Role of a novel excipient poly(ethylene glycol)-b-poly(L-histidine) in retention of physical stability of insulin in aqueous solutions.
OBJECTIVE
This study is to investigate whether poly(ethylene glycol) (PEG)-b-poly(L-histidine) [PEG-polyHis] can reduce aggregation of insulin in aqueous solutions on agitation by forming ionic complexes.


METHODS
Insulin aggregation on agitation was monitored spectrophotometrically and by fibrillation studies with a dye Thioflavin T. Pluronic F-127 as a control and PEG-polyHis as a novel multifunctional excipient were added to prevent destabilization of insulin. Conformation of insulin was evaluated in a circular dichroism (CD) study.


RESULTS
Ionic interactions between insulin and PEG-polyHis were induced in the pH range: 5.5-6.5. pH 5.5 was selected for further evaluation based on particle size/zeta potential studies. Ionic complexation with PEG-polyHis is more effective at pH 5.5 in stabilizing insulin (75% of insulin retained versus 0% with no excipient) than Pluronic F-127 (42% retained). PEG-polyHis guards against insulin aggregation in non-complexing pH conditions (pH 7.4), 64% insulin retained versus 58% with F-127 and 0% with no excipient) pointing to the potential role played by PEG in modulation of insulin surface adsorption. Rate of fibrillation was higher for plain insulin compared with addition of PEG-polyHis and Pluronic F-127 at both pH.


CONCLUSIONS
Understanding and manipulation of such polyelectrolyte-protein complexation will likely play a role in protein stabilization.
Taluja
Ajay
A
Department of Pharmaceutics & Pharmaceutical Chemistry, University of Utah, Salt Lake City, Utah, USA.
Bae
You Han
YH
D000817:Anilino Naphthalenesulfonates / Q000737:chemistry; D052160:Benzothiazoles; D002942:Circular Dichroism; D004355:Drug Stability; D005079:Excipients / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D007328:Insulin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D010316:Particle Size; D011092:Polyethylene Glycols / Q000737:chemistry*; D011095:Polyethylenes / Q000737:chemistry; D011126:Polypropylenes / Q000737:chemistry; D011485:Protein Binding; D011489:Protein Denaturation; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry*; D011863:Radioimmunoassay; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012995:Solubility; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D013844:Thiazoles / Q000737:chemistry
D000817:Anilino Naphthalenesulfonates; D052160:Benzothiazoles; D005079:Excipients; D005456:Fluorescent Dyes; D007328:Insulin; D011095:Polyethylenes; D011126:Polypropylenes; D011506:Proteins; D011994:Recombinant Proteins; D013844:Thiazoles; C480317:polyhistidine-block-polyethylene glycol; C009462:thioflavin T; D011092:Polyethylene Glycols; C078661:UCON 50-HB-5100