. One concern is that for sustained gene expression, a long-term, controlled delivery system is needed. Insoluble polymers containing a high proportion of cyclodextrin (CD) affinity groups have been shown to prolong drug delivery far beyond that capable of polymers relying on diffusion alone. In this study we evaluate the capacity of such polymers to deliver the transgene inducer doxycycline. Our results show that initial drug loading is proportional to affinity, with ∼8% loading in high-affinity γ-CD polymers; ∼7% loading in moderate-affinity β-CD polymers; and only ∼4.5% loading in the non-affinity control polymer made from linear dextran. When release aliquots from these polymers were incubated with cells genetically modified for inducible transgene expression we observed activation of transgene expression for up to three weeks from samples released by affinity-based polymers. We showed that drug stability is maintained over the course of the study using a bacterial zone of inhibition assay where again affinity-based polymers show sustained availability of drug, weeks longer than non-affinity controls. Lastly we provide theoretical calculations of strength of binding interactions between cyclodextrins and many additional transgene inducers demonstrating the broad utility of this delivery platform.
authors.affiliation: Department of Biomedical Engineering, Case Western Reserve University Cleveland, Ohio.
authors.forename: Edgardo
authors.initials: E
authors.lastname: Rivera-Delgado
authors.affiliation: Department of Biomedical Engineering, Case Western Reserve University Cleveland, Ohio.
authors.forename: Emily
authors.initials: E
authors.lastname: Ward
authors.affiliation: Department of Biomedical Engineering, Case Western Reserve University Cleveland, Ohio.
authors.forename: Horst A
authors.initials: HA
authors.lastname: von Recum
mesh_terms: D003692:Delayed-Action Preparations / Q000737:chemistry*; D003911:Dextrans / Q000737:chemistry; D004318:Doxycycline / Q000008:administration & dosage* / Q000494:pharmacology; D016503:Drug Delivery Systems; D015870:Gene Expression / Q000187:drug effects*; D049452:Green Fluorescent Proteins / Q000235:genetics; D006801:Humans; D061986:MCF-7 Cells; D008958:Models, Molecular; D019076:Transgenes / Q000187:drug effects*; D047392:beta-Cyclodextrins / Q000737:chemistry*; D047408:gamma-Cyclodextrins / Q000737:chemistry*
chemical_list: D003692:Delayed-Action Preparations; D003911:Dextrans; D047392:beta-Cyclodextrins; D047408:gamma-Cyclodextrins; D049452:Green Fluorescent Proteins; C031215:betadex; C023792:gamma-cyclodextrin; D004318:Doxycycline
keywords: affinity; cyclodextrin; drug delivery; inducible promoter; transgene