Abstract
PEG5kDa‐cholane, PEG10kDa‐cholane and PEG20kDa‐cholane self‐assembling polymers have been synthesised by the end-functionalisation of 5, 10 and 20kDa linear amino‐terminating monomethoxy‐poly(ethylene glycol) (PEG‐NH2) with 5β‐cholanic acid. Spectroscopic studies and isothermal titration calorimetry showed that the CMC of the PEG‐cholane derivatives increased from 23.5±1.8 to 60.2±2.4μM as the PEG molecular weight increased. Similarly, light scattering analysis showed that the micelle size increased from 15.8±4.9 to 23.2±11.1nm with the PEG molecular weight. Gel permeation studies showed that the polymer bioconjugates associate with recombinant human granulocyte colony stimulating factor (rh‐G‐CSF) to form supramolecular nanocomposites according to multi‐modal association profiles. The protein loadings obtained with PEG5kDa‐cholane, PEG10kDa‐cholane and PEG20kDa‐cholane were 7.4±1.1, 2.7±0.3 and 2.1±0.4% (protein/polymer, w/w %), respectively. Scatchard and Klotz analyses showed that the protein/polymer affinity constant increased and that the number of PEG‐cholane molecules associated to rh‐G‐CSF decreased as the PEG molecular weight increased. Isothermal titration calorimetry confirmed the protein/polymer multi‐modal association. Circular dichroism analyses showed that the polymer association alters the secondary structure of the protein. Nevertheless, in vitro studies performed with NFS‐60 cells showed that the polymer interaction does not impair the biological activity of the cytokine. In vivo studies performed by intravenous and subcutaneous administrations of rh‐G‐CSF to rats showed that the association with PEG5kDa‐cholane prolongs the body exposure of the protein. After subcutaneous administration, the protein tmax values obtained with rh‐G‐CSF and 1:14 and 1:21 rh‐G‐CSF/PEG5kDa‐cholane (w/w ratio) nanocomplexes were 2, 8 and 24h, respectively. The 1:21 (w/w) rh‐G‐CSF/PEG5kDa‐cholane formulation resulted in 149% relative bioavailability, and the pharmacokinetic behaviour was similar to that obtained with an equivalent protein dose of rh‐G‐CSF chemically conjugated with one linear 20‐kDa PEG. A single administration of a 1.5mg/kg dose of a 1:21 (w/w) rh‐G‐CSF/PEG5kDa‐cholane formulation induced a high production of white blood cells for 96h.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
