title: A novel soluble supramolecular system for sustained rh-GH delivery.
abstract: Methoxy-poly(ethylene glycol)s bearing a terminal cholanic moiety (mPEG(5kDa)-cholane, mPEG(10kDa)-cholane and mPEG(20kDa)-cholane) were physically combined with recombinant human growth hormone (rh-GH) to obtain supramolecular assemblies for sustained hormone delivery. The association constants (Ka) calculated by Scatchard analysis of size exclusion chromatography (SEC) data were in the order of 10(5)M(-1). The complete rh-GH association with mPEG(5kDa)-cholane, mPEG(10kDa)-cholane and mPEG(20kDa)-cholane was achieved with 7.5 ± 1.1, 3.9 ± 0.4 and 2.6 ± 0.4 w/w% rh-GH/mPEG-cholane, respectively. Isothermal titration calorimetry (ITC) yielded association constants similar to that calculated by SEC and showed that rh-GH has 21-25 binding sites for mPEG-cholane, regardless the polymer molecular weight. Dialysis studies showed that the mPEG-cholane association strongly delays the protein release; 80-90% of the associated rh-GH was released in 200 h. However, during the first 8h the protein formulations obtained with mPEG(10kDa)-cholane and mPEG(20kDa)-cholane showed a burst release of 8 and 28%, respectively. Circular dichroism (CD) analyses showed that the mPEG(5kDa)-cholane association does not alter the secondary structure of the protein. Furthermore, mPEG(5kDa)-cholane was found to enhance both the enzymatic and physical stability of rh-GH. In vivo pharmacokinetic and pharmacodynamic studies were performed by subcutaneous administration of rh-GH and rh-GH/mPEG(5kDa)-cholane to normal and hypophysectomised rats. The study showed that mPEG(5kDa)-cholane decreases the maximal concentration in the blood but prolongs the body exposure of the protein, which resulted in 55% bioavailability increase. Finally, rh-GH formulated with mPEG(5kDa)-cholane yielded prolonged weight increase of hypophysectomised rats as compared to rh-GH in buffer or formulated with mPEG(5kDa)-OH. After the second administration the weight of the animals treated with rh-GH formulated with mPEG(5kDa)-cholane was about 2 times higher than that obtained with equal dose of non-formulated rh-GH.
authors.affiliation: Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Via F. Marzolo 5, 35131 Padova, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Salmaso
authors.affiliation: Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Via F. Marzolo 5, 35131 Padova, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Bersani
authors.affiliation: Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Via F. Marzolo 5, 35131 Padova, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Scomparin
authors.affiliation: Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Via F. Marzolo 5, 35131 Padova, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Balasso
authors.affiliation: Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Via F. Marzolo 5, 35131 Padova, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Brazzale
authors.affiliation: Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Via F. Marzolo 5, 35131 Padova, Italy.
authors.forename: Michela
authors.initials: M
authors.lastname: Barattin
authors.affiliation: Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Via F. Marzolo 5, 35131 Padova, Italy. Electronic address: paolo.caliceti@unipd.it.
authors.forename: Paolo
authors.initials: P
authors.lastname: Caliceti
mesh_terms: D000818:Animals; D019540:Area Under Curve; D001682:Biological Availability; D002757:Cholanes / Q000737:chemistry; D003692:Delayed-Action Preparations; D016503:Drug Delivery Systems; D004355:Drug Stability; D005260:Female; D013006:Growth Hormone / Q000008:administration & dosage* / Q000493:pharmacokinetics; D006801:Humans; D007016:Hypophysectomy; D008297:Male; D008958:Models, Molecular; D011092:Polyethylene Glycols / Q000737:chemistry; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000008:administration & dosage; D012212:Rheology
chemical_list: D002757:Cholanes; D003692:Delayed-Action Preparations; D011994:Recombinant Proteins; D011092:Polyethylene Glycols; D013006:Growth Hormone
keywords: Amphiphilic polymers; Growth hormone; Poly(ethylene glycol); Protein/polymer association; Sustained protein delivery; rh-GH